Utilization of Recycled Materials in Illinois Highway Construction
- Steel reinforcement is made entirely of recycled scrap iron. This material is salvaged from automobiles, appliances, and steel-reinforced structures which include reinforced concrete pavements, bridges, and buildings. Two common forms of steel production are the basic oxygen and electric arc processes. In the electric arc process, "cold" ferrous material, which is generally 100 percent scrap steel, is the major component melted with alloys in an electric furnace. In the basic oxygen process, molten iron is removed from the blast furnace, combined with alloys, and up to 30 percent steel scrap-used as an additive to lower the temperature of the molten composition. In both processes, high-pressure oxygen is blown into the furnace causing a chemical reaction that separates the molten steel and impurities, which can be recycled as slag (1, 11).
- Physical Properties:
- The primary component of steel is iron alloyed with various elements, such as silicon, manganese, chromium, nickel, or copper. In production, carbon, phosphorus, and sulfate may also be present and altered, resulting in different grades of steel (1).
- Engineering Value:
- Steel reinforcement plays an important role in concrete structures; for example, reinforcing in PCC pavements holds cracks together ensuring high aggregate interlock exists across the pavement. Steel reinforcement may also eliminate the use of joints in pavement-potentially producing a longer lasting, smoother riding surface. These same qualities are also desirable in reinforced concrete drainage structures.
- Present Application:
- Steel reinforcement is used to strengthen concrete structures, such as reinforced PCC pavements and bridge decks. Two types of commonly used reinforced concrete pavements are jointed reinforced concrete (JRC) and continuously reinforced concrete (CRC). JRC pavements utilize welded wire fabric, while CRC consists of overlapping longitudinal and transverse reinforced steel bars (3, 11).
- Quantity Used:
- 15,150 tons of rebar; 582,500 SF of welded wire fabric(2001 MISTIC estimate)
- Economic Impact:
- Reinforced concrete structures are an integral part of Illinois' transportation system. Overall, reinforcing steel in concrete contributes to the durability and high structural strength of pavements and structures. In 2001, approximately $10,660,000 was spent on reinforcing steel in highway construction.