ACI CCS-0-2016 Concrete Fundamentals.pdf

1、Concrete Craftsman SeriesConcrete Fundamentals CCS-0(16)Concrete Craftsman SeriesConcrete FundamentalsCCS-0 Concrete Fundamentals was originally written by ACI Committee E703, Concrete Construction Practices. The 2016 edition of CCS-0 was reviewed and approved by an Education Task Group including: W

2、illiam Nash, William Palmer, Michael Pedraza, David Suchorski, and Scott Tarr. Thank you to the Task Group members for their thoughtful and thorough review of the fundamental material.CCS-0(16)Concrete Craftsman Series:CCS-0 Concrete FundamentalsISBN 978-1-942727-63-7Copyright 2016 American Concrete

3、 InstituteACI 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 and limitations of its content and recommenda-tions

4、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 therefrom.Reference to this document shall not be made

5、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 incorpora-tion by the Architect/Engineer.Managing Editor: Katie A. Amelio, P.E.Art Program: Claire HiltzEngineering Ed

6、itors: Michael Tholen, Ph.D., P.E. Jerzy Zemajtis, Ph. D., P.E.Professional Development Specialist: Tiffany VojnovskiTechnical Editors: Emily Bush, Cherrie FergussonManager, Publishing Services: Barry M. BerginProduction Editors: Carl Bischof, Kelli Slayden, Kaitlyn Hinman, Tiesha ElamPage Design th

7、e pattern of craze cracks existing in a surface. Curing action taken to maintain moisture and tempera-ture conditions in a freshly placed cementitious mixture to allow hydraulic cement hydration and, if applicable, pozzo-Fig. 0.2Example of concrete surface blistering (photo courtesy of Portland Ceme

8、nt Association (PCA)10 CONCRETE FUNDAMENTALSlanic reactions to occur so that the potential properties of the mixture may develop.Dropchute a device used to confine or direct the flow of a falling stream of fresh concrete. (1) articulated drop-chute a device consisting of a succession of tapered meta

9、l cylinders so designed that the lower end of each cylinder fits into the upper end of the one below; (2) flex-ible dropchute a device consisting of a heavy rubber-ized canvas or plastic collapsible tube.Dusting development of a powdered material at the surface of hardened concrete.Final setting a d

10、egree of stiffening of a cementitious mixture greater than initial setting, generally stated as an empirical value indicating the time required for the cementi-tious mixture to stiffen sufficiently to resist, to an established degree, the penetration of a weighted test device. (See also initial sett

11、ing.)Fine aggregate (1) aggregate passing the 3/8 in. (9.5 mm) sieve, almost entirely passing the No. 4 (4.75 mm) sieve, and predominantly retained on the No. 200 (75 mm) sieve; (2) that portion of aggregate passing the No. 4 (4.75 mm) sieve and predominantly retained on the No. 200 (75 mm) sieve. (

12、See also aggregate.)Fig. 0.3Coarse aggregates (photo courtesy of CTLGroup)VOCABULARY 11Fineness modulus a factor obtained by adding the total percentages of material in the sample that are coarser than each of the following sieves (cumulative percent-ages retained), and dividing the sum by 100: No.

13、100 (150 mm), No. 50 (300 mm), No. 30 (600 mm), No. 16 (1.18 mm), No. 8 (2.36 mm), No.4 (4.75 mm), 3/8 in. (9.5 mm), 3/4 in. (19.0 mm), 1-1/2 in. (37.5 mm), 3 in. (75 mm), and 6 in. (150 mm)Fly ash the finely divided residue that results from the combustion of ground or powdered coal and that is tra

14、ns-ported by flue gases from the combustion zone to the particle removal system.Grout mixture of cementitious materials and water, or other binding medium, with fine aggregate. High-range water-reducing admixture a water-reducing admixture capable of producing large water reduc-tion or great flowabi

15、lity without causing undue set retarda-tion or entrainment of air in mortar or concrete.Honeycomb voids left in concrete between coarse aggre-gates due to inadequate consolidation.Hydration the chemical reaction between hydraulic cement and water.Hydraulic cement a binding material that sets and har

16、dens by chemical reaction with water and is capable of doing so underwater. For example, portland cement and slag cement are hydraulic cements.Initial setting a degree of stiffening of a cementitious mixture less than final set, generally stated as an empirical value indicating the time required for

