Browsing by Author "Winston O. Soboyejo"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Recycling of Polyethylene into Strong and Tough Earth-Based Composite Building Materials
    (Journal of Materials in Civil Engineering, 2016) Salifu T. Azeko; Kabiru Mustapha; Ebenezer Annan; Olushola S. Odusanya; Winston O. Soboyejo
    Polyethylene (PE) waste often piles up in the environment for up to 30 to 50 years, without complete degradation. This paper describes how PE waste can be used as a reinforcement in laterite bricks for sustainable building materials. The bricks are produced with different volume percentages (0–30 vol. %) of PE. The flexural/compressive strengths and fracture toughness values of the composite blocks are compared with those of mortar (produced from river sand and cement). The composite containing 20 vol. % of PE is shown to have the best combination of flexural/compressive strength and fracture toughness. The flexural/compressive strengths and fracture toughness values increase with increasing volume percentage of PE up to 20 vol. %, before decreasing to minimum values for composites with 30 vol. % of PE. The trends in the measured strengths and fracture toughness values are explained using composite and crack bridging models.
  • Thumbnail Image
    Item
    Statistical Distributions of the Strength and Fracture Toughness of Recycled Polyethylene-Reinforced Laterite Composites
    (Journal of Materials in Civil Engineering, 2016) Salifu T. Azeko; Kabiru Mustapha; Ebenezer Annan; Olushola S. Odusanya; Alfred B. O. Soboyejo; Winston O. Soboyejo
    This paper presents the results of combined experimental and theoretical studies of the statistical distributions of the strength and fracture toughness of recycled polyethylene-reinforced laterite composites for potential applications in building materials. The composites are produced with different volume percentages (0–30% v/v) and particle sizes (∼300±0.02, ∼600 ± 0.03, ∼900 ± 0.03, ∼1,200±0.02, ∼1,500±0.04, and 1,800±0.03  μm) of powdered polyethylene (PE) in a laterite matrix. The composites with ∼900±0.03  μm and 20-volume percentage of PE are shown to have the best combination of flexural-compressive strengths and fracture toughness. The statistical variations in the flexural-compressive strengths and fracture toughness are well characterized by the Weibull distributions.
  • Thumbnail Image
    Item
    Statistics of Flow and the Scaling of Ceramic Water Filters
    (Journal of Environmental Engineering, 2014) Ebenezer Annan; Kabiru Mustapha; Olushola S. Odusanya; Karen Malatesta; Winston O. Soboyejo
    According to the World Health Organization (WHO), there was an increase in the number of people that have access to safe drinking water between 2006 and 2010. Such trends can be accounted for partly by the increasing usage of ceramic water filters that can remove microbial pathogens from water. However, the initial flow rates in such filters are often limited to ranges between 1 and 3  L/h. In this paper, six frustum-shaped ceramic water filters of the same clay:sawdust composition were tested. Each ceramic water filter was filled with water and allowed to filter 20 times. Each time, the flow rate and water level were measured for a consecutive 12 h. Permeability values were estimated for each run of the ceramic water filters. Statistical analysis was performed on flow rates (in the first hour), mean flow rates, and estimated permeability values. The flow rate values (in the first hour) for the six ceramic water filters were found to be between 1.4 and 3.0  L/h. An effective permeability was obtained for ceramic water filters with a range of microscale and nanoscale pore sizes. The statistical variations in the flow rates and effective permeabilities were elucidated along with the potency of a multiple ceramic water filter system for scale-up studies in serving communities that need portable water.
  • Thumbnail Image
    Item
    Toughening Behavior in Natural Fiber-reinforced Earth-based Composites
    (MRS Advances, 2016) Kabiru Mustapha; Martiale G. Zebaze Kana; Winston O. Soboyejo
    This study presents a combine experimental and analytical investigation of the toughening behavior in natural fiber-reinforced earth-based composites. A specially designed single fiber pullout apparatus was used to provide aquantitative determination of interfacial properties that are relevant to toughening brittle materials through fiber reinforcement. The parameters investigated included a specially designed high strength earth-based matrix comprising of 60% laterite, 20% clay and 20% cement. The toughening behavior of whisker-reinforced earth-based matrix is analyzed in terms of a whisker bridging zone immediately behind the crack tip and interface strength. This approach isconsistent with microscopy observations which reveal that intact bridging whiskers exist behind the crack tip as a result of debonding of the whisker-matrix interface. Debonding with constant frictional stress was obtained and this formed the basis for the analytical model considered and the underlying crack-microstructure interactions associated with Resistance-curve behavior was studied using in situ/ex situ optical microscopy to account for the bridging contribution to fracture toughness. The effect of multiple toughening mechanisms (debonding and crack bridging) was elucidated and the implications of the results are considered for potential applications in the design of robust earth-based building materials for sustainable eco-friendly homes.