Browsing by Author "Salifu T. Azeko"

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    Clay Mixtures and the Mechanical Properties of Microporous and Nanoporous Ceramic Water Filters
    (Journal of Materials in Civil Engineering, 2016) Ebenezer Annan; Kwabena Kan-Dapaah; Salifu T. Azeko; Kabiru Mustapha; Joseph Asare; M. G. Zebaze Kana; Wole Soboyejo
    This paper presents the results of an experimental study of the effects of clay mixtures on the mechanical properties of mixed clays with controlled levels of plasticity, prior to the firing of porous ceramic water filters for water filtration. Two clays with well-characterized initial compositions (Iro and Ewuya clays) are mixed with varying proportions to control their plasticity. The mechanical properties of the mixed and fired clays are then studied using a combination of experiments and theoretical models. These include the flexural strength, fracture toughness, Young’s modulus, and thermal shock resistance of fired clay mixtures. The results show that clay mixtures with 45–60 vol.% of Iro clay and 40–55 vol.% Ewuya clay can be used to produce clay composite filters with robust mechanical properties. The thermal shock resistance of a mixed clay filter (containing 50% Iro clay and 50% Ewuya clay) is also explained using a combination of elastic and viscoelastic crack-bridging models. The regimes for effective viscoelastic crack bridging are identified by comparing the relaxation times to the thermal shock durations. The implications of the results are then discussed for the mixing of locally available clays into robust micro- and nanoporous materials for applications in clay ceramic water filters.
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    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.
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    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.