Green material solutions for sustainable construction
Concrete is by far the most used construction material, with over 25 billion tonnes produced annually. This means that concrete’s constituent materials – aggregates and cement – need to be produced in immense quantities. “The production and transport of these materials leads to a large amount of CO2 being released,” explains GREEN-FRC Marie Skłodowska-Curie fellow Nikola Tošić from the Polytechnic University of Catalonia in Spain. “In fact, cement production alone is responsible for about 7 % of all man-made CO2 emissions.” The extraction and production of aggregates can also damage river and mountainous systems, and lead to significant waste production and soil contamination. As a result, the use of more sustainable materials has become an important area of focus. “Constant advances are being made here,” says Tošić. “However, the uptake and upscaling of these solutions by industry has proven to be the key bottleneck. The construction industry itself is very fragmented, and the margin of safety is significant given that lives are at stake.”
The GREEN-FRC project sought to address these challenges by creating completely ‘novel’ concretes with as many non-traditional components as possible. “The goal we set ourselves was to produce fibre-reinforced concretes with recycled and waste materials, for more sustainable urban infrastructure projects,” adds Tošić. To begin, the project team trialled different compositions of concretes with sustainable aggregates, binders and reinforcements. Materials included crushed concrete, limestone calcined clay and recycled macro-synthetic fibres. “This part of the project was experimental,” explains Tošić. “We batched different concretes, identified their fresh and hardened-state properties, and tested full-scale structural elements such as beams to find out their bearing capacity and behaviour under different loading conditions.” The research, which was undertaken with the support of the Marie Skłodowska-Curie Actions programme, also wanted to find ways of modelling and predicting the properties of such concretes. “This was done by building databases of experimental results and using, for example, machine learning algorithms to find dependencies between inputs (constituent material properties) and outputs (concrete properties),” adds Tošić. Numerical simulations were carried out, to enable the project team to see what was happening ‘inside’ various materials. This enabled them to measure virtually certain behaviours that could not be measured in experiments.
Unblocking industry bottlenecks
Tošić believes that the project has successfully demonstrated that new concretes made with alternative components and reinforcements are viable, and can be tailored for different structural purposes. “For example, we showed that macro-synthetic fibres, such as polypropylene, can be used as fibre reinforcements even under long-term loading conditions,” he remarks. “This was something that was not fully clear before the tests we carried out. We have also indicated how design codes should be changed to include these new materials.” The work done on design code development represents an important step forward towards the eventual adoption of new regulations. This is where the project could really help to unblock persistent industry bottlenecks.
Sustainable built environment
“The expertise and knowledge are there,” notes Tošić. “We just need to collaborate to implement them in practice.” In the meantime, the project team is actively collaborating with industry to transfer this knowledge to producers of fibre reinforcement, fibre-reinforced polymer bars and demolition companies. “Many collaborations were established during this project,” says Tošić. “Hopefully, the long-term legacy of this project will be a network of collaborating universities, institutes and companies, united around the goal of constantly improving the concretes we use to construct our built environment.”
GREEN-FRC, concrete, building, construction, cement, CO2, emissions, contamination, sustainable