Use of polymer/Additives in design of flexible pavement to improve strength (to avoid Rutting)

Abstract

An effective road network is absolutely vital to any country’s economy. When the need for paved roads became a worldwide requirement, asphalt very quickly appeared as an ideal binder to build both the pavement structure and wearing course. At low temperatures, asphalt behaves as a stiff material with modulus of resilience (MR) as high as 250,000 psi, where as at high temperatures it looses its MR to 10,000 psi. At ambient temperature, asphalt behaves as viscoelastic material providing both stability and flexibility for long lasting pavements. In regions like Pakistan the ambient temperature often exceeds 50°C and the temperature in the body of the laid asphalt exceeds over 65°C. In Pakistan the traffic comprises of 70 percent to 80 percent of heavy goods vehicles and there is always a tendency of overloading beyond legal axle loads limit due to economic reasons. This coupled with high temperature causes the problem of rutting (permanent deformation) in flexible pavements. By the addition of suitable additives/polymers like lime sulphur, fly ash, thermosetting polymers, thermoplastic rubbers, fibers like glass, asbestos etc, the temperature susceptibility of asphalt can be improved thus reducing the rut potential of asphalt. In view of above, a study to evaluate asphalt cement temperature susceptibility was carried out with/without using additives/polymers at different temperatures using 60/70 grades asphalts cements