Frequently Asked Questions

Technical Questions

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




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

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

Question: Can the importance of proper consistency for placing be overemphasized?

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

Question: Heat of hydration and the importance of controlling it

Question: Maximum temperature limits for hot-weather concreting

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

Question: How to Control Mass Concrete Temperature during Construction

Question: What is mass concrete?

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 concrete consolidated?

Question: Consolidation of concrete—required or not?

Question: Requirements for durable concrete

Question: The effect of pozzolans on water demand

Question: Requirements for storing and handling aggregate

Question: Why is the workability of concrete important?

Question: How is workability measured and specified?

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

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

Question: Can you have too much paste or mortar?

Question: What are the essential requirements of consistency?

Question: How is concrete placed?

Question: Why is consolidation needed?

Question: How should the concrete be consolidated to obtain a complete filling of the forms and around the reinforcement?

Question: Does over-vibration cause segregation and loss of air content?

Question: What is the importance of consolidation on strength?

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

Question: When can the finishing procedure be started?

Question: What is curing?

Question: What is meant by properly cured concrete?

Question: Is there any measure of the completeness or adequacy of curing?

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

Question: How does the temperature influence curing?

Question: What is the effect of freezing on concrete?

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

Question: Can the heat liberated by the hydrating cement be relied on to give protection during cold weather?

Question: When heated enclosures are used to protect freshly placed concrete, what precautions are necessary?

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

Question: Are any temperature limitations necessary in curing concrete in hot weather?

Question: When is steam curing used?

Question: How can the effectiveness of curing be measured?

Question: What is the importance of curing on strength?

Question: Does additional curing improve the properties of concrete in other ways than in strength?

Question: What is architectural concrete?

Question: Tolerances for floors supporting operable partitions

Question: Decorative concrete finishes

Question: Placement of welded wire reinforcement (WWR) in a slab-on-ground

Question: Tolerances for concrete slabs supporting steel tanks

Question: Standard on detailing of concrete reinforcement

Question: What test conditions affect the results of compressive strength tests of concrete?


Other Sources for Answers

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

Please enter this 5 digit unlock code on the web page.