Sustainable Development and Concrete Technology, May 2004

For a variety of reasons, the concrete construction industry is not sustainable. First, it consumes huge quantities of virgin materials. Second, the principal binder in concrete is portland cement, the production of which is a major contributor to greenhouse gas emissions that are implicated in global warming and climate change. Third, many concrete structures suffer from lack of durability which has an adverse effect on the resource productivity of the industry. Because the high-volume fly ash concrete system addresses all three sustainability issues, its adoption will enable the concrete construction industry to become more sustainable. In this paper, a brief review is presented of the theory and construction practice with concrete mixtures containing more than 50% fly ash by mass of the cementitious material. Mechanisms are discussed by which the incorporation of high volume of fly ash in concrete reduces the water demand, improves the workability, minimizes cracking due to thermal and drying shrinkage, and enhances durability to reinforcement corrosion, sulfate attack, and alkali-silica expansion. For countries like China and India, this technology can play an important role in meeting the huge demand for infrastructure in a sustainable manner.

Concrete Paving Notes Construction No.1, 2005

This booklet will help developers, consultants, and engineers planning concrete pavement construction projects, superintendents and supervisors who want a basic training aid and reference, and crew members new to the concrete paving industry. It provides a general description of current concrete pavement construction practices, from establishing preconstruction control mechanisms to sealing joints. It also provides a quick troubleshooting reference.

Developing Smooth, Quiet, Safe Portland Cement Concrete Pavements, March 2004

The concrete paving industry has spent large amounts of time working to provide safe, quiet, and smooth pavements for the traveling public as their needs and driving habits have changed since the advent of the automobile. During that time, the efforts of research, design, and construction were directed at one of the problems at a time. Current public surveys indicate that the traveling public wishes to have safe, quiet, and smooth pavements. This report identifies the problems remaining in the areas of developing smooth, quiet, and safe portland cement concrete pavement in each pavement we build. It develops the research framework that can be used to bring the existing information together with additional research in each area. The resulting answers can be used in each pavement design for a quiet, safe, and smooth pavement that is also long lasting.

Evaluation of U.S. and European Concrete Pavement Noise Reduction Methods, July 2006

Highway noise is one of the most pressing of the surface characteristics issues facing the concrete paving industry. This is particularly true in urban areas, where not only is there a higher population density near major thoroughfares, but also a greater volume of commuter traffic (Sandberg and Ejsmont 2002; van Keulen 2004). To help address this issue, the National Concrete Pavement Technology Center (CP Tech Center) at Iowa State University (ISU), Federal Highway Administration (FHWA), American Concrete Pavement Association (ACPA), and other organizations have partnered to conduct a multi-part, seven-year Concrete Pavement Surface Characteristics Project. This document contains the results of Part 1, Task 2, of the ISU-FHWA project, addressing the noise issue by evaluating conventional and innovative concrete pavement noise reduction methods. The first objective of this task was to determine what if any concrete surface textures currently constructed in the United States or Europe were considered quiet, had long-term friction characteristics, could be consistently built, and were cost effective. Any specifications of such concrete textures would be included in this report. The second objective was to determine whether any promising new concrete pavement surfaces to control tire-pavement noise and friction were in the development stage and, if so, what further research was necessary. The final objective was to identify measurement techniques used in the evaluation.

Strategic Plan for Improved Concrete Pavement Surface Characteristics, July 2006

Surface characteristics represent a critical issue facing pavement owners and the concrete paving industry. The traveling public has come to expect smoother, quieter, and better drained pavements, all without compromising safety. The overall surface characteristics issues is extremely complex since all pavement surface characteristics properties, including texture, noise, friction, splash/spray, rolling resistance, reflectivity/illuminance, and smoothness, are complexly related. The following needs and gaps related to achieving desired pavement surface characteristics need to be addressed: determined how changes in one surface characteristic affect, either beneficially or detrimentally, other characteristics of the pavement, determine the long-term surface and acoustic durability of different textures, and develop, evaluate, and standardize new data collection and analysis tools. It is clear that an overall strategic and coordinated research approach to the problem must be developed and pursued to address these needs and gaps.

