Workability and Flexural Strength of Binary Blended Concrete made with Recycled Aggregates and Marble Dust under Two-Point Loading

Workability and Flexural Strength of Binary Blended Concrete made with Recycled Aggregates and Marble Dust under Two-Point Loading | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Workability and Flexural Strength of Binary Blended Concrete made with Recycled Aggregates and Marble Dust under Two-Point Loading Shuban Ali, Wazir Ali Brohi, Bashir Ahmed Memon, Gulzar Hussain, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7383472/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 19 You are reading this latest preprint version Abstract The increasing demand for sustainable construction materials has increased interest in utilizing industrial waste products in concrete production. This research explores the combined effect of recycled coarse aggregates (RCA), obtained from demolished concrete, and marble dust (MD), a byproduct of marble processing, on workability and flexural strength of concrete. Both materials are widely available construction wastes that pose significant disposal challenges. In this study, RCA was used to replace 50% of conventional coarse aggregates, while marble dust replaced cement in varying proportions from 1–10%, at 1% intervals. A total of twelve concrete mixes were prepared using a standard 1:2:4 mix ratio and a constant water-binder ratio of 0.55. Among these, ten mixes contained both RCA and MD, one served as a control mix with all conventional aggregates and no MD, and one contained RCA but no MD. Workability was evaluated using the slump test, and flexural strength was assessed using standard prisms (100 mm × 100 mm × 500 mm) tested under two-point loading after 28 days of curing. The results revealed a clear trend of decreasing slump values with increasing marble dust content, indicating reduced workability due to higher water demand. Flexural strength generally declined with higher MD content, but the mix with 7% MD and 50% RCA achieved a balanced performance, exhibiting only a 15% reduction in strength compared to the control mix, while improving central deflection by 11%. These findings demonstrate that a binary blend of RCA and MD can yield eco-efficient concrete with acceptable structural performance, supporting broader adoption of waste materials in construction. The results also highlight the importance of optimized blending ratios to balance strength, ductility, and workability in sustainable concrete applications. Demolished waste marble dust workability flexural strength two-point loading sustainable development Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 1. Introduction Recycled aggregates, particularly those derived from demolished concrete waste, have emerged as a necessary and environmentally conscious alternative to natural aggregates. Their usage not only helps conserve natural aggregate reserves but also reduces environmental burdens associated with aggregate mining and waste disposal. Substantial time and effort have been devoted by the research community to understanding their production and behavior in concrete. However, several influencing factors—such as the presence of adhered mortar on old aggregates, the age and condition of the original structure, its exposure during service life, and the specific processing methods used—alter the properties of recycled aggregates. Consequently, concrete made with recycled aggregates behaves differently from conventional concrete, both in its fresh and hardened states. These deviations must be carefully addressed before recycled aggregates are utilized in structural applications. The concept of using recycled aggregates in concrete is not new; it dates to the late 1940s, when post-war reconstruction efforts created an urgent need to manage large volumes of demolition waste. On-site reuse of these materials as coarse aggregates not only alleviated waste management challenges but also preserved natural resources. However, several practical concerns persist, and many practitioners remain hesitant due to inconsistent performance data and the absence of standardized regulatory frameworks. [ 1 ] Comprehensive efforts have been made by the research community to understand recycled aggregate behavior in concrete. [ 2 ], along with others [ 3 , 4 ], reviewed the mechanical properties and durability of recycled aggregate concrete (RAC), highlighting challenges and proposing strategies for wider implementation. [ 5 ] studied \(\:{M}_{30}\) Concrete with 100% RCA and recorded reductions in compressive, tensile, and cohesive strength by 16.1%, 20.1%, and 18.1%, respectively, compared to conventional concrete. Conversely, Motlagh [ 6 ] Reported compressive strengths up to 7200 psi (49.65 MPa) using 100% recycled aggregates, emphasizing the variability due to source and processing quality. Jagan and Neelakantan [ 7 ] Evaluated different mixing approaches—two-stage, mortar mixing, enveloped mixing, and double mixing—and found that the mortar mixing method delivered superior performance. Enhancements in RAC properties have also been pursued through the addition of supplementary materials. The inclusion of 0.5% carbon fibers and 8% silica fume in concrete containing 50% RCA led to a 20% increase in both tensile and flexural strengths [ 8 ]. Various dosages of steel fiber have also been explored. In this regard, researchers in [ 9 ] observed substantial improvements in overall mechanical properties with 1% steel fiber content. [ 10 ] Extended this investigation, testing steel fiber content ranging from 1–5% in 0.5% increments. They recorded up to 69% improvement in flexural strength, with expectations of further enhancement at higher fiber volumes. [ 11 ] Examined high-strength RAC with 25%, 50%, 75%, and 100% RCA and found consistent reductions across all strength metrics. Similarly, Nandhini et al. [ 12 ] observed lower flexural strength and greater deflection in concrete with 100% RCA, although the observed flexural mode of failure was considered a positive outcome. In addition to experimental research, numerical and statistical models have been used to predict RAC properties. [ 13 ] Used 100% RCA and developed a regression model based on geometric and steel properties, yielding a high R² value of 0.997. [ 14 ] Employed numerical modeling using 302 datasets to predict flexural strength with strong accuracy. Other additives, such as metakaolin, have also been incorporated into RAC to improve performance. [ 15 ] Found that 20% metakaolin content allowed compressive strength levels comparable to conventional concrete. [ 16 ] Also observed this percentage as optimal, noting improvements in all strength parameters and modulus of elasticity. Their work also introduced predictive models for broader parameter estimation. Demolition waste is not the only source of concern; primary industrial processes such as marble quarrying also produce substantial amounts of waste in the form of dust and slurry. With growing construction activity, the marble industry has seen a parallel increase in waste output. This waste, typically discarded with minimal treatment, presents both environmental and logistical challenges due to limited landfill space. Marble waste can be processed into fine marble powder through drying and grinding. This powder, which possesses cementitious properties, shows potential as a partial cement replacement in concrete. [ 17 , 18 ]. Several researchers have reviewed its performance in cement replacement applications, highlighting strength enhancement and reductions in CO₂ emissions during cement production. [ 19 – 21 ]. Vashist and Naval [ 22 ] A 3% increase in 7-day compressive strength was reported, and 2% was reported at 28 days using 5% MD and 15% RCA. Similarly, Memon et al. [ 23 ] An 8.3% increase in compressive strength was found using the same dosage of MD as cement replacement. Ahmed et al. [ 24 ] Developed numerical models to predict tensile and flexural strength of RAC with MD, and the results closely matched experimental data. Hashmi et al. [ 25 ] Also applied modeling techniques to forecast strength parameters with a 5% prediction error. Another study [ 26 ] Utilized Gaussian process regression, support vector machines, and ANFIS modeling using 202 datasets, with Gaussian process yielding the most accurate predictions. Basaran et al. [ 27 ] Used marble waste as both fine and coarse aggregates and identified 50% as the optimum replacement level. Karalar et al. [ 28 ] Studied the flexural behavior of reinforced concrete beams with MD dosages up to 40%, concluding that a 10% replacement was optimal for strength improvements in beams with balanced steel ratios. Meena et al. [ 29 ] observed a 13.5% increase in compressive strength at 7.5% MD replacement, while Dhanalakshmi and Hameed [ 30 ] Reported a 54.5% increase at a 10% replacement level. Overall, extensive research has addressed the use of both recycled aggregates and marble dust in conventional concrete. Their combined use has also been explored to some extent, with promising results. However, there is a clear lack of consistency in reported findings, which continues to limit confidence in widespread implementation. Rigorous material testing remains essential for ensuring reliable mechanical behavior. Among mechanical tests, flexural strength assessment is especially important for understanding bending behavior in concrete elements. Although central-point loading is commonly used, it does not accurately reflect real structural conditions. Two-point loading is more representative of actual service loading and offers better insights into performance. Therefore, the present study aims to evaluate the combined effect of recycled aggregates from demolished concrete and marble dust as cement replacement on the flexural strength of concrete under two-point loading. The objective is to determine optimal replacement levels that maintain acceptable strength and deflection performance while supporting sustainable material use. The findings are expected to enhance understanding of blended waste concrete behavior and serve as a reference for future research and structural design guidelines. 