Study of recycled polyethylene plastic waste as binder in building block for greener construction.

Abstract

Plastic production has overtaken most man-made materials including metals and has long been under environmental scrutiny. Most plastic wastes are accumulated in landfills, natural environment and oceans. It is estimated that with the current trend of global production and waste management, approximately 12000 million metric tons of plastic waste will accumulate in landfills and in the natural environment by the year 2050. Plastics have very poor recycling rates, and their inherent menace is most pervasive in low-income, developing countries. This paper presents results of study on plastic waste as binder in mixtures of sand (fine aggregates) to produce building blocks for construction. Melted polyethylene plastic was mixed with sand (sandplast) in different proportions of 1:1, 1:1.5, 1:2, 1: 2.5 and 1:3 (plastic: sand). Test results include compressive, tensile and impact strengths, stress-strain response, fire resistance, water absorption and permeability of sandplast. The optimum mix ratio for the compressive, tensile and impact strength was 1:2. The compressive and tensile strength of sandplast blocks ranged from 4.8 to 7.4 N/mm2 and 3.3 to 7.2 N/mm2 respectively. These are greater than the respective values for sandcrete blocks produced in Ghana that generally vary from 1.4 to 3.5 N/mm2 and 0.1 to 0.3 N/mm2 . The static modulus of elasticity of sandplast averaged approximately 89.0, 311.5 and 197.7 N/mm2 for mix proportions of 1:1, 1:2 and 1:3. At temperatures below 80oC the strength properties and stability of sandplast blocks remained unchanged. When immersed in water, sandplast blocks were found to be insoluble in water. The coefficient of permeability of sandplast averaged 4.6 x 10-4 , 8.2 x 10-4 and 21.8 x 10-4 cm/sec for mix proportions 1:1, 1:2 and 1:3 respectively.