The American Concrete Institute is a non-profit technical society and standard developing organization. ACI was founded in 1904 and its headquarters are currently located in Farmington Hills, Michigan, USA.
This report is the authoritative glossary for cement and concrete technology. It is to be used generally and specifically in ACI technical communications, correspondence, and publications. One mission of Committee 116 is to produce and maintain a list of terms with their meaning in the field of cement and concrete technology. Committee 116 has tried to produce a glossary that will be useful, comprehensive, and up-to-date. It recognizes, however, that the listing may not be complete and that some definitions may be at variance with some commonly accepted meanings. Users of the glossary are invited to submit suggestions for changes and additions to ACI Headquarters for consideration by Committee 116 when preparing future editions. In the event that a user disagrees with any of the definitions, it is hoped that the reasons for such will be given to the committee. The committee is aware that some of the definitions included may seem entirely self-evident to an expert in the concrete field. This occurs because no term has been discarded if there was reason to believe it would appear to be technical in nature to a casual reader of the ACI literature. The committee voted to use the following procedural rules: 1. Each definition shall be stated in one sentence; 2. Each definition shall consist of the term printed in boldface, a dash, and the definition statement; 3. The definition statement shall not repeat the term and should state the class or group and identify the features unique to the term; as " mathematics - the science of numbers and spaces "; 4. Verbs should be stated in the infinitive rather than the participle; for example the term to be defined should be "abrade " not "abrading "; 5. Notes may be appended to definition statements; 6. Cross references may take the place of a definition as "green concrete - see concrete, green. " They also may call attention to related items as "flint - a variety of chert. (See also chert). " Where the committee has found two or more terms with the same meaning, the definition is given where the preferred term appears, the synonyms are cross referenced to the preferred term, and in many cases, the fact is stated; 7. Generally, where there are a number of terms, the last word of which is the same, the definitions are given where the terms are listed in the inverted form, as "cement, low-heat " rather than "low-heat cement, " but under the latter entry, there will be a cross reference "see cement, low-heat; " and 8. In selecting terms and definitions, there shall be coordination with the terminology subcommittees of ASTM Committees C-1 on Cement, and C-9 on Concrete and Concrete Aggregates.
This guide presents a system for making a condition survey of concrete in service. A condition survey is an examination of concrete for the purpose of identifying and defining areas of distress. The system is designed to be used in recording the history of a project from inception through construction and subsequent life of the structure. While it probably will be used most often in connection with the survey of concrete that is showing some degree of distress, its application is recommended for all concrete structures. In any case, records of the materials and construction practices used should be maintained because they are difficult to obtain at a later date. The committee has attempted to include pertinent items that might have a bearing on the performance of the concrete. Those making the survey should, however, not limit their investigation to the items listed, thereby possibly overlooking other contributing factors. Following the guide does not eliminate the need for intelligent observations and the use of sound judgement. Those performing the survey should be experienced and competent in this field. In addition to verbal descriptions, numerical data obtained by laboratory tests and field tests and measurements should be obtained wherever possible. Photographs, including a scale to indicate dimensions, are of great value in showing the condition of concrete. The check list is provided to facilitate a thorough survey. The definition of terms and associated photographs are an attempt to standardize the reporting of the condition of the concrete in a structure. This guide should be used in conjunction with the following: 1. ACI Committee 116 "Cement and Concrete Terminology " (ACI 116R). 2. ACI Committee 311 "Recommended Practice for Concrete Inspection " (ACI 311.1R). 3. ACI Committee 201, "Guide to Durable Concrete " (ACI 201.2R).
