BS 1881 : Part 201 : 1986Uoc 666.972.017 : 691.32 : 620.1

British Standard

Testing concretePart 201. Guide tc the use of nondestructivemethods of test for hardened concrete

Essais du b&onPartie 201. Guide pour I’utilisation des mkthodes d’essai non destructifs sur le b&on durci

Prtifverfahren fi,ir BetonTeil 201. Leitfaden’fCr die Anwendung zerst&rungsfreier Prtifverfahren fiir Festbeton

British Standards institution

Foreword

This Part of BS 1881 has been prepared under the directionof the Cement, Gypsum, Aggregates and Quarry ProductsStandards Committee. All aspects of testing concrete arebeing included as Parts of BS 1881 and this Part forms ageneral introduction to those on nondestructive testing.

Nondestructive testing of a body of hardened concrete ascast, whether in a structure or as a component, offersadvantages of speed, cost and lack of damage in comparisonwith test methods which require the removal of a sample.The range of properties that can be measured in this way isconsiderable, and much valuable information may beobtained if the available methods are used with an under-standing of what they can, and cannot, achieve.

This guide presents information on test methods of thistype which will assist with the planning of investigationsand the selection of methods which are most appropriateto the circumstances. It summarizes the principal featuresof currently available techniques together with theiradvantages, limitations and most reliable applications.Many of the methods will be described in detail in otherParts of BS 1881, Parts 202 onwards*, while othertechniques which are not yet so well established are alsoincluded with appropriate references. Additional guidanceis given concerning the value of combinations of testmethods.

The use of tests to assess strength is covered in greater detailin BS 6089. Strain gauges suitable for monitoring thebehaviour of concrete structures in service, or under testload conditions, will be dealt with in Part 206’ of thisstandard. For details of methods which are not covered inthese British Standards, reference should be made tospecialist literature as indicated.

It is hoped that the guidance given in this Part willencourage the wider use of nondestructive testing in aworthwhile and economical manner; it is not intended tosupplant engineering judgement or to inhibit thedevelopment and use of other test methods.NOTE. The numbers in parentheses in the text of this Part refer to

the numbered bibliographic references given in appendix A.

Compliance with a British Standard does not of itselfconfer immunity from legal obligations.

* In preparation.

BS 1881 : Part 201 : 1986

Contents

Inside front coverBack cover

ForewordCommittees responsible

Guide

Saction one. General

1 . 1 Scope1.2 Definitions1.3 Principal considerations1.4 Planning an investigation

Section two. Test methods

2.0 Introduction2.1 Resonant frequency2.2 Electromagnetic cover measurement2 . 3 Resistivity measurements2.4 Half-cell potential measurements2.5 Radiography2.6 Radiometry2.7 Neutron moisture measurement2.6 Initial surface absorption2.9 Surface permeability2.10 Maturity measurements2.11 Thermography2.12 Radar2.13 Ultrasonic pulse velocity measurement2.14 Dynamic response techniques2.15 Surface hardness2.16 Scraad tast2.17 Internal fracture2.18 Pull-out test2.19 Pull-off test2.20 Break-off tast2.21 Penetration resistance2.22 Depth of carbonation2.23 Acoustic emission2.24 Strain measuramants

Saction thraa. Combinations of mathods

3.1 General3.2 Electromagnatic cover measurement or

radiography to locate reinforcement3.3 Nondestructive methods as praliminrry

to partially-destructive mathods3.4 Increasing tha confidanca level of u3st rasults3.5 Improvement of calibration accuracy3.6 Half-cell potential and resistivitv tests to

indicate likelihood of reinforcement corrosion

Appendix

A Bibliography

Tables

1 Suitability of nondestructive test methods2 Summary of principal test methods

9889

101011111212121313141415151616171716181819

20

20

202020

20

l

21

56

1

BS 1881 : Part 201 : 1986C;IJI(J~. !;oc:lion on0

Section one. General

1.1 scope

This Part of BS 1881 gives guidance on the tests that areavailable for nondestructive testing of hardened concretewhich forms a laboratory specimen or part of a structure,structural component or other type of engineeringconstruction. Some tests cause varying degrees of localizeddamage or defacement and may therefore be consideredpartially destructive; these methods are all defined asnondestructive. All the tests can be performed on theconcrete as cast and do not require the removal of samplesfor subsequent analysis or testing.

Methods of testing hardened concrete which require sampleextraction are either dealt with in other Parts of BS 1881or elsewhere (1, 2).NOTE 1. Damage caused by the extraction of small-diameter coresmay not be significantly greater than that due to some of the near-to-surface methods included here, provided that reinforcement isnot cut during extraction. In cases where strength determination isrequired they may offer similar or better accuracy with fewercalibration problems (3).

NOTE 2. The titles of the publications referred to in this standardare listed on the inside back cover.

1.2 Definitions

For the purposes of this Part of BS 1881, the definitionsgiven in BS 2787 and BS 6100 : Part 6 apply, togetherwith the following.

1.2.1 non-dertructivr test. A test that does not impair thaIntended performance of the element or member underinvestigation.

1.2.2 location. A region of concrete that is being assessedand that, for practical purposes, is assumed to be of unlformq u a l i t y .

1.2.3 near-to-surface test. A test that measures someproperty of the concrete near to, but below, the surface.

1.2.4 standard cube strength. The measured compressivestrength of a cube made, cured and tested in accordancewith BS 1881 : Parts 108,111 and 116 respectively.

1.2.5 estimated in situ cube strength. The strength ofconcrete at a location in a structural member estimated byindirect means and expressed as the compressive strengthof specimens of cubic shape.

1.3 Principal considerations

1.3.1 Advantages of nondestructive testing

Nondestructive testing offers significant advantages ofspeed, cost and lack of damage in comparison with testmethods which require the removal of a sample for

subsequent examination. These factors will permit moret-ktt’nsive testing and thus enable an investigation to be

wider ranging with respect to the concrete structure under~r~;lrnln;rtlon than would otherwise be possible. Theimmediate avarlabrltty ot results may also be an impOrtWIt

advantage of this type of testing.

1.3.2 Properties measured

The range of properties that can be assessed using non-destructive techniques is large and includes fundamentalparameters of the concrete such as density and elasticmodulus in addition to strength. Other properties whichcan be assessed include concrete surface hardness, surfaceabsorption and moisture condition as well as reinforcementlocation, cover and corrosion risk. The quality ofworkmanship and structural integrity may also be checkedby the ability to identify and locate voids, cracking anddelamination.

The required property is not measured directly by anumber of the available methods and precise correlationsare not always easy to achieve. In some instances estimatesof the required property can only be achieved bycomparative means.

1.3.3 I mportence of trained steff

Skill and care by the operator will generally be necessary,while the results obtained by some methods are particularlysensitive to variations in testing procedure. It is importantthat tests are performed by trained and reliable staff ifworthwhile results are to be achieved, end it is recommendedthat two persons should normally be involved during testingon site.

1.3.4 Situations in which non-destructive testing may bevaluable

Nondestructive testing may be applied to both new andexisting structures. For new structures, the principalapplications are likely to ba for quality control or resolutionof doubts about the quality of materials or construction.Testing of existing structures will usually be related to anassessment of structural lntegrlty or adaquacy. In eithercasa, a small number of tests on a large structure, forexample tests on a few cores, can be misleading, whilenondestructive testing is often a valuable indicator, eitheron its own or es a preliminary to some other form oftesting.

Nondestructive tests are useful for the following purposes:

(a) quality control of pretest units or constructionin situ;

(b) removing uncertainties about the acceptability of themateriel supplied owing to apparent non-compliancewith specifications;

(c) confirming or negating doubt concerning theworkmanship involved in batching, mixing, placing,compacting or curing of concrete;

(d) monitoring of strength development in relation toformwork removal, cessation of curing, pre-stressing,load application or similar purposes;

(e) location and determination of the extent of cracks,voids, honeycombing end similar defects within aconcrete structure;

(1) dstermlnlng the poaltlon, qurntltlaa or condltlon ofreinforcament;

(g) determlnlng the concrrte uniformlty, possibly es apreliminary to core cutting, load testing or other moreexpansive or disruptive tests;

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BS 1881 : Part 201 : 1986

Section one

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(h) increasing the confidence level of a smaller numberof destructive tests;

(i) determining the extent of concrete variability inorder to help in the selection of sample locationsrepresentative of the quality to ba assessed;

(j) confirming or locating suspected drtarlorrtlon ofconcrete resulting from such factors aa

(1) overloading,(2) fatigue,(3) external or internal chemical attack or change,(4) fire,(5) explosion,(6) environmental effects;

(k) assessing the potential durability of the concrete;

(I) monitoring long term changes in concrete properties;

(m) providing information for any proposed change ofuse of a structure, for insurance or for change ofownership.

1.4 Planning an investigation

1.4.1 Reasons for testing

The situations in which non-destructive testing may beuseful have been indicated in 1.3.4, and the reasons fortesting should be clearly established before the details ofa test programme are planned. These will establish theinformation that is required, e.g. strength, uniformity anddensity, and whether this should relate to the surface,near to the surface, or to the body of a member.

1.4.2 Acceptance of test data

Before any programme commences, it is essential that thereis agreement between the interested parties on the validityof the proposed testing procedures, the criteria foracceptance and the appointment of a person and/orlaboratory to take responsibility for the testing andinterpretation of the results.

It is essential, despite the apparent simplicity of some testmethods, that testing is performed only by skilledoperators who are familiar with the methods and that theinterpretation of results is entrusted to a suitablyexperienced engineer.

1.4.3 Selecting a test programme

1.4.3.1 Genera/. The test programme will be determinedby the objectives of the investigation coupled with thesuitability of the available methods in relation to the siteconditions and economic factors as outlined in 1.4.3.2to 1.4.3.5.

