Retrospective: Dayton, Ohio
As the birthplace of aviation and key manufacturing industries, Dayton, Ohio (2013 pop. 143,355) is also the birthplace of the first machine-assisted municipal street with interlocking concrete pavement. Built in November 1985, the repaving project likely never generated much cocktail chatter among Dayton’s historical society, but it was part of the city’s multimillion-dollar investment to help revitalize several historic districts. The city supported millions in private investment by urban pioneers during the 1970s and 1980s. Such funding renewed vintage late-1800s homes and brought physical and social stability to old neighborhoods.
After 20 years, this magazine issued an interim report in 2005 on the 11,000 sf Tecumseh Street in Dayton’s Oregon Historic District. When constructed in 1985, it was considered a demonstration project by the City, an expression of support for a rundown neighborhood being revitalized with a consistent infusion of restorative sweat equity by residents. While a lightly trafficked pavement in a residential neighborhood, the editor again visited the 31-year-old street last year to inspect the project. Since the editor was responsible for building the project for the City in 1985, the visit was more like listening to an old friend.
From a functional perspective, there were only a few cracked interlocking concrete pavers. Most pavement cracking occurred within the deteriorated concrete collars set around manholes and shutoff valves. By comparison, the pavers will certainly outlast the cast-in-place collars.
The decades-old road base is a 7-inch thick mix of cement and aggregates, a hardened slurry that once supported a macadam surface, a thin layer of asphalt mixed with sand. This base had roughly 20% of it removed and replaced in 1985 due to deteriorated areas. As part of the renovation, the macadam, an early version of today’s asphalt surfacing, and the top of the concrete base were ground out and removed to receive an inch of bedding sand and 3 1/8-inch thick concrete pavers. These were machine-set in a 90-degree herringbone pattern in three days.
The aging base shows in a few areas where the paver surface has settled. Had the surface been asphalt, they would have been potholes. The pavers accommodate such movements while continuing to provide service to passing vehicles.
The pavement structure has at least another decade of remaining life. The pavers will almost certainly outlast the base. The strongest indicator of a need for repairs will happen when the base settles in places that eventually set off neighborhood driver complaints. That is unlikely as vehicle speeds are generally below 20 mph.
From a life-cycle cost analysis (LCCA) perspective, Tecumseh Street asks the question, what’s the long-term expense to Dayton’s taxpayers compared to asphalt or concrete? Would more street pavers ultimately save the City money? Since 1985, asphalt prices have fluctuated while interlocking concrete pavement has not. For residential streets in northern states, resurfacing (shave and pave) can be reasonably set at 17 to 20 years. An LCCA favorable to interlocking concrete pavement would compare costs for periodic asphalt pavement resurfacing. Such resurfacing during higher priced markets could likely register a savings by using concrete pavers.
The larger question asked by the street is institutional in nature. Just about every city has organized design, specifications, construction and maintenance equipment, and labor around asphalt and, to a lesser degree, concrete pavements. From a certain perspective, cities’ street maintenance departments are committed to asphalt because it’s cheap. Rather than a single street in pavers, what if Dayton had an entire neighborhood, district, or city with them? While an investment in a third pavement is an additional expense, would interlocking concrete pavement be less expensive to maintain from a city budget perspective if it was the majority pavement, replacing asphalt?
Cost comparisons could be modeled using pavement management software that most cities use to project maintenance costs. One aspect is for certain, departmental investment in construction and maintenance equipment, as well as labor and materials, would be significantly lower for concrete pavers than that required for asphalt. If deemed a cost savings, a shift by any city street maintenance department to pavers would require phasing out asphalt in low-speed streets. There would likely be a commensurate increase in property values due to enhanced neighborhood character. Whether a historic district or not, such enhancements benefit the City and property owners alike.