Developing resilient modulus model for modified asphalt mixes with crumb rubber and buton natural asphalt based on penetration index and temperature

Resilient modulus is used in the mechanistic analysis of pavement response under dynamic traffic loads, and the evaluation of the material quality is influenced by ambient temperature. This study aims to investigate the effect of hot mix asphalt additives on the resilient modulus (Mr) of crumb rubber (CR) and Buton natural asphalt (BNA)-modified asphalt mixes. Two different HMA additives were used to fabricate HMA specimens. The hot mix asphalt used asphalt Pen 60/70, coarse aggregates, fine aggregates, and filler obtained from the stone crusher machine. The CR is made from scrap tire rubber, in the form of a fine powder through sieve no. 30 (0.6 mm). CR-modified asphalt mixtures were obtained using the wet mixture method, with proportions of 5%, 10%, 15%, and 20% by total weight. BNA was added to the asphalt in proportions of 8%, 10%, and 12% by total weight. The resilient modulus of the specimens prepared having a 100-mm diameter and then compacted with a Marshall hammer. The test data using the indirect tensile test with the Universal Material Testing Apparatus (UMATTA) tool were recorded at temperatures of 25, 30, 35, 40 and 45 °C. The test results indicate that the levels of CR and BNA on the asphalt decreased the penetration rate, increased the bitumen softening point. The addition of the additive has improved the penetration index thus reducing the sensitivity to temperature. The model was developed by a linear relationship between log M_r and asphalt penetration index.