CONCRETE – ITS GREENER THAN YOU THINK!
The Inland Branch was proud to host one international, and two South African speakers at its recent half-day mini seminar on sustainability in cement and concrete. Prof Arnon Bentur, Head of the International School of Engineering Technion, Israel Institute of Technology; Bryan Perrie, Managing Director of the C&CI and Dr Dhiraj Rama, Director of the Association of Cementitious Materials Producers (ACMP) attracted well over 100 delegates to the seminar, all keen to learn of the latest developments in the drive towards sustainable concrete.
Prof Bentur covered: sustainability considerations in the use of cement and concrete; strategies to improve the sustainability of construction with concrete; reducing the cement content in concrete - strength and durability; extending the influence of cement by inert and reactive fillers and Shrinkage and cracking.
In his concluding remarks he stated:
Reduction in cement content at a given w/c ratio, which is achieved by using HRWR, can enable 25% reduction in cement without compromising durability performance, as estimated by capillary absorption, chloride and carbonation ingress.
The potential for reducing cement content without detrimental effect on durability requires re-evaluation of the requirements in standards for minimum cement content to achieve performance in harsh exposure conditions.
Strength gains of up to 30% can be obtained when using 100 to 200 kg/m3 of non-reactive fillers in the size range of 18 to 28 mm. To maximize this potential there is a need to use HRWR not just to maintain the consistency but also, at the same time, to disperse the fillers to generate the filler effect.
Reactive pozzolanic fillers such as fly ash can be activated with respect to strength gains in concrete, even if blended cement is used.
The gains in strength for concretes with CEMI and CEMII are similar. This behavior in the concrete is different than the one observed in mortars (pozzolanic activity test), where superior behavior is obtained with the CEM I cement.
These trends suggest that there is a need to have another look at the relevance of the pozzolanic activity tests to concrete performance
The proper use of HRWR in concrete can mobilize effects which can facilitate portland cement clinker reduction, which would come on top of those achieved by reduction offered by using blended cements
Since the latter strategy can enable reduction in clinker content in cement by 30% without compromising concrete properties, the other influences, such as cement reduction in concrete and extension of strength by fillers, can enable a similar range of clinker saving.
The seminar continued with an overview by Dr Rama of the ACMP, its activities and responsibilities as part of the mining sector.
He stated that all members of the ACMP recognise that climate change poses a real global threat to sustainable development and that this requires a global solution requiring action from all countries.
As a result ACMP members aim to proactively adopt and/or develop mitigation and adaptation strategies to manage greenhouse gas emissions while incorporating national development goals.
Dr Rama continued by comparing data on greenhouse gas emissions with other industries and, the cement industry, at around 1% of gases emitted, was not a major polluter of the atmosphere compared to many other industries. However, he said, this did not mean that the local cement producers were complacent about emissions. A lot of work has already been carried out over the past few years, which has resulted in the CO2 emission per ton of cement produced to average around 30% less than it did 20 years ago.
He confirmed that the National Policy on Climate change was being supported by the ACMP by collaborating with Government through the Inter-Ministerial Committee on Climate Change, the Intergovernmental Committee on Climate Change which brings together the relevant national and provincial departments and organized local government, andother programmes managed by relevant Government Departments
The cement industry has its own plans and targets and the ACMP plans will place appropriate focus on the developmental objectives of the country. ACMP members have made significant progress in terms of technological and energy efficiency initiatives, and will now focus on the use of Alternative Fuel Resources to improve carbon footprint, and the promotion of extenders and extended cements.
Bryan Perrie, Managing Director of the Cement and Concrete Institute was the third and final speaker and provided delegates with a very comprehensive insight into the ‘greenness’ of concrete He began by quoting Norwegian, Gro Brundtland, Special Envoy on climate change to the United Nations, defining sustainability as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs”.
The triple bottom line concept was described as well as the green star rating system, the Skanska approach to sustainability, the life cycle approach, and C&CI’s web-based model designed to enable designers to input specific materials and calculate the Carbon footprint of a given concrete mix, thereby making it possible to find the optimum mix to minimise the environmental impact of a the concrete in a proposed project or structure.
Moreover, new research is producing exciting data on the re-absorption of carbon dioxide by hardened concrete. A Danish study has found that 50% of the volume of concrete will be ‘carbonated’ over 70 years of any building’s service life. This sponge effect makes concrete a more green choice than previously thought, emphasising how global sustainability can be achieved with concrete.
Concrete has an excellent ecological profile compared to other materials, Bryan Perrie continued”. “Its social contribution is immense,and economic performance good based on life cycle analysis.All things considered, concrete is virtually unequalled in combining the many unique qualities and attributes to make it the responsible choice in construction materials, balancing all the elements for increased sustainability”.
“In fact, concrete is much greener than you think”, he concluded.
In thanking the speakers for their presentations, Hanlie Turner, Inland Branch Chairperson, announced that it was the first occasion upon which a Past President of RILEM (Prof Bentur) and the President-Elect of RILEM (Prof Mark Alexander) were together at the Inland Branch of the Concrete Society.
She went on the thank the main sponsor of the event – PPC, and also the companies that had displays at the seminar – C&CI, Ulula Ash, Mapei, BASF and Lafarge SA.