| Reinforced concrete members are easy to crack and difficult to control after cracking,which seriously affect the durability and service performance of the structure.High Ductile Concrete(HDC)is a new structural material with high toughness,high crack resistance and high damage resistance.It can effectively change the single cracking mode of traditional cement-based materials,and convert macroscopic harmful cracks into multiple fine and harmless cracks,so as to improving the crack resistance and durability of concrete members.In this paper,the uniaxial tensile properties of HDC and the crack propagation process of HDC beams are studied experimentally.The main contents are as follows:(1)The uniaxial tensile test of HDC was carried out to analyze the influence of water-binder ratio,fiber content,mineral content(mainly mineral powder,limestone powder)and age on the tensile properties of HDC.HDC materials with the same compressive strength grade and different ultimate tensile strain were prepared.The results show that in the range of reasonable water-to-binder ratio and fiber content,increasing the water-to-binder ratio and fiber content are beneficial to enhance the HDC strain hardening performance and increase the HDC ultimate tensile strain.However,the influences of the two factors on the tensile strength are different.With the increase of water-binder ratio,the tensile strength decreases,while with the increase of fiber content,the tensile strength increases;The use of mineral powder to replace part of the cement,HDC early tensile strength decreased,the ultimate tensile strain increased;increasing limestone powder content,HDC ultimate tensile strength and ultimate tensile strain were improved.(2)The bending test of reinforced HDC beam was carried out to study the crack initiation mechanism of reinforced HDC beam and the influence of ultimate tensile strain and reinforcement ratio of HDC on crack width,crack spacing and crack height.The test results show that HDC can effectively reduce the crack width,slow down the crack development and improve the deformation capacity of components.(3)On the basis of the calculation formula of crack width of ordinary reinforced concrete beam,the calculation formula of average crack spacing and maximum crack width of reinforced HDC beam is established by introducing equivalent stress coefficient ? to consider the tensile effect of HDC at the crack,which are proved to be more accurate.At the same time,the contribution of HDC to the crack is calculated based on the test data,and the influence of HDC on the stress,strain inhomogeneity and tension stiffening effect of the steel bar at the crack is analyzed. |
