Properties of asphalt concrete with special paving grade bitumen

Abstract

Residual deformations are one of the most spreaded defects in asphalt concrete pavements caused by an increase in traffic intensity and traffic load. Common ways of reducing the permanent deformations on asphalt concrete pavements is the use of pavements with high content of crushed stone and high-viscosity bituminous binders (bitumen modified with polymers or structuring additives). In the last 30 years, in different countries of the world, the design of high-modulus asphalt concrete pavements (EME, HiMA, HSMS) has become widespread, for which special road bitumen is used - solid and multi-grade. The purpose of the work performed was to study the effect of special road bitumen on the properties of asphalt concrete and to assess the possibility of producing high-modulus asphalt concrete in accordance with national standards requirements. The paper compares the standard and rheological indicators of the quality of high-modulus asphalt concrete with special road bitumen (multi-grade Unibit 35/50 and solid bitumen 20/30 and 35/50) and hot asphalt concrete with the БНД 70/100 bitumen, which is widely used in Ukraine. The asphalt concrete studied in this work has a granulometric composition of stone materials that meet the requirements for the composition of high-modulus mixtures EME 0/20 and the composition of asphalt concrete mixture of type A used in Ukraine with a maximum grain size of 25 mm. Comparison of the properties of asphalt concrete with special bitumen and  БНД 70/100 bitumen confirmed a significant improvement in the properties of asphalt concrete due to the use of special bitumen: the compressive strength at 20 °С increases significantly (by a factor of 1.16 - 1.43 times). Strength at 50°C increases by 1.42 - 1.86 times. Coefficient of long-term water resistance increases to 0.99 - 1.0. Elasticity moduli at 40°C increase by 2.76 times, and at minus 10°C by 1.26 times. The temperature range of plasticity of asphalt concrete significantly expands (up to 100°С on bitumen 20/30). At the same time, for asphalt concrete made on high-viscosity bitumen, an increase in the conditional glass transition temperature is observed, which can lead to a decrease in the crack resistance of asphalt concrete. The use of multi-grade bitumen for the asphalt concrete results in an increase in the physical and mechanical parameters of the quality of asphalt concrete, a decrease in their temperature sensitivity, as well as a decrease in elastic moduli at low temperatures and an increase at high summer temperatures, which leads to an increase in shear resistance and a decrease in fracture resistance.