ACI CCS-0-1993 Concrete Fundamentals《混凝土原理》.pdf

1、CACI CCS-O 93 = 0bb2949 O533987 AT9 AC1 CCS-O 93 Ob62949 051398B 735 CONCRETE CRAFTSMAN SERIES - CONCRETE FUNDAMENTALS Robert C. Bates Gregory J. Carr Kenneth D. Cummins Charles M. Dabney Robert E. Glanviile AC1 CCS-O 93 .I 0662949 0.513989 671 AC1 Committee E-703 Wiiiiam R. Phillips Chairman Samuel

2、 A. Greenberg Byron D. Hanson Oswin Keifer, Jr. Jay B. Kinhal Theodore WJ. Marotta C. Raymond Nowacki Paul J. Tikalsky Thomas D. Verti Bradley K. Violetta This document has bem reviewed in accordance with Institute publication procedures. Printed in the United States of America First Printing-Novemb

3、er 1993 Victoria A. Wieczorek-Editorial Production Copyright 0 1993 AMERICAN CONCRETE INSTITUTE PO Box 19150, Redford Station Detroit, Michigan 48219 All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by a

4、ny electronic or mechanical device, printed or written or oral, or recording for sound or visual reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors. The Institute is not responsible for the statements or opi

5、nions in its publications. Institute publications are not able to, nor intended to supplant individual training, responsibility, or judgement of the user. or the supplier of the information presented. LIBRARY OF CONGRESS CATALOG CARD NUMBER 93-73934 AC1 CCS-O 93 0662749 0533990 373 TABLE OF CONTENTS

6、 Preface v Vocabulary . 1 Chapter 1 Introduction . 5 Chapter 2 Concrete Materials . 11 Chapter 3 Mixture Proportioning . 23 Chapter 4 Batching and Mixing Concrete . 35 Chapter 6 Curing and Protection . 61 Chapter 5 Handling. Placing and Consolidating Concrete . 42 Chapter 7 Field Testing and Control

7、 of Concrete Quality . 73 Chapter 8 Evaluating Concrete Strength - Core and Cylinder Strength Tests of Hardened Concrete 84 Appendix A References . 93 Appendix B Conversion Factors . 96 AC1 CCS-O 93 D Obb29Y7 05L399L 22T PREFACE This is the fourth booklet in the Concrete Craftsman Series published b

8、y the American Concrete Institute. This booklet is intended for anyone who wants a simple intro- duction to concrete and concrete construction. Craftsmen in the concrete field may find it particularly useful as a guide for good practice. The first booklet in this series, Slabs on Grade, CCS-1 covere

9、d good construction practices for slabs. The second booklet, Cast-in-Place Walls, CCS-2 described formwork, reinforcement, placing of concrete, curing, and wali finishes. The third booklet, Supported Beams and Slabs, CCS-3 provided technical background on such subjects as shoring, reshoring, form re

10、moval, reinforcement place- ment, and concrete placing, finishing, and curing. Since this book went back to cover the fundamentals, it is numbered accordingly. Concrete Fundamentais, CCS-O starts with the most basic question of ali, “What is con- crete?“ Sections then cover materials, basic construc

11、tion practices, and testing. This booklet is the perfect starting point for someone in the concrete industry, whether they be an apprentice, a journeyman, a foreman, a material supplier, or even a young engineer without field exper- ience. This booklet is not a design aid but rather a guide to good

12、practice. The design of concrete structures is the responsibility of a professional engineer. Designs are usualiy reviewed and approved by local building authorities and are gov- erned by codes such as the Uniform Building Code, Stan- dard Building Code, BOCA Code, or others which usually reference

13、the “AC1 Building Code for Reinforced Con- crete, AC1 318.“ This booklet is not a replacement for any of these documents. It must be kept in mind that plans and specifications for a specific project, and local building code requirements in any area, must be foliowed, even if they differ from the inf

14、ormation in this booklet. V AC1 CCS-O 93 8 0bb2949 0533992 166 0 VOCABULARY If you are using this book as an introduction to con- crete, you will soon notice that a lot of ordinary words like accelerator, bleeding, blistering, honeycomb, slump, and many others have their own very special meaning whe

15、n ap- plied to concrete. To help with these meanings, weve listed some of the terms that appear in this book, along with brief definitions. For longer definitions and for other words not included here, see “Cement and Concrete Ter- minology (AC1 116R),” published by the American Con- crete Institute

