Construction aggregate

Abstract: Considerable usage of natural aggregates for road construction, and at the same time, the increasing amount of solid wastes, have attracted the attention of many researchers in the pavement industry to investigate the feasibility of the application of some of the waste materials in pavement construction. Construction and demolition wastes, including Recycled Construction Aggregate (RCA) constitute a major part of the municipal solid wastes. Using RCA in asphalt mixtures generally results in significant economic and environmental benefits. However, in spite of such promising potentials, insufficient and inconclusive data and information on the engineering properties of RCA had limited the reliability and design specifications of RCA to date. In light of this, this paper aims to investigate the feasibility of the application of RCA in asphalt mixtures. As the suitability of aggregates for using in asphalt mixtures is determined based on the aggregate characteristics, an experimental program is set up to evaluate the physical and mechanical properties of RCA. This laboratory investigation included the measurement of RCA compressive strength, particle shape, water absorption, flakiness index, crushing value, weak particles, wet/dry strength variation, and particle density. Based on this research, it was observed that RCA has a lower value of flaky and misshapen particles in comparison with basalt, implying that asphalt mixtures containing the certain amount of RCA can have better workability, deformation resistance and compaction. However, the test results show higher water absorption and wet/dry strength variation for RCA compared to natural materials, emphasizing on the necessity of an appropriate mix design.

Abstract: This technical note explores the concepts and applications of recovering and reusing two common disposable materials (crushed glass and dredged spoil) for beneficial engineering purposes. Dewatered fine-grained dredged material (DM) amended with glass cullet may prove to be a marketable combination especially useful as an engineered material and construction aggregate substitute.

Abstract: Iron and steelmaking slag is a by-product of the iron and steelmaking process. Slag has traditionally been used as a component of cement and construction aggregate. NKK has led the industry in promoting the effective use of slag. In this paper, fine concrete aggregate, known as Sandy-S, and slag sand-capping material are introduced as new applications of granulated blast furnace slag. Other innovative uses of steelmaking slag are introduced: large carbonated slag blocks, called Marine Blocks, produced by injecting carbon dioxide into slag compact, and potassium silicate fertilizer produced by adding a potassium source to steelmaking slag.

Abstract: Slag, an abundant by-product from the pyrometallurgical processing of ores, can be an environmental liability or a valuable resource. The most common environmental impact of slag is from the leaching of potentially toxic elements, acidity, or alkalinity that may impact nearby soils and surface water and groundwater. Factors that influence its environmental behavior include physical characteristics, such as grain size and porosity, chemical composition with some slag being enriched in certain elements, the mineralogy and partitioning of elements in more or less reactive phases, water-slag interactions, and site conditions. Many of these same factors also influence its resource potential. For example, crystalline ferrous slag is most commonly used as construction aggregate, whereas glassy (i.e., granulated) slag is used in cement. Also, the calcium minerals found in ferrous slag result in useful applications in water treatment. In contrast, the high trace-element content of some base-metal slags makes the slags economically attractive for extraction of residual elements. An evaluation tool is used to help categorize a particular slag as an environmental hazard or valuable by-product. Results for one type of slag, legacy steelmaking slag from the Chicago area in the United States, suggest the material has potential to be used for treating phosphate-rich or acidic waters; however, the pH and trace-element content of resulting solutions may warrant further examination.