Absorption of Asphalt by Aggregate, HR-142, Progress Report, 1970

This report summarizes work accomplished under Project HR-142 during the period from January 1, 1969 to December 31, 1969. Pore characteristics of six limestones were studied in relation to their absorption of two asphalt cements. Porosity and pore size distribution were determined by a mercury penetration porosimeter and asphalt absorption was determined by immersion and bulk-impregnated specific gravity methods. A special study was conducted to develop new, simple and more reproducible methods for bulk specific gravity determination. As a result, a new chemical indicator method was developed to determine the saturated surface-dry condition, and a glass mercury pycnometer was designed to determine coarse·and fine aggregates. Asphalt absorption history of one asphalt mixture on campus has been studied since September 1968. Chemical and/or radiation treatments of absorptive aggregates were conducted on four chemicals and two aggregates.

Improvement of Longitudinal Joints in Asphalt Pavement, HR-215, Construction Report, 1981

One significant benefit of asphalt concrete pavement construction is that it may be opened to traffic within one hour after being laid. Therefore, road closure and detour are not necessary, but only temporary lane closure and control of traffic. This one lane construction, even though desirable in regard to maintaining traffic flow, does pose an additional problem. The longitudinal joint at centerline often becomes a maintenance problem. The objective of this research project is to identify construction procedures that will provide an improved centerline joint.

Evaluation of the Chemical Durability of Iowa Fly Ash Concretes, HR-327, Phase II Progress Report, 1992

The major objective of this research project is to investigate how fly ash influences the chemical durability of portland cement based materials. The testing program is evaluating how Iowa fly ashes influence the sulfate durability of portland cement-fly ash pastes, mortars, and concretes. Also, alkali-reactivity studies are being conducted on mortar bar specimens prepared in accordance with ASTM C 311. Prelimary sulfate test results, based only on mortar bar studies, indicate that only the very high-calcium fly ash (29 percent CaO, by weight) consistently reduced the durability of test specimens exposed to a solution containing 5 percent sodium sulfate. The remaining four fly ashes that were used in the study showed negligible to dramatic increases in sulfate resistance. Concrete specimens were only beginning to respond to the sulfate solutions after about one year of exposure; and hence, considerably more time will be needed to assess their performance. Preliminary results from the alkali-reactivity tests have indicated that the Oreopolis aggregate is not sensitive to alkali attack. However, some of the test results have indicated that the testing procedure may be prone to delayed expansion due to the presence of periclase (MgO) in the Class C fly ashes. Research is being planned to: (1) verify if the periclase is influencing test results; and (2) estimating the magnitude of the potential error.

Taxonomy of Institutional Issues that Act as Barriers to the Implementation of Pavement Management Systems, 1994

The benefits of pavement management system when fully implemented are well known and the history of successful implementation is rich. Implementation occurs, for purposes of this paper, when the pavement management system is the critical component for making pavement decisions. This paper addresses the issues that act as barriers to full implementation of pavement management systems. Institutional barriers, not technical and financial barriers, are more commonly responsible for a pavement management systems falling short of full implementation. The paper groups these institutional issues into a general taxonomy. In general, more effort needs to be put forth by highway agencies to overcome institutional issues. Most agencies approach pavement management as a technical process, but more commonly, institutional issues become more problematic and thus require more attention paid to institutional issues. The paper concludes by summarizing the implementation process being taken by the Iowa Department of Transportation. The process was designed to overcome institutional barriers and facilitate the complete and full implementation of their pavement management system.

Evaluation and Testing of a Lightweight Fine Aggregate Concrete Bridge Deck in Buchanan County, Iowa, TR-648, 2016

Internal curing is a relatively new technique being used to promote hydration of Portland cement concretes. The fundamental concept is to provide reservoirs of water within the matrix such that the water does not increase the initial water/cementitious materials ratio to the mixture, but is available to help continue hydration once the system starts to dry out. The reservoirs used in the US are typically in the form of lightweight fine aggregate (LWFA) that is saturated prior to batching. Considerable work has been conducted both in the laboratory and in the field to confirm that this approach is fundamentally sound and yet practical for construction purposes. A number of bridge decks have been successfully constructed around the US, including one in Iowa in 2013. It is reported that inclusion of about 20% to 30% LWFA will not only improve strength development and potential durability, but, more importantly, will significantly reduce shrinking, thus reducing cracking risk. The aim of this work was to investigate the feasibility of such an approach in a bridge deck.

