Abstract
This paper presents the results of research into the heat of hydration and activation energy of calcium sulphoaluminate (CSA) cement in terms of the dependence on curing temperature and water/cement ratio. Cement pastes with water/cement ratios in the range of 0.3–0.6 were tested by isothermal calorimetry at 20 °C, 35 °C and 50 °C, with the evolved hydration heat and its rate monitored for 168 h from mixing water with cement. Reference pastes with ordinary Portland cement (OPC) were also tested in the same range. The apparent activation energy of CSA and OPC was determined based on the results of the measurements. CSA pastes exhibited complex thermal behaviour that differed significantly from the thermal behaviour of ordinary Portland cement. The results show that both the w/c ratio and elevated temperature have a meaningful effect on the heat emission and the hydration process of CSA cement pastes. The determined apparent activation energy of CSA revealed its substantial variability and dependence, both on the w/c ratio and the curing temperature.
Highlights
Environmental concerns are one of the most important challenges in current concrete technology, due to the high amount of CO2 emitted to the atmosphere during Portland clinker production
I (OPC)of cements with different pastes, a substantial increase in heat emission for the hydration temperature rise from water/cement ratios measured in isothermal tests at 20 C, 35 C and 50 C are shown can be observed
The process may have been occurring from the start of the test, but with the high amount of heat produced in the exothermic reaction of cement with water, it was not possible to notice the lowering of the generated heat. This claim can be substantiated by the fact that the higher the w/c ratio of the tested calcium sulphoaluminate (CSA) cement pastes, the higher the difference in the heat after 168 h between samples cured at 20 ◦ C
Summary
Environmental concerns are one of the most important challenges in current concrete technology, due to the high amount of CO2 emitted to the atmosphere during Portland clinker production. Due to ettringite being the main product of the hydration process, CSA cement is usually characterized by short initial and final setting times, high early strength, and low shrinkage [15,16]. All those properties are usually considered desirable in practical concrete technology, CSA cement is not widely used due to the high costs of the materials needed to produce the clinker, especially bauxite.
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