Development of high performance geopolymer concrete with waste rubber and recycle steel fiber: A study on compressive behavior, carbon emissions and economical performance

Ultra-high performance concrete (UHPC) has good application prospects with its high strength, toughness and good durability performance. However, the high carbon emissions and high cost of its constituent materials are significant factors that limit its development and promotion. This study explores the development of a lowcarbon and low-cost rubber modified high performance geopolymer concrete (R-HPGC) using recycled crumb rubber, recycled steel fibers, and low-carbon geopolymer gel. In this study, the compressive experiments of RHPGC with different rubber volume replacement ratios (0, 5 %, 20 %, 35 %, and 50 %) were conducted to explore the laws and mechanisms of the effect of different rubber volume replacement ratios on the failure mode, compressive strength, deformation, and elastic modulus of R-HPGC. The compressive stress-strain model of RHPGC considering the rubber replacement ratio were proposed. Meanwhile, a comprehensive evaluation method based on the carbon emission and cost index of concrete per unit strength is proposed to compare the carbon emissions and economical performance of R-HPGC, UHPC and normal concrete (NC). The results show that the compressive behavior of R-HPGC is determined by the mechanical properties and interactions between the mixed aggregates-geopolymer matrix-recycled steel fibers. At a low rubber replacement ratio (& LE;5 %/& LE;35 %), the compressive strength of R-HPGC can still reach the standard of ultra-high/high performance concrete (& GE;120 MPa/& GE;55 MPa). R-HPGC has a lower comprehensive cost and carbon emission index compared with conventional UHPC. NC has the lowest comprehensive cost index, but its comprehensive carbon emission index is the highest. It is recommended to use a rubber replacement ratio of & LE;5 % for R-HPGC, which provides the best compressive mechanical performance, as well as excellent environmental and economical performance. This study provides a low carbon emission, low cost and high performance concrete that can be designed based on a combination of strength, carbon emission and cost.