Technical Questions

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




Question: What nominal maximum sizes of aggregate are recommended?

Question: How can the surface or free water carried by the aggregates be determined?

Question: Requirements for storing and handling aggregate

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

Question: Popouts or popoffs?

Question: Advantages of low-density aggregate

Question: How can durable aggregates be ensured?

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

Question: The effect of aggregate strength on concrete strength

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

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

Question: Characteristics of aggregate affecting concrete strength

Question: What is aggregate?

Question: Why is combined aggregate grading used?

Question: What are high-density aggregates?

Question: Important requirements of a concrete aggregate

Question: The effect of aggregate on concrete durability

Question: The effect of aggregate shape on concrete strength

Question: The effect of aggregate characteristics on concrete shrinkage and permeability

Question: When water and aggregate are heated, are any limitations necessary?

Question: The effect of aggregate grading on concrete strength

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

Question: If the paste is ample in amount, but is too thin and watery to float the aggregate particles, what is the result?

Question: How is the resistance to alkali-aggregate reaction (AAR) determined?

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

Question: Curling, shrinkage, and w/cm

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

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

Question: What is D-cracking?

Question: Aggregate classification by density

Question: Size of test cylinder

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

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

Question: The basic approach used in the ACI mixture proportioning method

Question: Aggregate blending

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

Question: How can the adequacy of mixing be determined?

Question: How can segregation of the concrete between the mixer and its final point of placement be prevented?

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

Question: How to Control Mass Concrete Temperature during Construction

Question: Definition of low-density concrete

Question: Protecting concrete from cycles of freezing and thawing

Question: Improving the abrasion resistance of concrete

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

Question: Can you have too much paste or mortar?

Question: What is the purpose of finishing and texturing concrete surfaces?

Question: Are polymer concrete and polymer-modified concrete used in repairs?

Question: What tests are necessary or desirable in making a series of trial mixtures to arrive at a suitable mixture for a particular job?

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

Question: How is the air content of freshly mixed concrete determined?

Question: Using cube tests in lieu of cylinder tests

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

Question: Hardening of hydraulic cement

Question: Consistency, plastic consistency, and workability

Question: The effect of entrained air on the workability of concrete

Question: Factors governing the strength of concrete

Question: Air content common limits

Question: The effect of pozzolans on freezing and thawing resistance

Question: What is an admixture?

Question: Who selects the requirements for concrete for a project?

Question: The ultimate objective in proportioning concrete

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

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

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

Question: What factors affect the mixing time?

Question: What range in slump is recommended for various types of construction?

Question: How is concrete consolidated?

Question: Why is the slump test not an absolute measure of consistency or workability?

Question: Why are many non-destructive tests used as “estimators” of concrete strength?

Question: Mixture design and strength submittals

Question: Measurement of setting time

Question: Can tests be conducted by anyone?

Question: Design Properties of Lightweight Concrete


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