2. Materials and testing The conventional ingredients used in this study included ordinary Portland cement, hill sand (fine aggregates), crushed stone (coarse aggregates), and potable water. The ordinary Portland cement (Lucky Star brand) exhibited a fineness of 96% on the #100 sieve. The initial and final setting times were recorded as 64 and 370 minutes, respectively, with a standard consistency of 31%. These values indicate compliance with the requirements of ASTM C150/C150M. [ 31 ]. The fine aggregates (hill sand) were tested for essential properties such as water absorption (1.04%), specific gravity (2.52), loss on ignition (2.31%), and fineness modulus (2.86). Sieve analysis was conducted by ASTM C136/C136M. [ 32 ] To determine the gradation of the material. The particle size distribution, including comparisons with the ASTM-defined minimum and maximum limits, is shown in Fig. 1 . The results confirm that the fine aggregates meet the standard grading criteria. The coarse aggregates (crushed stone) were also evaluated for key physical characteristics. Water absorption, specific gravity, abrasion resistance, and fineness modules were measured as 1.5%, 2.5%, 12.6%, and 4.5%, respectively. A Sieve analysis was again conducted according to ASTM C136/C136M. The grading curves for both conventional and recycled coarse aggregates are presented in Fig. 2, along with the ASTM-defined boundaries. Both aggregate types were observed to fall within the acceptable limit defined by the standard. 2.1. Recycled aggregates To obtain recycled coarse aggregates, large concrete blocks sourced from the demolition of a reinforced concrete residential unit were manually broken down using hammers. The maximum aggregate size was limited to 25 mm to ensure consistency with standard gradation requirements. After crushing, the aggregates were thoroughly washed to remove dust and contaminants and manually sorted to eliminate unwanted materials such as wood, plastics, and metal fragments. The processed aggregates were then dried in the laboratory for 24 hours before testing. The basic physical properties of the recycled aggregates were subsequently evaluated. The water absorption, specific gravity, abrasion resistance, and fineness modulus were recorded as 4.0%, 2.27, 23.15%, and 4.48, respectively. The fineness modulus was computed using sieve analysis results, conducted by ASTM C136/C136M. These values fall within acceptable limits for coarse aggregates as defined by relevant ASTM standards. The gradation curve for the recycled aggregates, along with ASTM-specified minimum and maximum boundaries, is presented in Fig. 2 . Potable water was used throughout the experimental program for washing, mixing, and curing purposes. The water had a pH value of 6.9, confirming its suitability for concrete applications by ASTM C1602. 2.2. Marble Dust Marble dust is a byproduct generated during both the quarrying of marble blocks and the cutting of these blocks into tiles of desired dimensions. These processes not only produce significant quantities of fine dust and slurry but also contribute to carbon dioxide emissions due to the operation of heavy machinery. During cutting, water is used extensively, resulting in the formation of wet slurry, which eventually dries into hardened boulders. These waste forms—dust, slurry, and hardened residue—pose environmental and aesthetic concerns and require proper disposal to prevent negative impacts on the surrounding area and its inhabitants. Similar to construction and demolition waste, marble waste is commonly dumped in landfills. However, due to limited landfill availability and increasing urbanization, the disposal of marble waste has become a pressing issue in many parts of the world. Previous research has shown that marble dust exhibits pozzolanic and filler-like properties, making it a viable partial replacement for cement. Its use not only reduces the demand for cement production, thereby lowering associated CO₂ emissions, but also helps mitigate the challenges of marble waste management. In this study, marble dust was utilized as a partial cement replacement. The material was sourced from local marble cutting workshops and subsequently ground to a fine powder. To ensure its compatibility with cementitious materials, the powder was sieved using a #100 sieve. The fineness of the marble dust was recorded at 94.7%, which is comparable to the 96% fineness of the ordinary Portland cement used in the study. A visual representation of the marble dust material is provided in Fig. 3 . 2.3. Mix proportion and slump test For the preparation of concrete samples, a 1:2:4 mix ratio was selected, as it is a commonly used standard mix in the construction industry. Both conventional and recycled aggregates were used in equal proportions, according to the recommendations of previous studies [ 33 , 34 ] and [ 35 ], which suggests that this ratio minimizes strength loss when incorporating recycled aggregates. Marble dust was used as a partial cement replacement at replacement levels ranging from 1–10%, in 1% increments. This resulted in ten experimental mixes (labeled MD1 to MD10). Additionally, one control mix was prepared without marble dust, bringing the total number of mixes used in the study to eleven. For all mixes, a constant water-to-binder (w/b) ratio of 0.55 was adopted to account for the higher water demand associated with recycled aggregates. The workability of each concrete mix was evaluated using the slump cone test, conducted by ASTM C143. [ 36 ]. The concrete ingredients were thoroughly mixed in a rotating drum mixer. The slump cone was filled in three layers, with each layer being compacted using twenty-five strokes of a tamping rod. After leveling the top surface, the cone was carefully lifted in the standard manner, and the vertical settlement (slump) of the concrete was measured immediately. A photograph showing one of the mixes during slump testing is provided in Fig. 4, and the results of all mixes are summarized in Table 1 . Table 1 Slump values # Mix Cement (Kg) Marble dust (Kg) FA (Kg) CA (Kg) RA (Kg) Slump value (mm) % deviation with CC 1 CC 4.75 0 10.56 19.8 0 81 -- 2 MD1 4.70 0.047 10.56 9.9 9.9 70 -13.58 3 MD2 4.65 0.095 10.56 9.9 9.9 66 -18.52 4 MD3 4.60 0.142 10.56 9.9 9.9 62 -23.46 5 MD4 4.56 0.19 10.56 9.9 9.9 59 -27.16 6 MD5 4.51 0.23 10.56 9.9 9.9 53 -34.57 7 MD6 4.46 0.28 10.56 9.9 9.9 48 -40.74 8 MD7 4.41 0.33 10.56 9.9 9.9 42 -48.15 9 MD8 4.37 0.38 10.56 9.9 9.9 31 -61.73 10 MD9 4.32 0.42 10.56 9.9 9.9 20 -75.31 11 MD10 4.27 0.47 10.56 9.9 9.9 9 -88.89 2.4. Sample preparation and curing For the experimental program described in this study, concrete prism specimens with dimensions of 500 mm 100 mm 100 mm × 100 mm were prepared. Standard steel molds were used, cleaned, and oiled before casting. For each mix batch, three prism specimens were cast, resulting in a total of 36 specimens across all batches. The quantities of concrete ingredients used to produce three specimens per batch are summarized in Table 1 , corresponding to approximately 0.015 m³ of concrete per mix. Concrete was mixed in a mechanical drum mixer until a uniform consistency was achieved. The fresh concrete was then placed into the molds in layers and compacted using a table vibrator to ensure proper consolidation and eliminate entrapped air. The filled molds were left undisturbed for 24 hours to allow initial setting. After this period, the specimens were demolded and air-dried at room temperature for one day (Fig. 5 ). Following the initial drying phase, all specimens were fully immersed in potable water and cured for 28 days under standard laboratory conditions to ensure proper hydration (Fig. 6). Curing was performed at a controlled temperature of 20 ± 2°C and relative humidity above 95%, as per ASTM C192/C192M 3. Specimen testing After completing the 28-day curing period, the concrete prism specimens were removed from the water tank, their surfaces gently wiped with a clean cloth and allowed to dry air at ambient laboratory conditions for 24 hours. The specimens were tested under a two-point loading configuration, as illustrated in Fig. 7 . Flexural testing was conducted using a universal testing machine (UTM), where the load was applied symmetrically at the third points of the specimen span to create a constant moment region between the loading points. The load gradually increased at a controlled rate of 0.5 kN/sec until complete failure of the specimen occurred. A representative image of a specimen under loading is shown in Fig. 8. During testing, the maximum applied load and the corresponding central deflection were recorded for each specimen. The flexural strength was then calculated using the failure load and specimen dimensions, based on the standard equation for third-point loading. [ 37 ] The computed flexural strength and central point deflection values for each specimen in all batches are summarized in Table 2 . These results serve as the basis for evaluating the influence of recycled aggregates and marble dust on the flexural performance of concrete. Table 2 Flexural strength and maximum deflection # Mix Load (kN) Deflection (mm) Flexural Strength (MPa) 1 2 3 1 2 3 1 2 3 1 CC 7.57 7.52 8.14 4.8 4.5 5.6 5.67 5.64 6.10 2 MD1 7.96 7.92 7.19 5.2 4.9 6.1 5.97 5.94 5.39 3 MD2 7.74 7.65 5.74 5.7 6.5 4.7 5.80 5.73 4.30 4 MD3 6.39 6.94 6.13 4.5 4.7 4.5 4.79 5.20 4.59 5 MD4 6.86 5.90 6.62 4.5 4.7 4.4 5.14 4.42 4.96 6 MD5 5.82 6.88 6.96 4.8 4.5 4.3 4.36 5.16 5.22 7 MD6 6.90 5.82 8.99 4.5 4.9 4.5 5.17 4.36 4.49 8 MD7 6.51 6.87 6.37 4.2 4.3 4.8 4.88 5.15 4.77 9 MD8 6.49 6.87 5.91 4.2 4.7 4.5 4.86 5.15 4.43 10 MD9 6.48 5.23 5.64 4.1 5.5 4.5 4.86 3.92 4.23 11 MD10 6.00 4.46 4.86 5.7 4.5 5.1 4.50 3.34 3.64 4. Results and discussion The obtained results demonstrate the variation in basic properties between recycled and conventional aggregates, which is