Evaluation of Composite Pavement Unbonded Overlays: Phases I and II, April 2003

In recent years, thin whitetopping has evolved as a viable rehabilitation technique for deteriorated asphalt cement concrete (ACC) pavements. Numerous projects have been constructed and tested; these projects allow researchers to identify the important elements contributing to the projects’ successes. These elements include surface preparation, overlay thickness, synthetic fiber reinforcement usage, joint spacing, and joint sealing. Although the main factors affecting thin whitetopping performance have been identified by previous research, questions still existed as to the optimum design incorporating these variables. The objective of this research is to investigate the interaction between these variables over time. Laboratory testing and field-testing were planned in order to accomplish the research objective. Laboratory testing involved shear testing of the bond between the portland cement concrete (PCC) overlay and the ACC surface. Field-testing involved falling weight deflectometer deflection responses, measurement of joint faulting and joint opening, and visual distress surveys on the 9.6-mile project. The project was located on Iowa Highway 13 extending north from the city of Manchester, Iowa, to Iowa Highway 3 in Delaware County. Variables investigated included ACC surface preparation, PCC thickness, synthetic fiber reinforcement usage, and joint spacing. This report documents the planning, equipment selection, construction, field changes, and construction concerns of the project built in 2002. The data from this research could be combined with historical data to develop a design specification for the construction of thin, unbonded overlays.

Evaluation of Composite Pavement Unbonded Overlays: Phase III, August 2006

In recent years, thin whitetopping has evolved as a viable rehabilitation technique for deteriorated asphalt cement concrete (ACC) pavements. Numerous projects have been constructed and tested, allowing researchers to identify the important elements contributing to the projects’ successes. These elements include surface preparation, overlay thickness, synthetic fiber reinforcement usage, joint spacing, and joint sealing. Although the main factors affecting thin whitetopping performance have been identified by previous research, questions still existed as to the optimum design incorporating these variables. The objective of this research is to investigate the interaction between these variables over time. Laboratory testing and field testing were conducted to achieve the research objectives. Laboratory testing involved shear testing of the bond between the portland cement concrete (PCC) overlay and the ACC surface. Field testing involved falling weight deflectometer deflection responses, measurement of joint faulting and joint opening, and visual distress surveys on the 9.6-mile project. The project was located on Iowa Highway 13 extending north from the city of Manchester, Iowa, to Iowa Highway 3 in Delaware County. Variables investigated include ACC surface preparation, PCC thickness, slab size, synthetic fiber reinforcement usage, and joint spacing. This report documents the planning, construction, and performance of each variable in the time period from summer 2002 through spring 2006. The project has performed well with only minor distress identification since its construction.

Thin Bonded Overlay Evaluation, Construction Report, HR-559, 1999

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, the 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. Although the main factors affecting UTW performance have been identified in previous research, neither the impact that external variables have on the elements nor the element interaction have been thoroughly investigated. 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. Laboratory testing and full scale field testing were planned to accomplish the research objective. Laboratory testing involved monitoring interface strains in fabricated PCC/ACC composite test beams subjected to either static or dynamic flexural loading. Variables investigated included ACC surface preparation, PCC thickness, and synthetic fiber reinforcement usage. Field testing involved monitoring PCC/ACC interface stains and temperatures, falling weight deflectometer (FWD) deflection responses, direct shear strengths, and distresses on a 7.2 mile Iowa Department of Transportation (Iowa DOT) UTW project (HR-559). The project was located on Iowa Highway 21 between Iowa Highway 212 and U.S. Highway 6 in Iowa County, near Belle Plaine, Iowa. Variables investigated included ACC surface preparation, PCC thickness, synthetic fiber reinforcement usage, joint spacing, and joint sealing. This report documents the planning, equipment selection, and construction of the project built in 1994.

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.

Thin Bonded Overlay Evaluation, HR-559, Final Report, 2001

In 1994 the Iowa Department of Transportation constructed a 7.2-mile Portland Cement Concrete overlay project in Iowa County on Iowa Highway 21. The research work was conducted in cooperation with the Department of Civil Engineering and the Federal Highway Administration under the Iowa Highway Research Board project HR-559. The project was constructed to evaluate the performance of an ultrathin concrete overlay during a 5-year period. The experiment included variables of base surface preparation, overlay depth, joint spacing, fiber reinforcement, and the sealed or non-sealed joints. The project was instrumented to measure overlay/base interface temperatures and strains. Visual distress surveys and deflection testing were also used to monitor performance. Coring and direct shear testing was accomplished 3 times during the research period. Results of the testing and monitoring are identified in the report. The experiment was very successful and the results provide an insight into construction and design needs to be considered in tailoring a portland cement concrete overlay to a performance need. The results also indicate a method to monitor bond with nondestructive methods.

