<?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%3ARbmdhcbj%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>Experimental Study on Physical and Mechanical Properties of Lightweight Cellular Concrete Specimens Cast in Field and Laboratory</title><link>http://pubsindex.trb.org/view/2350650</link><description><![CDATA[This paper presents a series of laboratory tests for evaluating the material properties of Lightweight cellular concrete (LCC) with different cement-to-fly ash ratios and at different ages. LCC specimens used in this study were cast in the field and/or laboratory. Large and small direct shear box tests were used to determine the shear strengths of LCC specimens. The test results show that the average wet densities for the LCC specimens cast in the laboratory ranged from 460 to 491?kg/m3, whereas the average wet densities for the specimens cast in the field ranged from 480 to 578?kg/m3 at the age of 28 days. The permeability values for the LCC specimens cast in the field ranged from 5.4 × 10-7 to 7.7 × 10-6 m/s and the permeability values for the LCC specimens cast in the laboratory ranged from 6.8 × 10-7 to 2.5 × 10-6 m/s. The measured peak friction angles of the LCC specimens from the small direct shear box tests ranged from 19° to 63°, whereas the measured peak friction angles of the LCC specimens from large direct shear box tests ranged from 23° to 79°. The average measured compressive strengths for the LCC specimens cast in the field and laboratory ranged from 0.43 to 1.15?MPa and 1.08 to 1.11?MPa at the age of 28 days, respectively. LCC specimens showed shrinkage behavior when subjected to wet–dry cycles and had good resistance to freeze–thaw cycles following ASTM D560/560M. The paper also compares the material properties of LCC measured in this study with those reported in the literature and the comparison shows good agreement overall.]]></description><pubDate>Tue, 12 Mar 2024 11:04:43 GMT</pubDate><guid>http://pubsindex.trb.org/view/2350650</guid></item><item><title>Comparative Analysis of Laboratory and Prototype Models of Pervious Concrete Mixes Containing Reclaimed Asphalt Pavement Aggregates</title><link>http://pubsindex.trb.org/view/1905278</link><description><![CDATA[Pervious concrete (PC) is lightweight concrete with higher porosity and permeability than conventional concrete, making it suitable for reducing storm-water runoff from pavements. Incorporating reclaimed asphalt pavement (RAP) aggregates as a replacement for natural aggregates will likely enhance the porosity and permeability of PC pavement mixes. This paper provides a comparative analysis of the influence of RAP in PC pavement mixes when prepared in two different conditions (laboratory and field). To simulate field conditions, a prototype model tank consisting of subgrade and reservoir layers and a PC slab was constructed. Studies showed that the compaction types and efforts affect the RAP-PC prototype slab and require 50% extra cement to achieve the recommended 28-day compressive and flexural strength of PC pavements. The prototype model tank’s surface infiltration (SI) test demonstrated a higher permeability but less density than laboratory-prepared specimens, indicating that the use of binary graded RAP aggregates contributes to a porous network structure, which improves the transport properties of PC pavement mixes. A correlation with a high R2 value between the laboratory and prototype model tank was also established, indicating the coexistence of a relationship between the density and porosity of laboratory and Prototype-PC pavement mixes. Interestingly, it was reported that the use of standard proctor hammer compaction to cast laboratory specimens produced the same effect when the vibratory hammer compacted the RAP-PC prototype for 20?s. It is, therefore, recommended that 25% to 50% of RAP be used as a coarse aggregate replacement to produce PC pavement mixes.]]></description><pubDate>Mon, 24 Jan 2022 17:22:01 GMT</pubDate><guid>http://pubsindex.trb.org/view/1905278</guid></item><item><title>Properties of ultra-low density lightweight cellular concrete containing slag</title><link>http://pubsindex.trb.org/view/1572288</link><description><![CDATA[The suitability of using alternative material in the pavement structure was investigated. The approach considered the use of lightweight cellular concrete incorporating more environmental friendly alternatives. This was accomplished by partial replacement of cement with blast furnace slag. The purpose of this study, was to provide a protection layer over a weak subgrade in a Canadian pavement structure. Three different densities of lightweight cellular concrete were considered. These were: 400, 475, and 600 kg/m³, containing 80% of Portland cement, 20% of slag, water, and pre-foamed foam. Properties investigated included compressive and tensile strength, modulus of elasticity, Poisson’s ratio, and water absorption. It was determined that the material has