1、Designation: C1778 14Standard Guide forReducing the Risk of Deleterious Alkali-Aggregate Reactionin Concrete1This standard is issued under the fixed designation C1778; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las
2、t revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide provides guidance on how to address thepotential for deleterious alkali aggregate reaction (AAR) inconcrete co
3、nstruction. This guide addresses the process ofidentifying both potentially alkali-silica reactive (ASR) andalkali-carbonate reactive (ACR) aggregates through standard-ized testing procedures and the selection of mitigation optionsto minimize the risk of expansion when ASR aggregates areused in conc
4、rete construction. Mitigation methods for ASRaggregates are selected using either prescriptive orperformance-based alternatives. Preventive measures for ACRaggregates are limited to avoidance of use. Because thepotential for deleterious reactions depends not only on theconcrete mixture but also the
5、in-service exposure, guidance isprovided on the type of structures and exposure environmentswhere AAR may be of concern.1.2 UnitsThe values stated in either SI units or inch-pound units are to be regarded separately as standard. Thevalues stated in each system may not be exact equivalents;therefore,
6、 each system shall be used independently of the other.Combining values from the two systems may result in noncon-formance with the standard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard t
7、o establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C33/C33M Specification for Concrete AggregatesC125 Terminology Relating to Concrete and Concrete Ag-gregatesC150/C150M Specification
8、 for Portland CementC294 Descriptive Nomenclature for Constituents of Con-crete AggregatesC295 Guide for Petrographic Examination of Aggregates forConcreteC311 Test Methods for Sampling and Testing Fly Ash orNatural Pozzolans for Use in Portland-Cement ConcreteC586 Test Method for PotentialAlkali Re
9、activity of Carbon-ate Rocks as Concrete Aggregates (Rock-CylinderMethod)C595 Specification for Blended Hydraulic CementsC618 Specification for Coal Fly Ash and Raw or CalcinedNatural Pozzolan for Use in ConcreteC823/C823M Practice for Examination and Sampling ofHardened Concrete in ConstructionsC85
10、6 Practice for Petrographic Examination of HardenedConcreteC989 Specification for Slag Cement for Use in Concrete andMortarsC1105 Test Method for Length Change of Concrete Due toAlkali-Carbonate Rock ReactionC1157 Performance Specification for Hydraulic CementC1240 Specification for Silica Fume Used
11、 in CementitiousMixturesC1260 Test Method for Potential Alkali Reactivity of Ag-gregates (Mortar-Bar Method)C1293 Test Method for Determination of Length Change ofConcrete Due to Alkali-Silica ReactionC1567 Test Method for Determining the Potential Alkali-Silica Reactivity of Combinations of Cementi
12、tious Mate-rials and Aggregate (Accelerated Mortar-Bar Method)2.2 ACI Standard:3ACI 318 Building Code Requirements for Structural Con-crete and Commentary1This guide is under the jurisdiction of ASTM Committee C09 on Concrete andConcrete Aggregates and is the direct responsibility of Subcommittee C0
13、9.50 onRisk Management for Alkali Aggregate Reactions.Current edition approved Oct. 1, 2014. Published November 2014. DOI:10.1520/C1778-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume
14、 information, refer to the standards Document Summary page onthe ASTM website.3Available from American Concrete Institute (ACI), P.O. Box 9094, FarmingtonHills, MI 48333-9094, http:/www.concrete.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. U
15、nited States12.3 AASHTO Standard:AASHTO PP 65 Standard Practice for Determining theReactivity of Concrete Aggregates and Selecting Appro-priate Measures for Preventing Deleterious Expansion inNew Concrete Construction42.4 CSA Standards:5A23.2-26A Determination of PotentialAlkali-Carbonate Re-activit
16、y of Quarried Carbonate Rocks by Chemical Com-positionA23.2-27A Standard Practice to Identify Degree of Alkali-Aggregate Reactivity of Aggregates and to Identify Mea-sures to Avoid Deleterious Expansion in ConcreteA23.2-28A Standard Practice for Laboratory Testing toDemonstrate the Effectiveness of
17、Supplementary Cement-ing Materials and Lithium-Based Admixtures to PreventAlkali-Silica Reaction in Concrete3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this Guide, refer toTerminology C125 and Descriptive Nomenclature C294.3.2 Definitions of Terms Specific to This Standard:3
18、.2.1 alkali content, nthe alkali content of the cementexpressed as % Na2Oeqand calculated as Na2O + (0.658 K2O).3.2.2 alkali loading, nthe total amount of alkalies in theconcrete mixture expressed in kg/m3or lb/yd3; this is calcu-lated by multiplying the portland cement content of theconcrete in kg/
