Substantiating the Choice and Optimizing the Parameters for the Technology of Hot Recycling of Asphalt Concrete Road Coating

The method of expert assessments has been used to substantiate that the most significant factors that significantly influence the mechanism and kinetics of technological processes of the regenerated mixture preparation are the temperature of its preparation and the content of the regenerating additive. We have investigated their influence on the physical-mechanical parameters of regenerated asphalt concrete, obtained using the technology of hot recycling of asphalt concrete pavement applying the «in place» method. The experimental research has established the dependences of the physical and mechanical parameters (water saturation, compressive strength at 0 °С and 50 °С) of regenerated asphalt concrete on the content of an additive and stirring temperature. The mathematical models have been constructed in the form of second-degree polynomials that describe the dependence of water saturation and strength at the compression of regenerated asphalt concrete on the temperature of preparation and the content of a regenerating additive. It has been established that increasing the stirring temperature increases compressive strength at 0 °С; at the same time, compressive strength at 50 °С and the measure of water saturation decreases. The increase in the regenerating additive reduces all the examined physical and mechanical indicators. Based on an analysis of the results obtained, we have determined the regions of rational values of the stirring temperature of loose asphalt-concrete crumbs (125‒135) °С, as well as the content of an additive (0.26‒0.28) %, when preparing hot asphalt concrete mixture. In terms of physical-technical indicators, the resulting mixture meets the requirements set by DSTU B V.2.7-119:2011 «Asphalt concrete mixes and road and airfield asphalt concrete. Technical specifications» for hot fine-grained asphalt mixtures. The reported results could prove useful when devising a technology of hot recycling of asphalt concrete pavement by the «in place» method and for studies related to its improvement