Protection of Structural Concrete Substructures, HR-220, December 1992

In the past, many pier columns were deteriorating due to attack by chlorides. The chloride (from deicers) has attacked the substructures by drainage from the superstructure. Piers supporting grade separation bridges are also subject to chlorides contained in the direct splash from lower level traffic. Repairs of these piers are both difficult and costly. In this project, four different sealants were applied to piers to evaluate their use in the protection of the concrete against chloride-ions. One pier was left untreated to use as a control pier with which to compare the protected piers. This project began in 1980 and was to be completed in 1985, but at that time it was determined further testing was needed to make a more conclusive evaluation.

Low Water Stream Crossing: Design and Construction Recommendations; A Selection and Design Guide, February 2003

Most Iowa counties maintain low volume roads with at least one bridge or culvert that is structurally deficient or obsolete. In some counties the percentage of deficient drainage structures may be as high as 62%. Replacement with structures of similar size would require large capital expenditures that many counties cannot afford. Low water stream crossings (LWSCs) may be an acceptable lowcost alternative in some cases.

Evaluation of Safety Treatments for Roadside Culverts: TR-517, April 24, 2009

Roadside cross-drainage culverts have been found to impact vehicle accident injury levels. Designers have commonly used three safety treatments to protect errant drivers from culvert accidents. These treatments have included: culvert extension, guardrail installation and grating. In order to define which safety treatment is the most appropriate, benefit-cost analysis has used accident cost reduction to estimate societal gains earned by using any safety treatment. The purpose of this study was to estimate accident costs for a wide range of roadway and roadside characteristics so that designers can calculate benefit/cost ratios for culvert safety treatment options under any particular scenario. This study began with conducting a parametric study in order to find variables which have significant impact on accident cost changes. The study proceeded with highway scenario modeling which included scenarios with different values for combinations of roadway and roadside variables. These variables were chosen based upon findings from the parametric study and their values were assigned based upon highway classification. This study shows that the use of different culvert safety treatments should be flexible to roadway and roadside characteristics. It also shows that culvert extension and grating were the safety treatments found to produce the lowest accident costs for all highway scenarios modeled. Therefore, it is believed that the expanded adoption of culvert extension and culvert grates can improve overall highway safety.

Concrete Overlay Field Application Program Iowa Task Report US 18 Concrete Overlay Construction Under Traffic, May 2012

The National Concrete Pavement Technology Center, Iowa Department of Transportation, and Federal Highway Administration set out to demonstrate and document the design and construction of portland cement concrete (PCC) overlays on two-lane roadways while maintaining two-way traffic. An 18.82 mile project was selected for 2011 construction in northeast Iowa on US 18 between Fredericksburg and West Union. This report documents planning, design, and construction of the project and lessons learned. The work included the addition of subdrains, full-depth patching, bridge approach replacement, and drainage structural repair and cleaning prior to overlay construction. The paving involved surface preparation by milling to grade and the placement of a 4.5 inch PCC overlay and 4 foot of widening to the existing pavement. In addition, the report makes recommendations on ways to improve the process for future concrete overlays.

Field Demonstration of Foamed Asphalt Muscatine County, HR-257, 1988

The foamed asphalt concept has been around since the 1950's. Rising oil prices have created a renewed interest in this process. The purpose of this project was to construct an asphalt base using the foamed asphalt process and to evaluate its performance. A 4.2 mile length of Muscatine County road A-91 was selected for the research project. Asphalt contents of 4.5% and 5.5%, moisture contents of 70% and 90% of optimum, and fog, single chip, and double chip seal coats were used in various combinations to lay 9 test sections of 4-inch foamed asphalt base. After five years of service and evaluation, several conclusions can be made concerning the performance of the foamed asphalt bases: (1) the foamed asphalt process can work as shown by the excellent performance of Sections 2 and 3; (2) foamed asphalt base requires a well compacted subgrade and a road profile suitable for good drainage of water--test section failures were mostly due to a poor subgrade and subsurface moisture; and (3) when the base is placed in two or more lifts, extreme care must be exercised to insure adequate bonding is achieved between lifts. Any future research with foamed asphalt should include various asphalt depths in order to determine a thickness/strength relationship for foamed asphalt.

