COMPARISON OF FLY ASH, PVA FIBER, MGO AND SHRINKAGE-REDUCING ADMIXTURE ON THE FROST RESISTANCE OF FACE SLAB CONCRETE VIA PORE STRUCTURAL AND FRACTAL ANALYSIS

Abstract

Face slab concrete suffers from serious frost damage in the cold regions in China. How to improve the frost resistance of face slab concrete in cold regions is one of the important issues in concrete-faced rockfill dam (CFRD) design and construction. The results in this paper indicate that the frost resistance of concrete can be improved by adding fly ash, fiber, MgO and shrinkage-reducing admixtures (SRAs), and their efficiencies are in the following sequence: (fly ash [Formula: see text] fiber) [Formula: see text] fiber [Formula: see text] fly ash [Formula: see text] MgO [Formula: see text] SRA. The incorporation of 0.8[Formula: see text]kg/m3 polyvinyl alcohol (PVA) fiber and 20[Formula: see text]wt.% fly ash together enhances the compressive strength and tensile capacity of concrete by 6–7% at the late age, whereas the addition of 6[Formula: see text]wt.% MgO or 1[Formula: see text]wt.% SRA reduces the compressive strength and tensile capacity by about 4–10% at various ages. The [Formula: see text] of concrete added with fly ash, fiber, MgO and SRA is within the range of 2.619–2.796. The frost resistance of concrete correlates linearly with the air void parameters, pore structures and [Formula: see text]. The utilization of fly ash and/or PVA fiber refines and optimizes the pore structure, thus increasing [Formula: see text] and improving the frost resistance. On the contrary, MgO and SRA in this study are less effective in refining the pores than PVA fiber and fly ash, thereby producing smaller [Formula: see text] and relatively weaker frost resistance.