In the aim at developing and utilizing ferrous mill tailing resources to save energy, protect environment and develop sustainable society, the experimental study on ferrous mill tailing (FMT) concrete are carried out. The strength grades of concrete used in tests are C30, C35, C40, C45, C50 and C55. Based on the compressive tests, the cubic strength and prism strength of FMT concrete along with their relationship were obtained. Meanwhile, with prism compressive test, the elastic modulus of FMT concrete and its relationship with compressive standard strength also were obtained. The test results show that the ratio of prism compressive strength to cubic compressive strength for FMT concrete is about 0.8-0.9 and the FMT concrete elastic modulus increase with its strength grades.

In the aim at developing and utilizing ferrous mill tailing resources to save energy, protect environment and develop sustainable society, the research of replacing natural sand for ferrous mill tailing into concrete are carried out. Concrete mixed with ferrous mill tailing is called ferrous mill tailing concrete. The study results show the compressive strength of ferrous mill tailing concrete with grade from C20 to C40 is nearly equal to that of common concrete though its dump and divergence decrease little. Through adding in suitable volumes of water reducing mixture, fly ash and slag powder, its workability is improved and satisfies the practical requirement.

To study axial compressive strength of high strength concrete-filled steel tube composite columns, tests of 18 specimens were carried out. Parameters of the specimens were the confinement index of concrete-filled steel tube, the cubic strength and the stirrup characteristic value of concrete outer of steel tube. Test results show that the concrete-filled steel tube and the reinforced concrete deformed simultaneously in the axial direction before and at the peak value of axial compressive force; after failure of the reinforced concrete, the concrete-filled steel tube can still bear the axial load and deformation; the main influential factors of axial compressive capacity are confinement index, the cubic strength and the stirrup characteristic value of concrete outer of steel tube. The accuracy of the formula of axial compressive strength of composite columns provided by CECS 188:2005 is proved by the test results of this paper.

For environmental conservation, resource saving and sustainable development, discarded concrete sources are introduced and current situation of its application is summarized. Then, the facing problems and solutions on concrete-recycling use are analyzed, and recycled application methods of discarded concrete are proposed.

Compressive tests of 30 concrete column specimens with three concrete strength grades are carried out in this paper to study ultimate compressive strength of specimens. The specimens are divided into three groups, that is, unconfined, confined by CFRP with no initial compression and confined by CFRP with various initial compressions. The different initial compressions’ influence on ultimate stresses and strains are investigated. The decrease of CFRP reinforcing effect due to pre-compression are analyzed. The research results provide experimental datum for reinforced design of existing concrete columns.