Pollution and waste are continually generated. The production of waste. however. has increased rapidly in recent years. An efficient and safe means of either neutralizing or disposing of this waste has been increasingly researched. In recent times, the potential of recycling and reusing the waste in construction works has been investigated. The studies have highlighted the benefits of such applications. In line with these studies, the current study investigated the suitability of using Incinerator Bottom Ash Waste (lBA W) as an alternative to conventional aggregates in the construction of road foundations. IBA W is a residual material produced by incinerating Municipal Solid Waste (MSW). The potential advantage of this approach is that the reuse of IBA W helps to conserve the supplies of conventional aggregates and reduces the landfills needed to store the waste. However, such applications may cause serious environmental impacts as IBA W may be exposed to intermittent infiltration as a consequence of precipitation events or altering of the water table, resulting in a potential release of pollutants to soil and groundwater. This work is divided into three main parts. The first part investigates the potential environmental impacts by using leaching tests for treated and untreated IBA W. The treatment including stabilization and chemical processes was applied in this study for IBA W by using different types of novel and traditional additives. This treatment aimed at immobilizing the pollutants by integrating them in a strong matrix. The Iysimeter as a leaching tool was adopted to assess the potential impact of changing conditions such as liquid to solid ratio (LIS), pH value, IBA W content and different treatment agents on long-term release of heavy metals and salts to estimate the environmental risks of IBA W. Appropriate and reliable leaching models based on initial measurement of intrinsic material properties and simplified testing were used to predict the release of constituents of concern from IBA W and its migration and fate into soil. The second part of the thesis aims at analyzing the microstructure of IBA W material by using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDXS) techniques. These tests are adopted to manifest the physical and chemical features of IBA Wand identify the nature of the materials and any secondary reaction elements, especially after mixing with water, with and without additives. This helps understanding the behaviour of the materials because there is a good correlation between the microstructural and chemical composition of the materials and their mechanical behaviour. The third part studies the mechanical properties of IBA W as an aggregate. An experimental programme has been undertaken to investigate the influence of treatment on the behaviour of IBA W blends for use as foundation layers. The research has focused on determining the blends' resilient modulus and permanent deformation. Cyclic and static triaxial compression tests were adopted to determine the materials' mechanical characteristics. Light Weight Falling Deflectometer (L WFD) test was also adopted as an in-situ evaluation for the elastic modulus of IBA W. Emphasis has been on examining the effect of various parameters, such as IBA W content, type and content of additives, moisture content, curing time and maximum nominal particle size on the behaviour of the investigated blends. The shakedown concept was adopted to evaluate the behaviour of the IBAW material under cyclic loading as a granular material. A new calculation model was proposed to estimate the plastic deformation of IBA W and granular materials under monotonic loading. Finite element modelling was adopted to simulate the IBA W material behaviour under static, cyclic and impact loading in macro and micro scales. The main findings of this study are that IBA W can be reused safely and successfully as an aggregate in construction applications. It also illustrated that IBA W may show similar or even better behaviour than conventional aggregate as observed under some conditions. IBA W also showed typical behaviour of conventional aggregates using the theoretical and modelling approaches. Some novel and traditional treatment agents resulted in a good improvement in IBA W behaviour in terms of environmental and mechanical properties.