consistent with findings reported in the literature. The inferior performance of recycled aggregates is primarily attributed to the presence of adhered mortar, the age and previous service conditions of the source concrete, and the heterogeneous nature of the material. The porous structure of the attached mortar significantly increases water demand. Specifically, the water absorption of recycled aggregates was recorded to be 166% higher than that of conventional aggregates. Additionally, a 9% reduction in specific gravity and an 84% increase in abrasion loss were observed, further highlighting the impact of the residual mortar and previous use. The fineness modulus of recycled aggregates remained relatively like that of conventional aggregates, indicating comparable particle size distribution. These deviations in physical properties must be carefully considered during mix design to avoid issues in both the fresh and hardened states of concrete. In the current study, adjustments were made to the mix design to accommodate the higher water demand of recycled aggregates. The physical properties of fine aggregates, cement, and water were also evaluated earlier and found to be within the allowable limits specified in the relevant ASTM standards. The workability of the concrete mixes was assessed using the slump cone test, with results previously listed and graphically presented in Fig. 9 . The results indicate that the incorporation of marble dust as a partial cement replacement significantly reduced workability. As the marble dust content increased, a consistent decrease in slump values was observed. The reduction in slump ranged from 14–89%, with the maximum loss occurring at the highest replacement level. This trend suggests that marble dust increases the water demand of the mix, likely due to its fine particle size and higher surface area. In addition, the marble dust acts as a filler material, occupying voids between fine and coarse aggregates, which restricts fluidity and contributes to the observed decrease in slump. To maintain desired workability levels, adjustments in mixed design, such as water content modification or the use of superplasticizers, may be necessary when incorporating higher percentages of marble dust. The flexural strength values, computed from the recorded failure loads in the previous section, are compared with those of the control mix (conventional concrete) in Fig. 10. Like the slump results, flexural strength was affected by the incorporation of both recycled aggregates and marble dust, with the effect becoming more prominent as the dosage of marble dust increased. The reduction in flexural strength ranged from 0.63–34% across the tested mixes. At 1% marble dust replacement, the strength reduction was less than 1%, which can be considered negligible. However, at 2%, a more noticeable loss of 9% was recorded. Between 1% and 6%, the strength results exhibited some fluctuation, which may be attributed to variations in workmanship and the incomplete pozzolanic reaction of the marble dust at lower replacement levels. At 7% marble dust replacement, a strength reduction of approximately 15% was observed. Beyond this level, the reduction in flexural strength continued to increase steadily with higher marble dust content. The observed decline is likely due to the dilution effect of replacing cement with a non-reactive or slowly reacting filler, which limits the development of hydration products responsible for strength. Interestingly, the strength loss commonly associated with the use of recycled aggregates appears to be partially offset by the addition of marble dust. In particular, the 1% marble dust replacement yielded a flexural strength nearly equivalent to that of conventional concrete, suggesting a beneficial synergy. From a sustainability perspective, the 7% replacement of cement with marble dust may be treated as optimum with a loss of strength equal to 15%, offering a balance between strength performance and environmental benefits. At this dosage, the strength reduction remains within acceptable limits for structural applications, provided appropriate considerations are made during structural design to ensure durability and serviceability. The recorded central deflection values for all prism specimens during testing were previously presented. The average deflection values for each batch are compared with those of the control concrete (without marble dust) in Fig. 11 . It can be observed that the first two mixes, containing 1% and 2% marble dust, exhibited higher deflection than the conventional concrete, indicating increased deformation capacity. However, from 3–9% replacement, a gradual reduction in deflection was recorded. Interestingly, at 10% marble dust replacement, the deflection again increased beyond that of the control mix. This trend suggests that marble dust, when used at moderate levels, improves the compactness and bonding within the concrete matrix. Its fine particle size helps fill voids and contributes to matrix densification, which in turn reduces deflection. Conversely, at low replacement levels (1–2%), the pozzolanic activity of marble dust may not be fully activated, and the dominance of recycled aggregates, which typically exhibit higher deformation due to weaker interfacial zones, becomes more pronounced. The deviation in deflection across all mixes ranged from − 115% to + 14%, with negative values indicating lower deflection than the control. At the 7% replacement level, the deflection was 11% lower than that of the conventional concrete, aligning well with the earlier observation of optimal performance in flexural strength. While 1% and 2% of mixes showed favorable flexural strength, their deflection behavior was less desirable for structural applications due to excessive deformation. Overall, the 7% marble dust replacement emerged as the most balanced mix in terms of both strength and serviceability criteria. The results also compare favorably with those reported by Latif et al. [ 38 ], showing approximately 2% improvement in deflection control. These findings collectively indicate that the incorporation of marble dust in concrete formulations has a noticeable influence on central deflection behavior. The optimum proportions, as observed in batches B2 and B8, highlight the potential benefits of utilizing recycled aggregates and marble dust in enhancing the structural performance of concrete. Further comparison of the results with the findings of Latif et al. [ 38 ] Shows that deflection control in this study was 6% better. After testing, the failure of the specimens was observed (Fig. 12) and was identified as flexural failure-characterized by cracking and breakage of the specimen near its center, extending from top to bottom. This aligns with the theoretical basis for the failure mode of plain concrete prisms. The nature of the failure also demonstrates the feasibility of using recycled aggregates and marble dust in structural concrete applications. 5. Conclusion This study evaluated the effect of binary blending in concrete by partially replacing conventional coarse aggregates with recycled aggregates obtained from demolished concrete and replacing cement with marble dust. Flexural strength, central deflection, and failure modes were examined under two-point loading, which provides a more realistic simulation of structural behavior compared to central-point loading. A total of thirty-three prism specimens (500 mm × 100 mm × 100 mm) were cast using a 1:2:4 mix and a constant water–cement ratio of 0.55 across eleven batches. Among these, one batch served as the control mix with 100% conventional materials to enable comparison with the modified mixes. The experimental results revealed that a mix with 7% marble dust as a cement replacement and 50% recycled coarse aggregates achieved a 15% reduction in flexural strength while offering an 11% improvement in deflection control compared to the control mix. This highlights the potential of using recycled and waste-based materials to produce sustainable concrete with acceptable structural performance. The findings emphasize the importance of careful material selection and mix proportioning in achieving an optimal balance between strength and serviceability. The proposed blend offers a practical approach for incorporating industrial waste into concrete production without compromising structural integrity. Declarations No conflict The authors declare no conflict at any stage of this research work. Ethical Approval Not Applicable Consent of Participate Not Applicable Consent to Publish Not Applicable Competing interests The authors have no relevant financial or non-financial interests to disclose Funding sources The authors declare that no funds, grants, or other support were received during the preparation of this manuscript. Author Contribution Shuban Ali *: Manuscript drafting, formatting, literature review, and final editing.Wazir Ali Brohi: Experimental design, execution of tests, data collection.Bashir Ahmed Memon: Conceptualization, project supervision, critical review of methodology.Gulzar Hussain: Manuscript Writing, testing lab data collectionMohsin Ali: Data analysis and preparation of figures and tables.Sagar Ali: Laboratory setup, calibration of equipment, execution of hands-on experiments Data Availability Statement Availability of data and material All data generated or analyzed during this study are included in this published article. Additional datasets are available from the corresponding author upon reasonable request. References Memon BA, Buller A. Recent development on use of demolished concrete as coarse aggregates. 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Quaid-E-Awam Univ Res J Eng Sci Technol Nawabshah. 2020;18(1):11–8. https://doi.org/10.13140/RG.2.2.13361.40800 . Ahmad J, Zaid O, Shahzaib M, Abdullah MU, Ullah A, Ullah R. Mechanical properties of sustainable concrete modified by adding marble slurry as cement substitution. AIMS Mater Sci. 2021;8(3). https://doi.org/10.3934/matersci.2021022 . Zamir Hashmi SR, Khan MI, Khahro SH, Zaid O, Shahid Siddique M, Md NI, Yusoff. Prediction of strength properties of concrete containing waste marble aggregate and stone dust—modeling and optimization using RSM. Materials. 