Making concrete bricks out of recycled polystyrene

More than 50 000 tonnes of raw material virgin polystyrene is imported into South Africa every year. The versatility of polystyrene enables it to be manufactured into many products, ranging from food packaging to insulation in cooler rooms and even hangers.

Over 5 000 tonnes of polystyrene was recycled in South Africa last year, some of which is used in building and construction innovations such as lightweight concrete. This figure is significant keeping in mind that virtually no separation at source is available to consumers in South Africa. Although there is a long way to go, a large demand for material drives recycling initiatives.

The Polystyrene Association of South Africa (PolySA) represents the entire value chain of the country’s polystyrene industry, including raw material suppliers, manufacturers of expanded polystyrene and high-impact polystyrene, recyclers and retailers. PolySA has been supporting lightweight concrete projects since 2012 and has seen the market experience tremendous growth over the past six years. One of the fastest growing markets for recycled polystyrene is lightweight concrete blocks and screeds, made from an aggregate mixed with cement and additives, which are insulated, soundproof, fireproof and water-resistant.

Envirolite Concrete, an associate member of PolySA, was formed in 2018 after more than six years of developing its lightweight recycled polystyrene concrete blocks and screeds. One of the largest suppliers of such innovative alternative building products to the South African construction industry, the company produces a unique lightweight concrete block that is also the first in South Africa to utilise the tongue and groove interlocking system to improve walling alignment and speed up block installation.

“These concrete products are not only environmentally friendly and easy to install but are used for a wide range of walling installations, from load-bearing walls to infill walling for highrise concrete frames,” says Hilton Cowie of Envirolite Concrete.

Lightweight concrete blocks and screeds have already been used in various large commercial projects such as the Trumpet Towers in Johannesburg, the BMW Pavilion and Zeitz MOCAA in the V&A Waterfront, Baywest Mall in Port Elizabeth, and the Gautrain station in Sandton.

Envirolite has recently expanded its product range, with the introduction of the Eco Green Wall Block, made from a mixture of recycled polystyrene and cement for use in the construction of soil-based, living walls.

The lightweight concrete block

A green wall is a wall partially or completely covered with greenery that includes a growing medium, such as soil, water or a substrate. The Eco Green Wall Block is made from recycled polystyrene and cement for the construction of soil-based living walls.

The concept of living walls or vertical gardens has been practised for ages in many parts of the world. Ivan van der Walt from Abrus Enterprise developed the Eco Green Wall system as an answer to the need for a system that is durable, easy to install and maintain, and that would be suitable for all areas, especially areas with low humidity and rainfall.

Cowie says that living walls form an integral part of the movement towards sustainable, environmentand human-friendly developments. The use of recycled polystyrene in creating the Eco Green Wall ensures good moisture retention, enhances the cooling effect on the environment, offers excellent acoustic properties and reduces pollution through recycling. These walls are also lightweight and fire-resistant.

According to Cowie, there is a growing trend to establish living walls in urban and rural spaces. “These walls positively change the character of these spaces into more human-friendly and ecologically sustainable environments,” he says.

With living spaces becoming smaller in urban developments, the vertical plane presents an ideal opportunity to develop gardens upwards to soften these hard surfaces, leaving the horizontal spaces to be utilised for movement, seating and entertainment.

Enclosed planting cavities ensure longer moisture retention and less frequent watering. Walls can be painted in order to display the green foliage better.

Some of the benefits are:

1. climatic control – decrease extreme temperature fluctuations of building and the environment

2. Acoustic control – noise reduction

3. Improve air quality in urban environments

4. Commercial and DIY use – ideal for ornamental plants, strawberries, herbs, indigenous plants, grasses and food gardens.

The goal of a living wall is to imitate the ecology of a natural rock face by creating a suitable environment that can sustain a balance between plants and other organisms in a vertical plane.

The wall can be constructed as free-standing, against an existing wall, or back-to-back. Being easy to construct, walls can be built with mortar or tile adhesive and have a long, low-maintenance lifespan. Removable plant trays facilitate easy maintenance and can be irrigated with an internal drip system or manually.

Working towards sustainable environmental developments

Envirolite works closely with waste management services across South Africa to divert polystyrene waste from landfill, in order to be used in the manufacture of energy-efficient walling and flooring products.

The company recycles more than 1 000 cubes of waste polystyrene per month, helping to greatly reduce landfill volumes around South Africa, and plans to expand its polystyrene recycling efforts beyond South African borders.

Any form of expanded polystyrene can be used to manufacture the lightweight concrete. Items such as polystyrene cups or food trays and a wide range of polystyrene packaging are utilised. They can upcycle this waste into energy-efficient structures, making Envirolite Concrete the most sustainable building solution currently on the market.

Envirolite recently won Silver in the Inclusive category at the SAPRO 2018 awards, “for the substantial volumes of post-consumer polystyrene trays and cups recycled into a durable product with improved properties over its alternative concrete variants.”

The Inclusive category was for products manufactured from 100% post-consumer recyclate. Post-consumer recyclate comes with a packet of challenges, ranging from contamination issues to inconsistencies and supply. This means that winners in this category have managed to market a 100% recyclate product after extensive research and development trials and verification.

Envirolite is currently busy with three student residence apartment blocks in Johannesburg, as well as a large affordable housing project in Gauteng.