<?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%3ATpxvme" 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>Microscopic Observation of Absorption of Asphalt Binder into the Aggregate Pores Using SEM</title><link>http://pubsindex.trb.org/view/2595224</link><description><![CDATA[In this study, an experimental scheme is developed to visualize asphalt binder absorption within aggregate pores using scanning electron microscopy. A suitable sample preparation approach, image magnification levels, and image processing techniques are utilized for the visualization of the aggregate pores (pore structure and binder occupancy) before and after adding asphalt binder. Three types of aggregate—gneiss, quartzite, and sandstone—are used in this study. The results indicate that sandstone exhibits maximum binder absorption, followed by gneiss, and then quartzite. Sandstone also shows the highest pore occupancy, indicating that a higher pore area enables more binder absorption. Further, the study highlights a progressive decrease in the absorption level as one moves from the aggregate boundary toward its interior.]]></description><pubDate>Tue, 09 Sep 2025 08:55:12 GMT</pubDate><guid>http://pubsindex.trb.org/view/2595224</guid></item><item><title>Fractal Characterization of Channel-Lining Concrete Based on U-Net Deep Learning under Freeze–Thaw Cycles</title><link>http://pubsindex.trb.org/view/2483214</link><description><![CDATA[This study aims to examine the degradation patterns of channel-lining concrete in freeze–thaw cycles in north China. Experimental investigations were conducted to analyze the mechanical properties, surface morphology, and microscopic porosity of the concrete. The U-Net model was employed to perform semantic segmentation on scanning electron microscopy (SEM) images which enhance the accuracy and efficiency of the identification of minute pores. First, its apparent and microscopic pore perimeter area was calculated using the Image Pro Plus image analysis software. The apparent and microscopic fractal dimensions were then computed using fractal theory principles. The experimental results indicated a degradation in the mechanical properties and an increase in the fractal dimension as a consequence of freeze–thaw cycles. The integration of concrete’s internal damage evolution characteristics with the apparent fractal dimension allows for a quantitative analysis of concrete’s damage characteristics when subjected to freezing and thawing. The study also enables the prediction of microscopic damage, facilitating the timely assessment of overall damage to the concrete lining of the channel system. Consequently, it will promptly develop an emergency maintenance plan for the concrete of the channel system.]]></description><pubDate>Sat, 28 Dec 2024 16:15:59 GMT</pubDate><guid>http://pubsindex.trb.org/view/2483214</guid></item><item><title>Improvement of Strength and Volume-Change Properties of Expansive Clays with Geopolymer Treatment</title><link>http://pubsindex.trb.org/view/1843900</link><description><![CDATA[Expansive soils are conventionally treated with chemical stabilizers manufactured by energy-intensive processes that significantly contribute to carbon dioxide emissions globally. Geopolymers, which are synthesized from industrial byproducts rich in aluminosilicates, are a viable alternative to conventional treatments, as they are eco-friendly and sustainable. In this study, a metakaolin-based geopolymer was synthesized, and its effects on the strength and volume-change behavior of two native expansive soils from Texas, with a plasticity index over 20 were investigated. This paper elaborates on the geopolymerization process, synthesis of the metakaolin-based geopolymer, specimen preparation, and geopolymer treatment of soils. Comprehensive material testing revealed two clays with a plasticity index over 20. They were each treated with three dosages of the metakaolin-based geopolymer and cured in 100% relative humidity for three different curing periods. The efficiency of geopolymer treatment was determined by testing the control and geopolymer-treated soils for unconfined compressive strength (UCS), one-dimensional swell, and linear shrinkage. Field emission scanning electron microscope (FESEM) imaging was performed on the synthesized geopolymer, as well as on the control and geopolymer-treated soils, to detect microstructural changes caused by geopolymerization. A significant increase in UCS and reduction in swelling and shrinkage were observed for both geopolymer-treated soils, within a curing period of only 7 days. The FESEM imaging provided new insights on the structure of geopolymers and evidence of geopolymer formation in treated soils. In conclusion, the metakaolin-based geopolymer has strong potential as a lower-carbon-footprint alternative to conventional stabilizers for expansive soils.]]