Research On Mechanical Properties And Spalling Behaviours Of FRHPC Subjected To High Temperature And Fire

Recently, high-performance concrete (HPC) is more and more widely used in construction with the development of long-span bridge, tunnel and high-rise building. HPC has been shown to have a number of advantages such as workability, strength and durability. However, it also suffers from two major weaknesses: higher brittleness and lower fire resistance. HPC has been found to be prone to spalling when subjected to high temperature or fire. The addition of fibers is a main means to improve the toughness of HPC and some progresses have also been made in the study on fiber reinforced concrete (FRC), while the investigations on the high temperature and fire resistance properties of fiber reinforced high-performance concrete (FRHPC) are still limited. Based on the project of National Nature Science Foundation of China - Investigation on bearing capacity of fiber reinforced concrete/shotcrete under the repeated high temperature (No. 50278013), the following aspects are carried out in this thesis:(1) In order to estimate the toughness of FRC and to establish Chinese Guideline of FRC, many experiments of flexural toughness for steel fiber reinforced concrete (SFRC) beams are completed according to different international guidelines. Based on test results, the comparisons of different foreign flexural toughness test methods are carried out. It provides basis for the establishment of guideline of FRC in our country.(2) Workability, strength and toughness are significant properties of FRHPC. Based on the investigations on the workability and strength of FRHPC, flexural experiments of HPC reinforced with steel fibers, polypropylene (PP) fiber and hybrid fibers (steel fiber + PP fiber) are carried out according to RILEM. Experimental results show that fibers, especially steel fibers can obviously improve the flexural properties and failure patterns of HPC. In addition, both fiber type and fiber content play important roles in the workability, strength, flexural toughness and fracture energy of HPC.(3) Residual mechanical properties can be used to estimate the high temperature performance for structural materials. The degenerative rules of compressive strength and flexural properties of HPC subjected to high temperatures are investigated from two aspects of material and high temperature. The effects of high temperatures on the flexural failure patterns of FRHPC are analysed. The relationship of compressive strength and temperature acting on HPC are investigated by ultrasonic. Based on SEM test, the relationship between...