2013 Session: 746

• Estimation of Spacing and Width of Shrinkage Cracks in a Road Base with Cement-Treated Recycled Demolition Waste
  Abstract: In this paper a simplified mechanical method for estimating the shrinkage crack spacing and width in a base layer is presented. The base material is cement treated mix granulate produced by using recycled crushed concrete and masonry aggregates (CTMiGr). This method is based on material properties of CTMiGr as measured in the laboratory and the average climatic conditions recorded in the Netherlands. The calculated crack pattern showed to be comparable to the crack spacing observed in the field. The masonry content is a key factor determining the shrinkage crack characteristics. With increasing the masonry content, the crack spacing becomes larger and the width of the primary cracks dramatically decreases. Compared to the effect of the cement content and the moisture content on the shrinkage crack pattern, the influence of the degree of compaction is less.
  Authors: Xuan, Dongxing; Houben, Lambert; Molenaar, André
  Authors: Xuan, Dongxing; Houben, Lambert; Molenaar, André
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Materials
  Session: 746
  Paper Number: 13-1494
• Laboratory Study of Fly Ash and Soil Mixtures for Sustainable Roadway Embankments
  Abstract: This paper describes a laboratory study for the mechanical properties and environmental suitability of mixing an off-specification type of fly ash with soil for roadway embankment/structural fill constructions. Fly ash has a potential to be beneficially used in roadway constructions, including embankments and pavement structural layers such as base/sub-base layers, shoulders, asphalt concrete, and Portland cement concrete, to create longer lasting and sustainable infrastructure. The study includes the optimization of the mixing ratio of fly ash and soil and the leaching potential of heavy metals in the fly ash for environmental impact assessment. The fly ash was collected from a utility power plant in Mississippi and local soil was used. The specimens compacted at various fly ash-soil ratios and water contents were tested for compaction properties, unconfined compressive strength (UCS), and direct shear tests. Results showed that the addition of fly ash into soil resulted in appreciable increases in the UCS and shear strength of the clay soil. After 14 days of curing, the UCS of the samples compacted from the fly ash-soil mixtures ranged between 940 kPa and 4300 kPa, whereas the soil alone had a UCS of 317 kPa. Friction angle increased by 2-3 times for different fly ash-soil mixtures. An optimum mixing ratio of 60% fly ash and 40% soil is recommended. Leaching of trace metals from the fly ash-soil mixtures were tested through batch leaching tests and column leaching test. The batch leaching test results show that the concentrations of the eight environmentally concerned metals in the leachates are all below the U.S. EPA regulatory levels for hazardous waste and the Mississippi Department of Environmental Quality regulation standards for beneficial use of fly ash. The column leach test results show that only Chromium and Barium are detectable in the effluent and are in very low concentrations.
  Authors: Li, Lin; Li, Yadong
  Authors: Li, Lin; Li, Yadong
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Materials
  Session: 746
  Paper Number: 13-1576
• A Comparative Study on Compressive Strength of Recycled Plastic Pin, Wood Lumber and Bamboo at Different Environmental Conditions
  Abstract: The use of Recycled Plastic Pin (RPP) to stabilize shallow slope failure offers a great economic and construction benefit and has marked a notable recognition in the engineering community. RPP driven into the soil slope face may go beyond possible slip surface that provides an additional resistance force along the slip plane and increase the factor of safety. Natural structural element, wood lumber and bamboo are available in abundance in developing countries and can be utilized for slope stabilization. The objective of the current study is to compare the compressive strength of RPP, wood lumber and bamboo under different environmental conditions. Based on the ASTM standards and field conditions, three different strain rates were applied during the study. Moreover, different environmental exposures were considered, 1) Acidic condition 2) Alkaline condition and 3) Neutral condition that represent different clayey soils in Texas. The test results indicated that wood and bamboo possesses higher peak strength at the normal condition compared to RPP. However, the strength of wood and bamboo were decreased by 65% and 71% respectively under different environmental conditions, in contrast strength reduction for RPPs was insignificant. Therefore, for the pinning of the slope in United States, the wood and bamboo could be a better solution compared to the RPP for short term stabilization. However, for long term stabilization, RPP could perform better due to its environmental resistant behavior. Bamboo is available in most of the developing countries and could be utilized for the slope stabilization in both short term and long term conditions.