2022;15(22):8024. https://doi.org/10.3390/ma15228024 . Sharma N, Thakur MS, Kumar R, Malik MA, Alahmadi AA, Alwetaishi M, Alzaed AN. Assessing waste marble powder impact on concrete flexural strength using Gaussian process, SVM, and ANFIS, Processes 10(12) (2022) 2745. https://doi.org/10.3390/pr10122745 Basaran B, Kalkan I, Aksoylu C, Özkılıç YO, Sabri MMS. Effects of Waste Powder, Fine and Coarse Marble Aggregates on Concrete Compressive Strength. Sustainability. 2022;14(21):14388. https://doi.org/10.3390/su142114388 . Karalar M, Özkılıç YO, Aksoylu C, Sabri Sabri MM, Beskopylny AN, Stel’makh SA, Shcherban’ EM. Flexural behavior of reinforced concrete beams using waste marble powder towards application of sustainable concrete. Front Mater. 2022;9:1068791. https://doi.org/10.3389/fmats.2022.1068791 . Meena CM C. P., and, Agrawal HK. effect of marle dust and recycled aggregate on Compressive strength of concrete. irjmetS 4(9) (2022). https://www.irjmets.com/uploadedfiles/paper/issue_9_september_2022/30022/final/fin_irjmets1663395090.pdf Dhanalakshmi A, Hameed MS. Strength properties of concrete using marble dust powder. East Asian J Multidisc Res. 2022. https://doi.org/10.55927/eajmr.v1i11.1785 . Standard U. ASTM C150/C150M-18 Standard specification for Portland cement, West Conshohocken, PA: ASTM International. Available online at: www.astm. Org (2018). https://doi.org/www.astm.org Standard U, ASTM C136/C136M-14, Conshohocken W. PA: ASTM International. Available online at: www.astm. Org (2020). https://doi.org/10.1520/C0136_C0136M-14 Laserna S, Montero J. Influence of natural aggregates typology on recycled concrete strength properties. Constr Build Mater. 2016;115:78–86. https://doi.org/10.1016/j.conbuildmat.2016.04.037 . Bairagi N, Ravande K, Pareek V. Behaviour of concrete with different proportions of natural and recycled aggregates. Resour Conserv Recycl. 1993;9(1–2):109–26. https://mail.etasr.com/index.php/ETASR/article/view/3013 . Oad M, Memon B. Compressive strength of concrete cylinders using coarse aggregates from old concrete, 1st National Conference on Civil Engineering (NCCE 2013-14)-(Modern Trends and Advancements), 2014. https://doi.org/10.13140/RG.2.2.20772.73602 standard U. C143/C143M – 20, West Conshohocken, PA: ASTM International. Available online at: www.astm. org (2020). https://doi.org/10.1520/c0143_c0143m-20 Standard U, ASTM C78/C78M-22, Conshohocken W. PA: ASTM International. Available online at: www.astm. org (2022). https://doi.org/10.1520/c0078_c0078m-22 Latif F, Memon BA, Oad M, Latif A, Memon AR. Flexural Strength and Modulus of Elasticity of Concrete Beam Cast with Binary Blending of Recycled Concrete Aggregate and Marble Dust, Quaid-e-Awam University Research. J Eng Sci Technol. 2023;21(1):113–24. https://doi.org/10.52584/QRJ.2101.14 . Additional Declarations No competing interests reported. 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Ali","email":"data:image/png;base64,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","orcid":"","institution":"Shenzhen University","correspondingAuthor":true,"prefix":"","firstName":"Shuban","middleName":"","lastName":"Ali","suffix":""},{"id":513923625,"identity":"fca78516-14d7-4e08-b279-8ae49ae7065a","order_by":1,"name":"Wazir Ali Brohi","email":"","orcid":"","institution":"Quaid-e-Awam University of Engineering, Science and 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2","display":"","copyAsset":false,"role":"figure","size":25374,"visible":true,"origin":"","legend":"\u003cp\u003eSieve analysis of coarse aggregates\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7383472/v1/2bcf7d09ef621be3e3adf0f3.jpg"},{"id":91566521,"identity":"9154426d-affd-42fd-9dfa-4db2985213c7","added_by":"auto","created_at":"2025-09-17 19:41:47","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":8287,"visible":true,"origin":"","legend":"\u003cp\u003eMarble dust\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7383472/v1/15c86f273d2f35ab75863f06.jpg"},{"id":91567400,"identity":"1a4d40b1-b376-4450-a211-53673683d6cc","added_by":"auto","created_at":"2025-09-17 20:05:48","extension":"jpg","order_by":4,"title":"Figure 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testing\u003c/p\u003e","description":"","filename":"Picture8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7383472/v1/3fc2757c05e4df6dcc2a2146.jpg"},{"id":91566536,"identity":"279e5471-2690-4194-9d51-cb73617e85cd","added_by":"auto","created_at":"2025-09-17 19:41:48","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":25959,"visible":true,"origin":"","legend":"\u003cp\u003eSlump test values\u003c/p\u003e","description":"","filename":"Picture9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7383472/v1/9f2953bb3a0ac8b146dae003.jpg"},{"id":91566539,"identity":"6c6b633c-f3ad-4a48-a15c-2fdc461894f6","added_by":"auto","created_at":"2025-09-17 19:41:48","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":32427,"visible":true,"origin":"","legend":"\u003cp\u003eAverage flexural strength\u003c/p\u003e","description":"","filename":"Picture10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7383472/v1/8e108eada168584ff95f5dfa.jpg"},{"id":91566534,"identity":"01e2ad05-6f52-44d6-94e4-18fb18424134","added_by":"auto","created_at":"2025-09-17 19:41:48","extension":"jpg","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":32702,"visible":true,"origin":"","legend":"\u003cp\u003eAverage deflection\u003c/p\u003e","description":"","filename":"Picture11.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7383472/v1/ebcf91aff82ad4786c5b1c7f.jpg"},{"id":91566758,"identity":"a1ef91a9-223d-4511-b688-1892ddab6244","added_by":"auto","created_at":"2025-09-17 19:49:48","extension":"jpg","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":21153,"visible":true,"origin":"","legend":"\u003cp\u003eFailure mode\u003c/p\u003e","description":"","filename":"Picture12.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7383472/v1/3bd15e9f2127083efa436fcf.jpg"},{"id":91817728,"identity":"719b5ec4-87b0-4bd8-a913-eab42948d124","added_by":"auto","created_at":"2025-09-22 07:00:35","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1068006,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7383472/v1/2880b7ff-2a13-4364-80bc-c7911987f8d9.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Workability and Flexural Strength of Binary Blended Concrete made with Recycled Aggregates and Marble Dust under Two-Point Loading","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eRecycled aggregates, particularly those derived from demolished concrete waste, have emerged as a necessary and environmentally conscious alternative to natural aggregates. Their usage not only helps conserve natural aggregate reserves but also reduces environmental burdens associated with aggregate mining and waste disposal. Substantial time and effort have been devoted by the research community to understanding their production and behavior in concrete. However, several influencing factors\u0026mdash;such as the presence of adhered mortar on old aggregates, the age and condition of the original structure, its exposure during service life, and the specific processing methods used\u0026mdash;alter the properties of recycled aggregates. Consequently, concrete made with recycled aggregates behaves differently from conventional concrete, both in its fresh and hardened states. These deviations must be carefully addressed before recycled aggregates are utilized in structural applications.\u003c/p\u003e\u003cp\u003eThe concept of using recycled aggregates in concrete is not new; it dates to the late 1940s, when post-war reconstruction efforts created an urgent need to manage large volumes of demolition waste. On-site reuse of these materials as coarse aggregates not only alleviated waste management challenges but also preserved natural resources. However, several practical concerns persist, and many practitioners remain hesitant due to inconsistent performance data and the absence of standardized regulatory frameworks. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] Comprehensive efforts have been made by the research community to understand recycled aggregate behavior in concrete. [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], along with others [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], reviewed the mechanical properties and durability of recycled aggregate concrete (RAC), highlighting challenges and proposing strategies for wider implementation. [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] studied \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{M}_{30}\\)\u003c/span\u003e\u003c/span\u003e Concrete with 100% RCA and recorded reductions in compressive, tensile, and cohesive strength by 16.1%, 20.1%, and 18.1%, respectively, compared to conventional concrete. Conversely, Motlagh [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] Reported compressive strengths up to 7200 psi (49.65 MPa) using 100% recycled aggregates, emphasizing the variability due to source and processing quality. Jagan and Neelakantan [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] Evaluated different mixing approaches\u0026mdash;two-stage, mortar mixing, enveloped mixing, and double mixing\u0026mdash;and found that the mortar mixing method delivered superior performance.