A Review And Comparison Study On Drying Shrinkage Prediction Between Alkali-Activated Fly Ash/Slag And Ordinary Portland Cement

Alkali-activated binder (AAB) concrete is regarded as a green building material due to its high strength, chemical corrosion resistance, and low carbon emission. However, the shrinkage of AAB is more significant than that of ordinary Portland cement (OPC) and hinders the engineering applications of AAB. Current studies related to AAB shrinkage focus on the mechanisms and influencing factors of shrinkage. There are few shrinkage prediction models to guide the structural design. Compared with cement hydration, the hydration and polymerization of AAB are more complex and have many influencing factors. In addition to the factors affecting OPC shrinkage, the types, modulus, and alkali content of the activator can also affect AAB shrinkage. By comparing the results obtained by the existing shrinkage prediction models for OPC concrete and the shrinkage tests of AAB concrete, it is found that the empirical prediction model for OPC concrete cannot predict AAB concrete shrinkage well. Moreover, the theoretical method based on the capillary pressure mechanism also has challenges with predicting AAB concrete shrinkage due to the lack of statistical models related to microscopic parameters such as pore saturation, internal relative humidity, and creep coefficient of gels. According to the Kelvin-Laplace equation and viscoelastic analysis theory, a semi-theoretical prediction model could be established by studying the correlation between the mixed proportion of raw materials and the microscopic parameters of AAB concrete. The model may be one of the most rapid and efficient methods for predicting AAB concrete shrinkage.