<?xml version="1.0" encoding="utf-8"?><rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom"><channel><title>TRB Publications Index</title><link>http://pubsindex.trb.org/</link><atom:link href="http://pubsindex.trb.org/common/TRIS Suite/feeds/rss.aspx?tc=NN%3ARbmdhbfg%2A" rel="self" type="application/rss+xml" /><description></description><language>en-us</language><copyright>Copyright © 2015. National Academy of Sciences. All rights reserved.</copyright><docs>http://blogs.law.harvard.edu/tech/rss</docs><managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor><webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster><image><title>TRB Publications Index</title><url>http://pubsindex.trb.org/Images/PageHeader-wTitle.png</url><link>http://pubsindex.trb.org/</link></image><item><title>Assessment of the Impact of Fiber Types on the Performance of Fiber-Reinforced Hot Mix Asphalt</title><link>http://pubsindex.trb.org/view/1692969</link><description><![CDATA[This study aims to evaluate the impact of fiber types on the performance of hot mix asphalt (HMA) mixtures. Specifically, the impacts of fiber type on HMA mix design and laboratory performance are investigated. Four types of fiber (fiberglass, basalt, carbon, and polyolefin/aramid blend) were used to produce four fiber-reinforced HMA mixes, and a control mix without fibers was also prepared. The fiber dosage rates used in this study were 0.16% (fiberglass, basalt, and carbon) and 0.05% (polyolefin/aramid) by total mixture weight, based on manufacturer recommendations. Two mixing procedures for introducing fibers into HMA were also evaluated: dry and 15-s dispersion methods. The dry method involved mixing the fibers with aggregates before the addition of asphalt binder while the 15-s dispersion method involved adding the fibers into the mix every 15?seconds (as aggregates were coated by asphalt binder during the mixing process). All the HMA mixtures (unreinforced and fiber-reinforced) were then subjected to several different laboratory performance tests: dynamic complex modulus, Cantabro durability, asphalt pavement analyzer, flow number, and indirect tensile strength. Analysis of variance was conducted to evaluate statistically the impact of fibers on mix performance. Results showed that fibers affected the volumetric properties, mix durability, and rutting resistance of HMA mixes. It was also found that the process for introducing fibers into the mix (i.e., mixing method) affected the consistency of fiber-reinforced HMA samples. Overall, the results of this study showed that the use of fibers improved the rutting and durability performance of asphalt mixtures in the laboratory.]]></description><pubDate>Wed, 08 Apr 2020 08:54:12 GMT</pubDate><guid>http://pubsindex.trb.org/view/1692969</guid></item><item><title>Fiberglass ACE Mat as a Temporary, Rapid Alternative to Unpaved Road Surfaces</title><link>http://pubsindex.trb.org/view/1690356</link><description><![CDATA[Temporary, low-volume roadways often challenge designers with balancing cost of improving weak soils with the performance requirements of the intended application. Construction costs can be high, depending on the strength of the native soil and improvements required to sustain the vehicle loadings that are applied. In an effort to provide a solution for ground improvement that balances cost, logistics, and performance, the U.S. Army Corps of Engineers (USACE) developed a multipurpose, medium-duty matting system constructed of woven fiberglass reinforcement and polyester resin. This paper discusses three demonstrations in which the U.S. Army Corps of Engineers Mat (ACE Mat) was used as a surfacing for temporary roads. First, ACE Mat was used to support weak soil crossings for logging operations at the Apalachicola National Forest in Florida. Second, the matting was tested for its capability to support loads from a U.S. Marine Corps Medium Tactical Vehicle Replacement (MTVR) and a U.S. Army M1 Abrams main battle tank crossing sand and silt soils at the U.S. Army Engineer Research and Development Center in Mississippi. Finally, ACE Mat was demonstrated as a ground surfacing to stabilize a riverbank during temporary bridging training at Fort Knox, Kentucky. Attributes and performance characteristics of ACE Mat in comparison to typical unpaved road design and construction using compacted aggregate are also discussed.]]></description><pubDate>Tue, 03 Mar 2020 16:02:56 GMT</pubDate><guid>http://pubsindex.trb.org/view/1690356</guid></item><item><title>Comparing the Performance of Fiberglass Grid with Composite Interlayer Systems in Asphalt Concrete</title><link>http://pubsindex.trb.org/view/1439450</link><description><![CDATA[Geosynthetics, such as fabrics, grids, and composites, were introduced to asphalt pavements to mitigate reflective cracking or the creation of moisture barriers or both. Reinforcing interlayer systems, such as grids, have been shown to be effective in retarding the reflection of cracks in the underlying pavement into the upper layers. However, the effect of different interlayer systems on the performance of the pavement varies. The aim of this research was to compare the effects of fiberglass grids, paving fabric, and paving mat systems on the fatigue and fracture performance of double-layer beam specimens under four-point notched bending beam fatigue loading. Double-layer asphalt concrete beam