Improved Asphalt Surfaces and Asphalt Resurfacing Performance through Crack Maintenance, HR-213, 1987

In 1980, a Vanguard High Pressure Water Blaster capable of providing 10 gallons of water per minute at 2000 psi was purchased to evaluate water blasting as a crack cleaning method prior to crack filling on asphalt concrete pavements. Afer some iniital trials demonstrated its effectiveness of removing dirt, debris and vegetation, it was included in joint and crack maintenance research on Iowa 7 in Webster County. The objective of the research was to evaluate six crack preparation methods and seven "sealant" materials. The cleaning and sealing was performed in the spring of 1983. Visual evaluations of the performance were made in the fall of 1983 and spring of 1985. Compressed air and/or high pressure water did not adequately prepare cracks less than 3/8 inch wide. Routing or sawing was necessary to provide a sealant reservoir. The water blaster was more effective than compressed air in removing dirt, debris and vegetation but this did not yield significant improvement in sealant adhesion or longevity. Periodic crack filling is necessary on ACC surfaces throughout the remaining life of the pavement.

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.

Using the Air Void Anal Analyzer for Real-Time Quality Control Adjustments in the Field, November 2004

The air void analyzer (AVA) with its independent isolation base can be used to accurately evaluate the air void system—including volume of entrained air, size of air voids, and distribution of air voids—of fresh portland cement concrete (PCC) on the jobsite. With this information, quality control adjustments in concrete batching can be made in real time to improve the air void system and thus increase freeze-thaw durability. This technology offers many advantages over current practices for evaluating air in concrete.

Air Quality,

The Iowa Department of Economic Development (IDED) is committed to assisting economic developers as they advise businesses with new projects and expansions. IDED and the Iowa Department of Natural Resources (IDNR) have developed this fact sheet as a guide to help a business or project meet state and federal air quality regulations.

Evaluation of the RapidAir 457 Air Void Analyzer, March 2012

An adequate air void system is imperative to produce concrete with freeze-thaw durability in a wet freeze environment such as found in Iowa. Specifications rely on a percentage of air obtained in the plastic state by the pressure meter. Actual, in place air contents, of some concrete pavements in Iowa, have been found with reduced air content due to a number of factors such as excessive vibration and inadequate mixing. Determining hardened air void parameters is a time consuming process involving potential for human error. The RapidAir 457 air void analyzer is an automated device used to determine hardened air void parameters. The device is used in Europe and has been shown to quickly produce accurate and repeatable hardened air results. This research investigates how well the RapidAir 457 results correlate to plastic air content and the image analysis air technique. The repeatability and operator variation were also investigated, as well as, the impact of aggregate porosity and selection of threshold value on hardened air results.

Concrete Pavement Mixture Design and Analysis (MDA): Assessment of Air Void System Requirements for Durable Concrete, TPF-5(205), 2012

Concrete will suffer frost damage when saturated and subjected to freezing temperatures. Frost-durable concrete can be produced if a specialized surfactant, also known as an air-entraining admixture (AEA), is added during mixing to stabilize microscopic air voids. Small and well-dispersed air voids are critical to produce frost-resistant concrete. Work completed by Klieger in 1952 found the minimum volume of air required to consistently ensure frost durability in a concrete mixture subjected to rapid freezing and thawing cycles. He suggested that frost durability was provided if 18 percent air was created in the paste. This is the basis of current practice despite the tests being conducted on materials that are no longer available using tests that are different from those in use today. Based on the data presented, it was found that a minimum air content of 3.5 percent in the concrete and 11.0 percent in the paste should yield concrete durable in the ASTM C 666 with modern AEAs and low or no lignosulfonate water reducers (WRs). Limited data suggests that mixtures with a higher dosage of lignosulfonate will need about 1 percent more air in the concrete or 3 percent more air in the paste for the materials and procedures used. A spacing factor of 0.008 in. was still found to be necessary to provide frost durability for the mixtures investigated.

