Improvement of Cracking-resistance and Flexural Behavior of Cement-based Materials by Addition of Rubber Particles

By ring test and bend test, the improvement of waste tire rubber particles on the crack- resistance and flexural behaviors of cement-based materials were investigated. Test results show that the cracking time of the ring specimens can be retarded by the incorporation of rubber particles in the cement paste and mortar. The improvement in the crack-resistance depended on the rubber fraction. When the rubber fraction was 20% in volume, the cracking time was retarded about 15 h for the paste and 24 d for the mortar respectively. Flexural properties were evaluated based on the bend test results for both mortar and concrete containing different amount of rubber particles. Test results show that rubberized mortar and concrete specimens exhibit ductile failure and significant deformation before fracture. The ultimate deformations of both mortar and concrete specimen increase more than 2-4 times than control specimens.

Mutagenic Effects of Plasma Implantation on Scion of Jujube Tree

[ Objective ] This study aimed to explore and master the plasma implantation mutagenesis technology for jujube scion and find a new way to breed crack- ing-resistant fruit materials of jujube with ideal comprehensive characteristics. [ Method] A new technical means of plasma implantation mutagenesis was adopted for mutagenic treatment of famous jujube varieties Chun Date and Huping Date by implantation with nitrogen and argon plasma; subsequent grafting investigation was conducted. [ Result] The results showed that both nitrogen and argon plasma implantation could lead to mutation. With the same implantation dose, the mutation rate of jujube samples treated with argon plasma was significantly higher than nitrogen plasma; favorable mutations were mostly in jujube samples treated with argon plasma. Based on the grafting survival rate and mutation rate of jujube samples treated by plasma implantation, the optimal implantation dose of nitrogen and argon plasma for jujube scion was determined as （6 × 10^16 -8 × 10^16 ）/cm2 （number of ions per square centimeter）, the optimal implantation rate was 10 mA× 28 kV, and the optimal pulse intermittent duty cycle was 60%. According to survey results, jujube scion after mutagenic treatment with plasma implantation had a wide range of mutations in the growth rate, flowering and fruit-setting, leaf shape, fruit shape and growth period （maturity）. After four years of consecutive trials, a high-yield material with high fruit-setting rate and low fruit-cracking rate and two significantly cracking-resistant materials with growth period postponed by 10 - 15 d were obtained. [ Conclusion] This study provided new variant materials with cracking resistance and ideal comprehensive characteristics and explored new ways for the prevention and control of major disasters in jujube industry