Dowel Bar

Dowel bar is used to facilitate load transmission in the building of jointed concrete pavements, which is important for extended performance.

It is a small circular, smooth steel rod that is used to make a connection point between slabs while allowing for horizontal joint movement.

These bars are primarily utilized in jointed plain concrete pavement (JPCP) to support the increased stress and load caused by a moving vehicle.

In this article you’ll learn:

• What is Dowel Bar?
• Purpose of Dowel Bar.
• Methods of Dowel Bar.
• Merits and Demerits of Dowel Bar.
• Lots more.

So, if you’re ready to go with Dowel bar this article is for you.

Let’s get started!

What is a Dowel Bar?

Dowel bars are the steel left section used to unite any members such as slabs, columns, and staircases, among others, to convey the load-induced in concrete members.

Dowels bars are steel, rod bar, or reinforcement that are left as per steel size.

Dowel bars are circular steel bars that are inserted across horizontal joints of concrete components. They operate as a weight transmission factor between concrete joints while also allowing for movement.

 It may be installed where there is movement on specially built longitudinal joints.

Purpose of Dowel Bar:

• The dowel bar’s purpose is to improve joint function. Dowel bars are preserved in order to distribute load across concrete joints.
• It’s used to keep corners from breaking. Dowel bars are used to prevent joint faulting.
•  It is offered with the intention of transmitting the weight from one member to another, such as one slab to the next.
• Usually, we left 50D in length by increasing the bar’s diameter by 50. (50 x 16)
• When the diameter of the steel is 16, the length of the dowels and rebars is determined, i.e. 800mm.

Types of Dowel Bars:

Dowel Bar made of Stainless Steel:

Stainless steel dowel bars are commonly made of simple circular material.

They offer a long-lasting, corrosion-resistant solution for concrete or other structural connections.

There is an appropriate dowel bar’s for most purposes since they are available in a variety of diameters, material grades, and strengths.

Concrete slab dowel bars are used to transmit weight from one slab to another while allowing for axial thermal expansion along the dowel’s axis.

Dowel Bar with Epoxy Coating:

The dowel bar should be coated with an epoxy coating material selected from the official epoxy coating of steel.

Once cured, the coating thickness must be at least 7 millilitres. Bowling or other deformation controls on dowel bars are not permitted to slide into the concrete.

The tip must be trimmed. The chips in the cutting process must be removed from the coated bar.

Dowel bars should be supplied by the coating process in the list of approved certified reinforcing bars epoxy coaters and by selecting bars manufactured by the supplier.

 When dowel strips are shipped to the project site, they must be accompanied by the types of certificates provided.

Methods of Evaluating Dowel Bar Alignment:

Destructive method:

Joint chip-out and coring are the principal destructive methods of dowel bar alignment checking.

A jackhammer is used to expose the embedded dowel bars when chipping away a joint.

Hand measurements may then be taken of the locations of each dowel bar in a joint, such as rotation and translation. Coring might also be used to confirm bar alignment.

A single core gives minimum information, usually only bar depth.

 Yet, by coring at the expected position of both ends of the bar, a larger degree of detail, such as an approximation of the degree of rotation, might be acquired.

 Coring, on the other hand, only provides a sample of bar alignment at any particular joint unless conducted thoroughly. These procedures are time-consuming and rather costly.

Ground Penetrating Radar:

GPR systems function by firing electromagnetic radiation pulses into the soil and detecting the energy reflected on the surfaces.

The GPR signal responds to changes in the electrical characteristics of subsurface materials (such as dielectric constant and conductivity) as a result of substance type and moisture content.

Dowel bars are depicted as hyperbola curves. Missouri DOT (MoDOT 2003) proved that GPR may be used to properly check dowel bar alignment.

 Vertical alignment is precise to within 3 mm, while lateral dowel position is accurate to within 10 mm.

However, this method of determining dowel alignment is vulnerable to concrete’s dielectric constant, which fluctuates with moisture content, temperature, and antenna frequency, among other considerations.

MIT-SCAN:

While the significance of appropriate dowel alignment is well acknowledged.

The ability to adequately monitor the placement accuracy of dowel bars has been hampered by a lack of practical techniques for assessing the position and orientation of dowel bars buried in concrete.

While the equipment was designed to scan dowel, bars inserted with a dowel bar inserter (DBI), it can also scan bars inserted in dowel bins with high accuracy if the basket’s transport tie wires are disconnected.

Merits of Dowel Bar:

1. The necessary horizontal movement and dowel bars deflect the fracture of the concrete components.
2. The dowel bar is used to simply expand the structure. To introduce the steel for structural expansion, little drilling is necessary.
3. It improves the joint performance of structural members.
4. It boosts the project’s initial cost while lowering the life cycle cost.
5. Dowel bars extend the life of the primary structural part.
6. The usage enhances the weight carrying capability of the slab.
7. It reduces deflection and stress.

Demerits of Dowel Bar:

1. A problem occurred during installation.
2. Inadequately compacted concrete around dowel bars.

Also read: Concrete Joints | Crank Bars | Concrete Joint filler | Cantilever Beam

Conclusion:

Dowel Bar alignment is an essential measurement tool for concrete pavements.

Non-destructive measurement advancements have enabled extensive examination of the in-situ dowel bar’s location, which was previously impossible.

Concrete paving requirements have been revised to balance quality and buildability thanks to improved alignment information.

Many organisations are checking dowel bar alignment continuously to verify that it is in line with contract criteria and that optimal long-term pavement performance may be obtained.