Physical, mechanical and microstructural characteristics of cement-locust bean pod ash mortar blend

T.D Akpenpuun,O Olawale,O.I Adesina,B.A Akinyemi,O.J Aladegboye

doi:10.4314/jasem.v23i3.1

Abstract

The need to reduce the environmental pollution resulting from agro-wastes and to source a material that can be used to replace cement in order to reduce the pressure on its consumption necessitated this research. This study evaluated the effect of cement replacement with locust bean pod ash (LBPA) as supplementary cementitious material on the mechanical properties of mortar. The physical properties (workability, initial and final setting times), the compressive strength at 7, 14, 21 and 28 days and microstructural analysis (SEM, EDS, and XRD) were investigated. LBPA were considered at replacement levels of 0, 10, 15, 20 and 30% of cement mass for preparation of the mortar samples. Workability of the cement mortars reduced as the content of LBPA increases, while initial and final setting times increased with a correspnding rise in LBPA content in the matrix. An increase of about 79% in compressive strength at 7 days, 100% at 14 days, 147% at 21 days and 136% at 28 days were recorded with LBPA content of 15% LBPA being the optimum level when compared to control mix. Maximum compressive strength increased with the number of days of curing and ranged between 38.3 and 65 MPa. Microstructural analysis revealed fewer voids and pores, and the presence of dense Calcium silicate hydrate (C-S-H) gels which helped to maintain the optimum compressive strength at 15% LBPA cement replacement level of the mortar.Keywords: compressive; strength; agro-waste; pod; ash

Highlights

Another reason adduced for this pattern is that the low rate of cement hydration in the paste consisting of the locust bean pod ash (LBPA) pozzollan led to an increase in both initial and final setting times on subsequent increase in cement replacement levels (Cordeiro et al, 2012)
Increase in LBPA content led to a progressive increment in compressive strength up to 15% replacement of cement
Further increase in LBPA content beyond this level led to a subsequent decrease in strength because of the lower cement composition and slow hydration process

Summary

Introduction

The flow rate obtained in both cases could be as a result of reduced workability with increase in LBPA content in the mortar mix. Another reason adduced for this pattern is that the low rate of cement hydration in the paste consisting of the LBPA pozzollan led to an increase in both initial and final setting times on subsequent increase in cement replacement levels (Cordeiro et al, 2012).

Results

Conclusion