16、. Accelerator - Admixture that speeds up the normal set- ting and hardening of concrete. Admimre - Any material deliberately added to concrete before or during mixing, other than cement, water, aggre- gates, and fiber reinforcement. Aggregate - Sand, gravel, crushed stone and similar ma- terials mix

17、ed with cement and water to make concrete. Fine aggregate includes ali particles about Yi in. or less. Particles larger than 95 in. are called coarse aggregate. Air entrainment - Incorporation of minute air bubbles in 1 concrete during mixing. AU-entraining Agent - An admixture for concrete which ca

18、uses air entrainment during mixing. Bleeding - Appearance of water on the surface of fresh concrete. Caused by settlement of the cement grains and particles of aggregate. Blistering - Irregular raising of a thin layer at the con- crete surface during or soon after finishing work is.done. Bug holes -

19、 Small cavities in the formed surface of con- crete, resulting from air bubbles trapped against the. form during placement and consolidation. Cement puste - Cement and water mixture that is a part of concrete. Compressive strength - Measured maximum resistance of a concrete or mortar specimen to axi

20、al compressive load- ing, expressed as a force per unit cross-sectional area (pounds per square in., for example). AC1 CCS-O 93 W 0662949 0533993 OT2 Consistency - The relative mobility or ability of freshly mixed concrete to flow. Consolidation - Process of removing voids from a fresh concrete mix

21、and bringing solid particles together; sometimes referred to as compaction. Crazing - Development of fine random cracks in a con- crete surface; also the resulting pattern of cracks. Curing - Maintaining satisfactory moisture and temper- ature in concrete during its early stages so that desired prop

22、erties may develop. Dropchute - A device used to confine or direct the flow of a failing stream of fresh concrete. Dusting - Development of a powdered material at the surface of hardened concrete. Fineness modulus - A factor for evaluating aggregate; obtained by adding the total percentages of mater

23、ial in the sample that are coarser than each of the sieves in a pre- scribed set, then dividing the sum by 100. High range water reducer - See Superplasticizer. Honeycomb - Voids left in concrete due to failure of the mortar to effectively fill the spaces among the coarse ag- gregate particles. Hydr

24、ation - The chemical reaction between hydraulic ce- ment and water. Hydraulic cement - A cement that sets and hardens by chemical interaction with water and can do so under water. Portland cement is the hydraulic cement most commonly used in concrete. Mortar - A mixture of cement paste and fine aggr

25、egate. In fresh concrete this is the material that occupies the spaces between the particles of coarse aggregate. Puste - See Cement puste. Plustic shrinkage cracking - Cracking that occurs in the surface of fresh concrete soon after it is placed and while it is still plastic. Piusticity - In concre

26、te, the property that determines its ease of molding or resistance to deformation. Portland cement -A hydraulic cement made by finely pul- verizing the clinker formed when a mixture of calcium- and silica-containing minerals is heated to the point of fusion; usuaily has added gypsum interground to c

27、ontrol 2 AC1 CCS-O 93 Obb2949 0533994 T39 the setting and hardening. See also Hydraulic cement. Pozzolans - Siliceous or siliceous and aluminous materials that have little or no cementitious value when used alone. In finely divided form, in the presence of moisture, they react chemically with the ca

28、lcium hydroxide (which is formed in concrete when portland cement hydrates) to form compounds that have cementitious properties. Most natural pozzolans are derived from volcanic material, while fly ash is a common industrial byproduct pozzolan. Prestressed concrete - Concrete in which internal compr

29、es- sion stresses are introduced to counteract tensile stresses produced by service loads. e prestress is commonly in- troduced by tensioning tendons either before casting the concrete (pretensioned concrete), or after the concrete has hardened (post-tensioned concrete). Retarder - An admixture that

30、 delays the initial setting of concrete. Rockpocbt - A porous, mortar-deficient portion of har- dened concrete consisting primarily of coarse aggregate and voids. Salamander - Portable heat source, usuaiiy oil burning, used to heat an enclosure around or over newly placed concrete. Scahg - Local fla

31、king or peeling away of the near-sur- face portion of hardened concrete or mortar. Segregation -The separation of coarse aggregate from the sand-cement mortar portion of the concrete mix. Slump - A measure of the consistency of fresh concrete, equal to the subsidence of a molded specimen immediately

32、 after removal of the slump cone. Specified compressive strength - Compressive strength as required by contract documents andor local codes, given in force per unit area, such as psi (pounds per square in.). Supetplusticizers - More precisely called high range water reducers, these are admixtures th

