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.

Maintenance of Pavement Skid Resistance (Open Graded Asphalt Friction Courses), Progress Report, HR-170, 1976

This project involved the evaluation of several aggregates previously rated poor to excellent with respect to skid resistance and certain mix design parameters. An open graded asphalt friction course was evaluated using 4 comparably graded aggregates: quartzite, fine grained limestone, coarse limestone and lightweight expanded shale. The performance investigations involved the verification of observations of the quartzite test sections, evaluation of the effect of blending the superior quartzite with a typical coarse grained-textured limestone, and the evaluation of the limestone. The effects of traffic on the aggregates used in the test sections were studied, as well as the relationship between asphalt content levels and traffic with respect to performance. The bond of the open graded friction course mixture was also evaluated. The SN performance of all test sections after sixteen months of exposure was found to be satisfactory in that none of the material combinations had polished to the point where unacceptable SN levels developed. When material combinations were compared, significant differences were noted.

Skid Resistance of the Secondary Road System in Iowa, MLR-77-1, 1977

The Iowa Department of Transportation has been conducting skid resistance tests on the paved secondary system on a routine basis since 1973. This report summarizes the data obtained through 1976 on 10,101 miles in 95 of the 99 counties in Iowa. A summary of the skid resistance on the secondary system is presented by pavement type and age. The data indicates that the overall skid resistance on this road system is excellent. Higher traffic roads (over 1000 vehicles per day) have a lower skid resistance than the average of the secondary roads for the same age and pavement type. The use of non-polishing aggregates in asphaltic concrete paving surface courses and transverse grooving of portland cement concrete paving on high traffic roads is recommended. The routine resurvey of skid resistance on the secondary road system on a 5-year interval is probably not economically justified and could be extended to a 10-year interval.

A Laboratory Investigation of An Accelerated Polishing Method for Determining the Skid Resistance Potential of Aggregates, MLR-76-02 and R-264, 1976

An initial feasibility study indicated that the "Purdue Accelerated Polishing Method" gave repeatable results when testing the skid resistance of laboratory specimens. The results also showed a rough correlation with the field performance of the same aggregate sources. The research was then expanded to include all available asphalt aggregates. The results of the expanded study indicated that the method is not presently capable of developing and measuring the full skid potential of the various aggregate sources. Further research in the area of polishing times and/or pressures is needed.

Effect of Anti-Strip Agents on Temperature Susceptibility of Asphalt Cements, MLR-87-01, 1987

Anti-strip agents can effect the temperature susceptibility of asphalt cement. This concern was expressed at the 33rd Annual Bituminous Conference in St. Paul, Minnesota by Mr. David Gendell, Director of Highway Operations. This study compares viscosity-temperature relationships of asphalt cement with and without anti-strip agent addition.

Economics of Using Calcium Chloride vs. Sodium Chloride for Deicing/Anti-Icing, TR-488, 2008

The use of chemicals is a critical part of a pro-active winter maintenance program. However, ensuring that the correct chemicals are used is a challenge. On the one hand, budgets are limited, and thus price of chemicals is a major concern. On the other, performance of chemicals, especially at lower pavement temperatures, is not always assured. Two chemicals that are used extensively by the Iowa Department of Transportation (Iowa DOT) are sodium chloride (or salt) and calcium chloride. While calcium chloride can be effective at much lower temperatures than salt, it is also considerably more expensive. Costs for a gallon of salt brine are typically in the range of $0.05 to $0.10, whereas calcium chloride brine may cost in the range of $1.00 or more per gallon. These costs are of course subject to market forces and will thus change from year to year. The idea of mixing different winter maintenance chemicals is by no means new, and in general discussions it appears that many winter maintenance personnel have from time to time mixed up a jar of chemicals and done some work around the yard to see whether or not their new mix “works.” There are many stories about the mixture turning to “mayonnaise” (or, more colorfully, to “snot”) suggesting that mixing chemicals may give rise to some problems most likely due to precipitation. Further, the question of what constitutes a mixture “working” in this context is a topic of considerable discussion. In this study, mixtures of salt brine and calcium chloride brine were examined to determine their ice melting capability and their freezing point. Using the results from these tests, a linear interpolation model of the ice melting capability of mixtures of the two brines has been developed. Using a criterion based upon the ability of the mixture to melt a certain thickness of ice or snow (expressed as a thickness of melt-water equivalent), the model was extended to develop a material cost per lane mile for the full range of possible mixtures as a function of temperature. This allowed for a comparison of the performance of the various mixtures. From the point of view of melting capacity, mixing calcium chloride brine with salt brine appears to be effective only at very low temperatures (around 0° F and below). However, the approach described herein only considers the material costs, and does not consider application costs or other aspects of the mixture performance than melting capacity. While a unit quantity of calcium chloride is considerably more expensive than a unit quantity of sodium chloride, it also melts considerably more ice. In other words, to achieve the same result, much less calcium chloride brine is required than sodium chloride brine. This is important in considering application costs, because it means that a single application vehicle (for example, a brine dispensing trailer towed behind a snowplow) can cover many more lane miles with calcium chloride brine than with salt brine before needing to refill. Calculating exactly how much could be saved in application costs requires an optimization of routes used in the application of liquids in anti-icing, which is beyond the scope of the current study. However, this may be an area that agencies wish to pursue for future investigation. In discussion with winter maintenance personnel who use mixtures of sodium chloride and calcium chloride, it is evident that one reason for this is because the mixture is much more persistent (i.e. it stays longer on the road surface) than straight salt brine. Operationally this persistence is very valuable, but at present there are not any established methods to measure the persistence of a chemical on a pavement. In conclusion, the study presents a method that allows an agency to determine the material costs of using various mixtures of salt brine and calcium chloride brine. The method is based upon the requirement of melting a certain quantity of snow or ice at the ice-pavement interface, and on how much of a chemical or of a mixture of chemicals is required to do that.