Ecofriendly, ecoefficient and sustainable civil engineering work has been research with emphasis on adapting the byproducts of solid waste recycling and reuse to achieving infrastructural activities with low or zero carbon emission. The direction combustion model, the solid waste incinerator caustic soda oxides of carbon entrapment model (SWI-NaOH-OCEM) developed by this research has achieved a zero carbon release. This research adopted the literature search method to put together research results of previous works relevant to the aim of this present work. It has been shown that CO and CO2 emissions can be contained during the derivation of alternative or supplementary cementing materials used in the replacement of ordinary Portland cement in civil engineering works. In the overall assessment of the present review work has left the environment free of the hazards of CO and CO2 emissions. It was shown that these supplementary cementing materials derived from solid wastes improve the engineering properties of treated soft clay and expansive soils, concrete, and asphalt. Bio-peels, another form solid waste has been established as a good detoxificant used in treating wastewater. It has been shown that solid waste recycling and reuse is a hub to achieving ecofriendly, ecoefficient and sustainable infrastructural development on the global scale.
The menacing effects of global warming, rising cost of cement, high energy requirements for the production of cement, and the mitigation of environmental pollution have led researchers towards using locally available materials to partially replace cement in concrete or mortar. The concrete produced from such locally available material is called Green Concrete. Few researches have been reported on the usage of Oyster Shell Powder (OSP) to partially replace the Ordinary Portland Cement (OPC). However, none of those reports has reflected the response of such Green Concrete made with Oyster Shell Powder to Splitting Tensile load. In this research, OPC is partially replaced with OSP at the rate of 0%, 5%, 10%, 15%, 20% and 25% in concrete. A total of 72 number of cylindrical metal moulds of 150mm diameter and 300mm height are used to cast the concrete, demoded after 24 hours and cured for 3, 7, 14 and 28 days with three replicates for each curing age and each replacement percentage. The properties of fresh and hardened concrete were quantified. The results show that the increase of OSP from 0% up to 25% delays the initial and final setting times of cement paste by 25mins and 40mins respectively. It also improves workability by an additional slump of 19mm. In addition, the Splitting Tensile Strength decreased from 1.706N/mm2 for 0% replacement to 1.011N/mm2 for 25% replacement after a three-day curing period, as well as from 2.076.N/mm2 for 0% to 1.388N/mm2 for 25% replacement, after a 28-day curing period. In as much as the Splitting Tensile Strength of concrete is known to be very low relative to its compressive strength; this study has reflected the extent of vulnerability of OSP-Cement concrete to tensile cracking and stress due to loads. Hence, this will result in safer design and loading of such concrete.
Keywords: Concrete, Cement, Oyster Shell Powder, Splitting Tensile Strength, Partial Replacement.
Pollution of our environment with wastes and the associated harm to our ecosystem and health is of great concern globally. In addition, the unabated mining of sharp sand for concrete with environmental degradation arising therefrom is worrisome. In the Niger Delta region of Nigeria, enormous quantities of oyster shells are being littered along the streets, riverbanks and landfills, after eating the fleshy part as meat. As a means of managing the waste and conserving sand, this study examines the properties of concrete made, using crushed oyster shells (COS) as partial replacement of sand. Sand was partially replaced in concrete with COS at the rate of 0, 5, 10, 15, 20 and 25%. The concrete matrix was cast in a metal cube mold of 150mm3 and cured for 3, 7, 14 and 28 days. A total of 72 cubes were cast in three replicates for each replacement level and each curing period, using a standard mix of 1:2:4 and water-cement ratio of 0.5. The results reveal that the addition of COS reduces the slump of the fresh concrete from 27 mm at 0% to 20 mm at 25%. The addition of COS up to 25% reduced the density of the concrete by 4.05%. The compressive strength slightly reduced as the percentage replacement increased from 0 to 25%. The findings recommend replacement not exceeding 15% that has true slump of 23.5 mm, lighter density of 25.17 kg/m−3 and compressive strength of 26.2 Nmm−2 which are good for concrete works. When sand is partially replaced with COS in concrete, we can confront the environmental degradation arising from indiscriminate disposal of oyster shells, as well as the depletion of sand as non-renewable component of concrete.
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