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Cements – standards, third party certification, and chromium (VI)

Cements in the UK aren’t as complex as they could be, but they are a lot more sophisticated than they used to be.

Artificial cements have undergone many changes since Joseph Aspdin patented Portland cement in 1824. By 1838 production of Portland cement was well underway in Gateshead and London. In those early days of production, low temperatures were used for calcining the raw materials and consequently the cements performed inconsistently. In the 1860s an important change to production methods took place, when rotating horizontal kilns replaced vertical kilns. This allowed calcining at higher temperatures (around 1,450°C) and resulted in stronger cements with more consistent performance characteristics. By the 1920s ordinary Portland cement was the market leader, and from it stems the modern family of cements, manufactured by large multi-national corporations.

Standards

Today’s cements are highly engineered products, contributing to a range of strength, setting, durability and colour properties for concrete, grouts and mortars. Common cements are supplied to BS EN 197-1 Cement. Composition, specifications and conformity criteria for common cements. This defines 27 cements, including the composition of each product using the now familiar notations that commence with one of the five main cement types:

CEM I: Portland cement with up to 5% of minor additional constituents.
CEM II: Portland composite cement (e.g. Portland fly ash cement, comprising Portland cement with up to 35% of siliceous fly ash).
CEM III: Blastfurnace cement (comprising Portland cement with up to 95% blastfurnace slag).
CEM IV: Pozzolanic cement (comprising Portland cement with up to 55% of pozzolana).
CEM V: Composite cement (comprising Portland cement with up to 80% of, e.g. blastfurnace slag and fly ash).

There are several cements outside the scope of BS EN 197-1. Some, like sulfate-resisting Portland cement to BS 4027 and pozzolanic pulverized-fuel ash cement to BS 6610, may eventually be brought into the fold. Others, however, will remain outside the scope of BS EN 197-1. They include:

Blastfurnace cements to BS EN 197-4 Cement. Composition, specifications and conformity criteria for low early strength blastfurnace cements. These are CEM III cements with strengths lower than those permitted for BS EN 197-1 common cements.
Masonry cement to BS EN 413-1 Masonry cement. Composition, specifications and conformity criteria.
Cements which harden due to the hydration of calcium aluminates (e.g. high alumina cements to BS 915-2) rather than the hydration of calcium silicates, as in Portland cements.

In reality, the range of cements produced by UK manufacturers is relatively small. A look at the products lists for bagged cements, ignoring differentiation by strength class, reveals a range of about five common cements to BS EN 197-1: CEM I Portland, white Portland and rapid-hardening Portland cements, and CEM II Portland fly ash and Portland limestone cements. Add to these sulfate-resisting cement and masonry cement, and the odd special cement (e.g. rapid setting), and you get a range of about eight cement products. However, the potential remains for a wider range of BS EN 197-1 common cements to find their way onto the UK market.

Certification

When it comes to third party product certification of cements, it is interesting to see that the UK cement manufacturers affix the CE mark to their cements to BS EN 197-1 but do not add the BSI Kitemark, even though the scheme is available for common cements. The Kitemark is of course a voluntary quality mark, but the main reason for its exclusion by manufacturers in this case, is that it does not provide any additional information to the user that is not already covered by the CE mark. Another is its cost. However, manufacturers do use the Kitemark for cements outside the scope of BS EN 197-1, such as sulfate-resisting Portland cement to BS 4027.

Strictly speaking, CE marking is not a quality mark but, in the case of common cements to BS EN 197-1, it is almost indistinguishable from one. This is because such cements are subject to a level 1+ Attestation of Conformity – the highest level of control under the EU Construction products Directive. This means that cements conform to both the technical specification (verified by an independent third party) and regulatory requirements.

Chromium (VI) Directive

Finally, no discussion on cement can avoid mentioning the EU Chromium (VI) Directive which was implemented in January 2005 via amendments to the COSHH Regulations. Its purpose is to restrict the chromium (VI) content of cement, and products containing cement, thereby minimizing the risk of chromate-related allergic dermatitis. This is one of two types of dermatitis which can arise from contact with wet cement, the other being the more common irritant dermatitis.

Chromium is not an additive but occurs naturally in some of the raw materials used in the manufacture of cement. Manufacturers are required to keep the chromium content of their cement products within prescribed limits. This is achieved by the addition of reducing agents, such as ferrous sulfate, which prevent the chromium dissolving in water.

In terms of health and safety, the Chromium (VI) Directive makes not a jot of difference to the normal site practice of using personal protective equipment, which prevents irritant dermatitis and cement burns, as well as chromium-induced allergic dermatitis. One impact that the Directive does have is for manufacturers and users, because of the use of reducing agents. These are only effective for a limited period and so manufacturers are required to declare the shelf-life of their cement products where reducing agents have been used. For further information on this and other cement matters, see the British Cement Association (BCA) website (www.cementindustry.co.uk).