This week demonstrated more than most that the cement sector is still innovating after celebrating 200 years since Joseph Aspdin's patent for ordinary Portland cement (OPC). Refining this valuable building material has taken us to the point where Heidelberg Materials announced that it will now recycle concrete from demolition waste, creating a by-product that will be reused in cement manufacture. In future, the concrete already in the world can be recycled to supply new building materials, contributing to a more sustainable construction industry.
As the industry looks to transition from Aspdin’s OPC to greener cements, what may seem like inspired solutions still need to benefit the environment. CEMBUREAU estimates that 400-500Mt of construction and demolition waste (C&DW) are generated in Europe annually and in the USA experts cite that up to 85 per cent of construction waste consists of concrete material. Creating circular economies for cement are a crucial next step in the industry's decarbonisation path. The value of the circular economy becomes more evident when we look at the decline in biodiversity around the globe and the mounting pressure on our natural aggregate and sand resources that need protecting.
Heidelberg Materials' ReConcrete innovations
Heidelberg Materials is one company seeking to develop sustainable solutions for C&DW. It has commissioned the first industrial concrete recycling facility at Katowice in Poland, which will recycle 100 per cent of demolition concrete into high-quality aggregates, sand and cement paste that could later be reused as sustainable building materials.
The system, which incorporates FCB's Rhodax® technology, can recover recycled concrete paste (RCP) from the demolition concrete, which can then be used as an alternative raw material in clinker manufacturing. In addition, Heidelberg Materials says RCP can absorb and permanently bind CO2.
Heidelberg Materials is also developing an enforced carbonation reactor to be installed at its Gorazdze cement plant, also in Poland. Known as the ReConcrete initiative, the reactor is directly integrated into the cement making process and is designed to carbonate recycled concrete paste. By sequestering CO2 from the flue gas, it eliminates the need for gas purification and CO2 separation steps required by other carbon capture technologies.
Grinding specialist, Christian Pfeiffer, is involved in the pilot project which uses a Reaction Rotary Durm and bag filter technology. The whole innovation is part of the Carbon4Minerals project co-funded by EU Horizon Europe enabling concrete to be reused to create low-CO2 composite cements to form a circular economy.
Why is there not more concrete recycling?
There has been plenty of innovation in the industry to date, particularly in the area of co-processing for example, but the use of demolition waste remains at a low threshold, even though, as CEMBUREAU states: "Concrete can be 100 per cent recycled – in new concrete or in other applications."
So why is this? CEMBUREAU argues that "recycling rates are low in many Member states due to a lack of efficient sorting and collecting of concrete and demolition waste (C&DW)." Another factor hindering the reuse of C&DW is the transport-related CO2 emissions, as the material is transfered from building site to recycling plant.
Furthermore, environmental concerns still need to be addressed with concrete recycling. A case study in the UK serves to illustrate this point. Local residents in Thame, Oxfordshire, recently raised concerns over large scale and noise pollution and dust created from a recycling facility reprocessing construction, demolition and excavation waste. It is not just the local issues of potential air pollution, but also the 100,000t of waste being brought to the site and some 80 HGV movements during the day.
While it is right that innovation should be applauded, the whole environmental and economic feasibility of a C&DW recycling project must be considered. The proximity of cement plants to waste recycling plants and demolition waste is a significant issue and the value of what can be recycled from the waste material is a major cost factor.
Meanwhile, the existing market for demolition waste is dominated by recycled concrete aggregates (RCA). This reduces consumption of virgin raw materials, which is of great benefit, but it doesn't create circular economies. Crushed concrete is merely combined with previously used aggregate to make a more cost effective aggregate material.
Initiatives like the Katowice recycling plant and Gorazdze's carbonated recycled concrete represent the future. They demonstrate that concrete recycling can offer a superior solution, providing high quality recycled aggregates while maximising the circularity and sustainability of cement and concrete. Widespread application of these technologies will maximise resource efficiency and support CO2 emission reduction efforts.