\u003c/p\u003e\u003cp\u003eEnhancements in RAC properties have also been pursued through the addition of supplementary materials. The inclusion of 0.5% carbon fibers and 8% silica fume in concrete containing 50% RCA led to a 20% increase in both tensile and flexural strengths [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Various dosages of steel fiber have also been explored. In this regard, researchers in [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] observed substantial improvements in overall mechanical properties with 1% steel fiber content. [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] Extended this investigation, testing steel fiber content ranging from 1\u0026ndash;5% in 0.5% increments. They recorded up to 69% improvement in flexural strength, with expectations of further enhancement at higher fiber volumes. [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] Examined high-strength RAC with 25%, 50%, 75%, and 100% RCA and found consistent reductions across all strength metrics. Similarly, Nandhini et al. [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] observed lower flexural strength and greater deflection in concrete with 100% RCA, although the observed flexural mode of failure was considered a positive outcome.\u003c/p\u003e\u003cp\u003eIn addition to experimental research, numerical and statistical models have been used to predict RAC properties. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] Used 100% RCA and developed a regression model based on geometric and steel properties, yielding a high R\u0026sup2; value of 0.997. [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] Employed numerical modeling using 302 datasets to predict flexural strength with strong accuracy.\u003c/p\u003e\u003cp\u003eOther additives, such as metakaolin, have also been incorporated into RAC to improve performance. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] Found that 20% metakaolin content allowed compressive strength levels comparable to conventional concrete. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] Also observed this percentage as optimal, noting improvements in all strength parameters and modulus of elasticity. Their work also introduced predictive models for broader parameter estimation.\u003c/p\u003e\u003cp\u003eDemolition waste is not the only source of concern; primary industrial processes such as marble quarrying also produce substantial amounts of waste in the form of dust and slurry. With growing construction activity, the marble industry has seen a parallel increase in waste output. This waste, typically discarded with minimal treatment, presents both environmental and logistical challenges due to limited landfill space. Marble waste can be processed into fine marble powder through drying and grinding. This powder, which possesses cementitious properties, shows potential as a partial cement replacement in concrete. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Several researchers have reviewed its performance in cement replacement applications, highlighting strength enhancement and reductions in CO₂ emissions during cement production. [\u003cspan additionalcitationids=\"CR20\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Vashist and Naval [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] A 3% increase in 7-day compressive strength was reported, and 2% was reported at 28 days using 5% MD and 15% RCA. Similarly, Memon et al. [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] An 8.3% increase in compressive strength was found using the same dosage of MD as cement replacement. Ahmed et al. [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] Developed numerical models to predict tensile and flexural strength of RAC with MD, and the results closely matched experimental data. Hashmi et al. [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] Also applied modeling techniques to forecast strength parameters with a 5% prediction error. Another study [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] Utilized Gaussian process regression, support vector machines, and ANFIS modeling using 202 datasets, with Gaussian process yielding the most accurate predictions. Basaran et al. [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] Used marble waste as both fine and coarse aggregates and identified 50% as the optimum replacement level. Karalar et al. [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] Studied the flexural behavior of reinforced concrete beams with MD dosages up to 40%, concluding that a 10% replacement was optimal for strength improvements in beams with balanced steel ratios. Meena et al. [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] observed a 13.5% increase in compressive strength at 7.5% MD replacement, while Dhanalakshmi and Hameed [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] Reported a 54.5% increase at a 10% replacement level.\u003c/p\u003e\u003cp\u003eOverall, extensive research has addressed the use of both recycled aggregates and marble dust in conventional concrete. Their combined use has also been explored to some extent, with promising results. However, there is a clear lack of consistency in reported findings, which continues to limit confidence in widespread implementation. Rigorous material testing remains essential for ensuring reliable mechanical behavior. Among mechanical tests, flexural strength assessment is especially important for understanding bending behavior in concrete elements. Although central-point loading is commonly used, it does not accurately reflect real structural conditions. Two-point loading is more representative of actual service loading and offers better insights into performance.\u003c/p\u003e\u003cp\u003eTherefore, the present study aims to evaluate the combined effect of recycled aggregates from demolished concrete and marble dust as cement replacement on the flexural strength of concrete under two-point loading. The objective is to determine optimal replacement levels that maintain acceptable strength and deflection performance while supporting sustainable material use. The findings are expected to enhance understanding of blended waste concrete behavior and serve as a reference for future research and structural design guidelines.\u003c/p\u003e"},{"header":"2. Materials and testing","content":"\u003cp\u003eThe conventional ingredients used in this study included ordinary Portland cement, hill sand (fine aggregates), crushed stone (coarse aggregates), and potable water. The ordinary Portland cement (Lucky Star brand) exhibited a fineness of 96% on the #100 sieve. The initial and final setting times were recorded as 64 and 370 minutes, respectively, with a standard consistency of 31%. These values indicate compliance with the requirements of ASTM C150/C150M. [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. The fine aggregates (hill sand) were tested for essential properties such as water absorption (1.04%), specific gravity (2.52), loss on ignition (2.31%), and fineness modulus (2.86). Sieve analysis was conducted by ASTM C136/C136M. [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e] To determine the gradation of the material. The particle size distribution, including comparisons with the ASTM-defined minimum and maximum limits, is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The results confirm that the fine aggregates meet the standard grading criteria.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe coarse aggregates (crushed stone) were also evaluated for key physical characteristics. Water absorption, specific gravity, abrasion resistance, and fineness modules were measured as 1.5%, 2.5%, 12.6%, and 4.5%, respectively. A Sieve analysis was again conducted according to ASTM C136/C136M. The grading curves for both conventional and recycled coarse aggregates are presented in Fig.\u0026nbsp;2, along with the ASTM-defined boundaries. Both aggregate types were observed to fall within the acceptable limit defined by the standard.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Recycled aggregates\u003c/h2\u003e\u003cp\u003eTo obtain recycled coarse aggregates, large concrete blocks sourced from the demolition of a reinforced concrete residential unit were manually broken down using hammers. The maximum aggregate size was limited to 25 mm to ensure consistency with standard gradation requirements. After crushing, the aggregates were thoroughly washed to remove dust and contaminants and manually sorted to eliminate unwanted materials such as wood, plastics, and metal fragments. The processed aggregates were then dried in the laboratory for 24 hours before testing.\u003c/p\u003e\u003cp\u003eThe basic physical properties of the recycled aggregates were subsequently evaluated. The water absorption, specific gravity, abrasion resistance, and fineness modulus were recorded as 4.0%, 2.27, 23.15%, and 4.48, respectively. The fineness modulus was computed using sieve analysis results, conducted by ASTM C136/C136M. These values fall within acceptable limits for coarse aggregates as defined by relevant ASTM standards. The gradation curve for the recycled aggregates, along with ASTM-specified minimum and maximum boundaries, is presented in \u003cb\u003eFig.\u0026nbsp;2\u003c/b\u003e.\u003c/p\u003e\u003cp\u003ePotable water was used throughout the experimental program for washing, mixing, and curing purposes. The water had a pH value of 6.9, confirming its suitability for concrete applications by ASTM C1602.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Marble Dust\u003c/h2\u003e\u003cp\u003eMarble dust is a byproduct generated during both the quarrying of marble blocks and the cutting of these blocks into tiles of desired dimensions. These processes not only produce significant quantities of fine dust and slurry but also contribute to carbon dioxide emissions due to the operation of heavy machinery. During cutting, water is used extensively, resulting in the formation of wet slurry, which eventually dries into hardened boulders. These waste forms\u0026mdash;dust, slurry, and hardened residue\u0026mdash;pose environmental and aesthetic concerns and require proper disposal to prevent negative impacts on the surrounding area and its inhabitants.