Factors influencing stability of granular base course mixes, 1969

The objectives of this final report; Iowa Highway Research Board Project HR-99 by J.M. Hoover, was to evaluate the various factors influencing the stability of granular base course mixes.

Asphalt cement concrete pavement recycling, Cass and Montgomery Counties : final report for Iowa DOT project HR-1018, Federal Highway Administration demonstration project no. 39, contract no. DOT-FH-15-336, 1986

This demonstration project consisted of three adjacent highway resurfacing projects using asphalt cement concrete removed from an Interstate highway which had become severely rutted.

Shear Strength of Granular Materials, 1967

A theory was developed to allow the separate determination of the effects of the interparticle friction and interlocking of particles on the shearing resistance and deformational behavior of granular materials. The derived parameter, angle of solid friction, is independent of the type of shear test, stress history, porosity and the level of confining pressure, and depends solely upon the nature of the particle surface. The theory was tested against published data concerning the performance of plane strain, triaxial compression and extension tests on cohesionless soils. The theory also was applied to isotropically consolidated undrained triaxial tests on three crushed limestones prepared by the authors using vibratory compaction. The authors concluded that, (1) the theory allowed the determination of solid friction between particles which was found to depend solely on the nature of the particle surface, (2) the separation of frictional and volume change components of shear strength of granular materials qualitatively corroborated the postulated mechanism of deformation (sliding and rolling of groups of particles over other similar groups with resulting dilatancy of specimen), (3) the influence of void ratio, gradation confining pressure, stress history and type of shear test on shear strength is reflected in values of the omega parameter, and (4) calculation of the coefficient of solid friction allows the establishment of the lower limit of the shear strength of a granular material.

Evaluation, Selection and Planning the Implementation of a Pavement Management Optimization Model: Optimization Recommendations, 1994

This document briefly summarizes the pavement management activities under the existing Iowa Department of Transportation (DOT) Pavement Management System. The second part of the document provides projected increase in use due to the implementation of the Iowa DOT Pavement Management Optimization System. All estimates of existing time devoted to the Pavement Management System and project increases in time requirements are estimates made by the appropriate Iowa DOT office director or function manager. Included is the new Pavement Management Optimization Structure for the three main offices which will work most closely with the Pavement Management Optimization System (Materials, Design, and Program Management).

Evaluation, Selection and Planning the Implementation of a Pavement Management Optimization Model, Phase II Report, 1994

The missions of the research are to assist the Iowa Department of Transortation (Iowa DOT) to: Define pavement management (PM) optimization; Identify the characteristics of PM optimization systems being developed or implemented; Identify specific and achievable objectives for the Iowa DOT pavement management optimization; Evaluate different PM optimization methodologies; Identify a methodology to perform PM optimization that best satisfies the Iowa DOT's objectives; Develop a plan for the implementation of the PM optimization selected. The project is divided into three (3) phases. The first phase has been completed and accomplished the first three missions (identified above). The second phase has been completed and accomplished the next two missions. Phase three will accomplish the last mission.

Development of a Laboratory Durability Test for Asphalts, HR-124, 1967

Fruitful research on durability of paving asphalts may come from two approaches: The improvement of the asphalt for durability; The development of relatively rapid laboratory tests which will enable the design engineer to select or to specify an asphalt based on quality and to make a correct estimate of the service life of a selected asphalt when used in a specific paving mixture. Research Project HR-124, "Development of a Laboratory Durability Test for Asphalts," sponsored by the Iowa Highway Research Board is in the second category and was intended to be the initial stage of an overall study in the development of a durability test for paving asphalts.

