Evaluation of "FIBERMESH" Synthetic Fibers in P.C. Concrete Bridge Barrier Rail, MLR-88-17, 1988

Ten bridges were chosen to have their concrete barrier rails constructed with one rail having "Fibermesh" synthetic fibers added and the other rail without the fibers. The rails were constructed in 1985, 1986, or 1987. All the bridges were inspected in 1988 and no consistent reduction in cracking was achieved using Fibermesh fibers in the p.c. concrete bridge barrier rails.

Pavement Evaluation Using the Road Rater Deflection Dish, MLR-89-2, 1989

In recent years the Iowa Department of Transportation has shifted emphasis from the construction of new roads to the maintenance and preservation of existing highways. A need has developed for evaluating pavements structurally to select the correct rehabilitation strategy and to properly design a pavement overlay if necessary. Road Rater non-destructive testing has fulfilled this need and has been used successfully to evaluate pavement and subgrade conditions and to design asphaltic concrete overlays and portland cement concrete overlays. The Iowa Road Rater Design Method has been simplified so that it may be easily understood and used by various individuals who are involved in pavement restoration and management. Road Rater evaluation techniques have worked well to date and have been verified by pavement coring, soils sampling and testing. Void detection testing has also been performed, and results indicate that the Road Rater can be used to locate pavement voids and that Road Rater evaluation techniques are reasonably accurate. The success of Road Rater research and development has made dynamic deflection test data an important pavement management input.

Evaluation of Deterioration on US 20 in Webster County, MLR-91-1, 1991

Ten miles of U.S. Highway 20 in Webster County began to show deterioration in 1990. Any deterioration was unexpected, since the road was just constructed in 1986 and 1987. The deterioration looked much like the staining and cracking of D-cracking. Cracking was found on 391 joints throughout the 10 mile four lane divided highway. Evaluation of cores from the project reveal low air contents at those locations where cracking is occurring. The cause of the low air contents can only be speculated on. A possible cause may be the vibration from the paver coupled with the additional vibration at the joints. Other projects constructed in 1986 and 1987 with the same equipment show no signs of distress.

Evaluation of Concrete Patching Mixes and Opening Time Using the Maturity Concept, MLR-93-7, 1993

This report summarizes the findings of a research which was intended to evaluate the concrete strength and opening time for the full depth patching projects in Iowa under cold weather and whether or not cold water could be allowed in the mix. This research was performed both in the laboratory and in the field. The results indicated that with the present specification the concrete strength after five hours for two-lane patches which requires hot water and calcium chloride is about 1,600 psi. Hence, if a higher strength is desired, a longer curing time is required. Hot water will have to be used and water reducer is not recommended for two-lane patches. On the other hand, the concrete strength for multi-lane patches with either hot or cold water approaches 4,000 psi in less than 24 hours. There was only a slight difference in compressive strengths between the 24-hour and 36-hours curing times.

Evaluation Study of Pit Run Gravel Asphalt Treated Base Mixtures with Various Percentages of Crushed Limestone, R-217, 1968

In November of 1966, an investigation of the rigid Class I asphalt treated base specification, requiring 70 per cent crushed limestone, was initiated. It was felt that it might be possible to modify the need for crushed particles, in the construction of basis on heavy duty roads, at a savings, by using more local materials, without sacrificing strength and/or durability. This is a short study on typical sources of pit run gravel, with various percentages of limestone. It is conducted with an eye open to the possibility that our specifications may be modified. The possibility that further investigation may be desirable is not ignored.

Evaluation of Cohesion and Swell Characteristics of Asphalt Treated Base Mixtures, R-223, 1968

This study was undertaken to evaluate the suitability of various stones which play an important role in the properties of compacted mixtures in asphalt treated bases. The determination of the effect of water temperature on the cohesion of the mixes is investigated. A number of stones were prepared for the test. Attention is paid to the particular source of stone with the corresponding test results. A preliminary study of the effect of lime when added to mixed aggregate was also conducted. The purpose of this study is to provide needed information on the cohesive characteristics of asphalt treated bases using a wide range of stones. This study is also to evaluate the suitability of the various stone sources.

