Concrete in Aggressive Ground:3rd edition

70 Pages·2005·1.79 MB·English

by  Building Research Establishment

Special Digest 1:2005
Third edition
Concrete in
aggressive ground
BRE Construction Division
BREis committed to providing
impartial and authoritative Acknowledgements
information on all aspects of the The principal funding for the preparation of this
built environment for clients, Special Digest was provided by The Concrete
designers, contractors, engineers, Centre. A list of sponsors and members of the
manufacturers and owners. We steering group who advised on its preparation is
make every effort to ensure the shown on page vi.
accuracy and quality of information
and guidance when it is published. BRE Contact details
However, we can take no For technical enquiries or comment on the use of
responsibility for the subsequent this Special Digest please email:
use of this information, nor for any [email protected]
errors or omissions it may contain.
BRE is the UK’s leading centre of
expertise on the built environment,
construction, sustainability, energy,
fire and many associated issues.
Contact BRE for information about
its services, or for technical advice:
BRE, Garston, Watford WD25 9XX
Tel:[phone]
[email protected]
www.bre.co.uk
BREpublications are available from
www.brebookshop.com
or
IHS Rapidoc (BREBookshop)
Willoughby Road
Bracknell RG12 8DW
Tel:[phone]
Fax: [phone]
[email protected]
Requests to copy any part of this
publication should be made to the
publisher:
BREBookshop
Garston, Watford WD25 9XX
Tel:[phone]
[email protected]
Cover photo by Graham Gaunt,
courtesy of Arup©
SD1
© BRE 2005
First published 2001
Second edition 2003
Third edition 2005
ISBN 1 86081 754 8
iii
Contents
Sponsors and members of steering group vi
Part A: Introduction
A1 Problem of chemical attack 1
A2 Scope and structure of the guidance 1
A2.1 Types of site and chemical agents covered 1
A2.2 Readership 2
A2.3 Structure of the guidance 2
A2.4 Diagrammatic overview of ground assessment and concrete specification 2
A3 Background to guidance on sulfate attack 4
A4 Key changes since SD1:2003 5
A5 Relationship between SD1:2005 and British and European
Standards for concrete 5
Appendix A1 Glossary of terms 6
References: Part A 8
Part B: Chemical attack on concrete
B1 General 9
B2 Principal types of chemical attack on concrete 9
B2.1 Sulfate attack 9
B2.2 Acid attack 11
B3 Other types of chemical attack on concrete 12
B3.1 Magnesium ions 12
B3.2 Ammonium ions 12
B3.3 Chloride ions 13
B3.4 Organic compounds 13
B4 Attack from aggressive carbon dioxide 14
B5 Attack from pure water 14
B6 Damage to concrete from crystallisation of salts 14
B7 Microbial contribution to chemical attack on concrete 15
References: Part B 15
iv Contents
Part C: Assessing the aggressive chemical
environment
C1 General 16
C2 Principal constituents of aggressive ground and groundwater 17
C2.1 Sulfates and sulfides 17
C2.2 Acids 20
C2.3 Magnesium, calcium, sodium and potassium ions 20
C2.4 Ammonium ions 20
C2.5 Chloride ions 20
C3 Presence and mobility of groundwater 21
C3.1 Static groundwater 21
C3.2 Mobile groundwater 22
C3.3 Flowing groundwater 22
C4 Site investigation for aggressive ground conditions 23
C4.1 Introduction 23
C4.2 Desk study 23
C4.3 Site inspection (walk-over survey) 24
C4.4 Visual description of the ground 24
C4.5 Sampling and testing soils 25
C4.6 Sampling and testing groundwater 25
C5 Classification of site locations for chemicals aggressive to concrete 29
C5.1 Groundwater and soil analyses 29
C5.2 Aggressive Chemical Environment for Concrete (ACEC) classification 34
Appendix C1 Recommended test procedures for ground aggressive to concrete 36
Appendix C2 Guidance on comprehensive site investigation of sulfate ground 36
References: Part C 37
