Guidance for Use of Construction and Industrial Waste By-products in Concrete
This thesis presents a study to synthesize the published literature regarding the use of construction and industrial waste by-product as cement or aggregate in concrete, and aims to incorporate this knowledge along with findings of an agency and industry inquiry into development of a protocol for determining the suitability of waste materials for potential use in new concrete pavement construction. The use of construction and industrial waste by-products is beneficial for both environmental and economic reasons because beneficial reuse of waste materials will reduce environmental impacts of new construction as well as prevent the depletion of natural resources. Construction and industrial byproducts can be used in either bound applications (new concrete) or in unbound applications (base or fill materials) in new construction. Unbound applications are often seen as a lower risk application than bound materials, but minimal standards for physical properties and durability performance must still be met. Additionally, environmental concerns associated with leachate can be an issue. Use of waste byproducts in new concrete can help lower the environmental footprint for this widely used building material. However, performance criteria must still be met. The primary criteria upon which the performance of concrete depends includes fresh properties, mechanical properties, and durability performance. The economics and availability of the materials must also be considered. In this study, the characteristics of base materials and concrete produced using waste by-products, as well as the potential environmental impacts, were investigated and synthesized through a literature review. The perceived lack of guidance to support agency use of, and specification development for, these materials was explored using an inquiry of selected state highway agencies (SHA) and industry. The results of the inquiry conducted were analyzed to evaluate the barriers to use of construction and industrial waste by-products in concrete, identify needs, and assess risk tolerances. Similarities and differences between SHA and industry perceptions of benefits, required tests, and barriers to use were identified using statistical methods. Findings from the literature review and inquiry results were used to develop a methodology (guidance) for evaluating the suitable uses of construction and industrial waste by-products as unbound materials in concrete pavement construction or in concrete mixtures as either an aggregate or a supplementary cementitious material.