《ACI-224.3R-1995-R2001.pdf》由会员分享,可在线阅读,更多相关《ACI-224.3R-1995-R2001.pdf(44页珍藏版)》请在三一文库上搜索。
1、AC1 224.3R-95 (Reapproved 2001) Joints in Concrete Construction Reported by AC1 Committee 224 Grant T. Hahorsen*+ Chairman Peter Barlow Florian G. Barth Alfred G. Bishara* Randall W. Postonst Secretary David W. Fowler Peter Gergely Will Hansen Harry M. Palmbaum Keith A. Pashina* Andrew Scanlon Howar
2、d L. Boggs M. Nadim Hassoun Emest K. Schrader* Merle E. Brander David Fouad H. Fouad* William Lee Tony C. Liu* Edward G. Nawyt Wimal Suaris Lewis H. Tuthiil* Zenon A. Zielinski * Principal author. In addition to the above, committee associate member Michael J. Pfeiffer, consulting member LeRoy A. Lu
3、tz, past member Amfinn Rusten, and nonmember Guy S. Puccio (Chairman, Committee 504) were princi- pal authors; Committee 325 member Michael I. Darter was a contributing author. Editorial subcommittee. This report reviews the state of the art in design, construction, and mainte- nance ofjoints in con
4、crete structures subjected to a wide variety of use and environmental conditions. In some cases, the option of eliminating joints is considered. Aspects of various joint sealant materials and jointing tech- niques are discussed. The reader is referred to ACI 504R for a more com- prehensive treatment
5、 o f sealant materials, and to AC1 224R for a broad discussion of the causes and control of cracking in concrete construction, Chapters in the report focus on various types of structures and structural elements with unique characteristics: buildings, bridges, slabs-on-grade, tunnel linings, canal li
6、nings, precast concrete pipe, liquid-retaining struc- fures, walls, and mass concrete. Keywords: bridges, buildings, canals, canal linings, concrete construc- tion, construction joints, contraction joints, design, environmental engi- neering concrete structures, isolation joints, joints, parking lot
7、s, pavements, runways, slabs-on-grade, tunnels, tunnel linings, walls. CONTENTS Chapter 1-Introduction, p. 224.3R-2 1. I-Joints in concrete structures 1.2-Joint terminology 1.3-Movement in concrete structures 1.4-Objectives and scope AC1 Committee Reports, Guides, Standard Practices, and Commentarie
8、s are intended for guidance in planning, designing, executing, and inspecting construction. This document is intended for the use of individuais who are competent to evaluate the significance and limitations of its con- tent and recommendations and who will accept responsibility for the application
9、of the material it contains. The American Concrete Institute disclaims any and ali responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom. Reference to this document shall not be made in contract documents. If items found in this document
10、 are desired by the ArchitecEngineer to be a part of the contract documents, they shall be restated in mandatory lan- guage for incorporation by the ArchitectEngineer. Chapter Wealant materials and jointing techniques, p. 224.3R-4 2.1-Introduction 2.2-Required properties of joint sealants 2.3-Commer
11、cially available materials 2.4-Field-molded sealants 2.5-Accessory materials 2.6-Preformed sealants 2.7-Compression seals 2.8-Jointing practice Chapter 3-Buildings, p. 224.3R-8 3.1-Introduction 3.2-Construction joints 3.3-Contraction joints 3.4-Isolation or expansion joints Chapter char- acteristics
12、 of the structure; nature of restraint on an individ- ual member; and the type and magnitude of environmental and service loads on the member. 1.2-Joint terminology The lack of consistent terminology for joints has caused problems and misunderstandings that plague the construc- tion world. In 1979 t
13、he American Concrete Institute Techni- cal Activities Committee (TAC) adopted a consistent terminology on joints for use in reviewing AC1 documents: Joints will be designated by a terminology based on the following characteristics: resistance, configuration, formation, location, type o f structure,
14、and function. Characteristics in each category include, but are not limit- Resistance: Tied or reinforced, doweled, nondoweled, Configuration: Butt, lap, tongue, and groove. Formation: Sawed, hand-formed, tooled, grooved, insert- Location: Transverse, longitudinal, vertical, horizontal. Type of Stru
15、cture: Bridge, pavement, slab-on-grade building. Function: Construction, contraction, expansion, isolation, hinge. Example: Tied, tongue and groove, hand-tooled, longitu- dinal pavement construction joint. The familiar term, “control joint,” is not included in this list of joint terminology, since i
16、t does not have a unique and universal meaning. Many people involved with construction have used the term to indicate a joint provided to “control” cracking due to volume change effects, especially shrinkage. However, improperly detailed and constructed “control” joints may not function properly, an
