1、Designation: C1778 14C1778 16Standard 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 yea
2、r of last 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 the potential for deleterious alkali aggregate reaction (AAR) in c
3、oncreteconstruction. This guide addresses the process of identifying both potentially alkali-silica reactive (ASR) and alkali-carbonatereactive (ACR) aggregates through standardized testing procedures and the selection of mitigation options to minimize the risk ofexpansion when ASR aggregates are us
4、ed in concrete construction. Mitigation methods for ASR aggregates are selected usingeither prescriptive or performance-based alternatives. Preventive measures for ACR aggregates are limited to avoidance of use.Because the potential for deleterious reactions depends not only on the concrete mixture
5、but also the in-service exposure, guidanceis provided on the type of structures and exposure environments where 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. The values statedin each system may not be exact equivale
6、nts; therefore, each system shall be used independently of the other. Combining valuesfrom the two systems may result in nonconformance with the standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of
7、this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C33/C33M Specification for Concrete AggregatesC125 Terminology Relating to Concrete and Concrete AggregatesC150/C150M Sp
8、ecification for Portland CementC294 Descriptive Nomenclature for Constituents of Concrete AggregatesC295 Guide for Petrographic Examination of Aggregates for ConcreteC311 Test Methods for Sampling and Testing Fly Ash or Natural Pozzolans for Use in Portland-Cement ConcreteC586 Test Method for Potent
9、ial Alkali Reactivity of Carbonate Rocks as Concrete Aggregates (Rock-Cylinder Method)C595 Specification for Blended Hydraulic CementsC618 Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in ConcreteC823/C823M Practice for Examination and Sampling of Hardened Concrete in C
10、onstructionsC856 Practice for Petrographic Examination of Hardened ConcreteC989 Specification for Slag Cement for Use in Concrete and MortarsC1105 Test Method for Length Change of Concrete Due to Alkali-Carbonate Rock ReactionC1157 Performance Specification for Hydraulic CementC1240 Specification fo
11、r Silica Fume Used in Cementitious MixturesC1260 Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method)C1293 Test Method for Determination of Length Change of Concrete Due to Alkali-Silica ReactionC1567 Test Method for Determining the Potential Alkali-Silica Reactivity of Comb
12、inations of Cementitious Materials andAggregate (Accelerated Mortar-Bar Method)1 This guide is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee C09.50 on RiskManagement for Alkali Aggregate Reactions.Current edition app
13、roved Oct. 1, 2014July 1, 2016. Published November 2014August 2016. Originally approved in 2014. Last previous edition approved in 2014 asC177814. DOI: 10.1520/C1778-14.10.1520/C1778-16.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceast
14、m.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becaus
15、eit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Bar
16、r Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.2 ACI Standard:3ACI 318 Building Code Requirements for Structural Concrete and Commentary2.3 AASHTO Standard:AASHTO PP 65 Standard Practice for Determining the Reactivity of Concrete Aggregates and Selecting Appropriate M
17、easuresfor Preventing Deleterious Expansion in New Concrete Construction42.4 CSA Standards:5A23.2-26A Determination of Potential Alkali-Carbonate Reactivity of Quarried Carbonate Rocks by Chemical CompositionA23.2-27A Standard Practice to Identify Degree of Alkali-Aggregate Reactivity of Aggregates
18、and to Identify Measures toAvoid Deleterious Expansion in ConcreteA23.2-28A Standard Practice for Laboratory Testing to Demonstrate the Effectiveness of Supplementary Cementing Materialsand Lithium-Based Admixtures to Prevent Alkali-Silica Reaction in Concrete3. Terminology3.1 Definitions:3.1.1 For
19、definitions of terms used in this Guide, refer to Terminology C125 and Descriptive Nomenclature C294.3.2 Definitions of Terms Specific to This Standard:3.2.1 alkali content, nthe alkali content of the cement expressed as % Na2Oeq and calculated as Na2O + (0.658 K2O).3.2.2 alkali loading, nthe total
