The Effect of Sand and Cement Mixture Percentage on the Performance of Semi-Rigid Porous Asphalt with Different Gradation

Semi-rigid asphalt, or porous asphalt impregnated with cement or cement mortar and quicksand is an asphalt mixture with a very low fine grain and a high porosity percentage (about 20%) that is filled with cement and quicksand mortar. This type of asphalt is a flexible and durable mixture and a suitable procedure in terms of providing friction and reducing noise for road surfaces. Using the appropriate percentage of bitumen in the mixture, it can be used in areas with different temperatures. Semi-rigid asphalt is less susceptive to heat than conventional asphalt concrete. To evaluate this type of mixture, samples of a porous asphalt mixture with different percentages of cement-sand slurry (0%, 25%, 50% and 75%) were impregnated and Marshall resistance tests, dynamic creep, resilience coefficient, fatigue and moisture susceptibility was performed on them. The results show that on average, with increasing the percentage of cement-sand slurry in semi-rigid pavement, moisture susceptibility, fatigue and creep decreases by ،5%, 8% and 12%, respectively, and the Marshall resistance parameters and resilience coefficient increase by 8% and 33%, respectively. Also, with increasing the percentage of cement sand slurry in semi-rigid pavement, the amount of water and fluid absorption decreases and the amount of actual specific gravity of the sample increases. In fact, it can be said that the percentage of cement sand slurry in semi-rigid pavements is a very effective parameter on the performance of this pavement. In addition, the results show that by converting flexible asphalt pavement to semi-rigid pavement by injection of cement-sand slurry in porous asphalt cavities with granulation and optimal bitumen percentage (C granulation and 4% bitumen), respectively, the resilience modulus parameters, fatigue, creep, moisture susceptibility and Marshall resistance improved by approximately 5%, 62%, 60%, 167 and 21%; Therefore, by converting flexible pavement to semi-rigid pavement, performance parameters are improved.