The objective may be to investigate the overall quality ofthe fabric, in which instance a random choice of testlocations will be appropriate. Where the objective is toinvestigate suspect material, the test locations will beselected for this purpose and the test results will only applyto this suspect material. In both cases, a sufficient numberof test locations should be chosen to establish a satisfactoryconfidence level for the results.

Visual inspection should also be regarded as an essentialpreliminary to the planning of a programme of testing sinceobservation of features such as deflection, cracking andcolour may yield valuable information affecting the choiceof methods and location of test points.

In rome lnrtanwr, calibration ir nrcoury to rrlatr thrmeawrrd valur8 or properth to thosa which are required,The availability and reliability of such calibrations are thusimportant.

1.4.3.2 Choice of t@t method& The methods recommendedin table 1 an llksly to be most suitable for the generalcircumstences lndlcated. Practical limitations may precludethe use of particular methods in some situations, while inother casas it may be appropriate or necessary to considerthe use of methods other than those recommended. Forexample, surface treatments, such as those to reducemoisture permeability, or drcorrtivr coatings may preventthe use of some methods. The principal features of themethods, including their most important limitations andmost reliable applications, are described in section twoand summarized in table 2.

The equipment required to perform the tests is easilyportable in most cases, and all tests can be rapidly carriedout, although extensive preparation may sometimes benecessary.

Important considerations affecting the choice of testmethod include the following.

(a) Test locations, Some factors to be considered are:

(1) the position within the member or structure;

(2) the variations of concrete properties throughdepth of lift;

(3) the position of reinforcement;

(4) the presenca of local defects or influences,e.g. surface carbonation;

(5) the depth below the surface of the zone to whichresults apply.

(b) Effect of damagn. The choice of method may beinfluenced bv:

(1) the effects of testing on the surface appearanceof the members;

(2) the possibility of structural damage resultingfrom the testing of small section members.

(c) Siz# of ma&or. The size of the member may restrictthe use of some test methods as a result of limitationson minimum edge distances, minimum or maximumthicknesses, or similar considerations.

(d) Testing accw8cy required The testing accuracyrequired will depend upon the purpose of theinvestigation. The level that can be achieved will dependon:

(1) the test method;

(2) the number and location of measurements;

(3) the accuracy and reliabilitv of availablecalibrations.

In determining the necessary number of maasurements.it should be remembered that an individual result

3

BS 1881 : Part 201 : 1986Section one

.Y -

relates only to the immediate test position and doas notnecessarily reflect the proparties of the concrete Ingeneral.

1.4.3.3 Combination of methods. In some circumstances,the accuracy achieved may be improved by the use of twoor more test methods. A combination of different testmethods may be used for the following reasons.

(a) The use of one method as a preliminary to another.The most common situations of this type are:

(1) the location of reinforcement prior to corecutting or use of other nondestructive testingmethods;

(2) the use of a nondestructive method to providecomparative data on concrete uniformity prior tocore cutting or use of other nondestructive methodsinvolving greater expense or damage.

(b) To obtain enhanced reliability of results on thebasis of:

(1) the confirmation of obsarved patterns of concretequality;

1.4.3.4 Site conditions. The principal sita conditions thatshould ba contldrrsd include:

(a) the geographic location and easa of transport oftest equipment;

(b) the accessibility of test locations;

(c) the environment;

(d) the safety of personnel and the general public duringtesting.

1.4.3.5 Economic end social fbctold The test programmewill be influenced by factors such as the value of the projectand costs arising from:

(a) delays in construction, or restriction on usage oroccupancy, while testing is conducted and decisions aremade;

(b) remedial works that may be necessary;

(c) the features of different test methods, includingtime, materials and equipment, temporafy works andmaking good;

(2) the correlation of combinations of measured valueswith a desired property.

Suitable combinations of methods are discussed in sectionthree.

(d) the need to select an adequate number of tests foran appropriate reliability of assessment;

(e) the need for a higher level of confidence in theassessment of structures where public safety is involved.

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d

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BS lBB1: Part201 : 1986

Section one

Table 1. Suitability of nondastructivr test methods

Pull-out test(cast-in insert) X X

Pull-out test(drilled hole) X x .x X

Internal fracture X X X X

Break-off test X X

Pull-off test X X X

Penetration resistance X X X

Surface hardness X X X X

Sewed test X X X

Dynamic response x x X

Ultrasonic pulsevelocity measurement X X X X X X

Acoustic emission X X

Electromagnetic covermeasurement X X X

Rdar X X

Radiography X XRadiometry X X X

Neutron moisturemeasurement X X

Depth of carbonation X X X

Initial surface absorption X X

Surface permeability X

Rosistivity mrasunmrnts X X

Half-call potentialmeasuraments X

Strain mrasurrmrnts X X X X X

Thermography X X

Maturity measurements X

Resonant f raquoncy X .

l Subject to the practical limitations outlined in section two.

6

Table 2. Summary of principal test methods

Method CfUW PrincipIl- PlkripJnumb m-

surt8cadmw

Principal

wfmim

Strength relatedQuality control(in SiN stnngth~

Moderato/minor

2.18

2.18

2.17

2.20

2.19

2.21

216

8s 1881 : Part 207’

8s 1881 : Part M7’

8s 1881 : Put 207’

8s 1881 : Part 107’

BS 1881 : Part 207’

Bs 1881 : Part 207.

6S1881: Port102

Bs4408 : Part 41

In SiN Stmtgthmaosuremmt

1 n SiN SWmgthmwsummont

In Situ strengthmeasurament

Indtustrangthnrruranent

2.8 8s 1881: Part 306’ Surface

hPe- PamrMliw851881 :Part6) - t

I I

Pull-out taat(cut-in inaart)

PUllM t a tfdrilled holo)

Strength related Moderate/minor

Mechanical

I

Drilling difficulties on vertical surfacesor roffits, surface zone tnt

I

Strength related Moderate/minor

Mechanical High test variability.surface zone test I

lnarul fracture

Flexural tensile Substantial/strength moderate

Mechanical

I

High test variability,substantial damage I

Brwkaff lost

Direct tensile Moderate/strength minor

Mechanical

I

Care needed with adhasfva,surface zone tast I

Pull-offtaNl

Strength related Machanical

I

8pacific dibmtiom ractuirad, limits onminimum roambar slse, swfacr ZorW test I

hntmticnlwktulm

Surface ha&tess Vwy minor Machanical

I

Greatly &acted W surf- &&a endmoisture, autfaca mat unnpraaentathnon concrate more than 3 months dd,strmgthdibmtlonoffwtalbymlxprooerdar

Surface&sorption

Minor

Electrod 2,potontlJ o f “,rdnforament f

8urficr .7mparaturadiffwancas .

:.

NOM i

Maturity - Minor ”

Intro-rod ._ Extrarow -raturn effects hnw to be Iradiation , rxoh&d, tamperaturo dlffarentials em&I,datection shorta6a of &ta l d davdopment

. .

fhermo- ’ i, Proplannad uwgr, spulfk calibrationsensitive ~r0qUir.d . .chamkal ordactronicI monit&lnff

I l In praparatlon. -

I /r I

(I-

r I r r r r-. rc

I I

Table 2 (continued)

-

Method Cl8Uea Principal rafemnce Principrl Principal surface TYP. of Remarksnumbor applications properties damage equipment

-d

6cmed test 2.18 (21) Quality control Surface Minor Mechanical Sand/cement screeds only. cannot be usedof screeds soundness if screed over soft material

Ultrasunic pub 2.13 BS 1881 : Part 203. Comparative Elastic modulus None Electronic Two opposite smooth faces preferably needed,velocity mouuromont (supersedes surveys strength calibration affected by moisture and

8s 4408 : Part 5) mix properties, some surface staining possible

Acoustic rmiesion 2.23 (34) Monitoring Internal orack None Electronic Increasing load required, not fully deveiopedduring load development for site usetesting

Dynamic maprmmtachniquaa

Elactrom~netkccnr mmaurommt

2.14

2.2

UO) Pile integrity Dynamic response None Mechanical/ Cannot yield bearing capacityelectronic

8s 1881 : Part 204. Location of Presence of None Electro- Affected by magnetic aggregates and(supersedes reinforcement embedded steel magnetic unreliable for congested steel6S4408: Part 1)

Rular 2.12 (19) Location ofvoids orreinforcement

Internalinterfaces

None Electronic Experience limited, procedures underdevelopment

~~MFew

Adiomotry

Nwtron moktunmnsurommt

l In preparation.

2.6

2.8

2.7

0.S 1881 : Part 205’ Location of Relative None Radioactive Extensive safety precautions,(rUWSd8S voids or density source or limit on member thicknessBS4498:Part3) reinforcement generator

13) Quality control Density None Radioactive Safety precautions and limit on membersource or thickness for ‘direct’ method, ‘backscatter’generator method is surface zone test

(3) Comparative Moisture None Nuclear Surface zone test, calibration difficultmoisture content content

r Table 2 (concluded}_ ..- -..---. ~__ -_._

Method ClNlSS Principal reformco Principal Principalnumber 8pplicrtions properties

amssed

------------I---Surf8ca

dun-TYW of8quipm8nt

Remarks

Depth of carbonation

Resonant frequency

2.22

2.1

(33) Ourabil ity Concretesurvey alkalinity

8S 1881 : Part 209’ Quality control Dynamic elastic(supersedes modulusES 1881 : Part 5)

Strain measurements

’ In preparation.