17、 the cementitious mixture to stiffen sufficiently to resist, to an established degree, the penetration of a weighted test device. (See also final setting.)Mortar a mixture of cement paste and fine aggregate; in fresh concrete, the material occupying the interstices among particles of coarse aggregat

18、e; in masonry construction, joint mortar may contain masonry cement, or may contain hydraulic cement with lime (and possibly other admixtures) to afford greater plasticity and workability than are attain-able with standard portland cement mortar.Paste see Cement paste.Plastic shrinkage cracking surf

19、ace cracking that occurs in concrete before initial set.Plasticity property of freshly mixed cement paste, concrete, or mortar that determines its resistance to defor-mation or ease of molding.12 CONCRETE FUNDAMENTALSPortland cement a hydraulic cement made by pulver -izing portland-cement clinker an

20、d usually with addition of calcium sulfate to control setting.Pozzolans a siliceous or silico-aluminous material that will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temper-atures to form compounds having cementitious properties (ther

21、e are both natural and artificial pozzolans).Prestressed concrete structural concrete in which internal stresses have been introduced to reduce potential tensile stresses in concrete resulting from loads.Fig. 0.4Rodding is performed using a tamping rod, the length and diameter of the rod may vary ba

22、sed on the size of the sample being consolidated (photo courtesy of PCA)VOCABULARY 13Retarder an admixture that delays the setting of a cementitious mixture.Rock pocket a porous, mortar-deficient portion of hard-ened concrete consisting of coarse aggregate and voids. (See also honeycomb.)Rodding con

23、solidation of concrete by means of a tamping rod (Fig. 0.4). (See also tamping.)Scaling local flaking or peeling away of the near-surface portion of hardened concrete or mortar (Fig. 0.5).Segregation the separation of coarse aggregate from the sand-cement mortar portion of the concrete mixture.Setti

24、ng a chemical process that results in a gradual develop-ment of rigidity of a cementitious mixture, adhesive, or resin.Fig. 0.5Scaling removes the top layer of paste from the concrete (photo courtesy of PCA)14 CONCRETE FUNDAMENTALSSieve a metallic plate or sheet, woven-wire cloth, or other similar d

25、evice with regularly spaced apertures of uniform size mounted in a suitable frame or holder for use in sepa-rating granular material according to size.Silica fume very fine noncrystalline silica produced in electric arc furnaces as a byproduct of the production of elemental silicon or alloys contain

26、ing silicon.Slag cement granulated blast-furnace slag that has been finely ground and that is hydraulic cement.Slump a measure of the consistency of freshly mixed concrete, equal to the subsidence of a molded specimen immediately after removal of the slump cone.Specified compressive strength compres

27、sive strength of concrete used in design.Superplasticizer See High-range water-reducing admixture. Supplementary cementitious material inorganic mate-rial such as fly ash, silica fume, metakaolin, or slag cement that reacts pozzolanically or hydraulically.Tamping the operation of consolidating fresh

28、ly placed concrete by repeated blows or penetrations with a tamper. (See also consolidation and rodding.)Tensile strength maximum stress that a material is capable of resisting under axial tensile loading based on the cross-sectional area of the specimen before loading.Tremie a pipe or tube through

29、which concrete is depos-ited under water, having at its upper end a hopper for filling and a bail for moving the assemblage.Vibration energetic agitation of freshly mixed concrete during placement by mechanical devices, either pneumatic or electric, that create vibratory impulses of moderately high

30、frequency to assist in consolidating the concrete in the form or mold.1. External vibration employs vibrating devices attached at strategic positions on the forms and is particularly appli-cable to manufacture of precast items and for vibration of tunnel-lining forms; in manufacture of concrete prod

31、ucts, external vibration or impact may be applied to a casting table.2. Internal vibration employs one or more vibrating elements that can be inserted into the fresh concrete at selected locations, and is more generally applicable to in-place construction.3. Surface vibration employs a portable hori

32、zontal plat-form on which a vibrating element is mounted.VOCABULARY 15Water-cement ratio (w/c) the ratio of the mass of water, exclusive only of that absorbed by the aggregates, to the mass of portland cement in a cementitious mixture, stated as a decimal and abbreviated as w/c. Water-cementitious m

33、aterials ratio (w/cm) the ratio of the mass of water, excluding that absorbed by the aggregate, to the mass of cementitious material in a mixture, stated as a decimal and abbreviated w/cm. (See also water-cement ratio.)Workability the property of freshly mixed concrete or mortar that determines the