17、d the concrete can crack adjacent to the presumed joint. In many cases a “control joint” is really nothing more than rustication. These joints are really trying to control cracking due to shrinkage and thermal contraction. A properly detailed contraction joint is needed. An additional problem with j
18、oint nomenclature concerns “isolation” and “expansion” joints. An isolation joint isolates the movement between members. That is, there is no steel or dowels crossing the joint. An expansion joint, by compari- son, is usually doweled such that movement can be accom- modated in one direction, but the
19、re is shear transfer in the other directions. Many people describe structural joints with- out any restraint as expansion joints. ed to the following: plain. formed. 1.3-Movement and restraint in concrete structures Restrained movement is a major cause of cracking in con- crete structures. Internal
20、or external restraint can develop tensile stresses in a concrete member, and the tensile strength or strain capacity can be exceeded. Restrained movement of concrete structures includes the effects of settlement: com- patibility of deflections and rotations where members meet, and volume changes. Vo
21、lume changes typically result from shrinkage as hard- ened concrete dries, and from expansion or contraction due to temperature changes. A detailed discussion of volume change mechanisms is be- yond the scope of this report. Evaluate specific cases to de- termine the individual contributions of temp
22、erature change and loss of moisture to the environment. The potential vol- ume change is considered in terms of the restraint that results from geometry, as well as reinforcement. 1.3.1 Shrinkage volume changes-While many types of shrinkage are important and may cause cracking in concrete structures
23、, drying shrinkage of hardened concrete is of spe- cial concern. Drying shrinkage is a complicated function of parameters related to the nature of the cement paste, plain concrete, member, or structural geometry and environment. For example, building slabs shrink about 500 x lo4, yet shrinkage of an
24、 exposed slab on grade may be less than 100 x lo4. A portion of drying shrinkage also may be re- versible. A large number of empirical equations have been proposed to predict shrinkage. AC1 209R provides informa- tion on predicting shrinkage of concrete structures. If shrink- age-compensating concre
25、te is used, it is necessary for the structural element to expand against elastic restraint from in- ternal reinforcement before it dries and shrinks (AC1 224R). 1.3.2 Expansion volume changes-Where a shrinkage- compensating concrete is used, additional consideration of the expansion that will occur
26、during the early life of the con- crete is necessary. Unless a shrinkage-compensating con- crete is allowed to expand, its effectiveness in compensating for shrinkage will be reduced. 1.3.3 Thermal volume changes-The effects of thermal volume changes can be important during construction and in servi
27、ce as the concrete responds to temperature changes. Two important factors to consider are the nature of the tem- perature change and the fundamental material properties of concrete. The coefficient of thermal expansion for plain concrete a describes the ability of a material to expand or contract as
28、 temperatures change. For concrete, a depends on the mix- ture proportions and the type of aggregate used. Aggregate properties dominate the behavior, and the coefficient of lin- ear expansion can be predicted. Mindess and Young (1981) discuss the variation of the expansion coefficient in further de
29、tail. Ideally, the coefficient of thermal expansion could be computed for the concrete in a particular structure. This is seldom done unless justified by unusual material properties or a structure of special significance. For concrete, the coef- ficient of thermal expansion a can be reasonably assum
30、ed to be 6 x 10-VF (1 1 x 10-W). During construction, the heat generated by hydrating port- land cement may raise the temperature of a concrete mass higher than will be experienced in service. Contraction of the concrete as the temperature decreases while the material is relatively weak may lead to
31、cracking. AC1 224R, AC1 Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/05/2007 01:49:31 MSTNo reproduction or networking permitted without license from IHS -,-,- 224.3R-4 MANUAL OF CONCRETE PRAC
32、TICE 207.1R, and AC1 207.2R discuss control of cracking for or- dinary and mass concrete due to temperature effects during construction. In service, thermal effects are related to long-term and nearly instantaneous temperature differentials. Long-term shrinkage has the same sense as the effect of te
33、mperature drops, so overall contraction is likely to be the most signifi- cant volume change effect for many structures. For some components in a structure, the longer term ef- fects are related to the difference of hottest summer and low- est winter temperature. The structure also may respond to th
