Research And Development On The Green Super High Strength Concrete Used Stone-chip, And Experimental Studies On Its Mechanical Properties And Anti-fire Performance

Being higher with the specific strength, and lower with the consumption of natural resource and the cost in their life cycle, Reactive Powder Concrete as the representative of green super high strength concrete is of a promising application and has become the focus of research and application on the modern concrete. However, raw materials being expensive and scarce, as well as complicated process technologies, RPC is limited in engineering practice. On the support by the Natural Science Foundation of Fujian Province of China (No.2011J01327,2007J0163) and the Scientific and Technological Planning of Putian of Fujian Province (No.2007G26), the dissertation has concentrated on tackling deal with the technological difficult problems concerning applying RPC to practice through experiment studies combined with theoretical analysis, and has achieved a few of creative works as following:(1) Based on The experimental studies on the mix technology of green super high strength concrete used local materials, it is shown that it is possible for us to make up the new type of environmentally friendly concrete, i.e., super-high strength concrete, with the strength being as high as137.3MPa by means of the general technical process with the cheap local materials, and at the lower consumption of ordinary Portland cement of350kg/m3. It was found that within the factor scope of this test, specific strength of per unit cement of Green Super high strength concrete used Stone-chip (abbreviated to GSHSCUS) was about4.17times as high as that of ordinary concrete, and2.49times that of HSC, and2.02times that of RPC.It was found that both GSHSCUS and Polypropylene fiber reinforced super high strength concrete used stone-chip (abbreviated to PFRSHSCUS) shew excellent perfomance on the self-shrinkage, and it is possible to eliminate the disengaging at interface of steel and the core concrete by filling GSHSCUS or PFRSHSCUS with the reduced consumption of cement.(2) A series of experiments on the fire behavior of GSHSCUS with the two different parameters including temperature and fiber type were carried out in the laboratory, experimental results show that, GSHSCUS without fiber has a weak refractory performance as well as GSHSCUS mixed with the steel fiber, with being about400℃of cracking temperature, and that GSHSCUS mixed with polypropylene fiber exhibits excellent resistance to high temperature, and that after the high temperature all of them show distinguished characteristic different from that of ordinary concrete, HSC or HPC, namely the strength of GSHSCUS without fiber increases with the elevated temperature under360℃at which strength was as high as1.47times of that at room temperature, and GSHSCUS mixed with the polypropylene fiber show slowing growth of strength by400℃at which strength was1.07times of that at room temperature, then keeps declining. Also analyzed is the mechanism of the strength changing with elevated temperature.(3) Based on the experimental studies of14short steel tubular columns filled with GSHSCUS and19with PFRGSHSCUS, it is found that within the factor scope of these tests, both the confinement index and the concrete strength of the specimens have great influence on their features of specimen subjected to axial load. Experiment results show that the load&average strain curves of the specimens might be divided into four stages:elastic deformation process, elastic-plastic deformation process, the descent process and the recovery process of its carrying capacity, and that specimens with the lower confinement index exhibits a rapid softening process in the post-peak region with a towering peak and a shorter incremental portion plus the weak recovery in the forth stage, while specimens with the higher confinement index exhibits a gradual softening process in the post-peak region with a chubby curve and a longer incremental portion plus the strong momentum of recovery in the forth stage. The experimental phenomena indicate that all specimens are typical of the higher residual load capacity and excellent ductility. Then the formula of its ultimate load capacity was built by regression based on experimental results at the end, by which the calculated results have a good coincidence with those from the experiments.(4) Composition columns reinforced with the prefabricated GSHSCUS filled with steel tubes was put forward, and based on the experimental studies on the12short composition columns reinforced with the prefabricated GSHSCUS filled with steel tubes with1RC as reference. The experimental parameters were the concrete type inner steel tubes, and L/D ratio, steel ratio and so on. Experiment results show that mechanical properties of composition columns reinforced with the prefabricated GSHSCUS filled with steel tubes is superior to that of RC columns, with the higher residual load capacity and excellent ductility with ultimate strain being1.86～8.29times that of RC columns. Then the hypothesis was put forward based on experimental phenomena observed, and the formula of its ultimate load capacity was suggested based on superposition method, by which the predicted values have a good coincidence with those from the experiments.(5) Based on the experimental studies of12GSHSCUS filled with steel tubes short columns, it was found that within the factor scope of this test, the load&average strain curves of the specimens may be divided into four stages:elastic deformation, elastic-plastic deformation, the descent process and the recovery process of its carrying capacity, which is similar to that at room temperature, but elastic deformation stage was shorter with the lower stiffness and the ratio of elastic limiting load to ultimate load being lower, and with the peak strain increasing and the maximum strain decreased.