Investigation into Improved Pavement Curing Materials and Techniques: Part 2 - Phase III, March 2003

Appropriate curing is important for concrete to obtain the designed properties. This research was conducted to evaluate the curing effects of different curing materials and methods on pavement properties. At present the sprayed curing compound is a common used method for pavement and other concrete structure construction. Three curing compounds were selected for testing. Two different application rates were employed for the white-pigmented liquid curing compounds. The concrete properties of temperature, moisture content, conductivity, and permeability were examined at several test locations. It was found, in this project, that the concrete properties varied with the depth. Of the tests conducted (maturity, sorptivity, permeability, and conductivity), conductivity appears to be the best method to evaluate the curing effects in the field and bears potential for field application. The results indicated that currently approved curing materials in Iowa, when spread uniformly in a single or double application, provide adequate curing protection and meet the goals of the Iowa Department of Transportation. Experimental curing methods can be compared to this method through the use of conductivity testing to determine their application in the field.

Investgiation into Improved Pavement Curing Materials and Techniques: Part 1 - Phases I and II, April 2002

Concrete curing is closely related to cement hydration, microstructure development, and concrete performance. Application of a liquid membrane-forming curing compound is among the most widely used curing methods for concrete pavements and bridge decks. Curing compounds are economical, easy to apply, and maintenance free. However, limited research has been done to investigate the effectiveness of different curing compounds and their application technologies. No reliable standard testing method is available to evaluate the effectiveness of curing, especially of the field concrete curing. The present research investigates the effects of curing compound materials and application technologies on concrete properties, especially on the properties of surface concrete. This report presents a literature review of curing technology, with an emphasis on curing compounds, and the experimental results from the first part of this research—lab investigation. In the lab investigation, three curing compounds were selected and applied to mortar specimens at three different times after casting. Two application methods, single- and double-layer applications, were employed. Moisture content, conductivity, sorptivity, and degree of hydration were measured at different depths of the specimens. Flexural and compressive strength of the specimens were also tested. Statistical analysis was conducted to examine the relationships between these material properties. The research results indicate that application of a curing compound significantly increased moisture content and degree of cement hydration and reduced sorptivity of the near-surface-area concrete. For given concrete materials and mix proportions, optimal application time of curing compounds depended primarily upon the weather condition. If a sufficient amount of a high-efficiency-index curing compound was uniformly applied, no double-layer application was necessary. Among all test methods applied, the sorptivity test is the most sensitive one to provide good indication for the subtle changes in microstructure of the near-surface-area concrete caused by different curing materials and application methods. Sorptivity measurement has a close relation with moisture content and degree of hydration. The research results have established a baseline for and provided insight into the further development of testing procedures for evaluation of curing compounds in field. Recommendations are provided for further field study.

Development of In-Situ Detection Methods for Materials-Related Distress (MRD) in Concrete Pavements, July 2003

The purpose of this research was to summarize existing nondestructive test methods that have the potential to be used to detect materials-related distress (MRD) in concrete pavements. The various nondestructive test methods were then subjected to selection criteria that helped to reduce the size of the list so that specific techniques could be investigated in more detail. The main test methods that were determined to be applicable to this study included two stress-wave propagation techniques (impact-echo and spectral analysis of surface waves techniques), infrared thermography, ground penetrating radar (GPR), and visual inspection. The GPR technique was selected for a preliminary round of “proof of concept” trials. GPR surveys were carried out over a variety of portland cement concrete pavements for this study using two different systems. One of the systems was a state-of-the-art GPR system that allowed data to be collected at highway speeds. The other system was a less sophisticated system that was commercially available. Surveys conducted with both sets of equipment have produced test results capable of identifying subsurface distress in two of the three sites that exhibited internal cracking due to MRD. Both systems failed to detect distress in a single pavement that exhibited extensive cracking. Both systems correctly indicated that the control pavement exhibited negligible evidence of distress. The initial positive results presented here indicate that a more thorough study (incorporating refinements to the system, data collection, and analysis) is needed. Improvements in the results will be dependent upon defining the optimum number and arrangement of GPR antennas to detect the most common problems in Iowa pavements. In addition, refining highfrequency antenna response characteristics will be a crucial step toward providing an optimum GPR system for detecting materialsrelated distress.

Defining the Attributes of Good In-Service Portland Cement Concrete Pavements, December 2004

Much of the current research in portland cement concrete (PCC) pavements deals with the analysis of early pavement life failures and seeks to find ways to prevent those from reoccurring. The Long Term Pavement Performance (LTPP) portion of the Strategic Highway Research Program (SHRP) has identified some of the key factors in designing and building new PCC pavements. This statement will build on the Iowa Highway Research Board (IHRB) project TR-463, Field Performance Study of Past Iowa Pavement Research: A Look Back. In Iowa and across the nation, there are multiple pavements that were built more than 20 years ago that have been and are continuing to provide very good service to the public. They are found on both state and local routes and in both low and high traffic volume areas. There is a need to learn what went into those pavements, from the subgrade through the surface, that makes them perform so well. The purpose of this research project was to conduct a scoping study that could be used to evaluate the need for additional research to study the attributes of well-performing concrete pavements. The concept of zero-maintenance jointed plain concrete pavements” was iterated in this study for long-lasting, well-performing portland cement concrete pavement sections. The scope of the study was limited to a brief literature survey, pavement performance data collection from many counties, cities, and primary and interstate roads in Iowa, field visits to many selected pavement sites, and analysis of the collected data. No laboratory orfield testing was conducted for this phase of the project. A problem statement with a research plan was created that could be used to guide the second phase of the project.