Method for Estimating the Magnitude and Frequency of Floods at Ungaged Sites on Unregulated Rural Streams in Iowa, HR-268, 1987

This report provides techniques and procedures for estimating the probable magnitude and frequency of floods at ungaged sites on Iowa streams. Physiographic characteristics were used to define the boundaries of five hydrologic regions. Regional regression equations that relate the size of the drainage area to flood magnitude are defined for estimating peak discharges having specified recurrence intervals of 2, 5, 10, 25, 50, and 100 years. Regional regression equations are applicable to sites on streams that have drainage areas ranging from 0.04 to 5,150 square miles provided that the streams are not affected significantly by regulation upstream from the sites and that the drainage areas upstream from the sites are not mostly urban areas. Flood-frequency characteristics for the mainstems of selected rivers are presented in graphs as a function of drainage area.

Low-Cost Rural Surface Alternatives: Literature Review and Recommendations, TR-632, 2013

Freezing and thawing action induces damage to unbound gravel roads in Iowa resulting in maintenance costs for secondary road departments. Some approaches currently used by County Engineers to deal with this problem include temporarily spreading rock on the affected areas, lowering or improving drainage ditches, tiling, bridging the area with stone and geosynthetic covered by a top course of aggregate or gravel, coring boreholes and filling them with calcium chloride to melt lenses and provide drainage, and re-grading the crown to a slope of 4% to 6% to maximize spring drainage. However, most of these maintenance solutions are aimed at dealing with conditions after they occur. This study was tasked with identifying alternative approaches in the literature to mitigate the problem. An annotated bibliographic record of literature on the topic of frost-heave and thaw-weakening of gravel roads was generated and organized by topic, and all documents were assessed in terms of a suitable rating for mitigating the problem in Iowa. Over 300 technical articles were collected and selected down to about 150 relevant articles for a full assessment. The documents collected have been organized in an electronic database, which can be used as a tool by practitioners to search for information regarding the various repair and mitigation solutions, measurement technologies, and experiences that have been documented by selected domestic and international researchers and practitioners. Out of the 150+ articles, 71 articles were ranked as highly applicable to conditions in Iowa. The primary mitigation methods identified in this study included chemical and mechanical stabilization; scarification, blending, and recompaction; removal and replacement; separation, and reinforcement; geogrids and cellular confinement; drainage control and capillary barriers, and use of alternative materials. It is recommended that demonstration research projects be established to examine a range of construction methods and materials for treating granular surfaced roadways to mitigate frost-heave and thaw-weakening problems. Preliminary frost-susceptibility test results from ASTM D5916 are included for a range of Iowa materials.

Underseal Evaluation Project: Poweshiek County I-80 Near Milepost 189.5, Eastbound Roadway, MLR-85-10, 1985

The purpose of this project was to determine the optimal hole pattern needed for undersealing work, and also to determine if it is feasible to underseal a roadway with existing longitudinal subdrains without plugging the subdrain system. At the test site the hole pattern had little effect on the grout distribution. It was found that the hole pattern, to be effective, must locate existing voids and that holes must extend at least 2 in. (5 cm) below the underside of the pavement. It appeared that pavements can be undersealed without significant damage to the existing subdrains, but special care is needed to assure that excess grout is not injected into the drainage system. Recommendations are made concerning the hole pattern, grout efflux time, and procedures for minimizing the risk of plugging the subdrains with grout.

Permeability of Granular Subbase Materials, MLR-90-4, 1991

The purpose of this research was to evaluate the materials Iowa uses as a granular subbase and to determine if it provides adequate drainage. Numerous laboratory and in-situ tests were conducted on the materials currently being used in Iowa. The follow conclusions can be made based on the test results: 1. The crushed concrete that is used as a subbase material has a relatively low permeability compared to many other materials used by other states. 2. Further research and tests are needed to find the necessary parameters for crushed concrete to make sure it is providing its optimum drainage and preventing premature damage of the pavement. 3. We have definitely made improvements in drainage in the past few months, but there are many areas that we can improve on that will increase the permeability of this material and insure that the pavement system is safe from premature damage due to water. The current gradation specification for granular subbase material at the start of this study was: Sieve # % Passing 1” 100 #8 10-35 #50 0-15 #200 0-6

Pipe Rehabilitation with Polyethylene Pipe Liners, HR-370, 2003

Corroded, deteriorated, misaligned, and distorted drainage pipes can cause a serious threat to a roadway. Normal practice is to remove and replace the damaged drainage structure. An alternative method of rehabilitating these structures is to slip line them with a polyethylene liner. Twelve drainage structures were slip lined with polyethylene liners during 1994 in Iowa. Two types of liners installed were "Culvert Renew" and "Snap-Tite." It was found that the liners could be easily installed by most highway, county, and city maintenance departments. The liners restore the flow and increase the service life of the original drainage structure. The liners were found to be cost competitive compared with the removal and replacement of the existing drainage structure. Slip lining has the largest economic benefit when the roadway is paved, the culvert is under a deep fill, or traffic volumes are high. The annular space between the original pipe and the liner was filled with flowable mortar. Care should be taken to properly brace and grout the annular space between the liner and the culvert to avoid deformation of the liner.

