{"paper_id":"6f6fbc85-2310-4c67-9592-ddce4d3cefb7","body_text":"Immobilization of Ca2+ by OH- ions on calcium silicate hydrates | 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 Article Immobilization of Ca 2+ by OH - ions on calcium silicate hydrates Ziga Casar, Laura Mismetti, Maya Harris, Hugh Greenwell, Karen Scrivener, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6340288/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The interface of calcium silicate hydrate (C-S-H) plays a a crucial role in the mobility of ions through hardened cement paste and thus in the long term durability of concrete structures. Here, we combine experimental zeta potential measurements with non-equilibrium molecular dynamics simulations to elucidate the surface state of C-S-H under cement-relevant conditions. Our findings reveal that the co-adsorption of Ca 2+ and OH - ions overcompensates the negative surface charge of C-S-H, originating from deprotonated silanol groups, thereby forming a surface adsorption network. This mechanism is governed by the interplay between solution pH and calcium speciation, where higher pH values favor the formation of calcium-hydroxide solution complexes. Consequently, an increase in pH leads to a higher Ca/Si ratio in C-S-H and a greater adsorption of these complexes, further increasing the effective surface charge density. Conversely, a reduction in pH promotes ion desorption, leading to a progressive decrease in the Ca/Si and the decrease in effective surface charge. These findings provide new insights into the long-term compositional evolution of C-S-H in cement paste, with implications for phase stability, mechanical performance, and concrete durability. Physical sciences/Materials science/Nanoscale materials Physical sciences/Materials science/Structural materials calcium silicate hydrate C-S-H molecular dynamics zeta potential cement chemistry Full Text Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryInformation.pdf Supplementary information Data.zip Dataset 1 Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {\"props\":{\"pageProps\":{\"initialData\":{\"identity\":\"rs-6340288\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":true,\"archivedVersions\":[],\"articleType\":\"Article\",\"associatedPublications\":[],\"authors\":[{\"id\":436381815,\"identity\":\"84fe6b1c-95e2-452c-b3b2-19e9e6ab8dcb\",\"order_by\":0,\"name\":\"Ziga Casar\",\"email\":\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6ElEQVRIiWNgGAWjYBADHgYG5gNA2gLMJFYLWwIDQ4IE8VpAugyI08Lffvzh5wqGOhl59zMfH/P+kJDj5znA+OFjDm4tEmdyjCXPMLDxGJ7J3WzMkyBhLNnbwCw5cxtuLQYMOQySDQw8PIYNudukgVoSN5xnYGPmxaeF//njnw0MEjyG/W+eEalFIsEMaIsBj7xEDhtEy9kG/Fokbrwxs2wwSOAxkHhmbDgnDeiXnoPNeP3C35/++GZDRZ29fH/ywwdvbGyAIZZ88MNHPFpggcBgcADOY2wgpB4C5IlUNwpGwSgYBSMQAACnRkUUpnKVZgAAAABJRU5ErkJggg==\",\"orcid\":\"https://orcid.org/0000-0001-6598-4766\",\"institution\":\"Princeton University\",\"correspondingAuthor\":true,\"prefix\":\"\",\"firstName\":\"Ziga\",\"middleName\":\"\",\"lastName\":\"Casar\",\"suffix\":\"\"},{\"id\":436381816,\"identity\":\"85a8fa25-87cc-4376-a953-02a78d41942b\",\"order_by\":1,\"name\":\"Laura Mismetti\",\"email\":\"\",\"orcid\":\"https://orcid.org/0009-0009-0513-2145\",\"institution\":\"University of Durham\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Laura\",\"middleName\":\"\",\"lastName\":\"Mismetti\",\"suffix\":\"\"},{\"id\":436381817,\"identity\":\"decf3ee8-a1ef-479b-8ef2-99a57e7c94c4\",\"order_by\":2,\"name\":\"Maya Harris\",\"email\":\"\",\"orcid\":\"https://orcid.org/0000-0003-1165-1506\",\"institution\":\"EPFL\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Maya\",\"middleName\":\"\",\"lastName\":\"Harris\",\"suffix\":\"\"},{\"id\":436381818,\"identity\":\"ea776218-46d7-4a0a-bbbb-5caea74a4dd6\",\"order_by\":3,\"name\":\"Hugh