Institute for Transportation

About the research

About the research

The work to be covered by this project is the development of a Manual of Practice that will educate practicing engineers about when and how to use concrete mixtures containing ternary cementitious systems.

The information to be provided will be based on the findings of research recently completed through the ternary pooled fund and through a federal cooperative agreement with the National Concrete Pavement Technology Center. The manual will serve as a textbook to accompany a training program being developed by ACT (American Concrete Institute) for FHWA.

The research work has shown that ternary mixtures can be successful in a number of applications and provide enhanced performance while improving sustainability. Such mixtures do perform differently from conventional concrete, and the manual will document the benefits that may be expected as well as provide guidance for the precautions that need to be taken to ensure successful implementation.

About the research

Pavement design techniques have advanced to incorporate modern technology and scientific-based models to improve pavement construction, performance, maintenance, and rehabilitation. The reliability of these models depends upon input data gathered in the field via pavement instrumentation. There is a demonstrated lack of rigid pavement instrumentation and experimental field data nationally, leading to a shortage of pavement field data required to examine, model, and simulate the interaction of pavement components in the field (such as pavement base material, slab, tie bar, etc.). In order to rely upon more scientific-based models to improve pavement systems (and ultimately reduce pavement life-cycle costs), more data is required to refine existing and new pavement performance models.

Perhaps the most commonly used and popularly accepted model-based, modern approach to highway design is embodied in the Mechanistic-Empirical Pavement Design Guide (MEPDG), which incorporates models embedded in dedicated software (such as AASHTOWare Pavement ME Design) to predict pavement performance in greater detail than prior predictive models. Such dedicated software incorporates scientific data such as material mechanics, climate data, axle-load spectra, and other factors. Full implementation of the Mechanistic-Empirical Pavement Design by state departments of transportation (DOTs) requires customization or calibration/validation of the software for variables and pavement conditions at state and local levels. This in turn requires the collection of region-specific field data on climate, material properties, load response, and pavement performance for use in calibration and implementation of the software. Mechanistic-Empirical Pavement Design software uses these data inputs to more accurately simulate the load response of pavements and long-term pavement performance. Local calibration of the software involves comparing long-term performance simulation results to actual performance data at local sites (if possible) or from matching pavements in the Federal Highway Administration Long-Term Pavement Performance (LTPP) database. Several numerical models are available to predict pavement performance, and these models are an effective tool to predict the likelihood of pavement damage and longevity. These numerical models also enable improvements in road design methods, whether for new or rehabilitated pavements, that will help mitigate the problems of load-induced damage. However, most of these models have not been calibrated against actual field data obtained under realistic conditions.

To enhance the effectiveness of these models and to assist in their application, instrumented test sections of pavement can be monitored and data gathered to monitor performance factors (such as soil pressure, pavement temperature, strains and deflections caused by daily changes in temperature within the pavement, along with air temperature, wind speed, relative humidity, solar radiation, and precipitation). The pavement construction process can also be monitored, and the materials used in the pavement can be tested in the laboratory or in the field (using non-destructive testing) to ascertain material property information. As pavement systems are highly nonlinear in their responses to loads and load related strains, field data collected via instrumentation helps indicate which parameters need to be emphasized in the models to describe pavement performance and response to conditions. Data from the laboratory tests (or from non-destructive field testing) is input to the model to predict the road response. The predicted response is then compared to the measured response. A sensitivity analysis also helps determine which parameters should be adjusted to best fit actual conditions. Also the LTPP database can be used for calibration in addition to data related to material properties, traffic data, and pavement performance data provided by other DOTs. In the long term, the calibrated model is used in conjunction with existing Mechanistic-Empirical design models and Mechanistic-Empirical Pavement Design software to improve the design method. The data can be put into a format directly useful to designers and engineers.

Since 2001, the New York State Department of Transportation (NYSDOT) has significantly invested in instrumenting test pavement sections to acquire local data to improve calibration of Mechanistic-Empirical Pavement Design software. The instrumented field pavements in New York include I-490, I-90, and I-86. The installed sensors are still functioning to an extent that permits data collection of additional useful scientific information, and I-490 is providing high-quality data that will positively impact future design, construction, and maintenance of roads. As NYSDOT progresses in its adoption of the Mechanistic-Empirical Pavement Design approach, the test sections it has invested in over the past decade will play a key role in the validation of that approach. In addition to collecting load response data, it will be possible to assess the long-term performance of these pavements. (Mechanistic-Empirical Pavement Design requires both.)

An extended study will verify that the performance benefit is maintained in the long term and that these designs will save money in the long run. Additionally, on I-86, three different concrete pavement rehabilitation techniques were tested previously, with some differences in the performance. Extended study will provide a definitive conclusion of which method provides the best performance and is the most economical. Several states previously have conducted projects using instrumentation in pavement test sections to collect pavement performance data. In addition to the three I-86 sections instrumented to measure deflection, strain, and temperature in order to study different techniques of portland cement concrete (PCC) pavement rehabilitation, additional sections on I-490 and two sections on I-90 are being used to measure the effects of varying base types.

Other states such as Ohio, Minnesota, and Delaware, among others, have instrumented concrete sections to collect data which can be used for analysis. The sharing of data from multiple DOTs and geographic regions (via resources such as the LTPP database) adds significant value to pavement performance modeling tools and to the body of scientific knowledge; this pooled approach among multiple sources/DOTs also offers a more efficient and economical manner than on an individual basis.

The objectives of this study include: (1) Collecting load response and performance data and environmental monitoring at selected test pavements for four years; (2) installing new instrumented sections as needed for a better understanding of rigid pavement response, including monitoring for the duration of the project; (3) determining the impact of a base and other components (such as dowel bars, tie bars, etc.) on long-term performance of rigid pavement utilizing the data acquired and other nationally available data on the topic; (4) documentation of the processes, procedures, and findings; and (5) finalization of the rigid pavement design catalog with local validation and calibration of mechanistic-empirical models.

