What got you interested in preservation?

My interest in pavement preservation can be related back to the design of concretes course that I had taken during my undergraduate degree, also at Iowa State University. That class was my first introduction to the incredibly extensive and complex nature of both hot mix asphalt and portland cement concrete.

The interest in pavement preservation that Dr. Ashley Buss -- the asphalt instructor for this course -- has was contagious. With my captivation with the course clearly apparent, Dr. Buss invited me to join her graduate research team that focuses on pavement preservation. Between the research and other pavement-related courses, my interest in this field has only grown.

How is your research related to pavement preservation?

With increasing economic pressures, the amount of money spent on pavement preservation needs to be more effectively utilized. As local agencies try to balance the fine line between cost-effective preservation and end-user happiness, an understanding of local preservation performance is key.

The bulk of my Ph.D. research has been on a study with the Iowa DOT to do just that. By use of their pavement management system (PMS), Dr. Buss and I have been able to take pavement distress data from before and after a preservation treatment was used, and determine the service life extension and quantify any distress mitigation.

Ben Claypool, grad student at Iowa State University, studies pavement preservation.

Dr. Ashley Buss, assistant professor of civil, construction and environmental engineering at Iowa State University, pursues research in sustainable pavement practices, including pavement preservation, warm mix asphalt additives, recycled asphalt pavement and shingles, bio-based additives, adhesives, chip seals and micro surfacing, and life-cycle cost analysis

The PMS includes a staggering amount of information collected on all of Iowa’s primary roadways, including, but not limited to:

• Pavement Condition Index (PCI)

• Rutting Index (based on average rut depths)

• Riding Index (based on IRI values)

• Faulting Index (based on average fault size), and

• Cracking Index (based on collective cracking condition).

With these index values collected for a given preservation treatment, the use of either a linear, second-order polynomial, or reflected logistic sigmoidal function was fit to the data prior to the preservation to provide a trend that would best approximate the condition of the pavement if no preservation was performed.

In a similar fashion, these functions were also fit to the data from the time of preservation onwards, to provide a trend to best approximate the condition of the pavement after seeing a preservation treatment.

Fig. 1 shows a hypothetical example of one project’s index values, with relative year zero reflecting the time of the preservation treatment application. The index value on the y-axis is representative of any one of the indices listed above.

The figure highlights some of the formal analysis that has taken place, including data removal from curve fitting, and the determination of initial index value benefits and service life extensions.

Fig. 2 shows one of the micro surfacing projects that was analyzed in this study. The multiple markers visible at each relative year are the PMS values at different locations along the same project. This preservation resulted in a PCI increase of just over 35 points, and extended the overall condition of the pavement for more than four years.

Various preservation projects have been evaluated under this method of analysis, including slurry seals, micro surfacings, patching (HMA and PCC), crack sealing/joint filling (HMA and PCC), grinding and grooving, and dowel bar retrofit and grinding.

On a project quantity basis, more asphalt preservation projects have been evaluated than PCC preservation projects, with the results currently being reviewed by the technical advisory committee for the Iowa DOT.

How has your perspective changed about road infrastructure since the beginning of the research?

 They always say, the more you know about something, the less you actually understand it. Having dug into a wide variety of pavement attributes, I am only beginning to see the entire picture. The relationships between materials, traffic, politics, construction, agencies, funding, and the general public all play into the overall pavement network.

While driving the other day, I reflected on just how much my understanding and passion of pavements has grown, from seeing surface cracks and knowing why they exist, to arguing the side of paving contractors when people complain about road construction, or even just appreciating a smooth drive while it lasts.

How will you apply pavement preservation to your career post-graduation?

After graduation, I will be taking my position as a civil engineer for the city of Cedar Falls, Iowa.  I plan on taking everything that I have been lucky enough to learn and be able to provide insight within the department in any way that I can. 

Time and time again, the pavement preservation community has proven the pavement cost saving and life extending benefits of a successful preservation program.

By maintaining my role as an advocate for the benefits of pavement preservation, I hope to perpetuate the mindset that pavement preservation is a priority and not just a side note.