Bonded, Thin-Lift, Non-Reinforced Portland Cement Concrete Resurfacing, HR-191, 1980

A Research Project involving two, three, four and five inches of bonded Portland Cement Concrete Overlay on a 1.3 mile Portland Cement Concrete pavement was conducted in Clayton County, Iowa, during September, 1977, centering on the following objectives: 1. Determine the mixing and proportioning procedures required in using a conventional, central mix proportioning plant to produce a dense Portland Cement Concrete mixture using standard mixes with super-water reducing admixtures; 2. Determine the economics, longevity and maintenance performance of a bonded, thin-lift, non-reinforced Portland Cement Concrete resurfacing course using conventional procedures, equipment and concrete paving mixtures both with and without super-water reducing admixtures; 3. Determine if an adequate bond between the existing pavement and an overlay of thin-lift, dense, non-reinforced Portland Cement Concrete can be obtained with only special surface cleaning and no surface removal or grinding.

A Further Evaluation of Concrete Bridge Deck Surfacing in Iowa, MLR-79-1, 1979

The Iowa Department of Transportation has overlaid 446 bridge decks with low slump dense concrete from 1964 through October 1978. The overall performance of these decks has been satisfactory. Nineteen bridges that were resurfaced with either low slump dense concrete (LSDC) or latex-modified concrete were analyzed for chloride content, electrical corrosion potential, delaminations or debonding, and deck surface condition. The resurfacing ages of these bridges range from 5 to 13 years. None of the bridges showed any evidence of surface distress and the chloride penetration into the resurfacing concrete is relatively low. There are delaminations in the original decks below the resurfacing on the majority of bridges examined. The delaminations are concluded to be caused by either (A) reinforcing steel corrosion, (B) not removing all delaminated concrete prior to placing the resurfacing concrete, or (C) creating an incipient fracture in the top surf ace of the original deck through the use of scarification equipment. The active corrosion of the reinforcing steel is predominately in the gutter line on the majority of bridges evaluated. Recommendations for future deck repairs include removal of concrete to the top layer of reinforcing steel in areas where an electrical corrosion potential of -0.35V or more is detected, providing more positive methods of locating delaminated concrete, and treating the curb and gutter line to reduce the potential damage from salt water.

07043-017 North Fork Maquoketa Final Report

The North Fork Maquoketa River Headwaters (NFMRH) has been identified as impaired by nutrients, episodic slugs of ammonia and sediment. The NFMRH TMDL plan calls for a "phasing approach" to managing water quality when the origin is non-point source contaminants. This project will address phase 1 using a performance reward program for targeted cooperators to improve environmental index scores using cost-share, EQIP practices and flexible management alternatives. Pre-project assessments suggest that rewards should target refined management of erosion-prone fields and farms with livestock populations, which contribute to the P and N loads responsible for fertilizing filamentous algae blooms that depress dissolved oxygen concentrations in the NFMRH. The Phosphorus Index, Soil Conditioning Index and cornstalk nitrate test will be used by producers to determine effective alternatives, such as no-till planting, to reduce nutrient and sediment delivery. These evironmental indexes will be especially useful for livestock producers in the livestock dense watershed. This project will extend a NRCS-sponsored Conservation Innovation Grant currently offered to producers in the Coffee Creek sub-watershed to a three-year, watershed-wide effort that will be necessary to make significant improvements in environmental management.

Effects of Special Aggregate on Bridge Deck Overlay Frictional Properties, HR-205, 1986

The Iowa DOT has been using the "Iowa Method" thin bonded low-slump dense Portland Cement Concrete (PCC) bridge deck overlay for rehabilitation of delaminated decks since 1963. In time, continued use of studded tires will wear away the transverse grooved texture. The objective of this research was to evaluate the benefit of incorporating a hard durable aggregate into a dense PCC overlay to provide frictional property longevity. The project included three overlays on I-35 near Ankeny. The texture and friction properties of two overlays, one constructed with crushed granite and the other with crushed quartzite coarse aggregate, were compared to an overlay constructed with locally available crushed limestone. There were no construction problems resulting from the use of crushed granite or quartzite. There was no significant frictional property benefit from the crushed granite or crushed quartzite through six years.

