Mechanical and microstructural assessments of waste foundry sand in hot mix asphalt

In this paper, it was performed physical, mechanical, and microscopic analyzes on samples of industrial waste foundry sand (WFS) and hot mix asphalt mixtures (HMA) containing WFS as fine aggregate. The HMA was produced replacing 50 and 100 % of the fine aggregate (passing 4.38 mm by sieve) by WFS (by weight) with a dense gradation suitable for pavement course layers. A "control" mixture was used without WFS. The results of typical road engineering tests such as indirect tensile strength (ITS), resilient modulus (MR), modified lottman test (MLT), and four-point bending fatigue test (FTP-4) showed that asphalt mixes containing WFS have mechanical behavior that meets the required criteria to be used as a surface course layer in asphalt pavements. The WFS has physical characteristics very similar to the ones of quarry sands. Optical stereoscope and a scanning electron microscope coupled to an X-ray energy dispersive sensor (SEM/EDS) were used in this research to analyse microstructural characteristics of WFS. Results revealed that WFS has petrographic characteristics that attend usual required criteria, considering low reactivity. These tests also showed that the asphalt binder encapsulated the WFS eliminating the presence of free pathogenic substances. It is concluded that the use of WFS in HMA has technical viability and it is a sustainable alternative for road projects.