An investigation on resilient modulus of bituminous mixtures

Abstract

IRC:37-2012 suggests to use resilient modulus as an input parameter in the design of bituminous pavements in India. IRC:37 specifies the values of resilient modulus at different temperatures for Bituminous Concrete (BC) and Dense Bituminous Macadam (DBM) mixes with various grades of unmodified and modified binders. However, IRC:37 recommends identical values of resilient modulus to be used for the mixes, irrespective of the type of modified binder used. At higher temperatures, it can be noticed that IRC:37 tabulated resilient modulus values for the mixes with unmodified binder are higher than those with modified binders. Also, the influence of Poisson’s ratio is not incorporated since a constant value of 0.35 is used for all the mixes. In this investigation, BC mixtures with an unmodified (VG30) and three modified binders (CRMB, plastomer and elastomer) were tested at three different temperatures (25, 30 and 35°C) at 1 Hz frequency. Tests were conducted as per ASTM D7369-11. Samples of diameter 152.4 mm were used for the test. The sample was subjected to 200 cycles, and the last five cycles were used for the computation of Poisson’s ratio and resilient modulus. Both instantaneous and total resilient modulus were computed, and these values were compared with the IRC:37 specified values. The possible reasons for the difference in the modulus values from the present study and IRC:37 are explored.