Behaviour of supersulfated cements under accelerated and natural carbonation

Graduate Program in Civil Engineering (PPGEC), Federal University of Technology – Paraná (UTFPR), Pato Branco, Brazil

^* Corresponding author: angulski@utfpr.edu.br

Abstract

It is known that supersulfated cement (SSC) is susceptible to carbonation; however, there are uncertainties regarding the similarity between accelerated and natural carbonation processes. To investigate the behaviour of SSC hydration products, pastes containing 19 % and 15 % calcium sulfate were exposed to 2 % CO₂ (accelerated carbonation) for 7, 14, and 28 days and to atmospheric CO₂ (natural carbonation) for 7, 14, 28, and 56 days. The behaviour of the hydrated products was analyzed using X-ray diffraction (XRD) and thermogravimetric analysis (TGA/DTG). The results show similar behaviours between the two methods, with the complete decomposition of ettringite at the end of the test periods and the formation of calcite, vaterite, aragonite, and gypsum. Carbonation processes occurred more rapidly in accelerated carbonation, with total decomposition of ettringite after only 7 days of exposure for both pastes. Additionally, it was observed that accelerated and natural carbonation led to different performance outcomes for the produced pastes.