Iowa State Highway 92 Over Drainage Ditch #25: Performance Evaluation - Galvanized Reinforcing Bars -- Louisa County, Iowa, 2015

Several strategies are available to the Iowa Department of Transportation (IaDOT) for limiting deterioration due to chloride-induced corrosion of embedded reinforcing bars in concrete bridge decks. While the method most commonly used throughout the Midwestern United States is to construct concrete bridge decks with fusion-bonded epoxy-coated reinforcing bars, galvanized reinforcing bars are an available alternative. Previous studies of the in situ performance of galvanized reinforcing bars in service in bridge decks have been limited. IaDOT requested that Wiss, Janney, Elstner Associates, Inc. (WJE) perform this study to gain further understanding of the long-term performance of an Iowa bridge deck reinforced with galvanized reinforcing bars. This study characterized the condition of a bridge deck with galvanized reinforcing bars after about 36 years of service and compared that performance to the expected performance of epoxy-coated or uncoated reinforcing bars in similar bridge construction. For this study, IaDOT selected the Iowa State Highway 92 bridge across Drainage Ditch #25 in Louisa County, Iowa (Structure No. 5854.5S092), which was constructed using galvanized reinforcing bars as the main deck reinforcing. The scope of work for this study included: field assessment, testing, and sampling; laboratory testing and analysis; analysis of findings; service life modeling; and preparation of this report. In addition, supplemental observations of the condition of the galvanized reinforcing bars were made during a subsequent project to repair the bride deck.

A Research Report on Roadside Vegetation Management, December 1975

According to prevailing ecological theory one would expect the most stable vegetation on sites which are least disturbed (Odum 1971). According to theory one would also expect the most diversity of species on undisturbed sites (Odum 1971). This stable and diverse community would be produced over a period of many years through a process of plant succession where annual herbs are replaced by perennial herbs and finally woody plants would come to dominate and perpetuate the community. Another ecological theory holds that the complexity (structure and species diversity) of a plant community is dependent upon the amount of disturbance to which it is subjected (Woodwell, 1970). According to this theory the normal succession of a plant community through its various stages may be arrested at some point depending upon the nature and severity of the disturbance. In applying these theories to roadside vegetation it becomes apparent that mass herbicide spraying and extensive mowing of roadsides has produced a relatively simple and unstable vegetation. It follows that if disturbances were reduced not only would the roadside plant community increase in stability but maintenance costs and energy usage would be reduced. In this study we have investigated several aspects of reduced disturbances on roadside vegetation. Research has centered on the effectiveness of spot spraying techniques on noxious weed control, establishment of native grass cover where ditch cleaning and other disturbance has left the bare soil exposed and the response of roadside vegetation when released from annual mass spraying.

Multiplan Spreadsheets for Highway and Hydraulic Engineering Computations in County Engineering Offices, HR-284, 1987

Multiplan spreadsheet solutions were developed for a set of hydraulic and highway engineering computations of common interest to county engineers. These include earthwork, vertical and horizontal curves, staking superelevated curves and sign inventories for highways. The hydraulic applications were ditch flow, runoff, culvert size and stage discharge.

Recycled Paper Erosion Control Mat, HR-349, 1994

The objective of this research project was to evaluate field application results and determine whether the Earth-Gard mat made from recycled material would successfully control erosion and allow vegetation to establish in ditch bottoms and steep slopes. The research would also help determine how steep a grade in the ditch bottoms can be protected from rill and gully erosion and how steep and long a backslope or foreslope can be protected from sheet and rill erosion by the recycled material and allow establishment of vegetation. The Earth-Gard gave satisfactory performance on areas with limited drainage and gradual slopes. Earth-Gard had a longevity of only six months. It was eroded away when used on areas with greater flow or steeper slopes.

Development of an Economic Dust Palliative for Limestone Surfaced Secondary Roads, HR-297, Progress Report, 1988

Research activities during this period concentrated on continuation of field and laboratory testing for the Dallas County test road. Stationary ditch collection of dust was eliminated because of inconsistent data, and because of vandalism to collectors. Braking tests were developed and initiated to evaluate the influence of treatments on braking and safety characteristics of the test sections. Dust testing was initiated for out of the wheelpath conditions as well as in the wheelpath. Contrary to the results obtained during the summer and fall of 1987, the 1.5 percent bentonite treatment appears to be outperforming the other bentonite treated sections after over a year of service. Overall dust reduction appears to average between 25 to 35 percent. Dallas County applied 300 tons per mile of class A roadstone maintenance surfacing to the test road in August 1988. Test data indicates that the bentonite is capable of interacting and functioning to reduce dust generation of the new surfacing material. Again, the 1.5 percent bentonite treatment appeared the most effective. The fine particulate bonding and aggregation mechanism of the bentonite appears recoverable from the environmental effects of winter, and from alternating wet and dry road surface conditions. The magnesium chloride treatment appears capable of long-term (over one year) dust reduction and exhibited an overall average reduction in the range of 15 to 30 percent. The magnesium chloride treatment also appears capable of interacting with newly applied crushed stone to reduce dust generation. Two additional one mile test roads were to have been constructed early this year. Due to an extremely dry spring and summer, construction scheduling was not possible until August. This would have allowed only minimal data collection. Considering this and the fact that this was an atypically dry summer, it was our opinion that it would be in the best interest of the research project to extend the project (at no additional cost) for a period of one year. The two additional test roads will be constructed in early spring 1989 in Adair and Marion counties.