Abstract
Four different air entraining agents are selected. The air entraining effect and their foaming stabilities in cement pore solution; the impact on air entrainment in fresh concrete; and the variations in air voids and their structures in hardened concrete are compared and studied. The results show that the development in porosity of the hardened concrete mixed with different air entraining agents is consistent with the air entrainment in fresh concretes within the first hour, but deviated from the foaming stability of the air entraining agents in cement pore solutions. Carboxylic based air entraining agents generate calcium soap, whereby such moiety can effectively encapsulate air bubbles. While the stability is insignificant in cement pore solution, the impact is obvious in concrete. When employed alone, the air entraining agent failed to improve both air entrainment of fresh concrete and final concrete structure. Instead, a combination of air entraining agents is found to induce a synergetic effect, effectively enabling both the air-entraining performance and the development of an enhanced porous structure of the hardened concrete.
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