The air voids are caused by air trapped between the mold surface and the concrete. They generally appear in low slump concrete and can be found underneath irregular (non-spherical) shaped pieces of crushed aggregate. This is a result of having too little mortar to fill the spaces around the aggregate.
What causes void in concrete?
The most common causes for surface voids are entrapped air, the improper use of release agents or excess water within the concrete mix. Air can create blowholes and air bubbles in the concrete when air becomes trapped within the concrete mix.
How do you get rid of pinholes in concrete?
During placement, minimize the vertical distance between the concrete discharge point and the form to minimize the free-fall distance. Having too much free-fall distance during concrete placement can increase the amount of air to be entrapped in the concrete.
How do you fix air bubbles in concrete?
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What causes small holes in concrete?
Problem:Small pop outs or holes that occur on concrete slabs are often the result of lignite or shale carbons that were in the sand when the concrete was mixed. The lignite or shale particles are lightweight and float near the surface of the slab when the concrete is installed and troweled.
How do you tell if there is a void under concrete?
To detect voids under concrete, mudjacking contractors use a high-frequency, ground penetrating radar system. The GPR equipment sends a radio pulse down into the ground. When the transmission reaches an anomaly in the soil, a reflected signal is sent to the receiver.
How do you fill a concrete void?
Mudjacking. A type of sand-cement slurry (called “mud” in the industry) can be used to fill voids under concrete slabs. This mixture of sand, cement, and water is pumped through holes drilled in a slab foundation to fill voids underneath.
Can pitted concrete be repaired?
Once the surface begins to pit, filling the divots with concrete is usually a temporary fix that loosens over time. You can fill pits with a bonding concrete repair material, which is similar to caulk. Restoring the porch to a more original appearance requires dressing it with a special resurfacing concrete mixture.
What is concrete pitting?
Concrete pitting is when the surface of a concrete structure begins to deteriorate. It’s defined by a cluster of small holes that appear on the surface of the concrete. It’s an extremely common problem in construction that occurs because of a problem with the way the concrete was produced.
What causes concrete Popouts?
Popoffs can be a result of a poor quality concrete mixture, improper finishing, or inadequate curing practices that result in a poor bond between mortar and coarse aggregate particles. Popoffs are typically caused by pressure buildup associated with freezing of moisture in the mortar above the aggregate.
How can we prevent voids in concrete?
Use aggregate that is more uniform in shape. Irregular shaped pieces of aggregate tend to make the concrete less fluid. Techniques used during vibration can eliminate most surface voids. Vibrating both the outside and inside of your mold will draw most air and water bubbles away from the surface of the concrete.
What is the best fill under concrete?
Because concrete is a very porous material, it will absorb any moisture that it contacts. This can cause pooling. Without crushed stone, pooling water will settle under it and erode your slab. Adding a layer of crushed stone will add proper drainage, as well as create a barrier between your slab and the ground.
How do you fix a hollow concrete floor?
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Why does my concrete floor sound hollow?
Hollow sounds indicate the top surface of the floor has separated from the underlying concrete. “Sounding” by either tapping with a hammer or dragging a heavy chain and listening to the resulting sound are the easiest and primary means to detect and map delaminated floors.
How do you fill large gaps in concrete?
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Does concrete bonding agent work?
The use of a bonding agent helps the different concrete layers to behave like a single unit, thus increasing the strength and performance of the structure. The bonding agent is applied over the existing surface of the concrete so that the new layer of fresh concrete successfully adheres to the old layer.
Can you pour a thin layer of concrete over existing concrete?
Yes, you can put new concrete over old concrete providing there are no issues such as significant cracks of frost heaves with your existing concrete. A new layer of concrete should be about two inches to ensure an even, strong coverage.
Can new concrete bond to old concrete?
You can add new concrete to an existing concrete slab if the old concrete is in good condition. You will need to thoroughly clean the old concrete surface and use a suitable concrete bonding agent before pouring the new concrete to satisfy all structural requirements.
