Ultra-high performance concrete versus ultra-high performance geopolymer concrete: Mechanical performance, microstructure, and ecological assessment

Abstract

UHPC is a modern cement-based composite with exceptional mechanical characterizations and durability, while also being a high-cost and unsustainable composite. Therefore, ultra-high performance geopolymer concrete (UHPGC) was developed to achieve similar mechanical performance with more economic and ecological benefits. In this study, the engineering characteristics of UHPGC were compared to those of conventional UHPC. Flowability, compressive strength, splitting tensile strength, and load-deflection behavior in flexural, were among the engineering properties compared. Microstructural investigations, including SEM-EDS, MIP, and XRD, as well as economic and ecological impacts, were also examined. The flowability of UHPGC was lower than that of UHPC, but the flowability was still relatively high; additionally, the setting times of geopolymer concrete were very fast compared to UHPC. The early compressive strength of UHPGC was 101 MPa at 7 days, higher than all UHPC, and 133 MPa at 28 days, lower than all UHPC. But, it was revealed that the production of UHPGC had lower CO2 emissions (up to 70%), embodied energy (up to 73%), and cost (up to 64%) than UHPC. Furthermore, the flexural and splitting tensile strengths of UHPGC were lower than the tensile strengths of UHPC. Microscopic investigations showed that the microstructures of UHPGC were more compact and homogeneous at 7 days than those of UHPC, but less compact and homogeneous after 28 days. The manufacturing of UHPGC also offers a sustainable method of industrial waste disposal. In the era of sustainable development, UHPGC could be considered an affordable and environmentally beneficial alternative to conventional UHPC.