Getting more advanced high-performing concrete was the aim of an international conference this month, prodding the building materials industry to adopt standardisation for better sustainability. Anne Zammit reports.
Concrete is the second most consumed substance in the world after water. Yet in a small island state of confined spaces such as Malta, references to concrete are prone to draw “resistance from civil society” against “uglification”, according to the University of Malta’s Pro-Rector.
Speaking at the opening of a conference addressing the environmental impacts of concrete production, Carmen Sammut noted that, in local public opinion, concrete is often associated with environmental degradation.
“Such claims are often not completely unfounded,” she said, while commenting that the Sustainable Concrete Conference, set in the ‘baroque limestone city’ of Valletta, was “incongruous with what is taking place”.
Dr Sammut was referring to the widely-held view that too much construction is taking place on the Maltese islands.
Yet forecasts predict that populations worldwide will continue to flock to built-up areas, creating even more demand for buildings and related infrastructure. Eighty per cent of the world population is expected to be living in cities by 2050.
The demand for concrete is inevitably on the rise and, therefore, ensuring the sustainable use of the material supported with advances in research is a priority.
Three pillars
From the point of view of the concrete industry, the three pillars of sustainable concrete can be considered to be the constituent material of concrete and its properties, including workability of the mix at construction phase, the durability and long lifespan of structures and environmental performance.
Basic concrete is produced by mixing sand, water and cement, which is produced from limestone and clay. Environmental concerns circle around the high energy consumption required to mine, manufacture and transport raw materials for cement production and the release of greenhouse gases also linked to the production of cement. Around five per cent of global CO2 emissions come from cement plants.
Corrosion inhibitors and ‘self-healing’ products can repair cracks in concrete and prolong the lifespan of structures and buildings
Using different additives in concrete, including “cement replacing materials” from waste industrial by-products, can contribute to a reduction of carbon dioxide release by reducing the amount of cement needed in the concrete mix. This also leads to lower consumption of raw materials and less waste generated, as demonstrated by research conducted by Ruben Paul Borg at the University of Malta.
The difficulty usually lies in striking a balance, as changes in composition which minimise the carbon footprint may also have an impact on concrete properties and need to be supported with research.
The demands and expectations of a building or structure would have to be carefully considered at design stage before an appropriate mix is chosen.
Prickly pear concrete?
Adding nature-derived components to strengthen and improve the setting properties of mortars is being scientifically investigated.
One such study on the application of prickly pear extract in concrete mix was carried out at the University of Malta’s Faculty of the Built Environment in collaboration with the Department of Biology.
The combined action of carbon dioxide, salt, water and oxygen invading microcracks in concrete can lead to destructive corrosion of steel reinforcing rods and defective infrastructure. Real-time monitoring of chloride ion ingress could lead to better management of structures and specifications for a more adequate covering of concrete to extend a structure’s lifetime.
A joint study between UoM and Lithuania’s University of Technology tried out different proportions of waste by-products like ash to reduce the amount of cement used in the mix. It is known that recycled glass, gypsum board and materials generated by the concrete and construction industry itself all have potential.
The latest developments in acryclic-based plasticisers for concrete have allowed for improved material properties, especially important for tall buildings. Additives which reduce the ratio of water to cement in the concrete mix can also help prolong the life of structures.
Seeing a sustainable future in concrete construction, associate professor Luigi Coppola of the University of Bergamo spoke on maintenance and repair of existing structures as a way to meet the needs of a growing population while achieving better sustainability.
Corrosion inhibitors and “self-healing” products can repair cracks in concrete and prolong the lifespan of structures and buildings.
A presentation from the Technical University of Prague described a floating island made of fibre-reinforced concrete. Specifications for structures such as tunnels and wind turbine structures were addressed by a number of speakers.
Another UoM study looked at the effects of climate change on reinforced concrete structures, particularly corrosion caused by higher concentrations of CO2 in the atmosphere.
Prof. Hajek of the Czech Technical University in Prague maintained that the built environment needed to be “more resilient and better prepared for the new conditions”.
The International Federation for Structural Concrete (FIB) introduced some sustainable principles into its code of practice in 2010. Prof. Koji Sakai of the Japan Sustainability Institute augured that a more holistic design framework would be included in the upcoming Model Code 2020 for the industry.
Researchers at the European Laboratory for Structural Assessment recommended that environmental issues should be considered in the early stages of the design stage along with structural reliability and safety.
A life-cycle assessment would include looking at the environmental impacts of various concrete mixes.
“A consistent high quality of concrete is required in every batch and this can only be reached through standardisation,” urged Camci Ladin, technical development manager of the UK certifying body for reinforced steel.
The conference, coordinated by Ruben Paul Borg, at the Faculty for the Built Environment, UoM, was the first event held in collaboration with the International Federation for Structural Concrete (fib) in Malta.
The conference was also intended to promote discussion between the academic community and industry partners on sustainable concrete and was supported by Philip A. Tabone Marketing and BASF International, with the association of all the leading construction industry players and government entities in the Maltese islands.