Bitumen absorption is a problem with recycled construction aggregate asphalt mixtures (RCA). In this article, we are going to discuss how glass in the hot mix can optimize the process. Laboratory testing is used in this paper to characterize the effects of glass on the bitumen absorption and volumetric properties of asphalt mixtures containing 25% and 50% RCA. Materials such as C320 bitumen, RCA, and recycled glass were used in the testing program. Under 120 gyration cycles, three glass contents of 0%, 10%, and 20% in terms of the total weight of fine aggregates are used in the mixture designs for preparing 100 mm diameter specimens containing 0%, 25%, and 50% RCA. Individual aggregates and asphalt mixtures were subjected to a variety of tests in accordance with Australian standards, including volumetric analysis tests and aggregate specification tests. 
Glass waste has the potential to be a useful material for addressing the issue of high bitumen absorption in RCA-containing asphalt mixtures, according to the test results. Waste production rises steadily as the economy expands and consumption rises. Given the rising amount of waste, scarcity of natural resources, and limited landfill space, finding innovative ways to reuse and recycle waste is critical. The most promising solution to this problem may be to recycle and use Recycled Construction Aggregates (RCA) derived from construction and demolition waste (CDW) in construction projects such as asphalt pavement construction. Because aggregates play such an important role and constitute such a large portion of asphalt mixtures, using RCA in these mixtures is a sustainable technology. RCA has a higher flakiness index and better particle shape characteristics than basalt. These two characteristics can be considered one of RCA's strengths because they have a significant impact on the stability and strength of asphalt mixtures. The main disadvantage of RCA is that it absorbs more water than conventional aggregates, causing asphalt mixtures containing RCA to absorb more bitumen. It is possible to compensate for the high bitumen absorption of asphalt mixtures containing RCA by combining low absorption materials, such as glass. Because glass waste is nonmetallic and inorganic, it cannot be disposed of in incinerators or sanitary landfills; therefore, using waste glass in RCA-contained asphalt mixtures reduces not only bitumen absorption but also the negative environmental effects associated with waste glass disposal. Reduced demand for virgin aggregates is another benefit that leads to additional economic benefits. However, before applying this technology to the production of asphalt mixtures, a suitable mix design containing RCA and glass must be developed. 
The current work's goal is to investigate the benefits of glass addition on the bitumen absorption of asphalt mixtures in order to create the best asphalt mix design possible for RCA-contained asphalt. Various tests on individual aggregates were conducted in this regard, as discussed in the sections that follow, in order to learn more about the properties of recycled aggregate as well as to contrast them with the corresponding properties of virgin aggregate and standard requirements. Based on the aggregate specification tests, various tests were performed on asphalt mixtures containing various combinations of natural and recycled aggregates in order to characterize the effects of glass on the bitumen absorption and volumetric properties of asphalt mixtures containing various percentages of RCA. The experimental results are presented in three sections: volumetric performance of Hot Mix Asphalt (HMA) containing RCA in combination with glass and without glass, mechanical and physical characteristics of coarse aggregates (i.e., RCA and basalt), and physical characteristics of fine aggregates. Today, tires, plastics, glass waste, and other waste products are frequently used to construct various pavement layers, including the asphalt surface layer. Utilizing solid wastes in the asphalt layer reduces not only the negative effects of waste disposal but also the demand for natural resources, resulting in financial savings and other benefits. Incorporating recycled materials into the asphalt surface layer can also improve the engineering qualities of asphalt pavement materials, increasing the value of solid waste. However, the selection of waste materials used for road construction is critical, particularly for the surface course, because the incorporation of wastes should not compromise the structural integrity or functionality of the pavements. Furthermore, due to the importance of aggregates in asphalt concrete, studies on the use of recycled aggregates such as reclaimed asphalt pavement (RAP), recycled construction aggregate (RCA), recycled glass, and so on have grown globally over the last 20 years. 
The use of RCA in new asphalt mixtures is justified by the massive amount of construction and demolition waste generated globally. According to current literature, RCA has been used for pavement base courses and subbase courses for the past 20 years. However, only a few studies have documented the use of RCA in HMA. Comprehensive tests on RCA aggregate specifications revealed that RCA cannot meet the requirements for aggregate in asphalt mixtures for two properties: water absorption and wet/dry strength variation. As a result, using RCA without virgin aggregates may result in less effective asphalt mixtures. As a result, when designing the asphalt mixture, the percentages at which RCA is combined with other aggregates must be considered. Other materials, such as recycled glass, can be considered to compensate for some of RCA's shortcomings. The purpose of this study is to determine the best combination of these materials. Only 350,000 tons of Australia's 850,000 tons of glass are recycled. This means that approximately 500,000 tons of glass are disposed of in landfills each year. The Australian example exemplifies how glass waste is disposed of worldwide. Because waste glass is one of the most significant and particularly problematic components of solid waste because it cannot be incinerated or degraded, combining it with RCA in an asphalt mixture provides significant environmental and economic benefits. As a result, a suitable management strategy must be considered. Recycling is the most common method of dealing with glass waste. Glass can be recycled without affecting the quality of the final product. Recycling glass waste will save a significant amount of energy and mineral resources. Furthermore, glass recycling reduces the rising cost of landfill disposal. However, variations in glass color have prompted authorities to seek new approaches to glass waste management. 
