Frequently Asked Questions

In This Section

Other Sources for Answers

Search other resources on the ACI website for answers to technical questions

Technical Questions

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



Found 92 FAQs.

Question: Embedded metals other than reinforcing steel

Question: Curing and curling of concrete slabs over vapor retarders

Question: Can fresh concrete be used around aluminum framing or in aluminum molds??

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

Question: Curling, shrinkage, and w/cm

Question: What is mass concrete?

Question: Heat of hydration and the importance of controlling it

Question: How to Control Mass Concrete Temperature during Construction

Question: What does ACI recommend regarding water-cement (w/c) ratios or admixtures to improve workability...

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

Question: Consolidation of concrete—required or not?

Question: Requirements for durable concrete

Question: Requirements for storing and handling aggregate

Question: Using cube tests in lieu of cylinder tests

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

Question: Definition of setting time

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

Question: Importance of using pozzolans in hydraulic and environmental structures

Question: Mixture design and strength submittals

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

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

Question: The most important single factor affecting compressive strength

Question: Water Curing Mass Concrete Structures

Question: Do some water-reducing admixtures induce bleeding?

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

Question: How can durable aggregates be ensured?

Question: Decorative concrete finishes

Question: How do fibers affect the workability of concrete? Do fibers require additional water for placement?

Question: Factors affecting permeability

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

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

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

Question: Joint deterioration mechanism and prevention

Question: Benefits of using slag cement

Question: What does a pozzolan do in the concrete?

Question: Specialty admixtures

Question: Improving the abrasion resistance of concrete

Question: Characteristics of cement that affect compressive strength

Question: Using and handling pozzolans

Question: The effect of pozzolans on shrinkage

Question: What is calcium-aluminate cement?

Question: Why use fiber-reinforced concrete?

Question: Advantages of low-density aggregate

Question: Why is combined aggregate grading used?

Question: The effect of pozzolans on water demand

Question: What is a natural pozzolan?

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

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

Question: The effect of aggregate grading on concrete strength

Question: The difference between setting and hardening

Question: What is an air-entraining admixture?

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

Question: Characteristics of aggregate affecting concrete strength

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

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

Question: How can the adequacy of mixing be determined?

Question: The making of portland cement

Question: What are set-controlling admixtures?

Question: What is a pozzolan?

Question: What is fiber-reinforced concrete?

Question: Measurement of setting time

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

Question: Do all fly ashes behave in a similar way?

Question: The effect of aggregate shape on concrete strength

Question: What are water-reducing admixtures?

Question: What are blended cements?

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

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

Question: Material Requirements for Mass Concrete

Question: Chloride concentration in soil and exposure classes

Question: The effect of aggregate strength on concrete strength

Question: Factors affecting cement properties

Question: Definition of “hot cement”

Question: What water-cementitious material ratio should be used for a particular job when strength require...

Question: The purpose of calcium sulfate (gypsum)

Question: Are pozzolans all alike?

Question: What are high-density aggregates?

Question: What is architectural concrete?

Question: Hardening of hydraulic cement

Question: What is fly ash?

Question: What is silica fume?

Question: Important requirements of a concrete aggregate

Question: The effect of aggregate on concrete durability

Question: What is an admixture?

Question: Will the use of fibers impact the air content of the concrete?

Question: Requirements for a successful concrete structure

Question: Aggregate classification by density

Question: The effect of surface texture and cleanness on concrete strength

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

Question: What is aggregate?

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

Question: Materials used to produce portland cement