Thermoset Composite Concrete Reinforcement, HR-325, Part 1, 1992

The feasibility of substituting fibercomposite (FC) (thermoset) pavement dowels for steel pavement dowels was investigated in this research project. Load transfer capacity, flexural capacity, and material properties were examined. The objectives of Part 1 of this final report included the shear behavior and strength deformations of FC dowel bars without aging. Part 2 will contain the aging effects. This model included the effects of modulus of elasticity for the pavement dowel and concrete, dowel diameter, subgrade stiffness, and concrete compressive strength. An experimental investigation was carried out to establish the modulus of dowel support which is an important parameter for the analysis of dowels. The experimental investigation included measured deflections, observed behavioral characteristics, and failure mode observations. An extensive study was performed on various shear testing procedures. A modified Iosipescu shear method was selected for the test procedure. Also, a special test frame was designed and fabricated for this procedure. The experimental values of modulus of support for shear and FC dowels were used for arriving at the critical stresses and deflections for the theoretical model developed. Different theoretical methods based on analyses suggested by Timoshenko, Friberg, Bradbury, and Westergaard were studied and a comprehensive theoretical model was developed. The fibercomposite dowels were found to provide strengths and behavioral characteristics that appear promising as a potential substitute for steel dowels.

Evaluation of Carbonate Aggregate Using X-Ray Analysis, HR-266, 1989

Iowa has more than 13,000 miles of portland cement concrete (PCC) pavement. Some pavements have performed well for over 50 years, while others have been removed or overlaid due to the premature deterioration of joints and cracks. Some of the premature deterioration is classical D-cracking, which is attributed to a critically saturated aggregate pore system (freeze-thaw damage). However, some of the premature deterioration is related to adverse chemical reactivity involving carbonate coarse aggregate. The objective of this paper is to demonstrate the value of a chemical analysis of carbonate aggregate using X-ray equipment to identify good or poor quality. At least 1.5% dolomite is necessary in a carbonate aggregate to produce a discernible dolomite peak. The shift of the maximum-intensity X-ray diffraction dolomite d-spacing can be used to predict poor performance of a carbonate aggregate in PCC. A limestone aggregate with a low percentage of strontium (less than 0.013) and phosphorus (less than 0.010) would be expected to give good performance in PCC pavement. Poor performance in PCC pavement is expected from limestone aggregates with higher percentages (above 0.05) of strontium.

Effects of Deicing Salt Trace Compounds on Deterioration of Portland Cement Concrete, HR-271, 1987

A study was made of the detrimental effects of trace amounts of calcium sulfate (occurring naturally in halite deposits used for deicing) on portland cement concrete pavements. It was found that sulfate introduced as gypsum with sodium chloride in deicing brines can have detrimental effects on portland cement mortar. Concentrations of sulfate as low as 0.5% of the solute rendered the brine destructive. Conditions of brine application were critical to specimen durability. The mechanisms of deterioration were found to be due to pore filling resulting from compound formation and deposition. A field evaluation of deteriorating joints suggests that the sulfate phenomena demonstrated in the laboratory also operates in the field. A preliminary evaluation was made of remedies: limits on sulfates, fly ash admixtures, treatment of existing pavement, and salt treatments. This report gives details of the research objectives, experimental design, field testing, and possible solutions. Recommendations for further study are presented.

Iowa Motorcycle Ride Meter, HR-1019, 1980

The Iowa Department of Transportation (Iowa DOT) through the Highway Division is responsible for the design, construction and maintenance of roadways that will provide a high level of serviceability to the motorist. First, the motorist expects to be able to get where he wants to go, but now he also demands a minimum level of comfort. In the construction of new roadways, the public is quick to express dissatisfaction with rough pavements. The Highway Division of the Iowa DOT (formerly Iowa State Highway Commission) has a specification which requires a "smooth-riding surface". For over 40 years, new portland cement concrete (pcc) pavement has been checked with a 10-foot rolling straightedge. The contractor is required to grind, saw or mill off all high spots that deviate more than 1/8" from the 10-foot straight line. Unfortunately, there are instances where a roadway that will meet the above criteria does not provide a "smooth-riding surface". The roadway may have monger undulations (swales) that result in an undesirable ride. The objective of this project was to develop a repeatable, reliable time stable, lightweight test unit to measure the riding quality of pcc pavement at normal highway speed the day after construction.