Evaluation of the Chemical Durability of Iowa Fly Ash Concretes, HR-327, Phase I Progress Report, 1991

The following report summarizes research activities conducted on Iowa Department of Transportation Project HR-327, for the period April 1, 1990 through March 31, 1991. The purpose of this research project is to investigate how fly ash influences the chemical durability of portland cement based materials. The goal of this research is to utilize the empirical information obtained from laboratory testing to better estimate the durability of portland cement concrete pavements (with and without fly ash) subjected to chemical attack via the natural environment or the application of deicing salts. This project is being jointly sponsored by the Iowa Department of Transportation and the Iowa Fly Ash Affiliate Research group. The research work is also being cooperatively conducted by Iowa State University and Iowa Department of Transportation research personnel. Researchers at Iowa State University are conducting the paste and mortar studies while Iowa Department of Transportation researchers are conducting the concrete study.

Ultra Thin PCC Overlays, HR-559, Construction Report, 1995

A 11.6 km (7.2 mi.) portion of IA 21 in Iowa County from the junction of US 6 north to the junction of IA 212, was selected for the research project. The project was divided into 65 different test sections of a PCC overlay of an existing asphalt concrete (AC) surface with thicknesses of 50 mm (2 in.), 100 mm (4 in.), 150 mm (6 in.), and 200 mm (8 in.). The joint spacings for these sections were 0.6 m (2 ft.), 1.2 m (4 ft.), 1.8 m (6 ft.), 3.7 m (12 ft.), and 4.6 m (15 ft.). Joints were sealed if the thickness of the pavement was over 100 mm (4 in.), unless specified. Two types of polypropylene fibers, monofilament and fibrillated, were added to the conventional PCC mix for designated sections. Three additional sections consisted of an asphalt overlay for comparison with the concrete overlay. Three different base preparations were used on the project, consisting of: patching and scarifying, patching only, and cold-in-place recycling. Sensors were placed in various test sections to measure the temperature and strain during and after construction of the overlay. Pullout tests were also conducted at various locations. Beams cylinders were made for each of the PCC mixes and tested for flexural and compressive strengths. Evaluation of the performance will be conducted through December 31, 1999.

Dynamic Simulation Methods for Evaluating Motor Vehicle and Roadway Design and Resolving Policy Issues, 1990

This study had three objectives: (1) to develop a comprehensive truck simulation that executes rapidly, has a modular program construction to allow variation of vehicle characteristics, and is able to realistically predict vehicle motion and the tire-road surface interaction forces; (2) to develop a model of doweled portland cement concrete pavement that can be used to determine slab deflection and stress at predetermined nodes, and that allows for the variation of traditional thickness design factors; and (3) to implement these two models on a work station with suitable menu driven modules so that both existing and proposed pavements can be evaluated with respect to design life, given specific characteristics of the heavy vehicles that will be using the facility. This report summarizes the work that has been performed during the first year of the study. Briefly, the following has been accomplished: A two dimensional model of a typical 3-S2 tractor-trailer combination was created. A finite element structural analysis program, ANSYS, was used to model the pavement. Computer runs have been performed varying the parameters defining both vehicle and road elements. The resulting time specific displacements for each node are plotted, and the displacement basin is generated for defined vehicles. Relative damage to the pavement can then be estimated. A damage function resulting from load replications must be assumed that will be reflected by further pavement deterioration. Comparison with actual damage on Interstate 80 will eventually allow verification of these procedures.

Evaluation of Bond Retainage in Portland Cement Concrete Overlays by Infrared Thermography and Ground Penetrating Radar, HR-537, 1988

The purpose of this project was to evaluate the location and quantities of debonding in selected portland cement concrete (PCC) overlays. The project entailed an infrared thermographic survey and a ground penetrating radar survey of the PCC overlays to locate areas of debonding between the overlays and the original pavement. An infrared scanner is capable of locating these areas because of the temperature differential which is established between bonded and debonded areas under certain environmental conditions. A conventional video inspection of the top surface of the pavement was also completed in conjunction with the infrared thermographic survey to record the visual condition of the pavement surface. The ground penetrating radar system is capable of locating areas of debonding by detecting return wave forms generated by changes in the dielectric properties at the PCC overlay original pavement interface. This report consists of two parts; a text and a set of plan sheets. The text summarizes the procedures, analyses and conclusions of the investigation. The plan sheets locate specific areas of debonding, as identified through field observations.