1 An agitator truck transported ready mixed concrete to the

(1) An agitator truck transported ready mixed concrete to the jobsite. Due to delays on the way it took almost one hour to deliver concrete. During that time, the agitator truck drum had made 250 revolutions. Even though the initial setting did not occur, it was found that the concrete mix was stiffened. The truck operator asked your permission to add water to the mix and turn the drum 35 turns at the mixing speed. Assume that adding water do not violate the water- cement ratio requirements. As an engineer, would you allow the truck operator to add water and remix concrete? Explain reasons for your judgment using ASTM C94 requirements? Make sure to state the applicable ASTM C94 section numbers.

Solution

Yes, i will allow him to add water.

From ASTM C94 it is clear that concrete should be placed within one and half hour or 300 revolutions is reached, which ever comes first. It is clearly said that additional water can be added to meet the requirements and revolved for more than 30 revolutions at mixing speed.

It is mentioned in ASTM C94 -11.7