ACI 304 6R-2009 Guide for Use of Volumetric-Measuring and Continuous-Mixing Concrete Equipment《容积计量和混凝土连续搅拌设备的使用指南》.pdf

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1、ACI 304.6R-09Reported by ACI Committee 304Guide for Use of Volumetric-Measuringand Continuous-MixingConcrete EquipmentGuide for Use of Volumetric-Measuring andContinuous-Mixing Concrete EquipmentFirst PrintingMarch 2009ISBN 978-0-87031-321-9American Concrete InstituteAdvancing concrete knowledgeCopy

2、right by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This materialmay not be reproduced or copied, in whole or part, in any printed, mechanical, electronic, film, or otherdistribution and storage media, without the written consent of ACI.The technical committees respo

3、nsible for ACI committee reports and standards strive to avoid ambiguities,omissions, and errors in these documents. In spite of these efforts, the users of ACI documents occasionallyfind information or requirements that may be subject to more than one interpretation or may beincomplete or incorrect

4、. Users who have suggestions for the improvement of ACI documents arerequested to contact ACI. Proper use of this document includes periodically checking for errata atwww.concrete.org/committees/errata.asp for the most up-to-date revisions.ACI committee documents are intended for the use of individu

5、als who are competent to evaluate thesignificance and limitations of its content and recommendations and who will accept responsibility for theapplication of the material it contains. Individuals who use this publication in any way assume all risk andaccept total responsibility for the application a

6、nd use of this information.All information in this publication is provided “as is” without warranty of any kind, either express or implied,including but not limited to, the implied warranties of merchantability, fitness for a particular purpose ornon-infringement.ACI and its members disclaim liabili

7、ty for damages of any kind, including any special, indirect, incidental,or consequential damages, including without limitation, lost revenues or lost profits, which may resultfrom the use of this publication.It is the responsibility of the user of this document to establish health and safety practic

8、es appropriate tothe specific circumstances involved with its use. ACI does not make any representations with regard tohealth and safety issues and the use of this document. The user must determine the applicability of allregulatory limitations before applying the document and must comply with all a

9、pplicable laws and regulations,including but not limited to, United States Occupational Safety and Health Administration (OSHA) healthand safety standards.Order information: ACI documents are available in print, by download, on CD-ROM, through electronicsubscription, or reprint and may be obtained b

10、y 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: 248-848-3700Fax: 248-848-3701www.concrete.orgACI 304.6R-09 supersedes

11、 ACI 304.6R-91 and was adopted and published March 2009.Copyright 2009, 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

12、 oral, or recording for sound or visual reproductionor for use in any knowledge or retrieval system or device, unless permission in writingis obtained from the copyright proprietors.304.6R-1ACI Committee Reports, Guides, Manuals, StandardPractices, and Commentaries are intended for guidance inplanni

13、ng, designing, executing, and inspecting construction.This document is intended for the use of individuals who arecompetent to evaluate the significance and limitations of itscontent and recommendations and who will acceptresponsibility for the application of the material it contains.The American Co

14、ncrete Institute disclaims any and allresponsibility for the stated principles. The Institute shall notbe 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 pa

15、rt of the contract documents, theyshall be restated in mandatory language for incorporation bythe Architect/Engineer.Guide for Use of Volumetric-Measuring andContinuous-Mixing Concrete EquipmentReported by ACI Committee 304ACI 304.6R-09This guide includes a short history of and information on the ba

16、sic designand operation of equipment, frequently called mobile mixers, used toproduce concrete by volumetric measurement and continuous mixing(VMCM). Definitions, applications, and quality assurance testing arediscussed. The use of this equipment is compared with weigh-batch-mixingequipment to highl

17、ight some of the limited differences.Keywords: batcher; continuous mixer; flowing (self-consolidating)concrete; fresh concrete; grout; high-early-strength concrete; latex; mixer;no-fines (pervious) concrete; overlay; precast concrete; shotcrete.CONTENTSChapter 1Introduction and scope, p. 304.6R-21.1

18、Introduction1.2Scope1.3HistoryChapter 2Definitions, p. 304.6R-2Chapter 3Equipment, p. 304.6R-23.1Materials storage and measurement3.2Mixers3.3Equipment conditionChapter 4Operations, p. 304.6R-34.1General4.2Production rates4.3Planning4.4Materials4.5Personnel qualificationsHakim S. Abdelgader Daniel J

