Technical Questions

ACI Committees, Membership, and Staff have answered common questions on a variety of concrete related topics.

Question: Curing Cylinders for Acceptance Testing

Question: Rebound hammer and in-place strength testing

Question: Why is a spherically seated bearing block required in testing cylinders?

Question: Size of test cylinder

Question: ACI code for evaluating existing buildings prior to repair

Question: Low-strength cylinder test results

Question: Estimating in-place concrete strength

Question: What methods of capping are recommended for compression specimens?

Question: What are rebound, penetration resistance, and pullout tests?

Question: Air tests for non-air-entrained concrete

Question: Using core strength to calculate compressive strength of an existing structure

Question: Maximum temperature limits for hot-weather concreting

Question: Strength of concrete

Question: How can it be determined that an admixture will serve its intended purpose?

Question: How is the required strength selected, measured, and obtained?

Question: Are there any tests that may be made directly on the structure to determine if the concrete has ...

Question: What test conditions affect the results of compressive strength tests of concrete?

Question: What procedure should be followed for standard curing of specimens for strength tests?

Question: Are load tests on completed structures ever employed?

Question: How are properties of concrete in the structure measured?

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: 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 shrinkage of concrete determined?

Question: Using cube tests in lieu of cylinder tests

Question: Standards for 7-day and 28-day strength test results

Question: Consistency, plastic consistency, and workability

Question: Factors governing the strength of concrete

Question: The effect of air content on concrete strength

Question: Resistance to cycles of freezing and thawing

Question: Unsoundness in portland cement

Question: How can durable aggregates be ensured?

Question: The effect of maximum size of aggregate on concrete strength

Question: Why is the workability of concrete important?

Question: How is workability measured and specified?

Question: Precautions against sulfate attack

Question: Improving the abrasion resistance of concrete

Question: Protecting against excessive expansion due to alkali-aggregate reaction (AAR)

Question: The most important single factor affecting compressive strength

Question: How is the water-cementitious material ratio (w/cm) expressed?

Question: The effect of changes in proportions of the fine and coarse aggregate or the quantity of cementi...

Question: If time is not available for preliminary tests, how can the desired strengths be ensured?

Question: Are there data relating w/cm to flexural strength that are as reliable as those for compressive ...

Question: Can tests be conducted by anyone?

Question: What tests are necessary or desirable in making a series of trial mixtures to arrive at a suitab...

Question: Can trial mixtures be made with full-size batches at the start of a job?

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: Is the slump test of value as a measure of consistency or workability?

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: Does the method of molding test specimens affect the test results?

Question: What irregularities are to be avoided in the test specimen?

Question: Does a wet specimen test higher than a dry one?

Question: Is storing the specimens on the structure always a satisfactory procedure for estimating in-plac...

Question: Is the cutting of cores or other shaped specimens directly from a completed structure ever used ...

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: Alternative methods for measuring crack width

Question: Mixture design and strength submittals

Question: Curing Test Specimen at High Temperatures

Question: Addition of lime in curing tanks

Question: Definition of setting time

Question: The difference between setting and hardening

Question: Measurement of setting time

Question: False and flash set

Question: Definition of portland cement

Question: The cause of false set

Question: Important requirements of a concrete aggregate

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