Engineering Study for the Evaluation of Public Road Administration and Maintenance Alternatives, Executive Summary for HR-265, 1985

Iowa's public road system of 112,000 miles is one of the largest and the best in the nation. It represents a considerable financial investment of taxpayer revenues over the years. And, it requires a sustained investment to preserve an economical level of transport service into the future. In 1982, a Governor's Blue Ribbon Transportation Task Force evaluated the effectiveness of Iowa's entire transportation system. Four important Task Force recommendations dealt with public road administrative issues in Iowa. These issues were related to: 1. design criteria and levels of maintenance 2. consistency in the use of standards among jurisdictions 3. consolidation of maintenance operations at one jurisdictional level and 4. jurisdictional authority for roads. The issues formed the background for Research Project HR-265.

Field Evaluation of Engineering Fabrics for Asphalt Concrete Resurfacing - Audubon County, HR-360, Construction Report, 1994

An asphalt concrete (ACC) overlay is most often the rehabilitative effort used to maintain the serviceability of either an ACC or PCC pavement. The major problem in durability of this ACC overlay comes from reflective cracking. These cracks usually open, allowing water to enter the unsealed crack and strip the ACC in the overlay. The stripping of the ACC allows accelerated deterioration at the crack. Two engineering fabrics were evaluated in this project in order to determine their effectiveness in reducing reflective cracking. These two materials are: PavePrep, Contech Construction Products, Inc., and Pro-Guard, Phillips Fiber Corporation. A 4.2 km (2.6 mi) roadway in Audubon County was selected for the research project. The roadway was divided into eight test sections. Four of the test sections are conventional resurfacing. The other four sections are split between the two engineering fabrics (two Pro-Guard and two PavePrep). A 75 mm (3 in.) thick overlay was placed over the entire project.

Design and Operation of the Traffic Simulator, HR-100, 1967

Heavy traffic volumes frequently cause distress in asphalt pavements which were designed under accepted design methods and criteria. The distress appears in the form of rutting in the wheel tracks and rippling or shoving in areas where traffic accelerates or decelerates. Apparently accepted stability test methods alone do not always assure the desired service performance of asphaltic pavements under heavy traffic. The Bituminous Research Laboratory, Engineering Research Institute of Iowa State University undertook the development of a laboratory device by which the resistance of an asphalt paving mix to displacement under traffic might be evaluated, and also be used as a supplemental test to determine adequacy of design of the mix by stability procedures.

Concrete Pavement Mixture Design and Analysis (MDA): An Innovative Approach To Proportioning Concrete Mixtures, TPF-5(205), 2015

Mixture proportioning is routinely a matter of using a recipe based on a previously produced concrete, rather than adjusting the proportions based on the needs of the mixture and the locally available materials. As budgets grow tighter and increasing attention is being paid to sustainability metrics, greater attention is beginning to be focused on making mixtures that are more efficient in their usage of materials yet do not compromise engineering performance. Therefore, a performance-based mixture proportioning method is needed to provide the desired concrete properties for a given project specification. The proposed method should be user friendly, easy to apply in practice, and flexible in terms of allowing a wide range of material selection. The objective of this study is to further develop an innovative performance-based mixture proportioning method by analyzing the relationships between the selected mix characteristics and their corresponding effects on tested properties. The proposed method will provide step-by-step instructions to guide the selection of required aggregate and paste systems based on the performance requirements. Although the provided guidance in this report is primarily for concrete pavements, the same approach can be applied to other concrete applications as well.

Missouri River Studies: Alluvial Morphology and Engineering Soil Classification, HR-1, Progress Report, 1960

The primary purposes of this investigation are: 1) To delineate flood plain deposits with different geologic and engineering properties. 2) To provide basic data necessary for any attempt at stabilizing flood plain deposits. The alluvial valley of the Missouri River adjacent to Iowa was chosen as the logical place to begin this study. The river forms the western boundary of the state for an airline distance of approximately 139 miles; and the flood plain varies from a maximum width of approximately 18 miles (Plates 2 and 3, Sheets 75 and 75L) to approximately 4 miles near Crescent, Iowa (Plate 8, Sheet 66). The area studied includes parts of Woodbury, Monona, Harrison, Pottawattamie, Mills, and Fremont counties in Iowa and parts of Dakota, Thurston, Burt, Washington, Douglas, Sarpy, Cass and Otoe counties in Nebraska. Plate l is an index map of the area under consideration.

Field Evaluation of Engineering Fabrics for Asphalt Concrete Resurfacing - Audubon County, HR-360, Final Report, 2001

An ACC overlay is most often the rehabilitative effort used to maintain the serviceability of either an ACC or PCC pavement. The major problem in durability of this ACC overlay comes from reflective cracking. These cracks usually open, allowing water to enter the unsealed crack and strip the ACC in the overlay. The stripping of the ACC allows accelerated deterioration at the crack. Two engineering fabrics were evaluated in this project in order to determine their effectiveness in reducing reflective cracking. These two materials are: • PavePrep, Contech Construction Products Inc. • ProGuard, Phillips Fiber Corporation The data indicated a statistically significant decrease in reflective crack formation in the ProGuard fabric sections compared to control. There was little evidence of a similar effect from the PavePrep fabric sections compared to control. However, the rate of cracking (the rate of formation of new cracks) for both fabrics and control tended to be similar after three years. The benefits of using these fabrics (possible delay of some crack formation by two years) on this project did not outweigh the costs of up to $4200.00 per mile.

