ACI 221.1R-1998 Report on Alkali-Aggregate Reactivity《碱活性报告》.pdf

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1、ACI 221.1R-98 became effective August 19, 1998.Copyright 1998, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by anymeans, including the making of copies by any photo process, or by electronic ormechanical device, printed, written, or oral, or

2、 recording for sound or visual reproduc-tion or for use in any knowledge or retrieval system or device, unless permission inwriting is obtained from the copyright proprietors.221.1R-1ACI Committee Reports, Guides, and Commentaries areintended for guidance in planning, designing, executing, andinspec

3、ting construction. This document is intended for the useof individuals who are competent to evaluate the significanceand limitations of its content and recommendations and whowill accept responsibility for the application of the material itcontains. The American Concrete Institute disclaims any anda

4、ll responsibility for the stated principles. The Institute shallnot be liable for any loss or damage arising therefrom.Reference to this document shall not be made in contractdocuments. If items found in this document are desired by theArchitect/Engineer to be a part of the contract documents, theys

5、hall be restated in mandatory language for incorporation bythe Architect/Engineer.Report on Alkali-Aggregate ReactivityACI 221.1R-98(Reapproved 2008)Reported by ACI Committee 221Stephen W. Forster*ChairmanDavid J. Akers Meng K. Lee Aimee Pergalsky*Colin D. Arrand Donald W. Lewis James S. PierceGrego

6、ry S. Barger Dean R. MacDonald Raymond R. PisaneschiRichard L. Boone Kenneth Mackenzie Marc Q. RobertBenoit Fournier Gary R. Mass* James W. Schmitt*Michael S. Hammer Bryant Mather Charles F. Scholer*F. A. Innis Richard C. Meininger* Peter G. SnowJames T. Kennedy Richard E.Miller David C. Stark*Josep

7、h F. Lamond Michael A. Ozol* Michael D. A. ThomasD. Stephen Lane* Steven E. Parker Robert E. Tobin*Member of subcommittee responsible for preparation of this report.Note: Other Task Force members include: Kim Anderson (former Committee member, deceased); Leonard Bell (former committee member);and Co

8、lin Lobo (non-committee member).Information that is currently available on alkali-aggregate reactivity(AAR), including alkali-silica reactivity (ASR) and alkali-carbonate reac-tivity (ACR) is summarized in the report. Chapters are included that pro-vide an overview of the nature of ASR and ACR react

9、ions, means to avoidthe deleterious effects of each reaction, methods of testing for potentialexpansion of aggregates and cement-aggregate combinations, measures toprevent deleterious reactions, and recommendations for evaluation andrepairof existing structures.Keywords: aggregates; alkali-aggregate

10、 reactivity; alkali-carbonate reactiv-ity; alkali-silica reactivity; concrete; concrete distress; concrete durability.CONTENTSChapter 1Introduction, p. 221.1R-21.1Historical perspective1.2Scope of reportChapter 2Manifestations of distress due to alkali-silica reactivity, p. 221.1R-32.1Introduction2.

11、2Cracking mechanisms2.3Expansion and other indicators of alkali-silicareactivity2.4Alkali-silica reactivity reaction factors2.5Microscopic evidence of alkali-silica reactivityChapter 3Alkali-silica reactivity mechanisms,p. 221.1R-63.1Factors influencing the reaction3.2Basic mechanisms of reaction an

12、d expansionChapter 4Petrography of alkali-silica reactive aggregate, p. 221.1R-84.1Introduction4.2Potentially reactive natural siliceous constituents4.3Potentially reactive synthetic materialsChapter 5Measures to prevent alkali-silica reactivity, p. 221.1R-95.1Overview5.2Limiting moisture5.3Aggregat

13、e selection5.4Minimizing alkalies5.5Cement selection221.1R-2 MANUAL OF CONCRETE PRACTICE5.6Finely divided materials other than portland cement5.7Testing for the effectiveness of pozzolans or slags5.8Alkali content of concrete5.9Chemical admixtures5.10Other methodsChapter 6Methods to evaluate potenti

14、al for expansive alkali-silica reactivity, p. 221.1R-146.1Introduction6.2Field service record6.3Common tests to evaluate potential alkali-silica re-activity of aggregates6.4Less common tests to evaluate potential alkali-silicareactivity of aggregates6.5Tests to evaluate alkali-silica reactivity in h

15、ardenedconcrete6.6Summary of testingChapter 7Manifestations of distress due to alkali-carbonate reactivity, p. 221.1R-197.1Overview7.2Field indicators7.3Microscopic indicators7.4Role of environment, structure geometry, and re-straint on distress developmentChapter 8Alkali-carbonate reactivity mechan

