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

Concretos autoadensáveis com cinzas ricas em cálcio como fíler alternativo e materiais secos aquecidos para simular mistura sob clima quente

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.

Keywords:
Self-compacting concrete; Algaroba tree ashes; Hot weather