Field Evaluation of Elliptical Fiber Reinforced Polymer Dowel Performance, June 2005

Fiber reinforced polymer (FRP) composite materials are making an entry into the construction market in both buildings and pavements. The application to pavements so far has come in the form of joint reinforcement (dowels and tie bars). FRP resistance to salt corrosion in dowels has made it an alternative to standard epoxy-coated steel dowels for pavements. Iowa State University has completed a large amount of laboratory research to determine the diameter, spacing, and durability of FRP dowels. This report documents the performance of elliptical FRP dowels installed in a field situation. Ten joints were monitored in three consecutive test sections, for each of three dowel spacings (10, 12, and 15 inches) including one instrumented dowel in each test section. The modulus of dowel bar support was determined using falling weight deflectometer (FWD) testing and a loaded crawl truck. FWD testing was also used to determine load transfer efficiency across the joint. The long-term performance and durability of the concrete was also evaluated by monitoring faulting and joint opening measurements and performing visual distress surveys at each joint. This report also contains similar information for standard round, medium elliptical, and heavy elliptical steel dowels in a portion of the same highway. In addition, this report provides a summary of theoretical analysis used to evaluate joint differential deflection for the dowels.

Field Evaluation of Elliptical Fiber Reinforced Polymer Dowel Performance, June 2003

Fiber composite materials (FRP) are making an entry into the construction market in both buildings and pavements. The application to pavements comes in the form of joint reinforcement (dowels and tie bars) to date. FRP resistance to salt corrosion in dowels has made it an alternative to standard epoxy coated dowels for pavements. Iowa State University has completed a large amount of laboratory research into the determination of diameter, spacing, and durability of FRP dowels. This report documents the installation of a series of FRP elliptical-shaped dowel joints (including instrumented units) in a field situation and the beginning of a two-year study to compare laboratory results to in-service pavements. Ten joints were constructed for each of three dowel spacings of 10, 12, and 15 inches ( 254, 305, and 381 mm) with one instrumented joint in each test section. The instrumented bars will be load tested with a loaded truck and FWD testing.

Performance of Randomly Oriented, Fiber-Reinforced Roadway Soils, HR-211, 1982

Several primary techniques have been developed through which soil aggregate road material properties may be improved. Such techniques basically involve a mechanism of creating a continuous matrix system of soil and/or aggregate particles, interlocked through the use of some additive such as portland cement, lime, or bituminous products. Details by which soils are stabilized vary greatly, but they are dependent on the type of stabilizing agent and nature of the soil, though the overall approach to stabilization has the common feature that improvement is achieved by some mechanism(s) forcing individual particles to adhere to one another. This process creates a more rigid material, most often capable of resisting the influx of water during freezing, loss of strength due to high moisture content and particle dispersion during thawing, and loss of strength due to migration of fines and/or water by capillarity and pumping. The study reported herein, took a new and relatively different approach to strengthening of soils, i.e., improvement of roadway soils and/or soil-aggregate materials by structural reinforcement with randomly oriented fibers. The purpose of the study was to conduct a laboratory and field investigation into the potential of improving (a) soil-aggregate surfaced and subgrade materials, including those that are frost-prone and/or highly moisture susceptible, and (b) localized base course materials, by uniting such materials through fibrous reinforcement. The envisioned objective of the project was the development of a simple construction technique(s) that could be (a) applied on a selective basis to specific areas having a history of poor performance, or (b) used for improvement of potential base materials prior to surfacing. Little background information on such purpose and objective was available. Though the envisioned process had similarities to fibrous reinforced concrete, and to fibrous reinforced resin composites, the process was devoid of a cementitious binder matrix and thus highly dependent on the cohesive and frictional interlocking processes of a soil and/or aggregate with the fibrous reinforcement; a condition not unlike the introduction of reinforcing bars into a concrete sand/aggregate mixture without benefit of portland cement. Thus the study was also directed to answering some fundamental questions: (1) would the technique work; (2) what type or types of fibers are effective; (3) are workable fibers commercially available; and (4) can such fibers be effectively incorporated with conventional construction equipment, and employed in practical field applications? The approach to obtaining answers to these questions, was guided by the philosophy that an understanding of basic fundamentals was essential to developing a body of engineering knowledge, that would serve as the basis for eventual development of design procedures with fibrous products for the applications previously noted.

