Research On Filtering Concrete-filled Steel Tube With Formwork

Concrete-filled steel tube combines the beneficial qualities of both steel and concrete, namely, high strength, excellent ductility, large energy absorption capacity and convenience of construction. Therefore the use of concrete-filled steel tube has become widespread.But there are still some defects in concrete-filled steel tube, such as waste of resource and energy, environment pollution, needs for extra fireproofing and rust prevention, high maintenance expense, inconvenience of beam-column connections, insufficiency of confinement effect owing to the interface disengaging. Thus a further progress of concrete-filled steel tube is needed.The purpose of this paper is to solve above problems by using the principle of process engineering of materials. By using the principle of process engineering to optimize the factors of concrete and change the resource and energy flow of construction to enhance the performance of workability of concrete-filled steel tube and to meet the requirement of saving the resource and energy, protecting the environment and to conform the stratagem of the sustainable development. High water cement ratio during construction and low water cement ratio during solidification are realized by using electroosmosis technology in the process of concrete construction; the problems such as pollution, poor volume stability and higher cost causing by admixture were resolved; realized the reuse of resource by added large amount of fly ash.Main influencing factors of electroosmosis such as hydration time, current intensity, water cement ratio and quantity of fly ash are analyzed. Relationship between filtering capacity and time is deduced. Design method for mix proportions, which can be used in real engineering, is proposed. The experimental results indicate that electroosmosis technology can further the filtering velocity markedly, increase the compressive strength of concrete significantly and has fine economical efficiency.A new type of composite construction—concrete-filled steel tube with formwork composite construction is studied. Concrete-filled steel tube with formwork composite construction combines the beneficial qualities of both steel and concrete and has unique advantage. Mechanical properties of composite columns subjected to axial compressive loading are investigated.The experimental results indicate that the composite construction has excellent work performance, high strength and good deformation capacity. Owing to the confinement of formwork, the composite columns differ from common concrete-filled steel tube columns which exterior concrete spalls off too early thus lead to the sudden decrease of bearing capacity. After the ultimate strength is reached, the composite columns show a ductile...