Hydrological and water quality performance of Waste Tire Permeable Pavements: Field monitoring and numerical analysis.

Permeable pavements can reduce the amount of surface runoff and peak flow rate and delay the occurrence of peak flow by allowing water to infiltrate underground similar to natural undeveloped catchments. Such suite of benefits of permeable pavements have made them one of the preferred stormwater control measures in most of the integrated land and water programs. Waste tire permeable pavements (WTPPs), as a relatively new permeable pavement technology, are designed with a surface layer made of up to 50% recycled tire particles. This study aims to investigate the hydrological performance of WTPPs to divert surface runoff and their impact on water quality. A large-scale trial in Australia was constructed and a comprehensive field performance monitoring program including double-ring infiltrometer tests and water quality testing was conducted to evaluate the performance of WTPP in real field conditions. Quality assurance tests on samples of the WTPP surface layer were conducted for permeability in the laboratory, and numerical simulations were done to estimate the surface runoff and investigate the sensitivity of the results to important design parameters. The physically-based models used for numerical simulations were developed in MUSIC X by replicating the layers of the constructed permeable pavement system as well as the impervious part of the trial site. The results indicated that the constructed system is capable of mitigating the surface runoff from the studied site, although only 25% of the discharge area was covered with WTPP. The infiltration rate of the WTPP over nine months with and without maintenance was studied. The results revealed that the infiltration rates even in areas without maintenance after nine months were found to be above the recommended values from ASCE permeable pavements task committee, but lower than the areas that were regularly maintained highlighting the importance of a regular maintenance regime for permeability recovery over time. Water quality tests were done on samples taken over a 17 month-long period indicating that the WTPP system successfully reduced most of the studied pollutants and chemical indicators, including most of the heavy metals, total suspended solids (69%) and turbidity (88%) by physically filtering the water.

Improved Shear Strength Performance of Compacted Rubberized Clays Treated with Sodium Alginate Biopolymer.

This study examines the potential use of sodium alginate (SA) biopolymer as an environmentally sustainable agent for the stabilization of rubberized soil blends prepared using a high plasticity clay soil and tire-derived ground rubber (GR). The experimental program consisted of uniaxial compression and scanning electron microscopy (SEM) tests; the former was performed on three soil-GR blends (with GR-to-soil mass ratios of 0%, 5% and 10%) compacted (and cured for 1, 4, 7 and 14 d) employing distilled water and three SA solutions-prepared at SA-to-water (mass-to-volume) dosage ratios of 5, 10 and 15 g/L-as the compaction liquid. For any given GR content, the greater the SA dosage and/or the longer the curing duration, the higher the uniaxial compressive strength (UCS), with only minor added benefits beyond seven days of curing. This behaviour was attributed to the formation and propagation of so-called "cationic bridges" (developed as a result of a "Ca2+/Mg2+ ⟷ Na+ cation exchange/substitution" process among the clay and SA components) between adjacent clay surfaces over time, inducing flocculation of the clay particles. This clay amending mechanism was further verified by means of representative SEM images. Finally, the addition of (and content increase in) GR-which translates to partially replacing the soil clay content with GR particles and hence reducing the number of available attraction sites for the SA molecules to form additional cationic bridges-was found to moderately offset the efficiency of SA treatment.