></description><pubDate>Sat, 03 Apr 2021 17:40:48 GMT</pubDate><guid>http://pubsindex.trb.org/view/1843900</guid></item><item><title>Xonotlite and Hillebrandite as Model Compounds for Calcium Silicate Hydrate Seeding in Cementitious Materials</title><link>http://pubsindex.trb.org/view/1732461</link><description><![CDATA[The demand for more environmentally friendly cement with no disadvantages in relation to hydration activity has led to the development of various additives to accelerate cement hydration. As calcium silicate hydrate (C-S-H) is the major hydration product of cement and is responsible for its mechanical properties, it plays an outstanding role in the discussion of nanoparticle additives. Nevertheless, the investigation of its mechanism of action is complicated by the similarity of its properties to those of the C-S-H that forms as an initial hydration product. Crystalline C-S-H phases, on the other hand, can be easily distinguished from the original hydration products, which makes them a valuable model compound for studying the mechanisms of nucleation seeding in cementitious materials. In this paper, the effect of crystalline types of C-S-H as nucleation seeds are presented. Xonotlite and hillebrandite were thoroughly characterized using nuclear magnetic resonance, X-ray diffractometry (XRD), scanning electron microscopy (SEM), and infrared spectroscopy (IR) and were then used as an admixture for alite pastes. Low-vacuum SEM images of the hydrated pastes revealed that xonotlite can significantly promote the visible etch pit formation on C3S clinker particles, which was not found to be true for hillebrandite. Whether the phases act as a nucleation site is assumed to be strongly dependent on the mineralogy: hillebrandite appeared to be heavily overgrown, but xonotlite did not show any hydration products on its surfaces after the same hydration time of up to 24?h. The diverse effect of the minerals was confirmed by the accelerating behavior in isothermal heat flow calorimetry and by XRD.]]></description><pubDate>Mon, 31 Aug 2020 15:05:26 GMT</pubDate><guid>http://pubsindex.trb.org/view/1732461</guid></item><item><title>A New Preparation Method and Imaging Parameters of Asphalt Binder Samples for Atomic Force Microscopy</title><link>http://pubsindex.trb.org/view/1572308</link><description><![CDATA[The sample preparation and the image acquisition method of asphalt binders are of importance to atomic force microscopy (AFM) imaging quality, especially for the peak force quantitative nanomechanical (PF-QNM) mode. Based on the heat-cast method, a new hot asphalt pouring method for asphalt binder AFM sample preparation was developed in this study. For different probe types and test parameters, samples of the commercial SK-70# asphalt binder prepared by the proposed technique were subjected to PF-QNM tests. The experimental results obtained proved the feasibility and stability of the proposed sample preparation method. Aluminum-coated probes with a nominal spring constant range from 0.4 to 6 N/m were found to furnish the optimal solution to the construction of topography and nanomechanical property maps. The variation of test parameters has shown that the peak force setpoint and peak force tapping (PFT) gain strongly influenced the microstructure topography and nanomechanical property maps. Using reasonable probe and imaging parameters, good AFM maps could be obtained.]]></description><pubDate>Fri, 01 Mar 2019 15:50:53 GMT</pubDate><guid>http://pubsindex.trb.org/view/1572308</guid></item><item><title>Using AFM to Study the Interaction Between Recycled Asphalt Materials and Virgin Asphalt Binders</title><link>http://pubsindex.trb.org/view/1496076</link><description><![CDATA[This paper summarizes the results of a laboratory testing program that was conducted to examine the blending between recycled asphalt materials (recycled asphalt shingles (RAS) and reclaimed asphalt pavement (RAP) binders and virgin asphalt binders and to evaluate the factors that may affect fatigue cracking resistance of asphalt mixtures prepared using these materials. To this end, atomic force microscopy (AFM) was utilized to characterize the interfacial zone that develops