Frequently Asked Questions

Technical Questions

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




Question: How is the selection of mixture proportions affected by the materials to be used and the placing requirements?

Question: Materials used to produce portland cement

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

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

Question: Improving the abrasion resistance of concrete

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

Question: Material Requirements for Mass Concrete

Question: Embedded metals other than reinforcing steel

Question: What are high-density aggregates?

Question: Important requirements of a concrete aggregate

Question: What is an admixture?

Question: What is involved in the process of mixture proportioning?

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

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

Question: Mixture design and strength submittals

Question: What is calcium-aluminate cement?

Question: Using cube tests in lieu of cylinder tests

Question: Hardening of hydraulic cement

Question: Requirements for a successful concrete structure

Question: Requirements for durable concrete

Question: Definition of setting time

Question: The difference between setting and hardening

Question: Measurement of setting time

Question: Heat of hydration and the importance of controlling it

Question: Strength of concrete

Question: The making of portland cement

Question: The purpose of calcium sulfate (gypsum)

Question: Factors affecting cement properties

Question: Definition of “hot cement”

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 a natural pozzolan?

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: What is aggregate?

Question: Requirements for storing and handling aggregate

Question: Why is combined aggregate grading used?

Question: Aggregate classification by density

Question: Advantages of low-density 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: What is an air-entraining admixture?

Question: What are water-reducing admixtures?

Question: What are set-controlling admixtures?

Question: Specialty admixtures

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

Question: Would adding more cement serve the purpose of admixtures?

Question: Do some water-reducing admixtures induce bleeding?

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

Question: Definition of controlled low-strength material (CLSM)

Question: The most important single factor affecting compressive strength

Question: What correction should be made for absorbed water and surface water carried by the aggregates?

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

Question: How can the adequacy of mixing be determined?

Question: What methods are commonly used to ensure sufficient moisture for curing concrete?

Question: What methods are used for protecting concrete against low temperatures?

Question: What steps are taken in the repair of concrete structures?

Question: Are epoxy resins widely used in concrete construction and repair?

Question: When is the slump test useful in detecting changes in the concrete?

Question: Curling, shrinkage, and w/cm

Question: Consolidation of concrete—required or not?

Question: What is architectural concrete?

Question: Curing and curling of concrete slabs over vapor retarders

Question: Decorative concrete finishes

Question: How to Control Mass Concrete Temperature during Construction

Question: Water Curing Mass Concrete Structures

Question: Joint deterioration mechanism and prevention

Question: Chloride concentration in soil and exposure classes

Question: What is mass concrete?

Question: Pozzolans in mass concrete

Question: The effect of pozzolans on freezing and thawing resistance


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