Effects of the use of agricultural ashes, metakaolin and hydrated-lime on the behavior of self-compacting concretes

Abstract

Self-compacting concrete (SCC) is an innovative product, which has fluidity and cohesion to cover the entire length of the piece and fill the spaces between reinforcement. However, currently, its use in construction sites is linked to a high consumption of cement. This generates a series of environmental problems such as depletion of natural resources and increased CO2 emissions. To mitigate these environmental problems, it is necessary to seek supplementary, locally available materials, to provide a sustainable and efficient way forward for the construction industry. In this perspective, this research investigates the effects of the use of metakaolin (MK), sugar cane bagasse ash (SCBA), rice husk ash (RHA) and hydrated-lime (HL) on rheological (slump flow, J-ring and V-funnel), mechanical (compressive strength) and durability (electrical resistivity, accelerated carbonation and mercury intrusion porosimetry) behavior in SCC. Portland Cement was replaced from 0% to 60% by mineral admixtures in mixtures with and without 10% HL. The results indicated that the SCC produced with agricultural ashes presented physical behaviors compatible with the standards and obtained compressive strength equivalent to the reference SCC (REF). Moreover, these concretes presented carbonation depth lower than the normative values and electrical resistivity significantly higher than the SCC-REF, reducing the probability of corrosion of the steel bars and, therefore, validating the use of ash obtained from industrial bio-waste in the production of SCC. The HL also presented itself as a good re-alkalizer of the cement matrix.