20、amount of alkalies in the concrete mixture expressed in kg/m3 or lb/yd3; this is calculated bymultiplying the portland cement content of the concrete in kg/m3 or lb/yd3 by the alkali content of the cement divided by 100.3.2.3 deleteriously reactive, adjused to describe aggregates that undergo chemic
21、al reactions that subsequently result inpremature deterioration of concrete.3.2.3.1 DiscussionThe term used in this standard guide describes aggregates that undergo chemical reactions with hydroxide (OH-) in the poresolution.3.2.4 non-reactive, adjused to describe materials that do not undergo chemi
22、cal reactions that subsequently result in prematuredeterioration of concrete.3.2.4.1 DiscussionSome aggregates with minor amounts of reactive constituents may exhibit the symptoms of alkali-aggregate reaction (AAR)without producing any damage to the concrete; these are termed as non-reactive aggrega
23、tes.4. Summary of Guide4.1 Alkali-aggregate reactions (AAR) occur between the alkali hydroxides in the pore solution of concrete and certaincomponents found in some aggregates. Two types of AAR are recognized depending on the nature of the reactive component:alkali-silica reaction (ASR) nvolves vari
24、ous types of reactive siliceous (SiO2 containing) minerals and alkali-carbonate reaction(ACR) involves certain types of rocks that contain dolomite CaMg(CO3)2. Both types of reaction can result in expansion andcracking of concrete elements when exposed to moisture, leading to a reduction in the serv
25、ice life of concrete structures.4.2 This guide describes approaches for identifying potentially deleteriously reactive aggregates and selecting appropriatepreventive measures to minimize the risk of expansion when such aggregates are used in concrete in exposure environments whereAAR may be of conce
26、rn. Preventive measures include avoiding use of the reactive aggregate, limiting the alkali loading of theconcrete, using supplementary cementitious materials, using lithium-based admixtures, or a combination of these strategies.5. Significance and Use5.1 This guide provides recommendations for iden
27、tifying the potential for deleteriousAAR and selecting appropriate preventivemeasures, based on a prescriptive-based or performance approach, to minimize the risk of deleterious reaction. In regions whereoccurrences ofAAR are rare or the aggregate sources in use have a satisfactory field performance
28、 record verified by following theguidance in this standard, it is reasonable to continue to rely on the previous field history without subjecting the aggregates tolaboratory tests for AAR. In regions where AAR problems have occurred or the reactivity of aggregates is known to vary fromsource to sour
29、ce, it may be necessary to follow a testing program to determine potential reactivity and evaluate preventive3 Available from American Concrete Institute (ACI), P.O. Box 9094, Farmington Hills, MI 48333-9094, http:/www.concrete.org.4 Available from American Association of State Highway and Transport
30、ation Officials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,http:/www.transportation.org.5 Available from Canadian Standards Association (CSA), 5060 Spectrum Way, Suite 100, Mississauga, ON, L4W 5N4, Canada, http:/www.csa.ca.C1778 162measures. In this guide, the level of preven
31、tion required is a function of the reactivity of the aggregate, the nature of the exposureconditions (especially availability of moisture), the criticality of the structure, and the availability of alkali in the concrete.5.2 Risk EvaluationTo use this guide effectively, it is necessary to define the
32、 level of risk that is acceptable, as this willdetermine the type and complexity of testing (Note 1). The risk of deleterious expansion occurring as a result of a failure to detectdeleteriously reactive aggregates can be reduced by routine testing using petrography, or laboratory expansion tests, or
33、 both.NOTE 1The level of risk of alkali-silica reaction will depend upon the nature of the project (criticality of the structure and anticipated exposure). Thedetermination of the level of risk is generally associated with the responsible the responsibility of the individual in charge of the design,
34、 commonly arepresentative of the owner, and for structures designed in accordance with ACI 318, the level of acceptable risk would be determined by the licenseddesign professional.5.3 Preventive For conventional structures, preventive measures determined by either performance testing or the prescrip
