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?

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