1、 ACI 207.4R-05(Reapproved 2012)Cooling and Insulating Systemsfor Mass ConcreteReported by ACI Committee 207Cooling and Insulating Systemsfor Mass ConcreteFirst printingOctober 2005ISBN 0-087031-191-3Copyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This materia
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9、ough electronicsubscription, or reprint and may be obtained by contacting ACI.Most ACI standards and committee reports are gathered together in the annually revised ACI Manual ofConcrete Practice (MCP).American Concrete Institute38800 Country Club DriveFarmington Hills, MI 48331U.S.A.Phone: 248-848-
10、3700Fax: 248-848-3701www.concrete.orgACI 207.4R-05 supersedes 207.4R-93 (Reapproved 1998) and became effectiveAugust 15, 2005.Copyright 2005, 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 pho
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12、mentariesare intended for guidance in planning, designing, executing,and inspecting construction. This document is intended for theuse of individuals who are competent to evaluate thesignificance and limitations of its content and recommendationsand who will accept responsibility for the application
13、 of thematerial it contains. The American Concrete Institute disclaimsany and all responsibility for the stated principles. The Instituteshall not 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
14、 desired by theArchitect/Engineer to be a part of the contract documents, theyshall be restated in mandatory language for incorporation bythe Architect/Engineer.Cooling and Insulating Systemsfor Mass ConcreteReported by ACI Committee 207ACI 207.4R-05(Reappoved 2012)The need to control volume change
15、induced primarily by temperaturechange in mass concrete often requires cooling and insulating systems.This report reviews precooling, postcooling, and insulating systems. A sim-plified method for computing the temperature of freshly mixed concretecooled by various systems is also presented.Keywords:
16、 cement content; coarse aggregate; creep; formwork; heat ofhydration; mass concrete; modulus of elasticity; precooling; postcooling;pozzolan; restraint; specific heat; strain; stress; temperature rise; tensilestrength; thermal conductivity; thermal diffusivity; thermal expansion; thermalgradient; th
17、ermal shock.CONTENTSChapter 1Introduction, p. 21.1Scope and objective1.2Historical background1.3Types of structures and temperature controls1.4Construction practices for temperature control1.5InstrumentationChapter 2Precooling systems, p. 32.1General2.2Heat exchange2.3Batch water2.4Aggregate cooling
18、2.5Cementitious materials2.6Heat gains during concreting operations2.7Refrigeration plant capacity2.8Placement areaChapter 3Postcooling systems, p. 93.1General3.2Embedded pipe3.3Refrigeration and pumping facilities3.4Operational flow control3.5Surface coolingChapter 4Surface insulation, p. 114.1Gene
19、ral4.2Materials4.3Horizontal surfaces4.4Formed surfaces4.5Edges and corners4.6Heat absorption from light energy penetration4.7Geographical requirementsChapter 5References, p. 145.1Referenced standards and reports5.2Cited referencesStephen B. TatroChairJeffrey C. Allen Robert W. Cannon Barry D. Fehl
20、Gary R. MassTerrence E. Arnold Teck L. Chua Rodney E. Holderbaum Tibor J. PatakyRandall P. Bass Eric J. Ditchey Allen J. Hulshizer Ernest K. SchraderJ. Floyd Best Timothy P. Dolen David E. Kiefer Gary P. WilsonAnthony A. Bombich2 COOLING AND INSULATING SYSTEMS FOR MASS CONCRETE (ACI 207.4R-05)Americ
21、an Concrete Institute Copyrighted Materialwww.concrete.orgCHAPTER 1INTRODUCTION1.1Scope and objectiveThe need to control volume change induced primarily bytemperature change in mass concrete often requires coolingand insulating systems. This report discusses three constructionprocedures used to cont
22、rol temperature changes in concretestructures: precooling of materials, postcooling of in-placeconcrete by embedded pipes, and surface insulation. Otherdesign and construction practices, such as selection ofcementing materials, aggregates, chemical admixtures,cement content, or strength requirements
23、, are not within thescope of this report.The objective of this report is to offer guidance on theselection and application of these procedures for reducingthermal cracking in all types of concrete structures.1.2Historical backgroundMajor developments in cooling and insulating systems forconcrete beg
24、an with postcooling systems for dams. Latergains were made in developing precooling methods. The useof natural cooling methods has increased with the use ofbetter analytical methods to compute thermal performance.Similarly, insulating systems expanded beyond just coldweather protection and into cont
25、rol of thermal gradientsduring other weather conditions.The first major use of postcooling of in-place massconcrete was in the construction of the Bureau of Reclama-tions Hoover Dam in the early 1930s. The primary objectivewas to accelerate thermal contraction of the concrete mono-liths within the d
26、am so that the contraction joints could befilled with grout to ensure monolithic action of the dam.Cooling was achieved by circulating cold water through pipesembedded in the concrete. Circulation of water was usuallystarted several weeks or more after the concrete had beenplaced. Since the construc
27、tion of Hoover Dam, the same basicsystem of postcooling has been used in the construction ofmany large dams and other massive structures, such as power-houses, except that circulation of cooling water is now typicallyinitiated immediately after placing the concrete.In the early 1940s, the Tennessee
28、Valley Authority usedpostcooling in the construction of Fontana Dam for twopurposes: to control the temperature rise, particularly in thevulnerable base of the dam where cracking of the concretecould be induced by the restraining effect of the foundation;and to accelerate thermal contraction of the
29、columns so thatthe contraction joints between columns could be filled withgrout to ensure monolithic action. Postcooling was startedcoincidently with the placing of each lift of concrete. Thepipe spacing and lift thickness were varied to limit themaximum temperature to a predesigned level in all sea
