Synthetical improvement of dynamic mechanical property and toughness for precast concrete element based on optimization design of composition and curing regime

Abstract

The brittleness and toughening measures of steam-cured concrete are currently less researched aspects. This study focuses on exploring the improvement in the toughness of steam-cured concrete and evaluating its influence on dynamic mechanical properties through a series of macroscopic performance tests. These tests include four-point bending tests, three-point bending fracture tests, uniaxial compression tests, and drop hammer impact tests, all conducted from the perspective of optimizing composition materials and steam curing regimes. The experimental results indicate that, under a relatively short heating time and a prolonged constant temperature curing period, the pure cement steam-cured concrete (S1 group), compared to the S2 group which used 20 % FA and 10 % GGBS to replace cement while also increasing the aggregate content with a modified steam curing regime, exhibited higher strength and elastic modulus but also showed greater brittleness. For example, the damping ratio increased to 0.6–0.7, the flexural-to-compressive strength ratio exceeded 6, and the number of specimens damaged by drop hammer impact significantly decreased, and the notch specimen exhibits lower peak load and displacement during fracture, with generally lower fracture parameter values. The fracture energy of the S2 group is 100–130 N·m-1 higher than that of the S1 group, reaching approximately 670 N·m-1, and the ductility index increased by 0.3–0.4. This research can provide technical support for the high-quality preparation of precast components using steam-cured concrete and offer a theoretical basis for reducing the brittleness of steam-cured concrete.