between the tear-off recycled asphalt shingles RAS and a virgin asphalt binder and compare it to that develops between RAP and the same virgin asphalt binder. Several asphalt mixtures were used to evaluate the effect of the incorporation of RAS, RAP, and their combination on fatigue cracking resistance, including a control mixture (with no RAP or RAS), a mixture containing 30% RAP, a mixture containing 5% tear-off RAS, and a mixture containing 20% RAP and 3% tear-off RAS. The resistance of the asphalt mixtures to fatigue cracking was evaluated using the semi-circular bend (SCB) test. The AFM test results indicated that blending occurred between the RAP binder and the virgin binder. A reduction in the adhesive bonding energy was observed in the blending zone due to the presence of RAP. However, the adhesive bonding energy of the blending zone were significantly higher than those in the RAP binder. The AFM imaging and force spectroscopy experiments revealed no blending between tear-off RAS materials and the virgin asphalt binder considered. The SCB test results showed that the use of tear-off RAS in asphalt mixes significantly reduced their resistance to fatigue cracking.]]></description><pubDate>Tue, 27 Feb 2018 09:46:49 GMT</pubDate><guid>http://pubsindex.trb.org/view/1496076</guid></item><item><title>Blending Measurements in Mixtures with Reclaimed Asphalt: Use of Scanning Electron Microscopy with X-Ray Analysis</title><link>http://pubsindex.trb.org/view/1428937</link><description><![CDATA[A major impediment to the widespread use of asphalt concrete with a high content of reclaimed asphalt pavement (RAP) is uncertainty in the degree of blending between the RAP and the fresh binder. Furthering knowledge concerning the blending between RAP and fresh binder has been difficult because of the lack of an experimental method to quantify the degree of blending in asphalt concrete. This study introduces energy dispersive X-ray spectroscopy (EDS) scanning electron microscopy (SEM) as a means to analyze the degree of blending between RAP and fresh materials in asphalt concrete. EDS allows for mapping the distribution and relative proportion of elements in a sample, hence, allowing for the detection of the distribution of elements in an asphalt concrete specimen. Fresh and RAP binders will have a similar elemental composition. Therefore, titanium dioxide in a fine powder form (0.15-mm particles) is blended with the fresh binder as a tracer before the production of asphalt concrete to enable delineation of the RAP and fresh binders using EDS SEM. The efficacy of EDS SEM for quantifying the degree of blending between RAP and fresh binders in asphalt concrete is demonstrated with two high RAP content mixtures.]]></description><pubDate>Mon, 07 Nov 2016 11:07:14 GMT</pubDate><guid>http://pubsindex.trb.org/view/1428937</guid></item><item><title>Stability of Synthetic Calcium Silicate Hydrate Gels in Presence of Alkalis, Aluminum, and Soluble Silica</title><link>http://pubsindex.trb.org/view/918411</link><description><![CDATA[A study is described of the stability (chemical composition and nanostructural change) of a synthetic calcium silicate hydrate gel in the presence of Ca(OH)2, the two main products of portland cement hydration, hours after alkalis, aluminum, and soluble silica were added to the mix. The sol–gel procedure was used to synthesize the gels. Calcium nitrate and sodium silicate solutions were used as the sources of calcium and silicon, respectively. The samples were prepared to a target Ca–Si ratio of 1.9. A 10-M NaOH solution was added to hold the pH at values greater than 13. All processes were conducted in a nitrogen atmosphere. The samples were characterized by using X-ray diffraction, Fourier transform infrared spectroscopy, nuclear magnetic resonance, transmission electron microscopy, and energy dispersive X-ray. The findings showed that addition of a high sodium hydroxide content led to silicate polymerization. The simultaneous addition of alkalis and aluminum induced a rise in the degree of silicate condensation in the gel [Q²(nAl) and possible cross-linking, Q³, via bridging tetrahedral aluminate], along with the formation of a calcium aluminosilicate hydrate similar to strätlingite. Finally, the simultaneous addition of alkalis, aluminum, and soluble silica favored the precipitation of an alkaline aluminosilicate hydrate gel with calcium replacing a high percentage of sodium and a composition clearly different from that of the other components.]]