According to the low temperature disease on asphalt pavement in the areas of cold and large temperature difference between day and night, conventional index test and low temperature bending creep test were used to analyze the influence of diatomite dosage on the low temperature performance of diatomite modified asphalt, and the mixture’s low temperature bending test was applied for verification. Test results show that after diatomite’s addition into asphalt, equivalent brittle point reduces significantly, ductility test cannot estimate low temperature performance very well, stiffness modulus increases and relaxation ability decreases; meanwhile, peak value of stiffness modulus and strain energy of asphalt mixture can be found, the low temperature crack resistance is enhanced; optimum dosage of diatomite is 13%. So, the low temperature performance evaluation method of diatomite modified asphalt mixture through BBR’s low temperature performance evaluation on diatomite modified asphalt remains to be discussed.

The effect of different tempering temperatures on microstructure and impact property of 20CrMnTi steel has been studied on Zwick/roell Amsler PKP 450 pendulum machine, SU-8020 scanning electron microscope (SEM) and optical microscope. The results shows that the impact property of 20CrMnTi steel is dramatically improved after high-temperature tempering. However, the minimum value occurs when it was tempered at 350°C because of low-temperature tempering brittlement at this degree. The SEM fracture morphology was typical dimples after high temperature tempering, and the type of fracture was ductile fracture; the type of cleavage characteristic and quasi cleavage characteristic were generated on the fracture morphology at low-temperature and medium-temperature tempering respectively, and the type of fracture was brittle.