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Founded in 1904 and headquartered in Farmington Hills, Michigan, USA, the American Concrete Institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensus-based standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete design, construction, and materials, who share a commitment to pursuing the best use of concrete.
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Home > Tools > Frequently Asked Questions
Question: Tolerances for concrete slabs supporting steel tanks
Question: What is meant by properly cured concrete?
Question: What methods of capping are recommended for compression specimens?
Question: How is the shrinkage of concrete determined?
Question: Using cube tests in lieu of cylinder tests
Question: Air tests for non-air-entrained concrete
Question: Using core strength to calculate compressive strength of an existing structure
Question: Standards for 7-day and 28-day strength test results
Question: Size of test cylinder
Question: Maximum temperature limits for hot-weather concreting
Question: Low-strength cylinder test results
Question: Estimating in-place concrete strength
Question: Definition of setting time
Question: The difference between setting and hardening
Question: Measurement of setting time
Question: False and flash set
Question: Strength of concrete
Question: Air content common limits
Question: Factors affecting permeability
Question: The relationship between porosity and permeability of concrete
Question: Standard specifications for cements
Question: The purpose of calcium sulfate (gypsum)
Question: Factors affecting cement properties
Question: Effects of cement fineness on cement properties
Question: Unsoundness in portland cement
Question: The cause of false set
Question: Characteristics of cement that affect compressive strength
Question: Why is Type IV cement rarely produced and Type V cement rarely used?
Question: What is slag cement or ground granulated blast-furnace slag (GGBFS)
Question: Benefits of using slag cement
Question: What is a pozzolan?
Question: What does a pozzolan do in the concrete?
Question: Using and handling pozzolans
Question: Importance of using pozzolans in hydraulic and environmental structures
Question: Are pozzolans all alike?
Question: The effect of pozzolans on water demand
Question: The effect of pozzolans on shrinkage
Question: What is fly ash?
Question: Do all fly ashes behave in a similar way?
Question: What is silica fume?
Question: What are blended cements?
Question: What are shrinkage-compensating expansive cement and concrete?
Question: Can you use any source of water as mixing water?
Question: What is aggregate?
Question: Requirements for storing and handling aggregate
Question: Why is combined aggregate grading used?
Question: Aggregate classification by density
Question: What are high-density aggregates?
Question: Important requirements of a concrete aggregate
Question: The effect of aggregate on concrete durability
Question: How can durable aggregates be ensured?
Question: Characteristics of aggregate affecting concrete strength
Question: The effect of surface texture and cleanness on concrete strength
Question: The effect of aggregate shape on concrete strength
Question: The effect of aggregate grading on concrete strength
Question: The effect of maximum size of aggregate on concrete strength
Question: The effect of aggregate strength on concrete strength
Question: The effect of aggregate characteristics on concrete shrinkage and permeability
Question: What is an admixture?
Question: What is an air-entraining admixture?
Question: What are water-reducing admixtures?
Question: What are set-controlling admixtures?
Question: Do different admixtures of a given type always perform the same?
Question: How can it be determined that an admixture will serve its intended purpose?
Question: How are the relatively small dosages of an admixture measured reliably and placed in the mixer?
Question: Do some water-reducing admixtures induce bleeding?
Question: Are retarding admixtures reliable as to the time of setting?
Question: What fibers are used in concrete?
Question: Why is the workability of concrete important?
Question: How is workability measured and specified?
Question: How is the required strength selected, measured, and obtained?
Question: Improving the abrasion resistance of concrete
Question: The most important single factor affecting compressive strength
Question: How can the adequacy of mixing be determined?
Question: Are there any tests that may be made directly on the structure to determine if the concrete has ...
Question: How should samples of freshly mixed concrete be taken in the field to provide information on con...
Question: How can the surface or free water carried by the aggregates be determined?
Question: How is the slump test made?
Question: Why is the slump test not an absolute measure of consistency or workability?
Question: When is the slump test useful in detecting changes in the concrete?
Question: When does the slump test provide a useful indication of workability?
Question: What test is available to evaluate the behavior of no-slump concrete as it is vibrated?
Question: How is the air content of freshly mixed concrete determined?
Question: Is density a good indicator of air content?
Question: How is the temperature of concrete measured?
Question: What test conditions affect the results of compressive strength tests of concrete?
Question: Does the method of molding test specimens affect the test results?
Question: What irregularities are to be avoided in the test specimen?
Question: What procedure should be followed for standard curing of specimens for strength tests?
Question: What are the ultrasonic pulse velocity and the pulse echo tests?
Question: Is pulse velocity related to strength?
Question: What other uses are there for the pulse velocity?
Question: What are rebound, penetration resistance, and pullout tests?
Question: Why are many non-destructive tests used as “estimators” of concrete strength?
Question: How is strength estimated by the maturity method?
Question: How is the air content of hardened concrete determined?
Question: How is the resistance to freezing and thawing determined?
Question: How is the permeability of concrete determined?
Question: How is the resistance to sulfate determined?
Question: How is the resistance to alkali-aggregate reaction (AAR) determined?
Question: How is the abrasion resistance of concrete determined?
Question: Could a sulfate-resisting cement and slag cement be combined and used for concrete exposed to su...
Question: Curing and curling of concrete slabs over vapor retarders
Question: Curing Cylinders for Acceptance Testing
Question: Tolerances for floors supporting operable partitions
Question: Addition of lime in curing tanks
Question: Rebound hammer and in-place strength testing
Search other resources on the ACI website for answers to technical questions