If you were asked to name the greatest paving advantage of asphalt over concrete, how would you answer? Most likely your answer would be that asphalt is chosen over concrete because the road or highway can be opened to traffic in a matter of hours, versus days for concrete pavements. What many people don't know is that this asphalt advantage no longer exists. Fast-track concrete pavements have become a reality thanks to cooperative efforts between the contractors and members of the Iowa Concrete Paving Association (ICPA), the Iowa Department of Transportation (IDOT), Iowa Counties, ACPA and others in the highway industry. On July 11 and 14, 1986, the IDOT and cosponsoring associations hosted their first National Fast-Track Concrete Resurfacing Open House on 7 miles of U.S. Highway 71 north of Storm Lake, Iowa. Over 400 state, city, county and Federal officials attended to watch the contractor, Central Paving Corporation, Indianola, Iowa place the bonded concrete overlay on the existing concrete pavement.
The key to the success of fast-track was the development of economical concrete mixes that can provide high strengths at a relatively early age--24 hours or less. The specifications developed by the Iowa DOT stated that the contractor had the option of using a mix with either 710 pounds of Type III cement or 640 pounds of Type III portland cement and 70 pounds of Class C fly ash. The ratio of coarse to fine aggregate in the mix was 55 percent coarse to 45 percent fine. Air-entrainment was set at 6 1/2 percent to ensure durability.