This dissertation is a compilation of three papers that describe utilizations of fly ash in combination with other waste materials to produce new construction materials and a new soil classification system for use during design and construction of cohesive earth embankments. The first paper describes the long-term performance of a demonstration project where road base materials were constructed from reclaimed hydrated fly ash (HFA) with atmospheric fluidized bed combustion (AFBC) and cement kiln dust (CKD) by-products used as calcium activators. Reclaimed HFA is a form of artificial aggregate produced from compacted, hydrated (ASTM class C) fly ash at pulverized coal combustion facilities. Strength testing and chemical analysis indicate that AFBC and CKD activators increase cementitious and pozzolanic reactions in the HFA material. Long-term testing indicates that the high-volume alternative use of these by-products is an economical and suitable application;The second paper describes strength tests and microstructural features of a composite material from high-lime fly ash and recycled polyethylene terephthalate (PET) plastic. Composite specimens with varying fly ash concentrations were tested in compression and tension, immersed in water to measure water absorption, and observed for shrinkage during manufacturing. Theoretical equations for modulus of elasticity and tensile strength are derived with values compared to Portland cement concrete. The results of this investigation show that the fly ash concentration contributes significantly to both the strength of the composite material and the crystallinity of the PET binder;The third paper describes field-testing and laboratory analysis that were conducted to develop a simple and rapid performance-based soil classification system for cohesive earth embankments. Development of the Empirical Performance Classification (EPC) system is founded on swell potential and frost susceptibility relationships derived from liquid limit, plasticity index, and fines content (≤75 mum). From these parameters the EPC chart is used graphically to classify soils into one of three categories: select, suitable or unsuitable. This paper presents the background for the development of this system and procedures for its use. A field trial indicates that field personnel can effectively use the EPC system to better link soil design with construction activities.