Enhancing the Performance of a Mixed Recycled Aggregate for Unbound Pavement Layers: Preliminary Study

The construction industry contributes significantly to greenhouse gas emissions as a result of cement production, use of heavy machinery and consumption of large quantity of non-renewable resources. Additionally, the construction industry generates huge amounts of waste. The use of recycled aggregates in road pavements can significantly contribute to more sustainable infrastructures, minimizing the extraction of virgin aggregates and using secondary materials that would otherwise be discharged into the environment with negative impacts. In Portugal, as in most Southern European countries, most of recycled aggregates coming from Construction and Demolition (C&D) waste are mixed or non-selected recycled aggregates, containing concrete and mortars, aggregates, bituminous materials, masonries, among others. These materials are considered as low quality recycled aggregates, due to poor mechanical properties, namely their resistance to fragmentation and to wear, being their use in roadways pavement layers sometimes unfeasible. This paper presents results from a preliminary laboratory study carried out with different mixtures of a recycled aggregate with natural granitic aggregates and focused on the resistance to fragmentation. The behaviour of all the aggregates is also studied, analysing the resistance to fragmentation of different aggregate sizes or fractions. The results show that the performance of the recycled aggregate can be improved, but to comply with the requirements imposed by the Portuguese Road Infrastructures Management Entity, high percentages of natural aggregates with high fragmentation resistance are required.