2.24 8s 1881 : Part 206. Monitoring Changes in(supersedes movements strain8s 4408 : Part 2) in structures

Moderate/minor

-

None

M&nor

Chemical

Electronic

Optical/mechanical/electronic

-

Approximate indication of extent ofcarbonation

Specially cast specimen required

Attachment and reading requires skill,can only indicate changes in strain

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LSection two. Test methods

BS1881:Part201:1996Section two

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20 Introduction 2.22 Advantages

The test methods described here are in varying stages ofdevelopment. Those which are well established are detailedin other Parts of BS 1881, as indicated. Methods which arenot fully developed are described in technical literaturereferred to in the bibliography in appendix A, as indicatedby the numbers in parentheses.

This method for locating reinforcing steel within aconcrete member is truly nondestructive.

Under reasonable conditions, a site accuracy of estimatedcover of f 6 mm within the working ranga of the instrumentmay be expected.

Techniques are available to permit estimatas of both barsize and depth of cover when neither is known.

21 Resonant frequency2.2.3 Limitations

NOTE. This method is currently described in BS 1681 : Part 5,but will eventually be revised as ES 1881 : Part 209.

The effect of bar site is important if this is lass than 10 mmor greater than 32 mm.

2.1.1 General

Measurement of the resonant frequency of a prismaticspecimen and the determination of its density may be usedto yield a value for the dynamic elastic modulus of theconcrete of which the specimen is formed.

2.1.2 Advantages

This procedure is quick, does not damage the specimen inany way and is reliable. The influence of operatortechnique is small and other testing errors are low.

Calibrations are sansitive to steel type, bar diameter anddeformity, and aggregate and cement type, and have totake these factors into account. Most commerciallyavailable equipment is calibrated for medium-sized mildsteel round bars in ordinary Portland cement concrete.

The range of the equipment is limited according to type,but care and experience in interpretation of data arerequired in the following casas:

(a) multiple bars, e.g. laps, transverse steel or doeelyspaced parallel bars;

2.1.3 Limitations

(b) light wire mesh, buried nails or othar metals batweentha reinforcing bars and the surf-;

(12) metal tie wiras;

This test has to be performed on a standard specimen ofhardened concrete and is usually associated with laboratorv-cast samples. The method as described is not applicable toin situ usage.

(d) aggregates with magnetic properties;

(e) stability of calibration, which may ba particularlyimportant in relation to tamparaturr changes within themagnetic field;

ff) strav magnetic fields.2.1.4 Principal application

The principal epplication Is to provide a valua of dynamic 2.2.4 Prlnalpd applkrtknaUidStlc rnodulur ot concrete. i he test may also be valuable The principal application8 are the location of reinforcementas a technique for monitoring changes of concrete and estimation of cover, orientation and, in some cases,properties as a result of various influences during laboratory diameter of reinforcing bars. The technique is most reliableinvestigations. A modified form of this test may be adapted for lightly rainforced mambars, and may be used for thefor site use. following:

22 Electromagnetic cover measurement

NOTE. This method is currently describad in BS 4406 : Part 1,but will avrntuallv be rwisad as 68 1681 : Part 204.

(a) quality control checking, to ensure correct locationand cover of reinforcing bars;

(b) investigation of concrate rnambers for which recordsare not available;

2.2.1 General

Portable devices are available which are operated byrechargeable or dry batteries and are based uponmeasurement of the change of an electromagnetic fieldcaused by steel embedded in the concrete. Such equipmentis calibrated to indicate the distance of the steel below thesurface, and in some cases may also indicate the diametersof reinforcing bars. When reinforcement is parallel to thesurface, rotation of the search head will enable thealignment of the bar to be identified. Non-calibrated metaldetectors are available which may detect metals (ferrous ornon-ferrous) at depths outside the range of the aboveequipment.

(c) location of ninforcernant as a preliminary to someother form of tostlng in which ninfotwmmt should bravoided, e.g. taking cores, ultrasonic pulse velocitymeasurement or near to surface mathods.

2 3 Resistivitymeasurements ,

NOTE. This method Is discussad In rafarancas 4. 6 and 6 ofeoprndix A.

2.3.1 Generd

The electrolytic rasistivity of concrete is known to beinfluenced by many factors induding moisture, salt contentand temperature, as well as mix propwtions and the

9

water/cement ratio. The presence of reinforcement may alsoinfluence measurements. In situ measurements may bemade using a Wenner four-probe technique in which fourdldt Ilthkh dlCr ~~1dl’Utl Ill d blldlU~ll IlllU 1)ll OI (II&t IlUlflw th,

1.t111t ll!lV 4111 Itit tJ 111 r~t~lltll qMt.llt~‘, !\I1 Vltwll kdl I.111 IFjIll 1s

passed through the outer electrodes while the voltage dropbetween the inner electrodes is measured. The apparentresistivity of the concrete may be calculated from aknowledge of the current, voltage drop and electrodespacing. For practical purposes, the depth of the zone ofconcrete affecting the measurement may be taken as equalto the electrode spacing.

2.3.2 Advantages

This technique can provide a simple nondestructiveindication of the electrical resistivity of the concrete at thetest location. This can be related, principally by experience,to the corrosion hazard of embedded reinforcement orother features of the concrete.

2.3.3 Limitations

Correlation of resistivity measurements to properties suchas mix proportions are at present only possible underlaboratory conditions. The use of in situ measurements forthis purpose is hindered by the sensitivity of readings tothe factors outlined above. Practical application is thusgenerally restricted at present to comparative measurements.Limited damage to the concrete surface may sometimes benecessary.

2.3.4 Principal applications

Experienced investigators have used the method to assessor monitor the durability of concrete exposed to severeenvironments. In some circumstances, the likelihood ofcorrosion of embedded reinforcement may be predictedby this method where half-cell potential measurementsshow that corrosion is possible (5,6). Other possibleapplications of the method include comparative assessmentof moisture conditions and estimation of the thickness of aconcrete pavement slab by varying the electrode spacings(7;. Resistivity measurements may also be used to assist theintegrity testing of reinforced concrete piles (8).

24 Half-cell potential measurements

NOTE. This method is discussed in references 6, 6 and 9 ofappendix A.

2.4.1 General

The method of half-cell potential measurements normallyinvolves measuring the potential of an embedded reinforcingtjar relative to a reference half-cell placed on the concretesurface. This is usually a copper/copper sulphate or silver/

silver chloride cell but other combinations are used. TheL-~WI t?ttt functions as an electrolyte and the risk ofcot ~osion of the teinfot cement in the immediate region ofthe test location may be related empirically to the measured

potential difference (5). In some circumstances, useful

measurements can be obtained batwoan two half-calls onthe concrete surface (6).

2.4.2 Adurntrgr8I he rrqul(lltislll I, rllrl&l a,td allabIal a11 alrtlclsl flUll

destructive survey to produce isopotential contour maps ofthe surface of a concrete member. Zones of varying degreesof corrosion risk may ba identified from thesa maps.

2.4.3 Limitations

This method cannot indicate the actual corrosion rate.It may require a small hole to be drilled to enable electricalcontact to be made with the reinforcement in the memberunder examination, and surface preparation may also berequired. It is important to recognize that the use andinterpretation of the results obtained from the test requirean experienced operator who will be aware of otherlimitations such as the effect of protective or decorativecoatings applied to the concrete.

2.4.4 Principal applications

This technique is most likely to be used for assessment ormonitoring of the durability of reinforced concretemembers where reinforcement corrosion is suspected.Reported uses include the location of areas of highreinforcement corrosion risk in marine structures, bridgedecks and abutments. Used in conjunction with other tests,it has been found helpful when investigating concretecontaminated by salts.

25 Radiography

NOTE. This method is currently described in BS 4408 : Part 3,but will eventually be revised as BS 1881 : Part 205.

2.5.1 General

Radiography provides a method of obtaining a photographof the interior of a concrete member from which variationsof density may be identified. This is produced on a suitablefilm held against the rear faca of the concrete, while a beamof gamma rays or high-energy X-rays is directed at the frontface. The presence of high density materials, such asreinforcement, or low density areas caused by voids willproduce light and dark areas on the film.

2.5.2 Advantages

This non-destructive method is the most direct means ofproviding pictorial evidence of the interior of a body ofconcrete.

2.6.3 LimitationsThis technique raquires extensive safety precautions andutilizes highly specialized equipment. It is thereforeessential that this type of work is only performed bvradiographers with rxperirnoa of working with concrete.Gamma ray sources may ba used for member thicknessasof up to 500 mm; high-energy X-rays are more suitable forgreater thicknesses up to 1.6 m.

10

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-

-

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L-

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2.5.4 Principal applications

The principal applications are as follows.

(a) The method is particularly valuable for locating areasof variable compaction or of voids in the concrete, or inthe grouting of post-tensioned constructions.

(b) The general location of reinforcing bars can bedetermined. In favourable conditions, the location andsizing of reinforcing bars may be determined fairlyprecisely by photogrammetric analysis of the radiograph.The accuracy of measurements dedines in adverseradiographic conditions.

26 Radiometry

NOTE. This method is discussed in references 3 and 10 ofappendix A.

2.6.1 General

A narrow beam of gamma rays is directed into the concreteand the intensity of radiation emerging Is measured bymeans of either a Geiger counter or a scintillation detector.Measurements may be made either of radiation passingthrough a body of concrete (direct method) or of radiationreflected back to the same surface by collision withelectrons within the concrete (backscatter method).In either case, the mass per unit area of the concrete is theproperty which has the greatest influence on theattenuation of the beam of rays and hence the measuredvalue of radiation. Steel reinforcement has about threetimes the effect of normal concrete and its presence willthus influence measured values.

2.6.2 Advantages

This method provides a truly non-destructive method ofassessing in situ density. The direct method permitsexamination of the interior of a concrete member. Portableequipment, which can provide either backscatter or directreadings and incorporates a microprocessor to computeresults, is commercially available.

