Evaluation of the performance of corncob ash in cement mortars

This paper examined the performance of cement mortars containing corncob ash (CCA) on mortar cementitious system with the addition of two different types of superplasticizers. Corn cobs were burnt in a controlled environment for 2 h, at 600 °C after which the ash was cooled in ambient laboratory environment, sieved with 0.075 mm sieve and characterized using XRF analysis. Mortar samples were prepared with varying percentages of cement replacement with CCA from 0 to 25% at intervals of 5% using a mix ratio of 1:4 and a water binder ratio of 0.6. Cement–CCA mortar prisms (180 numbers) of size 40 mm × 40 mm × 160 mm were cast for compressive and flexural strength tests (cured for durations of 3, 7, 28, 56 and 90 days) and cylindrical specimens (36 numbers) of size 50 mm × 100 mm prepared for durability test. Chloride profiles were also obtained after 90 days of curing. The results showed increase in flexural and compressive strengths across the percentage replacements with increasing curing ages. However, 10% blended cement–CCA with (SPP1) gave optimum strength increase in compressive strength values: 40.5 N/mm 2 ; for SPP2: 38.6 N/mm 2 and control 35.3 N/mm 2 respectively after 90 days of curing. Also, at 10% blended cement–CCA with SPP1 gave the best chloride profile of durability properties in chloride environment having a value of 83.31 mg/L, 158.28 mg/L for SPP2 and a maximum value of 1174.64 mg/L for the control specimens. It shows that 10% blended cement–CCA percentage replacement in the presence of superplasticizers provided the best mechanical and durability properties.