What are the methods of joining old and new concrete?

Author: Erich Satterfield  |  Last update: Thursday, October 9, 2025

There are two basic methods for bonding a portland cement based product to existing concrete: 1) mechanically and 2) chemically. Mechanical bonding: Let's discuss the mechanical method first since it is really used in both approaches. The most effective way to ensure a really good bond is with a scratch coat.

How to connect old concrete with new concrete?

  • Clean and roughen the existing concrete surface to be bonded to by the new concrete.
  • Either you make a slurry of cement, water and fine sand and paint the existing concrete or you use a commercial bonding agent and paint the surface to be bonded immediately prior to placing the new concrete.

What is the joint between old concrete and new concrete?

Expansion joints are put in place before the concrete is poured. Expansion joints are used to allow the slab to move and not put stress on whatever it abuts. These joint are placed where a slab meets a building, where a slab meets another slab, and where a pool deck meets the coping.

Is there concrete mix that will adhere to existing concrete?

QUIKRETE® Concrete Bonding Adhesive (No. 9902) permanently bonds new concrete, plaster, and stucco to existing concrete, plaster, and stucco.

Which admixture is used for bonding between the old and new surfaces of concrete?

Bonding admixtures are sometimes used to facilitate bonding new or fresh concrete with old or set concrete. These may include the addition of compounds such as acrylics, polyvinyl chlorides, acetates and butadiene-styrene co-polymers.

Joining old and new concrete | Old concrete ko new concrete se join kaise kare

What is the method of joining old and new concrete?

The procedure to join old concrete and new concrete involves cleaning the surface, applying a bonding agent, pouring new concrete, and finishing it. Common materials for filling joints include silicone sealant and polyurethane sealant.

What is the bonding agent between old and new concrete?

There are different types of bonding agents available, but the most common are latex-based or epoxy-based. Simply apply the bonding agent to the prepared surface with a brush or roller, making sure to cover all areas where the new concrete will be placed.

Will Quikrete bond to existing concrete?

Quikrete 1 Qt. Concrete Bonding Adhesive permanently bonds existing concrete, plaster and stucco to new concrete, plaster and stucco.

Can you pour new concrete up against old concrete?

You can pour concrete on top of an existing slab as long as it's still in reasonably good condition and structurally sound. This means the concrete should be free of cracks, buckling, and breaks. If you notice any small cracks or minor issues, it's in your best interest to repair them before you pour the new concrete.

What is the bonding agent between old and new concrete Sika?

Sika® Hibond is a structural bonding agent applied between old and new concrete surfaces during casting of roof slabs, retaining walls, water tanks, columns, ex- tension of balconies, etc. It is also suitable for use as a structural bonding agent for steel and iron.

What are the 4 types of concrete joints?

Here are the different concrete joint types that you can install :
  • Concrete Construction Joints. Construction joints are normally installed in concrete slabs to figure out the extent of the individual placements. ...
  • Expansion Joints. ...
  • Contraction Joints. ...
  • Isolation Joints. ...
  • Decorative Concrete Joints.

Do I need an expansion joint between old and new 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 “ ...

What is the adhesive between old and new concrete?

Bonding Fresh Concrete to Existing Concrete Surfaces

Overlays or patching materials of new Portland Cement Concrete (PCC), terrazzo, mortar, grout and extruded curb based on Type I through Type V cements or White Cement may be structurally bonded with liquid epoxy adhesives to existing concrete surfaces.

Should you pin new concrete to old concrete?

Any time one is to attach new concrete to old concrete, it is likely for cracks to form and the sections will begin to separate. One way to help prevent that when attaching them is to use rebar to pin them together.

What is an expansion joint in concrete?

What is a concrete expansion joint? A concrete expansion joint – or control joint – is a gap which allows the concrete to expand and contract as/when the temperature changes. It forms a break between the concrete and other parts of a structure to allow movement without causing stress, which can lead to cracking.

What is an SBR bonding agent?

Construction Chemicals SBR is a white styrene butadiene co-polymer used to improve the properties of cement renders, screeds and mortars. It is also used in conjunction with Construction Chemicals Tanking Slurry as a priming coat or tight render basecoat.

How to join old concrete to new concrete?

Here's our five-step guide to bonding fresh concrete to an existing layer.
  1. Loosen Old Concrete. Before you even begin to think about pouring a new layer of concrete over the top, you have to start preparing the existing layer. ...
  2. Dust the Surface. ...
  3. Mix the Bonding Agent. ...
  4. Apply the Bonding Agent. ...
  5. Apply the New Cement.

Can you put Quikrete on top of concrete?

Use QUIKRETE® Sand Mix to resurface damaged concrete to depths up to 2". For patches less than 1" thick, replace part of the mixing water with QUIKRETE® Concrete Acrylic Fortifier.

How to make new concrete match old concrete?

How do you color match new and old concrete?
  1. Concrete stains. Acid or water-based stains can be used on new and old concrete to help achieve better color uniformity. ...
  2. Integral color. You can also color the new concrete before pouring it. ...
  3. Tinted sealers. ...
  4. Concrete overlays.

Will new cement stick to old 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. Condition-affected life span: Properly installed concrete can last for over 50 years.

Can two pieces of concrete be glued together?

Several types of adhesive can be employed to repair concrete. Concrete adhesives come in different formulas tailored to the type of material you're bonding. Options are available for both small home fixes and larger, more advanced jobs.

What is the best concrete bonding agent for concrete?

To help avoid an unfortunate scenario, use the best concrete bonding agent. Whether mixing the agent with a slurry or using an agent to bond two concrete surfaces together, a high-quality product can get the job done. Our pick as the best overall concrete bonding agent is the Quikrete Concrete Crack Seal.

What chemical is used to join old and new concrete?

Unibond (SBR) is a modified styrene-butadiene liquid emulsion that works as a ready-to-use bonding agent for repairing spalled concrete floors, columns, beams, and slabs. Its bonding capabilities also work well when bonding old concrete and mortar to new layers of concrete and mortar.

Can you pour new concrete over old concrete?

You can add a layer of concrete over an existing feature as long as you follow a few best practices to ensure the overlay concrete will adhere to the existing material properly. However, if the concrete structure has signs of damage, it's best to remove or repair it.

What is bonded concrete overlay?

Bonded concrete overlays are constructed using conventional concrete paving practices and procedures. Bonded together, the overlay and the existing pavement perform as one monolithic pavement, with the existing pavement continuing to carry a significant portion of the load.

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