19、m3or lb/yd3by the alkali content of the cementdivided by 100.3.2.3 deleteriously reactive, adjused to describe aggre-gates that undergo chemical reactions that subsequently resultin premature deterioration of concrete.3.2.3.1 DiscussionThe term used in this standard guidedescribes aggregates that un
20、dergo chemical reactions withhydroxide (OH-) in the pore solution.3.2.4 non-reactive, adjused to describe materials that donot undergo chemical reactions that subsequently result inpremature deterioration of concrete.3.2.4.1 DiscussionSome aggregates with minor amountsof reactive constituents may ex
21、hibit the symptoms of alkali-aggregate reaction (AAR) without producing any damage tothe concrete; these are termed as non-reactive aggregates.4. Summary of Guide4.1 Alkali-aggregate reactions (AAR) occur between thealkali hydroxides in the pore solution of concrete and certaincomponents found in so
22、me aggregates. Two types of AAR arerecognized depending on the nature of the reactive component:alkali-silica reaction (ASR) nvolves various types of reactivesiliceous (SiO2containing) minerals and alkali-carbonate re-action (ACR) involves certain types of rocks that containdolomite CaMg(CO3)2. Both
23、 types of reaction can result inexpansion and cracking of concrete elements when exposed tomoisture, leading to a reduction in the service life of concretestructures.4.2 This guide describes approaches for identifying poten-tially deleteriously reactive aggregates and selecting appropri-ate preventi
24、ve measures to minimize the risk of expansionwhen such aggregates are used in concrete in exposureenvironments where AAR may be of concern. Preventivemeasures include avoiding use of the reactive aggregate,limiting the alkali loading of the concrete, using supplementarycementitious materials, using
25、lithium-based admixtures, or acombination of these strategies.5. Significance and Use5.1 This guide provides recommendations for identifyingthe potential for deleterious AAR and selecting appropriatepreventive measures, based on a prescriptive-based or perfor-mance approach, to minimize the risk of
26、deleterious reaction.In regions where occurrences of AAR are rare or the aggregatesources in use have a satisfactory field performance recordverified by following the guidance in this standard, it isreasonable to continue to rely on the previous field historywithout subjecting the aggregates to labo
27、ratory tests for AAR.In regions whereAAR problems have occurred or the reactivityof aggregates is known to vary from source to source, it may benecessary to follow a testing program to determine potentialreactivity and evaluate preventive measures. In this guide, thelevel of prevention required is a
28、 function of the reactivity of theaggregate, the nature of the exposure conditions (especiallyavailability of moisture), the criticality of the structure, and theavailability of alkali in the concrete.5.2 Risk EvaluationTo use this guide effectively, it isnecessary to define the level of risk that i
29、s acceptable, as thiswill determine the type and complexity of testing (Note 1). Therisk of deleterious expansion occurring as a result of a failureto detect deleteriously reactive aggregates can be reduced byroutine testing using petrography, or laboratory expansiontests, or both.NOTE 1The level of
30、 risk of alkali-silica reaction will depend upon thenature of the project (criticality of the structure and anticipated exposure).The determination of the level of risk is generally associated with theresponsible individual in charge of the design, commonly a representativeof the owner, and for stru
31、ctures designed in accordance with ACI 318, thelevel of acceptable risk would be determined by the licensed designprofessional.5.3 Preventive measures determined by either performancetesting or the prescriptive approach described in this guide canbe expected to generally reduce the risk of expansion
32、 as a resultof ASR to an acceptable level for conventional structures. Forcertain critical structures, such as those exposed to continuousmoisture (for example, hydraulic dams or power plants), inwhich ASR-related expansion cannot be tolerated, more con-servative mitigation measures may be warranted
33、.5.4 There are no proven measures for effectively preventingdamaging expansion with alkali carbonate reactive rocks inconcrete and such materials need to be avoided by selectivequarrying.4Available from American Association of State Highway and TransportationOfficials (AASHTO), 444 N. Capitol St., N
34、W, Suite 249, Washington, DC 20001,http:/www.transportation.org.5Available from Canadian Standards Association (CSA), 5060 Spectrum Way,Suite 100, Mississauga, ON, L4W 5N4, Canada, http:/www.csa.ca.C1778 1425.5 If an aggregate is identified as potentially deleteriouslyreactive as a result of ASR, an