Part D: Specifying concrete for general cast-in-situ
use
D1 Introduction 38
D2 Changes since SD1: 2003 38
D3 Design process 39
D4 Selection of the DC Class and APMs 40
D4.1 Background 40
D4.2 Key factors 40
D5 Composition of concrete to resist chemical attack 41
D5.1 Background 41
D5.2 Using Table D2 42
D5.3 Cement and combination types 42
D5.4 Aggregate type 44
D6 Additional protective measures (APMs) 44
D6.1 General 44
D6.2 Enhance concrete quality (APM1) 45
D6.3 Use controlled permeability formwork (APM2) 45
D6.4 Provide surface protection (APM 3) 45
D6.5 Provide a sacrificial layer (APM4) 46
D6.6 Address drainage of site (APM5) 46
D7 Intended working life 47
D8 Contract documentation 48
References: Part D 48
Contents v
Part E: Specifying surface-carbonated precast
concrete for general use in the ground
E1 Introduction 49
E2 Changes since SD1:2003 50
E3 Design process 50
E3.1 Selection of the DC Class and APMs 50
E3.2 Specifying composition of concrete 50
E3.3 Additional protective measures 50
References: Part E 51
Part F: Design guides for specific precast concrete
products
F1 Introduction 52
F2 Procedure for using design guides 53
F3 Design guides for precast concrete pipeline systems 55
F3.1 General considerations 55
F3.2 Using Design Guide F1a for specifying concrete for pipes and
associated units 56
F3.3 Using Design Guide F1b for specifying internal linings to pipes and
associated units 57
F4 Precast box culverts and precast segmental linings for tunnels and
shafts 58
F4.1 General considerations 58
F4.2 Using Design Guide F2a for specifying concrete for precast box culverts and
segmental linings 59
F4.3 Using Design Guide F2b for specifying internal linings to precast box
culverts and segmental linings 60
F5 Design guides for precast concrete masonry units 61
References: Part F 62
vi
Sponsors and members of
steering group
Sponsors
The Concrete Centre
Quarry Products Association (QPA)
Cementitious Slag Makers Association (CSMA)
UK Quality Ash Association (UKQAA)
Members of Steering Group
Professor L A Clark Chairman, Thaumasite Expert Group
Department of Civil Engineering, University of Birmingham
Dr C A Clear British Cement Association (BCA)
Dr N J Crammond Centre for Concrete Construction, BRE
Mr I Haining Costain
Professor T Harrison Quarry Products Association (QPA) and BSI Committee B/517/1
Mr J C Haynes National House-Building Council (NHBC)
Dr D D Higgins Cementitious Slag Makers Association (CSMA)
Mr I Holton British Precast Concrete Federation / Loughborough University
Mr P Livesey Castle Cement
Mr T I Longworth Associate, BRE
Mr N Loudon The Highways Agency
Dr B K Marsh Arup
Dr J D Matthews, Associate, BRE
Mr A Morton Hepworth Concrete / Concrete Pipeline Systems Association (CPSA)
Dr P J Nixon Associate, BRE
Ms L Parker Tarmac Ltd
Ms A Scothern The Concrete Centre
Dr L K A Sear UK Quality Ash Association (UKQAA)
Dr J F Troy Tarmac Ltd
Principal Consultees
Mr D Appleton Hanson Building Products
Dr J C Cripps Department of Civil and Structural Engineering, University of Sheffield
Mr A J Elliott Milton Precast / Box Culvert Association
Dr T Grounds Tarmac Topblock
Dr A Haimoni Keller Ltd / Federation of Piling Specialists (FPS)
Mr R M Raymond Hughes Concrete Ltd / Concrete Pipeline Systems Association (CPSA)
Mr P Rhodes RMC
Mr S Wade Stent / Federation of Piling Specialists (FPS)
1
Part A
Introduction
A1 Problem of chemical attack A2 Scope and structure of the guidance
Chemical agents that are destructive to concrete may be A2.1 Types of site and chemical agents covered
found in the ground. In the UK, sulfates and acids, naturally SD1 provides guidance on the specification of concrete for
occurring in soil and groundwater, are the agents most installation in natural ground and in brownfield locations.
