Poured concrete can have problems that greatly affect the overall quality of the pour, such as bug holes, honey combing, and cold joints. Problems that commonly occur when using shoring equipment are mitigated by use of a concrete vibrator, which consolidates concrete and refines the pouring process. Here are some tips for perfecting poured concrete with vibration.
Use Good Practices and Planning Before Vibration
All the vibration in the world won’t make a difference if the concrete isn’t first handled and poured well. The first step is to make sure that you have backup systems in place for every part of the job, including extra vibrators and other tools. Plan out the pour to avoid hiccups during the job. Mix of concrete should be correct. If it is not, use super plasticizer or water reducer to increase slump.
When placing concrete, keep in mind that rebar tends to obstruct the pour, creating air pockets and sifting out aggregate from mortar. Use elephant trunks or placing equipment to reduce segregation and move poured concrete through obstructions.
Concrete Vibrator Tips
Vertical Motion Only
Concrete vibrators should only be moved vertically. If they are moved from side to side, it can create uneven mixtures of aggregate and concrete. Horizontal motion also tends to tangle the vibrator in the rebar. Flow lines and discoloration can also occur.
Technique for Success
The vibrator should be let down slowly into poured concrete, allowing the weight of the vibrator to carry it to the bottom of the pour. Let it sit at the bottom for 5 to 15 seconds, then allow 15 seconds for pulling it back out.
Vibrators work different amounts of the poured concrete depending on the strength of the vibrator, which is measured in the circle of concrete affected by the vibration. These circles must overlap so that all the concrete is vibrated. Space vibrator insertions close enough together that no concrete is missed.
Vibrators work well, but extra care has to be taken when using them near formwork. The very quality that works so well to consolidate concrete will cause a lot of problems when the vibrator comes in contact with the forms. Vibrators can damage forms, which is mirrored in the surface of hardened concrete. The damage becomes obvious when forms are removed. Take care to not get close to the surfaces of the formwork.
Under-vibration and over-vibration are both problems, but the most common is under-vibration. When in doubt, always vibrate a bit more. This will reduce the problem of bug holes and honeycombing.
Reduce Cold Joints by Vibrating
Concrete sets up in about an hour, and a cold joint is formed between the fresh concrete and the more hardened concrete, weakening the overall structure. Vibration every 15 minutes can prevent concrete from setting as quickly so that concrete bonds together until fresh concrete can be obtained to continue the pour.
The Right Equipment
When used with the correct vibration techniques, you can successfully form a strong structure that’s adequate for the loads it needs to bear. The other part of the equation is good equipment. Forming America can provide the quality shoring and forming equipment that you need for your next job. We offer sales and rentals, and the equipment is delivered directly to your jobsite, saving you time.
Forming America is here with solutions for your forming needs. Contact us today.