Abstract:
The brittle nature of geopolymer concretes (GPCs) and curing process required in their production are factors that limit their practical applications. It was not detected any study investigating the effect of polypropylene (PP) fiber length and fiber content on sulfate resistance of GPC. The aim of this study is to investigate the effect of PP fibers used in different content and length on sulfate resistance of GPC cured under laboratory conditions. For this purpose, 6 and 12 mm length PP fibers were added to GPC at rate of 0.5, 1.0, and 1.5% by volume of concrete. Samples were cured in laboratory conditions for 28 days, and then exposed to 5% MgSO4 solutions. After the sulfate effect, the changes in physical and mechanical properties of GPC such as compressive strength, tensile strength, weight, ultrasonic pulse velocity (UPV), apparent porosity, and external appearance were investigated. In addition, microstructural analyzes were carried out with scanning electron microscope (SEM). As a result, it was determined that PP fiber additive at rate of 0.5% by volume significantly increased the sulfate resistance by preventing crack growth thanks to bridging function occur between binder phase and interface regions. Since the increased fiber length made it difficult to distribute the fibers homogeneously, 6 mm long PP fibers were more effective in improving the sulfate resistance. © 2022 fib. International Federation for Structural Concrete.