PSI - Issue 64

4

Rahma Dhemaied et al. / Procedia Structural Integrity 64 (2024) 343–351 Rahma Dhemaied/ Structural Integrity Procedia 00 (2019) 000 – 000

346

3.2. Chemical properties The chemical properties of RCA are influenced by the composition of the original concrete from which it was derived. One notable characteristic is the higher pH value (more alkaline) of RCA compared to natural aggregates (Marinković et al., 2010) . This elevated alkalinity is attributed to the alkaline nature of the cement paste residue adhered to the RCA particles. Another important chemical consideration is the potential for alkali-silica reactivity (ASR) in concrete containing RCA. The presence of reactive silica in the adhered mortar of RCA can increase the risk of ASR (Cassiani et al., 2021), which is a deleterious reaction between the alkalis in the cement paste and certain reactive silica minerals. ASR can cause expansion and cracking in concrete pavements, leading to premature deterioration. Proper mitigation measures, such as the use of supplementary cementitious materials or chemical admixtures, may be necessary to prevent or minimize the effects of ASR when using RCA. Depending on the source of the recycled concrete, RCA may also contain trace amounts of heavy metals (Puthussery et al., 2017), which could potentially leach into the environment. Environmental considerations and leaching tests may be necessary to ensure the safe use of RCA in pavement construction. 3.3. Durability factors Despite some of the challenges associated with the physical properties of RCA, it has demonstrated favorable durability characteristics in certain aspects. Notably, RCA can have comparable or even superior resistance to freezing and thawing cycles compared to natural aggregates (Richardson et al., 2011). This resistance to freeze-thaw damage is an important consideration for pavements in cold regions, where repeated cycles of freezing and thawing can cause significant deterioration. On another positive note, RCA has shown better resistance to sulfate attack compared to natural aggregates (Tam et al., 2007). This improved sulfate resistance is attributed to the presence of supplementary cementitious materials, such as fly ash or slag, in the adhered mortar of RCA, which can enhance the concrete's resistance to sulfate-induced degradation. It's essential to thoroughly characterize and assess the specific properties of RCA from different sources, as they can vary significantly depending on the original concrete composition, processing methods, and exposure conditions. Appropriate material selection, mix design, and construction practices are crucial to mitigate potential durability and chemical issues while leveraging the benefits of RCA in pavement applications. 4. Pavement Design Considerations Due to their sustainability benefits, recycled concrete aggregates, or RCAs, are becoming more and more integrated into pavement design methodologies such as the Mechanistic-Empirical Pavement Design Guide (MEPDG), which permits modifications to material properties during the design phase. To better understand how RCA affects pavement performance, specialized models and calibration factors have been developed. This has made it possible to make modifications like resilient modulus adjustments and fatigue life predictions (Disfani et al., 2014). In addition, potential variations in the mechanical characteristics of RCA and conventional aggregates should be taken into consideration in the design, and elements such as pavement thickness and reinforcement should be modified accordingly (Pourkhorshidi et al., 2020). According to some case studies example in Austria (Gomez-Soberon, 2002) and Ontario, Canada (Butler et al., 2012), RCA pavements perform as well as or better structurally than conventional pavements. The angularity of RCA and the presence of old mortar within the particles are responsible for the improved fatigue resistance, rutting resistance, and thermal cracking resistance of RCA pavements. Adherence to production and construction practices is crucial, as evidenced by the significant impact that proper grading and quality control measures have on performance. RCA's compatibility with existing pavement infrastructure and construction techniques minimizes the need for modifications, promoting its adoption in projects and offering cost-effectiveness, resource conservation, and waste reduction advantages. Thereby, the use of RCA in pavement construction is crucial due to environmental