Improving Quality and Durability of Bitumen and Asphalt Concrete by Modification Using Recycled Polyethylene Based Polymer Composition

Abstract

Bitumen is a component of asphalt binder that combines gravel, sand and mineral powder in the monolith. Bitumen performs this function due to adhesive properties and ability to become liquid when heated, and becomes solid when cooling. At the same thermoplasticity and low strength makes bitumen the most sensitive of all the components of asphalt to the effects of traffic loads and climatic factors. Softening of bitumen at summer temperatures causes rutting on roads and winter fragility results in the occurrence of low-temperature cracking. Modification of bitumen by such polymer additives as thermoelastjplastics of SBS type, latex, terpolymers allows improving bitumen properties and increasing asphalt concrete durability. These additives increase cohesive strength and heat resistance of bitumen, impart elasticity to it, improve its behavior at low temperatures. The main reason that hinders wide application of polymeric modifiers is their high cost. One promising way for solving an issue is partial substitution of expensive modifiers for cheaper plastic waste. In addition, this waste must meet two requirements. Firstly, it should be compatible with bitumen. Secondly, it must provide bitumen with the required positive properties, although maybe not to the extent as special modifiers do. The conducted research showed that so-called recycled polyethylene resulting from the processing of plastic products (films designed for agricultural works, packaging material etc.) meets these requirements. Recycled polyethylene increases viscosity, cohesive strength and heat resistance of bitumen. The conducted studies allowed establishing effective combinations on the basis of recycled polyethylene which ensured significant reduction in the content of expensive special polymer modifiers in bitumen. Ratio of components in the polymer composition is as follows: recycled polyethylene - from 50% to 65%, latex or SBS thermoelastoplastics type - from 30% to 50%, plasticizer (industrial oils, oil extracts, etc.) up to 10%. Rational content is from 3% to 4% by weight of bitumen. The technologies of combining polymer components among themselves and with bitumen were developed. Modification of bitumen by created polymer compositions improved strength and heat resistance characteristics of asphalt concrete and increased its resistance to cracking. Technological parameters of modified bitumen based asphalt mixtures preparation and placing were defined. Modification of asphalt concrete by direct introducing of composite polymer additive in the mix was proposed.