\u003c/p\u003e\u003cp\u003eSimilar to construction and demolition waste, marble waste is commonly dumped in landfills. However, due to limited landfill availability and increasing urbanization, the disposal of marble waste has become a pressing issue in many parts of the world. Previous research has shown that marble dust exhibits pozzolanic and filler-like properties, making it a viable partial replacement for cement. Its use not only reduces the demand for cement production, thereby lowering associated CO₂ emissions, but also helps mitigate the challenges of marble waste management.\u003c/p\u003e\u003cp\u003eIn this study, marble dust was utilized as a partial cement replacement. The material was sourced from local marble cutting workshops and subsequently ground to a fine powder. To ensure its compatibility with cementitious materials, the powder was sieved using a #100 sieve. The fineness of the marble dust was recorded at 94.7%, which is comparable to the 96% fineness of the ordinary Portland cement used in the study. A visual representation of the marble dust material is provided in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Mix proportion and slump test\u003c/h2\u003e\u003cp\u003eFor the preparation of concrete samples, a 1:2:4 mix ratio was selected, as it is a commonly used standard mix in the construction industry. Both conventional and recycled aggregates were used in equal proportions, according to the recommendations of previous studies [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] and [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e], which suggests that this ratio minimizes strength loss when incorporating recycled aggregates. Marble dust was used as a partial cement replacement at replacement levels ranging from 1\u0026ndash;10%, in 1% increments. This resulted in ten experimental mixes (labeled MD1 to MD10). Additionally, one control mix was prepared without marble dust, bringing the total number of mixes used in the study to eleven. For all mixes, a constant water-to-binder (w/b) ratio of 0.55 was adopted to account for the higher water demand associated with recycled aggregates.\u003c/p\u003e\u003cp\u003eThe workability of each concrete mix was evaluated using the slump cone test, conducted by ASTM C143. [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. The concrete ingredients were thoroughly mixed in a rotating drum mixer. The slump cone was filled in three layers, with each layer being compacted using twenty-five strokes of a tamping rod. After leveling the top surface, the cone was carefully lifted in the standard manner, and the vertical settlement (slump) of the concrete was measured immediately. A photograph showing one of the mixes during slump testing is provided in Fig.\u0026nbsp;4, and the results of all mixes are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSlump values\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"9\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003e#\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMix\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCement (Kg)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMarble dust (Kg)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eFA\u003c/p\u003e\u003cp\u003e(Kg)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eCA\u003c/p\u003e\u003cp\u003e(Kg)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eRA\u003c/p\u003e\u003cp\u003e(Kg)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eSlump value\u003c/p\u003e\u003cp\u003e(mm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003e% deviation with CC\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" 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colname=\"c7\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-23.46\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e10.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" 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colname=\"c1\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e10.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-48.15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.38\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e10.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-61.73\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e10.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-75.31\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e10.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-88.89\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Sample preparation and curing\u003c/h2\u003e\u003cp\u003eFor the experimental program described in this study, concrete prism specimens with dimensions of 500 mm 100 mm 100 mm \u0026times; 100 mm were prepared. Standard steel molds were used, cleaned, and oiled before casting. For each mix batch, three prism specimens were cast, resulting in a total of 36 specimens across all batches. The quantities of concrete ingredients used to produce three specimens per batch are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, corresponding to approximately 0.015 m\u0026sup3; of concrete per mix.\u003c/p\u003e\u003cp\u003eConcrete was mixed in a mechanical drum mixer until a uniform consistency was achieved. The fresh concrete was then placed into the molds in layers and compacted using a table vibrator to ensure proper consolidation and eliminate entrapped air. The filled molds were left undisturbed for 24 hours to allow initial setting. After this period, the specimens were demolded and air-dried at room temperature for one day (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eFollowing the initial drying phase, all specimens were fully immersed in potable water and cured for 28 days under standard laboratory conditions to ensure proper hydration (Fig.\u0026nbsp;6). Curing was performed at a controlled temperature of 20\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C and relative humidity above 95%, as per ASTM C192/C192M\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Specimen testing","content":"\u003cp\u003eAfter completing the 28-day curing period, the concrete prism specimens were removed from the water tank, their surfaces gently wiped with a clean cloth and allowed to dry air at ambient laboratory conditions for 24 hours. The specimens were tested under a two-point loading configuration, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e7\u003c/span\u003e. Flexural testing was conducted using a universal testing machine (UTM), where the load was applied symmetrically at the third points of the specimen span to create a constant moment region between the loading points.\u003c/p\u003e\u003cp\u003eThe load gradually increased at a controlled rate of 0.5 kN/sec until complete failure of the specimen occurred. A representative image of a specimen under loading is shown in Fig.\u0026nbsp;8. During testing, the maximum applied load and the corresponding central deflection were recorded for each specimen. The flexural strength was then calculated using the failure load and specimen dimensions, based on the standard equation for third-point loading. [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eThe computed flexural strength and central point deflection values for each specimen in all batches are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. These results serve as the basis for evaluating the influence of recycled aggregates and marble dust on the flexural performance of concrete.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eFlexural strength and maximum deflection\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"11\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e#\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eMix\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c5\" namest=\"c3\"\u003e\u003cp\u003eLoad (kN)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c8\" namest=\"c6\"\u003e\u003cp\u003eDeflection (mm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c11\" namest=\"c9\"\u003e\u003cp\u003eFlexural Strength (MPa)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e1\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e7.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e7.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e8.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e5.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e5.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e5.64\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e6.10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e2\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e7.96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e7.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e7.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e5.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e6.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e5.97\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e5.94\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e5.39\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e3\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e7.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e7.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e5.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e5.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e6.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e4.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e5.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e5.73\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e4.30\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e4\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e6.94\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e6.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e4.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e5.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e4.59\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e5\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e5.90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e6.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e4.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e5.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e4.