Evaluating Soil Samples From The Vicinity Of The Great Benin Moat For Mud Brick Production And Pozzolanic Potential

Traditional earthen materials and techniques offer a promising solution to the housing infrastructure crisis in Nigeria and sub-Saharan Africa. This exploratory study examines the chemical and physico-mechanical properties of soils used in mud buildings and the historic Benin moat in Benin City, Nigeria, with the aim of adapting them for modern, low-cost housing. Four soil samples were analyzed in raw form and with 5-10% cement and sodium hydroxide (NaOH) stabilization. At 14 days, cube strengths with 5% cement exceeded the 1.6 N/mm² requirement of the Nigerian Building Code (2006) for non-loadbearing sandcrete blocks by over 30%, while unconfined compressive strength (UCS) at 28 days was within 5-6% of the code. However, all samples failed the chloride ion penetration test. The samples met ASTM C618-22 oxide requirements (SiO₂ + Al₂O₃ + Fe₂O₃ > 70%, SO₃ < 4%, K₂O < 1.5%) but showed high loss on ignition (LOI > 23%) and very low strength activity indices (<75%) at 28 days, limiting their pozzolanic performance. Despite this, the high kaolinite content (28– 68%) suggests strong potential for producing metakaolin, a valuable supplementary cementitious material (SCM). While stabilized mud bricks - uncalcined - show promise at 5% cement, further chemical or mechanical treatment is needed to enhance durability and long-term performance.