35、tiveapproach described in this guide can be expected to generally reduce the risk of expansion as a result ofASR to an acceptable levelfor conventional structures. level. For certain critical structures, such as those exposed to continuous moisture (for example,hydraulic dams or power plants), in wh
36、ichASR-related expansion cannot be tolerated, more conservative mitigation measures maybe warranted.5.4 There are no proven measures for effectively preventing damaging expansion with alkali carbonate reactive rocks inconcrete and such materials need to be avoided by selective quarrying.avoided.5.5
37、If an aggregate is identified as potentially deleteriously reactive as a result ofASR, and the structure size, class, and exposurecondition requires preventive measures, the aggregate may be accepted for use together with appropriate preventive measuresfollowing the prescriptive or performance metho
38、ds outlined in this guide.6. Procedure6.1 The flow chart in Fig. 1 shows the general sequence of testing and decisions that should be made when evaluating a sourceof aggregate for potential AAR. Prior documented satisfactory field performance of the aggregate in concrete is generallyconsidered to be
39、 sufficient for its acceptance in new concrete. However, reliance on prior field performance without following theguidance and recommended testing in 7.1 may not be sufficient to safeguard against damage as a result of AAR in newconstruction. This is due to the difficulties in assuring that the mate
40、rials and mixture proportions used in existing structures built10 to 20 years ago (the time frame needed to ensure that a deleterious reaction as a result of AAR has not occurred) are similarto those being proposed for use today. In most cases, it will be necessary to perform laboratory tests to det
41、ermine whether theaggregate is potentially deleteriously reactive for the specific concrete mixture to be used. There are several test methods availablefor evaluating potential AAR; petrographic examination, determination of chemical constituents, and mortar bar and concreteprism expansion tests are
42、 recommended in this guide. If the aggregate is deemed to be non-reactive, it can be accepted for use inconcrete with no further consideration of mitigation provided that the other physical properties of the aggregate render it suitablefor use (refer to Specification C33/C33M). If the aggregate is a
43、 quarried carbonate, additional tests are required to determinewhether the potential reaction is of the alkali-carbonate or alkali-silica type.6.2 Steps for selecting appropriate preventive measures for ASR follow either a performance-based (Section 8) orprescriptive-based (Section 9) approach. In t
44、he performance-based approach, a potential preventive measure is tested to determineif the measure provides a reduction in expansion below the limits outlined in this guide. Both approaches are intended to minimizethe potential for deleterious expansion in field concrete.7. Determining Aggregate Rea
45、ctivity7.1 Use of Field Performance History:7.1.1 The long-term field performance history of an aggregate can be established by surveying existing structures that wereconstructed using the same aggregate source.As many structures as practical should be included in the survey and these structuresshou
46、ld, if possible, represent different types of construction (for example, foundations, walls, bridges, pavements, sidewalks, andstructural elements). Practice C823/C823M provides useful guidance when surveying structures to establish field performancehistory. The following information should be docum
47、ented for each structure:7.1.1.1 AgeStructures should be at least 15 years old as visible damage from AAR can take more than ten years to develop.7.1.1.2 Cement content and alkali content of the cement used during construction.7.1.1.3 Use and content of pozzolans or slag cement or blended cements du
48、ring construction.7.1.1.4 Exposure ConditionAvailability of moisture and use of deicing chemicals.7.1.1.5 Symptoms of distress as a result of AAR or other causes.observed.7.1.2 Cores should be taken from a representative number of these structures and a petrographic examination conducted usingPracti
49、ce C856 to establish the following (Note 2):7.1.2.1 The aggregate used in the structure surveyed is of similar mineralogical composition, as determined by Guide C295, tothat of the aggregate to be used.7.1.2.2 Any evidence of damage as a result of AAR; andC1778 1637.1.2.3 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 should be taken to establish uniformity of materials.7.1.3 If the results of the field survey indicate that the ag
