A novel oxalic acid activated calcium silicate cement: strength, microstructure and composition evolution

This study introduces an oxalic acid-activated calcium silicate cement (OACS), where the oxalic acid precursor can be synthesized from CO₂ via electrochemical methods, thereby establishing it as a typical low-carbon cement. Experimental results indicate that the combination of oxalic acid and γ-dicalcium silicate exhibits rapid hardening during reaction. The setting time can be effectively adjusted through (1) lowering the mixing water temperature and (2) partial substitution of oxalic acid with sodium oxalate. Phase characterization reveals crystalline calcium oxalate dihydrate precipitates and extensively polymerized silica gel as the principal reaction products of OACS. Microstructural analysis shows a spatial configuration with silica gel encapsulating unreacted calcium silicate particles, while calcium oxalate deposits occupy interparticle spaces. Progressive pore-filling effects during curing reduce paste porosity over curing time, resulting in OACS pastes achieving a remarkable 3-day compressive strength of approximately 50 MPa, demonstrating excellent early-age performance.