Evaluation of Photoacoustic Spectroscopy for Quality Control of Cement, TR-409, 1998

This report discusses the feasibility of using infrared photoacoustic spectroscopy (PAS) as a viable technique that can quickly provide information on cement composition prior to use. The PAS technique is of interest because the cost is much lower than for other types of instrumentation used for mineral analysis, it requires virtually no sample preparation, and it can perform multi-component analysis in a matter of minutes. Feasibility of the technique was based on the ability of PAS to identify and quantify sulfate species and major cement matrix components. Strengths and limitations of the technique are presented.

Evaluation of Appropriate Maintenance, Repair and Rehabilitation Methods for Iowa Bridges, TR-429, 2003

Most states, including Iowa, have a significant number of substandard bridges. This number will increase significantly unless some type of preventative maintenance is employed. Both the Iowa Department of Transportation and Iowa counties have successfully employed numerous maintenance, repair and rehabilitation (MR&R) strategies for correcting various types of deficiencies. However, successfully employed MR&R procedures are often not systematically documented or defined for those involved in bridge maintenance. This study addressed the need for a standard bridge MR&R manual for Iowa with emphasis for secondary road applications. As part of the study, bridge MR&R activities that are relevant to the state of Iowa have been systematically categorized into a manual, in a standardized format. Where pertinent, design guidelines have been presented. Material presented in this manual is divided into two major categories: 1) Repair and Rehabilitation of Bridge Superstructure Components, and 2) Repair and Rehabilitation of Bridge Substructure Components. There are multiple subcategories within both major categories that provide detailed information. Some of the detailed information includes step-by-step procedures for accomplishing MR&R activities, material specifications and detailed drawings where available. The source of information contained in the manual is public domain technical literature and information provided by Iowa County Engineers. A questionnaire was sent to all 99 counties in Iowa to solicit information and the research team personally solicited input from many Iowa counties as a follow-up to the questionnaire.

Evaluation of Gateway and Low-Cost Traffic-Calming Treatments for Major Routes in Small, Rural Communities, TR-523, 2007

Many rural communities have developed around highways or major county roads; as a result, the main street through small rural communities is often part of a high-speed rural highway. Highways and county roads are characterized by high speeds outside the city limits; they then transition into a reduced speed section through the rural community. Consequently, drivers passing through the community often enter at high speeds and maintain those speeds as they travel through the community. Traffic calming in small rural communities along major roadways is common in Europe, but the U.S. does not have experience with applying traffic-calming measures outside of major urban areas. The purpose of the project was to evaluate traffic-calming treatments on the major road through small Iowa communities using either single-measure low-cost or gateway treatments. The project was partially funded by the Iowa Highway Research Board (IHRB). The focus of the IHRB portion was to evaluate single-measure, low-cost, traffic-calming measures that are appropriate to major roads through small rural communities. Seven different low-cost traffic treatments were implemented and evaluated in five rural Iowa communities. The research evaluated the use of two gateway treatments in Union and Roland; five single-measure treatments (speed table, on-pavement “SLOW” markings, a driver speed feedback sign, tubular markers, and on-pavement entrance treatments) were evaluated in Gilbert, Slater, and Dexter.

Evaluation of Long-Term Field Performance of Cold In-Place Recycled Roads: Field Distress Survey, TR-502, 2007

Cold in-place recycling (CIR) has become an attractive method for rehabilitating asphalt roads that have good subgrade support and are suffering distress related to non-structural aging and cracking of the pavement layer. Although CIR is widely used, its use could be expanded if its performance were more predictable. Transportation officials have observed roads that were recycled under similar circumstances perform very differently for no clear reason. Moreover, a rational mix design has not yet been developed, design assumptions regarding the structural support of the CIR layer remain empirical and conservative, and there is no clear understanding of the cause-effect relationships between the choices made during the design/construction process and the resulting performance. The objective of this project is to investigate these relationships, especially concerning the age of the recycled pavement, cumulative traffic volume, support conditions, aged engineering properties of the CIR materials, and road performance. Twenty-four CIR asphalt roads constructed in Iowa from 1986 to 2004 were studied: 18 were selected from a sample of roads studied in a previous research project (HR-392), and 6 were selected from newer CIR projects constructed after 1999. This report summarizes the results of a comprehensive program of field distress surveys, field testing, and laboratory testing for these CIR asphalt roads. The results of this research can help identify changes that should be made with regard to design, material selection, and construction in order to lengthen the time between rehabilitation cycles and improve the performance and cost-effectiveness of future recycled roads.

