Sugarcane bagasse ash as a partial replacement for cement in paste and mortar formulation – A case in the Philippines

Abstract

The quality of sugarcane bagasse ash (SCBA) varies significantly from one locality to another. It greatly influences its performance when used as cement replacement, thus requiring actual empirical data to be generated. This research explored the potential of locally available SCBA in the Philippines as a partial cement replacement material and assessed the appropriate formulations of the paste component with SCBA as part of the cement to be used for mortar and concrete production in the future. Mixtures with different SCBA-to-binder ratios (SBR) up to 20%, and water-to-binder ratios (WBR), were formulated to determine their effects on the consistency and setting time of paste, consistency of fresh mortar, density, and compressive strength of hardened mortar. Multivariate regression analysis was adopted to better interpret the influence of SBR and WBR on the different responses and generate models for their subsequent prediction, including the water requirement, to achieve normal consistency. It was found that increasing SBR from 0.00 to 0.20 increased the water demand for the paste from 0.27 to 0.36 WBR. An increase in the WBR subsequently increases the initial setting time to as much as 198 ± 16 min and the final setting time to 288 ± 4 min. The water demand for mortars also increased with increasing SBR to achieve the same workability. Generally, the models generated enabled good predictability (≥90% accuracy) of the water requirements of both paste and mortar. The density and compressive strength of mortars improved with SBR at 0.05 but then decreased as the SBR was increased. However, mixtures with SBR at 0.10 reached a compressive strength comparable to mixtures with pure cement, rendering the maximum amount that the cement can be replaced at 10%.