Characteristics of interlocking paving blocks made with cashew leaf ash as partial replacement for cement

This study appraised the effect of Cashew Leaf Ash (CLA) as a partial substitute for cement in Interlocking Paving Blocks (IPBs) production as a way of conserving natural resources and transforming agricultural by-products into valuable materials in the construction industry. Cashew leaf calcined at 600°C for 4 h and pulverized in a ball mill for 60 min. was characterised via fluorescence analysis. A total of six IPB mixes of 1:4 (cement: quarry dust) were prepared by replacing cement with CLA at 0 (control), 5, 10, 15, 20 and 25% by weight. The water-to-binder ratio and cement content were maintained at 0.45 and 314 kg/m3, respectively for all IPB mixes. The tests conducted on hardened IPBs were compressive strength, abrasion resistance and water absorption. The results indicated that CLA is useful as supplementary cementitious material based on its chemical composition revealing the sum of SiO2, Al2O3 and Fe2O3 in excess of 50% specified for class C pozzolans. IPBs with low contents of CLA (5 and 10% CLA) yielded between 87.86 and 98.95% of the compressive strength of the control at 28 and 90 days. Also, the IPBs containing 5 and 10% CLA exhibited similar 28-day abrasion resistance and water absorption as the control. IPBs with the incorporation of up to 10% CLA satisfied the minimum strength requirements for non-traffic applications such as, building premises, garden areas and landscaping with minimal load specified by Nigerian Building and Road Research Institute (2006). Thus, the addition of the optimum of 10% CLA as a substitute for cement in IPBs with quarry dust as the sole aggregate in the mix is feasible.