33、at can temporarily make concrete flowable and easy to place. Alternatively, they can be used to reduce necessary water while improving concrete workability. Tensile strength - Maximum force per unit area (pounds per square in., for example) that a material is able to resist when loaded axiaily in te

34、nsion. Tremie - A pipe or tube through which concrete is de- 3 AC1 CCS-O 93 E3 0bb2749 0533995 975 posited under water. Water-cement ratio -The ratio of the total amount of wa- ter (including water in HRWR) to the amount of cement in a concrete mix, preferably stated on the basis of weight or mass;

35、frequently abbreviated WIC. Recently, this term is often changed to water-cementitious materials ratio to account for the use of pozzolans to replace part of the cement in a mix. concrete. Workability - The property of freshly mixed concrete that determines the ease and homogeneity with which it can

36、 be mixed, placed, consolidated, and finished. Yield - The volume of freshly mixed concrete produced from a known quality of ingredients; the total weight of ingredients divided by the unit weight of the freshly mixed 4 AC1 CCS-O 93 M 0662949 0513996 BOL CHAPTER 1 INTRODUCTION People who work with c

37、oncrete should know what con- crete is made of and how it behaves. They should know the basic properties of concrete and they should also recognize safety precautions needed to protect themselves and other workers when they are placing and finishing concrete. Unlike other building materials that are

38、 delivered ready-to-use, concrete has to be manufactured at or near the job site just before it is used. This makes the work of the concrete craftsman doubly important to the success of the construction project. Understanding the basics should help workers to pro- duce better concrete. This book wil

39、l introduce you to the basics. To learn more; you may want to study some of the references shown in the appendix (page 93). Three impor- tant sources, frequently referenced in this book by their initials, are: American Concrete Institute (ACI): prepares codes, standards, and guides for design and co

40、nstruction in con- crete. American Society for Testing and Materials (ASTM): prepares specifications and test methods for concrete materials and ready-mixed concrete. Portland Cement Association (KA): has many publi- cations explaining how to get good concrete and how to build with it. What is concr

41、ete? Concrete is a mixture of cement, water, and aggregates (stone or sand). Nonnul-weight concrete, the concrete most commonly used for structural purposes, weighs about 140- 150 lb per CU ft. Lightweight structural concrete may weigh 100-110 lb per CU ft or less, while special heavyweight concrete

42、s weigh 180-400 lb per CU ft, or more. Most concretes today are made with portland cement. Sometimes we talk about concrete as a mixture of two major components: aggregates and paste. The paste, made of cement and water, binds the aggregates into a rock-like mass as the paste hardens (see Fig. 1.1).

43、 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, be- cause the cement needs moisture to hydrate and harden. When the concrete dries fully it no longer gains stren

44、gth. Workers sometimes refer to the mixture of cement, wa- ter and aggregates as cement, but this is technically wrong. 5 AC1 CCS-O 93 0662949 0513997 748 6 CEMENT 10%) AIR 5% AGGREGATE Fig. 1.2-Proportions by absolute volume of materials in a typical air-entrained concrete, freshly mixed. In other

45、mixes total aggregate may range from 60 to 75percent and cement from 7 to 15 percent very small spherical air voids, referred to as entrained air, intentionally introduced into the mix by means of an air- entraining admixture (described later) to improve certain properties in both the fresh and hard

46、ened concrete. As the diagram shows (see Fig. l.Z), the greatest part of concrete Fig. 1.1-Polished section sawed from hardened concrete. The cement-and-wuter paste coats each piece of aggregate and flk all spaces between the aggregate particles (photo courtey Portland Cement Association) Only the b

47、inding powder is properly called cement. The paste part of the concrete also contains air, called entrapped air, usually less than 2 percent by volume. En- trapped air voids are usually scattered, comparable in size to the larger grains of sand. Often the paste also contains AC1 CCS-O 93 Obb2949 053

48、3998 b4 is the aggregate. Importance of concrete Concrete is the most widely used construction material today. Worldwide about one ton is produced every year for every living human being. This happens because con- crete is the cheapest, most readily available material. Fortunately, it is also strong

49、, resistant to water and fire, and readily formable to an infinite variety of sizes and shapes. Concrete has been used to build some of the largest and tallest of all manmade structures. For example the CN Tower, the worlds tallest free-standing manmade object, has a concrete structure 1465 feet tall to support an antenna mast that reaches 1815 feet. Although the buk of conventional concrete has com- pressive strength in the range of 3000 to 6000 psi (pounds per square in.), continuing advances in concrete tech- nology are making ever-higher strengths available. Con- crete for high-rise