Sanjaya Senadheera

Survey of state practices to control skid resistance on hot-mix asphalt concrete pavements

A nationwide survey on design methods for achieving adequate skid resistance on hot-mix asphalt concrete pavements was conducted. Information was collected on the design practices used by 48 state departments of transportation (DOTs) in the contiguous United States. Survey findings show that the emphasis placed on the skid resistance aspects in various state DOT design procedures vary considerably. Based on the data collected, 21 out of 48 state highway agencies either do not have any design guidelines specifically addressing pavement skid behavior or assume that adequate skid resistance may be ensured through proper mix design. The general approach used by these agencies involves frequent monitoring of pavements to identify pavements with skid-related problems so that appropriate action may be taken. Survey findings indicated that state DOTs that consider skid resistance in their design procedures emphasize controlling the quality of coarse aggregates used in pavement surface course construction. The procedures used for aggregate qualification, however, vary significantly from one state agency to another. Some state DOTs rely on simple aggregate classification methods based on aggregate type, whereas others perform detailed laboratory evaluation. The laboratory test procedures that are most commonly used in evaluating aggregate frictional properties are the polish value test, acid insoluble residue test, and petrographic analysis. In addition to laboratory testing, Florida, Kentucky, Pennsylvania, and Texas use alternative procedures to qualify aggregates based on their field skid performance.

Chip Seal Maintenance: Solutions for Bleeding and Flushed Pavement Surfaces

This study summarizes the research directed at identifying maintenance solutions for bleeding and flushed pavements surfaced with a chip seal. Factors that contribute to bleeding and flushed chip seals pertain to aggregates, binders, traffic, environment, and construction. No better advice exists for dealing with bleeding and flushed chip seals than to avoid the problem from the outset by employing a preventive maintenance perspective. Bleeding is an immediate maintenance problem that must be addressed; corrective maintenance, or in some cases emergency maintenance, would be done. Basic approaches to treat bleeding include bridging over the live asphalt by applying aggregate of various types and gradations, cooling off the pavement surface by applying water with or without additives, and removing the bleeding asphalt and rebuilding the pavement seal. Flushing, in contrast to bleeding, is typically not a maintenance problem that must be addressed immediately. Basic approaches to treat flushed chip seals are to retexture the existing surface or to add a new textured surface over the flushed pavement. Three promising areas for further research and implementation relative to bleeding and flushing solutions include the uses of lime water, ultrahigh pressure water cutting, and the racked-in seal at intersections.

Use of Hydrated Fly Ash as a Flexible Base Material

Common uses for fly ash, such as soil stabilization and cement replacement, account for less than 20 percent of the fly ash produced in the United States. Therefore, finding other bulk uses for fly ash is important. One such potential application is hydrated fly ash as a base material. The Texas Department of Transportation (TxDOT) is working to produce specifications to incorporate hydrated fly ash as a flexible base material. High-calcium Class C fly ash has a self-hydrating capability in the presence of moisture. Class C fly ash produced from coal power plants using lignite and subbituminous coal is mixed with water, dumped in large pits, and left to hydrate for a period of 3 to 6 weeks. The result is a hard, homogeneous mass of hydrated fly ash that can be mined to produce a construction aggregate much like limestone. TxDOT has used this material on several test projects. It has a desirable compressive strength, but in some instances its adhesion to seal coats has been a problem. Laboratory studies in...

Rational Use of Terminal Anchorages in Portland Cement Concrete Pavement

Portland cement concrete (PCC) pavements have long been thought to expand and push bridge structures, with bridge damage resulting. To protect bridge structures from expanding PCC pavements, three terminal systems are currently used in Texas: anchor lug (AL), wide flange (WF), and expansion joint (EJ). Even though the Texas Department of Transportation uses all three systems in continuously reinforced concrete pavement (CRCP), the effectiveness of these three systems has not been fully evaluated. The parameters affecting CRCP movement near bridge terminal areas are investigated: whether thermal expansion of CRCP is damaging bridge structures, and if so, which terminal type is most cost-effective. Extensive field evaluations reveal that slab movement at the end of the CRCP are substantially restrained by subbase friction. Slab length from the end of the CRCP that significantly contributes to slab movement is limited to about 200 ft (60.96 m) for the CRCP system with asphalt base typically used in Texas. Slab movement rates due to seasonal temperature variations are larger than daily slab movement rates. The movement at the end of the CRCP can be accommodated by a simple EJ with subbase friction, which can be achieved with typical asphalt-stabilized base. The use of an AL system is not needed to restrain concrete slab movement. The benefits of WF and AL systems are doubtful when one considers that their cost is higher than that of the simpler EJ system.