Design and Performance Verification of UHPC Piles for Deep Foundations, TR-558, 2008

The strategic plan for bridge engineering issued by AASHTO in 2005 identified extending the service life and optimizing structural systems of bridges in the United States as two grand challenges in bridge engineering, with the objective of producing safer bridges that have a minimum service life of 75 years and reduced maintenance cost. Material deterioration was identified as one of the primary challenges to achieving the objective of extended life. In substructural applications (e.g., deep foundations), construction materials such as timber, steel, and concrete are subjected to deterioration due to environmental impacts. Using innovative and new materials for foundation applications makes the AASHTO objective of 75 years service life achievable. Ultra High Performance Concrete (UHPC) with compressive strength of 180 MPa (26,000 psi) and excellent durability has been used in superstructure applications but not in geotechnical and foundation applications. This study explores the use of precast, prestressed UHPC piles in future foundations of bridges and other structures. An H-shaped UHPC section, which is 10-in. (250-mm) deep with weight similar to that of an HP10×57 steel pile, was designed to improve constructability and reduce cost. In this project, instrumented UHPC piles were cast and laboratory and field tests were conducted. Laboratory tests were used to verify the moment-curvature response of UHPC pile section. In the field, two UHPC piles have been successfully driven in glacial till clay soil and load tested under vertical and lateral loads. This report provides a complete set of results for the field investigation conducted on UHPC H-shaped piles. Test results, durability, drivability, and other material advantages over normal concrete and steel indicate that UHPC piles are a viable alternative to achieve the goals of AASHTO strategic plan.

Fly Ash Soil Stabilization for Non-Uniform Subgrade Soils, Volume I: Engineering Properties and Construction Guidelines, TR-461, 2005

Soil treated with self-cementing fly ash is increasingly being used in Iowa to stabilize fine-grained pavement subgrades, but without a complete understanding of the short- and long-term behavior. To develop a broader understanding of fly ash engineering properties, mixtures of five different soil types, ranging from ML to CH, and several different fly ash sources (including hydrated and conditioned fly ashes) were evaluated. Results show that soil compaction characteristics, compressive strength, wet/dry durability, freeze/thaw durability, hydration characteristics, rate of strength gain, and plasticity characteristics are all affected by the addition of fly ash. Specifically, Iowa selfcementing fly ashes are effective at stabilizing fine-grained Iowa soils for earthwork and paving operations; fly ash increases compacted dry density and reduces the optimum moisture content; strength gain in soil-fly ash mixtures depends on cure time and temperature, compaction energy, and compaction delay; sulfur contents can form expansive minerals in soil–fly ash mixtures, which severely reduces the long-term strength and durability; fly ash increases the California bearing ratio of fine-grained soil–fly ash effectively dries wet soils and provides an initial rapid strength gain; fly ash decreases swell potential of expansive soils; soil-fly ash mixtures cured below freezing temperatures and then soaked in water are highly susceptible to slaking and strength loss; soil stabilized with fly ash exhibits increased freeze-thaw durability; soil strength can be increased with the addition of hydrated fly ash and conditioned fly ash, but at higher rates and not as effectively as self-cementing fly ash. Based on the results of this study, three proposed specifications were developed for the use of self-cementing fly ash, hydrated fly ash, and conditioned fly ash. The specifications describe laboratory evaluation, field placement, moisture conditioning, compaction, quality control testing procedures, and basis of payment.

Mix Design Development for Pervious Concrete in Cold Weather Climates

Portland cement pervious concrete (PCPC) is being used more frequently due to its benefits in reducing the quantity of runoff water,improving water quality, enhancing pavement skid resistance during storm events by rapid drainage of water, and reducing pavement noise. In the United States, PCPC typically has high porosity and low strength, which has resulted in the limited use of pervious concrete, especially in hard wet freeze environments (e.g., the Midwestern and Northeastern United States and other parts of the world).Improving the strength and freeze-thaw durability of pervious concrete will allow an increase in its use in these regions. The objective of this research is to develop a PCPC mix that not only has sufficient porosity for stormwater infiltration, but also desirable strength and freeze-thaw durability. In this research, concrete mixes were designed with various sizes and types of aggregates, binder contents, and admixture amounts. The engineering properties of the aggregates were evaluated. Additionally, the porosity, permeability, strength, and freeze-thaw durability of each of these mixes was measured. Results indicate that PCPC made with single-sized aggregate has high permeability but not adequate strength. Adding a small percent of sand to the mix improves its strength and freeze-thaw resistance, but lowers its permeability. Although adding sand and latex improved the strength of the mix when compared with single-sized mixes, the strength of mixes where only sand was added were higher. The freeze-thaw resistance of PCPC mixes with a small percentage of sand also showed 2% mass loss after 300 cycles of freeze-thaw. The preliminary results of the effects of compaction energy on PCPC properties show that compaction energy significantly affects the freeze-thaw durability of PCPC and, to a lesser extent, reduces compressive strength and split strength and increases permeability.