Mechanical properties of cement mortar in sodium sulfate and sodium chloride solutions

To investigate the mechanical properties of cement mortar in sodium sulfate and sodium chloride solutions, uniaxial compression test and ultrasonic test were performed. Test results show that the relative dynamic elastic modulus, the mass variation,and the compressive strength of cement mortar increase first, and then decrease with increasing erosion time in sodium sulfate and sodium chloride solutions. The relative dynamic elastic moduli and the compressive strengths of cement mortars with water/cement ratios of 0.55 and 0.65 in sodium sulfate solution are lower than those in sodium chloride solution with the same concentration at the420 th day of immersion. The compressive strength of cement mortar with water/cement ratio of 0.65 is more sensitive to strain rate than that with water/cement ratio of 0.55. In addition, the strain-rate sensitivity of compressive strength of cement mortar will increase under attacks of sodium sulfate or sodium chloride solution.

Hydraulic properties of dune sand-bentonite mixtures of insulation barriers for hazardous waste facilities

The material and elastic properties of rocks are utilized for predicting and evaluating hard rock brittleness using artificial neural networks（ANN）. Herein hard rock brittleness is defined using Yagiz＇method. A predictive model is developed using a comprehensive database compiled from 30 years＇ worth of rock tests at the Earth Mechanics Institute（EMI）, Colorado School of Mines. The model is sensitive to density, elastic properties, and P- and S-wave velocities. The results show that the model is a better predictor of rock brittleness than conventional destructive strength-test based models and multiple regression techniques. While the findings have direct implications on intact rock, the methodology can be extrapolated to rock mass problems in both tunneling and underground mining where rock brittleness is an important control.

Concentration-dependent crystal structure, elastic constants and electronic structure of ZrxTi1-x alloys under high pressure

The physical properties of ZrxTi1-x（x=0.0, 0.33, 0.5, 0.67, 0.75 and 1.00） alloys were sinmlated by virtual crystal approximation （VCA） methods which is generally used for disordered solid solutions modeling. The elastic constant, electronic structure and thermal Equation of state （EOS） of disor- dered ZrxTi1-x alloys under pressure are investigated by plane-wave pseudo-potentia1 method. Our simulations reveal increasement of variations of the calculated equilibrium volumes and decrease- ment of Bulk modulus as a function of the alloy compositions. Lattice parameters a and c of alloys with differentZr concentrations decrease linearly with pressure increasing, but the c/avalues are increasing as pressure increases, indicating no phase transitions under pressure from 0 GPa to 100 GPa. The elastic constants and the Bulk modulus to the Shear modulus ratios （B/G） indicate good ductility of Zr, Zr0.33 Ti0.67 Zr0.5Ti0.5, Zr0.75Ti0.25 and Ti, but the Zr0.67Ti0.33 alloy is brittle under 0 K and 0 GPa. The metallic behavior of these alloys was also proved by analyzing partial and total DOS.