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Expert commentary: developing the next generation of building materials to protect our environment

Dr Giovanni Pesce, discusses the impact the production of cement has on the world's carbon output and how our leading research is helping to find substitutes.

Giovanni -Pesce

In today’s world, the built environment contributes to around 30-40% of the UK’s total carbon footprint. In 2014, over 20% of this was total operational and embodied carbon footprint. In the same year, 55% of the total emissions (CO2eq) related to new constructions was due to products, 10% to transport and 20% to the construction itself1.

Therefore, one of the biggest policy changes we face now is reducing the carbon embodied in constructions (alongside changes such as decarbonising the heat supply).

 

Materials in the built environment

To give an idea of the scale of the problem, in 1998 only, the creation of the UK built environment required the use of 1.4Mt of glass and plastic, 3.9Mt of metals, 6Mt of bricks, 9.2Mt of wood and 98Mt of concrete1. Because of its use in construction, a material such as sand, which is used to produce glass, bricks and concrete and is very often overlooked by the general public, has become the second most used natural commodity on the planet after water. Sand has become such a precious commodity that it is literally being sold to Arab nations2! Sand for construction is obtained mainly from riverbeds and oceans and, consequently, in digging the sand we need for our buildings, we risk the destruction of entire ecosystems.

Natural sand can be replaced with other products such as crushed aggregate (e.g. crushed concrete) but changes do not happen in a day or a week. For instance, Norway’s construction industry took 20 years to move from natural sand and gravel to crushed aggregate. This is because the technical documents (i.e. standards) at the base of the sector need to be updated and, in order to do so, a significant amount of research, development and innovation projects have to be conducted3. At the same time, this new approach is being introduced to an industry which is traditionally resilient to changes.

Considering the amount of concrete used (10 times the second most used construction material, timber, and 70 times the least used material, glass) an important challenge that we face is reducing its usage and that of its most important component: cement.

The polluting effects of cement production

Cement production is the second most pollutant human activity today4; the cement industry currently accounts for about 6-8% of the annual anthropogenic global CO2 production5. The industry is monopolized by Portland cement, which is used in approximately 98% of concrete produced today. Portland Cement is an energy-intensive production. However, what is relevant is not the fact that cement production is pollutant per se (energy used in cement production has reduced over the years, reaching the point where it would be extremely difficult to reduce it further) but the amount of the material used to form concrete. According to World Cement, an online technical magazine for professionals and one of the ‘voices’ speaking in favour of this material: “Cement sector emissions cannot be reduced simply by changing fuels or increasing the efficiency of plants, but instead require the transformation of cement itself, either by blending it with alternative materials or by developing novel low-carbon cements”4.

Research for cement substitutes at Northumbria University

Research at Northumbria University aims to develop the next generation of cementitious materials: materials that can act as a binder in future mixes and have a reduced impact on the environment, people and economy compared to cement.

In order to provide an immediate substitute for cement, their research focuses on alternative materials, such as lime and gypsum, which have already been used in the industry and therefore do not face the limitations typical of brand new products (e.g. long testing, standard production etc). They aim to investigate the chemical processes at the base of these materials’ setting and hardening in the hope of modifying their characteristics and making them more suitable for the modern construction industry.

In recent research, isotopes were used as a way of pinpointing some of the chemical elements involved in the setting and hardening of lime, and we followed the evolution of the chemical products that embedded such elements through the whole process6. This produced a better picture of what happens during the initial stage of the setting and this will allow us, one day, to modify the process in order, for instance, to make it quicker.

Thanks to the experience gained during the above, we are also investigating the use of carbon fixed by lime during the setting as a method for measuring the age of the material, using the radiocarbon method. This research has important implications in the conservation industry and in archaeological research. We are at the forefront of the research in this area, with the development of an innovative method for sample preparation that reduces the risk of contamination from 14C-dead minerals (the main problem in all mortar dating techniques currently used)7.

We have also been investigating the characteristics of materials such as lime when at nanoscale. Nanolime is the general name of a limited group of commercial products developed and used in the conservation industry. These products are all made of nano-sized crystals of Portlandite (i.e. lime) that have not yet found a use in new constructions. However, the small size of the crystals give this material an edge over more traditional ones and can be exploited to develop, for instance, self-cleaning paints based on lime8.

Looking to the future, we aim to develop materials and technologies based on very simple and widely available minerals, such as calcium carbonate, that do not require high temperatures or milling processes (two of the most energy intensive manufacturing activities).

Our ultimate goal is to make the whole industry more sustainable for all of us: our environment, our economy and our society.

 

Dr Giovanni Pesce is one of the leading lecturers on our Royal Institution of Chartered Surveyors (RICS) accredited Surveying MSc, which explores a number of key topics across the built environment and construction sector, including Sustainable and Construction Technologies. We offer four distance learning pathways (Housing, Quantity Surveying, Real Estate and Building Surveying), each offering four intakes throughout the year and lasting two to four years.

 

1 Information from the UKGBC, website and from the article: Hurst, W. (2018). Built Environment Firms Must Act Now on Climate Change, Architect’s Journal, 8 October 2018. Accessed in October 2018.

2 Information from the article: n.a. (2017). How the demand for sand is killing rivers. BBC news, 3 September 2017. Accessed in October 2018

3 Danielsen S. W., Kuznetsova E., 2015. Resource management and a Best Available Concept for aggregate sustainability. In Prikryl R. Et al. 2016. Sustainable Use of Traditional Geomaterials in Construction Practice. Geological Society Special Publications, CPI Group:India, pp.59-70

4 Stewardson, L., 2018. The Path To Progress, World Cement, 5 November 2018. Accessed in November 2018.

5 Crow J.M. (2008). The Concrete Conundrum, Chemistry World, 27 February 2008. Accessed in October 2018

6 Pesce, G., Fletcher, I., Grant, J., Molinari, M., Parker, S. and Ball, R., 2017. Carbonation of Hydrous Materials at the Molecular Level: A Time of Flight-Secondary Ion Mass Spectrometry, Raman and Density Functional Theory Study. Crystal Growth & Design, 17 (3). pp. 1036-1044.

7 Pesce, G.L. Micheletto, E., Quarta, G., Uggè, S., Calcagnile, L., Decri, A., 2013. Radiocarbon dating of mortars from the baptismal font of the S. Lorenzo cathedral of Alba (Cuneo, Italy). Comparison with the thermoluminescence dating of related bricks and pipes. Radiocarbon, 55(2-3), pp. 526-533; Pesce, G.L., Ball, R.J., Quarta, G. and Calcagnile, L., 2012. Identification, extraction and preparation of reliable lime sample for the C14 dating of plasters and mortars with the method of “pure lime lumps”. Radiocarbon, 54(3-4), pp. 933-942.

8 Nuno, M., Pesce, G.L., Bowen, C.R., Xenophontos, P., Ball R.J., 2015. Environmental performance of nano-structured Ca(OH)2/TiO2 photocatalytic coatings for buildings. Building and Environment, 92, pp. 734-742.

 

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