specimens were loaded in a displacement control mode until full-depth cracking was observed. Haversine displacements with zero and maximum deflection peaks were applied to the specimens at frequencies of 5 and 10 Hz. The digital image correlation technique was used to determine and compare the damage mechanisms with stiffness curves plotted by using load and displacement data. A comparison of the results from beams with different interlayer systems showed that the type of interlayer system can noticeably affect the damage mechanisms and the performance of the fatigue specimen. In general, grid systems performed better when the interface bond was stronger. In nongrid interlayers, while interfacial damage created a discontinuity that increased the risk of interfacial debonding, a more flexible interlayer dissipated more energy at the interface and delayed the full vertical cracking of the beams under four-point bending beam fatigue loading.]]></description><pubDate>Thu, 29 Dec 2016 15:53:11 GMT</pubDate><guid>http://pubsindex.trb.org/view/1439450</guid></item><item><title>Laboratory Crack Testing of Interlayer Reinforced Asphalt Samples Using Overlay Tester</title><link>http://pubsindex.trb.org/view/1339381</link><description><![CDATA[Reflective cracking is one of the most undesirable distresses occurring in hot-mix asphalt (HMA) overlays; costing highway agencies millions of Tax Payer dollars in maintenance and rehabilitation programs. To mitigate this distress, crack-impeding interlayer materials such as asphalt interlayers are specified to protect the HMA Overlays as part of maintenance and rehabilitation strategies. Currently however, there is no universally standardized laboratory crack test method to aid in the selection of the most appropriate asphalt interlayer material for maximum crack resistance and performance. This study was undertaken to evaluate the laboratory cracking-resistance and fracture performance of different asphalt interlayer materials embedded in HMA samples. The test method used the Overlay Tester (OT), in a monotonic tensile loading mode (0.135 in./min) at zero degrees Celsius. Eight different asphalt interlayer products with different properties were compared to a ‘control specimen’ using a dense-graded HMA mix. Although field validation is still warranted, the study results indicated a substantial improvement in the crack and fracture performance of the asphalt interlayer reinforced samples over the control samples. A fracture performance improvement of over 40% was measured for some asphalt interlayers, suggesting that use of these asphalt interlayers may be beneficial in mitigating reflective cracking in HMA overlays. For the test conditions and loading parameters considered, the OT test in monotonic tensile-loading mode also exhibited potential as a practical crack test method for determining the cracking-resistance performance of asphalt interlayer materials. The sample crack failure mode, test repeatability, and statistical variability in the test data were generally within reasonable expectations.]]></description><pubDate>Mon, 09 Feb 2015 16:31:44 GMT</pubDate><guid>http://pubsindex.trb.org/view/1339381</guid></item><item><title>Investigating Reflective Cracking Mechanisms in Grid-Reinforced Asphalt Specimens: Use of Four-Point Bending Notched Beam Fatigue Tests and Digital Image Correlation</title><link>http://pubsindex.trb.org/view/1337850</link><description><![CDATA[The main purpose of this research was to examine the effects of interfacial conditions on the reflective cracking-related failure mechanisms of fiberglass grid-reinforced asphalt concrete beams using four-point bending notched beam fatigue tests (NBFTs). This study also aimed to determine whether conventional stiffness-based failure criteria could be used to rank the performance of grid-reinforced beam specimens. For these objectives to be fulfilled, asphalt concrete interfaces were reinforced with two types of fiberglass grid, G12.5 and G25, with and without a tack coat. The tack coats used in this study were PG 64-22 asphalt binder, SS-1 emulsion, and a highly polymer-modified tack coat. Also, two types of mixtures, with 9.5-mm and 12.5-mm nominal maximum aggregate sizes, were included in the testing plan. The beam fatigue tests were conducted at 20°C, and digital image correlation was used to measure the displacements and strains. The results suggest that different interlayer conditions do not reflect a unique failure mechanism, and, therefore, traditional stiffness-based failure criteria can be misleading. Thus all mechanisms, including damage within the asphalt layers and along the interface, that result in weakening the structural integrity of the layered samples must be considered when the performance of reinforced beams under NBFT loading is evaluated. The results indicate that grid-reinforced specimens outperform nonreinforced specimens and that the presence of a high-quality tack coat extends the fatigue life of grid-reinforced specimens.]]