In addition to monitoring skid resistance, texture depth, and tire-pavement noise testing over time, monitoring the overall performance of the HFS system over time provides valuable information on the durability of the material. While HFS product performance tests are still maturing in the U.S., the British Board of Agrement HAPAS process includes a number of simulative and conditioning tests for HFS products. Some of these tests are performed on the finished product in-situ, and others are performed in the laboratory on core samples removed from the finished product.
In addition to skid resistance and texture depth testing, on-site performance tests include:
- Erosion Index – Examination of the HFS surface used to quantify the degree of erosion of the material.
- Overall System Loss – Visual evaluation for overall system loss, including loss of aggregate or wearing away or delamination of the system from the underlying pavement surface.
- Cracking – Used to identify cracking (greater than 0.5 mm in width) in the HFS system.
Additional laboratory “torture” tests of HFS systems are also conducted to evaluate the durability of the products. These tests include:
- Scuffing – Used to determine the resistance to wear by scuffing a sample of the HFS at an elevated temperature. This is an accelerated loading test using a pneumatic tire to simulate actual traffic loading.
- Wear – Used to determine the resistance to wear under repeated turing wheels at a low temperature. This accelerated loading test simulates wear of the HFS under traffic turning movements.
- Tensile Adhesion – Used to evaluate the bond between the HFS system and the underlying pavement surface.
- Heat Aging – Used to determine what effect heat aging has on the performance of the HFS system – used in conjunction with the Scuffing Test.
- Freeze-Thaw Conditioning – Used to determine what effect exposure to freeze-thaw cycles has on the performance of the HFS system.
- Diesel Susceptibility – Used to determine the extent to which exposure to diesel fuel has a deleterious effect on the HFS system performance.
- Thermal Movement – Used to determine the thermal expansion coefficient of the HFS system.