Solving the perpetual problem of imperative use heat curing for fly ash geopolymer cement by using sugar beet waste

Abstract

This study aims to solve the perpetual problem of imperative use heat curing for fly ash (FA) geopolymer cement to obtain reasonable strength, especially at the early ages by using calcinated carbonation lime residue (CCR). The carbonation lime residue is a waste resulting from the sugar beet industry. For this purpose, FA was partially replaced with CCR at ratios fluctuated from 2.5% to 10%, by weight, with a step of 2.5%. FA geopolymer specimens with/without CCR were cured at room temperature. To investigate the effect of CCR on FA geopolymer cement, classical tests of flowability, setting time, compressive strength at various ages, water absorption and total porosity were explored. The results were analyzed by using advanced devices. The results showed that CCR is similar to CaO. The inclusion of CCR decreased setting time, flowability, water absorption and total porosity, whilst the compressive strength, especially at an early age, was enhanced. The optimum ratio of CCR was 7.5%, which provided the highest strength, lowest water absorption, lowest total porosity and acceptable setting time. Including a suitable ratio of CCR can accelerate the polymerization, form C-S-H gel, fill the pores and produce denser microstructure. The inclusion of 10% CCR showed too short setting time which did not provide enough time for handling, casting, compacting and finishing.