Potential for the liquid carbonation curing of Portland cement using sodium bicarbonate solutions

Abstract

Potential for the liquid carbonation curing of Portland cement (PC) using NaHCO 3 solutions was investigated. The PC paste samples were sealed -cured or immersed in a 0 %, 1 %, 3 %, 5 %, or 10 % NaHCO 3 solution after undergoing one day of initial curing. The characterization and quantification of the samples and NaHCO 3 solutions at various curing ages were performed using X-ray diffractometry, thermogravimetry, 29 Si nuclear magnetic resonance spectroscopy, inductively coupled plasma mass spectrometry, and compressive strength measurements. The test results revealed that the use of NaHCO 3 solution as a carbonation curing medium partially carbonated the hydrates, resulting in the formation of calcium carbonate and CO 2 -bearing AFm phases. In addition, the NaHCO 3 solution enhanced the reaction degree of clinkers. The carbonation rate further increased at higher NaHCO 3 concentrations. Inductively coupled plasma mass spectrometry results indicated that Ca leaching from the PC samples rarely occurred because of the high Na concentration in the NaHCO 3 solution and the presence of stable CaCO 3 in the samples. The compressive strengths of the samples cured in the NaHCO 3 solution were higher than those of the samples sealed -cured samples at later stages.