by Roger C. Schmitt, P.E.
Let’s Look First at What Has Worked in the Past…
US 17/92 in front of the District Five Office
Over twenty years ago I was the Area Maintenance Engineer for Orlando and Oviedo Maintenance in District Five. At that time, George Gilhooley was the District Maintenance Engineer and one day for lunch we were walking to a Chinese restaurant just down the road from the District Office. We were admiring the concrete pavement on US 17/92 in front of the District Office. We asked ourselves: “Look how long this has lasted, why don’t we construct more concrete roads”?
The concrete pavement was construction from 1939. It was almost 60 years old 10 years ago. It required minimal maintenance. About every 15 to 20 years a hot poured asphalt sealer is poured between the joints to seal the water out. Nothing has been done to that concrete pavement in 10 years. The photos below shows the intersection of US 17/92 with SR 44 in downtown Deland. Notice the old cars in the early picture.
Today there are still no cracked slabs and there is just a little spalling at some of the joints. Why has this pavement lasted and other concrete roads have failed in 20 years or less.
In 1999, District Five’s Design, Construction, Materials and Research and Maintenance Engineer traveled north to Georgia and went on a fact finding tour about concrete pavements. They came back with big ideas on using concrete on the Interstate System in District Five. Today, we have a concrete pavement project underway on I-95 in Brevard County.
This is amazing. A simple question, lead to a new look at concrete pavement in Florida? In 2003, I became the District Materials and Research Engineer. We had a District Materials Engineer’s meeting and we were discussing how long our Interstate asphalt pavements were lasting. At that meeting I decided I would do a study and find out how long Portland Cement Concrete and Asphalt roadways were lasting in District Five. It took a lot longer than I had I anticipated. The Pavement Management System currently in use systematically stated that all concrete roads build before 1976 were constructed in 1976. We had to find the original roadway plans for concrete roads. Doing this, we found out all but a few were much older than the pavement management system gave them credit. See Figure 2 for a summary for pavement life expectancy in District Five.
Pavement Life Expectancy in District Five.
Looking at Figure 2 we can say in District five concrete pavement will last 3 to 5 times longer than a asphalt pavement and we should consider using more concrete pavements because in some projects, concrete will be more cost effective. The Department’s “Pavement Type Selection Manual” should be used on all projects that have a history of poor performing pavement and the design ESALs are greater than (10) million. District Five is not the only District that has concrete pavements that have lasted more than 50 years and are still in great shape. Please contact your District Materials and Research Engineer if you’re looking for details for your area.
When Should the Project Manager consider Concrete Pavement on Existing Pavement?
The first place you want to look is your roadways or corridors that have a high percentage of trucks. If designed and constructed properly concrete pavements outperform asphalt pavement where a large number of trucks use the roadway. Such roadways or corridors would include urban interstate or toll roads, airports, seaports, truck terminals, landfills, bus stops, truck weigh and inspection stations, rest areas and any other high traffic volume areas that future rehabilitation would require massive user delays.
The second important item is simply, can you raise the roadway? A good example may be a rural section that will be changing to an urban section and it include curb and gutter.
The third and maybe most important item is does the area have good non-erodible draining soil. Ideally a free draining sand and gravel soil is the best. Extensive and expensive drainage modifications can be made; however, these costs can be high.
How has the Department Improved Existing Roadways by Using Concrete Pavement?
District Seven concluded the reconstruction of I-4 in the Tampa Area would be more cost effective by removing the existing concrete pavement and reconstructing using concrete pavement. A large portion of I-4 is being reconstructed. District Seven is also constructing a truck weigh station on I-4 using concrete pavement. District Seven has a busy seaport and reconstructed a portion of 22nd Street in Tampa using concrete pavement. This roadway experiences 21% trucks and leads into the port. District Seven routinely replaces concrete slabs on I-175, I-275 and US 92 with minimal disruption of traffic.
When Should a Project Manager Consider Pavement on a New Roadway?
The Project Manager should consider concrete pavement for all new roadways that you anticipate heavy truck usage. You should also consider concrete pavement any time you are considering complete reconstruction, especially in a curb and gutter urban section. We have many examples in District Five where the concrete pavements have lasted, with little rehabilitation over 60 to 70 years. Absolutely no traffic delays due to repeated asphalt rehabilitation every 16 years.
Another area you may want to consider is an urban or rural section that will be expanded from 2- lanes to a 4- lane divided highway. This is ideal for several reasons. When constructing the new 2-lane section it will be completely closed to traffic. This will allow you plenty of time to cure the concrete before opening to traffic. After the new section is completed and you can move traffic on the new concrete pavement and begin working on the original 2- lane section. The original 2-lane section can now be completed without any interference with traffic.
When considering a project for concrete pavement, a life cycle cost analysis needs to be performed. You should contact your District Pavement Design Engineer and your District Materials Engineer to determine the section properties for both the concrete and asphalt roadway sections and materials properties. Based on this information, you can obtain the cost estimates from your estimates engineer for both pavement types. With this information you can determine if a concrete or asphalt pavements are more cost effective.
Conclusion:
The project manager should consider concrete pavement on roadways that have a large percentage of trucks. Any Busy Intersection, Interstate roadways and urban and rural sections where lane closures for rehabilitation are impractical because of heavy traffic congestion. Other areas are entrances to airports, seaports, truck transfer stations, garbage dumps and bus stops. Concrete pavements can out last asphalt pavements. However, the initial costs can be high for concrete pavement and a life cycle cost analysis should be performed to determine the most cost effective roadway section.
“Quality is never an accident; it is always the result of high intention, sincere effort, intelligent direction and skillful execution; it represents the wise choice of many alternatives.”
~William A. Foster~
