Predictions of long-term deflection of geopolymer concrete beams

The long-term behaviour of concrete beams constructed with geopolymer concrete (GPC) is investigated. Self-weight and sustained load of 1 kPa are applied on top of the beams at the age of 14 days to simulate construction conditions. Creep tests on cylinders conducted with sustained loading commenced at the ages of 14 days and 28 days. The results from creep tests on GPC show higher creep in the specimens loaded at 14 days than those loaded at 28 days. Predictions of beam deflections are performed by using RCM, EMM and AEMM with input parameters of properties of GPC from experimental data, including elastic modulus, modulus of rupture, creep and shrinkage. These property tests show that GPC can achieve sufficient strength for structural designs, but both compressive strength and flexural tensile strength are affected by drying, which causes differential drying shrinkage and microcracking at the drying surfaces. The predicted deflections by these analysis methods are compared with the experimental results from beams, and show that RCM gives the worse performance of the three methods. The investigation concludes that the AEMM can be used for long-term deflection calculations for GPC beams with minor parameter modifications.