35、d the structure size, class, andexposure condition requires preventive measures, the aggre-gate may be accepted for use together with appropriatepreventive measures following the prescriptive or performancemethods outlined in this guide.6. Procedure6.1 The flow chart in Fig. 1 shows the general sequ
36、ence oftesting and decisions that should be made when evaluating asource of aggregate for potential AAR. Prior documentedsatisfactory field performance of the aggregate in concrete isAThe type of reaction only needs to be determined after the concrete prism test if the aggregate being tested is a qu
37、arried carbonate that has been identified as beingpotentially alkali-carbonate reactive by chemical composition in accordance with test method CSA A23.2-26A.BThe solid lines show the preferred approach. However, some agencies may want to reduce the amount of testing and accept a higher level of risk
38、 and this canbeachieved by following the direction of the hashed lines.FIG. 1 Sequence of Laboratory Tests for Evaluating Aggregate ReactivityC1778 143generally considered to be sufficient for its acceptance in newconcrete. However, reliance on prior field performance withoutfollowing the guidance a
39、nd recommended testing in 7.1 maynot be sufficient to safeguard against damage as a result ofAAR in new construction. This is due to the difficulties inassuring that the materials and mixture proportions used inexisting structures built 10 to 20 years ago (the time frameneeded to ensure that a delet
40、erious reaction as a result of AARhas not occurred) are similar to those being proposed for usetoday. In most cases, it will be necessary to perform laboratorytests to determine whether the aggregate is potentially delete-riously reactive for the specific concrete mixture to be used.There are severa
41、l test methods available for evaluating poten-tialAAR; petrographic examination, determination of chemicalconstituents, and mortar bar and concrete prism expansion testsare recommended in this guide. If the aggregate is deemed tobe non-reactive, it can be accepted for use in concrete with nofurther
42、consideration of mitigation provided that the otherphysical properties of the aggregate render it suitable for use(refer to Specification C33/C33M). If the aggregate is aquarried carbonate, additional tests are required to determinewhether the potential reaction is of the alkali-carbonate oralkali-s
43、ilica type.6.2 Steps for selecting appropriate preventive measures forASR follow either a performance-based (Section 8)orprescriptive-based (Section 9) approach. In the performance-based approach, a potential preventive measure is tested todetermine if the measure provides a reduction in expansionbe
44、low the limits outlined in this guide. Both approaches areintended to minimize the potential for deleterious expansion infield concrete.7. Determining Aggregate Reactivity7.1 Use of Field Performance History:7.1.1 The long-term field performance history of an aggre-gate can be established by surveyi
45、ng existing structures thatwere constructed using the same aggregate source. As manystructures as practical should be included in the survey andthese structures should, if possible, represent different types ofconstruction (for example, foundations, walls, bridges,pavements, sidewalks, and structura
46、l elements). Practice C823/C823M provides useful guidance when surveying structures toestablish field performance history. The following informationshould be documented for each structure:7.1.1.1 AgeStructures should be at least 15 years old asvisible damage from AAR can take more than ten years tod
47、evelop.7.1.1.2 Cement content and alkali content of the cementused during construction.7.1.1.3 Use and content of pozzolans or slag cement orblended cements during construction.7.1.1.4 Exposure ConditionAvailability of moisture anduse of deicing chemicals.7.1.1.5 Symptoms of distress as a result of
48、AAR or othercauses.7.1.2 Cores should be taken from a representative number ofthese structures and a petrographic examination conductedusing Practice C856 to establish the following (Note 2):7.1.2.1 The aggregate used in the structure surveyed is ofsimilar mineralogical composition, as determined by
49、 GuideC295, to that of the aggregate to be used.7.1.2.2 Any evidence of damage as a result of AAR; and7.1.2.3 The presence, quantity, and composition (if known)of fly ash, slag cement, or other supplementary cementitiousmaterials.NOTE 2Even if signs of deterioration are not observed, cores shouldbe taken to establish uniformity of materials.7.1.3 If the results of the field survey indicate that theaggregate is non-reactive, the aggregate may be used in newconstruction provided that the new concrete is not producedwith a higher concrete alkali content, a lower SCM re