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e4.96\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e6\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e6.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e6.96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e4.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e4.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e5.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e5.22\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e7\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6.90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e5.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e8.99\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e5.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e4.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e4.49\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e8\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e6.87\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e6.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e4.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e4.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e5.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e4.77\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e9\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e6.87\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e5.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e4.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e5.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e4.43\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e10\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e5.23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e5.64\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e5.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e4.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e3.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e4.23\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e11\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMD10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e4.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e5.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e5.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e4.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e3.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e3.64\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"4. Results and discussion","content":"\u003cp\u003eThe obtained results demonstrate the variation in basic properties between recycled and conventional aggregates, which is consistent with findings reported in the literature. The inferior performance of recycled aggregates is primarily attributed to the presence of adhered mortar, the age and previous service conditions of the source concrete, and the heterogeneous nature of the material. The porous structure of the attached mortar significantly increases water demand. Specifically, the water absorption of recycled aggregates was recorded to be 166% higher than that of conventional aggregates. Additionally, a 9% reduction in specific gravity and an 84% increase in abrasion loss were observed, further highlighting the impact of the residual mortar and previous use. The fineness modulus of recycled aggregates remained relatively like that of conventional aggregates, indicating comparable particle size distribution.\u003c/p\u003e\u003cp\u003eThese deviations in physical properties must be carefully considered during mix design to avoid issues in both the fresh and hardened states of concrete. In the current study, adjustments were made to the mix design to accommodate the higher water demand of recycled aggregates. The physical properties of fine aggregates, cement, and water were also evaluated earlier and found to be within the allowable limits specified in the relevant ASTM standards.\u003c/p\u003e\u003cp\u003eThe workability of the concrete mixes was assessed using the slump cone test, with results previously listed and graphically presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e9\u003c/span\u003e. The results indicate that the incorporation of marble dust as a partial cement replacement significantly reduced workability. As the marble dust content increased, a consistent decrease in slump values was observed. The reduction in slump ranged from 14\u0026ndash;89%, with the maximum loss occurring at the highest replacement level. This trend suggests that marble dust increases the water demand of the mix, likely due to its fine particle size and higher surface area. In addition, the marble dust acts as a filler material, occupying voids between fine and coarse aggregates, which restricts fluidity and contributes to the observed decrease in slump. To maintain desired workability levels, adjustments in mixed design, such as water content modification or the use of superplasticizers, may be necessary when incorporating higher percentages of marble dust.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe flexural strength values, computed from the recorded failure loads in the previous section, are compared with those of the control mix (conventional concrete) in Fig.\u0026nbsp;10. Like the slump results, flexural strength was affected by the incorporation of both recycled aggregates and marble dust, with the effect becoming more prominent as the dosage of marble dust increased. The reduction in flexural strength ranged from 0.63\u0026ndash;34% across the tested mixes. At 1% marble dust replacement, the strength reduction was less than 1%, which can be considered negligible. However, at 2%, a more noticeable loss of 9% was recorded. Between 1% and 6%, the strength results exhibited some fluctuation, which may be attributed to variations in workmanship and the incomplete pozzolanic reaction of the marble dust at lower replacement levels.\u003c/p\u003e\u003cp\u003eAt 7% marble dust replacement, a strength reduction of approximately 15% was observed. Beyond this level, the reduction in flexural strength continued to increase steadily with higher marble dust content. The observed decline is likely due to the dilution effect of replacing cement with a non-reactive or slowly reacting filler, which limits the development of hydration products responsible for strength.\u003c/p\u003e\u003cp\u003eInterestingly, the strength loss commonly associated with the use of recycled aggregates appears to be partially offset by the addition of marble dust. In particular, the 1% marble dust replacement yielded a flexural strength nearly equivalent to that of conventional concrete, suggesting a beneficial synergy. From a sustainability perspective, the 7% replacement of cement with marble dust may be treated as optimum with a loss of strength equal to 15%, offering a balance between strength performance and environmental benefits. At this dosage, the strength reduction remains within acceptable limits for structural applications, provided appropriate considerations are made during structural design to ensure durability and serviceability.\u003c/p\u003e\u003cp\u003eThe recorded central deflection values for all prism specimens during testing were previously presented. The average deflection values for each batch are compared with those of the control concrete (without marble dust) in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e11\u003c/span\u003e. It can be observed that the first two mixes, containing 1% and 2% marble dust, exhibited higher deflection than the conventional concrete, indicating increased deformation capacity. However, from 3\u0026ndash;9% replacement, a gradual reduction in deflection was recorded. Interestingly, at 10% marble dust replacement, the deflection again increased beyond that of the control mix.\u003c/p\u003e\u003cp\u003eThis trend suggests that marble dust, when used at moderate levels, improves the compactness and bonding within the concrete matrix. Its fine particle size helps fill voids and contributes to matrix densification, which in turn reduces deflection. Conversely, at low replacement levels (1\u0026ndash;2%), the pozzolanic activity of marble dust may not be fully activated, and the dominance of recycled aggregates, which typically exhibit higher deformation due to weaker interfacial zones, becomes more pronounced.\u003c/p\u003e\u003cp\u003eThe deviation in deflection across all mixes ranged from \u0026minus;\u0026thinsp;115% to +\u0026thinsp;14%, with negative values indicating lower deflection than the control. At the 7% replacement level, the deflection was 11% lower than that of the conventional concrete, aligning well with the earlier observation of optimal performance in flexural strength. While 1% and 2% of mixes showed favorable flexural strength, their deflection behavior was less desirable for structural applications due to excessive deformation.\u003c/p\u003e\u003cp\u003eOverall, the 7% marble dust replacement emerged as the most balanced mix in terms of both strength and serviceability criteria. The results also compare favorably with those reported by Latif et al. [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e], showing approximately 2% improvement in deflection control.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThese findings collectively indicate that the incorporation of marble dust in concrete formulations has a noticeable influence on central deflection behavior. The optimum proportions, as observed in batches B2 and B8, highlight the potential benefits of utilizing recycled aggregates and marble dust in enhancing the structural performance of concrete. Further comparison of the results with the findings of Latif et al. [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e] Shows that deflection control in this study was 6% better.\u003c/p\u003e\u003cp\u003eAfter testing, the failure of the specimens was observed (Fig.