Isaac L. Howard

Mississippi State University

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Co-Authors

Ben C. Cox

U.S. Army Engineer Research and Development Center

Jesse D. Doyle

U.S. Army Engineer Research and Development Center

Ashley S. Carey

Mississippi State University

Kimberly Warren

Pennsylvania Department of Health

Jay Shannon

U.S. Army Engineer Research and Development Center

W. Griffin Sullivan

Iowa Department of Transportation

Farshid Vahedifard

Tufts University

Walter S. Jordan

Carrier (United States)

Braden T. Smith

LUNGevity Foundation

Gaylon L. Baumgardner

Carrier (United States)

Cooperative Institutions

Mississippi State University

U.S. Army Engineer Research and Development Center

United States Army

Geotechnical and Structures Laboratory

United States Army Corps of Engineers

ORCID

United States Department of the Army

University of Illinois Urbana-Champaign

Walker (United States)

University of Alabama

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Research Field

Comparing Pressure Aging Vessel Time to Field Aging of Binder as a Function of Pavement Depth and Time

Transportation Research Record Journal of the Transportation Research Board (2018)

Braden T. Smith Isaac L. Howard Walter S. Jordan Codrin Daranga Gaylon L. Baumgardner

The AASHTO R28 pressure aging vessel (PAV) binder conditioning protocol has been heavily used for over two decades as part of purchasing specifications. Many paving industry changes have occurred since PAV was implemented in the early 1990s. This paper provides discussion with respect to a controlled test section in which the exact binders from construction were subjected to multiple PAV times and compared with properties observed after 2 or 4 years of field aging. The data suggests that 2 and 4 years of field aging were best simulated by 21 h and 45 h of PAV time for binders extracted from the top 1.3 cm of the pavement surface. For binders extracted from 5.0 to 6.3 cm below the pavement surface (i.e., at depth), 2 and 4 years of field aging were best simulated by 3 and 14 h of PAV conditioning, respectively. These results indicate that a PAV rate of 11 h per year of simulation seemed adequate for binders aged on the pavement surface, and a PAV rate of 3 h per year of simulation seemed most reasonable for binders aged at depth. Considering these rates, the current 20-h protocol in R28 seems to simulate roughly 2 years of aging at the pavement surface and about 6.5 years at depth. The amount of field aging simulation at depth is within the range of 5 to 10 years of aging suggested by R28.

Accelerated aging

10.1177/0361198118790836

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Citations (17)

Use of Portland Cement and Polymer Fibers to Stabilize Very High Moisture Content Fine-Grained Soils

Advances in Civil Engineering Materials (2013)

William D. Carruth Isaac L. Howard

Abstract Very high moisture content fine-grained soils are plentiful in wetlands, river basins, and after floods. They can be problematic and require disposal facilities to be constructed in some instances. Any means of handling or re-using these materials is potentially appealing. Using chemical stabilization (e.g., Portland cement) can enhance strength, but the resulting product can be brittle. Adding polymer fibers as a secondary stabilizer can add noticeable ductility while offering at least some strength and stiffness benefits. Two fiber types and Portland cement were mixed into three soils with varying properties at elevated moisture content and tested for shear strength via: (1) unconfined compression (UC), and (2) with hand-held gages. Fiber-reinforced and non-fiber-reinforced specimens were compared in terms of shear strength, elastic modulus, and ductility. Fiber addition, in general, increased shear strength, and the level of increase was affected by soil organic content. Ductility was considerably improved by fiber addition. Correlations were developed by soil type so that conservative elastic modulus values could be calculated from shear strength, and it was observed that fibers increased elastic moduli values.

Ductility (Earth science)

Brittleness

Shear Strength

10.1520/acem20120006

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Citations (16)

Time Delay Effects on Compactability of Soil-Cement Materials during Proctor Testing

Transportation Research Record Journal of the Transportation Research Board (2021)

W. Griffin Sullivan Isaac L. Howard

The Proctor test method, as specified in AASHTO T134 and ASTM D558, continues to play a vital role in design and construction quality control for soil-cement materials. However, neither test method establishes a methodology or standardized protocols to characterize the effects of time delay between cement addition and compaction, also known as compaction delay. Compaction delay has been well documented to have a notably negative effect on compactability, compressive strength, and overall performance of soil-cement materials, but specification tools to address this behavior are not prevalent. This paper aims to demonstrate the extent of compaction delay effects on several soil-cement mixtures used in Mississippi and to present recommended new test method protocols for AASHTO T134 to characterize compaction delay effects. Data presented showed that not all soil-cement mixtures are sensitive to compaction delay, but some mixtures can be very sensitive and lead to a meaningful decrease in specimen dry density. Recommended test method protocols were presented for AASHTO T134 and commentary was presented to provide state Departments of Transportation and other specifying agencies a few examples of how the new compaction delay protocols could be implemented.

Proctor compaction test

Soil cement

Soil Compaction

10.1177/0361198121998700

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Citations (7)

Emergency paving using hot-mixed asphalt incorporating warm mix technology

International Journal of Pavement Engineering (2012)

Isaac L. Howard Jesse D. Doyle James Michael Hemsley Gaylon L. Baumgardner L A Cooley

This paper presents results of a study on hot-mixed and warm-compacted asphalt incorporating warm mix technologies for use in emergency construction following a natural disaster. Case studies were first reviewed to investigate feasibility of the concept. Next, an overall emergency paving framework was developed, complemented by a two-component laboratory investigation. Component one developed a series of short-term ageing protocols for use in preparation of test specimens; component two evaluated those specimens for compactability and rut resistance. Results indicated that (1) material could be hauled up to 6 h and still be effectively used in emergency paving, (2) the two warm mix additives studied improved compactability of hot-mixed and warm-compacted asphalt and (3) rut resistance was acceptable for emergency applications. A discussion on the post natural disaster permanent residual value of the hot-mixed and warm-compacted material is also provided.

