Factors Influencing the Hydration, Dimensional Stability, and Strength Development of the OPC-CSA-Anhydrite Ternary System

Abstract

Due to the advantages of high early strength and rapid setting, ternary systems consisting of ordinary Portland clinker (OPC), calcium sulphoaluminate (CSA) clinker, and anhydrite have broad application prospects. However, further studies need to be undertaken to find a more optimal mixing proportion of this ternary binder in order to meet basic performance requirements. In this paper, isothermal calorimetric tests, chemical shrinkage tests, drying shrinkage tests, and compressive strength tests were carried out to systematically identify the effect of the OPC/CSA ratio and anhydrite dosage on the hydration, mechanical property development, and dimensional stability of ternary binders. It was found that a higher CSA content leads to a higher cumulative hydration heat, a shorter acceleration period, and a delayed induction period, which can be ascribed to the retardation of C3S at a high aluminate concentration. However, a higher addition of anhydrite can retard the main peak of hydration despite promoting the intermediate peak and improving the hydration reaction rate. The drying shrinkage of blends decreases first along with the CSA proportion and then increases. Moreover, a higher anhydrite content mitigates the drying shrinkage and hinders the strength development. Finally, considering the properties of both the fresh and hardened binder, the ternary blends with 5% anhydrite and OPC/CSA ratios ranging from 3/7 to 2/8 were identified as most suitable for applications that require a high early strength, stable late strength, and small level of shrinkage.

Recycle Option for Municipal Solid Waste Incineration Fly Ash (MSWIFA) as a Partial Replacement for Cement in Mortars Containing Calcium Sulfoaluminate Cement (CSA) and Portland Cement to Save the Environment and Natural Resources

“…It was necessary because of the extensive swelling of the mortars. The CSA/OPC ratio was reported to be optimal in the range of 70:30–80:20 [ 34 ]. In this research, the CSA/OPC ratio of 63:37 was previously examined and proven to cause the lowest volume changes in cement.…”

Recent progress and technical challenges in using calcium sulfoaluminate (CSA) cement

“…It is also worth mentioning the compressive strength development of Portland cement-CSA cement-anhydrite ternary systems. The amount of anhydrite content and the ratio of Portland cement to CSA cement is the most important factor that influences strength development [81,122].…”

Fabrication and Properties of Blended Calcium Sulfoaluminate Cements Based on Thermally Treated Reservoir Sediments

“…In this regard, there is noticeable interest in calcium sulfoaluminate (CSA) cements for their relevant technical properties [47][48][49][50][51][52][53][54][55][56][57][58] coupled with their environmentally friendly features [59,60]. CSA cements are obtained by mixing a clinker (derived from heating a meal composed of natural gypsum, bauxite, and limestone) with a source of calcium sulfate (e.g., anhydrite or natural gypsum).…”