The construction material reuse is a big issue across Europe. During the meeting in Gothenburg were presented two different projects in which recycle materials is the main purpose.
Reuse of Bricks
In Sweden a big number of buildings have an external layer of bricks that, in case of demolition, are usually disposed in a landfill.
This leads to some questions: can we reuse bricks? What will happen to bricks after demolition?
The opportunity to focus on this topic came when three buildings were going to be demolished and rebuilt on the same area. The push to study the bricks reuse is given by the city of Gothenburg sustainability plan, that includes the circular use of materials.
Circular construction is not so easy to put in practice, because there are some barriers preventing the diffusion of re-used materials and also many questions about how to disassemble and reassemble the materials, about legal aspects and the economical feasibility.
To answer those questions, in the specific case described above, it was carried out a preliminary study, than a more detailed analysis and finally a design concept with cost and benefits analysis.
The existing building was constructed in 1960’s and the inner walls were built with low weight concrete with uranium, so there were radon radiations problems. An attempt to solve the problem was done using mechanical ventilation but it didn’t work, so the only solution was to demolish and rebuild as new.
To be sure about the safety to reuse the bricks that were previously in contact with the radon some tests were carried out using a Geiger meter.
It was also done a visual check in building and it emerged that the bricks were in an overall good conservation state. A further investigation was done when 20 bricks were removed and send to test. The result was that the compressive strength is higher than normal bricks.
In this case the mortar composition is 50% lime and 50% cement, so it’s a quite strong mortar. Anyway the mortar came out from the bricks quite easily. The difficulty to remove the mortar could depend form the brick itself and their original production temperature.
They compared the standard demolition with a careful demolition (circular saw). With the standard one about 50-75% of bricks is reusable, while in careful demolition 100% of bricks are reusable. The cost in the first case is about 1-25.€/brick while with the careful demolition is about 2-4€/brick. Generally the normal cost for new bricks is 0.6 €/brick. In both cases there is a saving because the cost of transport to the landfill is saved.
It’s important that the reuse of materials must be a clear focus from the beginning. It was important also to have a material warranty.
Some simulation on the total building cost were studied increasing the cost of the façade, the result is that the total increase is relatively small, if you double the brick cost the total increase is about 0.9%.
According to LCA if you reuse 1m2of bricks you save 40kgCO2eq and 600MJ of energy. Translating this into the real building, that it’s not fully covered by bricks, it means reducing the carbon footprint of the building by 5-10%.
Choosing the deconstruction method means different % of reused material.
For the economical comparison the baseline was “no reuse”. Compared with this you have no landfill cost, no material cost, no transportation, but you have cleaning and preparation of the bricks. For the cleaning is very difficult to define the price, since it should be done manually. There is also big uncertain about the cost for the careful demolition.
In the Gothenburg project some design concepts were developed, covering different area of the new building with reused bricks. With design 1 the result is between 0.2% cost reduction to 0.02% increase and about 1% CO2 reduction. With design 2 from 0.4% reduction to 0.4% increase in costs and 1.4% CO2 reduction.
For future developments, the use of digital technology can help material reuse, for example the “material passport” could include information about the material characteristics.
Procurement requirements for circular flows in the construction and demolition process
The city of Gothenburg is developing a recommendation for procurement requirements for circular flows in the construction and demolition process. The main purpose is to speed up the transition to circular economy in the construction sector, aiming to reduce waste and need of new primary material. The project is about buildings, not infrastructures, and regards only housing and offices, schools and other facilities are excluded. The aim is also to increase the knowledge and awareness about how to formulate requirements in public procurements.
Today ¾ of the original value of material is lost after the first use of materials. City of Gothenburg decided in 2014 to reduce household waste by 30% before 2030 compared to the 2010 level. An average citizen of Gothenburg produces 8tons of CO2 per year.
In order to define requirements it was first described a potential scenario for 2030.Today’s situation was observed and a research for good examples in procurement was carried out. Then was carried out a gap analysis, to see what was missing to reach the 2030 scenario. From this gap analysis a recommendation to go from now to 2030 scenario was developed.
There are many different projects in this area at the moment. They invited a lot of different stakeholders to discuss. The communication with the stakeholders begun in the early stages of the process in order to have a better involvement.
The gap between now and the 2030 scenario is huge, but must be filled. The stakeholders must be prepared in a couple of years to the new requirements.
At the moment there is a lot of recycling of demolition material, but a lot of effort should be done already in the early stages, during the design. It’s possible to start already now to make buildings ready for deconstruction and easy repair, people just have to ask for it in the design procurement. A good approach is not to “request” but to cooperate with providers, starting with the architects.