  Authors: Khan, Mohammad Sadik; Hossain, Md. Sahadat; Ahmed, Faisal Shakib
  Authors: Khan, Mohammad Sadik; Hossain, Md. Sahadat; Ahmed, Faisal Shakib
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Materials
  Session: 746
  Paper Number: 13-4446
• Leaching Behavior of Aluminum, Arsenic, and Chromium from High-Carbon Fly-Ash Amended Highway Structural Fills
  Abstract: Coal power plants are very important in production of electricity in the United States. Approximately 50% of the electricity in Unites States is generated by coal combustion processes. As a result of this, large amounts of coal combustion byproducts, particularly fly ashes, are produced annually. Only 40% of these fly ashes can be reused successfully. The majority of the remaining landfilled or stockpiled fly ashes are high carbon fly ashes (HCFA). Continuous disposal of these HCFAs cause significant environmental and economical problems andhighway structures pose great potential for use of these landfilled HCFAs. While mechanical properties of the fly ash-amended highway base layers and embankments are deemed satisfactory, one key issue that precludes highway embankments built with fly ash is the potential for groundwater impacts caused by metals in the fly ash. To evaluate the environmental suitability, a series of column leach tests were conducted to determine the leaching of metals (Al, As and Cr) from fly ash amended soils. In addition, numerical computer modeling programs were used to predict the metal concentrations in soil vadose zone and groundwater. Results from laboratory tests indicated that metal concentrations increased with an increase in fly ash content and do not exceed the maximum concentration limits for drinking waters with few exceptions. Numerical modeling techniques predicted that leached metal concentrations decreased in the soil vadose zone with time and predicted concentrations of leached metals were below the environmental regulatory limits.
  Authors: Cetin, Bora; Aydilek, Ahmet H.; Li, Lin
  Authors: Cetin, Bora; Aydilek, Ahmet H.; Li, Lin
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Materials
  Session: 746
  Paper Number: 13-2251
  Practice-Ready: Yes
• Leaching of Alkaline Substances and Heavy Metals from Recycled Concrete Aggregate Used as Unbound Base Course
  Abstract: There is an increased trend towards use of recycled concrete aggregate (RCA) in construction. However, concerns have been expressed about the highly alkaline leachate from RCA in laboratory studies and associated high-pH leaching patterns and heavy metal release from RCA (e.g., Cr, Pb, and As). In this study, seven samples of RCA from a wide geographical area were investigated. Physical, chemical, and mineralogical properties were characterized, and laboratory column leaching tests were conducted. Two field test sites were installed and instrumented, one at the MNROAD facility in Minnesota and a second at surface parking facility on the campus of the University Wisconsin-Madison. The MNROAD site showed a neutral leachate pH between 6.5 and 8.0 after 7 months of service life (1.2 pore volumes of flow); however, pH from column leaching tests ranged between 11.0 and 12.5 and showed no decline over 100 pore volumes of flow (PVF). Due to the large difference between the field and laboratory results, two samples of RCA in Wisconsin, one from a recent demolition of concrete pavement (WR-F) and the other from an RCA stockpile with an age of 5-10 years (WR-SP), were used in the Wisconsin field site to verify the Minnesota data and investigate the long-term leaching of alkaline compounds and heavy metals. WR-F RCA started with a high leachate pH (12.6) and remained constant for the first 5 pore volumes of flow (PVF); however, WR-SP RCA started at a lower pH (7.3) but with a gradually increasing trend, up to pH = 11.9 for the first 2 PVF. The pH from both RCAs were higher than the USEPA drinking water standard. Arsenic, chromium, lead, and selenium in the RCA field leachate were also observed to be higher than the maximum contaminant level (MCL) for the USEPA drinking water standard.
  Authors: Chen, Jiannan; Tinjum, James M.; Edil, Tuncer B.
  Authors: Chen, Jiannan; Tinjum, James M.; Edil, Tuncer B.
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Materials
  Session: 746
  Paper Number: 13-2412
  Practice-Ready: Yes
• Leaching of Alkaline Substances and Heavy Metals from Recycled Concrete Aggregate Used as Unbound Base Course
  Authors: Chen, Jiannan
  Authors: Chen, Jiannan
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Materials
  Session: 746
  Paper Number: 13-2412
• Leaching Behavior of Aluminum, Arsenic, and Chromium from High-Carbon Fly-Ash Amended Highway Structural Fills
  Authors: Cetin, Bora
  Authors: Cetin, Bora
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Materials
  Session: 746
  Paper Number: 13-2251