Ambient- and oven-cured geopolymer concretes under active confinement

The axial compressive behavior of actively confined geopolymer concretes (GPCs) is investigated in this study. Two different batches of GPCs were manufactured using either 80% fly ash (FA)/20% ground granulated blast furnace slag (GGBS) (80/20 series) or 50% FA/50% GGBS (50/50 series). Two different curing conditions of ambient (at 23 °C) and oven (at 70 °C) curing were considered to evaluate the influence of the curing condition on the axial compressive behavior of actively-confined GPCs. Geopolymer concretes were confined by a Hoek cell at different confining pressures ranging from 5 to 25 MPa. Axial compression tests were conducted on unconfined and actively confined specimens to investigate the influence of the composition of the GPC mix, curing condition, and confining pressure on the behavior of GPCs. It is found that 50/50 series mixes exhibit slightly higher axial peak stress and strain than 80/20 series mixes. The results also show that oven-cured GPCs exhibit a slightly higher axial strength but a slightly lower peak axial strain than ambient-cured GPCs. At a given confining pressure, the GGBS content and curing condition also affect the trend of descending branch of the axial stress-axial strain curve of GPCs. The descending branch slope of GPCs tends to decrease with an increase in GGBS content, and oven-cured GPCs exhibit a slightly steeper descending branch than their ambient-cured counterparts. It is also found that, at a given axial strain, GPCs with a higher GGBS content develop a slightly higher lateral strain, indicating the increased dilation rate of GPCs at a higher GGBS content. These promising findings indicate the possibility of the use of GPC in structural columns in which the concrete will be subjected to lateral confinement.