Use of shredded tire chips and tire crumbs as packing media in trickling filter system for landfill leachate treatment

Scrap tire stockpiles are havens for pests and mosquitoes; thereby this poses a potential health risk. This research work was carried out in six stages to determine the use of scrap tire materials in trickling filter system to treat landfill leachate; 81 to 96% BOD₅, 76 to 90% COD and 15 to 68% NH₃-N from leachate were removed. Organic removal appears to be largely related with total dissolved solids reduction from leachate. Sudden increase in organic content of effluent from time to time could be attributed to biomass sloughing and clogging in trickling filters. However, tire crumbs exhibited more consistent organic removal through out the experiment. Because of high surface area of tire materials, a thick layer of biomass was attached on them and sloughed off at an interval of 21 days. Further research and practical applications are needed to establish usefulness of tire materials in this field.

Use of shredded tire chips and tire crumbs as packing media in trickling filter system for landfill leachate treatment

Scrap tire stockpiles are havens for pests and mosquitoes; thereby this poses a potential health risk. This research work was carried out in six stages to determine the use of scrap tire materials in trickling filter system to treat landfill leachate; 81 to 96% BOD₅, 76 to 90% COD and 15 to 68% NH₃-N from leachate were removed. Organic removal appears to be largely related with total dissolved solids reduction from leachate. Sudden increase in organic content of effluent from time to time could be attributed to biomass sloughing and clogging in trickling filters. However, tire crumbs exhibited more consistent organic removal through out the experiment. Because of high surface area of tire materials, a thick layer of biomass was attached on them and sloughed off at an interval of 21 days. Further research and practical applications are needed to establish usefulness of tire materials in this field.

Performance Evaluation of Modified Rubberized Concrete Exposed to Aggressive Environments

Recycling of the waste rubber tire crumbs (WRTCs) for the concretes production generated renewed interest worldwide. The insertion of such waste as a substitute for the natural aggregates in the concretes is an emergent trend for sustainable development towards building materials. Meanwhile, the enhanced resistance of the concrete structures against aggressive environments is important for durability, cost-saving, and sustainability. In this view, this research evaluated the performance of several modified rubberized concretes by exposing them to aggressive environments i.e., acid, and sulphate attacks, elevated temperatures. These concrete (12 batches) were made by replacing the cement and natural aggregate with an appropriate amount of the granulated blast furnace slag (GBFS) and WRTCs, respectively. The proposed mix designs’ performance was evaluated by several measures, including the residual compressive strength (CS), weight loss, ultrasonic pulse velocity (UPV), microstructures, etc. Besides, by using the available experimental test database, an optimized artificial neural network (ANN) combined with the particle swarm optimization (PSO) was developed to estimate the residual CS of modified rubberized concrete after immersion one year in MgSO4 and H2SO4 solutions. The results indicated that modified rubberized concrete prepared by 5 to 20% WRTCs as a substitute to natural aggregate, provided lower CS and weight lose expose to sulphate and acid attacks compared to control specimen prepared by ordinary Portland cement (OPC). Although the CS were slightly declined at the elevated temperature, these proposed mix designs have a high potential for a wide variety of concrete industrial applications, especially in acid and sulphate risk.

An Investigation on Mechanical Properties and Damping Behaviour of Hardened Mortar with Rubber Tire Crumbs (RTC)

Masonry wall has been used for ages as a part of non-engineered building structures, due to its ease of manufacture, strength, and stiffness to support gravity loads, but brittle enough to resist earthquake shake. One solution to increase its ductility when the earthquake shake stroked, ductile materials at bed joints that binding the masonries may apply. Mortar is a composite material consisting of sands, cement, and water that is generally used for masonry construction as a binder at bed joints. On the other hand, rubber has been used to isolate vibration of machinery because of its good damping behaviours. Those materials will be mixed and be elaborated to provide a ductile mortar binder at bed joints. This research aims to investigate the mechanical properties and the damping behaviour of hardened mortar with rubber tire crumbs at proportions of 0%, 40%, and 60%. Three types of specimens in forms of mortar cubes of 50x50x50 mm3, tensile specimens and mortar beams of 100x100x500 mm3 were tested to provide strength and damping behaviour. The addition of rubber tire crumbs in the mortar decreased the compressive strength, tensile strength, flexural strength and unit weight. Despite its weakness in the mechanical strengths, the addition of rubber tire crumbs could increase the damping behaviour significantly. This research recommended that mortar containing RTC is still appropriate use for non-structural component although it has low mechanical properties.

Mechanical Properties of Scrap Tire Crumbs-Clayey Soil Mixtures Determined by Laboratory Tests

Some laboratory tests, such as Proctor compaction test, direct shear and cyclic direct shear tests, consolidation test, and unconfined compression test, were performed on scrap tire crumbs-clayey soil mixtures to study the mechanical properties of the mixtures. The results show that (1) the maximum dry unit weight and the corresponding optimum moisture content of the mixtures decrease rapidly with the increase of scrap tire crumbs content (CSTC), showing good potential for using the mixtures as lightweight fill material; (2) it is not possible to prepare the mixture when CSTC exceeds 30% due to the occurrence of cracks in the mixture after removing from a mould; and (3) the shear strength of mixtures approximately increases by 20% when CSTC is up to 30%, while the residual strength decreases by 15%, compared with that of pure clayey soil. During shearing, the dilation of the mixtures occurs, particularly under the condition of a high CSTC and a low vertical pressure. Besides, the compressive strength and consolidation settlement of the mixtures decrease with CSTC increasing. The results indicate that it is possible for scrap tire crumbs used to improve clayey soil, which is suitable to act as a fill material.

New Formulations for Dynamic Behavior of Sand-Waste Tire Mixtures in a Small Range of Strain Amplitudes

This paper describes the results of a series of cyclic triaxial tests on sand - waste tire mixtures, and applications of genetic programming (GP) and stepwise regression (SR) for the prediction of damping ratio and shear modulus of the mixtures tested. In the tests, shear modulus, and damping ratio of the geomaterials were measured for a strain range of 0.0001% up to 0.04%. The input variables in the developed GP and SR models are the waste tire content (0%, 10%, 20%, and 30%), waste tire type (tire crumbs or tire buffings), strain, and confining pressures (40 kPa, 100 kPa, and 200 kPa), and outputs are shear modulus and damping ratio. Test results show that the shear modulus and the damping ratio of the mixtures are strongly influenced by the waste tire inclusions. The performance of the proposed GP models (R2 = 0.95 for shear modulus, and R2 = 0.94 for damping ratio) are observed to be more accurate than that of the SR models (R2 = 0.87 for shear modulus, and R2 = 0.91 for damping ratio).