Greenwell\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Durham University\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Hugh\",\"middleName\":\"\",\"lastName\":\"Greenwell\",\"suffix\":\"\"},{\"id\":436381819,\"identity\":\"f996e409-8f7c-413f-bde6-6502074ef831\",\"order_by\":4,\"name\":\"Karen Scrivener\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Iowa State University\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Karen\",\"middleName\":\"\",\"lastName\":\"Scrivener\",\"suffix\":\"\"},{\"id\":436381820,\"identity\":\"6744a1d9-eb7a-453f-833f-2756a6b25417\",\"order_by\":5,\"name\":\"Milan Předota\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"University of South Bohemia in České Budějovice\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Milan\",\"middleName\":\"\",\"lastName\":\"Předota\",\"suffix\":\"\"},{\"id\":436381821,\"identity\":\"2416febe-d95b-4bcf-a776-3d1d89fd9227\",\"order_by\":6,\"name\":\"Paul Bowen\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Ecole Polytechnique Federale de Lausanne\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Paul\",\"middleName\":\"\",\"lastName\":\"Bowen\",\"suffix\":\"\"}],\"badges\":[],\"createdAt\":\"2025-03-30 21:25:09\",\"currentVersionCode\":1,\"declarations\":\"\",\"doi\":\"10.21203/rs.3.rs-6340288/v1\",\"doiUrl\":\"https://doi.org/10.21203/rs.3.rs-6340288/v1\",\"draftVersion\":[],\"editorialEvents\":[],\"editorialNote\":\"\",\"failedWorkflow\":false,\"files\":[{\"id\":80351302,\"identity\":\"39dc1e2e-abea-468d-99a9-7058ddc50d04\",\"added_by\":\"auto\",\"created_at\":\"2025-04-10 23:33:25\",\"extension\":\"pdf\",\"order_by\":1,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"manuscript-pdf\",\"size\":1653327,\"visible\":true,\"origin\":\"\",\"legend\":\"Article File\",\"description\":\"\",\"filename\":\"Manuscript.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6340288/v1_covered_649ad6fb-6d62-419a-8805-ecf1d61b01de.pdf\"},{\"id\":80125449,\"identity\":\"1c8621a3-3195-49ae-9120-6718fcd6112c\",\"added_by\":\"auto\",\"created_at\":\"2025-04-08 08:17:40\",\"extension\":\"pdf\",\"order_by\":1,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"supplement\",\"size\":4608366,\"visible\":true,\"origin\":\"\",\"legend\":\"Supplementary information\",\"description\":\"\",\"filename\":\"SupplementaryInformation.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6340288/v1/e347cd37b3218589b22e26cf.pdf\"},{\"id\":80124985,\"identity\":\"0757081f-b7af-455a-9096-656897334c3f\",\"added_by\":\"auto\",\"created_at\":\"2025-04-08 08:09:40\",\"extension\":\"zip\",\"order_by\":2,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"supplement\",\"size\":5168570,\"visible\":true,\"origin\":\"\",\"legend\":\"Dataset 1\",\"description\":\"\",\"filename\":\"Data.zip\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6340288/v1/f0769b38687e9a79cdd3a25c.zip\"}],\"financialInterests\":\"There is \\u003cb\\u003eNO\\u003c/b\\u003e Competing Interest.\",\"formattedTitle\":\"Immobilization of Ca\\u003csup\\u003e2+\\u003c/sup\\u003e by OH\\u003csup\\u003e-\\u003c/sup\\u003e ions on calcium silicate hydrates\",\"fulltext\":[],\"fulltextSource\":\"\",\"fullText\":\"\",\"funders\":[],\"hasAdminPriorityOnWorkflow\":false,\"hasManuscriptDocX\":false,\"hasOptedInToPreprint\":false,\"hasPassedJournalQc\":\"\",\"hasAnyPriority\":true,\"hideJournal\":true,\"highlight\":\"\",\"institution\":\"\",\"isAcceptedByJournal\":false,\"isAuthorSuppliedPdf\":true,\"isDeskRejected\":\"\",\"isHiddenFromSearch\":false,\"isInQc\":false,\"isInWorkflow\":false,\"isPdf\":true,\"isPdfUpToDate\":true,\"isWithdrawnOrRetracted\":false,\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"researchsquare\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":true,\"externalIdentity\":\"\",\"sideBox\":\"\",\"snPcode\":\"\",\"submissionUrl\":\"/submission\",\"title\":\"Research