INTRODUCTION TO EXPANSION JOINTS
Expansion Joint Wear and Damage
An expansion joint is commonly located on structures such as bridges, highways and sidewalks. An expansion joint is a mid-structure separation designed to absorb vibration, join objects, or allow movement. In structures, expansion joints can help absorb the expansion and contraction of concrete slabs as a result of temperature changes. Without expansion joints, the concrete can crack or distort. However, expansion joints on their own are susceptible to failure. A major issue is incompressible materials that lock the joints and create stresses that may cause concrete spalling or shattering. As a result, seals are frequently installed in expansion joints to prevent incompressible debris from entering the joint. Two types of common seals are strip seals and compression seals.
Conventional Expansion Joint Seals
Strip seals are flexible neoprene membranes adhered to the joint walls. They adhere well and prevent water ingress, but the seals can tear and disjoin under traffic if incompressible debris settles on top. Compression seals are neoprene or cellular seals in the form of a series of web that provide outward pressure against joint walls to hold the seal in place. They are ready for use out of manufacturing, meaning no mixing or curing is necessary. The seals need to be correctly sized to maintain the pressure against the walls, but the seal can still disjoin with the loss of elasticity overtime.
Conventional Failure Reasons
Seals commonly fail due to adhesion loss and cohesion loss. Adhesion loss is evident when detachment of the seal from joint walls occurs. Adhesion loss is the loss of bond between the sealant and joint walls. Cohesion loss is evident when a tear on or in the seal occurs. Cohesion loss is the loss of internal bond in the sealant.
Conventional expansion joint seals have their own individual disadvantages and common failures. Belzona provides polyurethane sealants that protect expansion joints from incompressible debris while offering advantageous mechanical properties including high movement capability, high elastic recovery, and high abrasion resistance. In addition, Belzona polyurethane sealants contain low odors and adhere well to a range of substrates.
Failing Expansion Joint Repair Drawing
In our previous blog post “In Action: Repairing Failed Expansion Joints in Healthcare”, we introduced an expansion joint repair method called “Smooth Ride”, mostly applicable to hospitals. In this blog post, we demonstrate an expansion joint repair that can apply to any industry and any type of concrete joint.
Video: How to Fix a Failing Expansion Joint with Belzona
For this repair, we used:
- Belzona 4111 (Magma-Quartz) and a wooden batten to reform the nosings of the joint
- Belzona 2221 (MP Fluid Elastomer) and a backer road to create a new joint sealant
- Belzona 5231 (SG Laminate) to provide protection of the expansion joint and an aesthetic look
Additionally, we utilized Belzona 9111 (Cleaner/Degreaser) to clean of the substrate, Belzona 9411 (Release Agent) to be applied to the wooden batten, a handheld grinder and a pole sander to prepare the substrate, and a mixer for preparing Belzona 4111.