Thermoset Composite Concrete Reinforcement, HR-325, Part 2, 1992

This is the second part of the final report submitted to the Iowa Department of Transportation. Part 1 contained a comparison of unaged fiber composite and steel dowels and derivation of the appropriate theoretical model for analyzing the results. Part 2 of this final report covers the theoretical and experimental models for accelerated aging of fiber composite reinforcing bars and dowels cast in a concrete environment. Part 2 contains results from testing of unaged and aged fiber composite dowels and steel dowels, in addition to unaged and aged fiber composite reinforcing bars. Additional tests have been performed on unaged dowels (both steel and fibercomposite) to verify results from Part 1 and to keep the testing program consistent. Slight modifications have been made to the dowel specimens presented in Part 1. These modifications are noted in the Section 3.4 of this report. The flexural modulus of elasticity for the FC dowel bar given in Part 1 of the final report (Table 3. 2) was for the incorrect structural shape (non-circular cross section). The value is corrected and given in Part 2 of the final report (Table 3.4 for the.modulus of elasticity supplied by the manufacturer, and Tables 3. 5 and 3. 6 for experimentally determined modulus of elasticities) • The value in Part 1 was not used for any analysis of the FC dowel bars.

Demonstration and Field Evaluation of Alternative Portland Cement Concrete Pavement Reinforcement Materials, HR-1069, 2003

Transverse joints are placed in portland cement concrete pavements to control the development of random cracking due to stresses induced by moisture and thermal gradients and restrained slab movement. These joints are strengthened through the use of load transfer devices, typically dowel bars, designed to transfer load across the joint from one pavement slab to the next. Epoxy coated steel bars are the materials of choice at the present time, but have experienced some difficulties with resistance to corrosion from deicing salts. The research project investigated the use of alternative materials, dowel size and spacing to determine the benefits and limitations of each material. In this project two types of fiber composite materials, stainless steel solid dowels and epoxy coated dowels were tested for five years in side by side installation in a portion of U.S. 65 near Des Moines, Iowa, between 1997 and 2002. The work was directed at analyzing the load transfer characteristics of 8-in. vs. 12-in. spacing of the dowels and the alternative dowel materials, fiber composite (1.5- and 1.88-in. diameter) and stainless steel (1.5-in. diameter), compared to typical 1.5-in. diameter epoxy-coated steel dowels placed on 12-in. spacing. Data were collected biannually within each series of joints and variables in terms of load transfer in each lane (outer wheel path), visual distress, joint openings, and faulting in each wheel path. After five years of performance the following observations were made from the data collected. Each of the dowel materials is performing equally in terms of load transfer, joint movement and faulting. Stainless steel dowels are providing load transfer performance equal to or greater than epoxy-coated steel dowels at the end of five years. Fiber reinforced polymer (FRP) dowels of the sizes and materials tested should be spaced no greater than 8 in. apart to achieve comparable performance to epoxy coated dowels. No evidence of deterioration due to road salts was identified on any of the products tested. The relatively high cost of stainless steel solid and FRP dowels was a limitation at the time of this study conclusion. Work is continuing with the subject materials in laboratory studies to determine the proper shape, spacing, chemical composition and testing specification to make the FRP and stainless (clad or solid) dowels a viable alternative joint load transfer material for long lasting portland cement concrete pavements.

Demonstration and Field Evaluation of Alternative Portland Cement Concrete Pavement Reinforcement Materials, Construction Report, HR-1069, 1998

The function of dowel bars is the transfer of a load across the transverse joint from one pavement slab to the adjoining slab. In the past, these transfer mechanisms have been made of steel. However, pavement damage such as loss of bonding, deterioration, hollowing, cracking and spalling start to occur when the dowels begin to corrode. A significant amount of research has been done to evaluate alternative types of materials for use in the reinforcement of concrete pavements. Initial findings have indicated that stainless steel and fiber composite materials possess properties, such as flexural strength and corrosion resistance, that are equivalent to the Department of Transportation specifications for standard steel, 1 1/2 inch diameter dowel bars. Several factors affect the load transfer of dowels; these include diameter, alignment, grouting, bonding, spacing, corrosion resistance, joint spacing, slab thickness and dowel embedment length. This research is directed at the analysis of load transfer based on material type and dowel spacing. Specifically, this research is directed at analyzing the load transfer characteristics of: (a) 8-inch verses 12-inch spacing, and (b) alternative dowel material compared to epoxy coated steel dowels, will also be analyzed. This report documents the installation of the test sections, placed in 1997. Dowel material type and location are identified. Construction observations and limitations with each dowel material are shown.

