ACI 306R-2010 Guide to Cold Weather Concreting.pdf

1、ACI 306R-10Reported by ACI Committee 306Guide to Cold Weather ConcretingGuide to Cold Weather ConcretingFirst PrintingOctober 2010ISBN 978-0-87031-397-4American Concrete InstituteAdvancing concrete knowledgeCopyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This

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10、nually revised ACI Manual ofConcrete Practice (MCP).American Concrete Institute38800 Country Club DriveFarmington Hills, MI 48331U.S.A.Phone: 248-848-3700Fax: 248-848-3701www.concrete.orgACI 306R-10 supersedes ACI 306R-88 and was adopted and published October 2010.Copyright 2010, American Concrete I

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13、ompetent to evaluate thesignificance and limitations of its content and recommendationsand who will accept responsibility for the application of thematerial it contains. The American Concrete Institute disclaimsany and all responsibility for the stated principles. The Instituteshall not be liable fo

14、r 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, theyshall be restated in mandatory language for incorporation bythe Architect/Enginee

15、r.Guide to Cold Weather ConcretingReported by ACI Committee 306ACI 306R-10The objectives of cold weather concreting practices are to prevent damage toconcrete due to freezing at early ages, ensure that the concrete develops therequired strength for safe removal of forms, maintain curing conditions t

16、hatfoster normal strength development, limit rapid temperature changes, andprovide protection consistent with the intended serviceability of the structure.Concrete placed during cold weather will develop sufficient strength anddurability to satisfy intended service requirements when it is properlypr

17、oduced, placed, and protected. This guide provides information for thecontractor to select the best methods to satisfy the minimum cold weatherconcreting requirements.This guide discusses: concrete temperature during mixing and placing,temperature loss during delivery, preparation for cold weather c

18、oncreting,protection requirements for concrete that does not require constructionsupports, estimating strength development, methods of protection, curingrequirements, and admixtures for accelerating setting and strength gainincluding antifreeze admixtures.The materials, processes, quality control me

19、asures, and inspectionsdescribed in this document should be tested, monitored, or performed asapplicable only by individuals holding the appropriate ACI Certificationsor equivalent.Keywords: accelerating admixtures; antifreeze admixtures; cold weatherconcreting; concrete temperature; curing; enclosu

20、res; form removal;freezing and thawing; heaters; heating aggregates; insulating materials;maturity testing; protection; strength development.CONTENTSChapter 1Introduction, p. 2Chapter 2Notation and definitions, p. 22.1Notation2.2DefinitionsChapter 3Objectives, principles, and economy, p. 33.1Objecti

21、ves3.2Principles3.3EconomyChapter 4General requirements, p. 44.1Planning4.2Protection during unexpected freezing4.3Concrete temperature4.4Temperature records4.5Heated enclosures4.6Finishing air-entrained slabs4.7Concrete workabilityChapter 5Temperature of concrete as mixed and placed, and heating of

22、 materials, p. 55.1Placement temperature5.2Mixing temperature5.3Heating mixing water5.4Heating aggregates5.5Steam heating of aggregates5.6Overheating of aggregates5.7Calculation of mixture temperature5.8Temperature loss during deliveryKim D. Basham John P. Gnaedinger Timothy J. Lickel Richard W. Mel

23、nechukJames R. Baty II Robert J. Hoopes Darmawan Ludirdja Craig M. NewtsonTerry C. Collins Kenneth C. Hover William J. Lyons III William D. Palmer Jr.D. Gene Daniel Eric D. King Zhongguo John Ma Valery TokarDavid J. ElmerThe committee would like to acknowledge Charles Binkowski, Mario Garza, and Eri

24、c Holck for their contributions to the document.Stephen C. MorricalChairKevin A. MacDonaldVice Chair2 GUIDE TO COLD WEATHER CONCRETING (ACI 306R-10)American Concrete Institute Copyrighted Materialwww.concrete.orgChapter 6Preparation before concreting, p. 76.1Preparation of surfaces in contact with f

25、resh concrete6.2Massive metallic embedments6.3Subgrade conditionChapter 7Protection against freezing and protection for concrete not requiring construction supports, p. 87.1Protection methods7.2Protection period7.3Protection for strength gain7.4Temperature drop after removal of protection7.5Allowabl

26、e temperature differential during strippingChapter 8Protection for structural concrete requiring construction supports, p. 98.1Introduction8.2Field-cured cylinders8.3In-place testing8.4Maturity testing8.5Attainment of design strength8.6Increasing early strength8.7Cooling of concrete8.8Estimating str

27、ength development8.9Removal of forms and supports8.10Specification recommendations8.11Estimating strength developmentmodeling ofcold weather placementsChapter 9Equipment, materials, and methods of temperature protection, p. 149.1Introduction9.2Insulating materials9.3Selection of insulation when supp

28、lementary heat isnot used9.4Selection of insulation for use with hydronic heaters9.5Heaters9.6Enclosures9.7Internal heating9.8Temperature monitoring9.9Temporary removal of protection9.10Insulated formsChapter 10Curing requirements and methods,p. 2110.1Introduction10.2Curing during the protection per

29、iod10.3Curing following the protection periodChapter 11Acceleration of setting and strength development, p. 2111.1Introduction11.2Accelerating admixtures11.3Rapid-setting cementsChapter 12References, p. 2412.1Referenced standards and reports12.2Cited referencesCHAPTER 1INTRODUCTIONCold weather exist

