Technical Questions

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

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

Question: Consolidation of concrete—required or not?

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

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

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

Question: Mixture design and strength submittals

Question: What is the basis of proportioning to ensure concrete of the desired weather resistance?

Question: The effect of aggregate shape on concrete strength

Question: Air tests for non-air-entrained concrete

Question: The effect of aggregate grading on concrete strength

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

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

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

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

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

Question: The ultimate objective in proportioning concrete

Question: Why is the workability of concrete important?

Question: How is workability measured and specified?

Question: Air content common limits

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

Question: Why is combined aggregate grading used?

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

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

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

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

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

Question: Can you use any source of water as mixing water?

Question: Aggregate blending

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

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

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

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