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1. How do I obtain recycled materials?

2. What are Type I and Type II additions?

3. What is the difference between fly ash and pulverised-fuel ash?

4. What does CEM II mean?

5. How do I use recycled aggregate?

6. Do you supply recycled materials?

7. How do I access the technical documents?

8. What is the k-value method?

9. Is there a glossary of terminology?

1. How do I obtain recycled materials?

Details on availability and supply of the recycled materials and industrial by-products detailed in these documents can be obtained from a number of sources. For recycled concrete aggregate and recycled glass information it is recommended that you visit the WRAP.

Information on availability of fly ash and conditioned fly ash can be obtained from the UKQAA .

Incinerator ashes and granulated rubber are made available by specialist producers, e.g. Ballast phoenix, or Charles Lawrence Recycling.

2. What are Type I and Type II additions?

Additions as defined in BS EN 206-1 are finely divided inorganic material used in concrete in order to improve certain properties or to achieve special properties. Additions are sub-divided into: Type I – nearly inert; and Type II – pozzolanic.

Examples of Type II additions listed in BS 8500 are fly ash, granulated blastfurnace slag, silica fume and metakaolin. Conditioned fly ash also has pozzolanic properties and may be used as a Type II addition; however, it is not referred to in BS 8500.

Examples of Type I additions are pigments conforming to BS EN 12878 and pulverised-fuel ash conforming to BS 3892-2. Used in small volume fractions, fine GR may be regarded as a Type I addition; however, it is not referred to in BS 8500.

3. What is the difference between fly ash and pulverised-fuel ash?

Fly ash is the European designation for pulverised-fuel ash; therefore, strictly speaking they are the same material. However, the British Standard series BS 3892 is still current, and refers to pulverised-fuel ash and not fly ash. Therefore, when referring to material conforming to BS 3892 the term pulverised-fuel ash should still be used.

4. What does CEM II mean?

BS EN 197-1 denotes 5 main types of cement. They are: CEM I (Portland cement), CEM II, CEM III (Blastfurnace cement), CEM IV (Pozzolanic cement) and CEM V (Composite cement).

CEM II cements contain Portland cement as the main constituent and between 6 and 35% of another main constituent (e.g. fly ash or limestone fines).

5. How do I use recycled aggregate?

Recycled aggregate is aggregate resulting from the processing of inorganic material previously used in construction, e.g. crushed concrete, masonry, brick. BS 8500-2 differentiates between RCA containing predominately concrete, and RA which contains much higher proportions of brick, masonry and asphalt.

RA is not covered in this series of digests because of concerns raised by concrete producers as its potential variability in composition. Research is currently in progress at the Concrete Technology Unit to address these concerns. It is expected that a seventh research information digest on RA will be available within 2 years.

RCA is a coarse aggregate and should be used in the same way as natural aggregate (NA). Whilst, BS 8500-2 gives limitations on the use of RCA in different exposure conditions, the conditions in which RCA is permissible may be extended provided that it is demonstrated that the resulting concrete is suitable for the intended purpose. However, in general RCA is particularly appropriate for use in:

• General applications (kerb bedding, drainage works and oversite under suspended slabs)
• Floors (house floors, garage floors and general industrial wearing surfaces)
• Internal reinforced concrete in exposure class XC1
• Buried plain and reinforced foundations in design chemical class DC-1

6. Do you supply recycled materials?

No. This website is maintained by the Concrete Technology Unit, a research and development unit of the University of Dundee, and is funded by the DTI, the RMC Environment Fund and industrial partners. Some of the industrial partners do supply recycled materials and industrial by-products and we suggest that you contact them via their websites.

7. How do I access the technical documents?

The technical documents are currently being published by The Concrete Society. The research information digests will be published one-a-month from May 2005 (starting with recycled aggregate concrete) and the Technology digests will be available from the Concrete Society shop.

8. What is the k-value method?

The k-value approach to using additions in concrete assumes that an addition is ‘k’ times as effective as an equal mass of cement in the development of strength, engineering properties and durability resistance. The “effective cement content” to be used in the calculation of minimum ‘cement’ content and maximum water/‘cement’ ratio is therefore calculated as c + ka, where c is the actual cement content and a is the addition content.

Any type of cement can be used, but the k-value concept is not applied when the addition is part of the cement. Typical k-values are 0.4 for fly ash and 1.0 for silica fume.

The k-value method is simple to use, but whether a single k-value of 0.4 is applicable to the full range of fly ashes permitted by BS EN 450 is questionable. The achievement of sufficient strength to give adequate performance is therefore uncertain. A further problem is that k-values based on strength are not necessarily appropriate to many aspects of durability performance, where the relative effectiveness of fly ash compared with cement may be considerably different.

A CEN committee is currently drawing up guidance for the k-value method and further information on its application can be found at the Committee’s website.

9. Is there a glossary of terminology?

For help on terms relating to cement and concrete, users are advised to refer to Guidance on the use of terms relating to cement and concrete prepared by Tom Harrison and Gillian Bond, published by The Concrete Society.