Physical properties of asphalt modified with polyethylene-co-methyl acrylate and acids

Abstract

Asphalt was modified with polyethylene-co-methyacrylate in the range of 2-8 wt% and various kinds of acid: polyphosphoric acid, phosphoric acid and citric acid, in 1, 2 and 3 wt%, using mixing temperature of 170C for 2 h. It was found that when comparing the physical properties of these modified asphalts with those of asphalt modified with styrene-butadiene-styrene (4 wt%) as reference material, some properties of the asphalt modified with 4 wt% polymer: penetration, softening point, penetration index and complex modulus are similar to those of the reference material. When polyphosphoric acid, phosphoric acid and citric acid was added in the amount of 1, 2 or 3 wt%, penetration value, variation of softening point and storage stability were decreased. These demonstrated the increase in strength and compatibility of the modified asphalts. The separation during storage between polymer and asphalt was decreased. The increase in softening point showed thatthe modified asphalt was less sensitive to the temperature change. In addition, the dynamic viscosity was found to increase, but not over 3000 centipoise. This makes the material easy to mix for use. The elastic recovery and complex modulus were increased, indicating the resistance in deformation due to the rutting and cracking from traffic loading. The change in physical properties resulted from the interaction between acid and aromatic ring of asphaltene: hydrogen bonding and dipole-dipole interaction. These resulted in the increase in molecular size of asphaltene. Different type of acid has different result. It was found that the efficiency of acid in improving polyethylene-co-methyacrylate asphalts properties are in the order of polyphosphoric acid > phosphoric acid > citric acid