Optimization of Fracture Toughness Testing Method for Small-sized Cement Paste Specimens

In the study of cement-based materials, cement paste plays a decisive role in determining macroscopic material behavior. However, traditional large specimens face challenges such as high material consumption and low preparation efficiency when special additives or precise gradation control is required. To address this, an accurate fracture toughness test for small-sized cement paste specimens was developed. By systematically investigating the effects of pre-crack depth, support span, and loading rate, an optimized testing protocol was established using a precision three-point bending setup. Key issues such as randomness in fracture paths were resolved through segmented linear processing of load-displacement curves, significantly improving reliability. Results show that with a pre-crack depth of 35% of specimen thickness, a span of 100 mm, and a loading rate of 0.1 mm/min, the coefficients of variation for fracture toughness and fracture energy are within 2%/4%. Compared to conventional methods, this approach reduces specimen size by about 70%, greatly lowers material consumption, and provides an effective means for rapid performance evaluation of specially proportioned materials. It offers valuable application in new material development and performance assessment of specialty engineering materials, supporting the refined design of cement-based materials.