Physical and Mechanical Properties of Normal Concrete with Recycled Clay Products and the Plastic Fibres as Coarse Aggregates

Abstract

The quantities of clay product wastes in Kenya have been increasing significantly (approx. 45.9tonnes annually in Nairobi) without consideration for potential reuse or recycling increasing the risk to public health due to the scarcity of land area for dumping. This growing problem can be alleviated if new disposal options other than landfill can be found. Further, increased construction activity and continuous dependence on conventional materials of concrete are leading to scarcity of construction materials. This study aims at establishing the suitability and strength characteristics of clay product aggregates and plastic fibres as replacement for normal coarse aggregate in concrete. Clay product wastes originate mostly from broken or leftover bricks, whitewares, sanitary and kitchen ware. In this research, clay bricks were used to replace coarse aggregate in concrete, and varied with shredded plastic fibres. First, clay bricks and plastic fibres were prepared and graded in order to assess their suitability as aggregates. Then different concrete mixes were produced by replacing coarse aggregates with clay products and plastic fibres aggregates. The variations of the coarse aggregates were 20, 40, 60, 80 and 100% by weight for clay products and 5, 10 and 15% by volume of plastic fibres in C20 grade concrete. Different mixes of clay bricks and plastic fibres were prepared and used for making concrete specimens. Slump tests to ascertain the workability of the fresh concrete properties were carried out. Final test samples were cast and cured and their physical and mechanical properties assessed through density, splitting tensile tests, flexural tests, compressive tests and pull out force tests at 7and 28 days of curing. The effect of plastic fibres and clay bricks aggregates in concrete were studied and analyzed for physical and mechanical properties of the concrete. The results demonstrate there is great potential of use of waste clay products and plastic fibres as replacement in concrete. The optimum content of these aggregates were found to be 18.7 and 12.7% by weight and volume of clay bricks and plastic fibres, respectively. This resulted to reduction in concrete mechanical strengths by 59.8, 31.5, 44.2 and 31.1% for compressive strength, flexural strength, pull out force and splitting tensile strength respectively compared to control mix.However, the findings of this research are intended for applicationrequiring non-structural applications. These would therefore address issues such as environmental threats caused by wastes and leftovers, introducing them as alternative source of coarse aggregates in concrete, a conservation of natural resources.