Effects of intense ultraviolet irradiation on drying shrinkage and microstructural characteristics of cement mortar

The intense UV irradiation factor in the plateau area is easy to ignore, but it may have adverse effects on the microstructure and properties of concrete. Theredore, to clarify the evolution characteristics and the corresponding mechanism of the drying shrinkage of cement-based materials under intense UV irradiation environments at high altitudes cement mortars incorporating three types of mineral admixture were prepared to investigate the drying shrinkage, mass loss and microstructure, respectively. The hydration process and microstructure of samples were discussed in detail by microscopic experiments including TG-DTG, MIP, XRD, and IR patterns analysis. The results show that the mass loss and drying shrinkage of the cement-mineral admixture mortar exposed to intense UV irradiation were higher than those under the standard environment. Under intense UV radiation environment, the total porosity, mesoporosity (<50 nm), and carbonization degree of each group of samples increased. However, UV irradiation did not change the phase composition, chemical bond type, and polymerization degree of the C-S-H gel of the cement-based material. The incorporation of fly ash and slag resulted in the reduction of drying shrinkage of mortars, an increase in carbonation degree, and decreasing the hydration degree.