RESUMO
Recycled concrete aggregates (RCA) and reclaimed asphalt pavements (RAP) are two construction waste products that are commonly used in the road construction industry. Besides many advantages, pollutants leaching from RCA and RAP are highlighted as the most concerning environmental issue. This study investigated metals leaching characteristics from RCA and RAP due to the variations in key influential factors of pH, dissolved organic carbon (DOC), compaction and liquid to solid ratio (L/S). The leaching tests for RCA and RAP were carried out separately and additionally, the standard leaching test was conducted as the benchmark for leaching investigations. Study outcomes revealed that the combined influences of factors are variable for RCA and RAP, while influences are also variable for individual metals. L/S ratios considerably affect the release of metals from RCA under saturated conditions, facilitating high metal concentrations in the leachate. On the other hand, acidic solutions are more favourable for leaching of metals from RAP. The influence of DOC in solution was minimal on the metal leachability. Interestingly, the increased degree of compaction with a higher density of materials presented the highest negative influence on metal leachability, suggesting that the metal leachability can significantly reduce, in particular when the RCA and RAP are used for the sub-base layers of road structure with a higher degree of compaction. However, the use of these recycled materials under field conditions should be further studied as there is an increasing concern of metal leaching from RCA and RAP with respect to recreational and drinking water thresholds.
RESUMO
Slaking is a process of material parameters alteration resulting from wetting-drying cycles, changes in overburden stress, and chemical interactions. Tailings Storage Facilities (TSF) constructed with materials prone to slaking may experience breaches, especially during the post-closure period, due to the deterioration of shear strength and permeability characteristics. Rockfill materials, particularly those containing clay components, can undergo various forms of crack formation, leading to disintegration as a result of wetting-drying cycles, stress increments, and intense compaction. However, there are currently limited methodologies available for replicating such material alterations on a laboratory scale. Therefore, a new large-scale laboratory testing approach has been designed to simulate variations in wetting-drying cycles, humidity, and overburden pressure, enabling the prediction of the slaking potential of TSF construction materials. This novel methodology replicates field drying-wetting cycles and variations in humidity and overburden stress in a controlled environment, allowing for the estimation of the deterioration of shear strength and permeability characteristics in rockfill materials.
