Mechanical performance and durability of geopolymer lightweight rubber concrete

This research focuses on producing and testing a type of geopolymer concrete as an alternative to the conventional Portland cement concrete. The proposed concrete incorporates lightweight expanded clay aggregate (LECA) and rubber from car tyre waste which results in the production of a new concrete: “geopolymer LECA-Rubcrete”. A total of ten geopolymer concrete mixes were produced using rubber and LECA as partial replacements of fine and coarse aggregates, respectively. Variables such as the ratio of geopolymer binders, LECA pre-treatment, concrete curing method, and mixing procedures were examined. Physical, mechanical, and durability tests were conducted including workability, compressive strength, drying shrinkage, water absorption, surface abrasion, and carbonation. This research aimed to provide the necessary information needed to develop lightweight geopolymer Rubcrete structures to reduce carbon emissions and move a step closer towards a greener future. The results indicated that lightweight geopolymer Rubcrete is a suitable alternative to lightweight conventional concrete with similar or better durability properties. The workability increased by 9% and 20% when using rubber and LECA, respectively; however, the compressive strength decreased by 32% and 67%, respectively. Using 25% slag to 75% fly-ash decreased the workability by 44% and increased the strength by 47%. Specimens cured in the ambient condition showed less strength compared to those cured in water. Heat + water curing showed less strength in all mixes, except in mixes with no lightweight materials and with high fly-ash content, which showed 16–21% strength increase. Of the tested mixes, geopolymer LECA-Rubcrete mix that has high slag content showed comparable or better performance than that showed by Portland cement LECA-Rubcrete mix in all measured characteristics.