Laboratory Study of Skid Resistance using Pervious Macadam, Stone Mastic Asphalt and Asphalt Concrete Mixes

One of the effective factors in road safety and accident reduction is to combat road surface slipperiness. The greater the coefficient of friction at the contact patch, the greater will be the degree of vehicle control in bringing it to a halt, thus helping reduce accidents.Asphalt pavements are used extensively throughout the world in general, and in Iran in particular. Thus, in this research hot asphalt mixes (3 types) have been studied for their relative performance in skid resistance. In this research, British Skid Resistance Tester (commonly known as the Pendulum) has been used to evaluate the skid resistance of laboratory made samples and the macrotexture of these surfaces have been measured using the sand-patch technique.In this research, by keeping the aggregate type the same, three types of asphalt mixes that is; pervious macadam, stone mastic asphalt and asphalt concrete are made and evaluated that are different in respect of macrotexture, nominal size, aggregate grading and the percentage of large to small aggregate fractions. Samples made measure 30 x 30 cm with a thickness of 5 cm which are the same as a complete wearing course layer in the field. As asphalt pavements are extensively used in Iran and in the world in addition to mechanical specifications of the asphalt mix the skidding resistance should also be considered. The results show that:1.Among the porous asphalt, SMA asphalt, and the asphalt with continuous grading (concrete asphalt), the porous asphalt is advantageous from the skidding resistance point of view.2.The nominal size of the mix affects the skid resistance of the size, and in the range of 4.75 to 19 mm. nominal size that were studied in this research. The less the nominal size of the mix, the more will be its skid resistance.3.Investigations show that the content of aggregates passed through sieve No. 4.75mm. affects the skid resistance of the nominal size measured by the English pendulum and the skid resistance of the aggregates has a reversed relationship with the aggregates passed thought the same sieve.4.In the asphalt with continuous concrete asphalt grading, the reduced skid resistance between nominal size of 4.75 and 9.5 mm. is not considerable, however it is influential on other parameters like Marshall Stability