CO2 sequestration using calcium-silicate concrete

Abstract

The potential for using calcium silicate concrete to sequester CO₂ and simultaneously develop strong and durable concrete building products is studied. It is the calcium compounds in cement that react with CO₂ through the early-age carbonation curing, forming geologically stable calcium carbonates. Both type 10 and type 30 Portland cements were investigated as CO₂ binders in concretes with 0%, 25%, 50%, and 75% quartz aggregates and lightweight aggregates. The sequestration took place in a chamber under 0.5 MPa pressure at ambient temperature for a duration of 2 h; a 100% concentration of CO₂ was used to simulate the recovered CO₂ from flue gas. The CO₂ uptake was quantified by direct mass gain and by infrared-based carbon analyzer, and the performance of the carbonated concrete was evaluated by its strength. A CO₂ uptake of 9%–16% by binder mass was achieved in 2 h. The X-ray diffraction spectra showed the presence of strong calcite peaks and a total absence of Ca(OH)₂. The 2 h carbonation strength exceeded the 7 d hydration strength. The calcium silicate concrete approach is shown to be feasible for CO₂ sequestration and would result in technical, environmental, and economical benefits.Key words: CO₂ sequestration, concrete, carbonation curing, calcium carbonates, strength.