16、isms, p. 221.1R-208.1Overview8.2Characteristics of alkali-carbonate reactive rocks8.3Mechanism of reaction and expansionChapter 9Measures to prevent alkali-carbonate reactivity, p. 221.1R-229.1Introduction9.2Aggregate selection9.3Cement9.4Pozzolans9.5MoistureChapter 10Methods to evaluate potential f

17、or expansive alkali-carbonate reactivity, p. 221.1R-2210.1Introduction10.2Field service record10.3Petrographic examination10.4Rock cylinder test10.5Concrete prism tests10.6Other procedures10.7Evaluation of new aggregate sourcesChapter 11Evaluation and repair of structures affected by alkali-aggregat

18、e reactivity, p. 221.1R-2411.1Introduction11.2Evaluation11.3Repair methods and materialsChapter 12References, p. 221.1R-2612.1Referenced standards and reports12.2Cited referencesCHAPTER 1INTRODUCTIONIn many parts of the world, precautions must be taken toavoid excessive expansion due to alkali-aggre

19、gate reactivity(AAR) in many types of concrete construction. AAR mayinvolve siliceous aggregates (alkali-silica reactivity, ASR)or carbonate aggregates (alkali-carbonate reactivity, ACR),and failure to take precautions may result in progressivedeterioration, requiring costly repair and rehabilitatio

20、n ofconcrete structures to maintain their intended function.Extensive knowledge is available regarding the mechanismsof the reactions, the aggregate constituents that may reactdeleteriously, and precautions that can be taken to avoidresulting distress. However, deficiencies still exist in ourknowled

21、ge of both ASR and ACR. This is particularly truewith respect to the applicability of test methods to identifythe potential for reactivity, methods to repair affectedconcrete, and means to control the consequences of thereactions in existing structures.Intensive research has been conducted to develo

22、p thisneeded information. As a result, concrete structures can nowbe designed and built with a high degree of assurance thatexcessive expansion due to AAR will not occur and causeprogressive degradation of the concrete.This report provides information for those involved with thedesign and constructi

23、on of concrete, to make them aware ofthe factors involved in AAR and the means that are availableto control it.1.1Historical perspective1.1.1 Alkali-silica reactivityAlkali-silica reactivity(ASR) was first recognized in concrete pavement in Californiaby Stanton (1940, 1942) of the California State D

24、ivision ofHighways. Stantons early laboratory work demonstratedthat expansion and cracking resulted when certain combina-tions of high-alkali cement and aggregate were combined inmortar bars stored in containers at very high relativehumidity. Two important conclusions were drawn from thiswork: First

25、, expansions resulting from ASR in damp mortarbars were negligible when alkali levels in cement were lessthan 0.60 percent, expressed as equivalent sodium oxide(percent Na2Oe = percent Na2O + 0.658 percent K2O). Asecond conclusion was that the partial replacement of high-alkali cement with a suitabl

26、e pozzolanic material preventedexcessive expansions. Thus, foundations for the engineeringcontrol of the reaction were developed. This work also formedthe basis for ASTM C 227, the mortar-bar test procedure.Based on Stantons work, the U.S. Bureau of Reclamation(Meissner, 1941) conducted investigatio

27、ns of abnormalcracking in concrete dams. Meissners findings generallycorroborated those of Stanton, and lent further credence tothe importance of cement alkali level, aggregate composition,and environmental requirements in the development ofexpansion due to ASR. One outcome of this work was thedevel

28、opment of the quick chemical test, ASTM C 289(Mielenz et al., 1948).In the 1940s, other agencies both in the U.S. and othercountries conducted further studies on ASR. These agenciesincluded the Army Corps of Engineers, the Bureau ofALKALI-AGGREGATE REACTIVITY 221.1R-3Public Roads, and the Portland C

29、ement Association in theU.S., the Australian Council for Scientific and IndustrialResearch (Alderman et al., 1947) and the Danish NationalCommittee for Alkali Aggregate Research. They furtheredthe understanding of relationships among cement composition,aggregate types, mixture proportions of mortar

30、andconcrete, and expansion.Other workers during this period and in the early 1950sconcentrated on clarifying mechanisms expansive and non-expansive reactions. At the Portland Cement Association,Hansen (1944) proposed that osmotic pressures generatedduring swelling of gel reaction products were respo

31、nsible forthe observed expansion. Powers and Steinour (1955)proposed a variant of this hypothesis, while later researchersattempted to refine these ideas of expansion mechanisms. Aswith other aspects of the reaction, gaps still exist, particularly inthe quantitative aspects of reactivity.Mather (199

32、3) reviewed the use of admixtures to preventexcessive expansion due to alkali-silica reaction. Stanton(1940, 1942) reported that 25 percent pumicite, a pozzolan,“seems to be effective” in reducing “the expansion to a negli-gible amount at early periods.” The proposal to use pozzolanto prevent excess