Development of Performance Properties of Ternary Mixes: Scoping Study, June 2005

Pozzolans and slag extend the market for concrete products by improving specific properties of the products, which allows the products to be constructed with materials or placed in environments that would have precluded the use of portland cement alone. In properly formulated concrete mixes, pozzolans and slag have been shown to enhance long-term strength, decrease permeability, increase durability, reduce thermal cracking of mass concrete, minimize or eliminate cracking related to alkali-silica reaction (ASR), and minimize or eliminate cracking related to sulfate attack. The purpose of this research project was to conduct a scoping study that could be used to evaluate the need for additional research in the area of supplementary cementitious materials (SCMs) that are used in concrete for highway applications. Special emphasis was given to the concept of using two or more SCMs in a single concrete mixture. The scope of the study was limited to a literature survey and panel discussions concerning issues relevant to the project. No laboratory work was conducted for this project. A problem statement with research plan was created that could be used to guide a pooled fund project.

Self-Consolidating Concrete—Applications for Slip-Form Paving: Phase II, May 2011

The goal of the project was to develop a new type of self-consolidating concrete (SCC) for slip-form paving to simplify construction an make smoother pavements. Developing the new SCC involved two phases: a feasibility study (Phase I sponsored by TPF-5[098] and concrete admixtures industry) and an in-depth mix proportioning and performance study and field applications (Phase II). The phase I study demonstrated that the new type of SCC needs to possess not only excellent self-consolidating ability before a pavement slab is extruded, but also sufficient “green” strength (the strength of the concrete in a plastic state) after the extrusion. To meet these performance criteria, the new type of SCC mixtures should not be as fluid as conventional SCC but just flowable enough to be self-consolidating. That is, this new type of SCC should be semi-flowable self-consolidating concrete (SFSCC). In the phase II study, effects of different materials and admixtures on rheology, especially the thixotropy, and green strength of fresh SFSCC have been further investigated. The results indicate that SFSCC can be designed to (1) be workable enough for machine placement, (2) be self-consolidating without segregation, (3) hold its shape after extrusion from a paver, and (4) have performance properties (strength and durability) comparable with current pavement concrete. Due to the combined flowability (for self-consolidation) and shape-holding ability (for slip-forming) requirements, SFSCC demands higher cementitious content than conventional pavement concrete. Generally, high cementitious content is associated with high drying shrinkage potential of the concrete. However, well-proportioned and well-constructed SFSCC in a bike path constructed at Ames, IA, has not shown any shrinkage cracks after approximately 3 years of field service. On the other hand, another SFSCC pavement with different mix proportions and construction conditions showed random cracking. The results from the field SFSCC performance monitoring implied that not only the mix proportioning method but also the construction practice is important for producing durable SFSCC pavements. A carbon footprint, energy consumption, and cost analysis conducted in this study have suggested that SFSCC is economically comparable to conventional pavement concrete in fixed-form paving construction, with the benefit of faster, quieter, and easier construction.

20 Native Trees to Plant, January 25, 2010

If you have ever flown in an airplane over Iowa, you would see that our woodlands are scattered along the rivers and streams and areas too steep to farm. You would also see a green carpet of trees within out cities and towns. Did you know the 90% of the over 2.7 million acres of forest in Iowa is owned by over 138,000 different private owners? Or that 30% of the land cover in a typical Iowa community if covered by trees? Trees are vital for the protection of our drinking water supply, critical for wildlife habitat, and help sustain employment of over 7,000 Iowans in the wood products industry. This booklet "20 Native trees to Plant" will help you gain a greater knowledge about Iowa's trees and forests. Learn about and enjoy Iowa's trees. Consider ways that you can improve our environment by planting and caring for Iowa's trees and forests.

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.

Performance of Nongrouted Thin Bonded PCC Overlays, Construction Report, HR-291, 1986

The Iowa road system has approximately 13,000 miles of Portland Cement Concrete Pavements, many of which are reaching the stage where major rehabilitation is required. Age, greater than anticipated traffic, heavier loads and deterioration related to coarse aggregate in the original pavement are some of the reasons that these pavements have reached this level of distress. One method utilized to rehabilitate distressed or underdesigned PCC pavements is the thin bonded Portland Cement Concrete overlay. Since the introduction of thin bonded overlays on highway pavements in 1973, the concrete paving industry has made progress in reducing the construction costs of this rehabilitation technique. With the advent of the shotblast machine, surface preparation costs have decreased from over $4.00 per square yard to most recently $1.42 per square yard. Other construction costs, including placement, grouting and sawing, have also declined. With each project, knowledge and efficiency have improved.

