Penetration is not only the technical parameters to characterize the soft and hard degree and anti⁃fatigue at medium temperature of asphalt products,but also the classification index of penetration classification system.The research results in the literature show that the logarithm of penetration is correlated with with Celsius temperature.But correlations between the logarithm and double logarithm of penetration with Celsius temperature,reciprocal of absolute temperature,are rarely studied.In order to investigate the correlations among penetration classification system,viscosity classification system and Performance Grade classification system,ten asphalt products produced by two kinds of crude oil were used to study the linear correlations between the logarithm and double logarithm of penetration with Celsius temperature and reciprocal of absolute temperature at 15, 25 and 30 ℃, respectively,as well as the linear correlation between the slope and intercept of these linear correlations.Through the comparison of correlation coefficients of referenced literatures at home and abroad for the past 80 years,it is found that the linear relationship between the logarithm of penetration and Celsius temperature does not represent the optimal linear relationship between penetration and temperature,and the linear correlation between the logarithm of penetration and reciprocal of absolute temperature is better than that between the logarithm of penetration and Celsius temperature.The correlation coefficient between the slope and intercept in the linear equation between the logarithm of penetration and the reciprocal of absolute temperature is higher.It is found that the relationship between penetration and temperature of all asphalt in the previous studies can be expressed by one equation.

The relationship between density and low temperature cracking with the densitytemperature relationship and coefficient of thermal expansion of aggregate,relationship between density and temperature,creep property and temperature,creep property and density was studied. The results show that the density, the Logarithm of the creep stiffness and m value are linear to temperature. The Logarithm of the creep stiffness and m value are all linear to density. The density is closely related with lowtemperature cracking performance.The relationship between density and temperature can be used to evaluate the performance in low temperature condition and the judgment of performance in low temperature is consistent with that from creep property of asphalt. 