></description><pubDate>Wed, 21 Jan 2015 11:29:58 GMT</pubDate><guid>http://pubsindex.trb.org/view/1337850</guid></item><item><title>Matting Solutions for Low-Volume Roads</title><link>http://pubsindex.trb.org/view/1107624</link><description><![CDATA[An evaluation of 11 commercial roadway matting systems was conducted to determine their effectiveness in carrying heavy vehicle traffic over loose-sand subgrades. Three of the 11 matting systems were also evaluated under the same loading conditions over soft, fine-grained subgrades. Matting product types included high-density polyethylene, aluminum, fiberglass, and polyester. System installation methods included continuous rolls of material, segmented rolls, and connection of individual panels. The matting products were assembled in test sections of various sizes, which depended on individual panel dimensions and product availability. The mats were trafficked with a 7-ton, six-wheeled U.S. Marine Corps transport truck loaded with a 7-ton payload until 20% of the mat section was no longer reusable or 2,000 truck passes were achieved. Earth pressure cells were installed under nine of the sand test sections to monitor load distributions provided by the matting systems. On the basis of the test results, recommendations are given for selecting the best roadway matting system types for use on low-volume roads with sand or soft, fine-grained subgrades.]]></description><pubDate>Wed, 27 Jul 2011 13:43:41 GMT</pubDate><guid>http://pubsindex.trb.org/view/1107624</guid></item><item><title>Development of a New Design Methodology for Structural Airfield Mats</title><link>http://pubsindex.trb.org/view/881493</link><description><![CDATA[The U.S. Army Engineer Research and Development Center (ERDC) is currently evaluating the performance of aluminum, fiberglass, plastic, and composite airfield mats under both F-15 and C-17 aircraft loads.  Historically, the design methodology to determine the number of aircraft passes that a particular airfield mat will sustain before failure has been empirically correlated to the subgrade California Bearing Ratio (CBR) and the equivalent single-wheel load.  A new mechanistic design approach was developed in which the performance of the airfield mat is related to the maximum deviatory stress being applied to the subgrade.  New design criteria relating this deviatory stress to the number of passes for aircraft wheel loads were also developed.  A new mat response model, as well as comparisons to experimental measurements collected from full-scale traffic test sections conducted at the ERDC, is presented in this paper to show the applicability of the new design procedure.]]></description><pubDate>Mon, 16 Mar 2009 07:22:46 GMT</pubDate><guid>http://pubsindex.trb.org/view/881493</guid></item><item><title>Observations, Modeling, and Mitigation Related to Reflective Cracking on Composite Pavements in New York City</title><link>http://pubsindex.trb.org/view/880356</link><description><![CDATA[As part of a 7-year field study, experimental composite pavement sections incorporating several reflective crack control treatments were built and investigated in New York City (NYC). The primary objective of this study was to identify cost-effective materials and methods to minimize reflective cracks in NYC composite pavements. The as-constructed experiment included several reflective crack control strategies such as fabrics, membranes, composites, fiberglass laminates, and saw and seal crack control techniques. These strategies were repeated for 15- and 20-ft joint spacings in the base portland cement concrete (PCC) pavement. Control sections without any treatments were also built for each of the two PCC base joint spacings as baseline references. Evaluations in the form of 10 visual condition surveys, five falling weight deflectometer surveys, forensic coring, and materials testing were conducted over the life of the experiment. Performance was measured in terms of crack initiation, length, and severity as well as load transfer deterioration across the reflective cracks. The saw and seal crack control technique and short joint spacing, in that order, had the most effect on mitigating reflective cracking. The saw and seal technique offers a life extension of at least 18.5% and 34% for the 20- and 15-ft joint spacings, respectively, when compared with the NYC Department of Design and Construction (NYCDDC) standard reflective crack control measure—a nonwoven polypropylene fabric interlayer. On the basis of these findings, it is recommended that NYCDDC switch its standard reflective crack mitigation practice to saw and seal and abolish the practice of skewing transverse joints in the PCC base. A saw and seal specification was developed to help NYCDDC implement this recommendation. Additionally, the data from this research represent a unique body of work that can be used in mechanistic–empirical modeling of this important distress type.]]></description><pubDate>Thu, 29 Jan 2009 09:31:24 GMT</pubDate><guid>http://pubsindex.trb.org/view/880356</guid></item><item><title>Constitutive Design Criteria for a Fiberglass Grid: The Mechanical Performance and Bottom-Up Crack Propagation Retardation Mechanism of a Grid-Reinforced Asphalt Concrete System</title><link>http://pubsindex.trb.org/view/847995</link><description><![CDATA[Asphalt reinforcement is used to extend the service life of pavements while taking into account the increasingly rapid growth in traffic volume. This paper presents constitutive design criteria for a semi-rigid, resin-impregnated fiberglass grid that enhances the mechanical performance of the asphalt concrete overlay and provides a mechanism to retard crack propagation. The structure of the grid is formed by stitching warp and weft strands at their