Study on critical crack length of wet-sieved and full-graded concrete under mode I loading

This study quantitatively compares the critical crack lengths of wet-sieved and full-graded concrete obtained from experimental measurements, the numerical simulation, with that from the analytical solution based on the linear elastic fracture mechanics formula (LEFM). The experiments are conducted on wedge-splitting specimens with depths from 200 mm to 1500 mm and a maximum aggregate size of 150 mm. Strain gauges and clip gauges are pasted and mounted along the direction of crack growth to measure the critical crack length. The numerical and analytical methods are used to calculate the critical crack length. The average relative error between the analytical calculations and measurements is still 14%, even if the specimen depth increases to 1500 mm. Additionally, the effective fracture toughness is calculated by combining the peak load and critical crack length, resulting in an average relative error of 17%. These results indicate that the existing analytical method is inadequate for determining the critical crack length. Consequently, a modified analytical method is adopted, utilizing the 95% peak load in the post-peak region and the corresponding crack mouth opening displacement (CMOD), which provides calculated results that agree well with experimental data. Furthermore, the effective fracture toughness can be reasonably derived using the critical crack lengths from the modified analytical method.