How to Build a Notch Wedge Joint
BY Jerod Willow
When trying to increase the life of the mat, notch wedge joints (NWJ) are a superior alternative to butt joints. Since it is not always possible to run hot echelon paving, contractors can use the overlap of a notch wedge joint to increase the density of the longitudinal joint thus increasing the life of what traditionally seems to be the first failure point in paving. For example, we see an average of a three points increase in joint density when building with our notch wedge device versus a butt joint.
There are two predominant types of notch wedge devices right now:
- devices that go inside the screed
- devices that are attached to the outside of the endgate
We prefer the efficiency of the on-and-off devices that attach outside the endgate, such as our Willow Notch Wedge device, so when referring to devices in this article, we will be referencing the ones pictured here. Simply put, the mechanic can attach a bracket to be left on the screed or use the simple bolts on the device that allow for in-field attachment and removal in a few minutes.
These devices are offered by Willow Designs, East Berlin, Pennsylvania. Jerod Willow, the proprietor, took the time to prepare this step-by-step guide for building a successful notch wedge joint for the 2024 Training Directory.
Depending on the climate and quality of the mix, there are also options to add heat and/or vibration compaction with devices. Additionally, many companies choose to also use a specialized pneumatic roller from Willow Designs that attaches via a hand twist bolt to the notch wedge device alleviating the need to roll the wedge portion with an additional machine.
This pneumatic roller adds compression to the vertical joint while reducing raveling and fracturing of aggregate at the wedge. When used in tandem with the pneumatic roller, we see joint densities increase by an average of four to seven points.
For the first-time use of the Willow notch wedge device and pneumatic roller, I provide a shift of support to the paving crews so that they can achieve the best numbers with the product the conditions will allow. Often a full shift is not necessary due to the ease of use, but once in a while the team takes advantage of all my experience and they dig into the weeds of best paving practices.
Here is the step-by-step process to build a notch wedge joint.
Step 1: Select your system of choice and affix it to the endgate.
Based on your paver’s screed type, a simple bracket can be bolted to the endgate that the device can then be attached to. The device could also be directly bolted to the endgate.
The pneumatic roller is attached with a T-bolt to a stud on the notch wedge device. The release agent container is filled and snaps into brackets on the mat side of the roller.
Step 2: Apply tack.
Some states are now requiring that a longitudinal joint sealant (LJS) or void reducing asphalt membrane (VRAM), such as the J-Band product from Asphalt Materials Inc., be applied along the centerline. Check with your state specifications.
Step 3: Pave the first pass.
This is the time to dial in the device according to the mix and specifications of the job.
The primary jack is used to lower the inside portion of the device’s screed for the depth of the vertical notch. Bear in mind that you need to add the compaction depth of the mix to the depth of the vertical notch. We try to set the notch of the device at 40% above the compacted mat thickness while also trying to accommodate the largest aggregate in the mix.
Here you see the primary jack and turnbuckle highlighted.
Once the depth is set, use the turnbuckle which adjusts the slope of the wedge/toe slope/outside portion of the device’s screed. Also, the toe of the slope on the wedge should not be less than a stone’s thickness, otherwise there could be segregation in the wedge mat. Most states specify a 12-inch width of wedge, but the Maine DOT is playing with a 6-inch wedge for lift thicknesses that are less than 2 inches.
- Some devices have vibratory options, and during this step, you would turn on the vibration to the setting of your choice.
- With cold weather climates and SMA mixes, the heated screed plate would be plugged in before paving and then shut off once the device is running hot mix.
If the pneumatic roller is being used, then this is also the time to generously add release agent to the roller via the attached spray tank and nozzle. Release agent needs to be maintained until the roller heats up and then less material is required. Adjust the turnbuckle on the mat side to adjust the lateral tracking to just overlap the vertical edge by 0.5 or 1 inch.
Step 4: Roll the first lane.
This we find is probably the number one improvement to be made in low joint density numbers for compaction of the first lane with an open wedge joint. The breakdown roller should be rolling as soon as it can fit behind the paver, compacting as hot as possible. The rolling allows for the roller to overhang the joint by 12-18 inches of drum over the wedge. It does not seem to matter if it is rolled first or last in the pattern. We always recommend using the extra pass (if there is one) in a pattern on the open joint. This applies to all steel drum rollers in the paving train.
We have found that running another method of compaction on the 12 inches of wedge is not necessary if the Willow pneumatic roller was used initially.
Step 5: Apply tack to the second lane.
Spray the wedge with a double application in addition to coating the second lane. If there are any voids in the mat of the notch wedge joint, the heavy tack coat application will fill these and actually increase your chances of achieving higher joint density numbers.
Step 6: Lay the second lane.
The paver lays the second pass against the vertical edge and overlaps the wedge. Be careful to match the joint at the proper elevation so as not to starve the joint for asphalt mix. Longitudinal joints that are matched low will ultimately produce low joint density numbers because the compaction train will bridge on the cold lane of pavement being matched. We often see screed operators do this because they have been taught to build an “invisible joint” that rolls in clean with less distinction. We now know this is a failed joint waiting to happen. We can check good joint elevation by depth-checking proper loose depth thickness of the pavement at the matched joint 14 inches into the hot mat. The wedge will then heat back up and become the second lane as shown by joint density cores.
Cores should be centered over top of the wedge, which is roughly 3 inches from the seam. That provides the best representation of the joint.
Step 7: Roll the second lane.
Based on project conditions, for the breakdown, stay 12 to 14 inches off the matched joint with the first pass toward the paver. For the second pass, steer the roller to where the drum has a 12- to 18-inch overhang onto the cold lane. Not all job conditions allow for a great overhang, but the best results from our testing show that an 18-inch overhang puts the weight of the roller directly over the joint. This compacts the material into the joint, stabilizing the mix over the wedge. Then you continue rolling the mat as normal. We always recommend if there is an extra pass in the pattern to put it over the joint.
If specified density is not being achieved with this equipment, we need to dig deeper into good paving practices.
Jerod Willow is the proprietor of Willow Designs, East Berlin, Pennsylvania, and has over 20 years experience in the asphalt and paving industry. He saw a chance to improve asphalt life by developing user-friendly devices to meet the needs of contractors. He also uses this knowledge to teach paving classes and does onsite training as well as consulting for companies looking to improve their paving practices. For more information, contact him at (717) 919-9828.