Evolution of different microstructure and influence on the characterization of pore structure and mechanical properties of cement mortar exposed to freezing-thawing: The role of cement fineness

The pore structure and mechanical properties of cementitious material significantly are affected by changes in microstructure induced by cement fineness. The aim of this study was to assess the influence of different cement fineness and freezing-thawing cycles (FTCs) on the microstructural changes and establish the relationship between these changes and the mechanical properties. Besides, its influence on the pore structure was further clarified through 3D modeling. The testing results indicated that the use of finer cement could cause a remarkable increase of about 10-45% in flexural strength and increase of about 7-47% in compressive strength, along with a substantial reduction of about 25-70% in the total porosity for different FTCs. A relationship between the mechanical properties and the pore structures was also established: large porosity volumes due to coarser cement tend to decrease the mechanical strength while small porosity volumes due to finer cement, related with improved structure of cement paste, were linked to a rise in mechanical strength. In addition, the 3D modeling enabled realistic estimation of the pore volume after FTCs and showed that the number and size of pores as well as total pore volume increased with increment of FTCs and diminished with augmentation of the cement fineness.