Superpave Mix Designs for Low Volume Roads, Construction Report, TR-414, 2001

Most research current to the time of these projects was focused on use of Superpave mix designs on higher volume roads. Low volume roads have different requirements in terms of mix design, aggregate types, aggregate sources and project budgets. The purpose of this research was to determine if the Superpave mix design strategy for low volume roads was practical and economical. Eight projects were selected in five counties. The projects were completed in the summer of 1998. Performance evaluation of the resulting pavements was carried out annually. There was no significant increase in costs related to the use of Superpave. Nor were there any significant construction issues. There were some differences noted in placement and compaction in the field, but these were not serious.

A Feasibility Study on Embedded Micro-Electromechanical Sensors and Systems (MEMS) for Monitoring Highway Structures, TR-575, 2011

Micro-electromechanical systems (MEMS) provide vast improvements over existing sensing methods in the context of structural health monitoring (SHM) of highway infrastructure systems, including improved system reliability, improved longevity and enhanced system performance, improved safety against natural hazards and vibrations, and a reduction in life cycle cost in both operating and maintaining the infrastructure. Advancements in MEMS technology and wireless sensor networks provide opportunities for long-term continuous, real-time structural health monitoring of pavements and bridges at low cost within the context of sustainable infrastructure systems. The primary objective of this research was to investigate the use of MEMS in highway structures for health monitoring purposes. This study focused on investigating the use of MEMS and their potential applications in concrete through a comprehensive literature review, a vendor survey, and a laboratory study, as well as a small-scale field study. Based on the comprehensive literature review and vendor survey, the latest information available on off-the-shelf MEMS devices, as well as research prototypes, for bridge, pavement, and traffic applications were synthesized. A commercially-available wireless concrete monitoring system based on radio-frequency identification (RFID) technology and off-the-shelf temperature and humidity sensors were tested under controlled laboratory and field conditions. The test results validated the ability of the RFID wireless concrete monitoring system in accurately measuring the temperature both inside the laboratory and in the field under severe weather conditions. In consultation with the project technical advisory committee (TAC), the most relevant MEMS-based transportation infrastructure research applications to explore in the future were also highlighted and summarized.

Impact of Deck Cracking on Durability, TR-405, 2000

Concrete bridge decks subjected to corrosive environment because of the application of de-icing chemical could deteriorate at a rapid rate. In an effort to minimize corrosion of the reinforcement and the corresponding delaminations and spalls, the Iowa Department of Transportation started using epoxy-coated rebars (ECR) in the top mat of reinforcing around 1976 and in both mats 10 years later. The overall objective of this research was to determine the impact of deck cracking on durability and estimate the remaining functional service life of a bridge deck. This was accomplished by conducting a literature review, visually inspecting several bridge decks, collecting and sampling test cores from cracked and uncracked areas of bridge decks, determining the extent to which epoxy-coated rebars deteriorate at the site of cracks, and evaluating the impact of cracking on service life.

Strength-Temperature Study of Fly Ash Concrete, MLR-84-6, 1984

Class A, B, and C concrete paving mixes were tested for compressive strength at 40°F and 73°F, both with and without fly ash substitution for 15% of the portland cement. Two Class C ashes and one Class F ash from Iowa approved sources were examined in each mix. The purpose of the study was to provide data on cool weather strength development of concrete paving mixes utilizing Iowa materials. In all cases except one, the fly ash concretes exhibited lower 7 and 28- day compressive strengths at 40°F than control mixes. The continuation of the October 15 cut-off date for the use of fly ash concrete is recommended.

Correlation of Locally-Based Performance of Asphalts with their Physicochemical Parameters, Task 1 Report, HR-298, 1988

This is the first report of 6 tasks to be performed in an effort to establish locally-based quality and performance criteria for asphalts, and ultimately to develop performance-related specifications based on simple physicochemical methods. Three of the most promising chemical methods (high performance liquid chromatography (HPLC), thermal analysis, and X-ray diffraction were selected to analyze 4 different types of samples. The results will indicate the fundamental asphalt property variables that directly affect the field performance in Iowa. The details of the materials and procedures employed are described, and the results of the tests are presented.