2.6.3 Limitations

Direct methods across the full thickness of a concreteelement require extensive precautions, skilled personneland highly specialized equipment. Calibration may beobtained by cutting cores in the path of radiation after testand using these as samples for physical density measure-ment. Otherwise, results are restricted to comparative use.Concrete up to at least 1.2 m thick can be tested.For larger bodies of concrete or ground supported slabs,it may be necessary to lower the source and/or detectorinto predrilled or formed holes.

Direct readings may only be made at depths of up to300 mm below the surface using the commercially availableportable equipment, while backscatter results relate to asurface zone approximately 100 mm thick. Althoughequipment of this type is calibrated, difficulties may becaused by the lack of uniformity of the radiation absorption

D8 1881:Pwtaol: 1esd8aotlon two

characteristics of concrete or density gradients near thesurface. Backscatter results will mnerally be more variablethan direct measurements (10).

2.6.4 Principal rpplications

The principal applications are as follows.

(al Measurements of density where large numbers ofrepetitive measurements are required, e.g. for specialisedin situ locations such as cement bound road bases or forquality control of precast units.

(b) The direct method may be used to detect memberthickness or reinforcement in addition to densitymeasurements.

(cl The backscatter method may be used to measurethe density of the surfaca zone.

27 Neutron moisturemeaswemerit

NOTE. lhir method ir diauwod in rofmncr 3 of lpprndir A,

2.7.1 General

The energy of fast or high-energy neutrons is rapidlyreduced by the presence of elements of low atomic weight.The resulting slow or lcrw-energy neutrons may be countedby a detector designed for this purpose. Few elements oflow atomic mass are found in concrete other thanhydrogen contained in water, and the counts may be usedto provide an indication of moisture content

Measurements may either be made of the scattered neutronsreflected back to the same surface as the sourca (thebackscatter technique) or a direct transmission value maybe obtained by lowering the source into a predrilled hole.Best results are obtained using the direct technique whenthe moisture content is high.

2.7.2 Advantrgrs

Portable equipment, which can provide either backscatteror direct readings end incorporates a microprocessor tocompute results, is commercially available. This provides atruly nondestructive assessment of in situ moisture contentwhen using the backscatter method.

2.7.3 Limitations

The results will only relate to a surface zone of the concretea few millimetres deep when using the backscatter method.Direct measurements may be made at depths of UP to300 mm using the equipment currently available.Calibration of the instrument may not be straightfowardend in situ measurements may be influenced by moisturegradients near to the surface and the presence of other ’neutron absorbers. The accuracy of the method is poorfor concrete of low moisture content.

27.4 Principal application

The principal application is the estimation of the moisturecontent of the surface zone.

11

0SV331 :Part20\ : 1986Section two

2.8 Initial surface absorption

NOTE. This method is currently described in 8s 1881 : Pert 5,but wtll eventually be revised as 6s 1881 : Pert 208.

2.8.1 General

Initial surface absorption involves measurement of the rateof flow of water per unit area into a concrete surfacesubjected to a constant applied head.

The equipment consists of a cap which is clamped andsealed to the concrete surface, with an inlet connectedto a reservoir and an outlet connected to a horizontalcalibrated capillary tube and scale. Measurements aremade of the movement of the water in the capillary tubeover a fixed period of time following closure of a tapbetween the cap and the reservoir.

The absorption of water by a dry surface is initially highbut decreases as the water-filled length of capillariesincreases, thus measurements have to be taken at specifiedtime intervals from the start of the test.

2.8.2 Advantages

This method provides a practical non-destructive methodof in situ measurement of the rate of water penetration ofa concrete surface. It may be used on exposed aggregate orprofiled surfaces provided a water-tight seal is obtained.

2.8.3 Limitations

It is essential to provide a water-tight seal between the capand the concrete surface and difficulties are likely to beencountered. Sometimes it will be necessary to drill thesurface for fixings.

Results are affected by variations in moisture content ofthe concrete, and samples for laboratory testing shouldpreferably be oven dry or at least have been in a dryatmosphere for 48 h. It is virtually impossible to achievecomparable conditions with in situ concrete and this willreduce the reliability of quantitative results in thisapplication. In these circumstances, use will be restricted tocomparative measurements. The standardited pressure usedin the test, created by the 200 mm head of water, is lowand although results may be related to surface weatherexposure they are of little relevance to behaviour underhigher water pressures.

The internal permeability characteristics of a body Of

concrete cannot be assessed by this method.

2.8.4 Principal application

The most reliable application is as a quality control test forprecast units which can be tested when dry. The test hasbeen shown to he sensitive to changes in quality andweathering performance, and thus may also ha usedcomparatively on in situ concrete for the purposes ofquality contra! and assessment of potential durability.

29 Surface permeability

NOTE. There methods are dircursed in references 11, 12 end 13 brappendix A.

2.9.1 General

Several methods are available, or under development,which permit an assessment of the permeability of concretein the SUrfarX zone to water, air, carbon dioxide or othergases under pressure. These techniques, which vary indetail, all require a hole to be drilled into the surface ofthe concrete.

2.9.2 Advantages

These methods provide practical ways of assessing thepermeability of surface zone concrete under in situconditions. Information of this type may be particularlyvaluable as an indicator of potential durability.

2.9.3 Limitations

Some surface damage will be caused by these methods.The results will relate only to the particular test pointsand it will generally be necessary to perform tests at anumbar of points to obtain a representative value for eachlocation. Although use of tests of this type is increasing,experience in the interpretation of site results is still limited.

The internal permeability characteristics of a body ofconcrete cannot be assessed by these methods.

2.9.4 Principal application

The main application is the assessment of the permeabilityof surface zone concrete in relation to durability surveys.

210 Maturity measurements

NOTE. This method is discusSed in references 14 and 15 Of aFWndix A

2.10.1 General

Maturity is an arbitrary parameter based on measurementsof the internal temperature of a body of concretethroughout the setting, hardening and subsequent strengthdevelopment stages.

Equipment for these measurements may be constructed inmany forms. Two commercially available types are:

(a) disposable maturity meters, which are based on a

temperature-dependent chemical reaction and areembedded in the concrete surfaca at the time of casting;

(b) electrically-operated integrating maturity meters,consisting of a microprocessor coupled to a reusabletemperature sensor inserted into a metal tube which iscast into the concrete.

Maturity measurements may be related to strengthdevelopment for a particular concrete mix and areespecially valuable when combined with other non-destructive methods for monitoring strength development.

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8s 1881 : Part 201 : 1986Section two

2.10.2 Advantages

The measurement of maturity is a simple nondestructivetechnique which takes account of the temperature histowwithin the concrete during hydration. This is particularlyvaluable for construction during adverse weather conditionswhen a knowledge of strength development is important.

2.10.3 Limitations

Measurements relate only to the individual test points,and for a major pour it will thus be necessary to takemeasurements at several points simultaneously to accountfor variations within the concrete. This can involveconsiderable expense if used on a regular basis.

Correlations between maturity and strength will only applyto the particular mix and circumstances for which they havebeen developed.

2.10.4 Principal application

The principal application is the monitoring of in situstrength development in relation to stripping of formwork,removol’of props or the application of load.

211 Thermography

NOTE. This method is discussed in references 16 and 17 ofappendix A

2.11.1 General

Thermography involves the recording of surface temperaturedifferentials on a concrete member undergoing heating orcooling. Hidden features, including voids or cracks, willinfluence the local rate of heating or cooling and may bedetected by examination of temperature contour plots.Infrared measurement techniques are necessary to detectand record the temperature differentials involved, whichare very small. The following alternative types of equipmentare available:

(a) a quanrirarive remperatun, meawringgun, whichwill yield a digital reading of the surface tamperatureat the point at which it is aimed;

(b) a qualitatiwe thermal imager, which will indicaterelative temperature differentials within the field ofview; the image may be recorded photographically;

(c) a scanner and cathode-fey monitor, which willproduce a colour display of calibrated isotherms whichmay be video-recorded or photographed.

Experience suggests that observations are best made duringcooling, for example in the afternoon when the surface hasbeen exposed to sunlight.

2.11.2 Advantages

This method is non-destructive, non-contacting, requiresonly one exposed surface and does not require the safetyprecautions necessary for radiography. Thermography may

13

be carried out with the apparatus near to, or at aconsiderable distance from, the concrete surface.

2.11.3 Limitations

For large-scale structural surveys, it may be necessary to usethe relatively expansive scanner in conjunction with acathode ray tube. Precautions have to be taken to avoidintarferenca from extranaous heat sources. Experienca ofthe use of these tachniquas for inspection of concrete isl i m i t e d .

2.11.4 Principd applications

The principal reported applications are from NorthAmerica, where the technique has been used for thedetection of delamination within reinforced concretebridge decks. The method has also been used successfullyfor the location of Ingress of moistum and of minforcement(181, ducts, voids or similar features within concrete wallsor slabs, although pubiishad information is limited.

212 RadarNOTE. This method is discussed in refmm 19 of mndix A

2.12.1 Ganard

A surface-penetrating radar system may be used to examinethe reflections of short duration pulses from interfacesbetween materials with different dielectric constants lyingbelow the surface. Reinforcing bars, voids, ducts and similarfeatures may be identified and the thickness of slabs mayalso be determined. The equipment, which consists oftransmitting and receiving antennae together with a controlunit and recorder, is available commercially.

2.12.2 Advantagas

This method, which is nondestructive and may be non-contacting, provides a rapid method of locating andrecording features lying below the surface of a concreteelement.

