Chemical Stabilization and Physicochemical Properties of Soils, HR-97, Special Report, 1966

This project was initiated to gain a better understanding of the phenomena which affect the engineering behavior of soils containing colloidal size particles and to find chemical methods of treatment which could improve the engineering performance of such soils.

Chemical Stabilization and Physicochemical Properties of Soils, HR-97, Final Report, 1966

This project was initiated to gain a better understanding of the phenomena which affect the engineering behavior of soils containing colloidal size particles and to find chemical methods of treatment which could improve the engineering performance of such soils.

Development of a Laboratory Durability Test for Asphalts, HR-124, 1967

Fruitful research on durability of paving asphalts may come from two approaches: The improvement of the asphalt for durability; The development of relatively rapid laboratory tests which will enable the design engineer to select or to specify an asphalt based on quality and to make a correct estimate of the service life of a selected asphalt when used in a specific paving mixture. Research Project HR-124, "Development of a Laboratory Durability Test for Asphalts," sponsored by the Iowa Highway Research Board is in the second category and was intended to be the initial stage of an overall study in the development of a durability test for paving asphalts.

Behavior of Granular Materials Under Triaxial Compression with Pulsating Deviator Stress, HR-131, Special Report

Behavior of granular material subjected to repeated load triaxial compression tests is characterized by a model based on rate process theory. Starting with the Arrhenius equation from chemical kinetics, the relationship of temperature, shear stress, normal stress and volume change to deformation rate is developed. The proposed model equation includes these factors as a product of exponential terms. An empirical relationship between deformation and the cube root of the number of stress applications at constant temperature and normal stress is combined with the rate equation to yield an integrated relationship of temperature, deviator stress, confining pressure and number of deviator stress applications to axial strain. The experimental program consists of 64 repeated load triaxial compression tests, 52 on untreated crushed stone and 12 on the same crushed stone material treated with 4% asphalt cement. Results were analyzed with multiple linear regression techniques and show substantial agreement with the model equations. Experimental results fit the rate equation somewhat better than the integrated equation when all variable quantities are considered. The coefficient of shear temperature gives the activation enthalpy, which is about 4.7 kilocalories/mole for untreated material and 39.4 kilocalories/mole for asphalt-treated material. This indicates the activation enthalpy is about that of the pore fluid. The proportionality coefficient of deviator stress may be used to measure flow unit volume. The volumes thus determined for untreated and asphalt-treated material are not substantially different. This may be coincidental since comparison with flow unit volumes reported by others indicates flow unit volume is related to gradation of untreated material. The flow unit volume of asphalt-treated material may relate to asphalt cement content. The proposed model equations provide a more rational basis for further studies of factors affecting deformation of granular materials under stress similar to that in pavement subjected to transient traffic loads.

State-of-the-Art Methods for Design of Integral Bridge Abutments, HR-227, 1981

The routine use of integral abutments to tie bridge superstructures to foundation piling began in this country about 30 years ago. Kansas, Missouri, Ohio, North Dakota, and Tennessee were some of the early users. This method of construction has steadily grown more popular. Today more than half of the state highway agencies have developed design criteria for bridges without expansion joint devices.

Development of an Economic Dust Palliative for Limestone Surfaced Secondary Roads, HR-297, Progress Report, 1988

Research activities during this period concentrated on continuation of field and laboratory testing for the Dallas County test road. Stationary ditch collection of dust was eliminated because of inconsistent data, and because of vandalism to collectors. Braking tests were developed and initiated to evaluate the influence of treatments on braking and safety characteristics of the test sections. Dust testing was initiated for out of the wheelpath conditions as well as in the wheelpath. Contrary to the results obtained during the summer and fall of 1987, the 1.5 percent bentonite treatment appears to be outperforming the other bentonite treated sections after over a year of service. Overall dust reduction appears to average between 25 to 35 percent. Dallas County applied 300 tons per mile of class A roadstone maintenance surfacing to the test road in August 1988. Test data indicates that the bentonite is capable of interacting and functioning to reduce dust generation of the new surfacing material. Again, the 1.5 percent bentonite treatment appeared the most effective. The fine particulate bonding and aggregation mechanism of the bentonite appears recoverable from the environmental effects of winter, and from alternating wet and dry road surface conditions. The magnesium chloride treatment appears capable of long-term (over one year) dust reduction and exhibited an overall average reduction in the range of 15 to 30 percent. The magnesium chloride treatment also appears capable of interacting with newly applied crushed stone to reduce dust generation. Two additional one mile test roads were to have been constructed early this year. Due to an extremely dry spring and summer, construction scheduling was not possible until August. This would have allowed only minimal data collection. Considering this and the fact that this was an atypically dry summer, it was our opinion that it would be in the best interest of the research project to extend the project (at no additional cost) for a period of one year. The two additional test roads will be constructed in early spring 1989 in Adair and Marion counties.

