Special investigation of the University of Northern Iowa Events Complex Concessions for the period October 1, 2006 through March 31, 2012

Special investigation of the University of Northern Iowa Events Complex Concessions for the period October 1, 2006 through March 31, 2012

Report on a special investigation of the City of Indianola for the period June 1, 2006 through August 31, 2012

Report on a special investigation of the City of Indianola for the period June 1, 2006 through August 31, 2012

Report on a special investigation of the Lyon County Engineer’s Office for the period August 1, 2006 through May 31, 2012

Report on a special investigation of the Lyon County Engineer’s Office for the period August 1, 2006 through May 31, 2012

Report on a special investigation of the Creston Water Works for the period July 1, 2005 through November 16, 2012

Report on a special investigation of the Creston Water Works for the period July 1, 2005 through November 16, 2012

Report on special investigation of the Department of Inspections and Appeals, Office of the State Public Defender, for the period August 31, 2007 through March 31, 2011

Report on a special investigation of the State Public Defender’s Office for the period August 31, 2007 through March 31, 2011

Report on special investigation of the City of Farmington for the period July 1, 2009 through November 30, 2012

Special investigation of the City of Farmington for the period July 1, 2009 through November 30, 2012

Report on a special investigation of the City of Grand River for the period July 1, 2004 through March 7, 2012

Report on a special investigation of the City of Grand River for the period July 1, 2004 through March 7, 2012

Investigation of Deterioration of Joints in Concrete Pavements , TPF-5(224), 2012

Premature deterioration of concrete at the joints in concrete pavements and parking lots has been reported across the northern states. The distress is first observed as shadowing when microcracking near the joints traps water, later exhibiting as significant loss of material. Not all roadways are distressed, but the problem is common enough to warrant attention. The aim of the work being conducted under this and parallel contracts was to improve understanding of the mechanisms behind premature joint deterioration and, based on this understanding, develop training materials and guidance documents to help practitioners reduce the risk of further distress and provide guidelines for repair techniques. While work is still needed to understand all of the details of the mechanisms behind premature deterioration and prevention of further distress, the work in this report has contributed to advancing the state of knowledge.

Report on a special investigation of the football program at Lincoln High School within the Des Moines Independent Community School District for the period May 30, 2003 through October 31, 2012

Report on a special investigation of the football program at Lincoln High School within the Des Moines Independent Community School District for the period May 30, 2003 through October 31, 2012

Investigation into Shrinkage of High-Performance Concrete Used for Iowa Bridge Decks and Overlays, TR-633, 2013

High-performance concrete (HPC) overlays have been used increasingly as an effective and economical method for bridge decks in Iowa and other states. However, due to its high cementitious material content, HPC often displays high shrinkage cracking potential. This study investigated the shrinkage behavior and cracking potential of the HPC overlay mixes commonly used in Iowa. In the study, 11 HPC overlay mixes were studied. These mixes consisted of three types of cements (Type I, I/II, and IP) and various supplementary cementitious materials (Class C fly ash, slag and metakaolin). Limestone with two different gradations was used as coarse aggregates in 10 mixes and quartzite was used in one mix. Chemical shrinkage of pastes, free drying shrinkage, autogenous shrinkage of mortar and concrete, and restrained ring shrinkage of concrete were monitored over time. Mechanical properties (such as elastic modulus and compressive and splitting tensile strength) of these concrete mixes were measured at different ages. Creep coefficients of these concrete mixes were estimated using the RILEM B3 and NCHRP Report 496 models. Cracking potential of the concrete mixes was assessed based on both ASTM C 1581 and simple stress-to-strength ratio methods. The results indicate that among the 11 mixes studied, three mixes (4, 5, and 6) cracked at the age of 15, 11, and 17 days, respectively. Autogenous shrinkage of the HPC mixes ranges from 150 to 250 microstrain and free dying shrinkage of the concrete ranges from 700 to 1,200 microstrain at 56 days. Different concrete materials (cementitious type and admixtures) and mix proportions (cementitious material content) affect concrete shrinkage in different ways. Not all mixes having a high shrinkage value cracked first. The stresses in the concrete are associated primarily with the concrete shrinkage, elastic modulus, tensile strength, and creep. However, a good relationship is found between cementitious material content and total (autogenous and free drying) shrinkage of concrete.

Addendum to a report on a special investigation of the Iowa Department of Transportation for the period January 29, 1994 through June 30, 2013

Addendum to a report on a special investigation of the Iowa Department of Transportation for the period January 29, 1994 through June 30, 2013

Report on a special investigation of Remsen-Union Family Connections for the period July 1, 2011 through October 31, 2012

Report on a special investigation of Remsen-Union Family Connections for the period July 1, 2011 through October 31, 2012

Investigation of Warm-Mix Asphalt for Iowa Roadways, TR-635, 2013

Phase II of this study further evaluated the performance of plant-produced warm-mix asphalt (WMA) mixes by conducting additional mixture performance tests at a broader range of temperatures, adding additional pavements to the study, comparing virgin and recovered binder properties, performing pavement condition surveys, and comparing survey data with the Mechanistic Empirical Pavement Design Guide (MEPDG) forecast for pavement damage over 20 years of service life. Further objectives detailing curing behavior, quality assurance testing, and hybrid technologies were as follows: * Compare the predicted and observed field performance of existing WMA trials produced in the previous Phase I study to that of hot-mix asphalt (HMA) control sections to determine if Phase I conclusions are translating to the field; * Identify any curing effect (and timing of the effect) of WMA mixtures and binders in the field; * Determine how the field-compacted mixture properties and recovered binder properties of WMA compare to those of HMA over time for technologies common to Iowa; * Identify the protocols for WMA sample preparation for volumetric and performance testing that best simulate field conditions. The findings of this study indicate that WMA additives do show statistical differences in mixture properties in some of the mixes tested. These differences will not always be statistically different from mixture to mixture. Multiple factors, such as WMA additive type, amount of recycled asphalt material, construction conditions, and mixture variability all play a role in determining the extent of which WMA and HMA mixes differ. Other significant findings of this study include effects of curing, aging in recovered binders from HMA and WMA cores, and the influence of recycled asphalt shingles (RAS) used with WMA. These findings will be of interest to owner agencies and contractors utilizing WMA technologies.

Report on a special investigation of the City of Sloan for the period May 19, 2009 through March 31, 2013

Report on a special investigation of the City of Sloan for the period May 19, 2009 through March 31, 2013

Special investigation of the Garner Volunteer Ambulance Service for the period July 1, 2011 through June 30, 2012

Special investigation of the Garner Volunteer Ambulance Service for the period July 1, 2011 through June 30, 2012