Frequently Asked Questions

Technical Questions

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




Question: Curing and curling of concrete slabs over vapor retarders

Question: Curling, shrinkage, and w/cm

Question: What are shrinkage-compensating expansive cement and concrete?

Question: Heat of hydration and the importance of controlling it

Question: How does the relative amount of each ingredient used in concrete influence the properties of concrete?

Question: What is mass concrete?

Question: How to Control Mass Concrete Temperature during Construction

Question: Consolidation of concrete—required or not?

Question: Could a sulfate-resisting cement and slag cement be combined and used for concrete exposed to sulfates attack?

Question: The effect of pozzolans on freezing and thawing resistance

Question: Using cube tests in lieu of cylinder tests

Question: Definition of concrete, hydraulic cement, mortar, and grout

Question: The effect of changes in proportions of the fine and coarse aggregate or the quantity of cementitious material on the strength

Question: Mixture design and strength submittals

Question: Pozzolans in mass concrete

Question: The most important single factor affecting compressive strength

Question: What does a pozzolan do in the concrete?

Question: The ultimate objective in proportioning concrete

Question: What consideration should be given to water that may be lost from concrete between the time it leaves the mixer and its final consolidation in the form?

Question: Definition of setting time

Question: How do the requirements of placing affect the selection of proportions of aggregates and cementitious material?

Question: How is workability measured and specified?

Question: Joint deterioration mechanism and prevention

Question: Factors affecting time of setting

Question: Importance of using pozzolans in hydraulic and environmental structures

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

Question: Definition of portland cement

Question: Are the proportions of ingredients inter-related to produce concrete of a given workability?

Question: What is calcium-aluminate cement?

Question: Factors governing the strength of concrete

Question: Using and handling pozzolans

Question: What allowance should be made for strengths where air-entrained concrete is to be used?

Question: Why is combined aggregate grading used?

Question: Commonly used accelerating admixture

Question: The difference between setting and hardening

Question: Why is Type IV cement rarely produced and Type V cement rarely used?

Question: The effect of pozzolans on shrinkage

Question: What is a natural pozzolan?

Question: The effect of aggregate grading on concrete strength

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

Question: What is autogenous shrinkage?

Question: Standard specifications for cements

Question: The effect of pozzolans on water demand

Question: What water-cementitious material ratio should be used for a particular job when strength requirements are to govern?

Question: The making of portland cement

Question: What is a pozzolan?

Question: The effect of water-cementitious ratio on permeability and shrinkage

Question: Measurement of setting time

Question: Why is a plastic consistency usually desirable for placing concrete?

Question: Material Requirements for Mass Concrete

Question: What is slag cement or ground granulated blast-furnace slag (GGBFS)

Question: The effect of aggregate shape on concrete strength

Question: Benefits of using slag cement

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

Question: Characteristics of cement that affect compressive strength

Question: Effects of cement fineness on cement properties

Question: Notable changes in modern portland cement properties

Question: Chloride concentration in soil and exposure classes

Question: The purpose of calcium sulfate (gypsum)

Question: Factors affecting cement properties

Question: Definition of “hot cement”

Question: If the cementitious material paste is not sufficient in amount to float all of the aggregate particles, what is the result?

Question: Hardening of hydraulic cement

Question: Unsoundness in portland cement

Question: How should the aggregates and other ingredients be measured to obtain uniformity in proportions?

Question: Are pozzolans all alike?

Question: What is an admixture?

Question: The earliest use of portland cement

Question: Materials used to produce portland cement

Question: Do different admixtures of a given type always perform the same?

Question: Is personal protection needed when handling concrete?

Question: What are the essential requirements of consistency?

Question: What is an expansive cement and what are the different types of expansive cement?

Question: What are blended cements?

Question: How much does a bag of cement weigh?


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