Iowa Development of Rubblized Concrete Pavement Base - Mills County, HR-315, 1995

Iowa counties have tried to rehabilitate deteriorating portland cement concrete (PCC) pavements with standard overlays, placement of engineering fabric, rock, open graded bituminous mixes and cracking and seating. While these methods prolong the life of the road, the cracks in the old pavement have eventually reflected to the surface. One possible alternative for rehabilitating severely deteriorated roads and preventing reflective cracking is the rubblization process. The objective of this research project was to rehabilitate and evaluate a severely deteriorated PCC roadway using a rubblization process. A 3.0 km (1.9 mi) section of L63 in Mills County was selected for this research. The road was divided into 16 sections. A resonate frequency vibration pavement breaker was used to rubblize the existing pavement. The variables of rubblization, drainage, and ACC overlay depths of 75 mm (3 in.), 100 mm (4 in.), and 125 mm (5 in.) were evaluated. The research on rubblized concrete pavement bases support the following conclusions: (1) The rubblization process prevents reflective cracking; (2) Edge drains improved the structural rating of the rubblized roadway; (3) An ACC overlay of 125 mm (5 in.) on a rubblized base provided an excellent roadway regardless of soil and drainage conditions; (4) An ACC overlay of 75 mm (3 in.) on a rubblized base can provide a good roadway if the soil structure below the rubblized base is stable and well drained; and (5) The Road Rater structural ratings of the rubblized test sections for this project are comparable to the nonrubblized test sections.

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.

Use of Longitudinal Subdrains in the 3R Program, HR-509, Progress Report #2, 1981

The main consideration for base construction under the pavement, in the design of Iowa's interstate, was structural capacity. The material was dense graded with the aim of supporting the pavement and distributing the load as it is transferred to the underlying grade. The drainage characteristics of the base was apparently not given adequate consideration. On jointed portland cement concrete pavement, the water that is trapped immediately beneath the pavement causes severe problems. The traffic causes rapid movement of the water resulting in the hydraulic pressures or "pumping" (movement and redeposit of base fine material), further resulting in faulting between individual slabs. The objective of this evaluation is to determine if longitudinal subdrains are effective in preventing or reducing pumping, faulting and related deterioration. Results suggest that, based upon the flow from the outlets observed during periodic checks and evidence of water flow at the outlets, it appears that to date the subdrains are effective in draining the subbase and subgrade. Because of the limited data available at this time, however, the pavement condition and faulting results are inconclusive.

Pipe Rehabilitation with Polyethylene Pipe Liners, HR-370, Construction Report, 1995

Corroded, deteriorated, misaligned, and distorted drainage pipes can cause a serious threat to a roadway. Normal practice is to remove and replace the damaged drainage structure. An alternative method of rehabilitating these structures is to slip line them with a polyethylene liner. Twelve drainage structures were slip lined with polyethylene liners during 1994 in Iowa. Two types of liners installed were "Culvert Renew" and "Snap-Tite". It was found that the liners could be easily installed by most highway, county, and city maintenance departments. The liners restore the flow and increase the service life of the original drainage structure. The liners were found to be cost competitive with the removal and replacement of the existing drainage structure. Slip lining has the largest economic benefit when the roadway is paved, the culvert is under a deep fill, or traffic volumes are high. The annular space between the original pipe and the liner was filled with flowable mortar. Care should be taken to properly brace and grout the annular space between the liner and the culvert.

Low Cost Fly Ash - Sand Stabilized Roadway Des Moines County, HR-259, 1991

The objectives of this research were to develop a low cost fly ash-sand stabilized roadway and to correlate field performance with pavement design assumptions on a county road heavily trafficked by trucks hauling grain. The road was constructed during the summer of 1984. Three test sections comprised of different base thicknesses were incorporated in the roadway and were tested for compressive stength, structural rating, and rut depth. Annual crack surveys showed no appreciable difference in transverse cracking between the test sections and little to no rutting. The sandbase drainage characteristics beneath the roadway may have contributed to the satisfactory performance of the test sections. This project indicates that in spite of the inflated cost of construction due to the research nature of the work, a fly ash-sand base can be a viable alternative for roadway stabilization.