Cationic Emulsions are made up of three major classifications of emulsion grades: rapid-setting, medium-setting, and slow-setting. The terms “rapid,” “medium,” and “slow” relate to the amount of time it takes for the emulsion to cure and the amount of mixing that can be performed before the emulsion breaks. Emulsions that allow for the longest mixing times generally take the longest to cure, while emulsions that allow for very little mixing time are those that set and cure most rapidly.

Chemical surface-active agents, serving as emulsifiers, are classified by the electrochemical charge that is attained when they dissociate in a water solution. In the case of cationic emulsions, the chemical charge is positive. The chemical type and quantity of surface-active agents used in the manufacturing process governs the properties of the emulsion and in what applications the resulting asphalt emulsion can be used.

As many people know, Asphalt Materials, Inc. is made up of a large family of companies. One of these companies, Bituminous Material and Supply, with plant locations in Tama and Des Moines, Iowa, was approached by Denco Construction regarding an interest in using scrub seal in Iowa. This is an emulsion seal that is not often seen in Iowa. A scrub seal is an application that is very similar to a chip seal treatment. The only difference is that the asphalt distributor pulls a broom sled that houses a series of brooms placed at different angles. These brooms guide or “scrub” the emulsion into cracks to help ensure the road’s surface is sealed.

Testing

The scrub seal is a process by which asphalt emulsion is applied to a pavement surface by an asphalt distributor. The emulsion is scrubbed into the cracks and voids with a broom before a layer of aggregate is applied over the asphalt. The scrub seal is then rolled with a pneumatic tire roller and is usually ready for controlled traffic in 1 hour or less. The scrub seal process is intended to rejuvenate dry, oxidized, and cracked asphalt pavements in lieu of a micro-surfacing, chip seal or asphalt overlay. This process was tested on roads that interested counties offered as a demo. Below, you’ll find images that were taken during the testing process.

Results

The evaluation of the demo roads showed success, and Bituminous is now focused on sand applications. Denco Construction purchased a sand spreader during the winter season to fulfill the county’s request.

According to Chris Aldama, Plant Manager at Bituminous, “It’s still a pretty fresh process. Denco was able to take approximately 10,000 gallons at the end of June, but needs to make adjustments on sand suppliers. Once sand quality is finalized, I’m confident in the long term success in this area and beyond.”

To learn more about the process, feel free to watch this video:

H.G. Meigs was a proud sponsor again this year at WCHA Highway Conference in Wisconsin Dells at the Chula Vista Resort on June 7 – 9, 2021.

Ken Schakelman Regional Sales Manager of H.G. Meigs notes that, ‘The Wisconsin County Highway Association is a very unique association. Unlike any other in the nation. First of all, they have been around for over 100 years and they represent the 72 county highway departments in Wisconsin in a variety of ways. The highway departments in Wisconsin act independently from the state DOT. Some may even produce asphalt, have full construction capabilities, crushing operations, you name it. It is very unique to my knowledge from other states. Also, since H.G. Meigs has been serving Wisconsin agencies and associations since 1935, we are extremely proud of our long-standing, long-term relationship with WCHA. In addition to our production capabilities, we often partner on items like education, helping with new products and new processes.’

Wisconsin’s 72 counties play a significant role in the state’s transportation system.  The Wisconsin County Highway Association (WCHA) is responsible for the construction and maintenance of the 19,700 mile County Trunk Highway System, as well as maintenance of the 11,800 mile State Trunk Highway System and Interstate System under the oversight of the Wisconsin Department of Transportation. Conference attendees included Highway Commissioners, Highway Committee Officials, Engineers, Associate Members, WisDOT Officials, and spouses/guests representing all areas of the state.

This event presents an excellent opportunity to promote any current or new products, equipment and services offered by various organizations. To learn more about WCHA’s representation of Wisconsin’s 72 County Highway and Public Works Departments, click here.

‘H.G. Meigs is a staunch supporter of the WCHA. Along with our booth display and our annual breakfast that feeds 300-400 people, we work with the WCHA in a variety of ways. You can see a breakfast we sponsored in early 2020 in the above photo.”