33、ive expansion due to ASR apparently wasfirst advanced by Hanna (1947). The 1963 report of ACICommittee 212 indicated that there had been “a fewinstances” where a mineral admixture was used to provideprotection with high-alkali cement and reactive aggregate. Inspite of this statement, Mather (1993) r

34、eported that he couldfind no documented evidence of such use. However, Rogers(1987) had written, “At the Lower Notch Dam on the Mont-real River, 20 percent fly ash replacement was used success-fully to prevent cracking of concrete containing argillite andgraywacke.” This appears to have been the fir

35、st documentedcase where a pozzolan was used with cement known to havehigh-alkali content and with aggregate known to be poten-tially deleteriously reactive. A similar case was reportedfrom Wales (Blackwell and Pettifer, 1992).Test methods currently in use to determine potential forexpansive reactivi

36、ty, particularly in the United States, deriveprimarily from work carried out in the 1940s. However,research efforts in several countries today indicate a promiseof newer, more reliable tests to identify potentially deleteri-ously reactive cement-aggregate combinations.1.1.2 Alkali-carbonate reactivi

37、tyAlkali-carbonate reac-tivity (ACR) was identified as causing a type of progressivedeterioration of concrete by Swenson (1957) of the NationalResearch Council of Canada. He found that an alkali-sensitivereaction had developed in concrete containing argillaceouscalcitic dolomite aggregate that appea

38、red to be different thanthe alkali-silica reaction. Subsequent work by Swenson(1957), Swenson and Gillott (1960), and Gillott (1963) inCanada, and by various other agencies in Canada and theUnited States, further elucidated factors that affected themagnitude of expansion resulting from the reaction.

39、 Note-worthy among researchers in the United States were Newlonand Sherwood (1962), Newlon et al. (1972a,b), and Hadley(1961, 1964). Two hypotheses on the mechanism of ACRwere developed, both of which still are cited.Because rock susceptible to this type of reaction is rela-tively rare, and is often

40、 unacceptable for use as concreteaggregate for other reasons, reported occurrences of delete-rious ACR in actual structures are relatively few. The onlyarea where it appears to have developed to any great extentis in southern Ontario, Canada, in the vicinities of Kingstonand Cornwall. Isolated occur

41、rences in concrete structureshave been found in the United States in Indiana, Kentucky,Tennessee, and Virginia. So-called “alkali-dolomite reactions”involving dolomitic limestones and dolostones have alsobeen recognized in China (Tang et al., 1996).1.2Scope of reportThis report is intended to provid

42、e information on ASR andACR. Accordingly, chapters in this report provide an overviewof the nature of both ASR and ACR reactions, the means ofavoiding the deleterious effects of each reaction, methods oftesting for potential expansion of cement-aggregate combina-tions, measures to prevent deleteriou

43、s reactions, and recom-mendations for evaluation and repair of existing structures.CHAPTER 2MANIFESTATIONS OF DISTRESS DUE TO ALKALI-SILICA REACTIVITY2.1IntroductionThe most evident manifestations of deleterious ASR in aconcrete structure are concrete cracking, displacement ofstructural members due

44、to internal expansion of the concrete,and popouts. However, these features should not be used asthe only indicators in the diagnosis of ASR in a concretestructure. Cracking in concrete is essentially the result of thepresence of excessive tensile stress within the concrete,which can be caused by ext

45、ernal forces such as load, or bydevelopment of a differential volume change within theconcrete. Early contraction, too large thermal gradientsduring curing of the concrete, corrosion of embedded reinforce-ment, freezing and thawing, and internal and external sulfateattack are some of the mechanisms

46、that also can lead to theformation of cracks in concrete.Diagnosing ASR-related cracking requires the additionalidentification of ASR reaction product in the concrete and,most importantly, requires positive indications that thisproduct has led to the generation of tensile stresses sufficientlylarge

47、that the tensile strength of the concrete was exceeded.2.2Cracking mechanismsLittle is usually known about the time necessary fordevelopment of cracks in ASR-affected concrete in thefield. This is partly due to the heterogeneous nature ofconcrete as a material, and to the fact that the reactionkinet

48、ics of ASR are practically unexplored. For example:1. Does the reaction product swell at the place it forms, orat a different place where it migrates after formation?2. How rapidly are expansive pressures generated from theswelling reaction product?3. How do these mechanisms produce cracks in the co

49、ncrete?However, some inferences can be made based onobserving ASR-affected concrete in the field and in thelaboratory. For example, in an unreinforced and unconfinedconcrete element, such as a concrete slab or beam, the largest221.1R-4 MANUAL OF CONCRETE PRACTICEdegree of deformation of the concrete will occur in thedirection of least restraint.Fig. 1 is a sketch of the surface and a cross section of aconcrete slab undergoing ASR. Swelling due to the uptake ofwater by alkali-silica reaction product generates tensile