A comparative study of calcium hydroxide, calcium oxide, calcined dolomite, and metasilicate as activators for slag-based HPC

In this study, the mechanical characteristics and microstructure of high-performance concrete (HPC) were thoroughly investigated and the influences of alkaline earth and metasilicate activators on material properties were comprehensively analyzed. Moreover, the carbon footprint of each mix design was evaluated and the strength to the carbon footprint was quantified. To evaluate the mechanical properties, the samples underwent tests for compressive, tensile, and flexural strengths at 28 days. Microstructure characteristics were analyzed using Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis/Differential Thermal Analysis (TGA/DTA). Additionally, electrical resistance and water absorption tests were conducted. The findings revealed that employing 10% CaO as an HPC activator resulted in the highest compressive strength (80 MPa), flexural strength (6.4 MPa), splitting tensile strength (5.5 MPa), and electrical resistance (445 Ωm). Moreover, these samples exhibited the lowest water absorption percentage (2%). TGA/DTA analysis indicated the highest content of Calcium Silicate Hydrate (C-S-H) in the geopolymer matrix of samples activated with 10% CaO. SEM analysis confirmed the densest microstructure formation in these samples. Moreover, the study demonstrated that using 10% CaO as an HPC activator can yield superior strength to the embodied carbon footprint.