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The need for road (re)construction materials is constantly growing. At the same time, there is a limited quantity of new, high-quality materials available and a buildup of secondary/recycled construction materials. One possible solution may be the use of recycled concrete aggregate (RCA) in asphalt mixtures instead of natural aggregate (NA), which also promotes economic and environmental sustainability. The potential use of fine and coarse RCA in road asphalt mixtures is analyzed in this work. Nine asphalt mixtures were tested for base course layers, where RCA was used as a NA substitute. The impact of the quantity of RCA (up to 45% by mass) on the resulting physical and mechanical properties of asphalt mixtures was investigated, and consequently compared with the properties of a reference control mixture produced with NA only. Results reveal that the addition of RCA requires higher bitumen in comparison to the control mixture (up to 1%). Consequently, mixtures with RCA had 15−20% lower stiffness and up to 26% higher critical fatigue strain value (ε6). Although RCA mixtures contained more bitumen, their low-temperature resistance was slightly inferior compared with the control mixture (failure temperatures were up to 4.3 °C higher). In conclusion, asphalt mixtures with up to 45% RCA can be used without substantially reducing performance.

Properties modeling of cement composites made of fly ashThere is a number of advantages when using fly ash in cement composites. Fly ash is known for decades for its' pozzolanic properties, and thus it is mostly used as an mineral admixture in the process of production of cement. This way benefits like saving energy and reduction of CO2 emission are obtained. This paper presents the results of research conducted on cement composites made with fly ash from Serbia, added as a partial substitute for cement. The properties of fresh and hardened cement composites were studied with replacement of different mass quantites of cement. Studies have shown that with the moderate amount of fly ash (up to 30%) it is possible to obtain satisfactory physical and mechanical properties of cement composites, both in fresh and hardened state.

This study investigates the feasibility of using recycled concrete aggregate (RCA) as a partial substitution of natural aggregate in pavement engineering. Despite RCA’s good properties, such as polishing value and freeze-thaw resistance, its use is limited by low resistance to fragmentation and high-water absorption. This paper parent the experimental results of mineralogical-petrographic and physical-mechanical properties of RCA, natural stone (dolerite) and their combination (RCA content—15%, 30%, 45%, and 60%). The tested granular mixtures showed good resistance to fragmentation and wear (LA 22–27%, MDE 14–15%), as well as satisfactory Polished Stone Value of 55–57, which means they can be used in different layers of pavement structures. According to the obtained testing results, the application of RCA is possible in different flexible and rigid pavement layers and for various traffic loads.

Copper slag, a by-product of the pyrometallurgical process used for obtaining copper from copper ore in Bor, Serbia, contains mainly silicon, iron, calcium, and aluminium oxides. Due to such properties, it is disposed of in landfills. Despite the favourable technical properties copper slag aggregates possess, such as low-water absorption (WA24 0.6%), low resistance to fragmentation (LA 10%), and low resistance to wear (MDE 4%), its use in the construction industry is still limited. The results of testing the technical properties of copper slag aggregates (CSAs) as a potential replacement for natural river aggregate (RA) are presented in this paper. The experiments included tests on three concrete mixtures with partial replacement of coarse natural aggregate with copper slag. The replacement of RA particle sizes of 8/16 mm and 16/31.5 mm with CSA in the amount of 20% + 50% and 50% + 50% resulted in an increase in the compressive strength of 12.4% and 10.5%, respectively. The increase of CSA content led to a decrease in water penetration resistance and salt-frost resistance of concrete, whereas the resistance to chloride ion penetration did not change significantly.

Article Highlights • Two methods to enhance coarse recycled concrete aggregate quality are used (HCl and CO 2 treatment) • Carbonation process has positive effects on improving physical and mechanical properties of RCA • HCl treatment caused the increase in chloride content and the reduction of sulfate content in RCA • If RCA is obtained from high-quality concrete, quality improving procedures are not necessary

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