Cathodic Protection for a Continuous Box Girder Bridge Deck, HR-553, 1993

Bridge deck deterioration due to corrosive effect of deicers on reinforcing steel is a major problem facing many agencies. Cathodic protection is one method used to prevent reinforcing steel corrosion. The application of a direct current to the embedded reinforcing steel and a sacrificial anode protects the steel from corrosion. This 1992 project involved placing an Elgard Titanium Anode Mesh Cathodic Protection System on a bridge deck. The anode was fastened to the deck after the Class A repair-work and the overlay was placed using the Iowa Low Slump Dense Concrete System. The system was set up initially at 1 mA/sq ft.

Chloride Penetration Into LSDC (Iowa System) Resurfacing Mixes, MLR-77-05 and R-267, 1977

The purpose of this investigation was to determine the comparative effectiveness of standard D-57 concrete and Iowa system Low Slump Dense Concrete in preventing threshold levels of chloride from penetrating the concrete slabs to the reinforcing steel.

A Study of the Frictional Properties of New Asphaltic Concrete Pavements in Iowa, MLR-78-03, 1978

Seven asphaltic concrete resurfacing projects were tested for their frictional properties to determine the age-friction relationship of new paving. Projects studied included Type A asphaltic concrete which is generally used for higher traffic volume roads and Type B asphaltic concrete, a lower type material. Also included in the study were asphaltic concretes containing Type 3 and Type 4 coarse aggregate texture classifications. The classifications are based upon material type and grain size composition. Surfaces both with and without sprinkle treatment aggregates were also included. The data gathered suggests that properly designed and placed dense graded asphaltic concrete mixes are adequate to serve the traveling public at all ages tested.

Performance of Poly-Carb, Inc. Flexogrid Bridge Overlay System, MLR-86-04, 2001

Intrusion of deicing materials and surface water into concrete bridge decks is a main contributor in deck reinforcing steel corrosion and concrete delamination. Salt, spread on bridge decks to melt ice, dissolves in water and permeates voids in the concrete deck. When the chloride content of the concrete in contact with reinforcing steel reaches a high enough concentration, the steel oxidizes. In Iowa, the method used to reduce bridge deck chloride penetration is the application of a low slump dense concrete overlay after the completion of all Class A and Class B floor repairs. A possible alternative to the use of dense concrete overlays, developed by Poly-Carb, Inc., is the MARK-163 FLEXOGRID Overlay System. FLEXOGRID is a two component system of epoxy and urethane which is applied on a bridge deck to a minimum thickness of ¼ inch. An aggregate mixture of silica quartz and aluminum oxide is broadcast onto the epoxy at a prescribed rate to provide deck protection and superior friction properties. The material is mixed on site and applied to the deck in a series of lifts (usually two) until the desired overlay thickness has been attained.

Evaluation of High-Slump Concrete for Bridge Deck Overlays, TR-427, 2005

The Iowa Method for bridge deck overlays has been very successful in Iowa since its adoption in the 1970s. This method involves removal of deteriorated portions of a bridge deck followed by placement of a layer of dense (Type O) Portland Cement Concrete (PCC). The challenge encountered with this type of bridge deck overlay is that the PCC must be mixed on-site, brought to the placement area and placed with specialized equipment. This adds considerably to the cost and limits contractor selection, because not all contractors have the capability or equipment required. If it is possible for a ready-mix supplier to manufacture and deliver a dense PCC to the grade, then any competent bridge deck contractor would be able to complete the job. However, Type O concrete mixes are very stiff and generally cannot be transported and placed with ready-mix type trucks. This is where a “super-plasticizer” comes in to use. Addition of this admixture provides a substantial increase in the workability of the concrete – to the extent that it can be delivered to the site and placed on the deck directly out of a ready-mix truck. The objective of this research was to determine the feasibility of placing a deck overly of this type on county bridges within the limits of county budgets and workforce/contractor availability.

Iowa System of Bridge Deck Rehabilitation with Cathodic Protection, HR-1044, 1986

Bridge deck and substructure deterioration due to the corrosive effects of deicing chemicals on reinforcing steel is a problem facing many transportation agencies. The main concern is protection of older bridges with uncoated reinforcing steel. Many different methods have been tried over the past years to repair bridge decks. The Iowa system of bridge deck rehabilitation has proven to be very effective. It consists of scarifying the deck surface, removing any deteriorated concrete, and overlaying with low slump dense concrete. Another rehabilitation method that has emerged is cathodic protection. It has been used for many years in the protection of underground pipelines and in 1973 was first installed on a bridge deck. Cathodic protection works by applying an external source of direct current to the embedded reinforcing steel, thereby changing the electrochemical process of corrosion. The corroding steel, which is anodic, is protected by changing it to a cathodic state. The technology involved in cathodic protection as applied to bridge decks has improved over the last 12 years. One company marketing new technology in cathodic protection systems is Raychem Corporation of Menlo Park, California. Their system utilizes a Ferex anode mesh that distributes the impressed direct current over the deck surface. Ferex mesh was selected because it seemed readily adaptable to the Iowa system of bridge deck rehabilitation. The bridge deck would be scarified, deteriorated concrete removed, Ferex anode mesh installed, and overlaid with low slump dense concrete. The Federal Highway Administration (FHWA) promotes cathodic protection under Demonstration Project No. 34, "Cathodic Protection for Reinforced Concrete Bridge Decks."