adequate compressive strength for pavement application for all considered densities. It was also found that it exhibited higher stiffness than typical granular material. Tensile strength ranged from 14% to 18% of its compressive strength for the respective densities. Water absorption also indicated an increase with decrease in density. Failure criteria analysis assessing the structural capacities of the LCC densities found that the LCC layer could allow more than twice the traffic loading than the conventional granular material in terms of fatigue crackings. For rutting, it could allow between eight to thirty four times more traffic. Although the mechanical properties of lightweight cellular concrete reflect that it could be considered as a potential pavement material, it is recommended that further assessment of lightweight cellular concrete in terms of durability and functionality is required.]]></description><pubDate>Fri, 01 Mar 2019 15:50:53 GMT</pubDate><guid>http://pubsindex.trb.org/view/1572288</guid></item><item><title>Durable Concrete Overlays in Two Virginia Bridges</title><link>http://pubsindex.trb.org/view/1496282</link><description><![CDATA[The purpose of this study was to implement innovative concretes with low permeability and reduced cracking potential in overlays to reduce chloride infiltration into the bridge decks. Two parallel bridges on Route 64 over Dunlap Creek in Alleghany County, Virginia, were selected for this study. For low cracking potential, relatively low water contents, shrinkage reducing admixtures, and lightweight aggregates were used. For low permeability, concretes had supplementary cementitious material and relatively low water–cementitious material ratios. In the overlays, five different materials were used: latex-modified concrete with rapid set cement; silica fume concrete alone; and silica fume concrete with shrinkage reducing admixture, lightweight coarse aggregate, and partial lightweight fine aggregate. A compressive strength of 3,000 psi at 3 days was sought. The performance of the overlay concretes was observed after two to three winters. The overlays used in this study achieved the specified strength and low permeability. There were minimal tight cracks except for one section with the latex-modified concrete with rapid set cement in the left lane of the westbound bridge. The extensive cracks in that section were attributed to plastic shrinkage from adverse weather conditions at placement and the fact that a truck had caught fire in that lane. Silica fume concrete overlays with shrinkage reducing admixture, lightweight coarse aggregate, or lightweight fine aggregate are ready for implementation in the field for low cracking overlays.]]></description><pubDate>Mon, 26 Mar 2018 09:18:07 GMT</pubDate><guid>http://pubsindex.trb.org/view/1496282</guid></item><item><title>Research on Expanded Clay Aggregates Breakdown of Lightweight Asphalt Concrete</title><link>http://pubsindex.trb.org/view/1494466</link><description><![CDATA[Effects of aggregates fragmentation on performance of lightweight asphalt concrete are studied in this paper. The Marshall mixture design method was used to determine the optimum asphalt content of lightweight SMA-13 (LSMA-13). Gyratory compaction test was taken to simulate aggregates crushing. British Pendulum Tester, sand patch method, rutting test, indirect tensile strength test, freeze-thaw splitting test and soaked Marshall stability test were adopted to study the effects of aggregates fragmentation on friction, high temperature stability, low temperature crack resistance and moisture susceptibility of LSMA-13, respectively. The results show that lightweight aggregates have little effects on the fragmentation of basalt aggregates whose particle size is larger than that of lightweight aggregates, but can prevent the basalt aggregates whose particle size is smaller than that of lightweight aggregates from breaking. The number of gyrations and the replacement percentage of lightweight aggregates have negative effects on the aggregates fragmentation index (AFI) of LSMA-13. LSMA-13 have good skid resistance and the effects of aggregates fragmentation on friction of lightweight asphalt concrete are not obvious. The larger the AFI value is, the smaller the dynamic stability (DS) is. And when AFI is larger than 6%, DS of LSMA-13 is smaller than DS criteria (3000mm -1). 6% can be used as the AFI criterion of LSMA-13 for pavement engineering. Moreover, the effects of aggregates fragmentation on low temperature crack resistance of LSMA-13 are not obvious. The replacement percentage of lightweight aggregates of LSMA-13 has negative effect on its low temperature crack resistance. And the aggregates fragmentation of LSMA-13 has positive effect on its moisture susceptibility. LSMA-13 are not recommended to be applied in cold regions engineering, but are recommended to be applied in rainy regions engineering.]]