Evaluation of Fly Ash Concrete Durability Containing Class II Durability Aggregates, July 1986

Fly ash was used in this evaluation study to replace 15% of the cement in Class C-3 concrete paving mixes. One Class "c" ash from Iowa approved sources was examined in each mix. Substitution rate was based on 1 to 1 basis, for each pound of cement removed 1.0 pound of ash was added. The freeze/thaw durability of the concrete studied was not adversely affected by the presence of fly ash. This study reveals that the durability of the concrete test specimens made with Class II durability aggregates was slightly increased in all cases by the substitution of cement with 15% Class "c" fly ash. In all cases durability factors either remained the same or slightly improved except for one case where the durability factor decreased from 36 to 34. The expansion decreased in all cases.

Evaluation of Fly Ash in Water Reduced Paving Mixtures, June 1985

Fly ash was used to replace 15% of the cement in C3WR and C6WR concrete paving mixes containing ASTM C494 Type A water reducin9 admixtures. Two Class C ashes and one Class F ash from Iowa approved sources were examined in each mix. When Class C ashes were used they were substituted on the basis of 1 pound of ash added for each pound of cement deleted. When Class F was used it was substituted on the basis of 1.25 pounds of ash added for each pound of cement deleted. Compressive strengths of the water reduced mixes, with and without fly ash, were determined at 7, 28, and 56 days of age. In every case except one the mixes containing the fly ash exhibited higher strengths than the same concrete mix without the fly ash. An excellent correlation existed between the C3WR and C6WR mixes both with and without fly ash substitutions. The freeze-thaw durability of the concrete studied was not affected by presence or absence of fly ash. The data gathered suggests that the present Class C water reduced concrete paving mixes can be modified to allow the substitution of 15% of the cement with an approved fly ash.

Evaluation of Fly Ash Concrete Durability Containing Class II Durability Aggregates, July 1986

Fly ash was used in this evaluation study to replace 15% of the cement in Class C-3 concrete paving mixes. One Class "c" ash from Iowa approved sources was examined in each mix. Substitution rate was based on 1 to 1 basis, for each pound of cement removed 1.0 pound of ash was added. The freeze/thaw durability of the concrete studied was not adversely affected by the presence of fly ash. This study reveals that the durability of the concrete test specimens made with Class II durability aggregates was slightly increased in all cases by the substitution of cement with 15% Class "c" fly ash. In all cases durability factors either remained the same or slightly improved except for one case where the durability factor decreased from 36 to 34. The expansion decreased in all cases.

Evaluation of Fly Ash in lean Portland Cement Concrete Base "Econocrete", August 1986

Fly ash was used in this evaluation study to replace 30, 50 and 70 percent of the 400 1bs. of cement currently used in each cu. yd. of portland cement econocrete base paving mix. Two Class "c" ashes and one Class "F" ash from Iowa approved sources were examined in each mix. When Class "c" ashes were used, they were substituted on the basis of 1.0 pound for each pound of cement removed. When Class "F" ash was used, it was substituted on the basis of 1.25 pounds of ash for each pound of cement removed. Compressive strengths with and without fly ash were determined at 7, 28 and 56 days of age. In most cases, strengths were adequate. The freeze/thaw durability of the econocrete mixes studied was not adversely affected by the presence of fly ash. The tests along with erodibility and absorption tests have demonstrated the feasibility of producing econocrete with satisfactory mechanical properties even when relatively low quality and/or locally available aggregate is being used at no sacrifice to strength and/or durability.