Glass Waste Aggregate
Glass waste has been used to replace fine aggregate in asphalt mixtures in a number of countries, including the United States, Japan, and several European countries. When used as aggregate in asphalt concrete, glass must meet certain technical specifications. As a result, numerous researchers have looked into the use of glass as an aggregate in asphalt mixtures. Arabani and Azarhoosh investigated the behavior of glass-containing asphalt mixtures (glassphalt) under various temperatures and glass-use rates. According to the findings of the investigation, adding glass to asphalt mixtures increases their stiffness and dynamic behavior. Furthermore, asphalt mixtures containing glass are less temperature sensitive than conventional mixtures. Jony et al. investigated the effect of incorporating various fillers, including glass powder, at different rates in asphalt mixtures in a separate study (2011). This study found that using glass powder as a filler improves the Marshall Stability of asphalt mixtures when compared to asphalt mixtures made with Portland cement or limestone powder. Pereira et al. conducted research in 2010 on the use of used flat glass as a filler in asphalt mixtures. This study concluded that used glass can be successfully used as a filler in asphalt mixtures. As part of another field study, two road segments were built in Minnesota using two different sizes of crushed glass. The results of a rutting test on these roads, according to Marti et al., show that asphalt mixtures containing waste glass with a maximum size of 4.75 mm have greater dynamic stability than those containing waste glass with a size of 9.5 mm. Other research by Arnold et al. demonstrated that the addition of up to 30% glass waste by mass has no material effect on aggregate performance. According to Shafabakhsh and Sajed's findings, asphalt mixtures containing 10 to 15% crushed glass perform satisfactorily. According to Finkle and Ksaibati's, waste glass can be used as an alternative to virgin road base materials. 
However, based on this research, it was suggested that the glass content be limited to 20% and the maximum size be limited to 12 mm. Wu et al. investigated the effectiveness of asphalt mixtures containing waste glass as fine aggregate. According to this study, the maximum size should be 4.75 mm, with an ideal content of 10%. A report written by the Australian Road Research Board (ARRB) Group for the Packaging Stewardship Forum (PSF) of the Australian Food and Grocery Council suggested using glass up to 20% as a fine aggregate in asphalt mixtures. Only 30% of the total fine aggregate in the asphalt mixture can be recycled into glass, according to the findings of this study. Using Su and Chen (2002) as a reference, it can be stated that the engineering characteristics of asphalt mixtures containing crushed glass waste were investigated through laboratory and field tests during a research program in Taiwan. The findings of this study demonstrated that incorporating glass waste into asphalt mixtures provides significant financial and technical benefits. Pioneer Road Services conducted the nation's first glass mix trials in 2003. The roads were compared to standard asphalt roads in terms of skid resistance. The investigation found that asphalt mixtures containing glass waste have comparable skid resistance to standard asphalt mixtures. According to Viswanathan's (1996) research, used glass can be used in highway construction. The feasibility of using recycled glass to compensate for the high bitumen absorption of RCA-containing asphalt mixtures was investigated in this study. Tests on aggregates and asphalt mixtures containing RCA with or without glass revealed that Because RCA has fewer misshapen particles and a lower flakiness index than basalt, asphalt mixtures containing a small amount of RCA may improve compaction, workability, and rutting resistance. 
In terms of water absorption and wet/dry strength variation, RCA significantly outperforms virgin aggregate. RCA continues to meet the standards for aggregates in asphalt mixtures, according to test results. However, the high water absorption of RCA should be compensated for. Asphalt mixtures containing RCA have lower bulk densities, VMA, VFB, and BFI when compared to control mixes, but higher air void contents. Because asphalt jobs are usually measured in cubic meters and materials are bought in tons, RCA with a lower bulk density will be less expensive. Test results on various asphalt mixtures with varying RCA percentages revealed that increasing the RCA causes the ideal bitumen content of the mixtures to rise. As a result, selecting the appropriate RCA and another aggregate mixture is required to meet the relevant standard requirements. It was discovered that adding recycled glass with very low water absorption to asphalt mixtures containing various combinations of RCA reduced the amount of bitumen absorbed. Test results on various asphalt mixtures containing RCA and glass show that as glass content increases in asphalt mixtures, bitumen absorption decreases. In other words, glass-containing asphalt mixtures have a lower optimum bitumen content than asphalt mixtures without glass. Asphalt mixtures containing 75% RCA with 10% and 20% glass, as shown in Table 8, have an optimal bitumen content that is very close to the optimal bitumen content of control samples (asphalt mixtures without any recycled materials). Air void, VMA, and bulk density are lower in asphalt mixtures containing RCA and glass at various bitumen content rates than in asphalt mixtures containing RCA alone while adding glass to the asphalt mixtures increases VFB in asphalt mixtures containing both RCA and glass compared to asphalt mixtures containing only RCA. 
Based on an analysis of the volumetric properties of all asphalt mixtures at their ideal bitumen contents in Table 9, the mixture made by mixing 25% RCA and 10% glass is the most similar to control samples in terms of volumetric properties and ideal bitumen content requirements. According to the results of a resilient modulus test on a few different asphalt mixtures, asphalt mixtures made of 25% RCA and 10% glass have about 15% more stiffness than conventional mixtures. The resilient modulus test results show that asphalt mixtures containing 25% RCA and 10% glass improve both the structural performance and the environmental impact of asphalt pavements. The resilient modulus of asphalt mixtures is an important parameter in determining the overall structural performance of pavement, influencing layer thickness, service life, and overall pavement construction cost.