This paper presents the results of an experimental study of the bacterial-mediated biodegradation of linear low density polyethylene (LLDPE) by Serratia marcescens subsp. marcescens (S. marcescens marcescens) bacterium without prior exposure of the LLDPE to thermooxidative aging. Degradation promoted by supernatant from S. marcescens marcescens was also studied, and compared to that promoted by direct exposure to S. marcescens marcescens cells. The results show that the cell-free extracts degrade LLDPE faster than the S. marcescens marcescens. The mechanisms of degradation are also elucidated via Scanning Electron Microscopy, Differential Scanning Calorimetry and Fourier Transform Infra-Red Spectroscopy. These methods show that the S. marcescens marcescens and its supernatant both degrade LLDPE. There was also an increase in the concentrations of the carbonyl groups (new peaks) after the microbial degradation of LLDPE. The degradation process results in the formation and growth of microvoids. The latter are also found to coalesce to form larger defects with increasing exposure to supernatant/cell-free extracts or S. marcescens marcescens.

This paper presents the results of a study on the reliability and performance of the solar-powered street lighting systems installed at the African University of Science and Technology (AUST) in Nigeria, a hot and humid environment. The technical performance of the systems was studied using the following performance indicators: system energy yield, capture loss, as well as the system performance ratio while the reliability of the systems was examined using a model developed from the findings from the maintenance and fault diagnosis of the systems. The model was used to predict the total failure and survival probability of the systems using the Weibull distribution. The performance evaluation during the monitored period (February 2012 to January 2015) indicated that the performance ratios of the systems vary from 70% to 89% and the energy yields of the systems ranging from 2.87 h/day to 5.57 h/day. The results from the reliability analysis also showed that when the stress concentration factor around the notch between the cable terminals in the charge controller increases, the charge controller will become overheated, which in turn affected other components of the systems. The implications of this study are also discussed for the design and development of future solar-powered street lighting systems.

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This paper presents the results of a combined experimental and theoretical study of the strength, fracture toughness, and resistance-curve behavior of natural fiber-reinforced earth-based composite materials. The composites, which consist of mixtures of laterite, clay, and straw, are stabilized with controlled levels of Ordinary Portland cement. The compositional dependence of compressive, flexural/bend strength, and fracture toughness are explored for different proportions of the constituent materials using composites and crack-tip shielding models. The underlying crack-microstructure interactions associated with resistance-curve behavior were also studied using in situ/ex situ optical microscopy. This revealed evidence of crack bridging by the straw fibers. The measured resistance-curve behavior is also shown to be consistent with predictions from small-and large-scale bridging models. The implications of the results are then discussed for potential applications in the design of robust earth-based building materials for sustainable eco-friendly homes.

This paper presents the results of the experimental and analytical studies of the mechanical and thermal properties of laterite composites mixed with reprocessed low-density polyethylene waste (LDPE), calcium phosphate (CaP) and phosphogypsum wastes, and biochar to form brick composites. Bricks with mixtures of 20% by volume LDPE, 15% by volume CaP, and 15% by volume gypsum were shown to have excellent compressive strength, flexural strength, and fracture toughness. The composites with 1% by volume LDPE and 15% by volume biochar had the best blend of mechanical properties, such as flexural strength and fracture toughness, after sintering for ∼24 h. There was a linear association between the strength and the weight loss of the bricks. Scanning electron microscopy and optical microscopy images revealed evidence of crack bridging by LDPE particles. The laterite-LDPE composite mixed with 5%, 10%, and 15% by volume biochar had sintering temperatures of ∼850°C, ∼720°C, and ∼710°C, respectively, after undergoing softening, cold crystallization, and cooling.

This current research work combines both experimental and theoretical study of the impact of cement mortar reinforced with recycled polyethylene waste for applications in the construction industry. The work explores incorporating low density polyethylene (LDPE) waste into cement mortar to improve its fracture toughness and flexural strength with balanced compressive strength. Different volume fractions (0, 5, 10, 15, 20, 30, and 40%) of the powdered LDPE were mixed with cement and the density, compressive strength, flexural strength, and the fracture toughness were observed under different testing conditions. All specimens were tested after curing of 7, 14, and 28 days. The results show that there was [Formula: see text]6% increase in the fracture toughness at 5 vol. %, [Formula: see text]7% increase at 10 vol. %, and 24% increases at 20 vol. % of LDPE. Also, it was observed that the weight and compressive strength decreased with increasing volume fraction up to 40 vol. % of LDPE waste. The results for the survival/failure probability show that the PE-mortar composites with PE volume percentages up to 20 vol. % had the highest survival probability. The composite with this volume percentage can withstand crack up to 6 mm, with a survival probability of 0.6.