></description><pubDate>Thu, 22 Feb 2018 09:16:22 GMT</pubDate><guid>http://pubsindex.trb.org/view/1494466</guid></item><item><title>Variation in the Test Results of Self-Consolidating Lightweight Concrete Containing Ternary Blended Cement</title><link>http://pubsindex.trb.org/view/1494933</link><description><![CDATA[Portland limestone cement can be considered as a suitable alternative for portland cement in self-consolidating lightweight concrete (SCLWC) mixtures. However, certain inconsistencies were reported in terms of strength development and durability properties of the portland limestone cement concrete. In addition, fresh SCLWC mixtures are more likely to encounter test results variation than ordinary concrete. This paper experimentally investigates the performance of SCLWC incorporating ternary blended cements containing portland limestone cement and silica fume, fly ash, natural zeolite or metakaolin. The results show that the pozzolanic materials mixtures have greater but less variable results of flowability compared to the portland limestone mixture. The coefficient of variation in results of slump flow test is varied 0.8-2.9%. It was also observed there is a reduction in variation of the V-funnel results as the mean value increased. The obtained coefficient of variation was as low as 7% for zeolite ternary mixtures and the highest variation belonged to the binary mixture by 19.2%. The result of rapid chloride migration test (RCMT) and electrical resistance test indicated that there is a strong correlation between these two variables. Comparing the results to other studies, we recognized that the correlation seems to be unique for each case study.]]></description><pubDate>Wed, 31 Jan 2018 10:47:08 GMT</pubDate><guid>http://pubsindex.trb.org/view/1494933</guid></item><item><title>Development of a Specification for Low-Cracking Bridge Deck Concrete in Virginia</title><link>http://pubsindex.trb.org/view/1438698</link><description><![CDATA[Cracking continues to be the number one concern about bridge deck construction. Rarely is a deck without cracks constructed. Transverse cracking mainly attributable to drying shrinkage is common in bridge decks and has been observed in many bridge decks newly constructed by the Virginia Department of Transportation (DOT). Shrinkage-reducing admixtures (SRAs) in concrete reduce shrinkage and are one of the most effective ways of reducing shrinkage cracking. A low modulus of elasticity and high creep also help minimize cracking. Lightweight concrete (LWC) has a lower modulus of elasticity, higher inelastic strains, a lower coefficient of thermal expansion, a more continuous contact zone between the aggregate and the paste, and more water in the pores of aggregates for continued internal curing than normal weight concrete: all these factors help reduce cracking in LWC. Drying shrinkage can also be counteracted with the use of shrinkage-compensating concrete (SC). When properly restrained by reinforcement, SC can expand an amount equal to or slightly greater than the anticipated drying shrinkage. The research in this paper investigated the effectiveness of SC, LWC, and concrete with SRA in reducing cracks in bridge decks and to develop a low-cracking bridge deck specification for use in future Virginia DOT bridge decks. The study showed that bridges with fewer and narrower cracks could be constructed with SRA, LWC, and SC and that proper construction practices were needed to reduce bridge deck cracking. This study resulted in the Virginia DOT implementing a low-cracking bridge deck specification.]]></description><pubDate>Mon, 13 Mar 2017 16:05:40 GMT</pubDate><guid>http://pubsindex.trb.org/view/1438698</guid></item><item><title>Lightweight High-Performance Concrete in Beams and Deck in Opal, Virginia</title><link>http://pubsindex.trb.org/view/1338396</link><description><![CDATA[Lightweight high-performance concrete (LWHPC) with a pozzolan (fly ash or silica fume) or slag cement is expected to provide high workability, high strength, and high durability with reduced dead load. High workability is achieved by self-consolidating concrete. High strength and durability is possible through proper selection of ingredients and proportions. In this study, self-consolidating LWHPC with slag cement was used in the prestressed bulb-T beams for the bridge on Route 17 over Routes 15/29 in Fauquier County, Opal, Virginia. The deck has LWHPC with conventional consistency. The LWHPC had high workability, satisfactory strength and permeability in the ad bridge beams. The bridge deck LWHPC with slag cement had satisfactory strength and durability with no cracks after two winters. The study recommends that lightweight HPC with high workability and containing pozzolans or slag cement be considered in beams when there are long spans, poor soil conditions, and congested reinforcement. Further, lightweight concretes with conventional consistency should be considered for reducing deck cracking.]]