## 1 Introduction  
Asphalt mixtures (AM) are the most used construction material for flexible road pavements worldwide; they are designed to withstand traffic loading, ageing, and water damage [1]. Such mixtures of coarse aggregates, sand, and bitumen are integrated by mineral filler, which leads to porosity reduction and bitumen stiffening, resulting in improvement of mechanical response against rutting and showing [2; 3; 4; 5; 6; 7]; however, overdoses of mineral filler reduce the aggregate content, and a reduction in strength is observed [8]. The effective utilization of various mineral fillers such as lime [9], hydrated lime [10], limestone powder [11], fly ash [12] and cement [13] to improve the strength of asphalt mixtures has been investigated in various studies. In particular, Portland cement has demonstrated better effectiveness as a filler material [14]; however, on account of high CO\({}_{2}\) emissions associated with cement manufacturing, researchers are constantly looking for alternate environment-friendly filler materials [15]. Silica fume (microsilica), an industrial waste product, has an adverse impact on the environment if not disposed of safely; it is an extremely fine silica nanocrystalline polymorph formed as a by-product of silicon and ferrosilicon alloy processing in electric arc furnaces (EAFs). Silica fume (SF) has been used in the concrete industries to improve compressive strength, hardening of concrete, and as a partial replacement for cement [16; 17; 18; 19]. In fact, the material is involved in the pozzolanic reaction with the calcium hydroxide crystals, producing additional cementing material (C-S-H) and eliminating areas of stress concentrations prone to failure initiation [17; 20; 21; 22]. Furthermore, SF is used in road pavement subgrade to reduce swelling pressure and increase the bearing capacity of the pavement'ssubgrade [23; 24; 25]; however, a minimal investigation in necessary to study the use of this material as filler in AM. [PERSON] et al. investigated the effect of silica fume as mineral filler additive with waste fly ash on the indirect tensile strength of AM [26]. The study revealed that the addition of SF enhances the initial mechanical properties, long-term performance, and durability. [PERSON] and [PERSON] et al. studied the application of silica fume (0.25-1.0%) to improve the rheological properties and to reduce the oxidation rate of the asphalt binder [27; 28]. [PERSON] et al. carried out experimental work to quantify the effect of SF on various mechanical properties of asphalt concrete [29]. The effect of SF on the mechanical strength of reclaimed asphalt concrete was investigated by [PERSON] et al. [30]. [PERSON] et al. reported that silica fume can effectively improve the mechanical and rheological properties of asphalt concrete and can be used as an alternative filler material [31]. This research investigates the potential of using SF, a sustainable filler material, in place of OPC in asphalt mixtures for the base course of road pavements. The study focuses on evaluating the impact of SF as a mineral filler for heavy load requirements in the Indian context. The mechanical response of the asphalt mixtures was evaluated using Marshall stability (MS), the mean Marshall stability ratio (MMSR), and indirect tensile strength (ITS) and water sensitivity (WS) tests for different proportions of silica fume, OPC, and bitumen. As well as providing a comprehensive mechanical and volumetric characterization of asphalt mixtures for base courses made with SF rather than OPC as filler, this study aims to develop a machine learning-based methodology for predicting the mechanical and volumetric parameters of such mixtures. To this end, the experimental data were analyzed using artificial neural networks (ANNs) to create predictive models. Developing accurate predictive equations for the mechanical and volumetric response of asphalt mixes can enhance traditional mix design, which relies on costly and time-consuming laboratory testing.