Waldemar,

Lightweight waste aggregates, including expanded clay, shale, and thermally treated fly ash, are increasingly being utilized as an alternative to traditional concrete aggregate materials in the United States. As of 2019, lightweight aggregate concrete is estimated to account for 8-10% of the U.S. concrete market (Bruley & Whitens, 2019). This alternative offers multiple advantages, including improved workability, a more consistent design, reduced water content, and reduced environmental impact compared to virgin aggregate sources (Do Rozario et al., 2018). Expanded clay is one of the most widely used lightweight aggregates in the U.S. This product is produced by heating clay to temperatures above 1,000°C (1,830°F); this causes a reaction that generates light ceramic particles and a hollow structure. Due to its unique design, expanded clay has higher strength-weight ratios, low absorption rates, and excellent insulation properties than traditional aggregates (Tsinker, 2011; Migliazzo, 2009). Additionally, expanded clay can absorb seismic shock energy, making it suitable for earthquake-prone regions (Tascioglu, 2019). Shale is another important lightweight aggregate material used in the United States. This product is produced by heating the sedimentary rock to temperatures above 1,000°C (1,830°F). It comprises aggregates easily dispersed in water and possesses low bulk densities relative to traditional aggregate materials (Migliazzo, 2009). Shale has strong compressive and durability strengths, making it suitable for mixing concrete for multiple applications, such as foundations, walls, and bridges (Vasion et al., 2020). Lastly, thermally treated fly ash is a lightweight aggregate material made from a byproduct of coal-fired power plants. During the production process, the fly ash is heated to temperatures between 1,300-1,500°C (2,372-2,732°F); this causes a reaction that generates small particles and a hollow void structure, resulting in strength-weight ratios that are superior to traditional aggregates (Van de Voorde et al., 2002). Also, thermally treated fly ash has low absorption rates, making it suitable for use in concrete with high water-cement ratios (Lauwers et al., 2004). Lightweight aggregate materials are an increasingly popular alternative to traditional concrete aggregate materials in the United States. Expanded clay, shale, and thermally treated fly ash are the three primary products of lightweight aggregate concrete. These materials possess unique properties, such as superior strength-weight ratios, low absorption rates, and excellent insulation and durability properties. These materials are ideal for commercial, industrial, and residential concrete production.

References:

Bruley, J.F., & Whitens, W.S. (2019). Lightweight aggregate concrete: A comprehensive overview. Structural Concrete, 20(4): 1253–1264.

Do Rozario, M.M., Lima, R., Manzi, A.C.O., and Drost, K. (2018). Lightweight aggregate concrete: Recent advances in science and technology. Scientific Reports, 8(1): 1-13.

Lauwers, B., Barbotin, J.F., De Kestelier, X., Cnudde V., and Vand Peer, J. (2004). Effect of cement content and fly ash on the rheology of lightweight concrete. Cement and Concrete Research, 34: 2171-2179.

Migliazzo, C. (2009). Lightweight aggregate in concrete: Properties and applications. Thomas Telford, London.

Tascioglu, C. (2019). Performance of expanded clay aggregate concrete in seismic applications: Historical review and advancements. Construction and Building Materials, 217: 280-293.

Tsinker, Y.Y. (2011). Expanded clay lightweight particle aggregate concretes. In Uy um M. Yal ̧cin, M. (Ed.), Lightweight aggregate concrete (pp. 1-18). InTech, Vienna.

Van de Voorde, L., De Schutter, G., Postel, S., Kolaczkowski, S., and Tricarico L. (2002). Mechanical and structural properties of lightweight aggregate concrete made with fly ash and aluminum paste. Cement and Concrete Research, 32: 1089-1095.

Vasion, L., Prekorać, B., Golubović, D., and Medvidović, N. (2020). Shale lightweight concrete: Production technologies and representation of strength-related characteristics. Materials, 13(2), 270.

In the Middle East, several lightweight waste aggregates are being explored for use in concrete to minimize environmental impact. These include oil palm shells, a byproduct from the palm oil industry, and scoria, a type of porous volcanic rock. Fly ash, a coal combustion residue from power plants, is also used as a lightweight aggregate or a partial cement replacement. Expanded perlite, a type of heated volcanic glass, offers lightweight, fire-resistant, and insulating properties. Additionally, waste materials such as ground recycled glass and plastic waste are considered viable alternatives to traditional aggregates. However, the specific utilization of these materials can differ based on each country's guidelines and regulations within the region.