></description><pubDate>Thu, 26 Feb 2015 10:03:48 GMT</pubDate><guid>http://pubsindex.trb.org/view/1338396</guid></item><item><title>Chloride Infusion and Durability in Lightweight Concrete with Fiber Reinforced Polymer (FRP) Wrapping</title><link>http://pubsindex.trb.org/view/1337970</link><description><![CDATA[The purpose of this study was to investigate the effects of Fiber Reinforced Polymer (FRP) wraps on reducing chloride ingress and durability of lightweight concrete. Several prior studies have dealt with FRP application on normal weight concrete. However, the literature on externally bonded FRP application on lightweight concrete is sparse. This study involved determining any decrease in chloride ingress and associated increased durability in FRP wrapped lightweight concrete. Forty two cylinders were subjected to the electricity induced accelerated testing in a saline solution for 50 days. Samples were removed from the immersion tank after specific failures and analyzed for chloride content and failure modes. Both lightweight and normal weight concrete greatly benefited from FRP wrapping in terms of increased time to failure and reduced concrete chloride. Lightweight concrete generally performed better with Carbon FRP (CFRP), and normal weight concrete with Glass FRP (GFRP). CFRP wraps produced the best overall protection. Multiple wraps were more effective at reducing chloride ingress than single wraps. Lightweight concrete had greater chloride permeability reductions, whereas normal weight concrete benefited more from FRP confinement effects. The majority of sample failures were caused by cracking in the concrete substrate.]]></description><pubDate>Tue, 27 Jan 2015 11:22:51 GMT</pubDate><guid>http://pubsindex.trb.org/view/1337970</guid></item><item><title>High-Performance/High-Strength Lightweight Concrete for Bridge Girders and Decks</title><link>http://pubsindex.trb.org/view/1244385</link><description><![CDATA[This report presents proposed changes to the AASHTO LRFD bridge design and construction specifications to address the use of lightweight concrete in bridge girders and decks.  These modified specifications will provide highway agencies with the information necessary to develop comparable designs of lightweight and normal weight concrete bridge elements for use in evaluating alternatives and selecting the alternative that will yield economic benefits.  The material contained in the report should be of immediate interest to state bridge engineers and others involved in the design and construction of concrete bridges.]]></description><pubDate>Mon, 25 Feb 2013 13:52:50 GMT</pubDate><guid>http://pubsindex.trb.org/view/1244385</guid></item><item><title>Design of the Rich Street Bridge over the Scioto River, Columbus, Ohio</title><link>http://pubsindex.trb.org/view/881479</link><description><![CDATA[The Rich Street Bridge in Columbus, Ohio will replace a deteriorating 1914 earth filled concrete arch with a modern open-rib arch structure.  The bridge is one of three crossing the Scioto River in the city's historic Civic Center.  The configuration of the new structure was selected in response to design criteria set by community representatives requiring that the bridge complement the adjoining bridges to form a "family" of arch bridges while respecting the architectural character of the Civic Center. The proposed bridge is a 5 span, 563 foot long structure supported on four lines of arches.  The arches are constructed integrally with the bridge's four girder lines so that the resulting structure behaves as a rigid frame.  Both the arches and the girders consist of precast concrete segments constructed using high strength lightweight concrete.  Railings, lighting and other architectural details will be modern in style reflecting the design of the Central Ohio Science Institute and other recent buildings in the Civic Center.]]></description><pubDate>Mon, 30 Mar 2009 07:19:23 GMT</pubDate><guid>http://pubsindex.trb.org/view/881479</guid></item><item><title>Improvement of Portable Concrete Barrier Design Using Computational Mechanics</title><link>http://pubsindex.trb.org/view/777091</link><description><![CDATA[Concrete safety barriers have been employed broadly in Italy since the 1980s, particularly on highways and freeways. Safety barrier homologation and design standards have not yet precisely determined specific fields of application or modality of installation, in particular for concrete barriers. Such barriers have sometimes been judged too rigid and, therefore, inadequate to pass crash tests conducted with lightweight vehicles. No changes have been made nor have new designs (cross-section shape and size) been developed in the past 20 years. For all those reasons, the possibility of achieving better overall performance with concrete barriers has been investigated (containment of heavy vehicles and lower accelerations on occupants of lightweight vehicles). One design proposal for these modular systems is to use lightweight concrete and make the element shorter than the one that is usually adopted in Italy. In that way, the higher lateral deformability of the barrier could lead to a greater dissipation of energy, with a resulting decrease in the dynamic effects for users, maintaining a good containment capability in the high-energy crash tests. In this paper, this new design is evaluated with virtual crash tests carried out with LS-DYNA, a finite element code. The model has been previously validated by comparing results of an actual crash test (using the existing Italian concrete barrier design) with the virtual crash test performed under the same conditions.]]