Influence of water-to-binder ratio on strength reduction and sulfuric-acid deterioration mitigation in biochar-modified mortar

초록

This study evaluates how the water-to-binder (w/b) ratio influences strength reduction and sulfuric-acid deterioration mitigation in biochar-modified mortar with 10% (by weight) cement replacement. Flowability, 28-day compressive and flexural strength, density, moisture content, and water absorption were measured, and chemical resistance was examined under immersion in 5% H2SO4 and 10% CaCl2 solutions. Biochar incorporation slightly reduced flowability due to increased water demand; however, workability remained within practical limits. Strength decreased markedly at lower w/b ratios, whereas the reduction was substantially alleviated at higher w/b ratios, highlighting the importance of sufficient moisture availability and internal-curing effects. Biochar mixtures exhibited higher moisture content and water absorption, while density remained relatively stable. Under H2SO4 exposure, biochar-modified mortars showed reduced mass and length losses and better retention of structural integrity than the control, with the mitigation effect becoming more evident at higher w/b ratios. In contrast, CaCl2 caused no significant deterioration within the test period.

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