Equipment World Digital Magazine
Issue link: http://read.dmtmag.com/i/692436
June 2016 | EquipmentWorld.com 66 road science | continued a planned straight run of pavement will create noticeable mars on the surface. Therefore, it's important to keep a con- sistent head of material in the machine and to coordinate truck delivery and operations at the mix site. Mix design and weather Mix design and weather conditions also affect the quality of the pavement. Low humidity, high heat and high winds can dry out the PCC, which requires a delicate balance between workability and firmness. If the mix dries out, it loses workability and no manner of operational expertise will be able to improve the pavement. "Slight variations in aggregate and moisture conditions can cause prob- lems," says David Howrey, president of Howrey Construction in Rockwell City, Iowa. His firm is a recent winner of a 2015 Concrete Paving Award from the Iowa Concrete Paving Association (ICPA). The awards recognize projects that are evaluated on several factors, including smoothness. "A perfect mix design on paper is easy," Howrey says, "but getting that perfect mix design out of the mixer and through the paver and to have it act consistent is another matter. Just a slight variation of the moisture content can make it act differently." Howrey says he's witnessed contractors who work as if they believe the paver should be able to create perfect results in any condition. "In a job done this past year, we had a dirt contractor get into the concrete pave- ment business and he had an inexperi- enced guy running the paver. It was 95 degrees and he didn't understand why he was having issues. He was having nightmares over the project because the machine wasn't doing what he thought it should be doing. Every minute the concrete sits in those conditions, it's hydrating." Steve Jackson, president of Cedar Valley Corporation in Waterloo, Iowa, agrees with Howrey on the weather is- sue, as his staff lists it at the top of their challenges. Cedar Valley is consistently recognized for its quality concrete pave- ments, winning five awards from the ICPA's 2015 round of recognition, and a Gold Award from the American Con- crete Pavement Association's 2015 Ex- cellence in Concrete Pavements awards. Mix design and concrete consistency also is a top concern, but Jackson adds that poor design may be a bigger prob- lem when it comes to smoothness. The Ten Commandments of Smoothness O ften quoted and redistributed, the "Ten Command- ments of Smoothness" was originally produced by Chapin Cipherd of CMI Corporation (now CMI Roadbuilding) in 1988 and is included in the American Concrete Pavement Assocition's Best Practices for Construct- ing Smooth Concrete Pavements. 1. Develop a smoothness plan for the specific project. 2. Develop an accurate field survey for stringline/ stringless controls. 3. Properly prepare the grade, providing a stable form or track line. 4. Set up proper forms properly for fixed-formed paving. 5. Use a consistent concrete mixture appropriate for the paving method. 6. Deliver and place concrete consistently. 7. Set-up and operate the paver steadily. 8. Fasten dowels/reinforc- ing securely and use "bump-free" construc- tion joints (headers). 9. Use only necessary and appropriate finishing techniques. 10. Apply texturing and curing with care. Cedar Valley's work on Iowa Route E34 in Monona County, Iowa. The project recently won a Gold Award for County Roads from the American Concrete Pavement Association. Image: American Concrete Pavement Association