Performance Evaluation of Foamed Bitumen Bound Mixtures made with Recycled and Artificial Aggregates and Fibres

The paper describes a research aimed at analysing the performance of mixtures for road base and sub-base layers, made with foamed bitumen, cement, recycled and artificial aggregate as well as different types of fibres, used in order to enhance adhesion and structural properties of the mixes. Reclaimed Asphalt Pavement (RAP), Electric Arc Furnace (EAF) steel slag, foundry sand and fly ash were used in the experiment as alternative secondary aggregates. A control mixture prepared with quarried natural aggregate (limestone) was also studied for comparison purposes. Such Cement-Bitumen Treated Mixtures (CBTM) were manufactured using 70/100 pen foamed bitumen and CEM I 32.5 R Portland cement. Three types of fibres were also alternatively added to the mixtures: structural, polypropylene and cellulose/glass fibres. The comparative mechanical characterization was based on fatigue resistance (EN 12697-24), indirect tensile strength (EN 12697-23) stiffness (EN 12697-26) and water susceptibility (EN 12697-12). The research permitted to recognize the overall positive, but different, contribution of fibres to the performance of mixtures, and define most appropriate fibre content and field of application. Moreover, the contribution of the different waste materials to the structural properties and durability of the studied mixes has been ascertained and new construction solutions have been proposed.