Durability of hydraulic-cement concrete is defined as its ability to resist weathering action, chemical attack, abrasion, or any other process of deterioration. Durable concrete will retain its original form, quality, and serviceability when exposed to its environment. Some excellent general references on the subject are available (Klieger 1982; Woods 1968). This guide discusses the more important causes of concrete deterioration and gives recommendations on how to prevent such damage. Chapters on freezing and thawing, aggressive chemical exposure, abrasion, corrosion of metals, chemical reactions of aggregates, repair of concrete, and the use of protectivebarrier systems to enhance concrete durability are included. Fire resistance of concrete and cracking are not covered, because they are covered in ACI 216, ACI 224R and ACI 224.1R, respectively. Freezing and thawing in the temperate regions of the world can cause severe deterioration of concrete. Increased use of concrete in countries with hot climates has drawn attention to the fact that deleterious chemical processes, such as corrosion and alkali-aggregate reactions, are aggravated by high temperatures. Also, the combined effects of cold winter and hot summer exposures should receive attention in proportioning and making of durable concrete. Water is required for the chemical and most physical processes to take place in concrete, both the desirable ones and the deleterious. Heat provides the activation energy that makes the processes proceed. The integrated effects of water and heat, and other environmental elements are important and should be considered and monitored. Selecting appropriate materials of suitable composition and processing them correctly under existing environmental conditions is essential to achieve concrete that is resistant to deleterious effects of water, aggressive solutions, and extreme temperatures. Freezing-and-thawing damage is fairly well understood. The damage is accelerated, particularly in pavements by the use of deicing salts, often resulting in severe scaling at the surface. Fortunately, concrete made with quality aggregates, low water-cement ratio (w/c), proper air-void system, and allowed to mature before being exposed to severe freezing and thawing is highly resistant to such damage. Sulfates in soil, ground water, or seawater are resisted by using suitable cementitious materials and a properly proportioned concrete mixture subjected to proper quality control. Because the topic of delayed ettringite formation (DEF) remains a controversial issue and is the subject of various ongoing research projects, no definitive guidance on DEF is provided in this document. It is expected that future versions of this document will address DEF in significant detail. Quality concrete will resist occasional exposure to mild acids, but no concrete offers good resistance to attack by strong acids or compounds that convert to acids; special protection is necessary in these cases. Abrasion can cause concrete surfaces to wear away. Wear can be a particular problem in industrial floors. In hydraulic structures, particles of sand or gravel in flowing water can erode surfaces. The use of high-quality concrete and, in extreme cases, a very hard aggregate, will usually result in adequate durability under these exposures. The use of studded tires on automobiles has caused serious wear in concrete pavements; conventional concrete will not withstand this damage. The spalling of concrete in bridge decks is a serious problem. The principal cause of reinforcing-steel corrosion is mainly due to the use of deicing salts. The corrosion produces an expansive force that causes the concrete to spall above the steel. Ample cover over the steel and use of a low-permeability, air-entrained concrete will ensure durability in the majority of cases, but more positive protection, such as epoxy-coated reinforcing steel, cathodic protection, or chemical corrosion inhibitors, is needed for severe exposures. Although aggregate is commonly considered to be an inert filler in concrete, that is not always the case. Certain aggregates can react with alkalies in cement, causing expansion and deterioration. Care in the selection of aggregate sources and the use of low-alkali cement, pre-tested pozzolans, or ground slag will alleviate this problem. The final chapters of this report discuss the repair of concrete that has not withstood the forces of deterioration and the use of protective-barrier systems to enhance durability. The use of good materials and proper mixture proportioning will not ensure durable concrete. Quality control and workmanship are also absolutely essential to the production of durable concrete. Experience has shown that two areas should receive special attention: 1) control of entrained air and 2) finishing of slabs. ACI 311.1R describes good concrete practices and inspection procedures. ACI 302.1R describes in detail proper practice for consolidating and finishing floors and slabs. ACI 325.9R reviews pavement installation. ACI 330R discusses parking lot concrete, and ACI 332R covers residential concrete, including driveways and other flatwork.
"Mass concrete " is defined in ACI 116R as "any volume of concrete with dimensions large enough to require that measures be taken to cope with generation of heat from hydration of the cement and attendant volume change to minimize cracking. " The design of mass concrete structures is generally based principally on durability, economy, and thermal action, with strength often being a secondary rather than a primary concern. The one characteristic that distinguishes mass concrete from other concrete work is thermal behavior. Since the cement-water reaction is exothermic by nature, the temperature rise within a large concrete mass, where the heat is not quickly dissipated, can be quite high (see 5.1.1). Significant tensile stresses and strains may develop from the volume change associated with the increase and decrease of temperature within the mass. Measures 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 life of the structure, or may be aesthetically objectionable. Many of the principles in mass concrete practice can also be applied to general concrete work whereby certain economic and other benefits may be realized. This report contains a history of the development of mass concrete practice and discussion of materials and concrete mix proportioning, properties, construction methods and equipment, and thermal behavior. This report covers traditionally placed and consolidated mass concrete, and does not cover roller-compacted concrete. Roller-compacted concrete is described in detail in ACI 207.5R. Mass concreting practices were developed largely from concrete dam construction, where temperature-related cracking was first identified. Temperature-related cracking also has been experienced in other thick-section concrete structures, including mat foundations, pile caps, bridge piers, thick walls, and tunnel linings. High compressive strengths are usually not required in mass concrete structures; thin arch dams are exceptions. Massive structures, such as gravity dams, resist loads by virtue of their shape and mass, and only secondarily by their strength. Of more importance are durability and properties connected with temperature behavior and the tendency for cracking. The effects of heat generation, restraint, and volume changes on the design and behavior of massive reinforced elements and structures are discussed in ACI 207.2R. Cooling and insulating systems for mass concrete are addressed in ACI 207.4R. Mixture proportioning for mass concrete is discussed in ACI 211.1.