Evaluation of the Chemical Durability of Iowa Fly Ash Concretes, HR-327, Phase I Progress Report, 1991

The following report summarizes research activities conducted on Iowa Department of Transportation Project HR-327, for the period April 1, 1990 through March 31, 1991. The purpose of this research project is to investigate how fly ash influences the chemical durability of portland cement based materials. The goal of this research is to utilize the empirical information obtained from laboratory testing to better estimate the durability of portland cement concrete pavements (with and without fly ash) subjected to chemical attack via the natural environment or the application of deicing salts. This project is being jointly sponsored by the Iowa Department of Transportation and the Iowa Fly Ash Affiliate Research group. The research work is also being cooperatively conducted by Iowa State University and Iowa Department of Transportation research personnel. Researchers at Iowa State University are conducting the paste and mortar studies while Iowa Department of Transportation researchers are conducting the concrete study.

Drivers' Behavior at Railroad Grade Crossings: Before and After Safety Campaign, HR-335, Survey Data Summaries, 1992

Summaries of the data gathered for this project.

Ultra Thin PCC Overlays, HR-559, Construction Report, 1995

A 11.6 km (7.2 mi.) portion of IA 21 in Iowa County from the junction of US 6 north to the junction of IA 212, was selected for the research project. The project was divided into 65 different test sections of a PCC overlay of an existing asphalt concrete (AC) surface with thicknesses of 50 mm (2 in.), 100 mm (4 in.), 150 mm (6 in.), and 200 mm (8 in.). The joint spacings for these sections were 0.6 m (2 ft.), 1.2 m (4 ft.), 1.8 m (6 ft.), 3.7 m (12 ft.), and 4.6 m (15 ft.). Joints were sealed if the thickness of the pavement was over 100 mm (4 in.), unless specified. Two types of polypropylene fibers, monofilament and fibrillated, were added to the conventional PCC mix for designated sections. Three additional sections consisted of an asphalt overlay for comparison with the concrete overlay. Three different base preparations were used on the project, consisting of: patching and scarifying, patching only, and cold-in-place recycling. Sensors were placed in various test sections to measure the temperature and strain during and after construction of the overlay. Pullout tests were also conducted at various locations. Beams cylinders were made for each of the PCC mixes and tested for flexural and compressive strengths. Evaluation of the performance will be conducted through December 31, 1999.

Evaluation of Bond Retainage in Portland Cement Concrete Overlays by Infrared Thermography and Ground Penetrating Radar, HR-537, 1988

The purpose of this project was to evaluate the location and quantities of debonding in selected portland cement concrete (PCC) overlays. The project entailed an infrared thermographic survey and a ground penetrating radar survey of the PCC overlays to locate areas of debonding between the overlays and the original pavement. An infrared scanner is capable of locating these areas because of the temperature differential which is established between bonded and debonded areas under certain environmental conditions. A conventional video inspection of the top surface of the pavement was also completed in conjunction with the infrared thermographic survey to record the visual condition of the pavement surface. The ground penetrating radar system is capable of locating areas of debonding by detecting return wave forms generated by changes in the dielectric properties at the PCC overlay original pavement interface. This report consists of two parts; a text and a set of plan sheets. The text summarizes the procedures, analyses and conclusions of the investigation. The plan sheets locate specific areas of debonding, as identified through field observations.

