ACI 207.1R-96 Mass Concrete Reported by ACI Committee 207 Gary R. Mass Woodrow L. Burgess* Chairman Chairman, Task Group Edward A. Abdun-Nur* Robert W. Cannon David Groner Walter H. Price*† Ernest K. Schrader* Fred A. Anderson* Roy W. Carlson Kenneth D. Hansen Milos Polivka Roger L. Sprouse Richard A. Bradshaw, Jr.* James L. Cope* Gordon M. Kidd Jerome M. Raphael* John H. Stout Edward G. W. Bush James R. Graham* W. Douglas McEwen Patricia J. Roberts Carl R. Wilder James E. Oliverson* *Members of the task group who prepared this report. †Deceased Members of Committee 207 who voted on the 1996 revisions: John M. Scanlon John R. Hess Chairman Chairman, Task Group Dan A. Bonikowsky James L. Cope Michael I. Hammons Meng K. Lee Ernest K. Schrader Robert W. Cannon Luis H. Diaz Kenneth D. Hansen Gary R. Mass Glenn S. Tarbox Ahmed F. Chraibi Timothy P. Dolen James K. Hinds Robert F. Oury Stephen B. Tatro Allen J. Hulshizer Synopsis cause excessive seepage and shortening of the service life of the structure, or may be esthetically objectionable. Many of the principles in mass con- crete practice can also be applied to general concrete work whereby certain Mass concrete is “any volume of concrete with dimensions large enough to economic and other benefits may be realized. require that measures be taken to cope with generation of heat from hydra- tion of the cement and attendant volume change to minimize cracking.” The design of mass concrete structures is generally based on durability, This report contains a history of the development of mass concrete practice economy, and thermal action, with strength often being a secondary con- and discussion of materials and concrete mix proportioning, properties, cern. Since the cement-water reaction is exothermic by nature, the temper- construction methods and equipment, and thermal behavior. It covers tradi- ature rise within a large concrete mass, where the heat is not dissipated, tionally placed and consolidated mass concrete, and does not cover roller- compacted concrete. Mass concrete practices were largely developed from can be quite high. Significant tensile stresses may develop from the volume change associated with the increase and decrease of temperature within concrete dam construction, where temperature-related cracking was first identified. Temperature-related cracking has also been experienced in other the mass. Measures should be taken where cracking due to thermal behav- thick-section concrete structures, including mat foundations, pile caps, ior may cause loss of structural integrity and monolithic action, or may bridge piers, thick walls, and tunnel linings. ACI committee reports, guides, standard practices, design Keywords: admixtures; aggregate gradation; aggregate size; aggregates; air handbooks, and commentaries are intended for guidance in entrainment; arch dams; batching; bridge piers; cements; compressive planning, designing, executing, and inspecting construction. strength; concrete construction; concrete dams; cooling; cracking (fractur- This document is intended for the use of individuals who are ing); creep; curing; diffusivity; durability; fly ash; formwork (construction); competent to evaluate the significance and limitations of its gravity dams; heat generation; heat of hydration; history; instrumentation; content and recommendations and who will accept responsi- mass concrete; mix proportioning; mixing; modulus of elasticity; perme- bility for the application of the material it contains. The ability; placing; Poisson’s ratio; pozzolans; shear properties; shrinkage; American Concrete Institute disclaims any and all responsi- strains; stresses; temperature control; temperature rise (in concrete); ther- bility for the application of the stated principles. The Institute mal expansion; thermal gradient; thermal properties; vibration; volume change. shall not be liable for any loss or damage arising therefrom. Reference to this document shall not be made in contract ACI 207.1R-96 became effective November 21, 1996. This document replaces ACI 207.1R-87. documents. If items found in this document are desired by Copyright Ó 1997, American Concrete Institute. the Architect/Engineer to be a part of the contract docu- 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 electronic or ments, they shall be restated in mandatory language for in- mechanical device, printed, written, or oral, or recording for sound or visual reproduc- corporation by the Architect/Engineer. tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors. 207.1R-1 207.1R-2 ACI COMMITTEE REPORT CONTENTS CHAPTER 1—INTRODUCTION AND HISTORICAL DEVELOPMENTS Chapter 1—Introduction and historical developments, p. 207.1R-2 1.1—Scope 1.1—Scope 1.1.1—“Mass concrete” is defined in ACI 116R as “any 1.2—History volume of concrete with dimensions large enough to require 1.3—Temperature control that measures be taken to cope with generation of heat from hydration of the cement and attendant volume