A total of ten laboratories in Sweden and Finland took part in a comparative investigation of determining resilient modulus according to the indirect tensile test. Three different types (i.e. makes) of equipment have been used in the investigation: Hydraulic machine, Nottingham Asphalt Tester (NAT), and MATTA (UTM5P) machine. NAT and MATTA are pneumatic machines. Part of the project consists of a literature study. This has been done partly to determine the causes of variations within and between the laboratories when determining the resilient modulus of asphalt pavements. A total of 17 samples from three different mixes were circulated between the laboratories for determining resilient modulus according to FAS Method 454. Ten samples from two of the mixes were produced in the laboratory. Five samples were obtained from drill cores and two dummy samples consisted of Perspex and Teflon respectively. The investigation found that the NAT-equipment indicated a somewhat lower resilient modulus than hydraulic systems and the MATTA-equipment. The NAT-equipment has a longer loading time and measures deformation in a different way compared to the hydraulic equipment and MATTA-equipment when determining resilient modulus. It was also found that the indirect tensile test is a suitable method for routine testing of resilient modulus. When determining the resilient modulus of asphalt pavements, three samples are recommended in the case of laboratory produced material and six samples for drill cores from pavements. (A)
Abstract