19、. Green Gary R. Mass Royce J. RhoadsDavid J. Akers John V. Gruber Larry W. Matejcek James M. Shilstone Jr.Casimir Bognacki Neil R. Guptill Avi A. Mor Boris Y. SteinFrederic Chapdelaine Terence C. Holland Soubhi Naddaf William X. SypherJ. Mitchell Englestead Tarek S. Khan Dipak T. Parekh Samuel X. Ya

20、oMichael R. Gardner Larry G. Lepper*James S. Pierce*Subcommittee Chair.David A. BurgChair304.6R-2 ACI COMMITTEE REPORTChapter 5Applications, p. 304.6R-45.1General5.2Mixtures with short working times5.3Low-slump mixtures5.4Latex-modified overlays5.5Long unloading times5.6Concrete at remote sites5.7Ma

21、king small deliveries5.8Precast operations5.9Hot weather concreting5.10Mining applications5.11Grouting and pile filling5.12Colored concretes5.13Emergency applications5.14Controlled low-strength fill5.15Fiber-reinforced concrete5.16Military applicationsChapter 6Quality control and testing, p. 304.6R-

22、76.1General6.2Calibration6.3Production testingChapter 7Operational precautions, p. 304.6R-97.1General7.2Cold weather concrete7.3Hot weather concrete7.4Aggregate moisture7.5Rapid slump loss due to false set7.6Use of admixtures7.7Freshly mixed concrete propertiesChapter 8References, p. 304.6R-98.1Refe

23、renced standards and reportsAppendix ASample calibration procedure/forms, p. 304.6R-11CHAPTER 1INTRODUCTION AND SCOPE1.1IntroductionThis document offers guidance on volumetric-measurementand continuous-mixing (VMCM) concrete production. Theoriginal and most common use of VMCM equipment is asmobile (

24、either truck- or trailer-mounted) equipment.Because of its compact size, ability to produce mixedconcrete, and versatility, a significant number of stationaryunits have been produced. This configuration provides afree-standing base and is typically powered by electricalcircuits normally found in a p

25、recast plant or other industrialfacility. Unless specifically noted, the information in thisdocument applies to all VMCM equipment.1.2ScopeThis guide contains background information to be consideredwhen using the VMCM method. A discussion of other typesof continuous-measurement equipment (conveyor b

26、elt scalesor weigh-in-motion scales) is outside the scope of this report.1.3HistoryVolumetric measurement and continuous mixing have along history in the production of concrete. For many years,the concept of “one shovel of cement, two shovels of sand,and three shovels of stone” was used to produce c

27、oncrete.Patents on continuous mixers date back at least to 1913. Itwas not until volumetric measurement and continuousmixing were successfully combined in the early 1960s thatgeneral field use of this type of equipment began. The firstcommercial unit was delivered in 1964. Because of the detailof or

28、iginal patents, there was only one manufacturer of VMCMunits until the early 1980s, when other manufacturers beganto offer this type of equipment for concrete production.By the mid-1970s, there were over 4000 VMCM machinesin operation in the United States that were generally used toproduce small vol

29、umes of concrete. During the late 1970sand early 1980s, specialty concretes needed for bridge-deckrenovation and highway repair, which were difficult toproduce in conventional transit mixers, were producedsuccessfully with VMCM equipment. This application gavethe equipment credence by proving that i

30、t could consistentlyproduce close-tolerance, high-quality concrete. VMCMequipment was previously thought to be limited to producingspecial mixtures or small volumes; however, VMCM may besuitable for almost any concrete requirement.Standards activities related to concrete produced byVMCM equipment ha

31、ve been increasing as the field unitsincrease. In 1971, ASTM developed C685, and now maintainsASTM C685/C685M. The American Association of StateHighway and Transportation Officials covers VMCMequipment in M 241. In 1993, ACI published ACI 548.4,“Standard Specification for Latex Modified Concrete (LM

32、C)Overlays,” which lists mobile mixers as the equipment usedto produce this product, and designates ASTM C685/C685Mas the standard by which these units are defined. In 1999, agroup of VMCM equipment manufacturers approached theNational Ready Mixed Concrete Association (NRMCA) forassistance in formin

33、g the Volumetric Mixer ManufacturerBureau (VMMB). The VMMB was formed, and in 2001published VMMB 100-01, which defines the volume ofingredients needed to produce a cubic yard of concrete, andreferences ASTM C685/C685M uniformity requirements asthe measure of accuracy in this type of equipment.CHAPTE