2.12.3 Limitations

Many factors contribute to the characteristics of the msults,which require skilled specialist interpretation. Theresolution that can be obtained will depend upon thefrequency used, which will in turn influence the depth ofpenetration possible. When high speed testing of large areasis involved, as in highway surveys, data handling andpresentation may present particular problems. Applicationsof this technique to concmte are at an early stage, andavailable data and rxparienca am limited. .

2.12.4 Principal applications

The principal areas of application are likely to be theidentification and location of voids, cracks, delamination,and reinforcing bars. The thickness of slabs and location ofvoids beneath ground slabs can also be determined (17).

BS 1881 : Part 201 : 1986Section two

213 Ultrasonic pulse velocitymeasurement

NOTE. This method is currently described rn ES 4408 : Part 6,but wtll eventually be revised as ES 1881 : Part 203.

2.13.1 General

Ultrasonic pulse velocity equipment measures the transittime of a pulse between transducers placed on the surfaceof a body of concrete. The pulse velocity can then bacalculated using the measured path length through theconcrete.

The pulse velocity depends upon the dynamic Young’smodulus, dynamic Poisson’s ratio and density of themedium.

2.13.2 Advantaw

The principal advantages of ultrasonic pulse velocitymeasurement are that it is totally nondestructive, quick touse and reflects the properties of the interior of a body ofconcrete. It is particularly valuable in circumstances wherea considerable number of readings is required for theassessment of uniformity of hardened concrete.

2.13.3 Limitations

Although non-destructive, it is essential not to overlooksurface staining from the use of some couplants. The pulsevelocities for most practical concrete mixes lie within anarrow range and it is therefore necessary to measure boththe transit time and path length to an accuracy of the orderof + 1 % if the results are to be of greatest value.

Measured values may be affected by surface texture,moisture content, temperature, specimen size, reinforce-ment and stress. Correlations with strength are difficultto make and will be influenced considerably by the typesand proportions of mix constituents and maturity. Forcomparative surveys, readings may be made with bothtransducers placed on the same surface but when it isnecessary to measure pulse velocity accurately, e.g. forstrength estimation, it will be necessary to place thetransducers on opposite faces of the concrete element.

2.13.4 Principal applications

The principal applications are as follows.

(a) Determination of concrete uniformity, which is mostreliably achieved by taking measurements on a regulargrid on a member, or at comparable locations on similarmembers.

(b) Detection of cracking and honeycombing, which willincrease the effective path length resulting in a highermeasured transit time. If such defects lie between thetransducers, a higher measured transit time will notnecessarily occur if the crack or voids are water filled orbridged by reinforcement. The depth of surface cracksmay be estimated by placing transducers on either side.

l 1 MPa 1 0 ‘ N/m’ 10 bar.

Honeycombing or voids may be identified by taking aseries of measurements through a member on a regulargrid. The minimum size of detectable defect dependsupon the transducer size and the distance between them.

(c) In situ strength estimations, which are unlikely tohave 95 % confidence limits of better than f 7 MPa’given ideal testing conditions and a specifically preparedcalibration chart for the concrete mix in use. It may bepossible to improve this value if the density is known,or by combination with measured rebound numbers.

(d) Strength development monitoring, which is possibleif appropriate calibration charts can be obtained. Whereresults can be compared with predetermined limits foracceptance, the method may be used for quality control,formwork removal, stressing operations, etc.

(e) Assessment of concrete deterioration, using a generalcomparative survey to locate suspect areas. Techniquesare also available to estimate the depth of surface firedamage or chemical attack. Long term performance ofconcrete may also ba monitored by conducting repetitivetests at a location.NOTE. Although this method of test may be used on both in situconcrete and laboratory specimens, for purely laboratoryinvestigations resonance tests may be more suitable owing totheir greater sensitivity. One test of this tvpe is outlined in 2.1.

(f) Estimation of layer thickness, which may be possiblewhere there is a surface layer of inferior quality to thebody of the concrete due to construction, weathering orother damage such as fire.

214 Dynamic response techniques

NOTE. Some of these methods are discussed in reference 20 ofappendix A

2.14.1 Genaral

Several techniques are available that measure the responseof a structural member to an imposed dynamicload. They may be used to deduce stiffness and otherstructural properties. A wide range of methods may beapplied to l ntlra structures or lndlvldual memkrs of astructure, but the approach 1s most fully developed forintegrity testing of piles. Applications to other types ofstructural member are under development.

Techniques for pile testing indude single blow andcontinuous vibration methods (20). The simplest and mostwidely used of these is the pulse echo method in which thereflected shock waves, resulting from a single hammer blow,are monitored by a hand-held accelerometer coupled to asignal processor. The wave form is then generally displayedvisually.

2.14.2 Advantagas

These methods are fast to use and nondestructive. A widerange of specialist equipment is commercially available,which is especially suitable for testing of piles.

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2.14.3 Limitations

The equipment is often very specialized in nature andexpensive, and considerable skill and experience arenecessary for the interpretation of results. Tests on pilescannot directly assess the cross-sectional area or bearingcapacity, and limited preparation of the pile head maysometimes be necessary.

2.14.4 Principal applications

The principal applications are as follows:

(a) assessment of structural integrity and remainingservice life;

(b) fault finding;

(cl assessment of the need for and effectiveness ofrepairs;

(d) identification of defects, varying support conditionsand lengths of piles.

2.15 Surface hardness

NOTE. This method is published as BS 1881 : Part 202 (previouslydescribed in ES 4408 : Part 4).

2.15.1 General

The surface hardness test is based on the principle that therebound of an elastic mass depends upon the hardness ofthe surface which it strikes. A number of different hand-held spring-loaded steel rebound hammers are available tosuit a variety of concrete types. The results are expressedin terms of the rebound number which is affectad byconditions near to the surface. The test is particularlysuited to comparative surveys but the results may also becorrelated with other properties of the concrete. In thiscase a specific calibration for the type of concrete underinvestigation should be established as the usa of universalcalibrations can give seriously erroneous results.

2.15.2 Advantages

The principal advantages of surface hardnaas tests are thespeed and low cost of testing.

2.15.3 Limitations

Results relate only to a surface zone of up to 30 mm depthand may be greatly affected by localizad hardening due tocarbonation when the concrete is more than 3 months old.Although tests are easy to carry out, the results are influen-ced by many factors including surface texture, moistureconditions of the surface, cement type, mix characteristicsand type and rigidity of the structure. Concrete made withhigh alumina cement develops a surface layer considerablystronger than the underlying material, so results can tmmisleading. Minor surface indentations may ba cauaad,particularly with young or weak concreta.

2.15.4 Principal applications

The principal applications are as follows.

(a) Determination of concrete uniformity, which is mostreliably achieved by taking measurements on a regular

BS 1881 : Part201 : 1986Section two

grid on a mambar, or at corn~ble locations on similarmembers.

(b) Strength development monitoring, which is possibleif appropriate calibration charts can ba obtained. Whereresults can ba compared with predetermined limits foracceptance, tha mathod may ba used for quality control,formwork removal, etc.

(c) In situ strangth estimations, which era unlikely tohave 95 96 confidence limits of batter than k 7 MPagiven idaal tasting conditions and a specifically preparedcalibration chart for the concrete mix in use.

(d) Assasamant of abrasion resistance of concrete floorslebs. which may k corralatad with rabound number.

This test is often combined with ultrasonic pulse velocitytesting (sac 3.4 and 3.5).

216 Scteedtest

NOTE. This method is discussad in referancn 21 and 22 ofappendix A.

2.16.1 General

Measurement of the surface indentation caused by a definednumber of rapaetad controlled hammer blows at a point ona sand/cement scread may be empirically related to thesoundness of the scraad. Equipment is available in whicha mass of 4 kg is dropped 1 m down a vertical rod onto afoot which impacts the surface over a 500 mm’ area. Theindentation caused by a spacifiad number of blows may bemeasured with a simple dial gauge device. This test has beenspecifically developed as a performance test for assessingthe soundnets of sand/camant floor sawds, soundnessbeing usad to describe that property required of a screedto withstand the imposed loads and traffic in service.

2.16.2 Advantagas

This method provides a simple and quick approach whichinvolvas salf-containad hand-held aquipmant. The damagato sound scraads Is vary small.

2.16.3 Limitations

This test is not suitable for usa on concreta. Experience isrestricted to sand/carnent mortar scraads. On sound screeds,minor surface indentations up to 5 mm may be caused.The test cannot k uaad if the scraad is laid over a weak orsoft insulating Iayer,end the tast area has to ba flat andfree from all loose dirt and grit. The scraed should normallyba at least 14 days old, and measured indentations have toba related to predetermined acceptability limits (22). Theinterpretation of results requires experience and commonsense.

2.16.4 Principal application

The principal application is the assessment of durabilityand quality of floor sawds.

15

BS 1881 : Part 201 : 1986Section two

217 Internal fracture

NOTE. This method is discussed in reference 23 of appendix Aand will eventually be published in 6s 1661 : Pert 207.

2.17.1 General

A 6 mm diameter expanding wedge anchor bolt is fixedinto a drilled hole in the concrete surface and the peakforce is recorded when this bolt is pulled against a reactiontripod on the surface. The force may be calibrated againstcompressive strength for the particular load applicationtechnique employed, since failure is initiated by acombination of tensile and shear stresses for the standard-ized configuration of bolt depth and reaction tripoddimensions.

The most common technique for loading involves the useof a torquemeter on a greased nut bearing on the reactiontripod through a washer, but the twisting applied to thebolt increases the scatter of results compared with hydraulicor mechanical direct-pull methods (24,25).

2.17.2 Advantages.

This strength determination method is simple and cheap,requires only one exposed surface and is suitable for slendermembers. Strength calibrations are effectively independentof water/cement ratio, cement type and curing.

