Review of the Relationship Between the Composition, Strength, and Ultimate Tensile Strain of Engineering Geopolymer Composites

Engineered Geopolymer Composites (EGC) combine the high ductility and multi-crack characteristics of traditional Engineered Cementitious Composites (ECC) with the sound low-carbon advantages of geopolymers, making them a research hotspot in the green high-performance materials. This study focuses on the influence of EGC composition (precursor, activator, fiber and fine aggregate) on its tensile properties and the curing regime for different precursor compositions. The reported results data (with ultimate tensile strain exceeding 2%) from recent EGC studies are collected and reviewed. It concludes the systems and mix proportion ranges that are beneficial to tensile properties in current EGC research: blended system of fly ash and slag as the precursor; blended system of sodium hydroxide and water glass (with a modulus ranging from 1.2 to 1.4 and an alkali equivalent from 4% to 8%) as the activator; PE fiber (with a content of 2.0% and an aspect ratio of 500-750) or PVA fiber (with a content of 1.8-2.0% and an aspect ratio of approximately 300) as the reinforced fiber; silica sand (with a particle size of 100-300 μm) as the fine aggregate. Different curing regimes are selected according to different precursor types, and segmented curing and normal-temperature curing are widely adopted currently. This study reveals the relationship between compressive strength and tensile strain. When the EGC matrix strength is in the range of 25-45 MPa, it is easier to achieve excellent ductility. This study provides a theoretical basis and design reference for the material optimization and engineering application of EGC.