Question

Once water is added to a concrete mix at the mixing plant, what is the maximum time for delivery and discharge from truck?

1) 1 hour
2) 1 ½ hours
3) 2 hours
4) 2 ½ hours

Answer 1

The standard maximum time for concrete delivery and discharge from the truck after adding water is typically 1 1/2 to 2 hours, depending on various factors such as climate and additives in the mix.

Step-by-step explanation:

Once water is added to a concrete mix, the maximum time for delivery and discharge from the truck is typically around 90 minutes to 2 hours. However, this time can vary depending on specific standards and regulations in place, such as the American Concrete Institute (ACI) guidelines or the particular requirements of the construction project. Climate conditions and additives used in the mix can also affect this timeframe.

In practice, the maximum time is often a balance between the setting time of concrete and the need to ensure that it remains workable and able to fully compact and bond without developing cold joints. Extended delivery times may require the use of delaying admixtures to slow down the hydration process of the cement.

It's crucial for any concrete delivery to be appropriately planned to minimize the time between mixing and pouring, known as the "initial set", to ensure the integrity and strength of the final concrete structure.