Mechanical Behavior of a Hot-Mix Asphalt with the Addition of Water Treatment Sludge (WTS) for Sustainable Pavement Application

Drinking water treatment plants produce large quantities of Water Treatment Sludge (WTS), which negatively impacts the environment due to improper disposal. In this study, the mechanical performance of a hot-mix asphalt (HMA) containing WTS (referred to as HMA WTS) was evaluated and compared with a control mixture (HMA C), with a primary focus on its potential application in pavements constructed in warm-climate regions. In this way, the implementation of sustainable practices in road construction is promoted. The WTS was physicochemical characterized. Subsequently, the WTS was calcined at 200, 300, 500, and 800 °C to transform it into ash for use as filler (F). A calcination temperature of 500 °C was selected as optimal, based on the evaluation of the physical properties of mastic samples prepared with asphalt cement (AC) and calcined WTS. F/AC ratios of 0.11, 0.25, 0.43, and 0.67 were used, corresponding to filler contents between 0.5% and 2% in the HMA. Based on the stiffness and workability of the asphalt mastic, an F/AC ratio of 0.25 was selected, representing 1.0% filler in the HMA. Two mix designs (HMA C and HMA WTS) were developed according to the Marshall methodology to determine the Optimum Asphalt Content (OAC). Mechanical performance and durability tests were conducted to evaluate the behavior of the asphalt mixtures. The results indicate that WTS increased mastic stiffness, enhancing the mechanical performance of the HMA (greater resistance under monotonic loading and improved rutting and fatigue resistance) while reducing OAC, thus representing a promising alternative for its management and final disposal and contributes to sustainability in pavement engineering. However, durability-related properties (resistance to moisture damage, raveling, and abrasion) decreased due to the reduction in OAC.