Assessment of Dowel Bar Research, August 2002

This report presents the latest technological gaps in dowel bar research based upon completed and ongoing dowel bar research from across the nation. In order to obtain this collection of information about dowel bars, a search was conducted on a nationwide level. The technological gaps and duplications of the research were then determined. In addition, this report also provides a brief annotated bibliography of all sources used to determine the gaps in technology and knowledge for dowel bar and alternative dowel bar topics as applied to highway pavements.

Enlgish and Spanish Terms for Concrete Paving Workers, November 2004

Proper storage practices are critical to protect materials from intermingling, contamination, or degradation, and to maintain consistent aggregate gradation throughout a project. Concrete Paving Workforce Reference no.4. Spanish version.

Concrete Materials Storage, Mixing and Delivery, November 2004

Proper storage practices are critical to protect materials from intermingling, contamination, or degradation, and to maintain consistent aggregate gradation throughout a project. Concrete Paving Workforce Reference no.1

Concrete Paving site Preparation and Construction, November 2004

Proper storage practices are critical to protect materials from intermingling, contamination, or degradation, and to maintain consistent aggregate gradation throughout a project. Concrete Paving Workforce Reference no.2

Concrete Pavement Joint Sawing, Cleaning, and Sealing, November 2004

Proper storage practices are critical to protect materials from intermingling, contamination, or degradation, and to maintain consistent aggregate gradation throughout a project. Concrete Paving Workforce Reference no.3

Stringless Portland Cement Concrete Paving, February 2004

This report describes results from a study evaluating the use of stringless paving using a combination of global positioning and laser technologies. CMI and Geologic Computer Systems developed this technology and successfully implemented it on construction earthmoving and grading projects. Concrete paving is a new area for considering this technology. Fred Carlson Co. agreed to test the stringless paving technology on two challenging concrete paving projects located in Washington County, Iowa. The evaluation was conducted on two paving projects in Washington County, Iowa, during the summer of 2003. The research team from Iowa State University monitored the guidance and elevation conformance to the original design. They employed a combination of physical depth checks, surface location and elevation surveys, concrete yield checks, and physical survey of the control stakes and string line elevations. A final check on profile of the pavement surface was accomplished by the use of the Iowa Department of Transportation Light Weight Surface Analyzer (LISA). Due to the speed of paving and the rapid changes in terrain, the laser technology was abandoned for this project. Total control of the guidance and elevation controls on the slip-form paver were moved from string line to global positioning systems (GPS). The evaluation was a success, and the results indicate that GPS control is feasible and approaching the desired goals of guidance and profile control with the use of three dimensional design models. Further enhancements are needed in the physical features of the slipform paver oil system controls and in the computer program for controlling elevation.

Just the Facts for 2004

The information in “Just the Facts for 2004” is a snapshot of the workforce, collected, compiled, and presented in a format that will aid agencies and decision makers in strategic planning. In many cases, data cover a number of years and are presented to give the reader a sense of trends. While the Department of Administrative Services (DAS), Human Resource Enterprise (HRE) wants to present data in its purist form so readers can draw their own conclusions, we also have a responsibility to clarify anything that may be confusing or misleading. It is important to highlight workforce trends and explain their significance to the work of Iowa state government. The following chapter summaries are intended to do that.

The Conservation Reserve Program in the Presence of a Working Land Alternative: Implications for Environmental Quality, Program Participation, and Income Transfer, August 2005

The United States has invested large sums of resources in multiple conservation programs for agriculture over the past century. In this paper we focus on the impacts of program interactions. Specifically, using an integrated economic and bio-physical modeling framework, we consider the impacts of the presence of working land programs on a land retirement for an important agricultural region—the Upper Mississippi River Basin (UMRB). Compared to a land retirement only program, we find that the presence of a working land program for conservation tillage results in significantly lower predicted signups for land retirement at a given rental rate. We also find that the presence of both a large working land and land retirement program can result in more environmental benefits and income transfers than a land retirement only program can achieve.

Livestock Revenue Insurance, November 2000

This study outlines several possible structures for livestock revenue insurance. The policies take the form of an exotic option—an Asian basket option. The actuarially fair premiums for these policies are equal to the prices of the options they represent. Due to the complexity of pricing Asian basket options, we have combined two techniques for pricing options to reach the actuarially fair premiums. Projected premiums, producer welfare, and program efficiency are evaluated for the insurance products and existing market tools. Using efficiency ratios and certainty equivalent returns, we compare the insurance policies to strategies involving existing futures and options.

Stochastic Dynamic Northern Corn Rootworm Population Model, January 2000

A complete life cycle model for northern corn rootworm, Diabrotica barberi Smith and Lawrence, is developed using a published single-season model of adult population dynamics and data from field experiments. Temperature-dependent development and age-dependent advancement determine adult population dynamics and oviposition, while a simple stochastic hatch and density-dependent larval survival model determine adult emergence. Dispersal is not modeled. To evaluate the long-run performance of the model, stochastically generated daily air and soil temperatures are used for 100-year simulations for a variety of corn planting and flowering dates in Ithaca, NY, and Brookings, SD. Once the model is corrected for a bias in oviposition, model predictions for both locations are consistent with anecdotal field data. Extinctions still occur, but these may be consistent with northern corn rootworm metapopulation dynamics.

Generation of Simulated Daily Precipitation and Air and Soil Temperatures, January 2000

This paper describes a maximum likelihood method using historical weather data to estimate a parametric model of daily precipitation and maximum and minimum air temperatures. Parameter estimates are reported for Brookings, SD, and Boone, IA, to illustrate the procedure. The use of this parametric model to generate stochastic time series of daily weather is then summarized. A soil temperature model is described that determines daily average, maximum, and minimum soil temperatures based on air temperatures and precipitation, following a lagged process due to soil heat storage and other factors.