Engineered geopolymer composites: A state-of-the-art review

Engineered cementitious composite (ECC) featuring extraordinary tensile ductility is a promising option for many structural applications but its large-scale manufacture is not eco-friendly due to its binding ingredient, Portland cement. One of the potential alternatives to ECC is engineered geopolymer composites (EGC) that have been increasingly studied in recent years. This paper presents a comprehensive review of the state-of-the-art of EGC in terms of design theory, mix design, fabrication process, engineering properties, durability and environmental benefit, with special focus on the effects of different material composition factors including precursor, activator, aggregate, additive and fibre on the critical material properties of EGC especially uniaxial tensile properties. The correlations between essential mechanical properties are discussed in depth. The unique tensile behaviour of EGC can be tailored by modifying the material composition that would change its internal microstructure and in turn alter the matrix properties and fibre-matrix interfacial behaviour. Compared to typical ECC, around 64% of EGC mixtures have higher tensile strain capacity (over 2.49%) and about 27% of mixtures exhibit larger tensile strength (over 4.86 MPa). Through adjusting the mix design of EGC, it holds promises as a cost-effective and sustainable material for applications against dynamic loadings, fire and chemical attacks, as well as 3D concrete printing. This review summarises the recent advances in EGC and identifies the remaining challenges in development of EGC with desired properties for practical applications.