></description><pubDate>Thu, 27 May 2010 15:29:37 GMT</pubDate><guid>http://pubsindex.trb.org/view/918411</guid></item><item><title>Effect of Application Methods on Effectiveness of Titanium Dioxide as Photocatalyst Compound to Concrete Pavement</title><link>http://pubsindex.trb.org/view/909617</link><description><![CDATA[Photocatalytic compounds have the potential of removing harmful air pollutants from urban areas.  One proposed method to expand the reach of this technology is to apply titanium dioxide to concrete pavement surface to result in air-purifying concrete pavement.  However, the proper method of applying titanium dioxide to the concrete surface is still unclear.  To this end, the objective of this study was to evaluate three methods of application for titanium dioxide to concrete pavement.  Prepared samples were subjected to weathering and abrasion by using an accelerated loading test and rotary abrasion.  The environmental efficiency of the original and weathered samples to remove nitrogen oxides from the atmosphere was measured using a newly developed laboratory setup.  Microscopic analysis was conducted using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to determine the relative concentration and distribution of titanium dioxide particles on the surface before and after weathering.  Results of the experimental program showed that in the original state, the coating with 5% TiO2 and the PT product were the most efficient in removing nitrogen oxide from the air stream.  On the other hand, results of the rotary abrasion test indicated that the use of a thin coating would be more susceptible to abrasion than the photocatalysis compounds applied using the sprinkling method or using the PT product.  The highest NOx removal efficiency in the rotary abrasion state was measured for the coating with 5% TiO2.  Results of SEM and EDS analysis showed that the samples treated with the PT product had a more uniform distribution and a higher concentration of TiO2 than the samples treated with the sprinkling method.  This may explain the greater NO removal efficiency observed in the samples treated with PT product.]]></description><pubDate>Tue, 20 Apr 2010 08:44:26 GMT</pubDate><guid>http://pubsindex.trb.org/view/909617</guid></item><item><title>SCANNING ELECTRON MICROSCOPY AND OTHER TECHNIQUES TO INVESTIGATE LOW-STRENGTH CONCRETE</title><link>http://pubsindex.trb.org/view/715925</link><description><![CDATA[Fracture surface scanning electron microscopy (SEM), X-ray microcomputed tomography (X-ray CT), microhardness testing, contact angle goniometry, and foam drainage testing were used to investigate the cause of low compressive strength concrete in South Dakota.  SEM indicated that air voids were collecting in the vicinity of aggregate surfaces.  These voids reduced the area over which stress could be transferred from the paste to the aggregate.  Also, SEM showed that paste between the air voids was of poor quality.  X-ray CT corroborated the SEM findings concerning the air void distribution, whereas microhardness testing indicated that the paste in higher-strength samples was three times as hard as the paste in low-strength samples.  Air bubbles may attach to the aggregate surfaces due to the aggregate becoming hydrophobic when air-entraining admixtures were used in the concrete.  Contact angle goniometry confirmed this phenomenon as model aggregate surfaces had contact angles between 10 and 40 deg for all admixtures tested, and model aggregate treated with vinsol resin-based air-entraining agents exhibited significantly lower (by 5 to 20 deg) contact angles.  Finally, examination of three-phase foams produced by mixing cement, air-entraining admixture, and water showed that vinsol resin-based foams had larger bubble sizes and kept more water within the foam than did nonvinsol resin-based admixtures.]]></description><pubDate>Thu, 31 Jan 2002 00:00:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/715925</guid></item><item><title>DURABILITY OF COMPOSITE REINFORCEMENT FOR TIMBER BRIDGES</title><link>http://pubsindex.trb.org/view/651232</link><description><![CDATA[Fiber-reinforced polymeric (FRP) composites are materials that are increasing in use in civil engineering applications. Despite the excellent mechanical properties and corrosion resistance offered by these organic matrix materials, their susceptibility to the synergistic effects of stress and environmental weathering hinders their widespread acceptance in civil engineering.  The durability of a specific formulation of wood-compatible, pultruded, E-glass-phenolic composite is characterized.  