Papers by Author: Jun Liu

Abstract: The main research methods to predict and research wind loads on buildings at home and abroad include wind tunnel tests, field measurement and numerical simulation. However, the wind tunnel tests and field measurement require big funds, long cycle and complicated measurement. Moreover, numerical simulation technology is quite mature. In this paper, based on fluid dynamics software CFD and criteria Reynolds k-ε turbulence model, wind field of the village flat roof with parapet is studied using the numerical simulation technology. Furthermore, the wind pressure data in different wind angles are processed and analyzed. The results show that wind angle has a significant impact on the wind pressure and its distribution. When the wind angle is 0 °, the air pressure-fluctuation in each node of the roof is small, and the pressure coefficient is steady between -1.50 and -2.00. When the wind angle is 45 °, the air pressure fluctuation in each node of the roof is large, and the pressure coefficient fluctuates between -0.8 and -3.0. When the wind angle is 90 °, the wind pressure-fluctuation in each node of the roof is equal to the fluctuation between 0 ° and 45 °wind direction angle, and the wind pressure coefficient fluctuates between -0.7 and -1.7. When incoming flow is along the asymmetric axis, the wind pressure-fluctuation is large, and the wind pressure is greater than that in the large negative pressure zone which is along the symmetry axis, which can bring serious damage on the roof.

Abstract: Abstract. For the slow process of hydration and complex process of hydration of cement-based composite biomass materials, the paper study the compatibility of straw cement mixed system was evaluated in process of hydration. By testing temperature changes in process of hydration of cement-based composite biomass materials and analyzing the maximum value of hydration temperature, the maximum temperature difference and compatibility coefficient of modified the cement-based composite biomass materials by agent, taken before or after that. It was evaluated that compatibility performance of modified the cement-based composite biomass materials by agent. The results show that the characteristic changes of early hydration heat was reflected with a visual aid by some indexes that are the maximum value of hydration temperature, the maximum temperature difference, and so on. And the early hydration behavior was more comprehensive objective reflected by compatibility coefficient in cement-based composite biomass materials. At the same time, the modified effect of sodium silicate was superior to the polyvinyl acetate (PVAc) in the early hydration of the cement-based composite biomass materials.

Abstract: Through using acetic acid resin, asphalt and urea resin organic pretreatment methods to pretreat the surface of rural construction waste, and testing of crush index and water absorption rate of recycled coarse aggregate after pretreatment, the research for the influence of organic pretreatment technology on physical and mechanical performance of recycled coarse aggregate. The results prove that organic infiltrating pretreatment technology can effectively enhance the density of the coarse aggregate and decrease the crush of recycled coarse aggregate index, in a certain extent. The crush index of recycled coarse aggregates after organic pretreatment decreases at almost 17.63%, what’s more, organic pretreatment technology can decrease the water absorption rate of coarse aggregate by a large margin. The water absorption rate of coarse aggregate can be reduced to a minimum of 2.03% which closes to the level of natural aggregates. Because of urea resin solidified into film at fast speed, high integrity and high wear resistance, and relatively cheap, urea resin’s pretreatment effects on recycled coarse aggregates is better than acetic acid resin and asphalt.

Abstract: This study presents the impact of rice straw as additive material on physical properties of hollow block as compressive, flexural strength and water absorption, Softening coefficient. Through testing the hollow block physical properties, the of rice straw additive was studied. When the rice straw amount portion was 0~15%, with rice straw amount portion increased, compressive, flexural strength and water resistance effect of adding one kind of early strength agent and mixing Al2(SO4)3, CaCl2 early strength agent hollow block decreased gradually. When the rice straw amount portion was 10%, adding early strength agent Al2(SO4)3, CaCl2 ，the 28d compressive strength of hollow block was minimum, 3.5MPa; while mixing CaCl2, Al2(SO4)3 early strength agent, the hollow block softening coefficient was 0.76, water absorption rate was 3.9%, meet the requirements of national standard of common concrete hollow block. Through the experiment, the conclusion is mixing early strength agent Al2(SO4)3, CaCl2, Obviously superior to adding one kind of —early strength agent—Al2(SO4)3 or CaCl2 on the physical properties of hollow block.