Mechanical Properties and Meso-Structure of Polypropylene Fiber Reinforced Barite Concrete

The highly crystalline structure of barite aggregate makes it fragile, resulting in poor mechanical properties of barite radiation-proof concrete, which limits its application in buildings with severe radiation such as high-pressure and high-thermonuclear projects. To study the effect of polypropylene fiber incorporation on the mechanical properties of barite concrete, the effects of polypropylene fiber content (0, 3, 6, 9 kg/m³) on the mechanical properties of barite concrete with different strength grades were analyzed, and the size effect of barite concrete cube compressive strength was quantified. The meso-structure of polypropylene fiber barite concrete was studied via SEM test. The results showed that the surface of PR40 fiber was wrapped by a dense hardened cement matrix, which improved the structural strength of the polypropylene fiber-cement matrix, thus improving the splitting tensile strength and flexural strength of barite concrete. With the increase in fiber content, the 28 d compressive strength of the specimens increased by 4.3%-19.6%, and the 28 d flexural and splitting tensile strength increased by 1.8%-25.0% and 4.9%-27.7%, respectively. When the fiber content increased, the cement content could not meet the fiber wrapping, so the compressive strength of barite concrete increased first and then decreased with the increase of fiber contents. The size effect of the compressive strength of barite concrete cubes was gradually significant with the increase of fiber content. Compared with the specimens without fiber, the size effect coefficient η₁₀₀ increased by 0.2%-5.9%, and the size effect coefficient η₂₀₀ increased by 1.8%-5.9%.