Laboratory Study on Mechanical Parameters of Foamed Bitumen Mixtures in the Cold Recycling Technology

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 mineral recycled base mixes with foamed bitumen, in which the material from the existing pavement layers was used. The effect of two kind of binding agents (foamed bitumen and Portland cement) was evaluated. The bitumen binder was added to the recycled material in the amount of 2.0% to 3.5%, and hydraulic binder of 1.0% to 2.5% with steps every 0.5%. The effects of different binder materials contents on the air void content, Marshall stability and resilient modulus at temperature 25 °C of the recycled mixes were investigated. Moreover, the detrimental effect of water was measured by comparing indirect tensile strength (soaked and unsoaked) and determine tensile strength retained of foamed bitumen mixtures. The results were subject to the optimization process. This allowed to state that if 2.5% foamed bitumen and 2.0% of Portland cement are used, the recycled base course has the required physical and mechanical properties and moisture resistance.