Production of asphalt mixes with copper industry wastes: Use of copper slag as raw material replacement.

Copper slag is a waste obtained from copper production and it has a limited use, being mainly accumulated in landfills on a massive scale. This material presents a high hardness and it has hydrophobic properties, so it can be used as aggregate replacement in the production of asphalt mixtures. However, each size of copper slag behaves differently when used in asphalt mixes, especially under changing conditions of moisture or temperature. Precisely these climatic factors directly affect the service life of asphalt pavements. In this research, semi-dense graded asphalt mixtures were produced with copper slag as replacement of aggregates, varying the particle sizes used in the range from 2.5 to 0.08 mm to determine the size of copper slag with the best performance. Indirect tensile strength tests were used to analyze samples subjected to different moisture and temperature conditions and ageing degrees. The results show that copper slag can be used as aggregate replacement in asphalt mixes when the proper size is selected. The strength of the asphalt mixture increased as the size of the copper slag increased, especially under variable moisture and ageing conditions. Superior behaviour compared to a reference mixture was obtained when replacing the size of aggregate No. 8 with copper slag, increasing its indirect tensile strength and retained strength, reducing its stiffness under all the ageing periods, and being equally effective at the different temperatures, which results in mixtures with improved durability and delayed cracking. Furthermore, it would help to reduce between 15 and 20% of the virgin aggregate needed to produce asphalt mixes and it would also allow reducing the accumulated volume of this waste, decreasing the environmental impact of both industries.

Characterization of wash-off from urban impervious surfaces and SuDS design criteria for source control under semi-arid conditions.

Knowledge about pollutant wash-off from urban impervious surfaces is a key feature for developing effective management strategies. Accordingly, further information is required about urban areas under semi-arid climate conditions at the sub-catchment scale. This is important for designing source control systems for pollution. In this study, a characterization of pollutant wash-off has been performed over sixteen months, at the sub-catchment scale for urban roads as impervious surfaces. The study was conducted in Valencia, Spain, a city with a Mediterranean climate. The results show high event mean concentrations for suspended solids (98mg/l), organic matter (142mgCOD/l, 25mgBOD5/l), nutrients (3.7mgTN/l, 0.4mgTP/l), and metals (0.23, 0.32, 0.62 and 0.17mg/l for Cu, Ni, Pb, and Zn, respectively). The results of the runoff characterization highlight the need to control this pollution at its source, separately from wastewater because of their different characteristics. The wash-off, defined in terms of mobilized mass (g/m2) fits well with both process-based and statistical models, with the runoff volume and rainfall depth being the main explanatory variables. Based on these results and using information collected from hydrographs and pollutographs, an approach for sizing sustainable urban drainage systems (SuDS), focusing on water quality and quantity variables, has been proposed. By setting a concentration-based target (TSS discharged to receiving waters <35mg/l), the results indicate that for a SuDS type detention basin (DB), an off-line configuration performs better than an on-line configuration. The resulting design criterion, expressed as SuDS volume per unit catchment area, assuming a DB type SuDS, varies between 7 and 10l/m2.

Water quality and quantity assessment of pervious pavements performance in experimental car park areas.

Pervious pavements have become one of the most used sustainable urban drainage system (SUDS) techniques in car parks. This research paper presents the results of monitoring water quality from several experimental car park areas designed and constructed in Spain with bays made of interlocking concrete block pavement, porous asphalt, polymer-modified porous concrete and reinforced grass with plastic and concrete cells. Moreover, two different sub-base materials were used (limestone aggregates and basic oxygen furnace slag). This study therefore encompasses the majority of the materials used as permeable surfaces and sub-base layers all over the world. Effluent from the test bays was monitored for dissolved oxygen, pH, electric conductivity, total suspended solids, turbidity and total petroleum hydrocarbons in order to analyze the behaviour shown by each combination of surface and sub-base materials. In addition, permeability tests were undertaken in all car parks using the 'Laboratorio Caminos Santander' permeameter and the Cantabrian Portable Infiltrometer. All results are presented together with the influence of surface and sub-base materials on water quality indicators using bivariate correlation statistical analysis at a confidence level of 95%. The polymer-modified porous concrete surface course in combination with limestone aggregate sub-base presented the best performance.