Carbonation behavior of Portland cement incorporating polycarboxylate ether superplasticizer : towards carbonation kinetics, microstructural evolution and mechanical properties

Abstract

Polycarboxylate ether (PCE) superplasticizers are crucial in modern concrete, yet their compatibility with carbonation curing, a promising CO<inf>2</inf> sequestration method, remains insufficiently understood. This study systematically examined carbonation behavior of Portland cement (PC) incorporating PCE by analyzing its phase assemblage, microstructure, carbonation heat, solution chemistry and mechanical properties. Results indicated that PCE significantly reduced the carbonation rate. The peak rate of carbonation heat in pure PC reached 0.57 W/g, while the addition of 2.0 % PCE reduced this value by 43.9 %. This reduction was attributed to the adsorption and complexation effects of PCE, the immobilization of CaCO<inf>3</inf> clusters within polymer network, as well as a rapid decrease in solution pH. Furthermore, the aggressive carbonation kinetics amplified the detrimental impact of PCE on microstructural development. This inhibited carbonation at particle boundaries and weakened interparticle bonding, thereby leading to a decline in mechanical performance. These findings offer fundamental insights into the compatibility and limitations of using PCE in combination with carbonation technologies in concrete.