About the research

Concern has been expressed about the deicer scaling resistance of concrete containing slag, especially when the dosage of slag exceeds 50% of the total cementitious material in the mixture. Much of the concern appears to be based on the results of laboratory scaling tests based on ASTM C 672, despite indications that such mixtures often perform well in the field.

The initial phase of this study showed that construction-related issues played a bigger role in the observed scaling performance than did the amount of slag in the concrete mixture. The work also indicated that the test method (ASTM C 672) may be more severe than most environments. A second phase developed an alternative laboratory test method to ASTM C 672 that would better represent the field performance of concretes, based on a method from the Canadian Quebec Ministry of Transportation.

The work described in this report was to repeat some tests using similar materials in a second laboratory to evaluate repeatability of the test methods.

About the research

Nationally, there is concern regarding the design, fabrication, and erection of horizontally-curved steel girder bridges due to unpredicted girder displacements, fit-up, and locked-in stresses. One reason for the concerns is that up to one-quarter of steel girder bridges are being designed with horizontal curvature. The concerns are significant enough that a National Cooperative Highway Research Program (NCHRP) research problem statement was developed and given high priority for funding.

It is also noted that an urgent need exists to reduce bridge maintenance costs by eliminating or reducing deck joints. This can be achieved by expanding the use of integral abutments to include curved girder bridges.

The long-term objective of this effort is to establish guidelines for the use of integral abutments with curved girder bridges. The primary objective of this work was to monitor and evaluate the behavior of six in-service, horizontally-curved, steel-girder bridges with integral and semi-integral abutments. In addition, the influence and behavior of fixed and expansion piers were considered.

About the research

State highway agencies are increasingly intersted in using recycled asphalt shingles (RAS) in hot mix asphalt (HMA) applications, yet many agencies share common questions about the effect of RAS on the performance of HMA. Previous research has allowed for only limited laboratory testing and field surveys. The complexity of RAS materials and lack of past experiences led to the creation of Transportation Pooled Fund (TPF) Program TPF-5(213). The primary goal of this study is to address research needs of state DOT and environmental officials to determine the best practices for the use of recycled asphalt shingles in hot-mix asphalt applications.Agencies participating in the study include Missouri (lead state), California, Colorado, Illinois, Indiana, Iowa, Minnesota, Wisconsin, and the Federal Highway Administration. The agencies conducted demonstration projects that focused on evaluating different aspects (factors) of RAS that include RAS grind size, RAS percentage, RAS source (post-consumer versus post-manufactured), RAS in combination with warm mix asphalt technology, RAS as a fiber replacement for stone matrix asphalt, and RAS in combination with ground tire rubber. Field mixes from each demonstration project were sampled for conducting the following tests: dynamic modulus, flow number, four-point beam fatigue, semi-circular bending, and binder extraction and recovery with subsequent binder characterization. Pavement condition surveys were then conducted for each project after completion.

The demonstration projects showed that pavements using RAS alone or in combination with other cost saving technologies (e.g., WMA, RAP, GTR, SMA) can be successfully produced and meet state agency quality assurance requirements. The RAS mixes have very promising prospects since laboratory test results indicate good rutting and fatigue cracking resistance with low temperature cracking resistance similar to the mixes without RAS. The pavement condition of the mixes in the field after two years corroborated the laboratory test results. No signs of rutting, wheel path fatigue cracking, or thermal cracking were exhibited in the pavements. However, transverse reflective cracking from the underlying jointed concrete pavement was measured in the Missouri, Colorado, Iowa, Indiana, and Minnesota projects.

About the research

The Institute for Transportation (InTrans) at Iowa State University was a subcontractor to the Minnesota Department of Transportation on this transportation pooled fund study (TPF-5(132)). InTrans researchers made signifinant contributions on this project and links to the project pages are provided here.

About the research

Premature deterioration of concrete at the joints in concrete pavements and parking lots has been reported across the northern states. The distress may first appear as shadowing when microcracking near the joints traps water, or as cracks parallel to and about 1 inch from the saw cut. The distress later exhibits as a 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 the prevention of further distress, the work to date has contributed to advancing the state of the knowledge.

About the research

Bridges constitute the most expensive assets, by mile, for transportation agencies around the US and the world. Most of the bridges in the US were constructed between the 1950s and the 1970s. Consequently, an increasing number of bridges are getting old and requiring much more frequent inspections, repairs, or rehabilitations to keep them safe and functional. However, due to constrained construction and maintenance budgets, bridge owners are faced with the difficult task of balancing the condition of their bridges with the cost of maintaining them.

Bridge maintenance strategies depend upon information used to estimate future condition and remaining life of bridges. The desire of many departments of transportation (DOTs) is to augment their existing inspection process and maintenance system with a system that can objectively and more accurately quantify the state of bridge health in terms of condition and performance, aid in inspection and maintenance activities, and estimate the remaining life of their bridge inventory in real time. To better manage bridge inventories, tools that can accurately predict the future condition of a bridge, as well as its remaining life, are required.

One of the key requirements for an effective infrastructure management system is the establishment of a structural health monitoring (SHM) system. An SHM system traditionally consists of a network of monitoring sensors, data acquisition, and communication hardware and software capable of carrying out bridge condition assessments in real-time and accurately and objectively predicting the health of the infrastructure components and systems.

For this project, the research team developed an automated SHM system that could detect bridge damage and estimate load ratings of bridges, as well as models to develop predictions for future condition ratings of bridges. The SHM system and models were then used to develop a bridge maintenance prioritization system for DOTs to augment current bridge management practices.