Concrete is the basis we build upon, the foundation of a building. It is one of the things that most contributes to a successful project. If not completed correctly, it can have massive consequences for the entire project. If concrete is placed without consideration for weather, it can fail to meet strength and finish requirements. Incorrect placement can also lead to excessive cracks or spawling, which may require removal and replacement of entire sections of work.
For this article, we talked to two of our team members who have extensive experience with concrete placements, Project Manager Travis Magers and Quality Control Manager Robert Eblacas. They explained some of the guidelines for successful concrete placement and shared their experiences with nighttime concrete placements, which are sometimes necessary when weather or other factors are not conducive to a typical placement.
What are the guidelines for a successful concrete placement?
A detailed plan of operation for each concrete placement is vital to a successful project. It’s also important to have all necessary equipment and manpower set up and waiting prior to arrival of the concrete. Some of the steps Ross Group takes for a typical placement include:
Selecting the correct mix design for the type of project and getting it approved through the submittal process
Holding a pre-construction meeting with all stakeholders and relevant subcontractors prior to placement
Scheduling a timely delivery to the project site, as you only have 90 minutes to place concrete after it has been dispatched
Testing the concrete to ensure it meets all specified requirements
Putting safeguards in place to protect the finished concrete
Time and weather have a huge impact on concrete placement and the steps necessary to complete the process. Rain can introduce extra water to the concrete mix, which may decrease the strength or damage the finish. If temperatures are too cold, the concrete might fail to set up properly. (Ross Group works on a variety of Government projects and these generally require concrete to be placed only when temperatures are 40 degrees Fahrenheit and rising.) Alternatively, if temperatures are too hot, the concrete can cure too rapidly, creating problems with joints and finishes.
When and why is nighttime concrete placement necessary?
A nighttime placement may be necessary under two conditions. The first, and most common, condition is when daytime temperatures are too hot. Early morning or late evening placements during hot weather allow for placement without direct sunlight and at lower temperatures, which improves the team’s ability to control the cure and finish of the concrete. The second condition is when there is dense traffic at or around the project location, such as downtown in a large city. In this case, placing concrete at night allows for the necessary trucks and equipment to get onto the site more easily.
How is nighttime concrete placement accomplished? How is the process different from a daytime placement?
One thing that is significantly different for nighttime placements is that everything must be organized and prearranged the day before by preparing the site, setting up the testing lab, and setting up the necessary lights. The pump machine also has to be set up the day before, so it is ready for the nighttime placement.
Perhaps the biggest difference between nighttime and daytime placements, besides temperature, is the lack of light. This can be mitigated by placing light towers at various locations around the work area. Enough towers must be set up to provide the required light per OSHA regulations
Another difference that can become an obstacle is manpower and materials. Scheduling needs to be properly coordinated with the batch plant so that nighttime placements can be successfully accomplished. A chief concern with manpower is the potential for overwork. This can result from personnel working the days before and/or after a nighttime placement. Fatigue management is always an important consideration when placing concrete at night.
Having a solid foundation is key to getting a project off the ground and ensuring it progresses in the right direction. Concrete placement is critical to this process and it’s important that the construction team understands the conditions under which concrete can be placed and when adjustments need to be made. As Travis and Robert shared, nighttime placements are a great option in a variety of situations. To learn more, check out the American Concrete Institute’s page on concrete placement https://www.concrete.org/topicsinconcrete.