Abstract
Calcium sulfoaluminate (CSA) cement can be used as an alternative binder in concrete, partially or fully replacing ordinary Portland cement. While CSA cement considerably accelerates the mechanical properties development, the rapid evolution of the microstructure together with the high water demand cause rapid and large volume changes at early ages. As volume changes may lead to early-age cracking, measures to reduce them may be required In this paper, autogenous and drying shrinkage are studied in mortars prepared with Portland cement, CSA cement or a 50/50 blend as binder. Very fast self-desiccation and high autogenous shrinkage of the CSA-based mortar were observed compared to the mortar made with Portland cement. On the other hand, the early-age volume changes can be limited if a blend of the two cements is used. The blended system revealed a bi-modal trend in the evolution of self-desiccation and autogenous shrinkage, in which the initial fast self-desiccation and shrinkage enter the dormant phase after the first couple of days and again start after about 28 days.
Highlights
With a yearly production of 4 billion tons [1], ordinary Portland cement (OPC) is essential for the construction industry but it represents an ecological issue due to the high energy consumption and large amounts of CO2 emitted during its production [2, 3]
While the mixtures containing Calcium sulfoaluminate (CSA) show a faster development of the mechanical properties at early ages, the PC mixture eventually ends up
The early-age shrinkage evolution for three mortars based on limestone Portland cement, CSA cement and a 50/50 blend of the two was investigated
Summary
With a yearly production of 4 billion tons [1], ordinary Portland cement (OPC) is essential for the construction industry but it represents an ecological issue due to the high energy consumption and large amounts of CO2 emitted during its production [2, 3]. Considering the blended system CSA/OPC [10, 11], it was observed that the precipitation of AFt during the hydration process of CSA is the main process responsible for the characteristic properties of the hardening material, such as rapid setting, early-age strength development [12] and shrinkage compensation [8, 12]. In these blends OPC reaction becomes evident after a few days [11]. Some other factors were found to influence the expansive behavior of CSA-based systems [13], such as the type and amount of calcium sulfate [14, 15] and the amount of OPC in the blends [11]
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