DEVELOPMENT OF PUMPING HPSFRC FOR ANCHORAGE ZONE BETWEEN STEEL ANCHORAGE BOX AND CABLE IN BRIDGE TOWER

The usual fiber concrete is not widely used in high bridge tower due to bad pumping performance.Experiments were concentrated on pumpability,plastic shrinkage and drying shrinkage of the anchorage concrete.Based on the advanced multi-compound technique,the fiber concrete mix design was modified to ensure good pumpability.The effect of hot weather conditions on plastic shrinkage cracking of high performance concrete(HPC) and special high performance steel fiber-reinforced concrete(HPSFRC) have been analysised by the method of artificial imitation in the lab.The effect of fiber content and shrinkage-reducing agent(SRA) on plastic shrinkage cracking and drying shrinkage of HPC was also investigated.In the end,influence mechanisms have been explained.After 2 hours out of the machine,HPSFRC with the optimal mix proportion has good pumpability.The experimental results show that with the increase of content of fiber used in HPC,the total areas of plastic cracking decrease and the concrete anti-cracking grade improves.For HPC in which volume fraction of steel fibers is 0.8%,the free drying shrinkage could be diminished by about 50% in 90 days and the restrained drying shrinkage cracking could be avioded thoroughly within 66 days after casting,and accordingly reduce the cracking risk of concrete,and result in higher durability in anchorage zone.The test results also show that when 0.6% volume fraction of steel fibers together 1.5% SRA(by weight of cementitious material) are added into HPC,plastic shrinkage cracking and free drying shrinkage diminished obviously at early age.Furthermore,compared with the same strength of HPC,the experimental results indicate the addition of steel fiber improves the long term mechanical properties of HPC,especially the bending strength and splitting strength improve by 30%.