1、ACI Education Bulletin E4-12Chemical Admixtures for Concrete Developed by ACI Committee E-701First PrintingJanuary 2013Chemical Admixtures for ConcreteCopyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This material may not be reproduced or copied, in whole or p
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10、ACI documents are available in print, by download, on CD-ROM, through electronic subscription, or reprint and may be obtained by contacting ACI.Most ACI standards and committee reports are gathered together in the annually revised ACI Manual of Concrete Practice (MCP).American Concrete Institute3880
11、0 Country Club DriveFarmington Hills, MI 48331U.S.A.Phone: 248-848-3700Fax: 248-848-3701www.concrete.orgAmerican Concrete InstituteAdvancing concrete knowledgeACI Education Bulletin E4-12CHEMICAL ADMIXTURES FOR CONCRETEPrepared under the direction and supervision of ACI Committee E-701 Materials for
12、 Concrete ConstructionThomas M. Greene ChairCorina-Maria AldeaRichard P. BohanDavid A. BurgDarrell F. ElliotDarmawan LudirdjaMark R. LukkarilaClifford N. MacDonaldCharles K. NmaiDavid M. SuchorskiLawrence L. SutterJoseph E. ThomasPaul J. TikalskyKari L. Yuers*Robert C. Zellers*Chair of document subc
13、ommittee.The committee would like to thank Jeff Bowman, Kryton International, for his assistance in preparing this document.This document discusses commonly used chemical admixtures for concrete and describes the basic use of these admixtures. It is targeted at those in the concrete industry not inv
14、olved in determining the specific mixture proportions of concrete or in measuring the properties of the concrete. Students, craftsmen, inspectors, and contractors may find this a valuable introduction to a complex topic. The document is not intended to be a state-of-the-art report, users guide, or a
15、 technical discussion of past and present research findings. More detailed information is available in ACI Committee Report 212.3R, “Chemical Admixtures for Concrete” and 212.4R, “Guide for the Use of High-Range Water-Reducing Admixtures (Superplasticizers) in Concrete.”CONTENTSChapter 1Introduction
16、1.1History1.2Definitions and glossaryChapter 2Overview2.1Function2.2Effectiveness and compatibility2.2StandardsChapter 3Air-entraining admixtures3.1History3.2Mechanism3.3Use of air-entraining admixtures3.4Properties of entrained air3.5Handling and testing of air-entrained concreteChapter 4Water-redu
17、cing and set-controlling admixtures4.1Types and composition4.2Type A, water-reducing admixtures4.3Type B, retarding, and Type D, water-reducing and retarding admixtures4.4Type C, accelerating, and Type E, water-reducing and accelerating admixtures4.5High-range, water-reducing admixtures4.6Mid-range,
18、 water-reducing admixtures4.7Admixtures for self-consolidating concrete4.8Admixtures for slump and workability retentionChapter 5 Specialty admixtures5.1Corrosion-inhibiting admixtures5.2Shrinkage-reducing admixtures5.3Admixtures for controlling alkali-silica reactivity5.4Admixtures for underwater c
19、oncrete5.5Admixtures for cold weather5.6Permeability reducing admixturesChapter 6Admixture dispensers6.1Industry requirements and dispensing methods6.2Accuracy requirements6.3Application considerations and compatibility6.4Field and truck mounted dispensers6.5Dispenser maintenanceChapter 7ConclusionC
20、hapter 8References8.1Cited references8.2List of relevant ASTM standards1The Institute is not responsible for the statements oropinions expressed in its publications. Institute publicationsare not able to, nor intended to, supplant individualtraining, responsibility, or judgement of the user, or thes
21、upplier, of the information presented.ACI Education Bulletin E4-12. Supersedes E4-03. Adopted in 2012 and published in 2013.Copyright 2013, 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 phot
22、o process, or by electronic or mechanical device, printed, written, or oral, or recording for sound or visual repro-duction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.CHAPTER 1INTRODUCTION1.1HistoryAdmixtures hav
23、e long been recognized as important components of concrete used to improve its performance. The original use of admixtures in cementitious mixtures is not well documented. It is believed that the introduction of some of these materials may have been part of rituals or other ceremonies. It is known t
24、hat cement mixed with organic matter was applied as a surface coat for water resistance or tinting purposes. Materials used in early concrete and masonry included milk and lard by the Romans; eggs during the middle ages in Europe; polished glutinous rice paste, lacquer, tung oil, blackstrap molasses
25、, and extracts from elm soaked in water and boiled bananas by the Chinese; and in Mesoamerica and Peru, cactus juice and latex from rubber plants. The purpose of these materials is widely unknown. It is known that the Mayans used bark extracts and other substances as set retarders to keep stucco wor
26、kable for a long period of time. More recently chemical admixtures have been used to help concrete producers meet sustainability requirements that are necessary for modern construction. For concrete these requirements can be related to extended life cycles, use of recycled materials, stormwater mana
27、gement, and reduced energy usage. Chemical admixtures are used to facilitate the increased use of supplementary cementitious materials, lower permeability, and improve the long term durability of concrete.1.2Definitions typically between 0.0004 and 0.04 in. (10 and 1000 mm) in diameter and spherical
28、 or nearly so.Air, entrappedAir voids in concrete that are not purposely entrained and that are larger, mainly irregular in shape, and less useful than those of entrained air; and 1 mm or larger in size.Air contentThe volume of air voids in cement paste, mortar, or concrete, exclusive of pore space
29、in aggregate particles, usually expressed as a percentage of total volume of the paste, mortar, or concrete.AlkaliSalts of alkali metals, principally sodium and potassium; specifically sodium and potassium occurring in constituents of concrete and mortar, usually expressed in chemical analysis as th
