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.

An Evaluation of the Consolidation Monitoring Device, HR-1013, 1978

The Iowa Department of Transportation research project HR-1013 is the evaluation of a prototype continuous monitoring nuclear density unit. The Unit, the Consolidation Monitoring Device (CMD), mounts on the rear of a slip-form paver and measures the density of the concrete while still in the plastic state. The evaluation performed determined the usefulness, accuracy, precision and reproducibility of the unit. The CMD was calibrated and tested in the laboratory for one week before field evaluation. The field evaluation consisted of monitoring at least 5 miles of paving and then correlating the CMD data with two conventional density methods. The two supplemental methods were density measurement with a Troxler nuclear gauge and densities obtained from core samples.

Investigation of Field Corrosion Performance and Bond/Development Length of Galvanized Reinforcing Steel, TR-666, 2014

In reinforced concrete systems, ensuring that a good bond between the concrete and the embedded reinforcing steel is critical to long-term structural performance. Without good bond between the two, the system simply cannot behave as intended. The bond strength of reinforcing bars is a complex interaction between localized deformations, chemical adhesion, and other factors. Coating of reinforcing bars, although sometimes debated, has been commonly found to be an effective way to delay the initiation of corrosion in reinforced concrete systems. For many years, the standard practice has been to coat reinforcing steel with an epoxy coating, which provides a barrier between the steel and the corrosive elements of water, air, and chloride ions. Recently, there has been an industry-led effort to use galvanizing to provide the protective barrier commonly provided by traditional epoxy coatings. However, as with any new structural product, questions exist regarding both the structural performance and corrosion resistance of the system. In the fall of 2013, Buchanan County, Iowa constructed a demonstration bridge in which the steel girders and all internal reinforcing steel were galvanized. The work completed in this project sought to understand the structural performance of galvanized reinforcing steel as compared to epoxy-coated steel and to initiate a long-term corrosion monitoring program. This work consisted of a series of controlled laboratory tests and the installation of a corrosion monitoring system that can be observed for years in the future. The results of this work indicate there is no appreciable difference between the bond strength of epoxy-coated reinforcing steel and galvanized reinforcing steel. Although some differences were observed, no notable difference in either peak load, slip, or failure mode could be identified. Additionally, a long-term monitoring system was installed in this Buchanan County bridge and, to date, no corrosion activity has been identified.

Summary of the opinions of the Attorney General, 2015

Compiled biennially as Official opinions of the Attorney General in the Report of the Attorney General. Report year ends December 31. Slip opinions of the Attorney General.

Summary of the opinions of the Attorney General, 2014

Compiled biennially as Official opinions of the Attorney General in the Report of the Attorney General. Report year ends December 31. Slip opinions of the Attorney General.

Summary of the opinions of the Attorney General, 2012

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Summary of the opinions of the Attorney General, 2011

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Summary of the opinions of the Attorney General, 2009

Compiled biennially as Official opinions of the Attorney General in the Report of the Attorney General. Report year ends December 31. Slip opinions of the Attorney General.

Summary of the opinions of the Attorney General, 2007

Compiled biennially as Official opinions of the Attorney General in the Report of the Attorney General. Report year ends December 31. Slip opinions of the Attorney General.

Summary of the opinions of the Attorney General, 2008

Compiled biennially as Official opinions of the Attorney General in the Report of the Attorney General. Report year ends December 31. Slip opinions of the Attorney General.

Summary of the opinions of the Attorney General, 2006

Compiled biennially as Official opinions of the Attorney General in the Report of the Attorney General. Report year ends December 31. Slip opinions of the Attorney General.

Summary of the opinions of the Attorney General, 2005

Compiled biennially as Official opinions of the Attorney General in the Report of the Attorney General. Report year ends December 31. Slip opinions of the Attorney General.

Summary of the opinions of the Attorney General, 2004

Compiled biennially as Official opinions of the Attorney General in the Report of the Attorney General. Report year ends December 31. Slip opinions of the Attorney General.

Summary of the opinions of the Attorney General, 2003

Compiled biennially as Official opinions of the Attorney General in the Report of the Attorney General. Report year ends December 31. Slip opinions of the Attorney General.

Summary of the opinions of the Attorney General, 2002

Compiled biennially as Official opinions of the Attorney General in the Report of the Attorney General. Report year ends December 31. Slip opinions of the Attorney General.