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

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 + fiber) > fiber > fly ash > MgO > SRA. The incorporation of 0.8kg/m(3) polyvinyl alcohol (PVA) fiber and 20wt.% fly ash together enhances the compressive strength and tensile capacity of concrete by 6-7% at the late age, whereas the addition of 6wt.% MgO or 1wt.% SRA reduces the compressive strength and tensile capacity by about 4-10% at various ages. The Ds 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 Ds. The utilization of fly ash and/or PVA fiber refines and optimizes the pore structure, thus increasing Ds 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 Ds and relatively weaker frost resistance.

Automated summary

This study investigates the improvement of frost resistance of face slab concrete by adding fly ash, fiber, MgO, and shrinkage-reducing admixtures. The results suggest that the combination of PVA fiber and fly ash enhances compressive strength and tensile capacity, while MgO and SRA have a negative impact on the mechanical properties of concrete. Additionally, the frost resistance of concrete is closely related to air void parameters, pore structures, and Ds values.