Ultrathin Portland Cement Concrete Overlay Extended Evaluation, Construction Report, TR-432, 2000

In recent years, ultra-thin whitetopping (UTW) has evolved as a viable rehabilitation technique for deteriorated asphalt cement concrete (ACC) pavement. Numerous UTW projects have been constructed and tested, enabling researchers to identify key elements contributing to their successful performance. These elements include foundation support, interface bonding condition, portland cement concrete (PCC) overlay thickness, synthetic fiber reinforcement usage, joint spacing, and joint sealing. The interface bonding condition is the most important of these elements. It enables the pavement to act as a composite structure, thus reducing tensile stresses and allowing an ultra-thin PCC overlay to perform as intended. The Iowa Department of Transportation (Iowa DOT) UTW project (HR-559) initiated UTW in Iowa. The project is located on Iowa Highway 21 between Iowa Highway 212 and U.S. Highway 6 in Iowa County, near Belle Plaine, Iowa. The objective of this research was to investigate the interface bonding condition between an ultra-thin PCC overlay and an ACC base over time, considering the previously mentioned variables. This research lasted for five years, at which time it was extended an additional five years. The new phase of the project was initiated by removing cracked panels existing in the 2-inch thick PCC sections and replacing them with three inches of PCC. The project extension (TR 432) will provide an increased understanding of slab bonding conditions over a longer period, as well as knowledge regarding the behavior of the newly rehabilitated areas. In order to accomplish the goals of the project extension, Falling Weight Deflectometer (FWD) testing will continue to be conducted. Laboratory testing, field strain gage implementation, and coring will no longer be conducted. This report documents the planning and construction of the rehabilitation of HR 559 and the beginning of TR 432 during August of 1999.

Evaluation of Fly Ash in Portland Cement Concrete Pavement in Monona County, Iowa, Construction Report, HR-200, 1978

The primary objectives of this research project were: 1. Determine and recommend solutions for problems relating to shipping, storing and batching of fly ash. 2. Establish a procedure for batching, mixing and placing uniform concrete with specified air content and consistency. 3. Demonstrate that concrete of comparable quality can be produced.

An Evaluation of Cover Aggregate Stripping Characteristics, Progress Report, HR-182, 1977

The increasing use of seal coats for surface restoration and the concurrent increase in failures of such treatments prompted the current research. Field observations indicated that certain aggregate types seemed to be more susceptible to failure, including stripping and disintegration. The research was thus designed to try to identify those aggregate types which would perform satisfactorily under normal conditions.

An Evaluation of the Consolidation Monitoring Device, HR-1013, 1978

The Iowa Department of Transportation research project HR-1013 is the evaluation of a prototype continuous monitoring nuclear density unit. The Unit, the Consolidation Monitoring Device (CMD), mounts on the rear of a slip-form paver and measures the density of the concrete while still in the plastic state. The evaluation performed determined the usefulness, accuracy, precision and reproducibility of the unit. The CMD was calibrated and tested in the laboratory for one week before field evaluation. The field evaluation consisted of monitoring at least 5 miles of paving and then correlating the CMD data with two conventional density methods. The two supplemental methods were density measurement with a Troxler nuclear gauge and densities obtained from core samples.

Field Performance and Evaluation of Slurry Seals, HR-195, 1980

As part of the overall research program of evaluating asphalt emulsion slurry seal as a pavement maintenance material, 31 duplicate 500-ft test sections were constructed on U.S. 6 between Adel and Waukee in Dallas County during September and October of 1978. These test sections included combinations of eight aggregates, two gradings, three asphalt emulsions, two mineral fillers, and a range of emulsion contents determined by laboratory mix designs. The emulsion contents of the test sections varied from 10.3% for Section 7A (Ferguson coarse) to 32.9% for Section 31A (lightweight aggregate). The post-construction performance evaluation of the test sections, consisting primarily of the friction tests and surface appearance observations, was conducted at different time intervals up to 24 months after construction. At the 24-month final evaluation, most of the test sections had carried a total of 1.4 million vehicles.