30、sons.In summer, with naturally high (unregulated) placingtemperatures, the pipe spacing and lift thickness for thecritical foundation zone was 2.5 ft (0.76 m); in winter, whenplacing temperatures were naturally low, the pipe spacingand lift thickness for this zone was 5.0 ft (1.5 m). Above thecritic
31、al zone, the lift thickness was increased to 5.0 ft (1.5 m),and the pipe spacing was increased to 6.25 ft (1.9 m).Cooling was also started in this latter zone coincidently withthe placing of concrete in each new lift.In the 1960s, the Corps of Engineers began the practice ofstarting, stopping, and r
32、estarting the cooling process basedon temperatures measured with embedded resistancethermometers. At Dworshak Dam and at the Ice HarborAdditional Power House Units, the cooling water wasstopped when the temperature of the concrete near the pipesbegan to drop rapidly after reaching a peak. Within 1 t
33、o 3 dayslater, when the temperature would rise again to the previouspeak temperature, cooling would be started again to producecontrolled, safe cooling.Generally, arch dams were constructed with postcoolingsystems to expedite the volume change of the mass concretefor joint grouting. The first roller
34、-compacted concrete (RCC)arch dam was Knellpoort Dam in South Africa, completed in1988. Due to the height and rapid construction of RCC archdams, design engineers paid close attention to the heat-of-hydration issues due to their effect on the final stress state ofthe dam. In China, several arch dams
35、 have been completed,including Shapai Dam near Chengdu, China, which was theworlds highest until 2004. At Shapai Dam, and others since,cooling pipes were embedded between some of the RCC liftsto circulate cool liquid to control the maximum internaltemperature of the RCC. Testing showed that high-den
36、sitypolyethylene cooling pipes worked quite well with RCC. Thecontrols and operation procedures for the RCC arch damswere the same as used in conventional concrete dams in thepast. By late 2003, 14 RCC arch dams had been completed orwere under construction, mainly in China and South Africa.The first
37、 reported use of precooling concrete materials toreduce the maximum temperature of mass concrete was by theCorps of Engineers during the construction of Norfork Damfrom 1941 to 1945. A portion of the batch water was intro-duced into the mixture as crushed ice. Placement temperatureof the concrete wa
38、s reduced by approximately 10F (6C).The concrete was cooled as a result of the thermal energy (heatof fusion) required to convert ice to water and from thelowered temperature of the water after melting. Since then,precooling has become very common for mass concreteplacements. It also is used for pla
39、cements of relatively smalldimensions, such as for bridge piers and foundations wherethere is sufficient concern for minimizing thermal stresses.Injection of cold nitrogen gas into the mixer has been usedto precool concrete in recent years. Practical and economicalconsiderations should be evaluated,
40、 but it can be effective.As with ice, additional mixing time may be required. Minoramounts of concrete cooling have been achieved by injectingit at transfer points on conveyor delivery systems, in gobhoppers, and in the mixing chamber. Nitrogens maininefficiency is losing gas to the atmosphere if th
41、e mixer ortransfer is not well enclosed.Various combinations of crushed ice, cold batch water,liquid nitrogen, and cooled aggregate are used to lowerplacement temperature to 50F (10C) and, when necessary,to as low as 40F (4.5C).RCC projects have effectively used “natural” precoolingof aggregate duri
42、ng production. Large quantities of aggregateCOOLING AND INSULATING SYSTEMS FOR MASS CONCRETE (ACI 207.4R-05) 3American Concrete Institute Copyrighted Materialwww.concrete.orgproduced during cold winter months or during cold nighttimetemperatures and stockpiled in naturally cold conditions canremain
43、cold at the interior of the pile well into the warmsummer months. At Middle Fork, Monksville, and Stage-coach Dams, it was not unusual to find frost in the stockpilesduring production of RCC in the summer at ambienttemperatures about 75 to 95F (24 to 35C). Ice wasobserved in southern New Mexicos Gri
44、ndstoneCanyons coarse aggregate stockpile as late as June. Precooling and postcooling have been used in combination inthe construction of massive structures such as Glen CanyonDam, completed in 1963; Dworshak Dam, completed in1975; and the Lower Granite Dam Powerhouse addition,completed in 1978.Insu
45、lation has been used on lift surfaces and concrete facesto prevent or minimize the potential for cracking undersudden drops in ambient temperatures. This method ofminimizing cracking by controlling rapid cooling of thesurface has been used since 1950. It has become an effectivepractice where needed.
46、 The first extensive use of insulationwas during the construction of Table Rock Dam, built during1955 to 1957. More recent examples of mass concreteinsulation include the Lock Schrader 1987).1.4Construction practices for temperature controlPractices that have evolved to control temperatures andconse
47、quently minimize thermal stress and cracking are listedbelow. Some of these require minimal effort, while othersrequire substantial initial expense:Cooling batch water;Producing aggregate during cold seasons or coolnights;Replacing a portion of the batch water with ice;Shading aggregates in storage;
48、Shading aggregate conveyors;Spraying aggregate stockpiles for evaporative cooling;Immersion in cool water or saturation of coarse aggregates,including wet belt cooling;Vacuum evaporation of moisture in coarse aggregate;Nitrogen injection into the mixture and at transferpoints during delivery;Using l
49、ight-colored mixing and hauling equipment, andspraying the mixing, conveying, and delivery equipmentwith a water mist;Scheduling placements when ambient temperatures arelower, such as at night or during cooler times of the year;Cooling cure water and the evaporative cooling ofcure water;Postcooling with embedded cooling pipes;Controlling surface cooling of the concrete withinsulation;Avoiding thermal shock during form and insulationremoval;Protecting exposed edges and corners from excessiveheat loss;Cooling aggregates with natural or manufac
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