Laboratory assessment of recycling waste silt as filler in sustainable asphalt concretes for pavements

Due to the modernization of the construction industry, the use of waste is an attractive trend with high potential for many researchers. The majority of the waste materials that are recycled to produce new construction materials are usually by-products obtained from a variety of several manufacturing processes, such as the aggregate washing process. Recycling these materials is of utmost importance since it could reduce the adverse environmental impacts resulting from landfilling. The concept of producing asphalt mixes with waste materials serves as a way to reduce the enormous volume of wastes produced from various sources, which are dumped into lakes or to other water bodies. This study aimed to investigate the feasibility of including silt, a by-product of limestone aggregate production, obtained from S.A.P.A.B.A. s.r.l., as a filler in HMA. Asphalt concrete mixtures are composed of two main components, which are aggregates and binders. Several types of research have shown the importance and the influence of filler in controlling the physical and mechanical properties of HMAs. The main objective of this research is to investigate and assess the effects caused within HMA by using Waste Silt filler. For this purpose, rheological and mechanical tests have been performed on the bituminous mastics and HMAs specimens, respectively. Frequency sweep and multiple stress creep recovery tests of the mastic showed similar behavior of samples produced with untreated and thermally treated waste silt as the filler with those of the control sample produced with common limestone filler. All samples had same resistance against rutting. Moreover, Marshall stability results were used to determine the optimum binder content, which was determined as 5.5% for all mixtures, regardless of filler type used. Finally, the ITS of the HMA mixtures were compared. All in all, the use of Waste Silt as a filler does not negatively affect the performances of HMAs and their bituminous mastics.