Characterization of Fly Ash for Use in Concrete, HR-225, 1983

Recent construction of new generation power plants burning western coal within Iowa has resulted in fly Ash production on the order of 760,000 tons annually. Although fly ash has long been accepted as a valuable replacement for portland cement in concrete, most experience has been with fly ash generated from eastern bituminous coals. A few years ago, fly ash in Iowa was not a significant factor because production was small and economics dictated disposal as the better alternative than construction use. Today, the economic climate, coupled with abundance of the material, makes constructive use in concrete feasible. The problem is, however, fly ash produced from new power plants is different than that for which information was available. It seems fly ash types have outgrown existing standards. The objective of this study was to develop fundamental information about fly ashes available to construction in Iowa such that its advantages and limitations as replacement to portland cement can be defined. Evaluative techniques used in this work involve sophisticated laboratory equipment, not readily available to potential fly ash users, so a second goal was preliminary development of rapid diagnostic tests founded on fundamental information. Lastly, Iowa Department of Transportation research indicated an interesting interdependency among coarse aggregate type, fly ash and concrete's resistance to freeze-thaw action. Thus a third charge of this research project was to verify and determine the cause for the phenomena. One objective of this project was to determine properties of Iowa fly ashes and evaluate their relevance to use of the material as an admixture of PCC. This phase of the research involved two approaches. The first involved the development of a rapid method for determining quantitative elemental composition while the second was aimed at both qualitative and quantitative determination of compounds. X-ray fluorescence techniques were adapted for rapid determination of elemental composition of fly ash. The analysis was performed using a Siemens SR-200 sequential x-ray spectrometer controlled by a PDP-11-03 microcomputer. The spectrometer was equipped with a ten sample specimen chamber and four interchangeable analyzing crystals. Unfiltered excitation radiation was generated using a chromium tube at 50 KV and 48 ma. Programs for the spectrometer were developed by the Siemens Corporation.

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 Fly Ash in Portland Cement Concrete Pavement in Monona County, Iowa, Construction Report, HR-200, 1978

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 Fly Ash in Portland Cement Concrete Paving in Woodbury County, Iowa, Final Report, HR-201, 1980

The earliest overall comprehensive work on the use of fly ash in concrete was reported by Davis and Associates of the University of California in 1937. Since that time, there have been numerous applications of the use and varying propertions of fly ash in portland cement concrete mixes. Fly ash is a pozzolanic powdery by-product of the coal combustion process which is recovered from flue gases and is, generally associated with electric power generating plants. Environmental regulations enacted in recent years have required that fly ash be removed from the flue gases to maintain clean air standards. This has resulted in an increased volume of high quality fly ash that is considered a waste product or a by-product that can be utilized in products such as portland cement concrete. There are several sources of the high quality fly ash located in Iowa currently producing a combined total of 281,000 tons of material annually.

Evaluation of Fly Ash in Bridge Deck Concrete, MLR-84-2, 1985

Fly ash was used in this evaluation study to replace 15% of the cement in Class D-57 structural concrete containing ASTM C494 Type B, retarding admixtures. Two Class "C" ashes and one Class "F" ash from Iowa approved sources were examined in each mix. When Class "C" ashes were used, they were substituted on the basis of 1.0 pound for each pound of cement removed. When Class "F" ash was used, it was substituted on the basis of 1.25 pounds of ash for each pound of cement removed. Compressive strengths of the retarded mixes, with and without fly ash, were determined at 7, 28 and 56 days of age. In most cases, with few exceptions, the mixes containing the fly ash exhibited higher strengths than the same concrete mix without the fly ash. The exceptions were the 7, 28, and 56 days of the mixes containing Class F ash. The freeze/thaw durability of the concrete studied was not affected by the presence of fly ash. The data obtained suggested that the present Class D-57 structural concrete mix with retarding admixtures can be modified to allow the substitution of 15% of the cement with an approved fly ash when Class III coarse aggregates are used. Setting times of the concretes were not materially changed due to the incorporation of fly ash.

Alkali Content of Fly Ash – Measuring and Testing Strategies for Compliance, TR-628, 2015

Sodium and potassium are the common alkalis present in fly ash. Excessive amounts of fly ash alkalis can cause efflorescence problems in concrete products and raise concern about the effectiveness of the fly ash to mitigate alkali-silica reaction (ASR). The available alkali test, which is commonly used to measure fly ash alkali, takes approximately 35 days for execution and reporting. Hence, in many instances the fly ash has already been incorporated into concrete before the test results are available. This complicates the job of the fly ash marketing agencies and it leads to disputes with fly ash users who often are concerned with accepting projects that contain materials that fail to meet specification limits. The research project consisted of a lab study and a field study. The lab study focused on the available alkali test and how fly ash alkali content impacts common performance tests (mortar-bar expansion tests). Twenty-one fly ash samples were evaluated during the testing. The field study focused on the inspection and testing of selected, well documented pavement sites that contained moderately reactive fine aggregate and high-alkali fly ash. A total of nine pavement sites were evaluated. Two of the sites were control sites that did not contain fly ash. The results of the lab study indicated that the available alkali test is prone to experimental errors that cause poor agreement between testing labs. A strong (linear) relationship was observed between available alkali content and total alkali content of Class C fly ash. This relationship can be used to provide a quicker, more precise method of estimating the available alkali content. The results of the field study failed to link the use of high-alkali fly ash with the occurrence of ASR in the various concrete sites. Petrographic examination of the pavement cores indicated that Wayland sand is an ASR-sensitive aggregate. This was in good agreement with Iowa DOT field service records. It was recommended that preventative measures should be used when this source of sand is used in concrete mixtures.

