Application of recycled aggregates to the road base mixtures with foamed bitumen in the cold recycling technology

Abstract

To reduce the energy consumption and CO2 emissions during asphalt production, several environmentally friendly technologies have been developed during the last years. One of these technologies is the cold recycling by using foamed bitumen. Foaming the bitumen reduces the binder viscosity temporarily and increases the volume as well. Homogenous foams are produced by injection of cold water into hot bitumen. The paper presents the results of laboratory testing of the physical and mechanical parameters of the recycled material using the foamed bitumen and resistance to the action of water. The tests were performed on the road base mixtures incorporating reclaimed asphalt pavement (RAP) with foamed bitumen. The aim of the tests was to evaluate the properties of the mixes in terms of the recycled aggregates. The mixes included aggregates from the recycling of the crushed stone base layer and from the crushed concrete rubble. The effects of the type of recycled aggregate and amount of foamed bitumen on the air void content, Marshall stability and flow of the recycled mixtures were investigated. Indirect tensile stiffness modulus (ITSM) was determined at temperature 25 °C. Moreover, the detrimental effect of water was measured by comparing indirect tensile strength (ITS soaked and unsoaked) and determine tensile strength retained (TSR) of bitumen stabilized materials. The analysis of the test results allowed to state that if 2.5% foamed bitumen and 2.0% of Portland cement are used, the recycled road base had the required physical and mechanical properties and moisture resistance.