intersections such that the design allows the formation of interlocking columns of the asphalt mix. An acrylic polymer resin covers the fiberglass strands, thus making their viscoelastic nature compatible with the asphalt materials as well as protecting the glass fibers from corrosion in a roadway environment. The remarkable temperature susceptibility of the resin is observed in a high shear modulus profile over an extensive range of material temperatures using time-temperature superposition. The grid tensile strength of 100 kN/m was qualified using standard measurements. Three-point bending and cyclic fatigue loading mechanical tests affirm the retardation performance of the grid-reinforced system in terms of crack propagation. The retardation mechanism is effected by synchronizing the cracking pattern with the flexural stress-strain profile through image analysis. The bottom-up crack propagation at the grid interface exhibits a time delay until the upward fracturing process is resumed at a slower rate. Fracture toughness quantitatively represents the effects of crack retardation. Laboratory fatigue testing results indicate a nearly seven times longer life for the grid-reinforced specimen than that of the non-reinforced one. A National Center for Asphalt Technology (NCAT) full-scale road testing program provides comparative assessments of the grid-reinforced pavements. After trafficking 20 million ESALs, longitudinal and transverse cracks appeared only in the non-reinforced area. A visual inspection of the grid extracted from the reinforced area showed fair condition of the pavement.]]></description><pubDate>Thu, 31 Jul 2008 15:24:23 GMT</pubDate><guid>http://pubsindex.trb.org/view/847995</guid></item><item><title>Fiberglass Nail Pullout Capacity for Rapid Soil Landslide Remediation</title><link>http://pubsindex.trb.org/view/802633</link><description><![CDATA[Soil nailing using launched soil nails are a viable means of rapid and relatively low cost repair of shallow slope failures in soils.  Fiberglass nails are a potential alternative to steel nails to reduce the risk the risk of corrosion, reduce cost, and simplify nail fabrication.  This study considered the pullout capacity of fiberglass versus steel nails, finding the capacity of both nail types was similar to the lower bound capacity of traditionally installed soil nails.  Other factors discussed in the paper include installation damage, deflection required to mobilize the nail strength, and durability in the ground environment.  The results suggest fiberglass nails may be a viable alternative to steel if the cross section of the fiberglass nails is selected so the nails provide similar strength to steel.]]></description><pubDate>Mon, 23 Apr 2007 07:53:54 GMT</pubDate><guid>http://pubsindex.trb.org/view/802633</guid></item><item><title>DEVELOPMENT OF ENERGY-ABSORBING COMPOSITE UTILITY POLE</title><link>http://pubsindex.trb.org/view/683590</link><description><![CDATA[The serious hazard presented by unforgiving timber utility poles installed along the nation's roadways has long been recognized by the roadside safety community.  However, relatively little attention has been devoted to the development of safer utility poles beyond breakaway timber pole designs.  A new generation of utility pole designs that use energy-absorbing composite materials offers a solution to the development and implementation of safer utility poles that have a cost advantage over breakaway timber poles and can be tailored to achieve the desired functional performance and energy absorption characteristics inherently without the need for additional strength members or add-on energy absorption devices.  This research has resulted in the development of an energy-absorbing fiberglass-reinforced composite (FRC) utility pole design that meets structural performance requirements for environmental loading in accordance with the National Electrical Safety Code for Class 4 poles and safety performance criteria in compliance with National Cooperative Highway Research Program (NCHRP) Report 350 Test Level 2 conditions for utility poles.  Developmental testing and analyses were performed to support the development of a prototype design for demonstration testing.  Full-scale crash testing has demonstrated the ability of the composite pole to absorb the vehicle's impact energy by progressive crushing and fracture propagation as the vehicle is brought to a controlled stop.  In addition to offering improved safety performance, the energy-absorbing FRC pole provides significant functional advantages, such as reduced weight, an improved strength-to-weight ratio, increased longevity, ease of installation, low maintenance, and resistance to environmental degradation.]]></description><pubDate>Tue, 09 Dec 2003 00:00:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/683590</guid></item><item><title>GEOCOMPOSITE CAPILLARY BARRIER DRAIN SYSTEM WITH FIBERGLASS TRANSPORT LAYER</title><link>http://pubsindex.trb.org/view/715886</link><description><![CDATA[A geocomposite capillary barrier drain (GCBD) removes water from soil while pore pressures remain negative, that is, the soil to be drained does not need to be saturated.  GCBDs are being evaluated for inclusion in pavement systems, particularly between the base course and subgrade layer.  The GCBD system comprises a capillary barrier layer (a geonet) sandwiched between transport layers (certain geotextiles).  