change to 1.4—Long-term strength design minimize cracking.” The design of mass concrete structures is generally based principally on durability, economy, and Chapter 2—Materials and mix proportioning, p. thermal action, with strength often being a secondary rather 207.1R-6 than a primary concern. The one characteristic that distin- 2.1—General guishes mass concrete from other concrete work is thermal 2.2—Cements behavior. Since the cement-water reaction is exothermic by 2.3—Pozzolans and ground slag nature, the temperature rise within a large concrete mass, 2.4—Chemical admixtures where the heat is not quickly dissipated, can be quite high 2.5—Aggregates (see 5.1.1). Significant tensile stresses and strains may de- 2.6—Water velop from the volume change associated with the increase 2.7—Selection of proportions and decrease of temperature within the mass. Measures 2.8—Temperature control should be taken where cracking due to thermal behavior may cause loss of structural integrity and monolithic action, or may cause excessive seepage and shortening of the service Chapter 3—Properties, p. 207.1R-13 3.1—General life of the structure, or may be esthetically objectionable. Many of the principles in mass concrete practice can also be 3.2—Strength applied to general concrete work whereby certain economic 3.3—Elastic properties and other benefits may be realized. 3.4—Creep This report contains a history of the development of mass 3.5—Volume change concrete practice and discussion of materials and concrete 3.6—Permeability mix proportioning, properties, construction methods and 3.7—Thermal properties equipment, and thermal behavior. This report covers tradi- 3.8—Shear properties tionally placed and consolidated mass concrete, and does not 3.9—Durability cover roller-compacted concrete. Roller-compacted concrete is described in detail in ACI 207.5R. Mass concreting practices were developed largely from Chapter 4—Construction, p. 207.1R-22 4.1—Batching concrete dam construction, where temperature-related crack- ing was first identified. Temperature-related cracking also 4.2—Mixing has been experienced in other thick-section concrete struc- 4.3—Placing tures, including mat foundations, pile caps, bridge piers, 4.4—Curing thick walls, and tunnel linings. 4.5—Forms High compressive strengths are usually not required in 4.6—Height of lifts and time intervals between lifts mass concrete structures; thin arch dams are exceptions. 4.7—Cooling and temperature control Massive structures, such as gravity dams, resist loads by vir- 4.8—Grouting contraction joints tue of their shape and mass, and only secondarily by their strength. Of more importance are durability and properties Chapter 5—Behavior, p. 207.1R-29 connected with temperature behavior and the tendency for 5.1—Thermal stresses and cracking cracking. 5.2—Volume change The effects of heat generation, restraint, and volume changes on the design and behavior of massive reinforced el- 5.3—Heat generation ements and structures are discussed in ACI 207.2R. Cooling 5.4—Heat dissipation studies and insulating systems for mass concrete are addressed in 5.5—Instrumentation ACI 207.4R. Mixture proportioning for mass concrete is dis- cussed in ACI 211.1. Chapter 6—References, p. 207.1R-38 6.1—Specified and recommended references 1.2—History 6.2—Cited references 1.2.1—When concrete was first used in dams, the dams 6.3—Additional references were small and the concrete was mixed by hand. The port- land cement usually had to be aged to comply with a “boil- ing” soundness test, the aggregate was bank-run sand and Appendix—Metric examples, p. 207.1R-40 gravel, and proportioning was by the shovelful (Davis MASS CONCRETE 207.1R-3 1963).* Tremendous progress has been made since the early dry consistency was placed in thin layers and consolidated days, and the art and science of dam building practiced today by rigorous hand tamping. has reached a highly advanced state. The selection and pro- Generally, mixed concrete was transported to the forms by portioning of concrete materials to produce suitable strength, wheelbarrow. Where plums were employed in cyclopean durability, and impermeability of the finished product can be masonry, stiff-leg derricks operating inside the work area predicted and controlled with accuracy. moved the wet concrete and plums. The rate of placement 1.2.2—Covered herein are the principal steps from those was at most a few hundred cubic yards a day. Generally, very small beginnings to the present. In large dam construc- there was no attempt to moist cure. tion there is now exact and automatic proportioning and mix- An exception to these general practices was the Lower ing of materials. Concrete in 12-yd3 (9-m3) buckets can be Crystal Springs Dam completed in 1890. This dam is located placed by conventional methods at the rate of 10,000 yd3/day near San Mateo, California, about 20 miles south of San (7650 m3/day) at a temperature of less than 50 F (10 C) as Francisco.