Deicer Scaling Resistance of Concrete Mixtures Containing Slag Cement Phase 2: Evaluation of Different Laboratory Scaling Test Methods, TPF-5(100), 2012

With the use of supplementary cementing materials (SCMs) in concrete mixtures, salt scaling tests such as ASTM C672 have been found to be overly aggressive and do correlate well with field scaling performance. The reasons for this are thought to be because at high replacement levels, SCM mixtures can take longer to set and to develop their properties: neither of these factors is taken into account in the standard laboratory finishing and curing procedures. As a result, these variables were studied as well as a modified scaling test, based on the Quebec BNQ scaling test that had shown promise in other research. The experimental research focused on the evaluation of three scaling resistance tests, including the ASTM C672 test with normal curing as well as an accelerated curing regime used by VDOT for ASTM C1202 rapid chloride permeability tests and now included as an option in ASTM C1202. As well, several variations on the proposed draft ASTM WK9367 deicer scaling resistance test, based on the Quebec Ministry of Transportation BNQ test method, were evaluated for concretes containing varying amounts of slag cement. A total of 16 concrete mixtures were studied using both high alkali cement and low alkali cement, Grade 100 slag and Grade 120 slag with 0, 20, 35 and 50 percent slag replacement by mass of total cementing materials. Vinsol resin was used as the primary air entrainer and Micro Air® was used in two replicate mixes for comparison. Based on the results of this study, a draft alternative test method to ASTM C762 is proposed.

Laboratory Study of Structural Behavior of Alternative Dowel Bars, April 2006

Load transfer across transverse joints has always been a factor contributing to the useful life of concrete pavements. For many years, round steel dowels have been the conventional load transfer mechanism. Many problems have been associated with the round steel dowels. The most detrimental effect of the steel dowel is corrosion. Repeated loading over time also damages joints. When a dowel is repeatedly loaded over a long period of time, the high bearing stresses found at the top and bottom edge of a bar erode the surrounding concrete. This oblonging creates multiple problems in the joint. Over the past decade, Iowa State University has performed extensive research on new dowel shapes and materials to mitigate the effects of oblonging and corrosion. This report evaluates the bearing stress performance of six different dowel bar types subjected to two different shear load laboratory test methods. The first load test is the AASHTO T253 method. The second procedure is an experimental cantilevered dowel test. The major objective was to investigate and improve the current AASHTO T253 test method for determining the modulus of dowel support, k0. The modified AASHTO test procedure was examined alongside an experimental cantilever dowel test. The modified AASHTO specimens were also subjected to a small-scale fatigue test in order to simulate long-term dowel behavior with respect to concrete joint damage. Loss on ignition tests were also performed on the GFRP dowel specimens to determine the resin content percentage. The study concluded that all of the tested dowel bar shapes and materials were adequate with respect to performance under shear loading. The modified AASHTO method yielded more desirable results than the ones obtained from the cantilever test. The investigators determined that the experimental cantilever test was not a satisfactory test method to replace or verify the AASHTO T253 method.

Modified Sheet Pile Abutments for Low-Volume Road Bridges: Tech Transfer Summary, January 2012

Iowa has about 22,936 bridges on low-volume roads (LVRs). Based on the National Bridge Inventory data, 22 percent of the LVR bridges in Iowa are structurally deficient, while 5 percent of them are functionally obsolete. The substructure components (abutment and foundation elements) are known to be contributing factors for some of these poor ratings. Steel sheet piling was identified as a possible long-term option for LVR bridge substructures; but, due to lack of experience, Iowa needed investigation with regard to vertical and lateral load resistance, construction methods, design methodology, and load test performance. This project was initiated in January 2007 to investigate use of sheet pile abutments. *************Tech Transfer Summary. For full report see: http://publications.iowa.gov/id/eprint/14832*************

Iowa Pore Index Test, MLR-80-2, 1980

The objective of the investigation was the development of a test that would readily identify the potential of an aggregate to cause D-cracking because of its susceptivity to critical saturation. A Press-Ur-Meter was modified by replacing the air chamber with a one-inch diameter plastic tube calibrated in milli-. It was concluded that the pore index was sufficiently reliable to determine the D-cracking potential of limestone aggregates in all but a few cases where marginal results were obtained. Consistently poor or good results were always in agreement with established service records or concrete durability testing. In those instances where marginal results are obtained, the results of concrete durability testing should be considered when making the final determination of the D-cracking susceptibility of the aggregate in question. The following applications for the pore index test have been recommended for consideration: concrete durability testing be discontinued in the evaluation process of new aggregate sources with pore index results between 0-20 (Class 2 durability) and over 35 (Class 1) durability; composite aggregates with intermediate pore index results of 20-35 be tested on each stone type to facilitate the possible removal of low durability stone from the production process; and additional investigation should be made to evaluate the possibility of using the test to monitor and upgrade the acceptance of aggregate from sources associated with D-cracking.

Sieve Analysis of Combined Aggregate Samples by Different Test Methods, MLR-84-05, 1982

This past winter the sieve analysis of combined aggregate was investigated. This study was given No. 26 by the Central Laboratory. The purpose of this work was to try and develop a sieve analysis procedure for combined aggregate which is less time consuming and has the same accuracy as the method described in I.M. 304. In an attempt to use a variety of aggregates for this investigation, a request was made to each District Materials Office to obtain at least 3 different combined aggregate samples in their respective districts. At the same time it was also requested that the field technician test these samples, prior to submitting them to the Central Laboratory. The field technician was instructed to test each sample as described in method I.M. 304 and also by a modified AASHTO T27 method which will be identified in the report as Method A. The modified AASHTO Method A was identical to T27 with the exception that a smaller sample is used for testing. The field technicians submitted the samples, test results and also comments regarding the modified AASHTO procedure. The general comments of the modified AASHTO procedure were: The method was much simpler to follow; however, it took about the same amount of time so there was no real advantage. After reviewing AASHTO T27, T164, I.M. 304 and Report No. FHWA-RD-77-53 another test method was purposed. Report No. FHWA-RD-77-53 is a report prepared by FHWA from data they gathered concerning control practices and shortcut or alternative test methods for aggregate gradation. A second test method was developed which also was very similar to AASHTO T27, The test procedure for this method is attached and is identified as Method B. The following is a summary of test results submitted by the Field Technicians and obtained by the aggregate section of the Central Laboratory.

Investigation of the Modified Beam-in-Slab Bridge System, Technical Report, 2004, Vol. 1

Technical Report

Investigation of the Modified Beam-in-Slab Bridge System, Design Guide, 2004, Vol. 3

Design guide

Investigation of the Modified Beam-in-Slab Bridge System, Design Manual, 2004, Vol. 2

Design Manual

Labeling Regulations and Segregation of First- and, Second-Generation Genetically Modified Products: Innovation Incentives and Welfare Effects, April 2005

We review some of the most significant issues and results on the economic effects of genetically modified (GM) product innovation, with emphasis on the question of GM labeling and the need for costly segregation and identity preservation activities. The analysis is organized around an explicit model that can accommodate the features of both first-generation and second-generation GM products. The model accounts for the proprietary nature of GM innovations and for the critical role of consumer preferences vis-à-vis GM products, as well as for the impacts of segregation and identity preservation and the effects of a mandatory GM labeling regulation. We also investigate briefly a novel question in this setting, the choice of “research direction”when both cost-reducing and quality-enhancing GM innovations are feasible.