Sixth Street, north of U.S. 30 to the Union Pacific RR, has shown significant deterioration and heaving at the pavement joints/cracks recently. This heaving, and subsequent very rough ride, is presumed due to the deterioration of the Portland cement concrete (PCC) pavement, which underlies the asphalt surface. The deterioration is also presumed to be a result of ‘D’-cracking, or failure of the stone in the concrete matrix, which is a common problem with coarse aggregates, normally limestone, in PCC pavements constructed in the 60s and 70s.
‘D’-cracking is accelerated by deicing salts, which accumulate in the pavement joints and migrate from there. As the limestone coarse aggregate fails, the resulting silt-like material absorbs water and expands, and the water further expands during freezing in the winter. Thus, the heaving at the joints occurs.
The City Council has heard options from the city’s engineer and voted to rehabilitate the roadway by removing the existing asphalt surface, crushing or “rubblizing” the existing deteriorated PCC pavement for use as a granular subbase, and placing a structural layer of 8” of Hot Mix Asphalt. Subdrains will be added to promote adequate drainage under the pavement. Poor drainage under the existing pavement most likely contributed to its failure. The life expectancy is 20 to 25 years.
On March 10, the City Council approved the contract with HRG Company to design and bid the south Sixth Street roadway improvements. According to the project timeline, the bid may be awarded in May, construction to begin in July, and the project completion date is Oct. 1.
The city will have a representative on site during the project to ensure the work is done according to the plans.
The entire community will be notified by a variety of means, since parts of Sixth Street may be closed during the project. During construction, it is anticipated through traffic will detoured away from the project area. However, local access will be maintained.
If you have any questions, please do not hesitate to contact the City Administrator Elizabeth Hansen at 382-5466 or City Engineer Larry Stevens at 515-278-2913.