Studies on fatigue performance of modified dense bituminous macadam mix using nano silica as an additive

Abstract

In this project work, organized study was carried out to evaluate the fatigue performance of dense bituminous macadam (DBM) mix using nano silica as an additive and the results were compared with the conventional DBM mix. For this purpose, Marshall stability and indirect tensile strength (ITS) tests were conducted to find out optimum bitumen content, optimum nano silica content and tensile strength of the mix. Repeated load fatigue test was carried out for DBM mix with and without nano silica at different failure loading or stress level which was obtained from ITS test. The nano silica modified DBM mixes shows higher fatigue life across all failure loading compared to conventional DBM mix. Also, it was seen that the increase in failure loading resulted in decrease of number of fatigue cycles and increase in the initial tensile strain of the mix. The DBM mix with 4% (optimum) nano silica shows 1.85, 1.67, 1.74, 2.16 and 1.98 times higher resilient modulus when compared to conventional DBM mix at 10%, 20%, 30%, 40% and 50% failure load respectively. Fatigue line constants were calculated for both conventional and nano silica modified DBM mixes and the values were comparable with the literature.