Analysis of the effect of hydration characteristics of Lime Pozzolan Gypsum binders on their Mechanical properties.

Abstract

This study evaluated volcanic ash-based binders with volcanic ash to lime to gypsum mix ratios of 80:15:05, 65:30:05, 75:20:05, and 70:25:05, and assessed compressive strength, hydration level, water absorption, and lime reaction at ages of 3, 7, and 28 days, focusing on durability for N-type blocks (water absorption ≤14%). The 80:15:05 ratio exhibited the highest strength (2–5 MPa), with hydration increasing from 62.5% to 77.5%, showing a good correlation, and reaching 80% on day 7. Water absorption increased from 2.83% to 7.27%, which is within the specified limit. However, the rising porosity might pose a threat to durability. The lime consumption was low (10–12), indicating efficient utilization. The 65:30:05 with surplus lime showed hydration (77.5–80%) but low strength (3.5–4 MPa), as the surplus lime formed weak hydration phases. Water absorption decreased from 5.31% to 4.204%, which is within acceptable limits, but high lime consumption (22–24) fails to enhance durability. The 75:20:05 mix balanced between hydration (75–77.5%) and strength (2.21–5.67 MPa), but lime consumption stood at 15–16, and absorption rose to 5.95%, posing hazards to durability. The 70:25:05 ratio, with 80–80.5% hydration, had flat strength (1.76–3.89 MPa) and high absorption (4.97–9.34%), meeting the standard but losing durability. Reducing porosity and adjusting ash-to-lime ratios can enhance strength and durability for N-type applications. The combined interpretation of free lime content, lime consumption trends, compressive strength development, degree of hydration and durability in terms of water absorption revealed that the binder mix design significantly influences both the rate and effectiveness of the pozzolanic reaction. Among the four tested formulations, Mix 75:20:05 stood out as the most efficient in terms of both reactivity and mechanical performance qualifying it for use in making of blocks while 80:15:5 mix stood out as the most effective for use in the low strength construction as mortar, render etc. because of its lime consumption, degree of hydration positive correlation with compressive strength.