An evaluation of cores sampled from six concrete pavements was performed. Factors contributing to pavement distress observed in the field were determined, including expansive alkali-silica reactivity and freeze-thaw deterioration related to poor entrained air-void parameters. A laboratory study to investigate the role of alkali-silica reactivity through accelerated mortar bar and concrete prism testing was proposed.
A copy of this report and its appendices can be found on the Michigan Department of Transportation website.
This project was designed to explore the feasibility of lowering the cementitious materials content (CMC) used in Wisconsin concrete pavement construction. The cementitious materials studied included portland cement, fly ash, and ground granulated blast furnace slag. For the first phase, mixtures were prepared using the current WisDOT aggregate grading specification. For the second phase, mixtures were prepared using an optimized (e.g. Shilstone) gradation. A variety of tests for fresh and hardened concrete were conducted to determine the viability of low CMC mixtures for use in concrete pavement.
The research resulted in several successful low CMC concrete mixtures in terms of workability, strength, and durability. Many unsuccessful low CMC concrete mixtures were also produced. The analysis of the data suggests a practical minimum CMC of 5.0 sacks/yd³ for concrete. However, successful mixtures containing fly ash were achieved at the CMC levels of 4.0 sacks/yd³ and 4.5 sacks/yd³ . The same minimum CMC limits were established in both the first and second phases of the research, regardless of the change in aggregate gradation.
Initially researched as NCHRP 18-13: Specifications and Protocols for Acceptance Tests of Fly Ash Used in Highway Concrete
Fly ash—a byproduct of coal combustion—is widely used as a cementitious and pozzolanic ingredient in hydraulic cement concrete. The use of coal fly ash (CFA) in concrete is increasing because it improves some properties of concrete and often results in a lower cost of concrete. However, the chemical and physical compositions of CFA influence constructability, performance, and durability and may contribute to problems, such as cracking and alkali-silica reactivity (ASR) in concrete pavements, bridge decks, and other highway structures. Regulatory requirements have also contributed to changes in CFA properties that may adversely affect concrete performance. In addition, current specifications and test methods do not adequately characterize CFA properties, address the effects of CFA characteristics on fresh and hardened concrete properties, or consider the alkali content of the cement. For example, carbon content of CFA is not usually determined directly but is often assumed to be approximately equal to the loss on ignition (LOI). Such inadequate characterization may lead to unwarranted restrictions on the use of suitable materials. Although a great deal of research has been performed on the effects of CFA characteristics on concrete properties, the research has not dealt with the applicability of current specifications to the fly ashes that currently are produced. In addition, existing test methods for sampling and testing CFA used in concrete do not adequately address the characterization of CFA or the performance aspects of highway concrete. Further research is needed to develop recommendations for improving CFA specifications and test protocols and thus help highway agencies better evaluate and use CFA that will provide acceptable structural performance and durability. NCHRP Project 18-13 was initiated to address this need.
Initially researched as Phase I – Joint Deterioration Study.
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.
A copy of the final report can be found at the National Concrete Pavement Technology Center website.
SPONSOR: WISCONSIN DEPARTMENT OF TRANSPORTATION (WISDOT)
PI: Lawrence Sutter
The two objectives of this research were to a) evaluate Class F and Class C fly ash sources for use in paving concrete and b) determine acceptable proportions of each ash type to use in paving mixtures. A combined study was performed involving characterization with respect to AEA adsorption using the foam index test, direct measurement of adsorption, and the iodine number test and a partial factorial experiment was conducted to evaluate concrete mixtures prepared using different fly ash, cement, and aggregate sources. The adsorption testing highlighted known inconsistencies of loss on ignition measurements. Freeze-thaw testing in 4% CaCl2 solutions indicated no statistical difference in performance with or without fly ash but fly ash type was a significant factor in mixtures that failed freeze-thaw testing. Compressive and flexural strength followed the classical behavior expected of fly ash mixtures. Maturity showed the largest impact of fly ash addition. Overall the Class F and Class C ash sources performed well and using either at substitution levels up to 30% is recommended. Additional scrutiny of some Class F sources, with respect to freeze-thaw performance, is warranted. Use at higher levels should be done only after performance testing of the specific combination of materials to be used at the job-mix proportions.
A copy of this report can be found on the Wisconsin Department of Transportation website.
Sponsor: US Department of Transportation Research and Innovative Technology Administration (RITA)
PI: Tess Ahlborn
The condition of the nation’s infrastructure has gained increased attention in recent years, primarily as a result of catastrophic events such as the I-35W collapse in Minneapolis. However, deteriorating transportation infrastructure has burdened transportation agencies for many years. Bridges continue to age, and funds for the repair and replacement of this infrastructure are insufficient at current funding levels. Remote sensing technologies, which enables non-contact data collection at great distances, offer the ability to enhance inspection and monitoring of bridges. Research Objectives The objective is to explore the use of remote sensing technologies to assess and monitor the condition of bridge infrastructure and improve the efficiency of inspection, repair, and rehabilitation efforts to develop unique signatures of bridge condition. Methodology Remote sensing technologies will be correlated with in-place sensors to obtain bridge condition assessment data without the need to place heavy instrumentation on the structure. This information will then be analyzed by a computer decision support system to develop unique signatures of bridge condition. Monitoring how these signatures change over time will provide state and local engineers with additional information used to prioritize critical maintenance and repair of our nation’s bridges. The ability to acquire this information remotely from many bridges without the expense of a dense sensor network will provide more accurate and near real-time assessments of bridge condition. Improved assessments allow for limited resources to be better allocated in repair and maintenance efforts, thereby extending the service life and safety of bridge assets, and minimizing costs of service-life extension.
The mission of the TMRC is to provide expertise and facilities to support the Michigan Department of Transportation (MDOT)’s infrastructure materials engineering needs through technical services and engineering support. The TMRC also provides education and outreach to transportation officials in the state.
The center activities for 2016 provide a continuation of the past activities of the TMRC. The main center activities will continue to be technical support through material testing and analysis in conjunction with our innovative research investigations, education and outreach in support of MDOT’s mission.
The efforts of the TMRC are divided into two components; Core Services and Supplemental Services.
Core Services include education, research support and communications. Education activities include employment of both undergraduate and graduate students on TMRC projects and provide lectures on TMRC projects to a wide range of audiences that interact with MDOT or other transportation related organizations. Research support provides the administration of the TMRC contract and dissemination of TMRC project results to MDOT and at national meetings such as the Transportation Research Board (TRB). Communications include conveyance of the TMRC’s analysis, forensic evaluations and recommendations for field implementation through a written report and may be published in peer-reviewed journals or via direct meetings with MDOT personnel.
Supplemental services are those associated with specific technical projects and investigations as specified by the MDOT project manager through a formal request process.