34、ease with which it can be mixed, placed, consolidated, and finished to a homogenous condition.Yield (1) the volume of freshly mixed concrete produced from a known quantity of ingredients; (2) the total mass of ingredients divided by the density mass of the freshly mixed concrete; (3) the number of u

35、nits produced per bag of cement or per batch of concrete.16 CONCRETE FUNDAMENTALSCHAPTER 1INTRODUCTIONThose who work with concrete should know what concrete is made of and how it behaves. They should know the basic properties of concrete, and they should also recognize safety precautions needed to p

36、rotect themselves and other workers when they are placing and finishing concrete.Unlike other building materials that are delivered ready-to-use, most concrete has to be manufactured at or near the jobsite just before it is used. This makes the work of the concrete craftsman important to the success

37、 of the construction project (Fig. 1.1). An alternative is to use precast concrete that is manufactured offsite into the desired shape(s), (typically wall panels) and then trans-ported to the jobsite (Fig. 1.2). Understanding the basics should help workers to produce better concrete. To learn more,

38、study the references shown in Appendix A. Three important sources, frequently refer-enced in this book by their initials, are: American Concrete Institute (ACI): prepares codes, specifications, guides and state-of-the-art reports for design and construction in concrete. www.concrete.org ASTM Interna

39、tional (ASTM): prepares specifi-cations and test methods for concrete materials and ready mixed concrete. www.astm.org Portland Cement Association (PCA): has many publications explaining how to get good quality concrete and how to build with it. www.cement.orgWhat is concrete?Concrete is a mixture o

40、f cement, water, and aggre-gates (stone or sand) with or without admixtures, fibers, or other cementitious mate-rials. Normalweight concrete, the concrete most commonly used for structural purposes, has a density of about 135 to 160 lb/ft3(2160 to 2560 kg/m3). Lightweight structural concrete may hav

41、e an equilibrium density of 90 to 115 lb/ft3(1440 to 1840 kg/m3) or less, whereas special high-density (heavy-weight) concrete has a Fig. 1.1Concrete is not delivered in its final form. The fresh concrete should be placed, consolidated, finished, and cured17density up to about 400 lb/ft3(6400 kg/m3)

42、.Most concrete today is made with portland cement and supplementary cementi-tious materials (SCMs). Concrete is sometimes described as a mixture of two major components: aggre-gates and paste. The paste, made of cement, SCMs, and water, binds the aggregates into a rock-like mass as the paste hardens

43、 (Fig. 1.3). The hardening is a chemical process called hydration, not a drying process, and it can take place under water as well as when exposed to air. Concrete does not harden or cure by drying, because the cement needs moisture to hydrate and harden. When the concrete dries fully it no longer g

44、ains strength.People will often refer to the hardened mixture of cement, water, and aggregates as cement, but this is techni-cally wrong. Concrete is the combination of these mate-rials; only the binding powder is properly called cement (Fig. 1.4).The paste part of the concrete also contains air, ca

45、lled entrapped air, which occurs when air is trapped during mixing, and is usually less than 2 percent by volume. Entrapped air voids are usually scattered, comparable in size to the larger grains of sand. Often, the paste also contains very small spherical air voids, referred to as entrained air, i

46、ntentionally introduced into Fig. 1.2Precast panel constructionFig. 1.3Polished section sawed from hardened concrete. The cement-and-water paste coats each piece of aggregate and fills all spaces between the aggregate particles (photo courtesy CTLGroup)18 CONCRETE FUNDAMENTALSthe mixture by means of

47、 an air-entraining admixture to improve certain properties in both the fresh and hardened concrete. As Fig. 1.5 shows, the greatest part of concrete is the aggregate.Importance of concreteConcrete is the most widely used construction material today. Worldwide, almost 5 tons (4.5 tonnes) of concrete

48、is produced every year for every living human being. This happens because concrete is the cheapest, most readily available material. Fortunately, it is also strong, resistant to water and fire, and readily formable to an infinite variety of sizes and shapes.Concrete has been used to build some of th

49、e largest and tallest of all manmade struc-tures. For example, completed in 2009, the Trump Interna-tional Hotel and Tower in Chicago, IL, stands at 1389 ft (423 m). The primary struc-ture of this building is rein-forced concrete (Fig. 1.6).Although the bulk of conventional concrete has compressive strengths in the Fig. 1.4 Often incorrectly used, people will refer to concrete as cement. Cement is only one ingredient in a concrete mixture. Shown in (a) is cement (powder)(photo courtesy o