2.17.3 Limitations

The test depth is small (about 17 mm) and test variability isvery high, especially using the torquemeter loading method.The maximum acceptable aggregate size is 20 mm and anaverage of six readings is required at any location. Theloading rate and method are critical in relation to strengthcalibrations, and the 95 % confidence limits are unlikely tobe closer to the mean than f 28 % using a torquemeter.Testing technique and aggregate type influence thecorrelation with compressive strength, and specificcalibrations are recommended if reliance is to be plecadon strength estimates.

Surface damage may be limited to the drill holes if the testis stopped when the peak force is reached, but there remainsthe possibility that further surface damage may be causedby frost attack. If the bolt is pulled out of the concrete acrater approximately 80 mm in diameter will be formed.

2.17.4 Principal applications

The principal applications are as follows.

(a) Strength estimation of in situ concrete in situationswhere other methods are not practicable. This isparticularly likely in the case of slender members or forconcrete where specific calibrations for other methodsare impossible to obtain because of the large number ofvariables involved.

(b) Comparative surveys of in situ concrete.

(c) Quality control or strength monitoring purposes,which are possible if a suitable calibration chart isavailable.

218 Pull-out test

NOTE. This method is discussed in references 26 and 27 ofappendix A and will eventually be published in 6s 1661 : Part 207.

2.18.1 General

Pull-out tests involve measurement of the force required topull a metal insert from within the concrete against areaction ring. The shape and location of the insert and thereaction ring are designed and standardized to give a forcewhich can be related to the compressive strength of theconcrete. This calibration is relatively independent of mixcharacteristics for natural aggregates up to 36 mmmaximum size.

The insert may be cast in the concrete or may bepositioned in an underreamed groove from a drilled hole.Load is applied at a steady predetermined rate by hand-operated hydraulic equipment on to a removable bolt whichis connected to the insert. The peak value obtained isknown as the pull force and may be correlated againstcompressive strength. If the load is reduced at this stage,surface damage is small and the bolt can be removed,but if loading is continued, a cone of concrete will bepulled from the surface. Experience of these methods inthe UK is limited but they are in increasing use inScandinavia and North America.

2.18.2 Advantages

This method is quick and requires only one exposed surface.Cast-in inserts may ba fixed to soff it or side forms or on thetop surface, and tests may tm made through cutouts informs if required.

2.18.3 Limitations

The depth of test is small (25 mm) and the scatter ofindividual results is high, requiring an average of six readingsto be used. Estimated compressive strengths are unlikely tohave 95 96 confidence limits of better than f 20 % of themean when a general calibration is used or * 10 % when aspecially prepared calibration for the aggregate type in useis available. A minimum edge distance of 100 mm is requiredand reinforcement has to be avoided. Although testing isquick and the equipment simple to use, either pre-planningis required or drilling and underreaming are necessary. Thisoperation is basically straightforward but may present somepractical difficulties in situ, involving the use of a hand-heldelectric core cutter with water supply. The extent of surfacedamage will depend upon the test procedures adopted.

2.18.4 Principal applications

Cast-in inserts are most likely to be used for quality controlor strength monitoring purposas, especially related toacceptance, formwork stripping, post-tensioning ortermination of winter curing or protection. Values of pullforce should be compared with previously establishedlimiting velues for the particular circumstances. In somecircumstances, it may be appropriate to apply proof loadsto such inserts.

16

Inserts fixed into drilled holes may be used for thefollowing:

(a) comparative surveys of in situ concrete;

(b) in situ strength estimation based on an appropriatecalibration.

219 Pull-off test

NOTE 1. This method is discussed in references 28 end 29 ofappendix A and will eventually be. published in BS 1881 : Pan 207.

2.19.1 General

The pull-off test is a near-to-surface method in which acircular steel disc is glued to the surface of the concretewith an epoxy or polyester resin. The force required topull this from the surface, together with an attached layerof concrete, is measured. Simple mechanical hand-operatedloading equipment has been developed for this purpose.Partial coring may be used, if necessav, to eliminatesurface skin effects.

NOTE 2. Attention is drawn to the fact that it is claimed that thepull-off test is the subject of British Patent No. 1549842, copies ofwhich can be obtained from the Patent Office, 25 SouthamptonBuildings, London WCZA 1AY. BSI takes no position as lo thevalidity of the patent or whether it is still in force. The patent isendorsed ‘licences of right’ under Section 46 of the Patents Act1977, which states:

‘(31 Where such an entry is made in respect of a patent -(a) any person shall, at any time after the entry is made,be entitled as of right to a licence under the patent on suchterms as may be settled by agreement or, in default of agreement,by the Comptroller on the application of the proprietor of thepatent or the person requiring the licence’.

Licence details may be obtained from the registered proprietor ofthe patent.

2.19.2 Advantages

This method directly measures a strength-related property,requires only one exposed surfaca and is suitable for use onsmall-section members.

2.19.3 Limitations

Considerable care has to be given to surface preparationprior to fixing the steel disc. Sufficient time has to beallowed to enable the resin adhesive to cure prior to loadapplication. Results may ba correlated to strengthproperties measured on standard specimens. Correlationwith compressive strength is likely, however, to beinfluenced by aggregate type and it will probably benecessary to derive a calibration with strength for aparticular type of concrete to be investigated.

Laboratory tests on concrete cubes indicate that anaccuracy of strength prediction, based on the mean of threereadings, of * 15 % is possible. However, there isinsufficient evidence available to enable detailed guidanceto be given on the accuracy of the method under sitaconditions, although a greater variability is to be expected.

Localited surface damage will be caused, and test resultsare limited to the surface zone of the concrete with fracture

BS 1881 : Part 201 : 1986Section two

occurring approximately 5 mm below the surfam unlesspartial coring is used.

2.19.4 Principal applications

The principal applications are quality control, long termmonitoring and in situ strength assessment (particularlyof high alumina cement concrete and carbonated concretemade with ordinary Portland cement using partial coring).These all requim a ruiuMe correlation to be available.In some circumstances proof loads may be applied to aserler of permanent probes. The method also provides auseful fnaafn of tostlng mprirs to concfeta surfaces.

220 Break-off test

NOTE. This method is discussed in references 30 and 31 ofappendix A and will eventually be published in ES 1681 : Part 207.

2.20.1 Ganard

The break-off test has been developad in Scandinavia anddetermines directly the flexural tensile strength in a planeparallel to the concrete surface at a specified distance below

the surface. A 65 mm diameter core is effectively formedwithin the concrete to a depth of 70 mm either by meansof a disposable tubular form, which is cast into the concreteand then removed, or by cutting. An enlarged slot is formednear to the surface into which a hydraulically-operated jackwith a load all is inserted to provide a transverse force tothe top of the core. Measured values may be correlated tostrength tests on standard laboratory specimens; the mostreliable relationship is with flexural tests on prisms.

2.20.2 Advantagas

This method directly measures a strength-related propertyand requires only one exposed surface. It is daimad to baespecially suitable for young concretes and is quicker thanconventional core testing.

2.20.3 Limitations

This method will leave a sizable damage zone and willeither require pre-planning or the use of core-cuttingequipment. The test variability is high and it is recom-mended that the mean of five tests should be used torepresent the concrete at a given location. lnsuff icientevidence is available to permit guidance to be given onthe accuracy of in situ strength estimates obtained bythis method.

220.4 Principd applications

Principal applications are likely to be situations in whi&the tensile strength of the concrete is of importance,as follows:

(a) quality control of concrete pavements where resultscan be compamd with predetermined limits foracceptance;

(b) in situ strength assessment in situations where asuitable correlation is available.

17

BS 1881 : Part201 : 1986Section two

221 Penetration resistance

NOTE. This method is discussed in references 3, 25 and 32 ofappendix A and will eventually be published in BS 1861 : Part 207.

2.21.1 General

Penetration resistance involves firing a steel bolt (probe)into the surface of the concrete. A standardized charge isused and the depth of penetration is measured. This maybe calibrated against compressive strength, with therelationship principally affected by aggregate characteristics.Two power levels are available according to the concretestrength and the mean of three individual test results isnormally required at any location.

2.21.2 Advantages

This strength determination method is quick and relativelyinsensitive to operator techniques and factors such asmoisture content, cement type and curing. This may baparticularly valuable in situations where access is poor.The method may be used with up to 50 mm aggregate sizeand with rough or lightly textured surfaces or throughtimber forms. The test depth is uncertain but results arelikely to represent concrete between 25 mm to 75 mmfrom the surface.

2.21.3 Limitations

Damage in the form of cracking may be caused to slendermembers, and a minimum edge distance and memberthickness of 150 mm are required. Reinforcement has tobe avoided and simple safety precautions are necessary.Calibration for the aggregate in use is essential if resultsare to be used to assess compressive strength, and estimatedvalues are unlikely to have 95 % confidence limits of betterthan ? 20 %.

After measurement, the probe may be pulled from thesurface leaving a conical surface damage zone approximately75 mm in diameter.

2.21.4 Principal applications

The principal applications are as follows:

(a) comparative strength estimation in situations wheretruly nondestructive methods are unsuitable orimpracticable;

(b) quality control or strength development monitoring,where results can be compared with predetermined limitsfor acceptance, formwork removel, etc.;(I:) ttrnngth nrtirnatian of in tltu concrrte In 01~s wherean appropriate calibration is available.

2.22 Depth of carbonation

NOTE. This method is discussed in reference 33 of appendix A,

2.22.1 General

Carbonation of surface zone concrete will be accompaniedby a loss of alkalinity of the concrete affected. This may bedetected by the use of a suitable indicator, e.g.

phenolphthalein, which can be sprayed on to a freshlyexposed cut or broken surfaa of the concrete.

2.22.2 Advantages

This method is quick and simple and gives an immediatevisual indication.

