A novel development of HPC without cement: Mechanical properties and sustainability evaluation

Abstract

In the current study, a new type of high-performance concrete (HPC) called HPC-CAS (calcium oxide-activated slag) is presented. The HPC-CAS is made from calcium oxide-activated slag and is reinforced with steel, basalt, and recycled polyethylene terephthalate (PET) fibers to make it less brittle. To assess the mechanical properties of the samples, five mix designs were produced, including HPC, HPC-CAS without reinforcement, and HPC-CAS reinforced with fibers. Compressive, splitting tensile, and flexural strengths were then determined. In addition, the study evaluated the environmental impact of different mix designs using two methods: IMPACT 2002+ and CML baseline 2000. The findings indicate that in HPC-CAS, calcium oxide serves as the activator for slag, resulting in a compressive strength of 105 MPa, which is only 4.54% lower than that of HPC. Notably, incorporating steel and recycled PET fibers addresses the issue of brittle fracture in HPC and HPC-CAS samples, leading to compressive strengths of 121 MPa and 78 MPa, respectively. When compared to samples without fibers, the inclusion of steel, basalt, and recycled PET fibers in HPC-CAS resulted in improved splitting tensile strengths of 159%, 89%, and 55%, respectively. The samples containing steel, basalt, and recycled PET fibers also revealed flexural strengths with 3.68 and 1.20 times, and 31% increase, respectively, as compared to those without fibers. Overall, the incorporation of fibers significantly enhanced the brittle behavior of the HPC-CAS geopolymer matrix. However, it is important to note that the addition of 3% fibers to HPC-CAS resulted in higher environmental impacts in all categories as compared to HPC-CAS without fibers. Furthermore, the embodied carbon footprint associated with the production of HPC-CAS was found to be significantly lower, with a reduction of approximately 61%. Furthermore, when comparing HPC-CAS to HPC, it is evident that HPC-CAS exhibits decreased adverse effects on human health, ecosystem quality, and resource utilization.