Effect of the filler particle size on the low and high temperature performance in asphalt mastic and concrete

Restrained cooling, time-to-failure and triaxial tests were performed on mastics and both dense and gap-graded asphalt mixtures prepared with two different fillers. Coarse and fine fillers produced from the same limestone quarry were used to produce mastics and mixtures with varying amounts of filler. Aggregate fractions were proportioned to give nearly identical gradations above the 63-micron screen but intentionally different gradations below the 63-micron screen. Little variation in thermal stress response or time to failure was found between samples with different gradations in both mastic and mixture restrained cooling tests. Failure stresses and temperatures were identical for different mastics and mixtures, despite the large differences in fines gradations. These results lend indirect support to the view that the crack pinning theory as originally proposed by Evans is relevant to the low-temperature failure of asphalt mastics and mixtures. The theory predicts that only the volume fraction of particles, not the particle size, influences fracture properties. Triaxial tests on the asphalt mixtures revealed very significant differences in deformation characteristics according to the composition and gradation of the aggregate. Mixtures produced with coarse filler and less natural sand were found to have nearly 50 percent less permanent deformation than those with fine filler and more natural sand. This observation can be explained due to the presence of gaps and the lower amount of natural sand in the mixture made with coarse filler.