Our world is built from concrete.
Concrete shapes the world around us. The industry relies upon producers
supplying customers with materials that have certain properties.
Without effective standard test methods, this is impossible. At
the request of the European Committee for Standardisation, a project
team of 13 laboratories evaluated tests for a range of fresh and
hard concrete properties. Their results are being taken into account
in improved, revised standards for concrete testing.
Concrete: for most people, the first things that come to mind are roads or 1960s tower blocks, or maybe floors or paths. This all depends on their experiences in daily life. But concrete's uses are vast and they span our entire infrastructure: building foundations, hospitals, bridges, dams, reservoirs, power stations, air ports, water pipes, sewer systems and even underground transport systems. The list goes on and on and it is clear that much of modern life as we know it depends on concrete. The amount of concrete used each year is astounding - about 2,000 million tonnes. If we had the technology and the demand, this quantity could provide a pathway 1 metre wide and 10 cm thick to the moon and back, not once but 10 times.
An important industry
The industry behind the material provides jobs for many Europeans. The concrete sector has comprises the constituent suppliers - the people who produce cements, aggregates, additions and admixtures - as well as the producers who are known in the trade as the readymixed concrete industry.
Concrete has found its way into so many different applications because it's properties can be varied simply by changing its recipe. These properties have to be measured if the industry wants to continually improve the quality and test the performance of its wide range of products. Concrete tests are a crucial part of both product development and quality control.
Numerous laboratories from across Europe and around the world test concrete. Scientists in these organisations measure both properties important in the finished product, such as strength, and those affecting freshly mixed concrete. Examples of these properties include the ability to place fresh concrete in position and to ensure that it is properly compacted.
Concrete contracts -
a need for standards
Such properties and many others are so important to materials' and therefore to customer satisfaction. As a result, they appear in specifications and are often a condition of supply from a readymix company to a contractor. Standard testing methods that both the supplier and customer accept are key links in the supply chain. What's more, with accepted pan-European standards, suppliers can expand their markets and trade across borders more easily. The European Committee for Standardisation (CEN) is developing such standards, based on national and international standards.
A CEN task group was charged with the substantial task of drafting concrete testing standards to make them more precise and more effective. They came across several technical hurdles that were blocking progress. "The technical issues which needed attention were due to differences in national and international procedures and practices, which, because of the absence of relevant technical data, were not able to be resolved by discussion in committee," says Prof David Spooner of the British Cement Association. The debate hinged on how samples were prepared for testing, as well as the apparatus and procedures used to test both fresh and hard concrete.
Resolving the problems
The only answer to the question was to set up a project to evaluate the tests through an interlaboratory comparison. Prof Spooner coordinated this project.
The size and the scope of the test programme was beyond the scope of any single laboratory or country. Instead, it gained half of its financial suppport from the predecessor of the Standards, Measurements and Testing programme. The remaining funds came from the 13 laboratories and organisations who agreed to participate in the project.
The work began in December 1994 and continued until May 1997. During this time, the project team examined how the test results were affected by the size and shape of the test samples; the methods of compacting fresh concrete; the curing method; and the influence on test procedures or apparatus on the concrete's properties. Each partner made their own samples using locally available materials although they all agreed on the range of concrete specifications. The laboratories obtained remarkably consistent date and some factors which the partners had thought to be important turned out be less significant than others. They also found that in some cases, a different procedure leads to significantly different results.
The project group collated their findings and submitted them to CEN as draft standards which will soon be sent for formal voting. If they are accepted, they will become full standards for concrete testing. These improved standards will help producers to tighten concrete quality control. This would not have been possible without bringing laboratories together to cooperate in a project that crosses European borders.