Papers by Author: Ai Min Sha

Abstract: In order to analyze the characteristics of high modulus asphalt mixture dynamic modulus, Universal Testing Machine (UTM-25) was used for dynamic modulus test of three kinds of mixtures, which were PR Module modified asphalt mixture and PR PLAST.S modified asphalt mixture and virgin asphalt mixture, to investigate dynamic modulus and phase angle at different temperatures and frequencies. The results indicate that: the dynamic modulus order of the three asphalt mixtures is PR MODULE > PR PLAST.S > Virgin. PR MODULE asphalt mixture dynamic modulus is much larger than the other two.

Abstract: After cracks appear in the surface layer, the stress mode of pavement structure transits from infinite continuum to limited size board, and the cracks become stress concentration areas. Based on the practical tire contact pressure and contact area, this paper establishes the C3D8R model by ABAQUS, to calculate and analyse the influence on the surface cracks extension from graded gravel transition layer under half-sinusoid load. Analysis shows that the graded gravel has excellent stress dissipation ability. Whether there are cracks in the surface layer, the graded gravel transition layer between asphalt surface layer and semi-rigid base layer could greatly reduce the tensile stresses in the bottom of semi-rigid base and subbase layers, improve the road bearing level, delay and avoid the cracks extension to deep road and prolong the road service life.

Abstract: After cracks appear in the semi-rigid base layer, the stress mode of pavement structure transits from infinite continuum to limited size board, and the cracks become stress concentration areas. Based on the practical tire contact pressure and contact area, this paper establishes the C3D8R model by ABAQUS, to calculate and analyse the influence on the base cracks extension from graded gravel transition layer under half-sinusoid load. Analysis shows that the graded gravel has excellent stress dissipation ability. Whether there are cracks in the base, the graded gravel transition layer between asphalt surface layer and semi-rigid base layer could greatly reduce the tensile stresses in the bottom of semi-rigid base and subbase layers, improve the road bearing level, delay and avoid the cracks extension to deep road and prolong the road service life.

Abstract: This paper mainly presents the study on the properties of cement treated aggregate with different coarse aggregate content. The test specimens which contain 75%, 70%, 65%, 60% and 55% of coarse aggregates were made and the 7d, 28d, and 90d unconfined compressive strengths (UCS), 28d thremal shrinkage coefficient, as well as 90d anti-erosion performance were tested. Results show that with the increase of coarse aggregate, the maximum dry density (MDD)of the cement treated aggregate mixture increased slowly at first to reached the peak value and then decreased rapidly; The optimum moisture content (OMC) declined with the increase of coarse aggregate content; In order to enhance the UCS of cement treated aggregate, coarse aggregate of mixture can be increased to some extent, but too much coarse aggregate will increase the void of the specimen and lead to lower UCS; Increasing the content of coarse aggregate is able to decrease the thermal shrinkage coefficient and erosion quantity of 30 min of the specimens. This is favourable to enhance the cracking resistance and anti-erosion performance of cement treated aggregate base course.

Abstract: Laboratory tests were conducted to evaluate the performance of cement stabilized “skeleton-dense structure” aggregate and conventional “suspended-dense structure” aggregate. In this study, both of the aggregates above were stabilized by cement with different cement content (2%, 3%, 4%, 5% and 6%). Performances of the prepared specimens were studied in terms of compaction property, 7 day unconfined compressive strength (UCS), thermal shrinkage coefficient and 30 min erosion quantity. Results indicated that the maximum dry density of cement stabilized “skeleton-dense structure” aggregate is bigger than that of cement stabilized “suspended-dense structure” aggregate slightly. On the contrary, the optimum moisture content of the former is slightly smaller than that of the latter one. Along with the increase of cement content, the 7 day UCS and thermal shrinkage coefficient of cement stabilized two aggregates were all increase, and 30 min erosion quantity of cement stabilized two aggregates were all decrease. At the same cement content level, the 7 day UCS of cement stabilized “skeleton-dense structure” aggregate is greater than that of cement stabilized “suspended-dense structure” aggregate, and the thermal shrinkage coefficient and erosion quantity in 30 min of the former is smaller than that of the latter.