></description><pubDate>Fri, 03 Mar 2006 10:47:42 GMT</pubDate><guid>http://pubsindex.trb.org/view/777091</guid></item><item><title>PERSPECTIVES ON FUTURE HIGHWAY BRIDGE DESIGN: CROSSING INTO A NEW AGE</title><link>http://pubsindex.trb.org/view/476620</link><description><![CDATA[Cost savings, life-cycle costs, aesthetics, and material improvements will make segmental concrete the future choice for long span cable-stayed bridges.  The completion of the Sunshine Skyway Bridge in Tampa, Florida, in 1987 demonstrated that a community can have an economical signature bridge reflecting that community's vision, and this trend will continue. Innovative financing will be the primary means of accomplishing large bridge projects in the future.  The 5.87-km Mid-Bay Bridge in West Florida was completed in 1993 as a toll bridge, with $81 million in revenue bonds covering all costs.  There was no federal money involved in the project, and state and county loan money was paid back from the bond issue.  Bridge owners concerned about life-cycle costs will demand manuals showing maintenance inspections and rehabilitation designed to extend the lives of bridges.  High performance concrete and structural lightweight concrete will continue to improve segmental concrete cable-stayed bridges.  Bridge aesthetics and costs are and will continue to be dominant factors.  The need to balance these factors will keep bridge engineering firms looking for new materials as well as improving existing materials.]]></description><pubDate>Tue, 20 Mar 2001 00:00:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/476620</guid></item><item><title>REHABILITATION OF TAPPAN ZEE BRIDGE USING PRECAST CONCRETE COMPOSITE DECK UNITS</title><link>http://pubsindex.trb.org/view/651187</link><description><![CDATA[The criteria used for successful rehabilitation of decks of major bridges when it is not feasible to close the bridge to traffic are described.  These criteria are described with specific reference to recent work on the trestle spans of the Tappan Zee Bridge over the Hudson River near New York City.  The results of an experimental program conducted with a full-scale, 10-m-span, lightweight concrete slab-steel beam composite bridge deck unit intended for later use in rehabilitating the through-truss decks of the bridge are also described.  Loading history included 10,000,000 cycles of flexural fatigue loading followed by a flexural load capacity test.  Measured values of capacity and midspan deflection at this ultimate load level are compared with simplified analytical predictions.  A description of the actual rehabilitation process used on the Tappan Zee Bridge deck is also provided.]]></description><pubDate>Fri, 03 Mar 2000 00:00:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/651187</guid></item><item><title>DESIGN OF SEMILIGHTWEIGHT BRIDGE GIRDERS: DEVELOPMENT-LENGTH CONSIDERATIONS</title><link>http://pubsindex.trb.org/view/651184</link><description><![CDATA[In a recent study, 25 development-length tests were conducted on rectangular and T-shaped semilightweight beams having design compressive strengths of 48 MPa (7,000 psi) and 69 MPa (10,000 psi).  In the rectangular beam tests, the design moment capacity was exceeded in every case.  However, in the tests on T-shaped beams, bond failure occurred in some specimens immediately after the formation of a flexure-shear crack.  Additional tests were then conducted on similar T-shaped beams having varying amounts of transverse reinforcement near the point load.  These tests showed that bond failure could be prevented by increasing the transverse reinforcement near the point of maximum moment.  The study showed that the shift in the tension force that occurs when flexural cracks turn diagonally may lead to bond failure if sufficient anchorage of the strand is not provided.  Therefore, the investigators recommend that the current AASHTO requirements for strand development be enforced at a "critical section" located at a distance d sub p from the point of maximum moment toward the free end of the strand, where d sub p is the distance from the extreme compression fiber to the centroid of the prestressed reinforcement.]]></description><pubDate>Thu, 02 Mar 2000 00:00:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/651184</guid></item></channel></rss>