Kinds of concrete shrinkages, their importance and prevention methods
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Cement Wapno Beton Foundation
Publication date: 2021-06-15
Cement Wapno Beton 26(2) 109–117 (2021)
One of the unfavourable properties of concrete is shrinkage which is linked with the volume changes of cement paste. We distinguish the following kinds of shrinkage: – “chemical” shrinkage called also the contraction or Le Chatelier shrinkage, – plastic shrinkage, – autogenic shrinkage or spontaneous, sometimes called auto drying, – drying shrinkage. There are several methods to eliminate concrete shrinkage. The ettringite crystallization is one of the inorganic compounds methods and is based on Klein’s complex addition to cement. This complex is causing the rapid ettringite formation and the shrinkage is diminished. There are also organic admixtures which action is the reduction of the water surface tension. There are surface-active additions that are reducing this tension, in capillaries. The organic admixtures which are diminishing the shrinkage are based on neopentyl glycol or similar chemical compounds. In the study, the shrinkage-reducing admixture BASF Master Life SRA 815 alone and with CaO addition were examined. It was shown that CaO addition is giving very low diminishing of cement shrinkage, contrary to the fluid admixture Master Life SRA 815 which has a high diminishing influence on cement shrinkage. However, the simultaneous addition of CaO is increasing the diminishing influence of this fluid admixture. The addition of Klein’s complex does not influence of shrinkage but its simultaneous addition with Master Life SRA 815 gives higher shrinkage diminishing.