Bridge Deck Rehabilitation Rebonding a Delaminated PCC Overlay By Epoxy Injection, HR-1036, 1989

The Iowa demonstration project to promote the rehabilitation of bridge deck concrete by rebonding delaminations with injected epoxy is a 150 ft x 150 ft high truss bridge on Iowa route No. 210 over Indian Creek near Maxwell in Story County (Service level D, AADT-730, Inventory Rating HS-16.9, Operating Rating HS-25). The objective of this study was to evaluate the effectiveness of repairing a delaminated bridge deck by epoxy injection, specifically a bridge deck with a delaminated portland cement concrete overlay. Observations noted during the project lead to the following conclusions: The delaminations rebonded with epoxy have remained solid through five years. The percentage of delamination has stayed essentially the same for both the epoxy injected and non-repaired areas. Epoxy injection appears to be a practical, cost effective alternative to other forms of deck rehabilitation when undertaken at the proper time. Cost effectiveness would reduce dramatically if delayed until breakouts have occurred. On the other hand it would be a slow, labor intensive process if undertaken too early when delaminations are small.

Feasibility of Using Automated Distress Data in the County Need Study, TR-418, 1998

The purpose of this project was to determine the feasibility of using pavement condition data collected for the Iowa Pavement Management Program (IPMP) as input to the Iowa Quadrennial Need Study. The need study, conducted by the Iowa Department of Transportation (Iowa DOT) every four years, currently uses manually collected highway infrastructure condition data (roughness, rutting, cracking, etc.). Because of the Iowa DOT's 10-year data collection cycles, condition data for a given highway segment may be up to 10 years old. In some cases, the need study process has resulted in wide fluctuations in funding allocated to individual Iowa counties from one study to the next. This volatility in funding levels makes it difficult for county engineers to plan and program road maintenance and improvements. One possible remedy is to input more current and less subjective infrastructure condition data. The IPMP was initially developed to satisfy the Intermodal Surface Transportation Efficiency Act (ISTEA) requirement that federal-aid-eligible highways be managed through a pavement management system. Currently all metropolitan planning organizations (MPOs) in Iowa and 15 of Iowa's 18 RPAs participate in the IPMP. The core of this program is a statewide data base of pavement condition and construction history information. The pavement data are collected by machine in two-year cycles. Using pilot areas, researchers examined the implications of using the automated data collected for the IPMP as input to the need study computer program, HWYNEEDS. The results show that using the IPMP automated data in HWYNEEDS is feasible and beneficial, resulting in less volatility in the level of total need between successive quadrennial need studies. In other words, the more current the data, the smaller the shift in total need.

Performance of a Nongrouted Thin Bonded PCC Overlay, HR-291, 1992

The use of a thin bonded concrete overlay atop an older surface has been widely incorporated for pavement rehabilitation in Iowa since the early 70's. Two test sections were constructed in 1985 on county road T61 on the Monroe-Wapello County line without the use of grout as a bonding agent to determine if adequate bond could be achieved and structural capacity uncompromised. Both test sections have performed well with one section having higher bond strengths, lower roughness values, higher structural capacity, and less debonding at the joints than the other section. Overall, both ungrouted sections have performed well under substantial truck traffic with minimal surface distress. More attention should be given, however, to rectifying apparent debonding at the joints when no grout is used as a bonding agent.

Experimental Project No. 621, Pavement Instrumentation, HR-293, 1992

This document contains a discussion of the reasons why the project did not succeed. A detailed discussion of the steps taken by the Iowa Department of Transportation to make the experiment work are contained in this document, along with recommendations for future projects.

Ammonium Phosphate/Fly Ash Road Base Construction, HR-294, 1993

The objective of this research project was to evaluate the construction and service performance of ammonium phosphate/fly ash (APFA) treated base courses of crushed fines and/or unprocessed sand. Specific test results related to construction of the test sections were included in the 1987 construction report by Iowa State University. The performance of the experimental sections is dealt with in this final report. This 1986 project demonstrated that in all cases the control sections utilizing a Type B base experienced dramatically less cracking in the surface than the APFA treated base sections. The cost per mix and subsequent surface maintenance costs for the APFA base sections, especially those having a substantial amount of limestone, were higher than the Type B base control sections. This type of construction may prove to be economical only when petroleum product costs escalate.

Reducing the Adverse Effects of Transverse Cracking, HR-217, 1984

This research was initiated to identify methods of reducing the occurrence of transverse cracking. Eight (four repetitive) research sections were established to study three variations in the asphalt concrete pavement. The first variation was the comparison of low- and high-temperature-susceptible asphalt cement (AC) from two different sources. The second variable was to saw and seal transverse joints at spacings varying from 40 to 100 ft. The third variable was to increase the AC content in the asphalt treated base by 1 percent. The research sections were constructed with relatively few problems. Crack and joint surveys have been conducted on all research sections at intervals of less than 1 year since construction. No cracking was identified after the first winter season. The sawed joints also remained sealed through the first winter. At an age of approximately 1 1/2 years there was substantial cracking of the high-temperature-susceptible AC sections and substantial failure of the sealant material in the sawed joints. After almost 4 years, the asphalt pavement constructed with the high-temperature-susceptible AC produced a crack interval of 35 ft, the low-temperature-susceptible AC yielded an interval of 170 ft, and the low-temperature-susceptible AC with an increased AC content yielded an interval of 528 ft. The Pen-Vis number is an effective measure of temperature susceptibility of asphalt cements. The frequency of transverse cracking is affected by the temperature susceptibility of the AC. An increased AC content also reduces the frequency of transverse cracking.

