Risk of early age cracking in geopolymer concrete due to restrained shrinkage

Abstract

In this paper, experimental tests were carried out in order to measure early-age shrinkage and tensile creep of geopolymer concrete and assess their influence on early age cracking in reinforced concrete members. Two mixes of geopolymer concrete were tested. For the first mix, the specimens were heat-cured at a temperature of either 60 °C or 90 °C. For the second mix, the specimens were cured under ambient conditions. Tensile creep was directly measured using unreinforced dog-bone shaped specimens subjected to sustained axial tension. The shrinkage induced stress tests were performed on restrained geopolymer concrete rings. The results show that the tensile creep coefficient and shrinkage strains in geopolymer concrete are affected by the curing temperature and duration. Higher curing temperature leads to less tensile creep and shrinkage strains. Heat-cured geopolymer concrete demonstrated a lower early-age shrinkage and higher tensile creep coefficient, compared to the control ordinary Portland cement (OPC) concrete. Both restrained ring test and simulations confirm that heat-cured geopolymer concrete can relax undesirable stresses in concrete caused by restrained shrinkage, and reduce the risk of early-age cracking.