Strength and Stiffness Properties of Green Lightweight Fill Mixtures

Approximately 250 million tires are discarded each year in the United States and 20 million in Canada. Finding sustainable ways to dispose these tires continues to be a problem throughout the world not only in North America. Disposal issues along with a continuing increase in tire production have resulted in an increase in tire stockpiles, 30 % of these tires end up occupying valuable landfill space. Tire Derived Aggregates (TDA) made from scrap tires have a compacted dry unit weight of 6.9 kN/m³ and a specific gravity of 1.06 making their use as lightweight fill material especially for highway embankments over soft soils very advantageous. Using TDA as fill material not only provide a new construction material but also help to provide sustainable solution for several environmental and economic problems. Previous studies have shown that the addition of Tire Derived Aggregates (TDA) to sand results in a fill material which is characterized by its higher shear strength compared to that of 100 % sand. While there have been several studies investigating various properties and situations involving TDA’s, there remain areas that still require exploration. The effect of soil/aggregate gradation on shear strength is one of particular interest. All of the research conducted to date investigated only the sand gradation mixed with uniform TDA gradation. None of the conducted research investigated the interaction between the gradation of the two materials and its effect on the performance of the fill mixture. The main goal of this paper is to gain an understanding of this interaction in aim of producing better fill mixtures with enhanced characteristics.