likely to attack concrete. The effects can be serious (Figure The definition of a brownfield location adopted here is one
A1) resulting in expansion and softening of the concrete to a that has been subject to industrial development, storage of
mush. A substantial number of other substances are known chemicals, or deposition of waste, and which may contain
to be aggressive, most resulting from human activity, but aggressive chemicals in residual surface materials or in
collectively these are a lesser problem as they are ground penetrated by leachates. The procedures given for
encountered only rarely by concrete in the ground. ground assessment and concrete specification cover the
fairly common occurrence of sulfates, sulfides and acids.
It has been standard practice in the UK for at least six They also cover the more rarely occurring aggressive
decades to design concrete for installation in the ground to carbon dioxide found in some ground and surface waters.
be resistant to attack from commonly found chemicals,
including sulfates and acids. BRE has underpinned this
approach by issuing a series of guidance notes and Digests,
dating back to 1939, on the causes of chemical attack and
how to specify chemically resistant concrete.
Consequently, most concrete installed in the ground has
performed entirely satisfactorily and is expected to do so for
its required working life. Occasionally, however, cases of
chemical attack have come to light and have been subject to
research by BRE and others. Some of these cases have been
attributed to rarely occurring chemicals not specifically
covered by BRE Digests: some to natural ground conditions
for which there was insufficient guidance, such as
occurrence of pyrite; and some to the emergence of
previously unrecognised attack mechanisms, such as the
thaumasite form of sulfate attack (TSA) which has been
extensively reported in the last decade[1].
Guidance in BRE Digests has necessarily evolved to cater
for successive adverse field findings; to take advantage of
the emergence of new concrete constituents and
construction methods; and to maintain harmony with newly
published standards, latterly European ones. In order to be
both comprehensive and flexible, Digests have tended to
become longer and more complex. One objective of this
third edition of Special Digest 1 (SD1) is to simplify the
guidance. Other aims and changes are discussed later.
Figure A1 Extreme example of sulfate attack in a 30-year-old
highway bridge sub-structure exposed to wet, pyritic clay fill
2 Part A
While SD1 discusses several aggressive agents (eg Part E gives recommendations for specifying surface-
ammonium salts and phenols) occasionally found in heavily carbonated precast concrete for general use in the
contaminated ground, no specific procedures are included ground. An essential requirement for compliance with
for dealing with these. Specialist advice should be sought if this part is that surface carbonation is assured by
they are encountered. exposure of the precast concrete to air for a minimum of
10 days after curing. Since such carbonation provides a
A2.2 Readership degree of resistance to sulfate attack, the
SD1 provides practical guidance to ground specialists on recommendations for the derivation of DC Class in
the assessment of ground in respect of aggressiveness to respect of sulfates is relaxed by one level. Other than this,
concrete, and to concrete designers, contractors, specifiers the recommendations of Part D are followed for concrete
and producers on the specification of concrete to resist specification.
chemical attack.
Part F includes design guides for specification of specific
A2.3 Structure of the guidance precast concrete products, including pipeline systems,
Guidance is given in Parts B to F as follows. box culverts, and segmental linings for tunnels and
shafts. These products are manufactured under rigorous
Part B describes modes of chemical attack and discusses quality control to ensure appropriate mix composition
the mechanisms of the principal types, including sulfate and achieve relatively low concrete permeability.
and acid attack, and the action of aggressive carbon Together these provide an inherently high quality in
dioxide. respect of chemical resistance. Consequently, a further
relaxation (beyond that allowed for surface carbonation)
Part C deals with assessment of the chemical is permitted in respect of specification of DC Class for
aggressiveness of the ground. It gives procedures for the aggressive sulfate conditions. In practice this relaxation
determination of Design Sulfate Class (DS Class) from is used to offset the general-use recommendation that a
soluble sulfate and magnesium, and from the potential higher DC Class should be specified where concrete is of
sulfate (eg from oxidation of pyrite). It shows how the thin cross-section, or will encounter a relatively high
DS Class together with pH and mobility of groundwater hydraulic gradient.
