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As an engineer for the Federal Highway Administration (FHWA), Mike Praul travels around the country giving seminars on high-performance concrete (HPC) and extolling its virtues as something that will slow the deterioration of bridges and help our infrastructure. In his presentations, he shows slides of Roman structures. "There's a reason a lot of the concrete placed by the Romans is still standing. To some degree, the Romans inadvertently used a lot of high-performance technology in their concrete with the volcanic ash they used," he explains.

Obviously, HPC isn't as high-tech as it may sound; it involves using old-fashioned materials in different ways. But developing the wisdom to know a higher grade of concrete when you see it doesn't come in a day. For the 37-year-old Praul, it came from living in several places around the country to experience different ways of doing things in the concrete world.

After growing up in Seneca Falls, New York, in the heart of the Finger Lakes region, Praul got his B.S. in civil engineering from Clarkson University and later a Master of Engineering degree from Rensselaer Polytechnic Institute. During summers, he worked for an engineering consulting firm doing construction inspection on the New York State Thruway, leading to "an interest in the highway end of civil engineering," as he relates.

While at Clarkson, Praul interviewed with FHWA when they came to campus and received an offer from them. He started in 1987 as a highway engineer trainee and worked in North Carolina, Wisconsin, Tennessee, and West Virginia over the course of two years. Then came a stint as an assistant bridge engineer in Portland, Oregon followed by a four-year stay in Albany, New York as a structural engineer for FHWA's New York Division, a job that had him overseeing design and construction on famous bridges such as New York City's Brooklyn Bridge and Manhattan Bridge.

Praul admits, "The specialization in concrete and all that came about almost by accident." While working in Oregon, his boss had heard about specialty-type concretes and gave him a three-month assignment to learn all he could about it and develop a half-day seminar to give to state department of transportation (DOT) personnel. "I found the work very interesting."

His new endeavor mushroomed from there, Praul says. "When I came to the East, the New York State Department of Transportation ranked as a national leader in high-performance concrete, and I ended up working very closely with them on development of their HPC program. And then with all the work going on with the Boston Central Artery Project, I got involved helping them write their concrete specs and doing inspections for them and some forensics and troubleshooting and that kind of thing. I've just kind of stayed involved and gotten to the point now where I teach courses and seminars and speak at different conferences around the country."

Moving around so much has suited Praul just fine. "From a personal perspective, that's one of the reasons I took the job with the FHWA. I thought 'well, what better way to see the country than to have the government pay to move me around, train me, and I get to see a bunch of different places, live a bunch of different places."

Since 1996, Praul has served as the construction and materials engineer for FHWA's Maine Division in Augusta, Maine, managing the agency's construction and materials programs and assisting the Maine DOT with writing specifications and overseeing highway and bridge construction projects. He has proven instrumental in implementing quality assurance specifications and HPC technology in Maine. He also works half time for the FHWA Eastern Resource Center in Baltimore, Maryland, serving as a national technical resource in concrete.

In this dual role, Praul assists states around the country with implementation of HPC technology and specification writing. He also inspects construction projects using HPC and assists with forensic analyses to determine problem causes and develop solutions.

So just what is high-performance concrete? Most engineers know that standard concrete consists of Portland cement, water, sand, and stone. In HPC, ingredients known as pozzolans replace part of the cement. When mixed with water and the lime found in the cement, pozzolans react to form additional cementing compounds. The most common pozzolanic materials are fly ash, a byproduct of the coal-burning process in electric power plants, and silica fume, a product of electric arc furnaces producing steel alloys. Many state highway agencies have used HPC principles in bridge decks for years, as the use of pozzolans for this began in the early 1980s with New York and Virginia leading the way. Boston's Big Dig project has used HPC since 1994.

Adding pozzolans drastically improves the performance of concrete by increasing its strength and durability. The latter results from lower permeability and enhanced resistance to chemical attack. With less cement, less heat results from hydration, which helps when placing massive amounts of concrete. And HPC has a reduced percentage of water in it, resulting in less shrinkage.

"The big benefit in the areas I deal with comes in the bridge condition. When you look at the national bridge inventory database and the deterioration over time that happens to our bridges, there are a lot of bridges coming due for extensive rehabilitation, repair, replacement," Praul says. He tells how in the late 1960s, President Lyndon Johnson instituted the bare roads policy, which led to putting massive amounts of salt on our highways to melt ice and snow. This increased corrosion, the single biggest factor in bridge deck deterioration. The use of HPC slows this deterioration by preventing chloride ingress.

"A lot of people talk about stronger concrete, stronger bridges, and that kind of thing, but that's not the most significant part. The big bang for the buck is in the long-term durability. With the higher-performance concretes, you can get 75- and 100-year life out of your bridges," Praul explains. "Of the nearly half a million bridges in this country, most have concrete in them in one way or another, and the longer we can make that concrete last, the better off economically this country's going to be."

Praul stresses that HPC compares economically to ordinary concrete, but he adds, "The price we've got to pay is increased attention to detail during construction." In curing, for example, this means applying wet burlap or cotton mats to the concrete as soon as possible after finishing and for as long as possible. "The message we're trying to get to the field people is 'these aren't the same concretes you've always dealt with, and to ratchet up your performance and go to higher performing materials, the tolerances for shortcuts in quality control just aren't there anymore."

This keeps Praul traveling around the country giving talks on HPC. "I love it. I love living in Maine, and I don't know that I'd want to move anywhere else. But I do love to travel," he reveals. When asked if his message about HPC is well received, he exclaims, "Absolutely. The knowledge base has really improved, and they understand there's a lot more to concrete than just having strong concrete. They know the deterioration and what we are faced with as an industry." He sees more and more state highway agencies beginning to use HPC technologies, and he predicts over the next decade, the majority of state DOTs will make routine use of HPC technology.

This hearkens back to Praul's mention of Roman structures in his seminars. "We've come full circle now," as he puts it. They used volcanic ash in concrete; today's practitioners use fly ash. Maybe, through his efforts, we'll get the same longevity they did, and future generations will marvel at how long our bridges have lasted.

Progressive Engineer
Editor: Tom Gibson
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©2004 Progressive Engineer