Strength and Shrink/Swell Behavior of Highly Plastic Clay Treated with Geopolymer

This paper presents findings from an experimental study in which a novel, non-energy intensive, environmentally-friendly stabilizer known as geopolymer was used for stabilization of a highly plastic clay. Two forms of the stabilizer were synthesized, one using metakaolin (MK) and the other using fly ash (FA) as the alumino-silicate precursor. The paper describes the process of geopolymer synthesis as well as quality control tests conducted during geopolymer synthesis. Synthesized geopolymers were analyzed using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX). The paper also presents results obtained from a comprehensive laboratory test program that examined the effectiveness of the stabilizer in improving strength and controlling moisture induced swelling of a highly plastic clay soil. The geopolymer content of the soil ranged from 3% to 15% by weight ratio. SEM-EDX and XRD were performed to investigate the treated specimen for uniformity and stabilization mechanism. The data obtained from unconfined compressive strength tests conducted after seven days of curing showed three- to four-fold improvement in strength for geopolymer stabilized soils with MK geopolymer consistently providing better performance than FA geopolymer. The results from one-dimensional swell tests indicated significant reduction of swell behavior in FA geopolymer treated specimens while no improvement in swell behavior was observed in MK treated soil. This study demonstrates that, while geopolymers can overcome many limitations that exist in traditional stabilizers, the strength and swell performance of geopolymer stabilized clay soil can vary significantly depending on the source of alumino-silicate used in the production of the geopolymer.

Expenditure on Snow and Ice Control for Roadway Maintenance

AbstractThis paper presents the relationships between various winter weather conditions and the total expenditure on purchasing and applying snow and ice control materials and operation costs (labo...

Implementation of ultra high pressure water cutting for treatment of flushed chip seals in the US

This paper discusses implementation of ultra-high pressure (UHP) water cutting as a pavement maintenance strategy based on the first large-scale application of UHP water cutting for treatment of flushed chip seals in the USA. Data are from 13 field sites located in four different climatic regions in Texas. Production rates and treatment costs are sensitive to the UHP water cutter equipment, road surface condition, environmental factors and other variables. Production rates for UHP water cutting under Texas road conditions ranged from 490 m2/h to 1560 m2/h, average 830 m2/h, for treatment of light to heavy flushing. Turn-key unit costs for UHP water cutting varied from US

Ultrahigh-Pressure Watercutting Treatment of Flushed Chip Seals in the United States: Effectiveness and Durability

1.77/m2 to US

Volume-to-Capacity Estimation of Signalized Road Networks for Metropolitan Transportation Planning

2.08/m2 for an average savings of 41% as compared to the cost of typical Texas maintenance solutions for treatment of flushed chip seals. Overall, UHP water cutting shows positive results in terms of treatment effectiveness, durability and production considerations.

A Testing and Evaluation Protocol to Assess Seal Coat Binder-Aggregate Compatibility

This paper discusses the effectiveness and durability of ultrahigh-pressure (UHP) watercutting as a preventive or corrective maintenance strategy to treat flushed chip seals in the United States. The data presented here originated from an implementation project conducted in 2011–2012 in which UHP watercutting was used to treat chip-seal-surfaced roads at 13 field sites located in four FHWA climatic regions in Texas. Initial treatment effectiveness varied depending on the site but typically was high, with an average increase in pavement texture of about 200% and an average increase in friction of about 135%. Therefore, the UHP water-cutting treatment did improve pavement texture and friction. Follow-on monitoring of the field test sites over an 18-month period showed that the surface friction and texture values achieved at treatment survived at or above the desirable performance threshold for seven of 13 sites, and these values survived at or above the maintenance threshold for 12 of 13 sites. The life expectancy achieved by UHP watercutting varied in terms of pavement texture and friction values. Predictive decay models indicated that texture and friction values would last 1 or more years at 90% of the test sites. For 40% of the test sites, the treatment would last four or more years, and these life expectancy estimates were consistent with published data. Overall, the results from this study were promising for the application of UHP watercutting to chip seal maintenance in the United States.