City of Mapleton and Mapleton Municipal Electric, Auditor of State's Report on Reaudit, For the Period July 1, 2002 through June 30, 2003

City Audit Report - Reaudit

Report on a special investigation of the City of Ames Electric Department for the period July 1, 2003 through January 7, 2008

Report on a special investigation of the City of Ames Electric Department for the period July 1, 2003 through January 7, 2008

Concrete Pavement Mixture Design and Analysis (MDA): Application of a Portable X-Ray Fluorescence Technique to Assess Concrete Mix Proportions , TPF-5(205), 2012

Any transportation infrastructure system is inherently concerned with durability and performance issues. The proportioning and uniformity control of concrete mixtures are critical factors that directly affect the longevity and performance of the portland cement concrete pavement systems. At present, the only means available to monitor mix proportions of any given batch are to track batch tickets created at the batch plant. However, this does not take into account potential errors in loading materials into storage silos, calibration errors, and addition of water after dispatch. Therefore, there is a need for a rapid, cost-effective, and reliable field test that estimates the proportions of as-delivered concrete mixtures. In addition, performance based specifications will be more easily implemented if there is a way to readily demonstrate whether any given batch is similar to the proportions already accepted based on laboratory performance testing. The goal of the present research project is to investigate the potential use of a portable x-ray fluorescence (XRF) technique to assess the proportions of concrete mixtures as they are delivered. Tests were conducted on the raw materials, paste and mortar samples using a portable XRF device. There is a reasonable correlation between the actual and calculated mix proportions of the paste samples, but data on mortar samples was less reliable.

Bridge Deck Delamination Study Infrared Inspection, HR-244, 1982

The Iowa Department of Transportation is responsible for maintaining approximately 3800 bridges throughout the State. Of these bridges approximately 3200 have concrete decks. The remaining bridges have been constructed or repaired with a Portland Cement (P. C.) concrete overlay. Surveys of the overlays have indicated a growing incidence of delaminations and surface distress. The need to replace or repair the overlay may be dictated by the amount of delamination in the deck. Additionally, the concrete bridges are periodically inspected and scheduled for the appropriate rehabilitation. Part of this analysis is an assessment of the amount of delamination present in the deck. The ability to accurately and economically identify delamination in overlays and bridge decks is necessary to cost-effectively evaluate and schedule bridge rehabilitation. There are two conventional methods currently being used to detect delaminations. One is ref erred to as a chain drag method. The other a electro-mechanical sounding method (delamtect). In the chain drag method, the concrete surface is struck using a heavy chain. The inspector then listens to the sound produced as the surface is struck. The delaminated areas produce a dull sound as compared to nondelaminated areas. This procedure has proved to be very time consuming, especially when a number of small areas of delamination are present. With the · electro-mechanical method, the judgement of the inspector has been eliminated. A· device with three basic components, a tapping device, a sonic receiver, and a system of signal interpretation has been developed. This· device is wheeled along the deck and the instrument receives and interprets the acoustic signals generated by the instrument which in turn are reflected through the concrete. A recently developed method of detecting delaminations is infrared thermography. This method of detection is based on the difference in surface temperature which exists between delaminated and nondelaminated concrete under certain atmospheric conditions. The temperature difference can reach 5°C on a very sunny day where dry pavement exists. If clouds are present, or the pavement is wet, then the temperature difference between the delaminated and nondelaminated concrete will not be as great and therefore more difficult to detect. Infrared thermography was used to detect delaminations in 17 concrete bridge decks, 2 P. C. concrete overlays, and 1 section of continuously reinforced concrete pavement (CRCP) in Iowa. Thermography was selected to assess the accuracy, dependability, and potential of the infrared thermographic technique.