Time-Dependent Deformation of Non-Composite and Composite Sand-Lightweight Prestressed Concrete Structures, Phase 1, HR-137, 1969

Presented in this report is an investigation of the use of "sand-lightweight" concrete in prestressed concrete structures. The sand-lightweight concrete consists of 100% sand substitution for fines, along with Idealite coarse and medium lightweight aggregate and Type I Portland Cement.

Creep and Shrinkage Properties of Lightweight Concrete Used in the State of Iowa, HR-136, Phase I, 1968

In February of 1968 a cooperative research project by the Iowa State Highway Commission (Project No. HR-136) and the University of Iowa, Iowa City, Iowa was initiated in order to determine experimentally the creep and shrinkage characteristics of lightweight-aggregate concrete used in the State of Iowa. This report is concerned with Phase 1 of the Project as described in the Prospectus for the project submitted in November of 1967: "The State Highway Commission is planning to conduct pilot studies in prestressed-lightweight structures fabricated with materials that are proposed for use in bridge structures in the near future. Thus, Phase will have as its immediate objective, investigating the materials to be used in the above mentioned pilot studies.” (1) The work described in this report was also carried out in conjunction with a second cooperative project: "Time-Dependent Camber and Deflection of Non-Composite and Composite Lightweight-Prestressed Concrete Beams" (Project No. HR-137).

Evaluation of control devices for asphalt pavement recycling operations : summary report for research project HR-188, 1982

The objective of the research project was to seek acceptable solutions to the air pollution problem created in the asphalt recycling process using modified conventional equipment.

Undersökning av dopning i organiska dioder och solceller

Organiska solceller har gjort stora framsteg med avseende på effektivitet och stabilitet under det senaste årtiondet. Oavsiktlig dopning är ett ofta förekommande fenomen i organiska halvledare. Orenheter och defekter i halvledarmaterialet kan ge upphov till dopning. Dessutom kan organiska halvledare dopas över tid då de kommer i kontakt med syre eller fukt. I takt med att andra egenskaper optimeras och effektiviteten stiger blir dopningen en allt viktigare förlustprocess att ta i beaktande i organiska solceller. Målet med detta arbete har varit att bättre förstå dopningens inverkan på organiska dioder och solceller. Tanken var att med hjälp av två olika dopningsmolekyler åstadkomma avsiktlig dopning och på så sätt kontrollerat undersöka och skapa en bättre förståelse av hur dopningen påverkar egenskaperna hos organiska halvledare i dioder och solceller. För att undersöka dopningen har en mätmetod som baserar sig på laddningsextraktion med hjälp av en linjärt ökande spänning, kallad CELIV, använts. Teorin för mätmetoden har utvecklats för att analysera godtyckliga dopningsprofiler och för att ta i beaktande dopningsprofilen vid bestämning av mobiliteten. Metoden har, genom de experiment som utförts, bekräftats fungera väl för undersökning av dopning i organiska tunnfilmsdioder. De två dopningsmolekyler som använts har testats framgångsrikt för dopning av polymererna P3HT och PBTTT. Under arbetets gång kunde en viktig orsak till oavsiktlig dopning identifieras. Som selektivt håltransportlager vid anoden är molybdentrioxid ett av de mest använda materialen. I detta arbete visas att molekyler från ett tunt lager av molybdentrioxid diffunderar in i halvledarlagret och orsakar dopning. Dopningen i P3HT:PCBM till följd av ett molybdentrioxidlager är så hög att även tunna solceller, kring 100 nm, kommer att påverkas negativt på grund av ökad rekombination. Dopningen till följd av diffusion av molybdentrioxid är ett resultat som visar på ett behov att hitta nya alternativa material för håltransport. Ett alternativ kunde vara att använda kraftigt dopade organiska halvledare. För detta ändamål kan den avsiktliga dopning som här testats vara relevant. De experimentella resultat som ingår i denna avhandling bekräftar att CELIV-metoden lämpar sig väl för att mäta dopningskoncentration och dopningsprofiler i organiska dioder samtidigt som man kan erhålla information om laddningstransporten i halvledarlagret.