Self-compacting concrete using calcium-rich ashes as alternative fillers and heated dry materials to simulate hot weather mixing

Abstract

Algaroba wood (Prosopis juliflora) is commonly used as energy source in the northeast region of Brazil and India, generating rich-calcium carbonate (CaCO₃) ashes as a promising alternative limestone filler. Moreover, concreting in hot climates (for example, in tropical regions) can affect its fresh state conditions owing to the evaporation of the mixing water. Thus, Self-Compacting Concretes (SCCs) incorporating Algaroba ashes were produced using heated dry materials (80 ± 2 ^oC) to simulate hot weather mixing (on site, 50 ± 2 ^oC). In order to simulate the hot weather conditions on site for subsequent control tests over time (in the laboratory), the specimens were cured in water at 20 ± 2 ^oC. The self-compacting ability at the end of mixing was kept constant by extra water addition or superplasticizer overdosing. The partial replacement of 50% of natural lime filler by calcium-rich ash preserved the compressive strength and permeability of mixtures with 100% of limestone filler. Using 50% ash also demanded less water and superplasticizer when submitted to the simulated hot weather mixing.