Vibrator Placement
A concrete vibrator consolidates and adds paste to the concrete. Finding the right placement for your vibrator can be tricky, involving a wide scope of factors to consider.
Vibrator placement how to video
In this video we will show common vibrator placements on several different styles of molds.
You may find that slightly different positioning works better for you. Vibrator placement and intensity can be affected by many factors, such as mix design, slump, draft of the mold, and ground speed.
For information on installing vibrators, please see our video on mounting vibrators in a curb and gutter mold.
Let’s start with what a concrete vibrator does: Properly placed, the vibrators will help to consolidate the concrete and add paste for a better finish. Over vibration can segregate the materials, lower the entrained air content, and cause a poor finish.
The maximum area of vibration, or area of influence, is generally 18 inches wide, over the last 2 inches of the vibrator. We recommend having vibrators 2 inches into the finished product to make best use of this maximum vibration zone.
Curb and gutter is our first application. Install one vibrator in the head of the curb. A second vibrator is placed 3 to 6 inches from the toe of the mold. If the mold is more than 30 inches wide, add a 3rd vibrator spaced midway between the two existing vibrators.
Rollover curb is very similar to curb and gutter. Place a vibrator 3 to 6 inches from the backside of the mold. Add another vibrator 3 to 6 inches from the toe. Again, add a third vibrator if your mold is more than 30 inches wide.
Header curb, also known as stand up, or barrier curb can be handled 2 different ways. We first look at vibrators mounted inline, or in tandem. The vibrator closest to the back of the mold is mounted 2 inches deep and centered in the head of the curb. The second vibrator is mounted in front of the first and should be 8 to 10 inches lower. This vibrator will consolidate the concrete at the base of the curb.
You can also mount the vibrators side by side. The first vibrator goes in the center of the head, 2 inches down as before. But the second vibrator is mounted beside, not in front of the first. The second vibrator must angle down to get below the first. It is positioned low to consolidate the concrete at the base of the curb. Great care must be taken to ensure that the vibrators will not touch each other, or any part of the mold.
Sidewalk, median, and v ditch molds are very similar. Each side of the mold needs a vibrator 3 to 6 inches from the edge, 2 inches deep. The other vibrators are equally spaced, no more than 18 inches apart, also 2 inches deep.
Barrier and parapet molds are similar to header curb, just much larger. 2 vibrators are mounted on the front side of the hopper. These vibrators are for compacting the base of the wall. They should be 8 to 10 inches from the ground, and on either side. Depending on the height of the wall, several more could be placed on the sides. These should be midway down and mounted in the back of the hopper. A vibrator is needed up high to fill the mold and give a slick finish on top. This one will be the traditional 2 inches into the finished wall. These vibrators will be mounted in the back of the hopper.
Our last example is a barrier or parapet poured over a steel cage. The positioning will be similar to a standard barrier. 2 down low, mounted to the front of the hopper. And the rest attached to the back of the hopper. Great care must be taken to make sure that no vibrators touch the mold shell or the rebar cage. This would cause unwanted vibrations and could collapse the wall.
There are an infinite number of mold designs in use today. But most will have traits in common with the molds discussed in this video.