Microstructure and Freeze-Thaw Resistance of Portland Cement Mortars

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J. Korean Ceram. Soc. > Volume 28(11); 1991 > Article

Journal of the Korean Ceramic Society 1991;28(11): 917.

포틀랜드 시멘트 모르타르의 미세구조와 동결융해저항성에 대하여

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전남대학교 무기재료공학과

Microstructure and Freeze-Thaw Resistance of Portland Cement Mortars

ABSTRACT

For the present experiment five Portland cement mortars are in order: mortars with two different water/ cement ratios (W/C=0.45 and 0.50, each having no chemical additive), and those with an additive such as superplasticizer, air-entraining agent or water-repelling agent. We fix the W/C ratio of mortars having additive so that their pastes can yield the same workability as that of the cement mortar of W/C=0.50 with no additive. It is shown that the freeze-thaw resistivity depends heavily on the characteristic of wide pores. Despite a good deal of wide pores, the air-entrained specimen shows a good freeze-thaw resistivity due to appropriate air-pores. And also the specimen with water-repelling agent, which proves to cause the microstructure to become hydrophobic, make good resistance to freeze-thaw cycles in spite of its high wide-porosity. Our suggestion is that the freeze-thaw durability of Portland cement mortar/concrete can be more effectively enhanced by using air-entraining agent or water-repelling agent, and simutaneously by taking proper measures against foaming and/or the increased tendency of wide-pore building due to additive.