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.