Microstructural alteration of calcium sulfoaluminate cement-based materials exposed to accelerated carbonation conditions

Abstract

This dissertation investigates the microstructural alteration of calcium sulfoaluminate (CSA) cement-based materials exposed to accelerated carbonation conditions. CSA cement, which represents an ecologically friendly alternative to Portland cement, has been rapidly explored over decades due to its potential of lowering the associated CO2 emissions. Meanwhile, since most of the cementitious materials are exposed to air, it is necessary to clarify the deterioration mechanism induced by carbonation in the materials. However, the fundamental understanding on the microstructural modification of CSA cement upon carbonation is restricted due to a lack of available works. This dissertation explores the carbonation behavior of CSA-based materials by investigating the fundamental degradation mechanism and microstructural changes in these materials exposed to carbonation. To this end, this dissertation is composed of as follows: 1) unveiling the hydration kinetics and local Al network development of CSA cement with different sulfate contents, 2) characterizing the role of MgO in CSA cements upon carbonation, 3) inspecting the carbonation behavior of blast furnace slag-blended CSA cements upon carbonation, and 4) identifying the role of initial sulfate content on the carbonation properties of blast furnace slag-blended CSA cements. In addition, carbonation curing was adopted and the phase evolution of the carbonation-cured CSA cement-based materials exposed to an electrically leaching condition was explored. The obtained results provide new insight into the properties of CSA-based materials exposed to carbonation, which establishes fundamental knowledge of deterioration phenomena driven by the accelerated carbonation. In addition, with the understanding on the carbonation mechanism of the CSA-based materials, carbonation curing of these materials and their properties upon accelerated leaching were provided. The thesis is concluded by summarizing the implication of the results and potential topics.