Ken Shackleman

AMI is committed to changing the standard in the asphalt industry. Our companies strive to implement new processes, ideas, services, and products with the goal of creating a more effective solution to your road construction projects. Our dedication to quality often results in improving roads through the process of pavement rehabilitation. Each project contains different conditions and construction histories which may alter the approach to conducting pavement rehabilitation, but there are several processes that can be utilized upon reviewing a pavement individually. In general, pavement rehabilitation is suited for pavement in the C, D and F pavement condition zones. This article will address how and when each process is used.

Any business that has been around for over 65 years should have a strong commitment to innovation. Asphalt Materials is that company. Our teams are focused on helping build longer-lasting, safer roads. To do that, we focus on big challenges as creative problem solvers. We have a unique opportunity available to us and our customers in that we are part of The Heritage Group, which includes the expertise that resides within The Heritage Research Group.

Collaboration is a hallmark of our approach as well. Working with contractors and departments of transportation, we take a collective approach that fosters long-term relationships and mutual trust. A recent project created an opportunity with Indiana State Road 234. The construction project consisted of  126,505 square yards of Cold In-place Recycling (CIR) at a depth of 4-inches. The project length was 10.37 miles with a 22 foot width. The project progression can be seen in the image below.

While comprised of similar components to conventional Hot Mix Asphalt, CIR lifts cannot be sampled in the same way to measure and confirm quality of the material. Instead, each CIR candidate pavement is sampled, with the representative materials going through a mix design process designed to closely approximate the CIR construction procedure in the lab. Once the CIR mixture meets or exceeds specified laboratory standards, construction can begin.

Per industry standard, several tests are performed during CIR operations to verify the exact material quantities are added to the mixture per the project’s mix design. In-place density testing is also performed to confirm optimal compaction is reached throughout the placed CIR lift. While this testing method is rigorous for the mixture’s components it does not directly measure mixture performance. The current testing standard reveals opportunities to test the constructed material for performance that is timely from a construction perspective and valuable for agency and contractor customers.

Heritage Research Group designed a field sampling method to sample constructed CIR materials just prior to field compaction, allowing for test specimens to be produced and performance tested, similar to mix design test specimens in the lab.

Additionally, a rare opportunity arose to sample the CIR by coring, shortly after construction and the final HMA overlay was completed. This provided field cores from the project for further analysis that is truly representative of the mixture.

Six, 6-inch cores were collected from eight locations on the project (see example below).

Based on these testing and material sampling opportunities, a research project was formed as follows:

• Evaluate sampling procedure for field-collected samples.
• Compare mix design results to field-collected samples.
• Quantify impact of delayed compaction of field samples.
• Compare mix design, field samples to field cores.

The variation in approximated versus representative processes in the three types of CIR samples provide a unique perspective to confirm accuracy of the field sampled mix tests and of the initial mix design test results. A diagram outlining the differentiations between mix design, field samples and field cores can be viewed below.

All of the CIR processes are approximated in the lab to produce a mix design, while field sampled materials contain more accurate versions of these processes because they are sampled from the constructed lift. Finally, cores collected from the project, several months after the CIR was completed, provide the most accurate version of the mixture, all of the CIR processes, including compaction, being true to the constructed CIR. 

After conducting testing to determine air voids in the mixtures, specimens were tested for marshall stability and indirect tensile strength in dry and wet conditions. These results are used to estimate a mixture’s resistance to water damage, rutting, and cracking in tension.

To further understand the long-term performance of the mixture, dynamic modulus testing was performed with small-scale AMPT specimens collected from the CIR pavement cores.

Several findings were determined upon analysis of the test:

• The sampling method to collect field mix samples for lab compaction and testing could be a method to verify CIR mixture properties in the future.
• The dynamic modulus test results provide additional data to the industry on the performance qualities of the constructed mixture, which also align with the current industry recommendations for the mastercurves which characterize CIR materials. 

This project is an excellent case study that demonstrates the outcomes that are possible when different groups are all driving to the same goal of creating longer lasting, safer roads.