Fibrous P.C. Concrete Overlay Research Green County, Iowa, December 1978

The Greene County, Iowa overlay project, completed in October 1973, was inspected on October 16 & 17, 1978 After five years of service The 33 fibrous concrete sections, four CRCP sections, two mesh reinforced and two plain concrete sections with doweled reinforcement were rated relative to each other on a scale of 0 t o 100. The rating was conducted by the original members of the Project Planning Committee, Iowa DOT, Iowa Counties, Federal Highway Administration, University of Illinois and industry representatives . In all , there were 23 representatives who rated this project . The 23 values were then averaged to provide a final rating number for each section. The highest panel rating (90) was assigned to the 5-inch thick , deformed barre in forced PCC sections ; an 86t o a 3-inch thick , 160 lbs. of fiber and 600 lbs . of cement on a partial bonded surface ; an 84 to the 4-inch CRC with elastic joints (bonded) and an 84 to a 4-inch mesh reinforce section. One of the major factors influencing performance appears t o be the thickness. In the fibrous concrete overlay, The greatest influences appears t o be the fiber content. Overlay Sections containing 160 1b/yd3 of Fiber are, in almost all cases , outperforming those c o n t a i n i n g 60 or 100. It is obvious at This time meth at the 3-inch thick fibrous concrete overlays are, in general, out performing the 2-inch thick sections. The performance of the fibrous concrete the overlay appears to be favorably influenced by: (1) The use of higher a spectra fiber (0.025 x 2.5 i n c h e s ) v e r s u s (0.010 x 0.022 x 1.0 inches) (2) The use of a lower cement c o n t e n t ( 600 versus 750 1b/yd3) However, The set less well defined and the improvements in overlay performance attributed to high aspect ratio fibers and low cement contents.

Fiber Arts of the Hmong, 1983

This brochure describes the textile folk art and needlework of the Hmong tribes who are from Northern China. It is a colorful and exciting addition for American admirers of fine stitching. It also tells of the history of the Hmong tribes.

Non-Corrosive Tie Reinforcing and Dowel Bars for Highway Pavement Slabs, HR-343, 1993

The use of non-metallic load transfer and reinforcement devices for concrete highway pavements is a possible alternative to avoid corrosion problems related to the current practice of steel materials. Laboratory and field testing of highway pavement dowel bars, made of both steel and fiber composite materials, and fiber composite tie rods were carried out in this research investigation. Fatigue, static, and dynamic testing was performed on full-scale concrete pavement slabs which were supported by a simulated subgrade and which included a single transverse joint. The bahavior of the full-scale specimens with both steel and fiber composite dowels placed in the test joints was monitored during several million load cycles which simulated truck traffic at a transverse joint. Static bond tests were conducted on fiber composite tie rods to determine the required embedment length. These tests took the form of bending tests which included curvature and shear in the embedment zone and pullout tests which subjected the test specimen to axial tension only. Fiber composite dowel bars were placed at two transverse joints during construction of a new concrete highway pavement in order to evaluate their performance under actual field conditions. Fiber composite tie rods were also placed in the longitudinal joint between the two fiber composite doweled transverse joints.

Innovative Solutions for Slope Stability Reinforcement and Characterization: Vol. I, TR-489, 2005

Soil slope instability concerning highway infrastructure is an ongoing problem in Iowa, as slope failures endanger public safety and continue to result in costly repair work. Characterization of slope failures is complicated, because the factors affecting slope stability can be difficult to discern and measure, particularly soil shear strength parameters. While in the past extensive research has been conducted on slope stability investigations and analysis, this research consists of field investigations addressing both the characterization and reinforcement of such slope failures. The current research focuses on applying an infrequently-used testing technique comprised of the Borehole Shear Test (BST). This in-situ test rapidly provides effective (i.e., drained) shear strength parameter values of soil. Using the BST device, fifteen Iowa slopes (fourteen failures and one proposed slope) were investigated and documented. Particular attention was paid to highly weathered shale and glacial till soil deposits, which have both been associated with slope failures in the southern Iowa drift region. Conventional laboratory tests including direct shear tests, triaxial compression tests, and ring shear tests were also performed on undisturbed and reconstituted soil samples to supplement BST results. The shear strength measurements were incorporated into complete evaluations of slope stability using both limit equilibrium and probabilistic analyses. The research methods and findings of these investigations are summarized in Volume 1 of this report. Research details of the independent characterization and reinforcement investigations are provided in Volumes 2 and 3, respectively. Combined, the field investigations offer guidance on identifying the factors that affect slope stability at a particular location and also on designing slope reinforcement using pile elements for cases where remedial measures are necessary. The research findings are expected to benefit civil and geotechnical engineers of government transportation agencies, consultants, and contractors dealing with slope stability, slope remediation, and geotechnical testing in Iowa.