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concrete briefing

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REFERENCES

High Strength Concrete, American Concrete Institute. aci Report 363. Tel 001 248 848 3700.

Design Guidance for high strength concrete, Concrete Society Technical Report No. 49. Concrete Society, 1998. Tel 01334 466007. High-strength concrete has a flexible definition and is interpreted differently depending upon experience and expectations. For structural design it is important to reflect the properties of the concrete and the interaction between concrete and reinforcement. Higher-strength concretes had early exposure in North American structures, and the guidance and design basis from the American Concrete Institute (aci) is useful coverage. Recent understanding developed from a European Union-funded collaborative research project and resulted in the more advanced design guidance published in Concrete Society Technical Report 49. This gives information and rules for design in high-strength concrete that is compatible with bs8110.

The Sherbrooke Reactive Powder Concrete Footbridge, P C Aitcin, M Lachemi , R Adeline and P Richard. Structural Engineering International, February 1998. Published by IABSE. Tel 00411 633 2647.

The properties and potential applications of macro-defect-free cement, N McN Alford and J D Birchall. Proceedings of a symposium on very high- strength cement-based materials, Boston, Massachusetts, November 1984. Ed. J Francis Young. Materials Research Society, Volume 42. Tel 001 724 779 3004 (ext. 531). Very high-strength concretes are beyond the realm of what we might see as conventional structural concrete. Their behaviour and potential uses require a broader vision of applications. It may take many years for suitable applications and markets to develop. The symposium organised by the Materials Research Society covered a wide range of high-strength concrete types. In particular, it gave a good presentation of some of the science and technology of potentially very high-strength materials, including macro-defect free cement. Since that seminar, other materials developments have continued. The reactive powder concrete (rpc) concept sits between conventional high-strength concrete and the advanced cement-based materials such as macro defect-free. The Sherbrooke footbridge paper describes the application of rpc to a full -scale concrete structure.

A Review of Service Life Design of Concrete Structures, Building Research Establishment Report br 316, B K Marsh. bre, 1996. Available from crc. Tel 0171 505 6622.

Service Life Design of Concrete Structures - Current and Emerging Approaches, Bob Cather and Dr Bryan Marsh, Ove Arup & Partners. Proceedings of an international seminar on management of concrete structures for long-term serviceability. University of Sheffield, November 1997. Ed. E Byars and T McNulty. Thomas Telford 1998.

Service Life Design for the Western Scheldt Tunnel, Breitenbucher, Gehlen, Schiessl, Van Den Hoonaard and Siemes. Durability of Building Materials and Components 8 (Volume One), 1999. Proceedings of 8th International Conference on the Durability of Building Materials and Components. There is much published information on the specific properties and deterioration of concrete structures. The specification for durability and for repair currently tends to be substantially prescriptive. More effective design and management of structures, throughout their life, would enhance the use of resources, reduce costs and perhaps give greater opportunity to introduce new technologies. The deterioration of structures is a complex interaction of materials chemistry, detail design and environment. Methodologies are developing for providing an assessment framework for the whole service- life design. These are reviewed in the bre report and the proceedings of the Sheffield conference. The service-life assessment methodologies can incorporate the output from the developing capability to model the deterioration process mathematically. The paper on the Western Scheldt Tunnel shows how such modeling can be used on real projects.

Guidance on the Use of Stainless Steel Reinforcement, Concrete Society Technical Report 51. Concrete Society, 1998.

Interim Guidance on the Design of Reinforced Concrete Structures using Fibre Composite Reinforcement, Institution of Structural Engineers, London, 1999.

Much premature deterioration of concrete occurs through corrosion of reinforcement, usually as a result of insufficient cover or concrete of poor quality. In good-quality concrete, austenitic stainless-steel reinforcement will remain free of corrosion for the life of a structure, even in severe exposure environments. Fibre-reinforced plastic reinforcement potentially offers the same protection against corrosion but has been used in relatively few structures other than on a trial basis. Design guidance is now available to cater for the significantly different properties of these materials compared to conventional steel reinforcement.

Recycled aggregates, bre Digest 433. BRE1998.

Sustainable Construction: Use of Recycled Aggregate Concrete, Ed. R K Dhir, N A Henderson and M C Limbachiya. T homas Telford, 1998.

The environmental impact of materials raises many concerns, but it can be difficult to change practice while retaining confidence in the performance of structures. Minimising the use of dredged or quarried aggregates is a desirable aim. BRE Digest 433 describes a basis for using recycled crushed concrete as an aggregate source for new concrete. It describes a classification system for different uses with suggested limits on quality and contaminants. The proceedings of a recent conference in London give the state of the art regarding the use of recycled concrete, with particular reference to the production of new concrete.

Testing of Concrete Structures, J H Bungey. Blackie Academic & Professional, 1995.

Fresh Concrete - Properties and Tests, P Bartos. Elsevier, 1992.

New tests to determine the properties of fresh concrete and concrete within a structure are continually emerging and adding to the large range already available. Knowledge of the principles involved, operating conditions and the test limitations is important for their successful use.

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