34、R 2DEFINITIONSmeasuring, volumetricdispensing an ingredient basedon volume, either in discrete quantities or by continuous flow.mixing, continuousproducing concrete by continuouslyblending ingredients in fixed proportions. The discharge ofthe concrete mixture may be started or stopped as required.CH

35、APTER 3EQUIPMENT3.1Materials storage and measurementMeasurement of material by volume can be accomplishedby a variety of means. Rotary vane feeders (both horizontaland vertical axis), screw conveyors (both adjustable andfixed speed), drag chains, calibrated gate openings, variable-volume sliding com

36、partments, and vibrating plate feedersVOLUMETRIC-MEASURING AND CONTINUOUS-MIXING CONCRETE EQUIPMENT 304.6R-3have been used to measure quantities of dry ingredients.Liquids can be introduced by air pressure, pumps, or cylinders,with the flow controlled by valves or timers and measured byflow meters.

37、Whichever methods of material metering areused, they should be consistent to ensure the production of aproper mixture. Documents produced by the equipmentmanufacturers should be referenced for operating details ofthe various types of equipment. Cement, water, and admixturesare stored in separate con

38、tainers and are measured separately.Fine and coarse aggregates are stored either separately orcombined. If aggregates are stored and used in a combinedstate, they should be accurately preblended, and particularcare should be taken to avoid segregation.A meter or other indicator on the equipment reco

39、rds theamount and the rate of introduction of cement into themixture, and this rate serves, directly or indirectly, to controlthe rate at which other ingredients are added. All systems areinterconnected so that once they are calibrated and set toproduce a specific concrete mixture, all ingredients a

40、resimultaneously and continuously measured into the mixer.This interconnecting allows either continuous or intermittentoperation of the system to accommodate the quantities of theconcrete needed. These interconnections should not beconfused with the interlocks typically found in weigh-typebatch plan

41、ts. VMCM equipment is designed to allow therelative proportions of ingredients to be changed rapidly tovary the concrete mixture as required. Because the mixingchamber only holds approximately 4 ft3(0.10 m3), suchchanges can be made with little or no waste. Typical VMCMunits carry enough materials t

42、o produce 6 to 10 yd3(4.5 to 8 m3)of concrete (Fig. 3.1). This limitation is based on axleloading limitations. Production of larger volumes of concreteor high rates of production will require provisions forrecharging the material storage compartments.3.2MixersMost continuous mixers use an auger rota

43、ted in a slopedtrough or tube. Materials are introduced at or near the lowerend, and the mixed concrete is discharged at the other. Thisbasic principle is the same for all VMCM equipment,although there are many individual variations. Augers areavailable in different lengths and diameters, can operat

44、e atdifferent speeds, and can have continuous or interruptedflights. Troughs may have flexible or rigid bottoms andcovered or open tops. The slope of the mixer may be fixed oradjustable. Lowering the trough (which is normally set atabout a 15-degree inclination) may reduce the mixing time,while rais

45、ing the trough may extend it. Mixing time can beadjusted by modifying the mixer angle of inclination, mixerrpm, mixer flighting configuration, throughput rate, or acombination of these. Actual mixing time from input tooutput is usually less than 20 seconds. Mixing times as longas 45 seconds have bee

46、n achieved, but this comes at aconsiderable reduction in production throughput.With this type of mixer, output is always equal to input,with a relatively small amount of material being mixed atany one time. Thorough mixing is accomplished in a veryshort time by applying high-shear, high-energy mixin

47、g to thematerial. A pivot at the base of most mixers allows them toswing from side to side.3.3Equipment conditionAll proportioning and mixing equipment should be wellmaintained in accordance with the manufacturers instructions.This point cannot be overemphasized. Equipment conditiondirectly impacts

48、the quality of the finished product.Attention should be paid to the following areas:The cement dispenser should be clean and free of anybuildup;Valves should operate smoothly and not leak;Any accumulation of materials on any controllingsurface or opening in the system will alter the calibratedflow o

49、f materials;Mixer augers should not be allowed to wear beyond themanufacturers recommended limits;There should be no buildup of concrete on the mixerauger surfaces;Delivery mechanisms should be properly adjusted andkept in good repair;There should be no leaks in the hydraulic or air systems;There should be no cut or damaged insulation onelectrical wires; andAll covers and guards should be securely in place.ASTM C685/C685M provides guidance for evaluatingmixer uniformity.CHAPTER 4OPERATIONS4.1GeneralVolumetric measurement and cont