Environmental concerns arising from the over-dredging of sand have led to restrictions on its extraction across India, with direct economic impacts on concrete construction. A suitable environmentally friendly alternative to sand must be found to match the huge demand from the concrete construction industry. At the same time, waste plastic is rarely recycled in India, with as much as 40% left in landfill. The dumping of such materials which degrade at extremely low rates meaning they persist in the environment is a long-term environmental concern.
To tackle both issues, it is proposed to process waste plastic to create a partial replacement for fine sand in a novel mix for structural concrete. In this paper eleven new concrete mixes are evaluated to study five plastic material compositions, three groups of particle sizes, three different aspect ratios, and two chemical treatments and establish an appropriate choice of material to act as partial replacement for sand.
The results show that replacing 10% sand by volume with recycled plastic is a viable proposition that has the potential to save 820 million tonnes of sand every year. Through suitable mix design the structural performance of concrete with plastic waste can be maintained. This preliminary work was supported through funding from the British Council under the UKIERI (United Kingdom India Educational Research Initiative) programme for the project ‘Development of structural concrete with the help of plastic waste as partial replacement for sand’.
Cement manufacture in India reached 280 Mt in 2014 , second only to China. India exports only small volumes of cement, with internal demand for concrete being driven by a growing economy, growing population, and rising living standards . Mass extraction of sand, usually via river dredging, has been a problem in India for a number of years and is mainly fed by construction demand. A high court ruling in 2011 has virtually eliminated sand dredging  with the consequence of supply problems within India.
The Indian central pollution control board CPCB) reported in 2008 that approximately 15,000 tons of plastic waste is dumped every day in India . Non-biodegradable plastic waste is inert and breaks down very slowly once buried in landfill. Even if all of this plastic could be recycled, by-products of the recycling process such as polyethylene terephthalate (PET) sand are still required to be sent to landfill.
A solution to both of these problems is proposed by substituting fine sand in concrete mixes with processed waste plastic, which would otherwise remain as waste in landfill. This would not only encourage the collection and use of waste, but would provide alternative sources of fine material in place of sand in novel concrete mixes
This paper has demonstrated the potential for using recycled waste plastic in structural concrete mixes. At a replacement ratio of 10% by volume, this has the potential to save 820 millions tonnes of sand every year from being used in concrete mixes . This is equivalent to approximately 5% of total global annual sand consumption. A further benefit is to add value to waste plastic, helping to reduce the volumes sent to landfill in some countries. A reduction in sand demand from the construction industry would further support efforts to limit the effects of sand dredging in countries such as India and China, where significant sand volumes are extracted every year.
It is generally seen that substituting plastic into a concrete mix causes a decrease in compressive and tensile strength due to the poor bond between the plastic and surrounding matrix. Since failure in concrete propagates in tension, the poor bond around plastic particles leads to a reduced compressive and tensile strength. The use of a graded PET plastic matched to the size of the sand particles it replaces, and at a replacement of 10% by volume, gave the most promising overall performance. This material is furthermore cost effective to produce and comes widely available as a waste material in many markets. This paper has shown that simply shredding a PET material is sufficient processing to provide a viable alternative to sand.