No abstract

In order to clear the shear mechanism of the scrap tire strips reinforced brick powder, a series of large-scale direct shear tests were carried out on the pure brick powder and reinforced brick powder. The scrap tire strips with 50 mm in length, 5 mm in thickness, and 10 mm, 30 mm, and 50 mm in width were put into the brick powder with volume percentages of 2%, 6%, and 10% as reinforcement, respectively. The results show that the internal friction angle and cohesion increase by adding scrap tire strips into brick powder. The peak shear strength of reinforced brick powder initially decreases, thereafter increases and finally decreases with the increase of volume percentage of the scrap tire strips. And the peak shear strength increases in the initial stage and then decreases with the increase of the scrap tire strips dimension. The optimal dimension and volume percentage of the scrap tire strips are 50 mm × 30 mm × 5 mm and 6%, respectively. In addition, the scrap tire strips provide constraints to restrict the vertical displacement of integral reinforced brick powder, and relative to the pure brick powder, the larger the vertical load is, the greater the decrease of vertical displacement is.

Color blended rotor spun yarn mixing with different methods were spun. Three blending methods were used, one passage of drawing, three passages of drawing and rovings during multi-channel spinning. Multi-channel spinning is modified on rotor spinning machine, which is implemented by a novel mechanical system specially designed to incorporate three separate feed rollers side by side and controlled by servo motors with PLC. Using this new method, blend ratio of yarn can be controlled and realized by asynchronous drafted rovings. 37 type of color blend yarn were produced with different blending ratios. And each yarn was intercepted with 5 cross sections and a total of 185 cross-sectional images were taken. Hamilton index of different colored fibers were calculated of the each type of yarns. And sum of absolute values of Hamilton index were got to demonstrated fibers blending effect in yarns cross sections. All the Hamilton index of the yarns prepared by the three above mentioned methods were all around 5, much below 20. The results showed that regardless of blending method used, the blending effects of rotor spun yarns were all very good.

Different kinds of hemihydrate calcium sulfate whiskers were fabricated by calcination method under the condition of 115-600 °C. And the density, moisture rate and mechanical properties of composites of gypsum and whisker were studied. The specific strength of composites was investigated. The results show that gypsum boards with whisker calcined at 115 °C and 300 °C have the maximum and minimum densities, which are about 1658 kg/m3 and 1604 kg/m3, respectively. Hydration ability of anhydrous calcium sulfate whisker is the strongest. The values of specific strength of gypsum board reinforced by different types of whiskers suggested that the porosity of the composites changed with the different kinds of whiskers, which agreed well with the moisture rate and mechanical properties.