1、Guide to Cold Weather ConcretingReported by ACI Committee 306ACI 306R-16First PrintingSeptember 2016ISBN: 978-1-945487-15-6Guide to Cold Weather ConcretingCopyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This material may not be reproduced or copied, in whole
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11、Institute38800 Country Club DriveFarmington Hills, MI 48331Phone: +1.248.848.3700Fax: +1.248.848.3701www.concrete.orgThis document guides specifiers, contractors, and concrete producers through the selection processes that identify methods for cold weather concreting. The objectives of cold weather
12、concreting practices are to: a) prevent damage to concrete due to freezing at early ages; b) ensure that the concrete develops the recommended strength for safe removal of forms; c) maintain curing conditions that foster normal strength development; d) limit rapid tempera-ture changes; and e) provid
13、e protection consistent with intended serviceability of the structure. Concrete placed during cold weather will develop sufficient strength and durability to satisfy intended service requirements when it is properly proportioned, produced, placed, and protected.Keywords: accelerating admixtures; ant
14、ifreeze admixtures; cold weather concreting; concrete temperature; curing; enclosures; form removal; freezing and thawing; heaters; heating aggregates; insulating materials; maturity testing; protection; strength development.CONTENTSCHAPTER 1INTRODUCTION AND SCOPE, p. 21.1Introduction, p. 21.2Scope,
15、 p. 2CHAPTER 2NOTATION AND DEFINITIONS, p. 22.1Notation, p. 22.2Definitions, p. 3CHAPTER 3OBJECTIVES, PRINCIPLES, AND ECONOMY, p. 33.1Objectives, p. 33.2Principles, p. 33.3Economy, p. 4CHAPTER 4GENERAL RECOMMENDATIONS, p. 44.1Planning, p. 44.2Protection during unexpected freezing, p. 44.3Concrete te
16、mperature, p. 44.4Temperature records, p. 44.5Heated enclosures, p. 54.6Slab finishing, p. 54.7Concrete workability, p. 5CHAPTER 5TEMPERATURE OF CONCRETE AS MIXED AND PLACED, AND HEATING OF MATERIALS, p. 55.1Placement temperature, p. 55.2Mixing temperature, p. 65.3Heating mixing water, p. 65.4Heatin
17、g aggregates, p. 65.5Steam heating of aggregates, p. 7William J. Lyons III, Chair Kevin A. MacDonald, Vice Chair Erik Holck, SecretaryACI 306R-16Guide to Cold Weather ConcretingReported by ACI Committee 306Kim D. BashamJames R. Baty IIMichael Patrick BerryCharles D. BinkowskiKen CannellaTerry C. Col
18、linsD. Gene DanielDavid J. ElmerMario GarzaJohn P. GnaedingerRobert J. HoopesKenneth C. HoverEric D. KingRonald L. Kozikowski Jr.Steve R. Lloyd Sr.Michael J. MarcheseStephen C. MorricalCraig M. NewtsonWilliam D. Palmer Jr.Dennis R. PurintonDomenick Thomas RutturaValery TokarConsulting MembersTerry L
19、. LavyRobert J. RyanHarold B. WenzelSixin YangVictor I. SubkovACI Committee Reports, Guides, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. This document is intended for the use of individuals who are competent to evaluate the significance
20、and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. The American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising ther
21、efrom.Reference to this document shall not be made in contract documents. If items found in this document are desired by the Architect/Engineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer.ACI 306R-16 supersedes ACI
22、306R-10 and was adopted and published September 2016.Copyright 2016, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by electronic or mechanical device, printed, written, or
23、oral, or recording for sound or visual reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.15.6Overheating of aggregates, p. 75.7Calculation of mixture temperature, p. 75.8Temperature loss during delivery, p.
24、 7CHAPTER 6PREPARATION BEFORE CONCRETING, p. 86.1Preparation of surfaces in contact with fresh concrete, p. 86.2Massive metallic embedments, p. 86.3Subgrade condition, p. 8CHAPTER 7PROTECTION AGAINST FREEZING FOR CONCRETE NOT REQUIRING CONSTRUCTION SUPPORTS, p. 87.1Protection methods, p. 87.2Protect
25、ion period, p. 97.3Protection period for durability, p. 97.4Protection for strength gain, p. 97.5Temperature drop after removal of protection, p. 97.6Allowable temperature differential during stripping, p. 10CHAPTER 8PROTECTION AGAINST FREEZING FOR STRUCTURAL CONCRETE REQUIRING CONSTRUCTION SUPPORTS
26、, p. 108.1Introduction, p. 108.2Field-cured cylinders, p. 108.3In-place testing, p. 108.4Maturity testing, p. 108.5Attainment of design strength, p. 128.6Increasing early strength, p. 128.7Cooling concrete, p. 138.8Estimating strength development, p. 138.9Removal of forms and supports, p. 138.10Esti
27、mating strength development: modeling cold weather placements, p. 14CHAPTER 9EQUIPMENT, MATERIALS, AND METHODS OF TEMPERATURE PROTECTION, p. 149.1Introduction, p. 149.2Insulating materials, p. 149.3Selection of insulation when supplementary heat is not used, p. 149.4Selection of insulation for use w
28、ith hydronic heaters, p. 199.5Heaters, p. 199.6Enclosures, p. 199.7Internal heating, p. 209.8Temperature monitoring, p. 209.9Temporary removal of protection, p. 209.10Insulated forms, p. 20CHAPTER 10CURING RECOMMENDATIONS AND METHODS, p. 2010.1Introduction, p. 2010.2Curing during the protection peri
29、od inside an enclosure, p. 2010.3Curing following the protection period, p. 21CHAPTER 11ACCELERATION OF SETTING AND STRENGTH DEVELOPMENT, p. 2111.1Introduction, p. 2111.2Accelerating admixtures, p. 2111.3Cold weather admixture systems (CWASs), p. 2211.4Rapid setting cements, p. 22CHAPTER 12REFERENCE
30、S, p. 22Authored documents, p. 23CHAPTER 1INTRODUCTION AND SCOPE1.1IntroductionThe conditions of cold weather concreting exist when the air temperature has fallen to, or is expected to fall below, 40F (4C) during the protection period. The protection period is defined as the amount of time recommend
31、ed to prevent concrete from being adversely affected by exposure to cold weather during construction. Concrete placed during cold weather will develop sufficient strength and durability to satisfy the intended service recommendations when it is properly proportioned, produced, placed, and protected.
