Aragonite formation induced by triethylene glycol and its enhancement to flexural strength in carbonated rankinite cement

Abstract

In this study, triethylene glycol (TEG) was used as a modifier for rankinite (C3S2) cement carbonation to induce the formation of aragonite whiskers and to prepare rankinite cement with high flexural strength. The effects of different admixture amounts of TEG on the in situ aragonite formation and the enhancement in the mechanical strength of C3S2 mortar were mainly explored. The results showed that when the TEG/C3S2 molar ratio, reaction pressure, and temperature were 0.1, 0.1 MPa, and 70 °C, respectively, the aragonite whiskers generated in the hardened cement paste reached 35 % of the solid content. Under the above reaction conditions, the cement mortar specimens that were carbonated for 1 and 7 d had flexural strengths of 3.0 MPa and 9.6 MPa, respectively, which were 50 % and 95.9 % higher than those of the reference sample; furthermore, they had compressive strengths of 9.2 MPa and 60.8 MPa, respectively, which were 31.4 % and 60 % higher than those of the reference sample. In addition, under the same reaction conditions, the CO2 uptake of cement after carbonation for 72 h was 28.4 %. The analysis results showed that the increase in flexural strength could be attributed to the interlaced 3D spatial structure formed by the growth of aragonite whiskers in the cement paste. The results of this study could provide a new route for the preparation of high-flexural-strength cements while utilizing CO2.