Improving Freeze-Thaw Resistance and Strength Gain of Roller Compacted Fly Ash Concretes with Modified Absorbent Polymer

Abstract

It is difficult to entrain air into roller compacted concrete (RCC) using conventional air entraining agent (AEA) because of its low cement content. This paper examines whether modified absorbent polymer (MAP) can be used as an air entraining admixture to improve both freeze-thaw resistance and strength gain of roller compacted concrete with 4% fly ash content. Modified absorbent polymer is different from superabsorbent polymer because MAP particles are spherical, have low water-absorption capacity, do not entrain additional air by surfactant content, and can release the absorbed water during subsequent hydration. The influence of MAP and AEA on strength and freeze-thaw resistance of RCC is compared. The air void structure and pore structure are evaluated by microscopic imaging, mercury intrusion porosimetry, and nanoindentation. Compared with traditional AEA, the addition of MAP facilitates the formation of a more effective air void network, the improvement of capillary structure, and the enhancement of the strength of the matrix surrounding MAP voids, resulting in significant improvement of freeze-thaw resistance with great increase in strength.