Non-hazardous construction and demolition waste – including concrete, bricks, tiles and ceramics – represents over 10 % of total European waste (or about 335 million tonnes as of 2016). This material is recycled as unbound aggregate (pebble-sized chunks) for backfilling and road base, and sometimes as bound aggregate in concrete. Although the concrete recycling pathway offers the most added value, the nature of cement limits this option. A feasible alternative would be to collect the most suitable building waste via selective demolition, and then to recycle that in conjunction with new binders. This would yield a high-quality building panel compatible with circular economy ideals. The EU-funded InnoWEE project fleshed out this concept. Researchers developed three types of prefabricated, lightweight building panel in preparation for commercialisation. All panels foster energy efficiency and incorporate aggregate from recycled construction and demolition waste. The so-called ETICS-like panels are 40 x 90 cm and are intended for external use. The ventilated-facade panels are also intended for external use, while the radiant ceiling panels are for indoor use. The latter two are both 59.5 cm squares, which is a standard industry size. Researchers investigated various types of construction and demolition waste for suitability, development of the panels and performance assessment, in addition to commercial goals.
Geopolymer improves on cement
All panels feature aggregate made from selectively recycled building rubble, instead of natural alternatives that are unsustainable and difficult to obtain without environmental damage. The aggregate is bound with a new geopolymer developed by the project. Geopolymer binds the aggregate like cement, but has a better carbon footprint and is more durable. “The geopolymer layer also provides the finishing, with no need for additional rendering,” explains project coordinator, Adriana Bernardi. “The panels can be potentially produced with various surface textures, which can be protected with either a transparent or a coloured multifunctional paint.” Recycled construction aggregate comprises 50 % of the panels by weight. To this is added expanded polystyrene (EPS), for its thermal insulation properties and low weight. “Due to the time span of the project, EPS was practically the only possible choice without imposing additional and risky burdens on the project,” adds Bernardi. “Nonetheless, it is not the ultimate choice, and in the medium term we want to replace EPS with a more sustainable material, such as inorganic foams.”
Progress towards commercialisation
The products have been raised from technology readiness level 3/4 to level 6/7. Technical and environmental testing confirmed the panels’ excellent mechanical properties, resistance to freezing and other environmental factors, such as longevity. Testing of the exterior panels in various climates confirmed their superior thermal insulation and inertia compared to conventional options. The interior panels performed better than competitors as well, in both heating and cooling mode. The team will continue promoting the products in readiness for full commercialisation. Since geopolymer binders are new, European standards do not cover them. Therefore team members will be making applications through European technical assessment bodies, including the European Committee for Standardization and European Organisation for Technical Assessment, to overcome legislative barriers concerning the use of geopolymers.
InnoWEE, recycled aggregate, construction, geopolymer, cement, building panel, green building panels, demolition waste, energy efficiency, circular economy