This composite is unique because its layered structure and void content make it compatible with standard structural wood adhesives.  The durability of this wood-compatible FRP reinforcement cannot be directly determined from published work on the durability of E-glass composites because of its unique design.  A durability test matrix was generated according to specifications and test standards from the International Conference of Building Officials Evaluation Service, Inc., and from the California Department of Transportation.  Physical and mechanical properties that were used as indicators of degradation mechanisms and that applied to the bridge environment included tensile behavior, interlaminar shear strength, void content, and glass-transition temperature. Environmental testing involved exposure to various storage media, such as moisture, saline solutions, and calcium carbonate, followed by mechanical testing.  Other exposure treatments included dry heat, cyclic freeze-thaw, accelerated weathering, and natural weathering.  In addition to the strength-retention determination after environmental conditioning, control and exposed specimens were examined visually with optical and scanning electron microscopy to determine surface changes and their effect on failure and fracture modes.]]></description><pubDate>Wed, 08 Mar 2000 00:00:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/651232</guid></item><item><title>EVALUATING CLAY MICROFABRIC USING SCANNING ELECTRON MICROSCOPY AND DIGITAL INFORMATION PROCESSING</title><link>http://pubsindex.trb.org/view/469436</link><description><![CDATA[Several aspects related to the qualitative and quantitative evaluation of clay microfabric are presented.  A digital image processing technique called "intensity gradient analysis" is used in evaluating clay microfabric from scanning electron micrographs.  Details are given of three computer programs (histogram.c, average.c and ellipse.c) that provide for the quantitative analysis of the orientation of clay particles.  The important aspects related to sample and surface preparation and digital image acquisition and analysis are explained.  Two natural clays, Pennsylvanian fire clay and Pleistocene varved glacial lake clay, considered in the analysis show well-defined preferred and random fabric.  The polar histograms of the intensity gradient analysis for the two clays are compared at varying magnifications, and conclusions were drawn.  The output data were conveniently reduced to a few parameters that indicate the strength and magnitude of a given orientation.  The concept of fabric index is used to quantitatively describe the preferential or randomness of clay microfabric.  A simple scheme is proposed by which clay microfabric is classified as preferred when the fabric index is less than a value of 0.75 and random otherwise.  The advantages of the signal intensity gradient method are that it is based on intensity changes rather than absolute values, the rosette diagrams of several micrographs can simply be added to get an overall idea, and it provides a common frame of reference for description of microfabric.  The disadvantages are that it requires careful surface preparation, and the technique is valid for linear features.  With the advent of inexpensive and powerful image processing tools, the technique has the potential to become a routine tool for the orientation analysis of clay micrographs seen in scanning electron microscopy.]]></description><pubDate>Sat, 27 Dec 1997 00:00:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/469436</guid></item><item><title>PERMEABILITY OF CONCRETE SUBJECTED TO CYCLIC LOADING</title><link>http://pubsindex.trb.org/view/467946</link><description><![CDATA[The effect of microcracking development and propagation on the permeability of concrete was investigated in this study.  Large numbers of single-edge-notched beams as well as unnotched beams were prepared in the laboratory and in the field from different concrete mixes and subjected to dynamic loading at various stress ratios.  During the cyclic loading, stress-strain and air permeability measurements were simultaneously recorded using strain gauges and the poroscope apparatus.  Obtained strain and the air permeability measurements were used to evaluate the deterioration of concrete during crack initiation and further propagation.  