34、e difference between temperature extremes and a typical tem- perature during construction. In most cases the larger tem- perature difference is most important. Daily variations in temperature are important, too. Distor- tions will occur from night to day, or as sunlight heats por- tions of the struc
35、ture differently. These distortions may be very complicated, introducing length changes, as well as cur- vatures into portions of the structure. An example is the ef- fect of “sun camber” in parking structures where the roof deck surface becomes as much as 20 to 40 F (10 to 20 C) hot- ter than the s
36、upporting girder. This effect causes shears and moments in continuous framing. 1.4-Objectives and scope This report reviews joint practices in concrete structures subjected to a wide variety of uses and environmental condi- tions. Design, construction, and maintenance of joints are discussed, and in
37、 some cases, the option of eliminating joints is considered. Chapter 2 summarizes aspects of various seal- ant materials and jointing techniques. However, the reader is referred to AC1 504R for a more comprehensive treatment. Chapters 3-10 focus on various types of structures and struc- tural elemen
38、ts with unique characteristics: buildings, bridg- es, slabs-on-grade, tunnel linings, canal linings, precast concrete pipe, liquid-retaining structures, walls, and mass concrete. Many readers of this report will not be interested in all types of construction discussed in Chapters 3-10. These readers
39、 may wish to first study Chapter 2, then focus on a specific type of structure. While not all types of concrete construction are addressed specifically in this report, the Committee feels that this broad selection of types of structures can provide guidance in other cases as well. Additional structu
40、ral forms may be addressed in future versions of this report. AC1 22413 provides additional detailed discussion of both the causes of cracking and control of cracking through de- sign and construction practice. CHAPTER support it against sagging, indentation, and displacement by traffic or fluid pre
41、ssure; and simplify tooling. They may also serve as a bond breaker to prevent the sealant from bonding to the back of the joint. The backup material should preferably be compressible so that the sealant is not forced out as the joint closes, and it should recover as the joint opens. Care is re- quir
42、ed to select the correct width and shape of material, so that after installation it is compressed to about 50 percent of its onginal width. Stretching, twisting, or braiding of tube or rod stock should be avoided. Backup materials and fillers containing bitumen or volatile materials should not be us
43、ed with thermosetting chemical curing field-molded sealants. They may migrate to, or be absorbed at joint interfaces, and impair adhesion. In selecting a backup material to ensure compatibility, it is advisable to follow the recommendations of the sealant manufacturer. Preformed backup materials are
44、 used for supporting and controlling the depth of field-molded sealants. 2.6-Preformed sealants Traditionally, preformed sealants have been subdivided into two classes; rigid and flexible. Most rigid preformed sealants are metallic; examples are metal water stops and flashings. Flexible sealants are
45、 usually made from natural or synthetic rubbers, polyvinyl chloride, and like materials, and are used for waterstops, gaskets, and miscellaneous sealing purposes. Preformed equivalents of certain materials, e.g., rubber asphalts, usually categorized as field molded, are available as a convenience in
46、 handling and installation. Compression seals should be included with the flexible group of preformed sealants. However, their function is dif- ferent. The compartmentalized neoprene type can be used in most joint sealant applications as an alternative to field- molded sealants. They are treated sep
47、arately in this report. 2.6.1 Rigid waterstops and miscellaneous seals-Rigid waterstops are made of steel, copper, and occasionally of lead. Steel waterstops are primarily used in dams and other heavy construction projects. Ordinary steel may require ad- ditional protection against corrosion. Stainl
48、ess steels are used in dam construction to overcome corrosion problems. Steel waterstops are low in carbon and stabilized with columbium or titanium to simplify welding and retain corro- sion resistance after welding. Annealing is required for im- proved flexibility, but the stiffness of steel water
49、stops may lead to cracking in the adjacent concrete. Copper waterstops are used in dams and general construc- tion; they are highly resistant to corrosion, but require care- ful handling to avoid damage. For this reason, in addition to considerations of higher cost, flexible waterstops are often used instead. Copper is also used for flashings. At one time lead was used for waterstops, flashings, or protection in industrial floor joints. Its use is now very limit- ed. Bronze strips find wide application in dividing, rather than sealing, terrazzo and o
链接地址:https://www.31doc.com/p-3728774.html