The maximum elapsed time allowed between obtaining the final portion of the composite sample and beginning the tests for slump, temperature, and air content is _____ minutes.

The maximum elapsed time allowed between obtaining the final portion of the composite sample and beginning the tests for slump, temperature, and air content is _____ minutes.

• A. 3 minutes
• B. 10 minutes
• C. 5 minutes
• D. 7 minutes

Answer: (C)

Fresh concrete tests must be started quickly after the final portion is added to the composite sample. This is because the concrete begins to hydrate and its properties can change rapidly as time passes, affecting workability, air voids, and temperature. If testing is delayed, slump can change as the mix stiffens, air content can shift due to segregation or entrained air loss, and temperature can drift due to ongoing hydration and ambient conditions. To capture the true state of the batch, a strict maximum window is set for starting slump, temperature, and air-content tests, so the results reflect the concrete’s fresh properties. The standard window is five minutes, making this the best answer.

Fresh concrete tests must be started quickly after the final portion is added to the composite sample. This is because the concrete begins to hydrate and its properties can change rapidly as time passes, affecting workability, air voids, and temperature. If testing is delayed, slump can change as the mix stiffens, air content can shift due to segregation or entrained air loss, and temperature can drift due to ongoing hydration and ambient conditions. To capture the true state of the batch, a strict maximum window is set for starting slump, temperature, and air-content tests, so the results reflect the concrete’s fresh properties. The standard window is five minutes, making this the best answer.