30、s when the air temperature has fallen to,or is expected to fall below 40F (4C) during the protectionperiod. The protection period is defined as the time requiredto prevent concrete from being affected by exposure to coldweather. Concrete placed during cold weather will developsufficient strength and

31、 durability to satisfy the intendedservice requirements when it is properly produced, placed,and protected. The necessary degree of protection increasesas the ambient temperature decreases.If requirements for cold weather concreting are needed inspecification form, reference ACI 306.1. If necessary,

32、 addappropriate modifications to the contract documents afterconsulting the specification checklist.This guide provides the necessary information for thecontractor to select the best methods to satisfy the minimumcold weather concreting requirements.CHAPTER 2NOTATION AND DEFINITIONS2.1NotationM = ma

33、turity factor, degree-hourT = temperature of concrete, F (C)Ta= temperature of coarse aggregate, F (C)Tc= temperature of cement, F (C)Td= temperature drop to be expected during a 1-hourdelivery time, F (C). (This value should beadded to trto determine the required temperatureof concrete at the plant

34、.)To= datum temperature, F (C)Ts= temperature of fine aggregate, F (C)Tw= temperature of added mixing water, F (C)ta= ambient air temperature, F (C)tr= concrete temperature required at the job, F (C)Wa= saturated surface-dry weight of coarse aggregate,lb (kg)Wc= weight of cement lb (kg)Ws= saturated

35、 surface-dry weight of fine aggregate, lb (kg)Ww= weight of mixing water, lb (kg)Wwa= weight of free water on coarse aggregate, lb (kg)Wws= weight of free water on fine aggregate, lb (kg)w/cm = water-cementitious material ratiot = duration of curing period at temperature T,degree-hour2.2DefinitionsA

36、CI provides a comprehensive list of definitions throughan online resource, “ACI Concrete Terminology,” http:/terminology.concrete.org. Definitions provided hereincomplement that resource.admixturea material other than water, aggregates,cementitious materials, and fiber reinforcement, used as aningre

37、dient of a cementitious mixture to modify its freshlymixed, setting, or hardened properties and that is added tothe batch before or during its mixing.backshoresshores placed snugly under a concrete slabor structural member after the original formwork and shoreshave been removed from a small area wit

38、hout allowing theGUIDE TO COLD WEATHER CONCRETING (ACI 306R-10) 3American Concrete Institute Copyrighted Materialwww.concrete.orgentire slab or member to deflect or support its own mass orexisting construction loads.carbon monoxidea molecular gas at STP (standardtemperature and pressure) consisting

39、of one atom of carbonand one of oxygen, often the product of burning organicmaterials in a low-oxygen environment.carbonationthe reaction between carbon dioxide and ahydroxide or oxide to form a carbonate, especially in cementpaste, mortar, or concrete; the reaction with calciumcompounds to produce

40、calcium carbonate.cold weatherwhen air temperature has fallen to, or isexpected to fall below, 40F (4C) during the protection period;protection period is defined as the time required to preventconcrete from being affected by exposure to cold weather.concrete, lightweightconcrete having a density ofa

41、pproximately 90 to 115 lb/ft3 (1440 to 1840 kg/m3), usuallyachieved by using lightweight coarse aggregate, lightweightfine aggregate, or both.concrete, normalweightconcrete having a density ofapproximately 150 lb/ft3(2400 kg/m3), made with normal-density aggregates.corrosiondestruction of metal by a

42、 chemical, electro-chemical, or electrolytic reaction within its environment.crack, plastic-shrinkagesurface crack that occurs inconcrete prior to initial set.hydronic heatermobile energy-exchanging systemused to heat frozen ground, formwork, or concrete surfacesby pumping heated fluid through close

43、d-circulation tubingand a heat exchanger.maturity testingtests performed to estimate in-placeconcrete strength using in-place concrete temperature historyand strength versus temperature history functions derivedfrom tests of concrete with comparable mixture proportions.post-tensioningmethod of prest

44、ressing in whichprestressing steel is tensioned after concrete has hardened.protectionthe materials and environmental conditionsin place to prevent concrete from being affected by exposureto cold weather.reaction, alkali-aggregatea generally deleterious dissolu-tion and swelling of components in agg

45、regates in the presenceof pore solutions comprising alkali hydroxides; the reactionproducts may cause expansion and cracking of concrete.reshorea temporary support placed against the bottomof a slab or other structural member immediately after theforms and original shores have been removed.saturatio

46、nas applied to aggregate or concrete: the condi-tion such that no more liquid can be held or placed within it.shorea temporary support for formwork, fresh concrete,and construction loads or for recently built structures thathave not developed full design strength; also called prop,tom, post, and str

47、ut.strength, concrete compressivethe measured maximumresistance of a concrete specimen to axial compressiveloading; expressed as force per unit cross-sectional area.temperaturea measure of the average kinetic energy of theparticles in a sample of matter, expressed in terms of units ordegrees designa

48、ted on a standard scale. The temperature ofconcrete is measured in accordance with ASTM C1064/C1064M.CHAPTER 3OBJECTIVES,PRINCIPLES, AND ECONOMY3.1ObjectivesThe objectives of cold weather concreting practices are asfollows:3.1.1 Prevent damage to concrete due to early age freezing.When no external w

49、ater is available, the degree of saturationof newly placed concrete decreases as the concrete maturesand the mixing water combines with cement during hydration.Under such conditions, the degree of saturation falls below thecritical level (the degree of water saturation where a singlecycle of freezing causes damage) at the approximate time theconcrete attains a compressive strength of 500 psi (3.5 MPa)(Powers 1962). At 50F (10C), most well-proportionedconcrete mixtures r