2.22.3 Limitations

A suitable surface has to be provided by cutting or breakingand testing immediately. This procedure will ceuse localizedsurface damage. This method provides only an indication ofthe extent of carbonation.

2.22.4 Principal applications

A knowledge of the depth of carbonation combined withthe age of the concrete may be useful when assessingpotential durability and the likelihood of corrosion ofreinforcement. This test may also be useful in conjunctionwith some of the near-to-surface test methods to ensurethat the depth of carbonation is insufficient to influenceresults.

2.23 Acoustic emission

NOTE. This method is discussed in references 3 and 34 ofappendix A.

2.23.1 General

This method involves the detection of small amplitudeelastic stress waves which are propagated throughout amaterial as localized crushing or microcracking occursunder load. This emission is generally not in the audiblerange and may be monitored by transducers positionedon the concrete surface and connected to electronicprocessing and recording equipment. As the load level ona concrete element increases, both the emission rate andsignal level increase steadily. A rapid increase in bothparameters precedes failure.

2.23.2 Advantages

Crack initiation and propagation can be monitorednondestructively during a period of increasing stresswithin a concrete element. It may also be possible toidentify the location of crack initiation and propagationby the use of multiple detectors.

2.23.3 Llmltatlons

Concrrta may rooovor aorne aapaatr of Ita pr*crroklnginternal structure, and rrloadlng over a particular stressrange may again generate emissions. Consequently, it isnot always possible to establish a history of past stresslevels, contrary to the behaviour of many other materials.

This method would not normally be used for eitherindividual or comparative measurements under static loadconditions.

The propagation of acoustic waves in concrete is limited tolow ultrasonic frequencies where the noise background isoften high. The method is not, therefore, suitable for use

18

on most building sites nor for the pncisa location ofpropagation cracks even in quiet araas.Specialist equipment is required, and applications of thetechnique to concrete outside of the I8bontoryhmm notyet been fully developed. _

2.23.4 Principal application

The principal application is likely to be monitoring of theinitiation, origin and davelopmant of lntamd cnoking andlocal breakdown during load tin& md to p&de owarning of impending failure. . .

2 2 4 S t r a i n m e a s u r e m e n t s “I .i

NOTE. This method is currently described In 6B 4408.: put 2,but will eventually be revised as BS 1881 : Pw2M.

2.24.1 General

Useful deductions concerning the suitability of concrataelements can be made by measuring strgin. Strain gpugascan measure strain, or apparent strain, wsad by crackpropagation, thermal changes, etc. Thw w ona 01 ~FIof the following to amplify and display thr wnt:

Bs1881:Put201:1ae6SIctlontwa ’

BS 1881 : Part 201 : 1986Section three

Section three. Combinations of methods

3.1 General

Situations in which it may be worthwhile to usecombinations of test methods are outlined in 1.4.3.3.The most suitable methods will vary according to thecircumstances but the following suggestions may beconsidered as typical.

3.2 Electromagnetic cover measurementor radiography to locate reinforcement

Electromagnetic cover measuring devices will frequently bevaluable in conjunction with the near-to-surface testmethods to ensure that reinforcement is avoided at testlocations. The limited depth range of such equipment willnot normally be a problem in this situation. This approachmay similarly be valuable in relation to core drilling andultrasonic pulse velocity measurements.

If the reinforcement is embedded at a depth beyond therange of this equipment, it may be necessary to useradiography to provide an indication of location, but thisis only likely to be justified in particularly criticalsituations.

3.3 Non-destructive methods aspreliminary to partially-destructivemethods

It may often be worthwhile to perform an extensive surveyquickly and cheaply with a rebound hammer or ultrasonicpulse velocity equipment prior to the use of other methodsinvolving greater expense or damage but which give a morereliable indication of the required property of the concrete.This approach will enable suspect zones to be identified andcan provide a calibration datum, thereby reducing the timeand cost of examining a large body of concrete. The choiceof a preliminary method has to be determined, takingaccount of the practical circumstances and the limitationsof the test methods, and may also include radiography,radiometry or thermography. The subsequent testing willdepend largely upon the property required but may includecore cutting, pullout, internal fracture, break-off orpenetration resistance, where strength is important. Whenin situ strength development is to be monitored, maturitymeasurements may provide useful preliminary data priorto confirmation by more disruptive strength assessmenttests, such as pull-outs 115, 35).

3.4 Increasing the confidence level of testresults

As a general rule, the cheapest and quickest suitable testmethods will have been chosen. The observed patterns ofvariation of quality may be confirmed by the use ofadditional methods. For example, on recently cast concretethe use of rebound hammer and ultrasonic pulse velocity

may be the most appropriate combination. In othercircumstances it may be necessary to combine one or theother of these with near-to-surface testing or radiometry.The patterns of results obtained should be compareddirectly, and results should not be converted to some otherproperty before comparison. Confidence will be muchincreased if similar patterns emerge.

In situations where the volume of concrete is relativelysmall, and where a specific property, e.g. strength, is ofprimary interest, it may be worthwhile to compare twoor more estimates of that property using different methods.

3.5 Improvement of calibration accuracy

In some cases where the correlation between measuredvalues and required property is sensitive to a number ofvariables, it may be possible to achieve an improvedaccuracy of estimated property by mathematicalcombination of results.

The accuracy of strength prediction from ultrasonic pulsevelocity may be improved by combination with values ofdensity (36) obtained from the same specimens or sections,provided sufficiently accurate measurements can be made.Ideally, a velocity/strength relationship should be derivedfor each value of density, However, rebound hammerreadings, which are surface-density related, have most oftenbeen used in combination with ultrasonic pulse velocitymeasurements.

In cases where strength calibrations are available for bothmethods relating to the concrete in use, multiple regressionequations can be developed with compressive strength asthe dependent variable (37, 38). This is likely to be ofparticular value for quality control applications. Correlationgraphs may also be produced involving coefficients relatingto various properties (39).

3.6 Half-cell potential and resistivity teststo indicate likelihood of reinforcementcorrosion

Half-ceil potential surveys will usually indicate the level ofpossibility of the occurrence of reinforcement corrosionas a result of electrochemical action. Subsequent resistivitymeasurements in zones which are demonstrated to be atrisk may sometimes indicate the likelihood of corrosionactually occurring. While combination of these methodscannot positively confirm that corrosion has occurred oris occurring, or assess the extent of any corrosion, theyrepresent the most effective nondestructive approachcurrently available (6.40). Other tests of a chemical natureare available for the concrete, e.g. chloride content analysisand carbonation depth, while steel monitoring tests, e.g.electrical resistance probes and linear polarization probes,may have to be incorporated at the time of construction (5).Tests of this type may be valuable in conjunction with half-cell potential and resistivity measurements, but are outsidethe scope of this standard.

20

Appendix

Appemdix A Bibliography

1. AMERICAN SOCIETY FOR TESTING ANDMATERIALS.Air~~~~tk,hwdnrdcancnar,

ASTM C&7,1980.

2. AMERICAN SOCIETY FOR TESTING ANDMATERIALS. PotrogrqDhk l xu&setAu~ of hnknrdconcmte, ASTM C866.1077.

3. BUNGEY, J.H. The testing of commts h Umctum,1882.

4. McCARTER, WJ., FORDE, MC. & WHITTINGTON,H.W. Resistivity characteristics of ooncrote. ProE. l&E.,Port 2, 1981.71, 107-l 17.

5. VASSIE, P.R. A survey of site tests for the euessmrntof corrosion in reinforced concrete. Trsd Rard

6.

7.

8.

0.

10.

11.

12.

13.

14.

15.

Res. Lab., Lab. Rep. 953, 1080.

FIGG, J.W. 81 MARSDEN, A.F. Development ofinspection techniques - a state-of-the-m survey ofelectrical potential and resistivity measurements foruse above water level. In: CIRIA, Concmuin dm .Omms, &we II, T&nicd Notv P6d. Fill Rqmrt,90,1983.

MALHOTRA, V.M. Testing hardened conorete -nondestructive methods. AC/ Monoonph No. 9, 1078.

McCARTER, W.J., WHITTINGTON, H.W. 8FORDE, MC. An experimental investigetion of theearth resistance response of reinforod oonorete piles.Proc. I.C.E., Part2, 1981,71,1101-1128.

AMERICAN SOCIETY FOR TESTING ANDMATERIALS. Standud test mathad for l&fsvJlpotanti& of twin forcing stml in cmctvt~,ASTM C676.1080.

SHERWOOD, P.T. & CLARK, A.J. The meesurementof the in situ density of cement bound meteriels.Trutrport & Road Ros Lab., Lab. Rip. t 169,1984.

F IGG, J.W. Methods of measuring the eir end waterpermeebility of concrete. Mrg. of Cancmr Ru,1073.26, No. 86.213210.

CATHER, R., FIGG, J.W., MARSDEN,A.F. 81O’BRIEN, T.P. Improvements to the Figg method ofdetermining the air permeebility of oonorete. Mw ofConcmte Rm, lBB4,36, No. 129,241.246.

HANSEN, AJ., OTTOSEN, N.S. 81 PETERSEN, C.G.Gas permeability of concrete in situ: ttteor~ endpractice. In: ACI In situ/non-des~,tl~ tat& Ofconcmw, sP42,643-666,1884.

NAIK, T.R. Concrete strength prediction by thematurity method. Pm. ASCE, 1866,166, EM3,466480.

PETERSEN, C.G. &?I HANSEN, AJ. Timing of loadingdetermined by pull-out and maturity tests. In: Proc.

lnt. Conf. on concrete at early ro#, RILEM, 1082,1.173-175.

16

17.

16.

