Effect of Curing Conditions on the Performance of Geopolymer Concrete Based on Granulated Blast Furnace Slag and Metakaolin

Abstract

This study aims to evaluate the performance of granulated blast furnace slag (GBFS) and metakaolin (MK)-based geopolymer concrete (GC) under different curing conditions. GC was derived from a portland self-compacting concrete (PC). Three curing modalities were considered: (1) 20°C−50% relative humidity (RH); (2) 20°C−90% RH; and (3) 20°C-water immersion. The results showed that both PC and GC cured under water possess similar compressive strength. However, GC presented a lower elastic modulus and higher shrinkage and porosity. It was also found that hardening at 90% RH reduces both water porosity and shrinkage and enhances the mechanical performance of GC, which can be explained by the formation of more compacted geopolymer matrix. The validity of a current European standard to predict the compressive strength evolution and shrinkage development was verified. It was established that the standard relationship proposed for the prediction of strength evolution can be extended to GC, and a modification of the shrinkage development model was proposed. Finally, it was concluded that the use of the GBFS/MK mixture overcomes the mechanical performance degradation commonly known for GC immersed in water.