How to Install Armored Joints in Concrete Floors

What Is an Armored Joint in Concrete Flooring?

An armored joint is a specialized expansion joint system used in concrete flooring to accommodate thermal expansion and contraction. It is typically made of steel or high-strength materials and installed at slab joints to protect edges from damage.

Armored joints play a critical role in preventing cracking, chipping, and deformation in heavy-duty floors. Thanks to their high load-bearing capacity and wear resistance, they are widely used in industrial facilities, warehouses, and parking structures where forklift traffic and heavy loads are common.

Project Background (Case Study)

In a large-scale financial facility project, a high-precision concrete floor was required for a secure underground area with frequent heavy vehicle traffic.

The project demanded:

• Extremely high flatness tolerance (±2mm over 2m)
• Long-term durability of expansion joints
• Resistance to heavy loads and continuous traffic

To meet these requirements, an advanced armored joint system with load transfer capability was adopted to ensure both structural performance and surface quality.

Overview of the Armored Joint System

This project adopts an AFJ armored load transfer formwork expansion joint system for ultra-flat, heavy-duty, wear-resistant concrete floors.

The system consists of:

• Breakable plastic bolts
• Edge protection flat steel
• Anchor studs
• Free-movement sleeves
• Split-type load transfer plates
• Floor joint steel plates

It allows the concrete floor to be divided into sections in both longitudinal and transverse directions, enabling large-area segmented pouring.

At the joints, the load transfer formwork can move freely, which helps prevent cracking.

With this system, there is no need for traditional expansion joints or formwork removal, significantly improving construction efficiency and reducing overall costs.

Key Installation Techniques

To ensure the quality of the concrete floor, it is important to control the processing, transportation, and installation of the armored joint system.

At the same time, floor flatness must be carefully controlled during construction to avoid deviations after curing.

Processing, Transportation, and Installation

To avoid deformation during transportation, continuous steel bars are welded to anchor studs using CO₂ gas-shielded welding.

👉 This method:

• Improves overall straightness
• Reduces deformation caused by welding shrinkage

After the base slab is prepared, control lines are marked on the floor.The armored joint system is then positioned and adjusted according to these reference lines.

To ensure stability during installation, the system is fixed using:

• Adjustable A-frame supports – simple, reusable, and suitable for different joint specifications
• Multi-point rebar positioning system – ensures accurate alignment during installation

The positioning system uses triangular rebar supports fixed into the concrete, which help maintain precise positioning.

👉 Installation requirement:

• For each 3-meter joint section, at least 4 supports should be installed on one side

Before the second concrete pour, these supports must be removed or cut to:

• Allow free movement of the joint system
• Prevent cracking caused by restraint

Concrete Pouring and Curing

After the armored joint system is installed, concrete is poured for the floor slab.
The concrete surface should be level with the top of the steel edge protection.

During pouring, special attention must be given to vibration around key components, including:

• Load transfer plates
• Sleeves for movement

👉 Proper vibration ensures dense concrete and avoids voids or quality issues.

Conclusion

This project demonstrates the effective application of the armored joint system in high-precision, heavy-duty concrete flooring.

By combining straightness control techniques and a multi-point positioning system, common issues such as misalignment and insufficient fixation were successfully resolved.

The use of split-type load transfer plates allows the joint system to adapt to floor movement, reducing the risk of settlement and cracking.

In addition, the self-developed adjustable screed and elevation control tools significantly improved construction efficiency while ensuring high flatness accuracy.

As a result, the project achieved the required floor flatness, enhanced joint durability, and reduced construction time, delivering both technical and economic benefits.