Air Formed Arch Culvert Construction - Washington County, HR-313, 1994

Iowa's secondary roads contain nearly 15,000 bridges which are less than 40 ft (12.2 m) in length. Many of these bridges were built several decades ago and need to be replaced. Box culvert construction has proven to be an adequate bridge replacement technique. Recently a new bridge replacement alternative, called the Air-O-Form method, has emerged which has several potential advantages over box culvert construction. This new technique uses inflated balloons as the interior form in the construction of an arch culvert. Concrete was then shotcreted onto the balloon form. The objective of research project HR-313 was to construct an air formed arch culvert to determine the applicability of the Air-O-Form technique as a county bridge replacement alternative. The project had the following results: The Air-O-Form method can be used to construct a structurally sound arch culvert; and the method must become more economical if it is to compete with box culverts. Continued monitoring should be conducted in order to evaluate the long-term performance of the Air-O-Form method.

Air Formed Arch Culvert Construction - Crawford County, HR-314, 1995

Iowa's secondary road network contains nearly 15,000 bridges which are less than 12 m (40 ft) long. Many of these bridges were built several decades ago and need to be replaced. Box culvert construction has proven to be an adequate bridge replacement technique. An alternative to box culverts is the Air-O-Form method of arch culvert construction. The Air-O-Form method has several potential advantages over box culvert construction. The new technique uses inflated balloons as the interior form in the construction of an arch culvert. Concrete is then shotcreted onto the balloon form to complete the arch culvert. The objective of the research project was to construct an air formed arch culvert to determine its applicability as an alternative county bridge replacement technique. The project had the following results: (1) The Air-O-Form method can be used to construct a structurally sound arch culvert; and (2) The method must become more economical if it is to compete with box culverts.

Evaluation of Air Pollution Control Devices for Asphalt Pavement Recycling Operations, HR-188, Progress Report, 1977

This report discusses the asphalt pavement recycling project designated Project HR-188 in Kossuth County, Iowa. Specific objectives were: (a) to determine the effectiveness of drum mixing plant modifications designed to control air pollution within limits specified by the Iowa Department of Environmental Quality; (b) to assess the impact of varying the proportions of recycled and virgin aggregates, (c) to assess the impact of varying the production rate of the plant, and (d) to assess the impact of varying the mixing temperature. The discussion includes information on the proposed use of research funds, project location and description, the project planning conference, plan development, bid letting, asphalt plant configuration, actual plant operation, why this method is successful, probable process limitations, pollution results, recycled pavement test results, and the cost of virgin vs. recycled asphalt pavements.

Image Analysis for Evaluating Air Void Parameters of Concrete, HR-396, 1998

This research project investigated the use of image analysis to measure the air void parameters of concrete specimens produced under standard laboratory conditions. The results obtained from the image analysis technique were compared to results obtained from plastic air content tests, Danish air meter tests (also referred to as Air Void Analyzer tests), high-pressure air content tests on hardened concrete, and linear traverse tests (as per ASTM C-457). Hardened concrete specimens were sent to three different laboratories for the linear traverse tests. The samples that were circulated to the three labs consisted of specimens that needed different levels of surface preparation. The first set consisted of approximately 18 specimens that had been sectioned from a 4 in. by 4 in. by 18 in. (10 cm by 10 cm by 46 cm) beam using a saw equipped with a diamond blade. These specimens were subjected to the normal sample preparation techniques that were commonly employed by the three different labs (each lab practiced slightly different specimen preparation techniques). The second set of samples consisted of eight specimens that had been ground and polished at a single laboratory. The companion labs were only supposed to retouch the sample surfaces if they exhibited major flaws. In general, the study indicated that the image analysis test results for entrained air content exhibited good to strong correlation to the average values determined via the linear traverse technique. Specimens ground and polished in a single laboratory and then circulated to the other participating laboratories for the air content determinations exhibited the strongest correlation between the image analysis and linear traverse techniques (coefficient of determination, r-squared = 0.96, for n=8). Specimens ground and polished at each of the individual laboratories exhibited considerably more scatter (coefficient of determination, r-squared = 0.78, for n=16). The image analysis technique tended to produce low estimates of the specific surface of the voids when compared to the results from the linear traverse method. This caused the image analysis spacing factor calculations to produce larger values than those obtained from the linear traverse tests. The image analysis spacing factors were still successful at distinguishing between the frost-prone test specimens and the other (more durable) test specimens that were studied in this research project.

