*9.5. Treatment of RCA*

Due to the varying performance of RCA and its negative impact on most of the properties and concrete durability, several studies have suggested methods for treating RCAs in order to improve their properties and promote its application in the concrete industry safely [172]. The treatment methods depend on several factors, including the source, type of aggregate, and applications of RCA-containing concrete. The studies have suggested different approaches.


#### **10. Practical, Economical, and Environmental Issues of RCA Concretes**

Obviously, for the economic feasibility of RCA production, ready-mix concrete plants can be used to obtain production scale for production. Economic impact assessment is effective when it is considered that the action of the case does not require additional payment. He looks at the recycling of waste concrete in ready-mixed concrete plants as infrastructure and construction resources. The prototype developed is based on information obtained from various industrial shops as well as concrete processing shops, which are used as a scenario study to estimate the additional commercial price of a product. The current problems facing Thailand, where there are so many landfills for concrete waste as a result of destruction plans, and inappropriate concrete is being disposed of, will be addressed using RCA production [72]. The growth in RCA replacement is primarily associated with an increase in additional unit costs of resources. In particular, the replacement of the cement content is increased as a result of the increase in the RCA replacement ratio. The increase in RCA cost is associated with additional quality control and pre-processing costs. However, upfront costs can be reduced by going directly to a high quality concrete plant.

Compared to a recycling approach where construction waste is used in recycling plants to obtain new materials, the traditional costs are very high [178]. The first stage of the recycling process includes construction waste that is disposed of at low cost recycling facilities. Additional costs include energy consumption and transportation costs. The second stage is stockpiling, in which lone workers are employed at a rate of \$18 an hour. The third step is sorting with machines, such as a shredder and excavator. Also accrued are additional costs for equipment maintenance, labor, fuel, fixed indirect costs, working capital, operating costs, equipment costs, and capital costs [75]. Crushing processes in the fourth phase include magnetic separation, primary crushing, and secondary crushing. This includes fuel costs, fixed indirect costs, operating costs, working capital, and capital costs. With magnetic separation, the process also includes sorting steel scrap and sells for about \$100 per ton. The casting phase includes manual removal processes in which pieces of paper, wood, and plastic are separated from the grounded concrete. In this process, the wages are about \$18 an hour. The sixth stage involves sitting in the air, watching, and doing laundry, which is identical to the traditional approach. Recycled fuel and water are used to deposit dust particles at this stage [178]. The final stages of the refining process include finished products that sell for between \$14 and \$22 per ton.

Thus, compared to the traditional approach, RCA has the most cost-effective gain [75]. The financial benefits of recycling concrete lead to longer-term benefits than using natural concrete. Sensitivity analysis is performed, taking into account the main parameter due to the expected uncertainties with the main variables used in the model [153]. The purpose of the analysis is to determine the main variable impact of modification on one unit of output. The main factors to be taken into account are transport distance, additional costs for RCA pretreatment, additional cement required to produce RCA, and RCA composition [138]. Due to depleted natural resources, crushed concrete for demolition is produced in large quantities and must be used in an environmentally friendly and economical manner. Deterministic values are defined as means because the parameters have normal distribution characteristics. The range of input variables can be estimated to determine upper and lower bounds. The RCA price cap range is determined by breaking down changes in the value of a product by changes in quantities [148].

#### **11. Comments and Further Researches**

The literature in this paper is summarized to provide comprehensive insights into the potential applications of RCA to produce green and sustainable concrete composites that contribute to environmentally friendly buildings. Therefore, differences in the current state of knowledge between RCAs and NCAs are highlighted, and some suggestions for future research are provided. In addition, this study also contributed to uncovering deficiencies in previous research and studies, which requires further research and investigation into the following points:

