The Economics of Dead Zones: Linking Externalities from the Land to their Consequences in the Sea, October 2012,

The purpose of this review and analysis is to provide a basic understanding of the issues related to worldwide hypoxic zones and the range of economic questions sorely in need of answers. We begin by describing the causes and extent of hypoxic zones worldwide, followed by a review of the evidence concerning ecological effects of the condition and impacts on ecosystem services. We describe what is known about abatement options and cost effective policy design before turning to an analysis of the large, seasonally recurring hypoxic zone in the Gulf of Mexico. We advance the understanding of this major ecological issue by estimating the relationship between pollutants (nutrients) and the areal extent of the hypoxic zone. This “production function” relationship suggests that both instantaneous and legacy contributions of nutrients contribute to annual predictions of the size of the zone, highlighting concerns that ecologists have raised about lags in the recovery of the system and affirms the importance of multiple nutrients as target pollutants. We conclude with a discussion of critical research needs to provide input to policy formation.

Measuring Salt Retention, 2013

This research developed and completed a field evaluation of salt distribution equipment. The evaluation provides a direct comparison of three different types of salt spreaders at three different truck speeds and brine rates. A rubber mat was divided into eight sample areas to measure the salt distribution across the lane by each variable combination. A total of 264 samples were processed and measured. These results will support future efforts to target areas of efficiencies specific to salt and brine delivery methods. These results support Iowa Department of Transportation efforts to progress winter maintenance efficiencies and ultimately motorist safety.

Measuring Salt Retention: Tech Transfer Summary, 2013.

This research developed and completed a field evaluation of salt distribution equipment. The evaluation provides a direct comparison of three different types of salt spreaders at three different truck speeds and brine rates. A rubber mat was divided into eight sample areas to measure the salt distribution across the lane by each variable combination. A total of 264 samples were processed and measured. These results will support future efforts to target areas of efficiencies specific to salt and brine delivery methods. These results support Iowa Department of Transportation efforts to progress winter maintenance efficiencies and ultimately motorist safety.

Effects of Deicing Salt Trace Compounds on Deterioration of Portland Cement Concrete, HR-271, 1987

A study was made of the detrimental effects of trace amounts of calcium sulfate (occurring naturally in halite deposits used for deicing) on portland cement concrete pavements. It was found that sulfate introduced as gypsum with sodium chloride in deicing brines can have detrimental effects on portland cement mortar. Concentrations of sulfate as low as 0.5% of the solute rendered the brine destructive. Conditions of brine application were critical to specimen durability. The mechanisms of deterioration were found to be due to pore filling resulting from compound formation and deposition. A field evaluation of deteriorating joints suggests that the sulfate phenomena demonstrated in the laboratory also operates in the field. A preliminary evaluation was made of remedies: limits on sulfates, fly ash admixtures, treatment of existing pavement, and salt treatments. This report gives details of the research objectives, experimental design, field testing, and possible solutions. Recommendations for further study are presented.

Deicing Salt Corrosion with and without Inhibitors, MLR-87-8, 1989

Chloride ion penetration through concrete to reinforcing steel is causing the premature deterioration of numerous bridge decks in Iowa. The purpose of the research reported in this paper was to determine whether any of several additives or alternative deicing chemicals could inhibit corrosion of reinforcing steel. The deicers tested were calcium magnesium acetate (CMA), CMA plus NaCl (NaCl: sodium chloride), Quicksalt plus PCI, and CG-90, a polyphosphate solution being developed by Cargill. Two tests were established. First, steel coupons were placed in a 15% solution of a deicer and distilled water to determine which alternative deicer would cause the least amount of corrosion in solution. The coupons were weighed periodically to determine each coupon's weight loss from corrosion. The second test involved ponding a 15% solution of each material on reinforced concrete blocks. Weekly copper-copper sulfate electrical half-cell (CSE) potential readings were taken on each block to determine whether corrosive activity was occurring at the steel surface. When the ponding research was concluded, concrete samples were taken from one of the three blocks ponded with each deicer. The samples were used to determine the chloride ion content at the level of the steel. Results show that all the deicers were less corrosive than NaCl. Only pure CMA, however, significantly inhibited the corrosion of steel embedded in concrete.

The Effect of Deicing Salt on Aggregate Durability, Progress Report HR-266, 1985

The Iowa DOT has been using rapid freezing in air and thawing in water to evaluate coarse aggregate durability in concrete since 1962. Earlier research had shown that the aggregate pore system was a major factor in susceptibility to D-cracking rapid deterioration. There are cases were service records show rapid deterioration of concrete containing certain aggregates on heavily salted primary roads and relatively good performance with the same aggregate in secondary pavements with limited use of deicing salt. A five-cycle salt treatment of the coarse aggregate prior to durability testing has yielded durability factors that correlate with aggregate service records on heavily salted primary pavements. X-ray fluorescence analyses have shown that sulfur contents correlate well with aggregate durabilities with higher sulfur contents producing poor durability. Trial additives that affect the salt treatment durabilities would indicate that one factor in the rapid deterioration mechanism is an adverse chemical reaction. The objective· of the current research is to develop a simple method of determining aggregate susceptibility to salt related deterioration. This method of evaluation includes analyses of both the pore system and chemical composition.