| Currently, 2.5--3 billion scrap tires are stockpiled across the United States. Stockpiled scrap tires represent a waste of resources and a public health hazard. A large scale potential use of shredded scrap tires can be in soil stabilization, provided the mixtures exhibit the desired engineering properties and environmentally safe chemical characteristics.;Compaction characteristics, permeability, unconfined compressive strength, compressibility, and shear strength parameters were determined for two different soil types (a non-plastic silt and a low plasticity clay), dime different size ranges (1/4"--1/2" or 7 mm--13 mm; 1/2"--1" or 13 mm--25 mm; 1"--1.5" or 25 mm--38mm) of shredded tire material, and soil-tire mixtures containing 10% to 90% shredded tire material by weight. The results show that most engineering properties improve with the addition of shredded tire material. The friction angle increases with increasing tire content for silt-tire mixtures. For clay-tire mixtures, however, the friction angle increases up to 20% tire content and then decreases. The cohesion decreases with increasing tire content for both types of soil-tire mixtures containing (1/4"--1/2" (7 mm--13 mm) size shredded tire material. For soil-tire mixtures containing other two sizes of tire chips, the cohesion increases at 10% shredded tire content by weight, and then drops. The unconfined compressive strength decreases with an increase of shredded tire content for both soil types and all three size ranges of shredded tire.;In addition to laboratory investigations of soil-tire mixtures, a test embankment, containing 30% shredded tire material and 70% clay soil by weight, was constructed and monitored for settlement, slope stability, and leachate composition. The embankment construction revealed that a rototiller is the most effective way of mixing soil and shredded tire material, whereas a sheepsfoot roller is the best equipment for compacting the soil-tire mixtures.;The loss on ignition (LOI) test, bulk chemical analyses, and leachate analyses were performed for shredded tire material and soil-tire mixtures to evaluate the environmental impact. Results of the LOI test and bulk chemical analyses show that there are no significant differences between the three shredded-tire size ranges.;Three different methods were used to extract leachate samples: a laboratory method and two field methods (box samples and embankment samples). The results of leachate analyses from the laboratory samples indicate that concentration of barium from shredded tire material may exceed the maximum contaminant levels (MCLs) specified in U.S. Environmental Protection Agency's regulations.;Based on the engineering properties and chemical characteristics, soil-tire mixtures can be used as a construction material for roadway embankments, hydraulic barriers, and playgrounds, as well as a lightweight fill material. (Abstract shortened by UMI.)... |