BS 1881: Put 201:. lfta

Appemdix

MANNING, D.G. & HOLT, F.B. Dotmctingdelrmlnatlon in concmtebridgeWWIntonwtW, lBW,2, No. 11,3c11.

GODFREY, J.R. Naw tools hdp find fbs. Civ#Enahwhv. 1664,64, No. 0,3B42.

HILLEMEIER, 8. & MtiLLER-RUN, U.Bewehrungwcha mit der thermoqa@tk. &as usd- __.StWbaton, 1980, m, No. 4,6366.

10. CANTOR, T.R. Roviow of perwmting r&u a appiiedto the nondestrwtiw tasting of -ta. In: ACIIn 8itu/Wh tmt& of ccma8te,sP%1,5B1-602,1984.

20. STAIN, R.T. Integrity tasting. Civ# Ea. AprillBB2,64)60; May 1982.71-73.

21. PYE, P.W. 81 WARLOW, W.J. A method of waassina

22.

23.

24.

26.

26.

27.

28.. . .

29.

30.

31.

the roundness of some dense floor weeds. &&I&Ra EM&mm tirmt pq#r CWW%. 1076.

PYE, P.W. BRE Scmed taster: dasaifiation of sweds,sempling end aceeptana limits. 8uJdN RaEmblMmmt Inhmatim &m IPllAU. 19&1.

CHABOWSKI, A.J. & BRYDEN SMITH, D.W. lnmrndfracture testing of in situ conctete. Buildiw Ra&t&Mm Infomwtiiw W IP22A!W. 1980.

BUNGEY, J.H. Cbncrate strength konminatictn bypull-out wts on wedge-andtor bolts. k?c. I.C.E.Pmt2,1861,71,37B-a.

KEILLER, A.K. Assessing the strength of in situconctmw. &mcmw Intmathn&, 1986.7. No. 2.1621.

BUNGEY, J.H. An appraisal of pull-out methods oftesting conmew. In: bc. NOT&?, 12-21, EnginewinsTechnics Proas, Edinburgh, 1883.

PETERSEN, C.G. L&test and Cape-test devebpmentend their rppkationr. Proc. I.C.E. PM 1.1984.76,636-640.

LONG, A.E. & MURRAY, A. McC. The pull-off

LONG, A.E. Improvements in or relating to suengd~testing brittle nutnriais. 8* AtmtSsrdfiutianNo. l-, 1070.

CARLSSDN, M.. EEG, I.R. 81 JAHREN. P. Fieldexperkna in the use of the bmakoff tesmr. In: ACIIn 8ltuhamWbwth m&v of amvuv, 6P81.2770202,1664.

DAHL-JORGANSEN, E. & JOHANSEN, R. Garteraland apocirlked use of the break-off concrom strqptltosting mottwd. In: ACI In situ/W bbilgof co?mwt8,6PB2,263-308,1B84.

32: SWAMY, R.N. 6 AL-HAMED, A.H.M.S. Evafuation oftheWindsorpwbetosttowsessinsit.uconcr8testmngth.pr#t I.cE.,Put2,1m4,77,167-19).

21

t53 ImI : rarr zul : 1YtmAppendix

33.

34.

35.

36.

ROBERTS, M.H. Carbonation of concrete made withdense natural aggregates. Building Res Estabiidmmt,Information Paper IP6/8 1, 1981.

MLAKAR, P.F., WALKER, R.E.,SULLIVAN, 8.R.&CHIARITO, V.P. Acoustic emission behaviour ofconcrete. In: ACI In situ/non-dertnrctive tvstiq ofconcrete, SP-82, 619637, 1984.

PARSONS, T.J. & NAIK, T.R. Early age concretestrength determination by pull-out testing andmaturity. in: ACI In situ/non-ktructiw Ming ofconcrete, SP-82,177-200.1984.

REYNOLDS, W.N. Measuring concrete qualitynondestructively. In: hit. J. of Non-&srnrcriwTesting, 1984,28, 1 l-14.

22

.

22

37.

38.

35.

40.

SAMAR IN, A. & OH I R, R.K. Determination of in situconcrete strength: rapidly and confidently by non-destructive testing. In: ACI In dtu/n~testing of concmv, 6W2,77-64,1984.

TANIGAWA, Y., BABA, K. & HIROSHI, M.Estimation of concrete by combined nondestructivetesting mrthod. In: ACI In rlrumorxkdnrcbiu tmtingof concrua, 6P-62,67-76 4.

FACAOARU, I. Romanial: .evements in non-destructive strength testing tit- concrete. in: ACI In situ/non-dtmtiw tuting ofcovidtw, 6PB2,36-68,1984.

VASSIE, P. Reinforcement corrosion and durability ofconcreta bridgrr.proC. I.C.E. Pur I, l-,76,713-723.

Publications referred to0s 1981 Testing concrete

Part 5 Methods of tasting hardened concmte for other than strengthPart 108 Method for making test cubes from fresh concretePart 111 Method of normal curing of test specimens (20 ‘C method)Part 116 Method for determination of compressive strength of concrete cukrPart 202 Recommendations for surfece hardness testing by rebound hemmerPart 203’ Recommendations for the meesurement of velocity of ultreaonic pulses in concmtePart 204’ Recommendations for the use of electromegnetic cover meeeuring dwiiesPart 205’ Recommendations for the rediogrephy of concrete

Part 206’ Recommendations for the determinetion of strein in cwmtePart 207’ Recommendations for near to surface tests for concretePart 208’ Recommendations for the determination of initiel rurfece l baorptiort of concretePart 209’ Recommendations for the dynamic modulus of l leeticitv

0s 2707 Gfossarv of terms for concrete and reinforced concrete0s 4408 Recommendations for nondestructive methods of test for concrete

Part 1 Electromagnetic cover meesuring devicesPart 2 Strain gauges for concrete investigetionsPart 5 Mrasurement of the velocity of ultresonic pulses in concmte

BS 6089 t Guide IO assessment of concmte strength in existing structureaBS 6100 Glossary of building and civil erqffneering terms

Part 6 Concrete and plater

NOTE. !%ee also bibliography in tgpendix A

-1

-

i

l In preparatron.

t Referred to in the foreword only.

This Brltlsh Standard, having been prepared under the direction ofthe Cement, Gypsum. Aggregates and Quarry Products StandardsCommrttee, was published under the authority of the Board of BSI

and comes Into effect on 28 February 1986.

zBr,rlsh Standards Instrtutron. 1886

lS8N 0 580 14767 3

Brmsh Standards InstitutionIncorporated by Royal Charter, BSI is the independent nationalbody for the preparation of British Standards. It is the UK memberof the International Organiration for Standardization and UKsponsor of the Brutish National Committee of the InternationalElactrotechnrcal Commrssion.

CopyrightUsers of Brrtrsh Standards are reminded that copyright subsista inall BSI publicatrons. No part of this publication may be reproducedI” any form wrthout the prior permission in writing of BSI. Thisdoes not preclude the free use, in thecourse of implementing thestandard, of necessary detatls such as symbols and size, type orgrade designatrons. Enquiries should be addressed to thePublrcationr Manager, British Standerds Institution, Linford Wood,

BS 1881: Part 201

: 1986

'

Milton Keynes MK14 BLE. The number for telephone enquiries 1s0808 320033 and for telex 825777.

Contract requirementsA British Standard does not purport to include all the necessaryprovisions of a contract. Usets of British Standards are responwblefor their correct application.

Revision of British StandardsBritish Standards are revised, when necessary, by the issue arther

of amendments or of revised editions. It is imporsant that usus ofBritish Stendamls should escertein tftp they are in poasea& ofshe latest l mewlments or ditions. Information on all BSIpublications is in the 89 Catalogue, supplemented each month byBSI News which is available to subscribing members of thaInstitution and gives deteils of new publiutions. revrsions.amendments and withdrewn standards. Any person who, whenmaking use of a British Standard, encounters an maccuracy orambigurty, is requested to notify BSI without delay rn order thatthe matter may be investigetetf and appropriate actron taken.

The following BSI references relate to the work on this standard:Committee reference CAB/4 Draft for comment B4/10723 DC

Committees responsible for this British StandardThe preparatron of this British Standard was entrusted by theCrmrur. Gypsum. Aggregates and Quarry Products StandardsCommrttee ICAB,‘-I to Technical Committee CAB/4 upon whichthe following bodies were represented:

Association of Lightweight Aggregate ManufacturersArsociatron of Metropolitan AuthoritiesBritish Aggregate Construction Materials IndustriesBrutish Precast Concrete FederatronBr~trsh Ready Mixed Concrete AssociatronBulldIng Employers’ ConfederationCement Admixtures AssociationCement and Concrete AssoclatlonCement Makers’ FederattonConcrete SocletvCounry Surveyor’s SocietyDepartment 01 the Environment (Bullding Research Establishment)Deparrmenr 01 the Environment (Property Services Agency)Department of the Environment (Transport and Road Research

Laboratory I

Amendments issued since publication

Department of Transport ff-lighwaysfElectricity Supplv Industry in England and WalesFederation of Civil Engineering ContractorsInstitute of Concrete TechnologyInstitution of Civil EngineersInstitution of Highweys and TrensportationInstitution of Structural EngineersInstitution of Weter Engineers end ScientistsRoyal Institute of British ArchitectsRoyal Institution of Cherterd SurveyorsSand and Gravel AssociationSociety of Chemical Industry

The following bodies were also represented in the drafting of thestandard, through subcommittees end panels:

British Civil Engineering Test Equipment Manufacturers’ AssociatronBritish Nuclear Fuels LimitedUnited Kingdom Atomic Energy Authoritv

Amd. No. Datr! of issue I Text affected

Erltish Standards Institution . 2 Park Street London WlA 26s . Telephone 01-629 9000 . Telex 266933

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