may be collectively taken into account for natural ground
and brownfield sites to classify a location in terms of Part F also covers specification of precast concrete
Aggressive Chemical Environment for Concrete Class masonry units (concrete blocks) for aggressive ground
(ACEC Class). conditions. The guidance is based on Design Sulfate
Class rather than ACEC Class as there is currently no
Part D gives recommendations for the specification of correlation of block performance with the latter, though
concrete for general cast-in-situ use in the ground. It work on this is ongoing.
explains how to derive an appropriate quality of
concrete, termed the Design Chemical Class (DC Class), A glossary of terms is included as Appendix A1 on page 6.
from a consideration of the ACEC Class together with
the hydraulic gradient due to groundwater, the type and A2.4 Diagrammatic overview of ground assessment
thickness of the concrete element, and its intended and concrete specification
working life. In some cases, where conditions are highly An overview of the various procedures for ground
aggressive, additional protective measures (APMs) are assessment and specification of concrete is given in Figure
recommended. A2. This is arranged in four stages according to the
construction sector that has key responsibility. Within each
Part D follows this with guidance on the constituents of of these stages, the principal tasks are shown in boxes with
concrete required to achieve the identified DC Class. references to the relevant sections of SD1. While most steps
Specification is shown as maximum free-water/cement are equally applicable to all uses of concrete, there is a
ratio, minimum cement content and type of cement. differentiation in Stage 3 for the determination of DC Class
and APM between the three categories of concrete element
dealt with in Parts D, E and F.
Introduction 3
Stage 1 Consider design options for building or structure and Part C
Designer of building or prepare specification for site investigation.
structure Inform geotechnical specialist of design concept and
site investigation requirements
Stage 2 Carry out site investigation to determine chemical
Geotechnical specialist conditions for concrete, including water mobility.
See Part C
Determine DS Class and ACEC Class for site
locations using Tables C1 and C2.
See Section C5
Parts D, E
Stage 3 Determine the intended working life of proposed building or
and F
Designer of building or structure, and the form and use of specific concrete elements.
structure See Section D7
General use of cast-in-situ General use of surface- Specific precast concrete
concrete carbonated precast concrete products
Find specification of concrete and Find specification of concrete and ● Use Part F
APM using procedure in Part D: APM using procedure in Part E: ● Determine the DC Class and
● determine the DC Class and any ● determine the DC Class and any APM for the concrete using
APM from Table D1 APM from Table E1 Design Guides F1a, F1b, F2a,
● adjust DC Class / APM for section ● adjust DC Class / APM for section F2b, F3a, F3b
thickness and hydraulic gradient thickness and hydraulic gradient
● determine options for APM from ● determine options for APM from
Table D4 Table D4
State in contract documents the DS Class and ACEC Class of the ground and the method of deriving
the concrete specification (eg use of Tables C1, D1 and D2, or Table C2 and Design Guide F1a).
State requirements and options for concrete specification, including:
● specified DC Class of concrete after any enhancement
● specified number and type of APM and compressive strength class of concrete
● any other requirements
Stage 4 Obtain from contract documents the specified DC Class,
Contractor for building number and type of APM, and any other design
or structure in liaison requirements for each concrete element
with any third party
concrete producer
Formulate concrete mix design and consistence for structural
element taking into account specified DC Class, strength class,
availability, and cost of materials and contract requirements
Where concrete is being supplied ready-mixed, check the
proposed mix for conformity to the DC Class specification
Are all
requirements of
design guides and No
contract documents
met?
Yes
Accept concrete mix design for specific use.
Implement any APM specified for DC Class or
in contract documents
Figure A2 Procedure for design of buried concrete for use in an aggressive chemical environment