Comparison of Roadway Roughness Derived from LIDAR and SFM 3D Point Clouds, HR-3001, 2015

This report describes a short-term study undertaken to investigate the potential for using dense three-dimensional (3D) point clouds generated from light detection and ranging (LIDAR) and photogrammetry to assess roadway roughness. Spatially continuous roughness maps have potential for the identification of localized roughness features, which would be a significant improvement over traditional profiling methods. This report specifically illustrates the use of terrestrial laser scanning (TLS) and photogrammetry using a process known as structure from motion (SFM) to acquire point clouds and illustrates the use of these point clouds in evaluating road roughness. Five roadway sections were chosen for scanning and testing: three gravel road sections, one portland cement concrete (PCC) section, and one asphalt concrete (AC) section. To compare clouds obtained from terrestrial laser scanning and photogrammetry, the coordinates of the clouds for the same section on the same date were matched using open source computer code. The research indicates that the technologies described are very promising for evaluating road roughness. The major advantage of both technologies is the large amount of data collected, which allows the evaluation of the full surface. Additional research is needed to further develop the use of dense 3D point clouds for roadway assessment.

09008-005 Hewitt Creek Final Report

The primary goal of the Hewitt Creek watershed council is to have Hewitt-Hickory Creek removed from the Iowa impaired waters (303d) list. Hewitt Creek watershed, a livestock dense 23,005 acre sub-watershed of the Maquoketa River Basin, is 91.2% agricultural and 7.5% woodland. Since 2005, sixty-seven percent of 84 watershed farm operations participated in an organized watershed improvement effort using a performance­ based watershed management approach, reducing annual sediment delivery to the stream by 4,000 tons. Watershed residents realize that water quality improvement efforts require a long-term commitment in order to meet their watershed improvement goals and seek funding for an additional five years to continue their successful watershed improvement project. Cooperators will be provided incentives for improved environmental performance, along with incentives and technical support to address feedlot runoff issues and sub-surface nitrate-nitrogen loss. The Phosphorus Index, Soil Conditioning Index and cornstalk nitrate test will be used by producers as measures of performance to refine nutrient and soil loss management and to determine effective alternatives to reduce nutrient and sediment delivery. Twenty-five livestock operations will improve feedlot runoff control systems and five sub-surface bioreactors will be installed to reduce nitrate delivery from priority tile-drained fields. The Hewitt Creek council will seek additional cost-share funding for high-cost feedlot runoff control structures, sediment control basins and stream bank stabilization projects.

1231-014 Twelve Mile Lake Watershed Final Report

Twelve Mile Creek Lake is a 660 acre, Significant Publicly Owned Lake with a watershed of 14,820 acres for a ratio of 21:3. The watershed is predominately privately owned agricultural land that originates in Adair County and drains into the lake which serves as the primary source water for the City of Creston, Union County and the seven counties served by the Southern Iowa Rural Water Association. In recent years, frequent algae blooms and recurrent spikes in suspended solid concentrations have been inflating water treatment expenses for the Creston Municipal Utilities (CMU). Declining trends in water quality spurred CMU to enlist the Union Soil and Water Conservation District (SWCD) to assist in evaluating watershed conditions for potential upland improvements. Significant gully erosion issues that had been previously underestimated were discovered during this watershed assessment process. Newly acquired LiDAR elevation data readily revealed this concern which was previously obscured from view by the dense tree canopy. A Watershed Development and Planning Assistance Grant Application was approved and funded by the Iowa Department of Ag and Land Stewardship- Division of Soil Conservation. Throughout the planning process, project partners innovatively evaluated and prioritized a number of resource concerns throughout the watershed. The implementation plan presented will thwart these threats which left unaided will continue to diminish the overall health of the system, reduce the appeal of the lake to recreational users, and contribute to higher water treatment costs.