Role of references in international industrial marketing : a theory-building case study about supplier’s processes of utilizing references

Scientific studies regarding specifically references do not seem to exist. However, the utilization of references is an important practice for many companies involved in industrial marketing. The purpose of the study is to increase the understanding about the utilization of references in international industrial marketing in order to contribute to the development of a theory of reference behavior. Specifically, the modes of reference usage in industry, the factors affecting a supplier's reference behavior, and the question how references are actually utilized, are explored in the study. Due to the explorative nature of the study, a research design was followed where theory and empirical studies alternated. An Exploratory Framework was developed to guide a pilot case study that resulted in Framework 1. Results of the pilot study guided an expanded literature review that was used to develop first a Structural Framework and a Process Framework which were combined in Framework 2. Then, the second empirical phase of the case study was conducted in the same (pilot) case company. In this phase, Decision Systems Analysis (DSA) was used as the analysis method. The DSA procedure consists of three interviewing waves: initial interviews, reinterviews, and validating interviews. Four reference decision processes were identified, described and analyzed in the form of flowchart descriptions. The flowchart descriptions were used to explore new constructs and to develop new propositions to develop Framework 2 further. The quality of the study was ascertained by many actions in both empirical parts of the study. The construct validity of the study was ascertained by using multiple sources of evidence and by asking the key informant to review the pilot case report. The DSA method itself includes procedures assuring validity. Because of the choice to conduct a single case study, external validity was not even pursued. High reliability was pursued through detailed documentation and thorough reporting of evidence. It was concluded that the core of the concept of reference is a customer relationship regardless of the concrete forms a reference might take in its utilization. Depending on various contingencies, references might have various tasks inside the four roles of increasing 1) efficiency of sales and sales management, 2) efficiency of the business, 3) effectiveness of marketing activities, and 4) effectiveness in establishing, maintaining and enhancing customer relationships. Thus, references have not only external but internal tasks as well. A supplier's reference behavior might be affected by many hierarchical conditions. Additionally, the empirical study showed that the supplier can utilize its references as a continuous, all pervasive decision making process through various practices. The process includes both individual and unstructured decision making subprocesses. The proposed concept of reference can be used to guide a reference policy recommendable for companies for which the utilization of references is important. The significance of the study is threefold: proposing the concept of reference, developing a framework of a supplier's reference behavior and its short term process of utilizing references, and conceptual structuring of an unstructured and in industrial marketing important phenomenon to four roles.

Evaluating the structure and magnitude of the ash plume during the initial phase of the 2010 Eyjafjallajökull eruption using lidar observations and NAME simulations

The Eyjafjallajökull volcano in Iceland erupted explosively on 14 April 2010, emitting a plume of ash into the atmosphere. The ash was transported from Iceland toward Europe where mostly cloud-free skies allowed ground-based lidars at Chilbolton in England and Leipzig in Germany to estimate the mass concentration in the ash cloud as it passed overhead. The UK Met Office's Numerical Atmospheric-dispersion Modeling Environment (NAME) has been used to simulate the evolution of the ash cloud from the Eyjafjallajökull volcano during the initial phase of the ash emissions, 14–16 April 2010. NAME captures the timing and sloped structure of the ash layer observed over Leipzig, close to the central axis of the ash cloud. Relatively small errors in the ash cloud position, probably caused by the cumulative effect of errors in the driving meteorology en route, result in a timing error at distances far from the central axis of the ash cloud. Taking the timing error into account, NAME is able to capture the sloped ash layer over the UK. Comparison of the lidar observations and NAME simulations has allowed an estimation of the plume height time series to be made. It is necessary to include in the model input the large variations in plume height in order to accurately predict the ash cloud structure at long range. Quantitative comparison with the mass concentrations at Leipzig and Chilbolton suggest that around 3% of the total emitted mass is transported as far as these sites by small (<100 μm diameter) ash particles.