Opening Address

Professor L A Clark OBE, FREng

Professor of Structural Engineering, The University of Birmingham

Chairman of the Thaumasite Expert Group Report

Abstract Professor Clark will give an outline of the history of the field cases of thaumasite in the UK which led to the UK Government setting up the Thaumasite Expert Group which he chaired. The challenges which the Group faced will be described and the rationale for the membership of the Group explained. The scope and outcomes of the two subsequent reviews of the recommendations of the Group will be presented briefly. Finally, reference will be made to the link between the work of the Group and the recent research at the University of Sheffield.

Engineering at The University of Birmingham

Thaumasite Sulfate AttackThe UK Experience

Professor L A Clark OBE FREngProfessor of Structural Engineering

The University of Birmingham

Chairman Thaumasite Expert Group

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History

• 1990 Domestic properties• Feb 1998 M5 bridges

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Tredington Ashchurch Bridge

• TSA discovered during strengthening of piers for impact loading

• Bases and piers had been constructed in excavation backfilled with excavated clay

• Concrete in a “sump”

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TSA in M5 bridge foundation

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TSA in M5 bridge foundations

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History

• 1990 Domestic properties• Feb 1998 M5 bridges• March 1998 Question in House of Commons• 25/3/ 1998 Contacted by DETR to chair TEG• 1/4/1998 Appointed Chairman by Minister and

announced to House• 13/5/1998 TEG announced to House by Minister

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Thaumasite Expert Group Brief

• Prepare interim advice and guidance• Consult widely• Report to DETR within six months

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Scope of Brief

• Identification of structures at risk• Diagnosis• Appraisal• Structural assessment• Prognosis and remedial action• Specification• Further research

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Expert Group

Had to deal with a range of issues:• Scientific• Lack of data• Commercial interests• Public concerns over safety• Professional clients and owners (bridges)• House owners and mortgage lenders – highly emotive

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Expert Group Members

• Chairman: Chartered Structural and Civil Engineer• 12 Members representing organisations and institutions

from the scientific, design, specification, supply, contracting (civil and building), government, client, surveying, valuing and mortgage lending sectors

• Secretary from BRE• 2 Technical Experts from BRE• 32 Consultees from 15 organisations

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History

• 1990 Domestic properties• Feb 1998 M5 bridges• March 1998 Question in House of Commons• 25/3/ 1998 Contacted by DETR to chair TEG• 1/4/1998 Appointed Chairman by Minister• 13/5/1998 TEG announced to House by Minister• 15/5/1998 First meeting of Group• 7/12/1998 Report presented to Minister• 25/1 1999 Report published

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Report of Thaumasite

Expert Group

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Reaction to Report

• Well received• Balanced• Advice safe and robust• No significant adverse impact on industry sectors• Some problems of interpretation

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Reviews of Report

• March 2000 First Review - One-Year• March 2002 Second Review - Three-Years• Second Review not officially accepted by

Government until January 2003 as a result of change of responsibility from DETR to ODPM

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Scope of Reviews

• New Guidance• Dissemination• Current impact and awareness• Problems• New cases• New features• New research• Guidance in preparation

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Outcomes of Reviews

• Recommendations robust• Problems of interpretation• Data do not permit relaxations other than

those in BRE SD1• About 50 new cases• Concrete containing siliceous aggregates• Reinforcement bond

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BRE Special Digest SD1

• Provides guidance on concrete in aggressive ground• Replaces BRE Digest 363• Published in 2001 in 4 Parts• Includes guidance on special products such as precast

concrete pipes• Second Edition in 2003 - updates to BS EN 197-1:2000

and BS 8500:2002

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Part 1 of Special Digest

1(SD1)

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Research

• Report identified research areas• Sheffield University has been one of the

centres which has taken up the research challenge– Mixes– Reaction mechanism– Clay/concrete interface

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Seminar Purpose

• Disseminate the results of research at Sheffield• UK has significant experience of the management of TSA• Other countries have research expertise and cases of TSA

We need to share experience and best practice for the benefit of society