Beyond Burnt Bricks: Reassessing Otukpo Soil for Sustainable Construction Applications

The Otukpo Burnt Brick Factory has remained inactive for over three decades despite repeated government efforts to revive it. Given the abundance of clay-rich soils in the region and the growing need for sustainable, low-cost building materials, this study explores the potential of Otukpo soils for uncalcined brick production and use as supplementary cementitious materials (SCMs). Four representative samples (OT1–OT4) were characterized through mechanical, chemical, and mineralogical tests aligned with international standards for natural pozzolans. All samples exhibited high oxide contents (SiO₂ + Al₂O₃ + Fe₂O₃ > 93 %), low SO₃ and loss-on-ignition (~6 %), and adequate fineness (13–17 % retained on a 45 µm sieve), suggestive of favorable pozzolanic properties. Strength Activity Indices (SAI) based on unconfined compressive strength (UCS) and cube strength showed that OT3 and OT4 exceeded 100% of the NIS 87:2007 (≥2500 kPa at 28 days) threshold at 56 days with 5 wt.% sodium hydroxide and cement activation. Both also surpassed the NBC’s 14-day cube strength requirement (≥1600 kPa) and maintained water absorption below the 20 % limit for bricks. Unstabilized samples collapsed upon immersion, indicating excessive porosity/poor durability without enhancements. These findings strongly suggest that the Otukpo soils, particularly OT3 and OT4, are suitable for low-energy brick and SCM production.