Investigation of pore structure and mechanical property of cement paste subjected to the coupled action of freezing/thawing and calcium leaching

In order to comprehensively understand the degradation of cementitious materials when subjected to the coupled action of calcium leaching and freezing/thawing, changes of the pore structure and the Vickers hardness of cement paste are investigated. In this study, the coupled action are designed as Case I (first leaching then freezing/thawing) and Case II (first freezing/thawing then leaching). The effects of Case I on the mechanical degradation are greater than Case II. This is further clarified by changes of the pore structure. For freezing/thawing, the level of deterioration qualified by hardness decrease is sensitive to the proportion of big pores (i.e., >100 nm). For calcium leaching, it is determined by the amount of CH and C-S-H. In addition, the hardness-porosity relationship is discussed. A quantitative prediction model from theoretical deviations considering influences of pore size is established.