30、e oxides Na2O and K2O.Alkali-aggregate reactionChemical reaction in either mortar or concrete between alkalies (sodium and potassium) from portland cement or other sources and certain constituents of some aggregates; under certain conditions, deleterious expansion of concrete or mortar may result.Al
31、kali-carbonate reactionThe reaction between the alkalies (sodium and potassium) in portland cement and certain carbonate rocks, particularly calcitic dolomite American Concrete Institute Copyrighted Materialwww.concrete.orgE4-2 ACI EDUCATION BULLETIN and dolomitic limestones, present in some aggrega
32、tes; the products of the reaction may cause abnormal expansion and cracking of concrete in service.Alkali-silica reactionA generally deleterious dissolution and swelling of siliceous aggregates in the presence of pore solutions comprised of alkali hydroxides; the reaction products may cause abnormal
33、 expansion and cracking of concrete.Calcium chlorideA crystalline solid, CaCl2; in various technical grades, used as a drying agent, as an accelerator for fresh concrete, a deicing chemical, and for other purposes.Cement, portlandA hydraulic cement produced by pulverizing clinker formed by heating a
34、 mixture, usually of limestone and clay, to 1400 to 1600C (2550 to 2900F). Calcium sulfate is usually ground with the clinker to control set.CementitiousHaving cementing properties.Sulfate attackEither a chemical or physical reaction or both between sulfates usually in soil or groundwater and concre
35、te or mortar; the chemical reaction is primarily with calcium aluminate hydrates in the cement-paste matrix, often causing deterioration.Sulfate resistanceAbility of concrete or mortar to withstand sulfate attack.CHAPTER 2OVERVIEW2.1FunctionChemical admixtures discussed in this document are availabl
36、e in liquid and powder form. Liquid admixtures are dispensed through mechanical dispensers as the concrete is batched, but can be introduced to the concrete by other means, such as hand dosing or truck mounted dispensers. Powders are usually introduced in pre-packaged units that contain a prescribed
37、 amount. Most times the units consist of bags that can be opened and the contents added while mixing, or bags that are made to disintegrate and disperse their contents while mixing. Generally, admixtures in powdered form are introduced to the concrete after batching. A discussion of dispensing equip
38、ment for liquid admixtures is given in Chapter 6. The dosages used vary widely depending on several factors including, type of admixture, performance desired, environmental conditions, and many others. The uses of admixtures are outlined by the following functions that they perform: Increase workabi
39、lity without increasing water content or decrease the water content at the same workability; Retard or accelerate initial time of setting; Reduce or prevent shrinkage or create slight expansion; Modify the rate or capacity for bleeding; Reduce segregation; Improve pumpability; Reduce rate of slump l
40、oss; Retard or reduce heat evolution during early hardening; Accelerate the rate of strength development at early ages; Increase strength (compressive, tensile, or flexural); Increase durability or resistance to severe conditions of exposure, including application of deicing salts and other chemical
41、s; Decrease permeability of concrete; Control expansion caused by the reaction of alkalis with reactive aggregate constituents; Increase bond of concrete to steel reinforcement; Increase bond between existing and new concrete; Improve impact and abrasion resistance; Inhibit corrosion of embedded met
42、al; Produce colored concrete or mortar; and Aid in achieving sustainability requirements.2.2Effectiveness and CompatibilityThe effectiveness of any admixture will vary depending on its concentration in the concrete and the effect of the various other constituents of the concrete mixture. Each class
43、of admixture is defined by its primary function. It may have one or more secondary functions, however, and its use may affect, positively or negatively, concrete properties other than those desired. Therefore, adequate testing should be performed to determine the effects of an admixture on the plast
44、ic properties of concrete such as slump, rate of slump loss (that is the relationship between slump and time), air content, and setting time. In addition, testing should be performed to determine the effect of the admixture on the hardened properties of concrete that may be of interest, for example,
45、 strength development, drying shrinkage, modulus of elasticity, or permeability. The final decision as to the use of any admixture and the brand, class, or type, depends on its ability to meet or enhance specific concrete performance needs.Many improvements can be achieved by proper selection and ap
46、plication of specific admixtures. The selection process should focus on the functional qualities required by structural demands, architectural requirements, and contractor needs.Whatever the approach, be it a single water-reducing admixture or a combination approach, the use of admixtures can be ben
47、eficial. Admixtures provide additional means of controlling the quality of concrete by modifying some of its properties, however, they cannot correct for poor-quality materials, improper proportioning of the concrete, and inappropriate placement procedures.It is quite common for a concrete mixture t
48、o contain more than one admixture. In the simplest cases, such as paving or residential applications, a concrete mixture may be dosed with only a water-reducing admixture and an air-entraining admixture. High-performance concrete mixtures may be dosed with as many as five admixtures, depending on th
49、e specific application. Therefore, it is imperative that the admixtures that are used in a given concrete mixture are compatible to prevent undesired effects such as rapid slump loss, air-entrainment difficulties, severe set retardation, or improper strength development.A typical rule of thumb is for all admixtures to be added separately to a concrete mixture and not pre-blended before introduction into the mixture. In addition, admixture manufacturers typically provide information on potential American Concrete