Square\",\"twitterHandle\":\"researchsquare\",\"acdcEnabled\":true,\"dfaEnabled\":false,\"editorialSystem\":\"\",\"reportingPortfolio\":\"\",\"inReviewEnabled\":false,\"inReviewRevisionsEnabled\":true},\"keywords\":\"calcium silicate hydrate, C-S-H, molecular dynamics, zeta potential, cement chemistry\",\"lastPublishedDoi\":\"10.21203/rs.3.rs-6340288/v1\",\"lastPublishedDoiUrl\":\"https://doi.org/10.21203/rs.3.rs-6340288/v1\",\"license\":{\"name\":\"CC BY 4.0\",\"url\":\"https://creativecommons.org/licenses/by/4.0/\"},\"manuscriptAbstract\":\"The interface of calcium silicate hydrate (C-S-H) plays a a crucial role in the mobility of ions through hardened cement paste and thus in the long term durability of concrete structures. Here, we combine experimental zeta potential measurements with non-equilibrium molecular dynamics simulations to elucidate the surface state of C-S-H under cement-relevant conditions. Our findings reveal that the co-adsorption of Ca\\u003csup\\u003e2+\\u003c/sup\\u003e and OH\\u003csup\\u003e-\\u003c/sup\\u003e ions overcompensates the negative surface charge of C-S-H, originating from deprotonated silanol groups, thereby forming a surface adsorption network. This mechanism is governed by the interplay between solution pH and calcium speciation, where higher pH values favor the formation of calcium-hydroxide solution complexes. Consequently, an increase in pH leads to a higher Ca/Si ratio in C-S-H and a greater adsorption of these complexes, further increasing the effective surface charge density. Conversely, a reduction in pH promotes ion desorption, leading to a progressive decrease in the Ca/Si and the decrease in effective surface charge. These findings provide new insights into the long-term compositional evolution of C-S-H in cement paste, with implications for phase stability, mechanical performance, and concrete durability.\",\"manuscriptTitle\":\"Immobilization of Ca2+ by OH- ions on calcium silicate hydrates\",\"msid\":\"\",\"msnumber\":\"\",\"nonDraftVersions\":[{\"code\":1,\"date\":\"2025-04-08 08:09:35\",\"doi\":\"10.21203/rs.3.rs-6340288/v1\",\"editorialEvents\":[{\"type\":\"communityComments\",\"content\":0}],\"status\":\"published\",\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"researchsquare\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":true,\"externalIdentity\":\"\",\"sideBox\":\"\",\"snPcode\":\"\",\"submissionUrl\":\"/submission\",\"title\":\"Research Square\",\"twitterHandle\":\"researchsquare\",\"acdcEnabled\":true,\"dfaEnabled\":false,\"editorialSystem\":\"\",\"reportingPortfolio\":\"\",\"inReviewEnabled\":false,\"inReviewRevisionsEnabled\":true}}],\"origin\":\"\",\"ownerIdentity\":\"ebfaad2c-f885-46ef-b463-d648236ed099\",\"owner\":[],\"postedDate\":\"April 8th, 2025\",\"published\":true,\"recentEditorialEvents\":[],\"rejectedJournal\":[],\"revision\":\"\",\"amendment\":\"\",\"status\":\"posted\",\"subjectAreas\":[{\"id\":46462827,\"name\":\"Physical sciences/Materials science/Nanoscale materials\"},{\"id\":46462828,\"name\":\"Physical sciences/Materials science/Structural materials\"}],\"tags\":[],\"updatedAt\":\"2025-06-17T13:01:03+00:00\",\"versionOfRecord\":[],\"versionCreatedAt\":\"2025-04-08 08:09:35\",\"video\":\"\",\"vorDoi\":\"\",\"vorDoiUrl\":\"\",\"workflowStages\":[]},\"version\":\"v1\",\"identity\":\"rs-6340288\",\"journalConfig\":\"researchsquare\"},\"__N_SSP\":true},\"page\":\"/article/[identity]/[[...version]]\",\"query\":{\"redirect\":\"/article/rs-6340288\",\"identity\":\"rs-6340288\",\"version\":[\"v1\"]},\"buildId\":\"XKTyCvWXoU3ODBz1xrDgd\",\"isFallback\":false,\"isExperimentalCompile\":false,\"dynamicIds\":[84888],\"gssp\":true,\"scriptLoader\":[]}","source_license":"CC-BY-4.0","license_restricted":false}