Improved GCBD performance is expected with a transport layer that has a greater affinity for water compared with conventional geotextiles.  After many materials were evaluated, a woven fiberglass product was selected for further evaluation as a transport layer.  A GCBD with a fiberglass transport layer was placed between a subgrade and a base course in a 3-m-long sloped test device used to measure lateral drainage.  Water was infiltrated on the top of the base course, and drainage from the GCBD and the soil layers was collected.  Measurements of soil suction were made within the soil layers.  The GCBD performance was evaluated during three test phases:  constant rate infiltration, subsequent drainage with no infiltration, and transient infiltration corresponding to a design storm.  The GCBD was successful in draining sufficient water under suction to prevent positive pore water pressures from developing in the base course and to limit water movement into the underlying subgrade soil.]]></description><pubDate>Fri, 25 Jan 2002 00:00:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/715886</guid></item><item><title>SELECTION OF NOISE BARRIER MATERIAL</title><link>http://pubsindex.trb.org/view/695871</link><description><![CDATA[Because of the large capital expenditures required to construct or replace a noise barrier, it is important for designers to have the information necessary to make rational choices among the materials available.  Designers face difficulties, however, There is a lack of information on both existing materials and designs, and many of the new products being introduced are not typical in highway construction.  As a result, research was conducted to determine the service life of the various noise barrier materials and products currently in use in Illinois and to develop a life-cycle cost model for evaluating alternative materials.  Wood and metal products were estimated to have a 25-year service life; the service life for earth berms, concrete, and fiberglass was estimated to be 50 years.  Results of the life-cycle cost analyses (LCCA) indicated that earth berms were the lowest-cost alternative, and metal barriers with absorptive panels were the most expensive.  The life-cycle costs of the other barrier materials modeled (including wood, concrete, and proprietary materials) were approximately twice the cost of earth berms.  However, although LCCA can provide an additional piece of information in the selection process for noise barrier materials, it should not be used as the sole criterion because of the lack of reliable historical field data on the costs and frequency of maintenance and replacement of barriers.]]></description><pubDate>Tue, 06 Nov 2001 00:00:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/695871</guid></item><item><title>FIBERGLASS TENDONS FOR POSTTENTIONING CONCRETE BRIDGES</title><link>http://pubsindex.trb.org/view/282335</link><description><![CDATA[Glass, if completely oriented in the direction of stress, can withstand forces as well as steel.  Combining this strength with light weight and corrosion resistance in a high-quality prestressing tendon is conceivable.  Bayer AG, a West German chemical concern with worldwide sales close to $20 billion, has developed a technique that yields unidirectionally oriented fiber-reinforced rods.  The product, Polystal, has proven effective in applications where steel-like resistance to stress is required while affording users the advantages of electrical neutrality and corrosion resistance.  Over the past 10 years, Bayer AG and Strabag, a West German civil engineering and construction firm, have jointly developed a fiberglass tendon and anchorage system to be used as posttensioning elements for concrete construction.  Presently, these elements have been incorporated into a bridge outside of Dusseldorf and their performance is being monitored.  In this paper, the development of Polystal as a posttensioning medium and some insight concerning the Ulenbergstrasse Bridge are reviewed.]]></description><pubDate>Tue, 31 May 1988 00:00:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/282335</guid></item><item><title>EXPERIMENTAL STUDY OF BURIED FIBER-REINFORCED PLASTIC PIPE</title><link>http://pubsindex.trb.org/view/283776</link><description><![CDATA[An experimental study of interaction between soil and fiberglass-reinforced plastic pipes was performed in a large laboratory soil box.  Seven pipe specimens of different diameters and stiffnesses were tested at various loads and under various laying conditions.  Sand and clay were the soil backfill.  Five different and independent sets of measurements were taken in each test; vertical and horizontal pressures in the backfill soil, normal and tangential stresses at the pipe-soil interface, radii of curvature of the pipe, vertical and horizontal pipe deflections, and hoop strains at the internal and external perimeters of the pipes.  Measurements were taken during backfilling and when superimposed pressures were applied. Short-term effects of load, soil type and density, split backfill, and installation quality on pipe performance were considered.  The main findings of the study are analyzed and discussed in qualitative terms.]]></description><pubDate>Thu, 31 Mar 1988 00:00:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/283776</guid></item></channel></rss>