Reducing the Adverse Effects of Transverse Cracking, Construction Report, HR-217, 1981

The objective of this research project was to identify a method of reducing the adverse effect of transverse cracking and to improve the performance of asphalt pavement. The research involved three variations from the contractor's planned operation. Briefly, they were: (1) use of another asphalt cement; (2) saw and seal transverse joints; and (3) increased asphalt cement content. The following conclusions were reached: (1) an improved sealant or sealing procedure is needed if transverse joints are to be used in asphalt pavements; (2) the penetration-viscosity number (PVN) is an effective measure of the temperature susceptibility of asphalt cements; (3) the use of a high temperature susceptible asphalt cement produced severe transverse cracking; (4) the use of asphalt cements with low temperature susceptibility will reduce the frequency of transverse cracking; and (5) an increased asphalt cement content in the asphalt treated base will reduce the frequency of transverse cracking.

Freeze-Thaw Durability of Concretes with Infilling of Ettringite in Voids, Phase 2, MLR-94-9, 1997

Examination of field portland cement concrete cores, from Iowa pavements with premature deterioration, reveals extensive infilling of calcium sulfate aluminum (CSA) compound in their air voids. A previous study (Phase I) has shown some evidence of the correlation between freeze-thaw durability of concretes and ettringite infilling. To further verify the previous observation, a more extensive experimental program was conducted in this Phase 2 study. A total of 101 concrete mixes were examined. Seven cements, six fly ashes, two water reducers and three coarse aggregates were used in the concrete mixes. Specimens were under moist curing for up to 223 days before being subjected to the freeze-thaw cycling. An environmental treatment consisting of three consecutive wet [70 deg F (21 deg C) in distilled water]/dry [120 deg F (49 deg C) in oven] cycles was applied to some specimens. Immediately prior to the freeze-thaw cycling, most specimens were examined by a low-vacuum scanning electron microscope (SEM) for their microstructure. The results obtained further demonstrate the correlation between concrete freeze-thaw response and CSA compound infilling in the air voids. The extent of the infilling depends on the period of moist curing as well as the wet/dry treatment. The extent of the infilling also relates to materials used. Concrete mixes with extensive infilling are more vulnerable to the freeze-thaw attack. Based on the obtained results, material criteria on cements and fly ashes for mainline paving were proposed for minimizing potential infilling of CSA compound in concrete.

Durability of P.C. Concrete as Affected by Aggregate Size, Curing and Proportions, R-214, 1968

The durability of concrete is a most important aspect in pavement life. Deterioration of the interstate portland cement concrete pavement has prompted various studies of factors which may contribute to the durability. Studies of cores taken from deteriorated areas indicated that the larger particles of coarse aggregate may contribute greatly to the problem. This indication was mainly due to the analysis of the cracking pattern which showed that most of the cracks passed through the larger aggregates and the larger aggregate particles were more cracked than the smaller particles. The purpose of this project is to determine if the size of the coarse aggregate has a bearing on the durability of freeze and thaw beams. A secondary purpose of this project is to determine what effect the method of curing and proportions have on the durability of freeze and thaw beams.

A Study of Portland Cement Maintenance Mix and Set Accelerators, R-249, 1970

The large volume of traffic on the interstate system makes it difficult to make pavement repairs. The maintenance crew needs 4-5 hours to break out the concrete to be replaced and prepare the hole for placing new concrete. Because of this it is usually noon before the patch can be placed. Since it is desirable to remove the barricades before dark there are only 7-8 hours for the concrete to reach the required strength. There exists a need for a concrete that can reach the necessary strength (modulus of rupture = 500 psi) in 7-8 hours. The purpose of this study is to determine if type III cement and/or an accelerator can be used in an M-4 mix to yield a fast setting patch with very little shrinkage. It is recognized that calcium chloride is a corrosive material and may therefore have detrimental effects upon the reinforcing steel. The study of these effects, however, is beyond the scope of this investigation.

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.