32、 The necessary degree of protection increases as the ambient temperature decreases.Take advantage of the opportunity provided by cold weather to place low-temperature concrete. Concrete placed during cold weather, protected against freezing, and prop-erly cured for a sufficient length of time, has t
33、he potential to develop higher ultimate strength (Klieger 1958) and greater durability than concrete placed at higher temperatures. It is susceptible to less thermal cracking than similar concrete placed at higher temperatures.Refer to ACI 306.1 for cold weather concreting require-ments in a specifi
34、cation format. The Mandatory Items Checklist in ACI 306.1 can be used to add appropriate modi-fications to the contract documents.This document guides the specifier, contractor, and concrete producer through the recommendations that iden-tify methods for cold weather concreting.1.2ScopeThis guide di
35、scusses general recommendations, concrete temperature during mixing and placing, temperature loss during delivery, preparation for cold weather concreting, protection requirements for concrete with or without construction supports, estimating strength development, methods of protection, curing recom
36、mendations, and admix-tures for accelerating setting and strength gain including antifreeze admixtures.The materials, processes, quality-control measures, and inspections described in this document should be tested, monitored, or performed as applicable only by individuals holding the appropriate AC
37、I Certifications or equivalent.CHAPTER 2NOTATION AND DEFINITIONS2.1NotationM = maturity factor, deg-hAmerican Concrete Institute Copyrighted Material www.concrete.org2 GUIDE TO COLD WEATHER CONCRETING (ACI 306R-16)ta= ambient air temperature, F (C)tr= concrete temperature upon delivery to the jobsit
38、e, F (C)T = concrete temperature, F (C)Ta= coarse aggregate temperature, F (C)Tc= cement temperature, F (C)Td= drop in temperature to be expected during a 1-hour delivery time, F (C). (This value should be added to trto determine the recommended temperature of concrete at the plant after batching.)T
39、o= datum temperature, F (C)Ts= fine aggregate temperature, F (C)Tw= temperature of added mixing water, F (C)Wa= saturated surface-dry weight of coarse aggregate, lb (kg)Wc= weight of cement lb (kg)Ws= saturated surface-dry weight of fine aggregate, lb (kg)Ww= weight of mixing water, lb (kg)Wwa= weig
40、ht of free water on coarse aggregate, lb (kg)Wws= weight of free water on fine aggregate, lb (kg)t = duration of curing period at concrete temperature T, deg-h2.2DefinitionsACI provides a comprehensive list of definitions through an online resource, “ACI Concrete Terminology,” https:/www.concrete.or
41、g/store/productdetail.aspx?ItemID=CT16. Definitions provided herein complement that resource.carbon monoxidea colorless and odorless gas in the exhaust of fossil-fuel heaters and internal combustion engines that can cause dusting of concrete surfaces that are less than 24 hours of age.cold weatherwh
42、en air temperature has fallen to, or is expected to fall below, 40F (4C) during the protec-tion period; protection period is defined as the time recom-mended to prevent concrete from being adversely affected by exposure to cold weather during construction.freezingthe development of solid water ice w
43、ithin the paste that disrupts the paste, causing frost lenses to develop in the paste.hydronic heatermobile energy-exchanging system used to heat frozen ground, formwork, or concrete surfaces by pumping heated fluid through closed-circulation tubing and a heat exchanger.liquidus temperaturethe minim
44、um temperature at which all components of a solution can be in a liquid state. Below the liquidus temperature the mixture will be partly or entirely solid.maturity testingtests performed to estimate in-place concrete strength using in-place concrete temperature history and strength-versus-temperatur
45、e history functions derived from tests of concrete with comparable mixture proportions.protectionthe materials and environmental conditions in place to prevent concrete from being affected by exposure to cold weather.CHAPTER 3OBJECTIVES, PRINCIPLES, AND ECONOMY3.1ObjectivesThe objectives of cold wea
46、ther concreting practices are to:(a) Prevent damage to concrete due to early-age freezing. When no external water is available, the degree of saturation of newly placed concrete decreases as the concrete matures and the mixing water combines with cement during hydra-tion. Additionally, mixing water
47、is lost to evaporation even at cold temperatures. Under such conditions, the degree of saturation falls below the critical saturation. Critical satura-tion is the level at which a single cycle of freezing can cause damage. The degree of saturation falls below critical satura-tion at the approximate
48、time the concrete attains a compres-sive strength of 500 psi (3.5 MPa) (Powers 1962). At 50F (10C), most well-proportioned concrete mixtures reach this strength within 48 hours. The temperature of concrete is measured in accordance with ASTM C1064/C1064M.(b) Ensure that the concrete develops the req
49、uired strength for safe removal of forms, shores, and reshores, and for safe loading of the structure during and after construction.(c) Maintain curing conditions that promote strength devel-opment without exceeding the recommended concrete temper-atures in Table 5.1 by more than 20F (7C) and without using water curing, which may cause critical saturation at the end of the protection period, thus reducing resistance to freezing and thawing when protection is removed (5.1).