This report is primarily concerned with limiting the width of cracks in structural members that occur principally from restraint of thermal contraction. A detailed discussion of the effects of heat generation and volume changes on the design and behavior of mass reinforced concrete elements and structures is presented. It is written primarily to provide guidance for the selection of concrete materials, mix requirements, reinforcement requirements and construction procedures necessary to control the size and spacing of cracks. Particular emphasis is placed on the effect of restraint to volume change in both preventing and causing cracking and the need for controlling peak concrete temperature. The quality of concrete for resistance to weathering is not emphasized in recommending reduced cements contents; however, it should be understood that the concrete should be sufficiently durable to resist expected service conditions. The report can be applied to any concrete structure with a potential for unacceptable cracking; however, its general application is to massive concrete members 18 in. or more in thickness.
Scope and objective This report presents a discussion of special construction procedures which can be used to control the temperature changes which occur in concrete structures. The principal construction practices covered are precooling of materials, postcooling of in-place concrete by embedded pipes, and surface insulation. Other design and construction practices, including the selection of cementing materials, aggregates, chemical admixtures, cement content, and strength requirements are not within the scope of this report. The objective of this report is to summarize experiences with cooling and insulating systems, and to offer guidance on the selection and application of these procedures in design and construction for controlling thermal cracking in all types of concrete structures.
This report outlines the causes, control, maintenance, and repair of erosion in hydraulic structures. Such erosion occurs from three major causes: caviration, abrasion, and chemical attack. Design parameters, materials selection and quality, environmental factors, and other issues affecting the performance of concrete are discussed. Evidence exists to suggest that given the operating characteristics and conditions to which a hydraulic structure will be subjected, it can be designed to mitigate future erosion of the concrete. However, operational factors change or are not clearly known and hence erosion of concrete surfaces occurs and repairs must follow. This report briefly treats the subject of concrete erosion and repair and provides numerous references to detailed treatment of the subject.
This Standard Practice describes methods for selecting proportions for hydraulic cement concrete made with and without other cementitious materials and chemical admixtures. This concrete consists of normal and/or high density aggregates (as distinguished from lightweight aggregates) with a workability suitable for usual cast-in-place construction (as distinguished from special mixtures for concrete products manufacture). Also included is a description of methods used for selecting proportions for mass concrete. Hydraulic cements referred to in this Standard Practice are portland cement (ASTM C 150) and blended cement (ASTM C 595). The Standard does not include proportioning with condensed silica fume. The methods provide a first approximation of proportions intended to be checked by trial batches in the laboratory or field and adjusted, as necessary, to produce the desired characteristics of the concrete. U.S. customary units are used in the main body of the text. Adaption for the metric system is provided in Appendix 1 and demonstrated in an example problem in Appendix 2. Test methods mentioned in the text are listed in Appendix 3.
Purpose The purpose of this standard is to provide generally applicable methods for selecting and adjusting mixture proportions for structural lightweight concrete. These methods are also applicable to concretes containing a combination of lightweight and normal weight aggregate. Discussion in this standard is limited to structural grade, lightweight aggregates, and structural lightweight aggregate concretes. Structural lightweight aggregate concrete is defined as concrete which: (a) is made with lightweight aggregates conforming to ASTM C330. (b) has a compressive strength in excess of 2500 psi at 28 days of age when tested in accordance with methods stated in ASTM C330, and (c) has an air dry weight not exceeding 115 lb/ft(3) as determined by ASTM C567. Concrete in which a portion of the lightweight aggregate is replaced by normal weight aggregate is within the scope of this standard. When normal weight fine aggregate is used, it should conform to the requirements of ASTM C33. The use of pozzolanic and chemical admixtures is not covered in this standard.