An Investigation of Portland Cement Concrete Utilizing 70% Class V Aggregate and 30% Calcareous Coarse Aggregate, R-255, 1973

The main sources of coarse aggregate for secondary slip form paving in Southwest Iowa exhibit undesirable "D" cracking. "D" cracking is a discoloration of the concrete caused by fine, hairline cracks. These cracks are caused by the freezing and thawing of moisture inside the coarse aggregate. The cracks are often hour glass shaped, are parallel to each other, and occur along saw joints. The B-4, a typical secondary mix, utilizes 50% fine aggregate and 50% coarse aggregate. It has been proposed that a concrete mix with less coarse aggregate and more fine aggregate might impede this type of deterioration. The Nebraska Standard 47B Mix, a 70% fine aggregate, and 30% coarse aggregate mix, as used by Nebraska Department of Roads produces concrete with ultimate strengths in excess of 4500 psi but because of the higher cost of cement (it is a six bag per cubic yard mix) is not competitive with our present secondary mixes. The sands of Southwest Iowa generally have poorer mortar strengths than the average Iowa Sand. Class V Aggregate also found in Southwest Iowa has a coarser sand fraction, therefore it has a better mortar strength, but exhibits an acidic reaction and therefore must be·used with limestone. This illustrates the need to find a mix for use in Southwest Iowa that possesses adequate strength and satisfactory durability at a low cost. The purpose of this study is to determine a concrete mix with an acceptable cement content which will produce physical properties similar to that of our present secondary paving mixes.

Oils and Tars from Iowa Shales, HR-32, 1962

The inadequate supply of suitable road surfacing material in the southern part of Iowa raises the question of the possibility of utilizing certain shales abundant in this area. These carbonaceous shales commonly overlie the coal beds and may also be found as impurities in the coal seams. They constitute the "slate" which with minor amounts of coal makes up the "gob" piles at the mines. These shales frequently contain enough carbonaceous material to burn. Those which do not usually require only a relatively small amount of coal mixed with them to support combustion. As a result, the "gob" piles frequently burn. The residual shale material is frequently used locally as a road surfacing material. However, since there is no control over the burning, there is no assurance that the product is the most suitable which might be produced or that it is even uniform in its properties. To determine if a controlled burning would produce a suitable road building product economically a research project "Use of Shales as Highway Materials" (ISHC Project HR-21, IEES Project 299-S) was set up in the Iowa Engineering Experiment Station with funds provided by the Iowa State Highway Commission, This project was supervised by Charles Frush, formerly Assistant Professor of Mining Engineering at Iowa State University. The various shales were subjected to controlled burning, and the solid residues were tested for their suitability for highway use.

Studies on Soil-Aggregate-Sodium Chloride Stabilized Roads in Franklin County, Iowa, HR-33

This investigation was conducted to study the performance characteristics of low cost roadway surfaces of soil-aggregate-sodium chloride mixtures. Many roads have been successfully stabilized with sodium chloride. However, little information is available on either the properties of the road materials or the effects of sodium chloride on the materials. The performance of some of the sodium chloride stabilized roads in Franklin County, Iowa, and the performance of some near-by nonchemically treated roads has been studied. The study of sodium chloride stabilized roads was restricted to the roads in which the binder soil used in construction came from the same source. The effects of sodium chloride on some of the engineering properties of the soil and soil-aggregate mixtures used were studied in the laboratory.

Void Ratio and Shear Strength of Two Compacted Crushed Stones, Progress Report, HR-99

Triaxial compression tests of two crushed limestones of differing highway service records indicate a fundamental difference in their shear strength -- void ratio relationship. Analyses were based on stress parameters at minimum sample volume, i.e., before there was significant sample dilation due to shear. The better service record sample compacted to higher density, and had a high effective angle of internal friction and zero effective cohesion. The other sample compacted to lower density and had a lower friction angle, but gained significant stability from effective cohesion. Repeated loading-unloading cycles reduced the cohesion, apparently due to modification of the sample structure. Extrapolations of the results to zero void ratio agree with sliding friction data reported on calcite, or with triaxial parameters reported on carbonate rocks.

Evaluation of Carbide Waste Lime for Soil Stabilization, Progress Report, HR-111

A lime by-product from the manufacture of acetylene from calcium carbide will be commercially available in Iowa. Since the cost of carbide waste lime f.o.b. source is only about half that of ordinary commercial lime, this material was investigated for potential uses in soil stabilization. The by-product lime is calcium hydroxide in a water slurry with approximately 40% solid concentration. Its effectiveness at stabilizing soils was checked by comparing with commercial high-calcium and dolomitic monohydrate varieties of lime. This was done by soil strength and plasticity tests in addition to studies of the reaction products by X-ray diffraction and chemical methods.