\u0026nbsp;12) and was identified as flexural failure-characterized by cracking and breakage of the specimen near its center, extending from top to bottom. This aligns with the theoretical basis for the failure mode of plain concrete prisms. The nature of the failure also demonstrates the feasibility of using recycled aggregates and marble dust in structural concrete applications.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThis study evaluated the effect of binary blending in concrete by partially replacing conventional coarse aggregates with recycled aggregates obtained from demolished concrete and replacing cement with marble dust. Flexural strength, central deflection, and failure modes were examined under two-point loading, which provides a more realistic simulation of structural behavior compared to central-point loading. A total of thirty-three prism specimens (500 mm \u0026times; 100 mm \u0026times; 100 mm) were cast using a 1:2:4 mix and a constant water\u0026ndash;cement ratio of 0.55 across eleven batches. Among these, one batch served as the control mix with 100% conventional materials to enable comparison with the modified mixes. The experimental results revealed that a mix with 7% marble dust as a cement replacement and 50% recycled coarse aggregates achieved a 15% reduction in flexural strength while offering an 11% improvement in deflection control compared to the control mix. This highlights the potential of using recycled and waste-based materials to produce sustainable concrete with acceptable structural performance. The findings emphasize the importance of careful material selection and mix proportioning in achieving an optimal balance between strength and serviceability. The proposed blend offers a practical approach for incorporating industrial waste into concrete production without compromising structural integrity.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eNo conflict\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflict at any stage of this research work.\u003c/p\u003e\u003cp\u003e\u003ch2\u003eEthical Approval\u003c/h2\u003e\u003cp\u003eNot Applicable\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003ch2\u003eConsent of Participate\u003c/h2\u003e\u003cp\u003eNot Applicable\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003ch2\u003eConsent to Publish\u003c/h2\u003e\u003cp\u003eNot Applicable\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding sources\u003c/h2\u003e\u003cp\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eShuban Ali *: Manuscript drafting, formatting, literature review, and final editing.Wazir Ali Brohi: Experimental design, execution of tests, data collection.Bashir Ahmed Memon: Conceptualization, project supervision, critical review of methodology.Gulzar Hussain: Manuscript Writing, testing lab data collectionMohsin Ali: Data analysis and preparation of figures and tables.Sagar Ali: Laboratory setup, calibration of equipment, execution of hands-on experiments\u003c/p\u003e\u003ch2\u003eData Availability Statement\u003c/h2\u003e\u003cp\u003eAvailability of data and material\u003c/p\u003e\u003cp\u003eAll data generated or analyzed during this study are included in this published article. Additional datasets are available from the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMemon BA, Buller A. Recent development on use of demolished concrete as coarse aggregates. Int J Emerg Technol Innovative Eng. 2016;2(1):1\u0026ndash;11. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.researchgate.net/publication/328759902_RECENT_DEVELOPMENT_ON_USE_OF_DEMOLISHED_CONCRETE_AS_COARSE_AGGREGATES\u003c/span\u003e\u003cspan address=\"https://www.researchgate.net/publication/328759902_RECENT_DEVELOPMENT_ON_USE_OF_DEMOLISHED_CONCRETE_AS_COARSE_AGGREGATES\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGuo H, Shi C, Guan X, Zhu J, Ding Y, Ling T-C, Zhang H, Wang Y. Durability of recycled aggregate concrete \u0026ndash; A review. 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C143/C143M\u0026thinsp;\u0026ndash;\u0026thinsp;20, West Conshohocken, PA: ASTM International. Available online at: www.astm. org (2020).\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1520/c0143_c0143m-20\u003c/span\u003e\u003cspan address=\"10.1520/c0143_c0143m-20\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eStandard U, ASTM C78/C78M-22, Conshohocken W. PA: ASTM International. Available online at: www.astm. org (2022).\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1520/c0078_c0078m-22\u003c/span\u003e\u003cspan address=\"10.1520/c0078_c0078m-22\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLatif F, Memon BA, Oad M, Latif A, Memon AR. Flexural Strength and Modulus of Elasticity of Concrete Beam Cast with Binary Blending of Recycled Concrete Aggregate and Marble Dust, Quaid-e-Awam University Research. J Eng Sci Technol. 2023;21(1):113\u0026ndash;24. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.52584/QRJ.2101.14\u003c/span\u003e\u003cspan address=\"10.52584/QRJ.2101.14\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-civil-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Civil Engineering](https://www.springer.com/journal/44290)","snPcode":"44290","submissionUrl":"https://submission.nature.com/new-submission/44290","title":"Discover Civil Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Demolished waste, marble dust, workability, flexural strength, two-point loading, sustainable development","lastPublishedDoi":"10.21203/rs.3.rs-7383472/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7383472/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe increasing demand for sustainable construction materials has increased interest in utilizing industrial waste products in concrete production. This research explores the combined effect of recycled coarse aggregates (RCA), obtained from demolished concrete, and marble dust (MD), a byproduct of marble processing, on workability and flexural strength of concrete. Both materials are widely available construction wastes that pose significant disposal challenges. In this study, RCA was used to replace 50% of conventional coarse aggregates, while marble dust replaced cement in varying proportions from 1\u0026ndash;10%, at 1% intervals. A total of twelve concrete mixes were prepared using a standard 1:2:4 mix ratio and a constant water-binder ratio of 0.55. Among these, ten mixes contained both RCA and MD, one served as a control mix with all conventional aggregates and no MD, and one contained RCA but no MD. Workability was evaluated using the slump test, and flexural strength was assessed using standard prisms (100 mm \u0026times; 100 mm \u0026times; 500 mm) tested under two-point loading after 28 days of curing. The results revealed a clear trend of decreasing slump values with increasing marble dust content, indicating reduced workability due to higher water demand. Flexural strength generally declined with higher MD content, but the mix with 7% MD and 50% RCA achieved a balanced performance, exhibiting only a 15% reduction in strength compared to the control mix, while improving central deflection by 11%. These findings demonstrate that a binary blend of RCA and MD can yield eco-efficient concrete with acceptable structural performance, supporting broader adoption of waste materials in construction. The results also highlight the importance of optimized blending ratios to balance strength, ductility, and workability in sustainable concrete applications.\u003c/p\u003e","manuscriptTitle":"Workability and Flexural Strength of Binary Blended Concrete made with Recycled Aggregates and Marble Dust under Two-Point Loading","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-17 19:41:43","doi":"10.21203/rs.3.rs-7383472/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-11-13T11:59:33+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-19T19:57:25+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-19T08:41:19+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-17T21:40:01+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-16T05:21:55+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"97160571015720727927537942346010988527","date":"2025-10-16T03:18:59+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-13T01:20:00+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"31171921338374314281681118149985950434","date":"2025-10-12T05:59:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"249502543500653807866609477603401021081","date":"2025-10-12T05:27:10+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"134325309113699626127288482029430669795","date":"2025-10-11T15:03:01+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-11T03:20:44+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"140590620527398345243744301331863641031","date":"2025-10-09T17:56:36+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"308307235309547274567670566837851378690","date":"2025-10-09T17:01:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"176307210100855436751918096639565451808","date":"2025-09-12T02:25:28+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-09T20:39:05+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-09-08T11:33:28+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-22T10:17:22+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-08-22T10:17:04+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Civil Engineering","date":"2025-08-15T18:26:41+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-civil-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Civil Engineering](https://www.springer.com/journal/44290)","snPcode":"44290","submissionUrl":"https://submission.nature.com/new-submission/44290","title":"Discover Civil Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"09d4a4fa-c343-4526-aaaa-97c9dbfe2338","owner":[],"postedDate":"September 17th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-02-10T06:56:47+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-17 19:41:43","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7383472","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7383472","identity":"rs-7383472","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}