To study the influence of steel strands corrosion on the bond behavior for anchoring of pre-tensioned prestressed concrete beams, nine specimens were fabricated. Of which, 5 beams were mixed with salt and set in different places to be corroded in different intensity for 13 months. Then the load test was held to all the 9 specimens and the load-slip curves were obtained. The results show that under the condition of no corrosion crack, the short-term anchoring bond strength of pre-tensioned prestressed concrete beams increases for the steel strands corrosion. Because the tension behavior of steel strands deteriorates remarkably even if the corrosion is slight, which is the dominant cause for the degradation of fundamental structural behavior, the influence of steel strands corrosion on the bond behavior for anchoring may be ignored.

Abstract. Elastic constants and homogenized properties of gypsum structure were investigated by first-principles method. The gypsum (chemical formula of CaSO4•2H2O) is an evaporite mineral and a kind of hydration product of anhydrite (chemical formula: CaSO4). Elastic constants are calculated based on Density Functional Theory (DFT), which can also contribute to provide information for investigate the anisotropy and mechanical properties of gypsum polycrystals. In addition, based on elastic constants (13 independent constants) of the monoclinic crystal, elastic properties of gypsum polycrystals are obtained. The Young's modulus, shear modulus, bulk modulus and Poisson's ration are derived. Therefore, it is fairly meaningful to study the elastic constants to understand the physical, chemical and mechanical properties of gypsum structure. Elastic constants can be used as the measure criterion of the resistance of a crystal to an externally applied stress. The calculated parameters are in excellent agreement with reference by Huang et al..

This paper presents the results of elevated temperatures on the compressive of high fly ash content concrete (HFCC). The specimens were prepared with three different replacements of cement by fly ash 30%, 40% and 50% by mass and the residual compressive strength was tested after exposure to elevated temperature 250, 450, 550 and 650°C and room temperature respectively. The results showed that the compressive strength apparently decreased with the elevated temperature increased. The presence of fly ash was effective for improvement of the relative strength, which was the ratio of residual compressive strength after exposure to elevated temperature and ordinary concrete. The relative compressive strength of fly ash concrete was higher than those of ordinary concrete. Based on the experiments results, the alternating simulation formula to determine the relationship among relative strength, elevated temperature and fly ash replacement is developed by using regression of results, which provides the theoretical basis for the evaluation and repair of HFCC after elevated temperature.

This paper presents the results of the splitting tensile strength of high fly ash content concrete (HFCC) after high temperature and analysis the degraded rules of the residual splitting strength subjected to high temperature and the replacements of cement by fly ash. The specimens were prepared with three different replacements of cement by fly ash 30%, 40% and 50% by mass and were tested after exposure to high temperature 250, 450, 550 and 650°C and room temperature respectively, compared with ordinary Portland cement concrete. The results showed that the splitting tensile strength sensitively decreased with the high temperature increased. Furthermore, the presence of fly ash was effective for improvement of the relative strength. The relative residual splitting strength of fly ash concrete was higher than those of ordinary Portland cement concrete except 30% fly ash replacement. Based on the experiments results, the alternating simulation formula to determine the relationship among relative residual strength, high temperature and fly ash replacement is developed by using regression of results, which provides the theoretical basis for the evaluation and repair of HFCC after high temperature.

The effect of replacement of Portland cement by ground limestone as well as its specific surface Blaine (SSB) on the physical-mechanical properties of fresh and hardened cement paste is studied. The binder was composed of cement and limestone, which was prepared by eight replacement levels of limestone powder (0,5,10,15,20,25,30 and 35%) of binder by mass and four levels of SSB (300,600,800 and 1000 m2/kg). Test results demonstrated that the water requirement of normal consistency and the setting times(initial and final) decreased obviously as the replacement level of limestone powder increased and the extent of reduction was noticeable with the increase of SSB of limestone powder. The compressive strength of mortar incorporating different replacement levels and various SSB of limestone powder increased steadily with ages. The compressive strength decreased with the increase of replacement level of limestone, while as increased with the increase of SSB at the same replacement level and ages. The SSB influence factor was created to describe the effect of SSB of limestone powder on the compressive strength. The strength activity index of limestone powder concerning the replacement levels, SSB of limestone powder and mortar ages was established. The grade of limestone powder was suggested in order to reasonable utilization.