Study on the Mechanical Properties and Microstructure of Fiber-Reinforced Concrete Subjected to Sulfate Erosion

It is of great significance to overall evaluate the degree and process of sulfate erosion on concrete, especially for the fiber-reinforced concrete (FRC). This paper investigated the effect of steel fiber (SF), polypropylene fiber (PPF), and basalt fiber (BF) on the mechanical properties and microstructure of concrete exposed to sulfate erosion. The compressive strength, mass change rate, and scanning electron microscope (SEM) images of the steel fiber-reinforced concrete (SFRC), polypropylene fiber-reinforced concrete (PPFRC), and basalt fiber-reinforced concrete (BFRC) were obtained. The results revealed that the sodium solution concentration affected the compressive strength and relative elasticity modulus of concrete, the compressive strength and relative elasticity modulus diminished with the erosion concentration increased. Further, for the FRC, there was an optimum fiber content for the compressive strength of concretes to resist sulfate erosion, whereby the optimum fiber contents for the SFRC, PPFRC, and BFRC were 3.0%, 1.0‰ and 0.5‰, respectively. Moreover, the mass change rates for the PPFRC were lower than those for the BFRC, while being higher than those for the SFRC. The mass change rate of PPFRC exposed to sulfate erosion concentrations of 3%, 5% and 7% could be divided into three stages, i.e., decreasing stage with the mass change rate below zero, increasing stage with the pores of concretes filling by some expansion products, and declining stage with some mortar peeling out. Additionally, the number and shape of expansion products increased with the erosion age and sulfate solution concentration, together with the depth and width of cracks in concrete.