Extolling the versatility of cementitious materials, scientists, academics and industry professionals exchanged notes on research areas and methodologies at Cement and Concrete Science 2011, held in London, UK, on September 12-13. Michael Bennett reports

The concrete and cement community swapped some solid backslaps at their annual get-together, held at Imperial College London, UK.

Illustrating how concrete and cement form a fundamental part of the world around us, Ellis Gartner from Lafarge, a French building materials company, said that ‘global construction needs could never be met without concrete’. He pointed out that the amount of concrete produced annually across the world has approximately the same mass as the Aletsch Glacier in Switzerland.

Given the material’s crucial role, the conference focused on the key areas that industry needs to address – material shortage and ensuring a future supply.

Gartner explained that contingency plans needed to be in place to ensure we can keep building if the materials used to make concrete and cement start to run out. ‘First you would look for materials that are extremely abundant and widespread, such as limestone, quartz, hydra aluminosilicates or basic aluminosilicate rocks...then abundant but localised materials like coal, iron ores, amorphous rocks and peridotes.’

Although concrete is a fairly low CO2 material compared to cut stone, the raw materials (cement, aggregate and water) make up a big chunk of the material’s carbon footprint. Cement is a crucial global commodity, with around 2.9billion tonnes of it produced each year (a figure that according to Novacem, is set to increase to 5billion tonnes by 2030), but producing one tonne of industry standard Portland cement typically emits 800kg of CO2. Gartner noted that ‘from an industrial perspective, we must take a pessimistic viewpoint that we will soon be made to reduce our CO2 [output]’.

Cementing change

Delegates at the conference heard a variety of innovative avenues being exploited by researchers to make the concrete and cement manufacturing process cheaper and more environmentally friendly.

Stephanie Barnett from the University of Portsmouth, UK, outlined her research into whether alkali activated binders could be made from fly ash sourced from power stations around the UK, as a sustainable alternative to cement that would turn waste into a useful building material ingredient.

Yusuf Ozturk from the University of Manchester, UK, presented a paper on the influence of supplementary cementing materials (such as fly ash, ground granulated blast-furnace slag and silica fume) on the water retaining characteristics of hydrated lime and Portland cement mortars. Ozturk explained how his team have been using a method based on the Sharp Front theory to explore the varying desorptivity of the supplementary materials, and how further research could lead to the increased use of sustainable binders in masonry mortars.

Nuclear waste disposal

Colum McCague from Queen’s University Belfast, UK, talked about how the nuclear industry uses Portland-based cement poured into steel drums to immobilise low-level nuclear waste, but pointed out that a high pH of the pore solution can trigger corrosion in certain waste metals such as aluminium and uranium, and that corrosion products are expansive and can lead to cracking, which causes a durability issue. He proposed the use of magnesium phosphate cement as a potential alternative for the encapsulation of nuclear waste containing aluminium, as it is rapid setting, has high short and long term strengths, a lower permeability and a greater resistance to sulphate attack. However, he added that the main disadvantage of using magnesium phosphate was excessive heat generation, which as some delegates highlighted, could pose safety problems.

Alan Maries from the Mineral Industry Research Organisation described a Technology Strategy Board-funded study carried out over three months into self pulverising cement. His team found that although this powder does not possess hydraulic properties, it can be activated by accelerated carbonation with CO2 gas extracted from the cement kiln to produce a strong cementitious material. He added that if the process were to be developed on a commercial scale, a possible saving of 30% in CO2 emissions could be achieved.

Green politics

However, although the concrete and cement community is not short of ideas, the crucial factor is finding a solution that is both sustainable and economically viable. ‘As soon as economic pressure builds up, people lose heart in cutting greenhouse gases’, said Gartner. Gartner highlighted the enormity of the task when trying to get a whole industry to change its practices, citing the OPEC oil embargo in the 1970s as an example of a world event that forced the industry as a whole to adapt. He added that in principle, the same could happen with global warming, however, ‘it was easier to understand [the reaction to the embargo] because it was cost driven. Greenhouse gas, however, is seen as a political issue and is harder to control.’

One company that seemed to be on the right track was Imperial College spin-out Novacem, which showcased a new cement based on magnesium oxide that they claim could offer a less carbon-intensive option. The product is manufactured from reserves of magnesium silicates, of which more than 20,000bn tonnes exist worldwide. The company also claim that no carbon emissions are released from the raw material – instead, it uses a non-carbonate feedstock, a low processing temperature and the end product results in the manufacture of magnesium carbonates that absorb CO2.

Playing to a different tune

Concrete guitarAs the conference drew to a close, things took a more lighthearted turn when Ruting Sun from Loughborough University, UK, showcased possible uses of concrete to make musical instruments. From Taiwanese flutes to Croatian sea organs, cementitious materials can be used to make a variety of weird and wonderful instruments. By precisely engineering the physical properties of concrete to control tonality, timbre and resonance, ‘concrete does actually have acoustic potential,’ said Sun. ‘It has the right material properties that can be adjusted by adding admixtures, aggregates etc. Modal parameters are the key factors to the vibration in the material.’

Concrete sea organSun also discussed how concrete could be used to make the built environment more musical, giving the example of a Croatian sea organ, designed by architect Nikola Basic for Zadar beach, the organ consists of 35 tuned pipes that create random but ethereal noises as the sea breeze blows into them, with the size and velocity of each wave determining the notes played.