Environmental impact and durability of carbonated calcium silicate concrete

This paper describes the environment impact of low-lime calcium silicate (Ca₂SiO₄) cement (CSC) that cures by a reaction with gaseous carbon dioxide (CO₂). The production of CSC requires less limestone and lower kiln temperatures than those used for ordinary Portland cement (OPC). This makes it possible to reduce the carbon dioxide emissions at the cement kiln from ∼810 kg/t for OPC to ∼565 kg/t for CSC. The carbon dioxide used in the curing process and captured within CSC-based concrete (CSC-C) is industrial-grade carbon dioxide sourced from waste flue gas streams. The fully hardened CSC-C will contain up to 300 kg of carbon dioxide per tonne of cement used in the concrete formulation. This paper also summarises the performance and durability of CSC-C and OPC concrete (OPC-C). Freeze–thaw and scaling resistance were evaluated as per ASTM C666 and ASTM C672, respectively, the concentrations of ionic species leached from the concretes were measured, efflorescence was evaluated in pavers partially submerged in water, and the expansion and mass changes associated with the exposure to sodium sulfate (Na₂SO₄) and magnesium (Mg) solutions were measured. In each of the durability tests, the CSC-C specimens, made with commercially produced Solidia Cement, performed equivalently or better than the OPC-C specimens.