Determine Initial Cause for Current Premature Portland Cement Concrete Pavement Deterioration Final Report, 2000

A detailed investigation has been conducted on core samples taken from 17 portland cement concrete pavements located in Iowa. The goal of the investigation was to help to clarify the root cause of the premature deterioration problem that has become evident since the early 1990s. Laboratory experiments were also conducted to evaluate how cement composition, mixing time, and admixtures could have influenced the occurrence of premature deterioration. The cements used in this study were selected in an attempt to cover the main compositional parameters pertinent to the construction industry in Iowa. The hardened air content determinations conducted during this study indicated that the pavements that exhibited premature deterioration often contained poor to marginal entrained-air void systems. In addition, petrographic studies indicated that sometimes the entrained-air void system had been marginal after mixing and placement of the pavement slab, while in other instances a marginal to adequate entrained-air void system had been filled with ettringite. The filling was most probably accelerated because of shrinkage cracking at the surface of the concrete pavements. The results of this study suggest that the durability—more sciecifically, the frost resistance—of the concrete pavements should be less than anticipated during the design stage of the pavements. Construction practices played a significant role in the premature deterioration problem. The pavements that exhibited premature distress also exhibited features that suggested poor mixing and poor control of aggregate grading. Segregation was very common in the cores extracted from the pavements that exhibited premature distress. This suggests that the vibrators on the paver were used to overcome a workability problem. Entrained-air voids formed in concrete mixtures experiencing these types of problems normally tend to be extremely coarse, and hence they can easily be lost during the paving process. This tends to leave the pavement with a low air content and a poor distribution of air voids. All of these features were consistent with a premature stiffening problem that drastically influenced the ability of the contractor to place the concrete mixture. Laboratory studies conducted during this project indicated that most premature stiffening problems can be directly attributed to the portland cement used on the project. The admixtures (class C fly ash and water reducer) tended to have only a minor influence on the premature stiffening problem when they were used at the dosage rates described in this study.

The Growth and Direction of the Biodiesel Industry in the United States, 2007

The biodiesel industry in the United States has realized significant growth over the past decade through large increases in annual production and production capacity and a transition from smaller batch plants to larger-scale continuous producers. The larger, continuous-flow plants provide operating cost advantages over the smaller batch plants through their ability to capture co-products and reuse certain components in the production process. This paper uses a simple capital budgeting model developed by the authors along with production data supplied by industry sources to estimate production costs, return-on-investment levels, and break-even conditions for two common plant sizes (30 and 60 million gallon annual capacities) over a range of biodiesel and feedstock price levels. The analysis shows that the larger plant realizes returns to scale in both labor and capital costs, enabling the larger plant to pay up to $0.015 more per pound for the feedstock to achieve equivalent return levels as the smaller plant under the same conditions. The paper contributes to the growing literature on the biodiesel industry by using the most current conversion rates for the production technology and current price levels to estimate biodiesel production costs and potential plant performance, providing a useful follow-up to previous studies.

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.

Workshop on Nanotechnology for Cement and Concrete, September 5, 2007

This document summarizes the discussions and findings of a workshop held in Arlington, VA, on September 5, 2007. The objective of the meeting was to provide national direction on areas of priority interest and collaboration between industry and public agencies specifically for applications of nanotechnology to cement and concrete.

Evaluation of Concrete Sealers for Use on Bridge Pier Tops and Abutments, R-242, 1971

Many reports have been written concerning investigations of concrete sealants. The primary concern of most investigators is the protection of bridge decks from de-icing chemicals which cause surface scaling and, when allowed to permeate to reinforcing steel, result in deep spalling and general concrete deterioration. The problem of protecting abutments and pier tops from salt solutions entails a significantly different approach than the problem of protecting bridge decks. The epoxy resins become eligible as a protective material since one need not be concerned with slipperiness or its abrasive characteristics. Protection with linseed oil at regular intervals would prove bothersome because of the inaccessibility of pier tops after the deck is placed. The primary purpose of this investigation was to evaluate various commercial products in terms of their ability to prevent concrete scaling of bridge abutments and pier tops which are subject to salt water deterioration.