Enhancing the Mechanical and Durability Properties of Fly Ash-Based Geopolymer Mortar Modified by Polyvinyl Alcohol Fibers and Styrene Butadiene Rubber Latex

This study investigated three types of fly ash-based geopolymer mortar (FAG) modified with polyvinyl alcohol fiber (PVA) or styrene butadiene rubber (SBR) latex, where the influence of PVA fibers and SBR latex on the mechanical properties and durability of FAG were studied. The sample performance was subsequently interpreted by characterizing the microstructures of modified FAG samples via the use of scanning electron microscopy (SEM), where the internal structural stress and modification mechanisms were clarified by microstructural analysis. The results showed that the incorporation of PVA fibers mainly promotes the mechanical properties of the samples, especially the early flexural strength, and alleviates their dry shrinkage. However, adding SBR latex to the geopolymer mortar damages the compressive strength and increases the dry shrinkage of samples while improving their freeze-thaw resistance and 28-day flexural strength. The results also show that FAGs have great sulfate resistance. Microstructural analysis reveals that while the dehydrated SBR latex is capable of forming a continuous porous film structure, the fibers also facilitate the formation of a three-dimensional network structure between the dense FAG gels; thus, a more stable geopolymer structure is formed, resulting in an improvement in the toughness and durability of the samples. Furthermore, the SBR latex promotes tight connections between the fibers and geopolymer matrix so that the bond strength between the interfacial transition zone (ITZ) is greatly enhanced.