Asphalt pavement

10.1080/10298436.2012.721549

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Citations (16)

Simulation-Based Individualized Airfield Pavement Maintenance Recommendations to Reduce Total Cost of Ownership for the U.S. Air Force

Engineering Management Journal (2021)

Thomas M. Synovec Isaac L. Howard

The U.S. Air Force (USAF) estimates it has a $33 billion deferred maintenance backlog within its $263 billion infrastructure portfolio. While the USAF has had recent success advocating for additional funding, new investment and maintenance strategies are ultimately needed to reduce the cost of ownership of its infrastructure while addressing risk and performance-based requirements. This paper documents a simulation-based methodology to implement a portfolio-wide, lowest life-cycle cost strategy projected to provide a $126 million annualized savings. The RAMPSS algorithm developed through this research provides a strategic, decision-making support tool to help reverse the growing maintenance backlog. Analysis from RAMPSS of the USAF’s pavement portfolio suggests that airfields are generally more cost-effective to maintain if kept in better conditions with strategies other than localized preventative maintenance.

Investment

Planned maintenance

10.1080/10429247.2021.1940045

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Citations (1)

Geotextile tubes and beneficial reuse of dredged soil: applications near ports and harbours

Proceedings of the Institution of Civil Engineers - Ground Improvement (2017)

Isaac L. Howard Farshid Vahedifard J.M. Williams Chris Timpson

Geotextile tubes can offer a sustainable solution for beneficial reuse of dredged soil near ports and harbours. Dredging and subsequent handling of dredged materials is one of the main challenges that may adversely impact the efficient port operation. Additional challenges facing some ports are related to the availability of land. If large quantities of dredged soil are stored on site, land availability can further decrease. Geotextile tubes have already been used in various applications in and around ports and harbours. However, there are several untapped opportunities with geotextile tubes as a sustainable means of beneficially reusing dredged soils to positively impact port operations. This paper summarises properties and considerations related to dredged materials and geotextile tubes. The key features of projects conducted are presented to exemplify the potential of including geotextile tubes in various applications. The applications include dewatering, lightweight backfill over compressible soil, contaminated sediment handling, shallow and stacked geotextile tube walls, engineering with nature by way of vegetation establishment and land creation or land use. The case studies examined demonstrate the technical, environmental and economic advantages that geotextile tube applications can offer for beneficial reuse of dredged soil near ports and harbours.

Geotextile

Dredging

Port (circuit theory)

Dewatering

10.1680/jgrim.17.00059

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Citations (20)

Use of Hot-Mix Warm-Compacted Asphalt in Construction

Transportation Research Board 90th Annual MeetingTransportation Research Board (2011)

Isaac L. Howard Jesse D. Doyle Mike Hemsley Gaylon L. Baumgardner L A Cooley

Warm mix additives have the potential to be advantageous in a variety of asphalt construction applications. Applications that would not have been considered a few years ago are beginning to be considered. Long haul distances provide numerous construction advantages. This paper presents the results of a study of hot mixed-warm compacted asphalt incorporating warm mix additives for use in emergency construction following a hurricane. A two component investigation was performed. Component one developed a series of short term aging protocols for use in preparation of test specimens for component two. Component two evaluated compactability and rut resistance of the mixtures. Results indicated that the two warm mix additives studied improved compactability of hot mixed-warm compacted asphalt, and that rut resistance was acceptable for emergency applications. Discussion related to the fate of the material after all emergency trafficking is complete was also provided.

Asphalt pavement

Component (thermodynamics)

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Citations (4)

Measuring aggregate and binder interaction by way of mixture tests before and after field ageing

Proceedings of the Institution of Civil Engineers - Construction Materials (2018)

Bradley S. Hansen Isaac L. Howard

Mixture properties were measured before and after field ageing to evaluate how aggregates, binder and environmental effects interact. To isolate these effects, very simple mixes (usually comprising one aggregate source and one binder) were designed and tested. The results showed that clear differences existed before and after field ageing where the same binder was utilised with different aggregates. Aggregate effects were magnified by field ageing. The results agree with a literature review that has documented aggregates' influence in response to environmental effects such as ageing for many years. When combined with the literature reviewed, the data collected should help ongoing discussions within the asphalt industry related to mixture testing and how to capture environmental effects/ageing. To truly capture in-service conditions, mixture conditioning that can simulate the simultaneous effects of the environment, aggregates and binder is likely to be the most effective approach based on the data reported in this paper. This is especially true today where mixtures are often very complex and contain many virgin and post-consumer ingredients.

Service life

10.1680/jcoma.17.00070

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Citations (2)

Editorial

Proceedings of the Institution of Civil Engineers - Ground Improvement (2018)

Isaac L. Howard

10.1680/jgrim.2018.171.4.183

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Citations (0)

Columbus Mississippi Field Aging and Laboratory Conditioning Study: Air Force Base and Single Aggregate Source Reference Asphalt Mixtures

Isaac L. Howard Bradley S. Hansen Braden T. Smith

Base (topology)

Central air conditioning

Source

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Citations (1)