A. Ragab Ewais

Bio: A. Ragab Ewais is an academic researcher. The author has contributed to research in topics: Geomembrane & Leachate. The author has an hindex of 1, co-authored 1 publications receiving 38 citations.

Antioxidant Depletion from a High Density Polyethylene Geomembrane under Simulated Landfill Conditions

Abstract: Accelerated aging tests to evaluate the depletion of antioxidants from a high density polyethylene geomembrane are described. The effects of temperature, high pressure, and continuous leachate circulation on the aging of geomembranes in composite liner systems are examined. The antioxidant depletion rates (0.05, 0.19, and 0.41 month−1 at 55, 70, and 85°C , respectively) obtained for the simulated landfill liner at 250 kPa vertical pressure are consistently lower than that obtained from traditional leachate immersion tests on the same geomembrane (0.12, 0.39, and 1.1 month−1 at 55, 70, and 85°C ). This difference leads to a substantial increase in antioxidant depletion times at a typical landfill liner temperature ( 35°C ) with 40 years predicted based on the data from the landfill liner simulators tests, compared to 15 years predicted for the same geomembrane based on leachate immersion tests. In these tests, the crystallinity and tensile yield strain of the geomembrane increased in the early stages of ...

Short- and long-term leakage through composite liners. The 7th Arthur Casagrande Lecture1 1This lecture was presented at the 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, Toronto, Ont., October 2011, and a pre-print appeared in the conference proceedings.

Abstract: The factors that may affect short-term leakage through composite liners are examined. It is shown that the leakage through composite liners is only a very small fraction of that expected for either...

Aluminum Waste Reaction Indicators in a Municipal Solid Waste Landfill

Abstract: Subtitle D landfills may contain aluminum from residential and commercial solid waste, industrial waste, and aluminum pro- duction wastes. Some aluminum-bearing waste materials, particularly aluminum production wastes, may react with liquid in a landfill and cause uncontrolled temperature increases, significant changes in gas composition and pressure, nuisance odors, and changes in leachate composition and quantity. Such reactions may also cause degradation of leachate quality (e.g., increased ammonia, sodium, potassium, chloride, and TDS concentrations), combustion of the surrounding waste, damage to engineered components (gas collection systems, leachate collection systems, and liner system materials), and slope instability. Temperatures exceeding 150°C (300°F), generation and accumulation of undesirable explosive and toxic gases (e.g., hydrogen, acetylene, ammonia, carbon monoxide, and benzene), and gas pressures exceeding 210 kPa (30.5 psi) have been observed. Water from leachate recirculation, precipitation, the waste, or groundwater infiltration can initiate the exothermic reaction if aluminum production wastes are present. This paper uses a case history to illustrate some indicators of an aluminum reaction and problems that can develop from such a reaction in a Subtitle D landfill. DOI: 10.1061/(ASCE)GT.1943-5606.0000581. © 2012 American Society of Civil Engineers. CE Database subject headings: Solid wastes; Leaching; Aluminum (chemical); Waste disposal; Landfills. Author keywords: Solid waste; Leachate; Stability; Leachate recirculation; Aluminum; Exothermic chemical reaction; Waste disposal; MSW; Subsurface fire.

Service Life of HDPE Geomembranes Subjected to Elevated Temperatures

Abstract: Subtitle D landfills may experience elevated temperatures for a variety of reasons such as hydration of combustion ash, waste biodegradation with and without leachate recirculation, aluminum production waste and combustion ash reactions, and wastes received with elevated temperature. Elevated temperatures can reduce service life or effectiveness of high density polyethylene (HDPE) geomem- branes by accelerating antioxidant depletion of geomembranes and polymer degradation. A case history is presented to illustrate the potential effects of elevated temperatures and time-temperature history on a HDPE geomembrane and the associated reduction in service life or effectiveness. The geomembrane service life was influenced by the peak temperature, e.g., 60-80°C, the duration of peak temperatures (time-temperature history), and the time to complete antioxidant depletion. This paper also discusses possible criteria for assessing the service life of geomembranes, such as applicable engineering properties, locations for service life assessments, definitions of geomembrane service life, and measures that could be adopted if service life were reduced significantly. DOI: 10.1061/(ASCE)HZ.2153-5515.0000188. © 2014 American Society of Civil Engineers. Author keywords: Aluminum; Dross; Heat generation; Exothermic chemical reaction; Landfill fire; Landfill gas; Elevated temperature; Geomembranes; Geosynthetics; Durability; Waste disposal; Service life; Municipal solid waste.

Brittle rupture of an aged HPDE geomembrane at local gravel indentations under simulated field conditions

Abstract: The susceptibility of a 1.5 mm thick high-density polyethylene geomembrane to brittle rupture from long-term stress cracking in a simulated municipal solid waste landfill liner is examined. The geomembrane was pre-aged in a leachate at 85°C to lower the notched constant tensile load stress crack resistance of the geomembrane to about 75 h. The aged geomembrane was then used as part of a composite liner system in geosynthetic liner longevity simulators (GLLSs) with a geosynthetic clay liner and sand foundation layer below the geomembrane and a 560 g/m2 geotextile protection layer and 50 mm drainage gravel above the geomembrane. The GLLSs allow the simulation of field conditions including elevated temperatures, overburden pressure, leachate circulation, and composite liner exposure conditions. The geomembrane experienced brittle rupture on the side slopes of the local gravel indentations for temperatures between 55 and 85°C. The higher the liner temperature, the shorter the time to rupture and the...