A critical review of engineered geopolymer composite: A low-carbon ultra-high-performance concrete

Bendable concrete or, more formally, engineered cementitious composite (ECC) is a special type of ultra -high-performance concrete that possesses strain-hardening properties with high tensile ductility. Despite their improved performance, ECCs contain about two to three times higher ordinary Portland cement (OPC) content than conventional concrete. Given the high carbon footprint of OPC, the environmental impact of ECCs is sig-nificant. Although copious research has been conducted on replacing OPC in ECCs with low-carbon binders, e.g., blended cements, such materials can only partially replace OPC in ECCs. One promising alternative that can fully replace OPC in ECCs is geopolymer, an alkali-activated cement. Research on replacing OPC with geopolymers in ECCs started about a decade ago, and such composites have become known in the literature as Engineered Geopolymer Composites (EGCs) or Strain-Hardening Geopolymer Composites (SHGCs). This paper provides an extensive literature review of all published studies on EGCs to date. The paper starts with a scientometric analysis using science mapping to provide a holistic overview of the current research progress on EGCs. Comparisons between EGCs and ECCs in terms of their pseudo-strain-hardening behavior and mechanical properties are provided. The effects of varying parameters related to the matrix, fibers, and curing conditions, on the perfor-mance of EGCs, are also discussed. Finally, durability, self-healing, and environmental impact, among other aspects of EGCs, are highlighted. The conducted review revealed the promising potential of EGCs as low-carbon and ultra-high-performance concretes. However, research on EGCs is still developing, and further investigations are needed before the full potential of EGCs can be realized.

Automated summary

Bendable concrete (ECC) has a high carbon footprint due to its high content of ordinary Portland cement (OPC), leading researchers to explore geopolymer composites (EGCs) as a low-carbon alternative with promising potential for ultra-high-performance concrete. While EGCs show great promise as low-carbon and ultra-high-performance concretes, further research is needed to fully realize their potential.