After fatigue testing, other sets of samples were cored from the fractured beams for water permeability testing. Results from these samples were used to correlate with the air permeability as well as with the compressive strength of the beams.  Findings indicated that at the first stage of cyclic loading the beam samples exhibited large strains along with a rapid deterioration in the permeability values.  Scanning electron microscope images on specimens obtained from cracked sections in Stages I and II corresponded with the severity of the strain measurements and the air permeability values in these zones.  It was also found that compressive strength influenced the transport characteristics of concrete.  Another relationship was derived for the air permeability ratio versus the ratio of number of cycles.  This relationship can be used as a tool to predict the remaining fatigue life of a structure by measuring its permeability.]]></description><pubDate>Tue, 22 Oct 1996 00:00:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/467946</guid></item><item><title>A DIFFERENT PERSPECTIVE FOR INVESTIGATION OF PORTLAND CEMENT CONCRETE PAVEMENT DETERIORATION</title><link>http://pubsindex.trb.org/view/467917</link><description><![CDATA[Many early Iowa portland cement concrete (PCC) pavements provided good performance without deterioration for more than 50 years.  In the late 1950s, Iowa was faced with severe PCC pavement deterioration called D-cracking due to crushed limestone containing a bad pore system.  Selective quarrying solved the problem.  In 1990, cracking deterioration was identified on a 3-year-old US-20 pavement in central Iowa.  The coarse aggregate was a crushed limestone with an excellent history of performance in PCC pavement.  Examination of cores showed very few cracks through the coarse aggregate particles. The cracks were predominately confined to the matrix.  A high-resolution, low-vacuum Hitachi scanning electron microscope with an energy dispersion detector was used to investigate the deterioration.  Subsequent evaluation identified a very small concentration of silica gel (silicon) but substantial amounts of sulfur and aluminum (assumed to be ettringite) in the air voids. Some of these voids have cracks radiating from them leading to the conclusion that the ettringite in the voids, after being subjected to sodium chloride brine, initially swelled and then dissolved.  The research has indicated that the premature deterioration may be due to ettringite and may have been mistakenly identified as alkali-silica reactivity.]]></description><pubDate>Fri, 18 Oct 1996 00:00:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/467917</guid></item><item><title>EVALUATING PARTICULATE EMISSIONS FROM JET ENGINES: ANALYSIS OF CHEMICAL AND PHYSICAL CHARACTERISTICS AND POTENTIAL IMPACTS ON COASTAL ENVIRONMENTS AND HUMAN HEALTH</title><link>http://pubsindex.trb.org/view/464037</link><description><![CDATA[The results of this study suggest that the range of size of particulate emissions from some jet engines clusters below 1.5 micrometers and that the emissions contain heavy metals. Therefore, jet exhaust particulates (JEPs) have the potential to adversely affect both the environment and human health.  Little is known about the particulate component of jet engine emissions.  Baseline physical and chemical data on JEPs were obtained to evaluate their potential effects on the environment. Particles collected from the exhaust stream of two types of jet engines were examined using scanning electron microscopy. Analysis indicated that 100% of the particles collected were below 1.5 micrometers in size.  Particles in this size range can penetrate to the alveoli of human lungs.  Chemical analyses of jet engine exhaust were conducted in an attempt to identify chemical fingerprints that would distinguish aviation emissions in the environment from other anthropogenic emissions.  Certain heavy metals, especially vanadium, were found in jet exhaust and may be useful chemical fingerprints.  Analysis of JP-5 fuel standards revealed a suite of alkylbenzene hydrocarbons, which may also aid in fingerprinting aviation emissions.  Sediment samples taken at coastal wetlands near airports indicated the presence of the same heavy metals as those found in jet exhaust samples.  Field sites exposed to higher volumes of air traffic contained higher levels of sediment heavy metals, supporting the hypothesis that aerial deposition of heavy metals is occurring in areas near some airports.]]></description><pubDate>Wed, 18 Sep 1996 00:00:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/464037</guid></item></channel></rss>