Durability of Concrete as Affected by Variations in Air and W/C Ratio, R-258, 1975

Many times during the past four years we have seen ranges in the durability factor for a single coarse aggregate source that were too great to be explained by variations in the coarse aggregate alone. The durability test (ASTM C 666 Method B) as presently used is a test of the concrete system rather than that of a particular coarse aggregate. An informal study of current durability factor data indicates that w/c ratio and/or percentage of air may be critical to beam growth and durability factor. The purpose of this project, R-258, is to determine the extent w/c ratio and air content variations have on beam growth and durability factor when other factors including coarse aggregate gradation are held constant.

Fatigue Behavior of Air-Entrained Concrete, HR-183, 1977

When a material fails under a number of repeated loads, each smaller than the ultimate static strength, a fatigue failure is said to have taken place. Many studies have been made to characterize the fatigue behavior of various engineering materials. The results of some of these studies have proved invaluable in the evaluation and prediction of the fatigue strength of structural materials. Considerable time and effort has gone into the evaluation of the fatigue behavior of metals. These early studies were motivated by practical considerations: The first fatigue tests were performed on materials that had been observed to fail after repeated loading of a magnitude less than that required for failure under the application of a single load. Mine-hoist chains, railway axles, and steam engine parts were among the first structural components to be recognized as exhibiting fatigue behavior. Since concrete is usually subjected to static loading rather than cyclic loading, need for knowledge of the fatigue behavior of concrete has lagged behind that of metals. One notable exception to this, however, is in the area of highway and airfield pavement design. Due to the fact that the fatigue behavior of concrete must be understood in the design of pavements and reinforced concrete bridges, highway engineers have provided the motivation for concrete fatigue studies since the 1920's.

Fatigue Behavior of Air-Entrained Concrete: Phase II, HR-197, 1979

When a material fails under a number of repeated loads, each smaller than the ultimate static strength, a fatigue failure is said to have taken place. Many studies have been made to characterize the fatigue behavior of various engineering materials. The results of some of these studies have proved invaluable in the evaluation and prediction of the fatigue strength of structural materials. Considerable time and effort have gone into the evaluation of the fatigue behavior of metals. These early studies were motivated by practical considerations: the first fatigue tests were performed on materials that had been observed to fail after repeated loading of a magnitude less than that required for failure under the application of a single load. Mine-hoist chains (1829), railway axles (1852), and steam engine parts were among the first structural components to be recognized as exhibiting fatigue behavior. Since concrete is usually subjected to static loading rather than cyclic loading, need for knowledge of the fatigue behavior of concrete has lagged behind that of metals. One notable exception to this, however, is in the area of highway and airfield pavement design. Due to the fact that the fatigue behavior of concrete must be understood in the design of pavements and reinforced concrete bridges, highway engineers have provided the motivation for concrete fatigue studies since the 1920s.

2014 Iowa Commercial Air Service Retention and Expansion Committee - Plan

Senate File 2355 Sec. 19 (Iowa Code §328.13) created a commercial air service retention and expansion committee within the aviation office of the department of transportation. The membership of the committee consisted of the director or the director’s designee; the managers of each airport in Iowa with commercial air service; two members of the senate, one appointed by the majority leader of the senate and one appointed by the minority leader of the senate; and two members of the house of representatives, one appointed by the speaker of the house and one appointed by the minority leader of the house. The committee was to develop a plan by December 31, 2014 for the retention and expansion of passenger air service in Iowa. The committee is to meet as the committee deems necessary to assess progress in implementing the plan and, if necessary, to update the plan.

Concrete Pavement Mixture Design and Analysis (MDA): Evaluation of Foam Drainage Test to Measure Air Void Stability in Concrete

The stability of air bubbles in fresh concrete can have a profound influence of the potential durability of the system, because excessive losses during placement and consolidation can compromise the ability of the mixture to resist freezing and thawing. The stability of air void systems developed by some air entraining admixtures (AEAs) could be affected by the presence of some polycarboxylate-based water reducing admixtures (WRAs). The foam drainage test provides a means of measuring the potential stability of air bubbles in a paste. A barrier to acceptance of the test was that there was little investigation of the correlation with field performance. The work reported here was a limited exercise seeking to observe the stability of a range of currently available AEA/WRA combinations in the foam drainage test; then, to take the best and the worst and observe their stabilities on concrete mixtures in the lab. Based on the data collected, the foam drainage test appears to identify stable combinations of AEA and WRA.