Synergistic Effects of Ethylene Glycol Solution and Polycarboxylate Superplasticizer on the Hydration of Calcium Sulphoaluminate Cement at −10°C

In recent years, there has been great interest in cold weather concreting methods that utilize cold materials, which require less energy and emit less CO2 during cold weather. The aim of this research is to evaluate the combined effects of ethylene glycol (EG) and a polycarboxylate superplasticizer (PCE) on calcium sulphoaluminate (CSA) cement pastes, which are mixed using a cold weather concreting method with cold materials, at a temperature of −10°C. The temperature curves were recorded using a temperature logging device for CSA cement mixed with water or EG solution at −10°C. The compressive strength was measured after 3, 7, and 28 days. X-ray diffraction (XRD), thermogravimetry analysis (TGA), and backscattered electron image analysis (BSE-IA) were used to analyze the evolution of hydration. The results showed that CSA cement paste mixed with EG solution did not freeze at −10°C, whereas CSA cement paste mixed with water froze at the same temperature. Reducing the water-to-cement (W/C) ratio improved the compressive strength but had no significant impact on the amount of hydration product or the degree of hydration. Lowering the ethylene glycol-to-cement (E/C) ratio increased the amount of hydration products and the degree of hydration. The addition of PCE significantly accelerated the hydration evolution of CSA cement, which effectively improved the compressive strength. The 28-day compressive strength (36.5 MPa) of cement paste CPWE, with a W/C ratio of 0.23, E/C ratio of 0.1, and 1.8% PCE, significantly increased, reached 570% of that measured in cement paste CO (6.4 MPa), which had a high degree of hydration and a dense microstructure.