Physical properties and carbon dioxide capture of synthetic gamma-C2S cement composites in the early days of curing

Abstract

This study investigates how the porosity and compressive strength of ordinary Portland cement (OPC) blended with different ratios of synthetic gamma dicalcium silicate (γ-C2S) change in the first 28 d of curing. The composites are cured either under normal atmospheric conditions (standard curing) or in a carbon dioxide chamber (accelerated carbonation curing). The carbon dioxide capture experiments are performed under constant conditions (10% carbon dioxide, 20°C and 60% relative humidity) and results are evaluated on days 3, 7 and 28, representative of the early curing days for the blends. The results show that the samples cured under carbonation exhibit higher compressive strengths after 28 d of curing than their corresponding samples cured under standard conditions. The results also show that the porosity of the 20 wt% γ-C2S/OPC blend cured under carbonation conditions is reduced from 29·0% to 19·4%, indicating the densification of the final product. This decrease in porosity is attributed to the formation of calcite and vaterite (μ-CaCO3) phases, by the free calcium oxide inside the pore structure reacting with carbon dioxide. These findings confirm that a 20 wt% γ-C2S/OPC blend cured under carbon dioxide undergoes densification, and this contributes to the enhanced durability and strength of carbon dioxide-cured cement products.