Bridge Deck Delamination Study Infrared Inspection, HR-244, 1982

The Iowa Department of Transportation is responsible for maintaining approximately 3800 bridges throughout the State. Of these bridges approximately 3200 have concrete decks. The remaining bridges have been constructed or repaired with a Portland Cement (P. C.) concrete overlay. Surveys of the overlays have indicated a growing incidence of delaminations and surface distress. The need to replace or repair the overlay may be dictated by the amount of delamination in the deck. Additionally, the concrete bridges are periodically inspected and scheduled for the appropriate rehabilitation. Part of this analysis is an assessment of the amount of delamination present in the deck. The ability to accurately and economically identify delamination in overlays and bridge decks is necessary to cost-effectively evaluate and schedule bridge rehabilitation. There are two conventional methods currently being used to detect delaminations. One is ref erred to as a chain drag method. The other a electro-mechanical sounding method (delamtect). In the chain drag method, the concrete surface is struck using a heavy chain. The inspector then listens to the sound produced as the surface is struck. The delaminated areas produce a dull sound as compared to nondelaminated areas. This procedure has proved to be very time consuming, especially when a number of small areas of delamination are present. With the · electro-mechanical method, the judgement of the inspector has been eliminated. A· device with three basic components, a tapping device, a sonic receiver, and a system of signal interpretation has been developed. This· device is wheeled along the deck and the instrument receives and interprets the acoustic signals generated by the instrument which in turn are reflected through the concrete. A recently developed method of detecting delaminations is infrared thermography. This method of detection is based on the difference in surface temperature which exists between delaminated and nondelaminated concrete under certain atmospheric conditions. The temperature difference can reach 5°C on a very sunny day where dry pavement exists. If clouds are present, or the pavement is wet, then the temperature difference between the delaminated and nondelaminated concrete will not be as great and therefore more difficult to detect. Infrared thermography was used to detect delaminations in 17 concrete bridge decks, 2 P. C. concrete overlays, and 1 section of continuously reinforced concrete pavement (CRCP) in Iowa. Thermography was selected to assess the accuracy, dependability, and potential of the infrared thermographic technique.

Bridge Deck Repair Using Epoxy Resin, HR-177, 1979

Research funds were approved for the purchase of equipment designed to proportion and inject epoxy resins into delaminated areas of bridge decks. Through investigation and refining of this process, it was anticipated that a maintenance procedure would be developed to delay spalling of bridge decks by "gluing down" delaminated areas before spalling occurred.

Evaluation of Fly Ash in Portland Cement Concrete Pavement in Monona County, Iowa, HR-200, 1980

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.

Evaluation of Calcium Magnesium Acetate Deicer in Scott County, HR-253, Progress Report, 1987

The field testing of the noncorrosive alternative deicing agent, calcium magnesium acetate is described. Seventy three tons were produced of one part CMA and three parts sand deicer which was field tested on I-280 from I-80 to the Mississippi River (7,000 ADT with 50% trucks). A comparative application was made with one part sand and one part sodium chloride. The study found that CMA deicer required a longer time for the pavement to reach normal conditions, and 20-25% more CMA deicer to provide the desired deicing. It was concluded that the CMA deicer was not as dependable as the sodium chloride deicing agent, and it was more difficult to clean up the equipment for spreading the CMA deicer.

Innovative Leak Test for Pavement Joint Seals, Progress Report, HR-318, 1993

Premature failure of concrete pavement contraction joint seals is an ongoing and costly problem for the Iowa Department of Transportation. Several joint seal test sections consisting of variations in sawing methods, joint cleaning techniques, sealant installation, and sealant types have been established over the past few years. Laboratory analysis and field inspections were done as a part of the tests, and core samples were taken for laboratory adhesion pull tests. Such methods often cover specifically small areas and may not expose hidden failures. Some tests are also labor-intensive and destructive, especially that of coring. An innovative, nondestructive, broad coverage joint seal tester that yields quick results has been designed and developed for evaluation of pavement joint seal performance. The Iowa vacuum joint seal tester (IA-VAC) applies a low vacuum above a joint seal that has been spray-covered with a foaming water solution. Any unsealed area or leak that exists along the joint will become quickly and clearly visible by the development of bubbles at the leak point. By analyzing the results from the IA-VAC tests, information on the number and types of leaks can be obtained; such information will help identify the source of the problem and direct efforts toward a solution.