Yes, you can pour fresh concrete over existing concrete. As long as your concrete is in mint condition, this task is doable. If you decide to pour a new mixture over an old slab, be sure it is at least 2 inches thick.
Does concrete stick to concrete? If you pour a new layer over concrete right on top of the old one, you won't get proper adhesion. You must properly prepare your concrete slab and then apply a chemical bonding agent on top of it so your new concrete adheres properly.
Bonding restrictions: Concrete is composed of sand and aggregates held together with cement. Since cement lacks any natural bonding agents, newly-poured concrete won't naturally bond to the existing slab. You'll need to either use a bonding agent to adhere the two layers together or use an unbonded overlay method.
Brent Anderson responds: There are many ways to support a garage slab next to a basement wall. The best approach is to provide compacted backfill to 95% Proctor density from the footing to the sub-base (see "Soil Compaction Basics," 3/94).
However, concrete does indeed expand when it gets hot or when the moisture content changes.
Concrete is usually dry enough after 24 to 48 hours to walk on. For concrete to dry and reach its full strength, it typically takes about 28 days per inch of slab thickness. Once conditions are conducive for the concrete to cure at 85-90% relative humidity.
All concrete will shrink slightly as it dries and, when it's set, will expand or contract depending on the ambient temperature. To prevent cracks from forming, concrete expansion joints should be incorporated to allow for movement, particularly in slabs with a surface area exceeding 6m2.
First, the gap is cleaned of any debris. Then, if the gap is large enough, a backer rod is added to support the caulk. If the gap is smaller, a backer rod is unnecessary and can be filled only using a polymer caulk.
You can do this by regrading your yard, installing a drain tile system, cleaning your gutters regularly, using downspout extensions, installing an underground downspout, keeping water-hungry plants away from the foundation, installing a French drain in your yard, not using edging around landscaping, and keeping around ...
You can purchase a roll of welded wire mesh at a home improvement store, then simply spread it out in a single layer over the old concrete. Press it down so it is flat and level before you add the new concrete. The new concrete you pour binds to the mesh.
QUIKRETE® Concrete Bonding Adhesive (No. 9902) permanently bonds new concrete, plaster, and stucco to existing concrete, plaster, and stucco. Eliminates the need for roughing the surface before the application. Exceeds the performance requirements of ASTM C 1059 Type I and II.
A concrete slab in direct contact with the ground should be at least 3 ½” thick, but the minimum thickness is only two inches when adding an overlay.
Blinding is a non-structural concrete to form a level and more stable surface on which further works can be more readily undertaken and is typically of 50 to 100mm depth.
Concrete doesn't stick to very much at all. First of all, wet concrete will not bond to dry concrete, hence the need for a bonding agent. It also doesn't adhere to paint, as paint is another material that is often made without any bonding agents. It also won't adhere to mortar and glue has absolutely no effect on it.
Concrete should be placed into its final position as soon as practicable. Extended delays in placing can lead to a significant loss of consistence with time making it impossible to place with satisfactory compaction.
Install a steel or fiber mesh: A layer of steel or fiber mesh can be added to the surface of the existing slab and embedded into a fresh layer of concrete to provide additional reinforcement.
Installing a concrete walkway around your house is an excellent way to protect the foundation.
One particularly effective method is using rocks to divert water. Doing so around a house's foundation helps prevent water from gathering, ultimately ensuring minimal risk of basement flooding.
To ensure proper curing, there are several key things to ensure optimal results. Spray: To maintain the proper moisture levels, concrete should be sprayed with water frequently. This is known as moist-curing. Most specialists recommend watering the slab 5 to 10 times per day for the first seven days.
Large Gaps and Expansion Joints (Over 1/4″)
All sections should be measured before the filling process. Materials for large concrete gaps and expansion joints include: Non-Sag Caulk: Thick, easy-to-control caulk ideal for larger areas. It requires smoothing but stays in place and works well with a backer rod.
In most cases, separation of the porch from the main house is caused by slope failure which is triggered by either slow movement on the hillside or movement of the retainer walls as the soil behind it continues to slide. In the case of retainer partition movement, movements can be sudden or gradual.
A flexible, lightweight, closed cell, cross-linked, polyethylene foam expansion joint and space filler. In concrete and brickwork Abelflex has excellent recovery properties.
Thickness of the concrete: Thicker layers of concrete can take longer to cure than thinner layers. Weather conditions: Wind, rain, and other weather conditions can affect the curing time and quality of the concrete.
When hydration – a chemical reaction between cement and water – takes place, concrete hardens and therefore becomes stronger. If too much rain falls into the concrete mix – or if it is laid onto wet surfaces or trenches – this will affect the mix, resulting in weak concrete.
Guidance from the American Concrete Institute (ACI PRC-224.3-95: Joints in Concrete Construction) says that “the expansion of concrete slabs on grade is generally less than the initial shrinkage, and provision for expansion is seldom required.” Regarding the regular use of expansion joints, the guide also states “ ...