Abstract:
Resilient modulus is an important parameter of hot mix asphalt (HMA) design and analysis of pavement structural response under traffic loading. This research study attempts to characterize different HMA mixtures using resilient modulus test. Four different aggregate gradations of wearing course mixtures including: NHA-A, NHA-B, Superpave and Asphalt Institute’s manual series; each prepared with two different penetration grade bitumen (40/50 and 60/70) were considered. Experimental investigation of various factors: test temperature, load pulse duration, binder type, nominal maximum size of aggregate, specimen diameter and their interaction on the resilient modulus of different HMA mixtures was analyzed. Superpave gyratory compacted specimens were subjected to haversine-shaped wave load pulse with load duration of 100 ms and 300 ms at 25°C and 40°C temperatures using repeated-load indirect test setup in Universal Testing Machine (UTM-25). The resilient modulus values of coarser gradation (NHA-A) was relatively higher amongst the tested gradations. Also, the study found that the size of the specimen statistically affected the measured resilient modulus value as the resilient modulus values obtained for 100mm diameter specimens were higher than those obtained for 150 mm diameter specimens at all testing temperatures. The analysis of two-level full factorial design of experiments revealed that the test temperature was the most significant factor affecting the resilient modulus followed by load duration, bitumen type, nominal maximum aggregate size and specimen diameter. A comparison of resilient modulus with dynamic modulus values from the past research on similar experimental design was carried out in which a strong relation was found between the dynamic modulus values at 5 Hz load frequency with the resilient modulus values at 25°C temperature while at 40°C temperature the resilient modulus values showed a close agreement with that of dynamic modulus values at 1 Hz load frequency.
