Each year since 1979, seminars on basics of concrete have been offered at the World of Concrete. At the end of each session, questions from the audience of contractors, suppliers, engineers and architects are answered by the seminar speakers. The questions dealt with in this article give an indication of what people want to know about concrete.

CONCRETING MATERIALS

The topics addressed in these questions are: Type I versus Type II cement; disadvantages of Type II cement; seawater as mixing water for concrete; liquid or solid calcium chloride; and alkali reactive aggregates.

CONCRETE CONSTRUCTION PRACTICES

The topics addressed in this set of questions are: latex-modified concrete; restarting the curing process; wire mesh at joints; and the effect of a vibrating screed on entrained air.

CONCRETE TROUBLESHOOTING

This set of questions covers the topics of: concrete turning white; replacement of lost air; getting rid of bleed water; concrete rejected because it wasn't discharged soon enough; and efflorescence problems.

CONCRETE TESTING PROCEDURES

This set of questions deals with: measuring yield and field-cured cylinders.