مقاله انگلیسی رایگان در مورد مصالح بتنی بازیافت شده و تاثیر آن در تولید بتن جدید – الزویر 2018

Concrete is known as one of the most highly consumed construction materials. The primary ingredients of a concrete mixture are cement, aggregates (coarse and fine), water and admixtures (Mindess et al., 2003; National Ready Mixed Concrete Association (NRMCA), 2012). Among the aforementioned components, aggregate takes up about 70% to 80% of concrete’s volume. Types of NAs that are commonly used in concrete application consist of crushed stone, sand, and gravel (USGS, 1997). These NAs are obtained through mining natural resources and opening aggregate quarries. The mining process of NAs generally takes place in vast aggregate quarries that involves heavy equipment and consumes an excessive amount of energy. The resources of NAs are abundant but finite (USGS, 1997). Challenges may develop in construction due to depletion and scarcity of the sources, restrictions on opening new sources and the increased production cost. Using recycled aggregate (RA) may help to address some of these challenges (ACPA, 2009; Verian, 2012). RA can be derived from existing concrete, and thus, termed as recycled concrete aggregate (RCA). According to de Vries (1996), the application of RCA in construction works has become a subject of priority throughout many places around the world. As indicators, 10% of the total aggregates used in the United Kingdom (UK) are RCA (Collins, 1996), 78000 tons of RCA were used in the Netherlands in 1994 (de Vries, 1996) while Germany has been aiming a target of 40% recycling rate of its building and demolition waste since 1991 (van Acker, 1998). According the data in 1997, 0.9 million out of 1.06 million metric ton of the recycled old concrete was used for construction in Denmark (Schimmoller et al., 2000). The annual production of recycled materials derived from old asphalt pavement reached 0.8 million metric ton in Sweden in 1999, in which 95% of it was used in the new asphalt pavement (Schimmoller et al., 2000). Florea and Brouwers (2012) have reported that due to the costly landfilling process, which I some cases are more costly than recycling, many European countries have set a high bar for their recycling goals – between 50% to 90% of their construction and demolition (C&D) waste production. In the United States (U.S.), nearly 100 highway paving projects by the mid-1990s had incorporated RCA in concrete for pavements, some of which are derived from pavements exhibiting D-cracking and alkalisilica reaction (ASR) damage (Burke et al., 1992). As one of the solutions in preserving the environment and as it is rich in potentials, the use of RCA has been rising and is encouraged. For this reason, understanding the characteristics of RCA is critical to assure the success of its application. This manuscript presents information regarding the state-of-the-art of the characteristics of RCA, its effects on concrete properties, and various methods to optimize its application.