Utilization of sepiolite materials as a bottom liner material in solid waste landfills.

Landfill bottom liners are generally constructed with natural clay soils due to their high strength and low hydraulic conductivity characteristics. However, in recent years it is increasingly difficult to find locally available clay soils that satisfy the required engineering properties. Fine grained soils such as sepiolite and zeolite may be used as alternative materials in the constructions of landfill bottom liners. A study was conducted to investigate the feasibility of using natural clay rich in kaolinite, sepiolite, zeolite, and their mixtures as a bottom liner material. Unconfined compression tests, swell tests, hydraulic conductivity tests, batch and column adsorption tests were performed on each type of soil and sepiolite-zeolite mixtures. The results of the current study indicate that sepiolite is the dominant material that affects both the geomechanical and geoenvironmental properties of these alternative liners. An increase in sepiolite content in the sepiolite-zeolite mixtures increased the strength, swelling potential and metal adsorption capacities of the soil mixtures. Moreover, hydraulic conductivity of the mixtures decreased significantly with the addition of sepiolite. The utilization of sepiolite-zeolite materials as a bottom liner material allowed for thinner liners with some reduction in construction costs compared to use of a kaolinite-rich clay.

Re-usage of waste foundry sand in high-strength concrete.

In this study, the potential re-use of waste foundry sand in high-strength concrete production was investigated. The natural fine sand is replaced with waste foundry sand (0%, 5%, 10%, and 15%). The findings from a series of test program has shown reduction in compressive and tensile strengths, and the elasticity modulus which is directly related to waste foundry inclusion in concrete. Nevertheless the concrete with 10% waste foundry sand exhibits almost similar results to that of the control one. The slump and the workability of the fresh concrete decreases with the increase of the waste foundry sand ratio. Although the freezing and thawing significantly reduces the mechanical and physical properties of the concrete. The obtained results satisfies the acceptable limits set by the American Concrete Institute (ACI).

Geoenvironmental behavior of foundry sand amended mixtures for highway subbases.

The high cost of landfilling and the potential uses of waste foundry sands have prompted research into their beneficial reuse. Roadways have a high potential for large volume usage of the foundry sands. A laboratory testing program was conducted on soil-foundry sand mixtures amended with cement and lime to assess their applicability as highway subbase materials. The mixtures were compacted in the laboratory at a variety of moisture contents and compactive efforts and subjected to unconfined compression, California bearing ratio, and hydraulic conductivity tests. The environmental suitability of the prepared mixtures was evaluated by analyzing the effluent collected during hydraulic conductivity tests. Finally, required subbase thicknesses were calculated using the laboratory-based strength parameters. The results of the study show that the strength of a mixture is highly dependent on the curing period, compactive energy, lime or cement presence, and water content at compaction. The resistance of foundry sand-based specimens to winter conditions is generally better than that of a typical subbase reference material. Laboratory leaching tests indicated that if these mixtures later come in contact with water that has been discharged directly to the environment (e.g., drainage through asphalt pavement), the quality of water will not be affected.

Use of natural zeolites as a landfill liner.

The purpose of this study is to investigate certain features of a novel material proposed to serve as an impervious liner in landfills. Various ratios of bentonites and zeolites (B/Z) compacted at optimum water content were tested to determine the strength parameters, permeability, pH, heavy metals and other properties. A B/Z ratio of 0.10 was found to be an ideal landfill liner material regarding its low hydraulic conductivity and high cation exchange capacity. The use of B/Z mixtures as an alternative to clay liners would provide potential to significantly reduce the thickness of base liner for landfills.