Problem Adding New Concrete Walls To Existing Concrete Walls Bonding

The edges of the defective area should be chipped or cut straight and at right angles to the surface or slightly undercut to provide a key at the edge of the patch.

Problem adding new concrete walls to existing concrete walls bonding.

Let s start by assuming you are concerned that the old wall is failing and you want to support the house on the new reinforced concrete wall. When joining new concrete work to old concrete work the joint will always develop a crack and will be a point of expansion and contraction. Just as in the process described above after the bonder has become tacky apply a scratch coat and then apply the repair material. Saturated surface dry is a condition in which the concrete contains moisture that is equal to its potential absorption without the surface being wet or damp.

Quikrete concrete bonding adhesive no. 9902 permanently bonds new concrete plaster and stucco to existing concrete plaster and stucco. It must be ensured through proper surface preparation material choice and use and curing. Then apply the repair material.

After 24 hours remove the formwork and allow the concrete wall to cure. This usually takes only a few minutes. The cement within a concrete mix doesn t contain any natural bonding agents so when fresh concrete is added on top of an existing layer of concrete the two won t join together. Exceeds the performance requirements of astm c 1059 type i and ii.

That would require major framing work since you would need a new sill around the house the old framed walls if that is in fact what you have would not line up with the new wall etc. Existing concrete walls can be strengthened by retrofitting steel materials. Fresh concrete can then be poured into the formwork and left to dry. Once cured the new concrete will simply sit on top as a separate layer.

This method does add a bit of weight to the walls but it can also be done with minimal disruption to anyone living or working inside the building. Research has also shown that the moisture condition of the substrate affects the shear bond strength of bonded concrete. Over time this expansion and contraction especially if they occur at different rates due to the sections of concrete being exposed to different temperatures will work the sections apart and the crack will widen. When using a liquid bonding agent paint the bonder onto the existing concrete and allow it to dry until it is tacky.

Bonding fresh plastic concrete to old hardened concrete increases the strength of the composite material fresh patches concrete adjacent to construction joints and overlays all benefit from bonding to the hardened concrete substrate bond is not however guaranteed. All damaged loosened or unbonded portions of existing concrete should be removed by chipping hammers or other mechanical methods.