Papers by Author: Zhi Fang

Abstract: Strength standard deviation determines the trial strength of recycled concrete, and it is vital to the mix proportion design and quality control of recycled concrete. But at present the data on the standard deviation for the compressive strength of recycled concrete is very little. On the basis of consulting extensive literatures, related data is summarized, and the values of strength standard deviation of recycled concrete are suggested, which can be for reference in the mix proportion design of recycled concrete.

Abstract: The mix proportion of DSP for the sake of rock anchor grouting has been studied, and the effects of water-binder ratio, volume of nanometer silica added in and various curing methods on the behaviour of the grout have been investigated. Based on the test results, a appropriate proportion of DSP grout with good working and mechanical performance was successfully found.

Abstract: Because there exists a used cement mortar layer outside the recycled aggregate, there are more interfaces inside recycled concrete, which would result in recycled concrete has different properties from ordinary concrete. In this paper, the effect of such key factors for recycled concrete mix ratio as water-cement ratio, cement strength, sand rate, maximum granule diameter and gradation on the properties of concrete with recycled coarse aggregate was studied by experiment, and the some useful suggestion for mix ratio of recycled concrete was provided.

Abstract: Designing the reasonable cross-section and the structural conformation, three Reactive power concrete box piers samples were designed and studied under the constant axial force and reversed horizontal loads. The effect of the reversed horizontal load on the seismic performance of RPC box pier was studied. Such seismic performance as ductility, hysteresis curve, skeleton curve, etc. of RPC box piers is studied by pseudo-static test on three RPC box piers. The simulation results shows that RPC box piers exists excellent performance of resisting seismic force, the direction of horizontal load significant affect that performance, and the performance of resisting seismic force for the pier loaded by the force from main axial direction are better than that from other direction.

Abstract: Ultra High Performance Concrete (UHPC), which has very special properties that are remarkably different to the properties of normal and high performance concrete, is being increasingly used for the construction of structure. In this paper, an experimental program was formulated to investigate the characteristics of complete stress-strain curve of UHPC in uniaxial compression and flexural behaviors of prestressed UHPC beams. The particular focus was the influence of the partial prestress ratio and jacking stress on the flexural response of UHPC beams. The results show that UHPC is of good deformability, and a general form of the serpentine curve is proposed to represent the complete stress-strain relationship of UHPC in compression. The tests of beams demonstrated that the UHPC beams have an excellent behavior in load carrying capacity, crack distribution and deformability, their ultimate deflection can reach 1/34～1/70 of the span. Based on this investigation, theoretical correlations for the prediction structure response of UHPC beam are proposed.

Abstract: The effect of water-cement ratio and curing age on the strength of recycled concrete was studied by experiment with the combination of the recycled coarse aggregate adding natural sand. The results showed that with the increase of curing age, the greater the water-cement ratio is, the smaller the strength growth rate is; the smaller the water-cement ratio is, the greater the strength growth rate is. There is a relatively larger increase in the growth rate of 90d strength than 28d’, which is significantly higher than that of the ordinary concrete. The linear relationship between water-cement ratio and strength of recycled concrete is worse than that of ordinary concrete. Under the same water-cement ratio and curing age, the strength of recycled concrete is lower than that of ordinary concrete, and the empirical formulas between the strength of 28d and 7d, 90d and 28d were obtained.

Abstract: An experimental investigation is reported into the size effect for compressive strength from 36 concrete prism specimens under axial loading and with three different kinds of dimensions of 100×100×300mm, 150×150×300mm, 200×200×400mm. Such parameters as strength grade of concrete and reinforcement ratio are taken into consideration. Three different strength grades of concrete and two different reinforcement ratio are included in those specimens, all tests are undertaken according to ASTM C 39/C 39M-2005. Based on the results obtained, a new size effect law for different kinds of concrete in prismatical compressive strength is suggested and those relative parameters on the size effect are discussed.

Abstract: 81 concrete prism specimens under axial compression were tested to invesgigate the size effect on the axial load stength. Three different kinds of specimens with the dimension 100×100×300mm, 150×150×300mm, 200×200×400mm were tested. The parameters including compressive strength of concrete and aggregate composition are taken into consideration. Three different strength grades of concrete and three different aggregate composition are included in those specimens. The test method are undertaken according to ASTM C 39/C 39M-2005. Based on the test results, a new size effect law for different kinds of concrete in prismatical compressive strength is suggested and those relative parameters on the size effect are discussed.

Abstract: The purpose of present paper is to study the flexural behaviors of concrete T-beams prestressed with external carbon fiber reinforced polymer(CFRP) tendons. Tests were carried out on 5 beams under four-point load, of which four beams were reinforced with hybrid both external CFRP tendons and internal steel rebars and another one only reinforced with internal steel rebars. Such parameters as the different initial loading states at external CFRP tendon jacking and different jacking stress in tendon were considered in experiment. A program was developed to predict the behaviors of those beams prestressed with externally prestressed tendons and the parametric study was conducted using the program. The predicted results from the program were in good agreement with the test results. Such parameters as jacking stress, elastic modulus of external tendons, configuration of deviators and ratio of span to effective depth of beam were chosen as primary analytical factors for the study on the flexural behaviors of beams prestressed with external tendons. The initial loading state on the beam before tendon jacking has no significant influence on the ultimate loading capacity and deflection.

Abstract: An experimental program was formulated to investigate the characteristics of complete stress-strain curve of UHPC in uniaxial compression and flexural behaviors of prestressed UHPC beams. The particular focus was the influence of the partial prestress ratio and jacking stress on the flexural response of UHPC beams. The tests of beams demonstrated that the UHPC beams have an excellent behavior in load carrying capacity, crack distribution and deformability; their ultimate deflection can reach 1/34～1/42 of the span. Based on this investigation, theoretical correlations for the prediction structure response of UHPC beams are proposed.