Fracture behavior of basalt fiber-reinforced concrete subjected to high temperatures

The three-point bending test was conducted and the digital image correlation (DIC) technique was used to observe the full-field displacement and strain of the notched beam. The initial cracking load and the crack mouth opening displacement were determined based on the deformation field near the tip and mouth of the notch. The initial cracking toughness K-ini and the unstable fracture toughness K-un calculated according to the double-K fracture model, the fracture energy G(F) and the ductility index D-u determined with a modified method, and the equivalent fracture toughness K at four different deformation stages, were analyzed under different temperatures and basalt fiber contents. The results showed that K-ini exhibited a monotonic decrease trend with the increasing temperature, indicating that the notched beam was prone to initial cracking after high temperatures. However, K-ini rose slowly with the increase of the fiber content, suggesting that the basalt fiber had little influence on K-ini. At the temperatures below 400 & DEG;C, the K-un, G(F), D-u, and K at each deformation stage increased with the rise of temperature. At the temperatures above 400 & DEG;C, the K-un, G(F), D-u, and K at each deformation stage apparently decreased with the increase of temperature. Under the current test conditions, the basalt fiber content of 0.4% by volume had the greatest improvement on the fracture performances of concrete after high temperatures.