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    <title>Transport Research International Documentation (TRID)</title>
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    <copyright>Copyright © 2026. 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>
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      <title>Transport Research International Documentation (TRID)</title>
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      <link>https://trid.trb.org/</link>
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    <item>
      <title>Experimental Characterization and Numerical Performance Assessment of Treated Cinder Gravel for Base Course Applications</title>
      <link>https://trid.trb.org/View/2717181</link>
      <description><![CDATA[This study investigated the suitability of natural cinder gravel blended with fine-crushed aggregates as a base course pavement material using laboratory tests and numerical simulations. Laboratory test results for natural cinder gravel indicated that cinder gravel alone failed to meet the Ethiopian Roads Authority (ERA) standard specifications for some tests, and they showed marginal quality values to the standard specifications for GB2 and GB3 base course materials. Thus, mechanical stabilization was performed at different percentages of finely crushed rock (0%, 15%, 20%, 25%, and 30%) by the dry weight of cinder gravel to improve its mechanical and physical properties A blend of 75% cinder gravel with 25% CFA resulted in Los Angeles abrasion (LAA), SG, aggregate crushing value (ACV), aggregate impact value (AIV), plastic index, water absorption, and CBR of 35.7%, 2.7%, 28.1%, 27.98%, nonplastic (NP), 1.16%, and 125%, respectively, fulfilling the required ERA standard specifications of GB2 and GB3 materials. The numerical simulation conducted using PLAXIS 3D demonstrated that the treated cinder gravel base course layer exhibits reduced vertical deformation, higher stiffness response, enhanced ability to dissipate stresses laterally, reducing excessive strain concentrations, and better load-carrying capacity under standard traffic loading. These findings assure the potential use of treated cinder gravel as a sustainable and cost-effective base course material alternative to conventional crushed stone aggregates. Therefore, the use of 75% cinder gravel by weight is recommended for the road base course layer as an alternative material in places where the materials are abundantly available.]]></description>
      <pubDate>Wed, 24 Jun 2026 11:29:35 GMT</pubDate>
      <guid>https://trid.trb.org/View/2717181</guid>
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    <item>
      <title>Experimental and Numerical Investigation of the Shear Behavior of Geogrid-Reinforced Ballast Mixed with Tire Chips</title>
      <link>https://trid.trb.org/View/2551207</link>
      <description><![CDATA[This study presents the results of large-scale laboratory direct shear tests and discrete element method (DEM) simulations conducted on railway ballast mixed with varying proportions of tire chips (TCs) under both unreinforced and geogrid-reinforced conditions. The results of the Los Angeles abrasion test indicated that abrasion resistance of the GB-TC mix enhanced with the increase in TC content. The results of direct shear tests revealed that both friction angle (φ) and dilation angle (ψ) of the GB-TC mix decreased with increase in TC content in both the experiment and DEM simulations. However, with the inclusion of geogrid, the value of φ increased, whereas the value of ψ decreased compared to the unreinforced conditions. Further, it was found that with the increase in TC content, the amount of breakage decreases significantly. Furthermore, the inclusion of geogrids substantially reduces particle breakage in the GB-TC mix as compared to the unreinforced conditions. The peak φ is observed to be lower than that of unreinforced GB when the proportion of TC exceeds 3.3–3.8%, depending on the magnitude of the applied normal stress. Therefore, the optimal TC content to be mixed with geogrid-reinforced GB is suggested to be in the range of 3.3–3.8%.]]></description>
      <pubDate>Mon, 09 Jun 2025 14:49:02 GMT</pubDate>
      <guid>https://trid.trb.org/View/2551207</guid>
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    <item>
      <title>Wear resistance analysis of steel slag aggregates based on morphology characteristics</title>
      <link>https://trid.trb.org/View/2274984</link>
      <description><![CDATA[Steel slag can be utilized in the wearing course of highway asphalt pavement. However, further research is needed to explore the impact of steel slag on the wear resistance of asphalt pavement. This study aimed to evaluate the wear resistance of two steel slag samples and compare them with three stone aggregates based on morphological characteristics. The Los Angeles abrasion test was conducted at different revolution levels, and the micro-morphology characteristics of the aggregates were analyzed through image analysis using six morphology parameters. The results showed that the steel slag samples had the lowest Los Angeles abrasion rates, indicating their superior hardness and wear resistance compared to limestone and granite aggregates. The steel slag aggregates also exhibited higher values in morphological indices of arithmetic mean height Sa, peak apex density Spd, and arithmetic mean curvature of peak apex Spc, indicating a rougher surface, more contact points and more durable wear resistance. Fluctuations were observed on variation curves of the maximum height Sz, surface skewness Ssk, and surface sharpness Sku of the steel slag during the abrasion process, suggesting the presence of numerous pits and spikes that contribute to the skid resistance of the steel slag asphalt mixture. The arithmetic mean height Sa, peak density Spd, and arithmetic mean curvature of peak apex Spc showed a consistent decrease over the number of revolutions, making them reliable indices for future research on the wear resistance of steel slag asphalt mixtures. Overall, this study provides a basis for further research on investigation the correlation between the morphology changes of steel slag aggregates and the anti-skid performance of pavement wearing courses.]]></description>
      <pubDate>Tue, 21 Nov 2023 08:50:15 GMT</pubDate>
      <guid>https://trid.trb.org/View/2274984</guid>
    </item>
    <item>
      <title>Studying the impact of aggregates and mix volumetric properties on the moisture resistance of asphalt concrete using a feed-Forward artificial neural network</title>
      <link>https://trid.trb.org/View/2255842</link>
      <description><![CDATA[Several studies have reported the effect of various additives on the moisture resistance of AC, but limited studies explored the impact of aggregate’s properties on the moisture sensitivity of AC. In this study, the influence of aggregate properties and mix’s volumetric properties on the moisture sensitivity of AC was studied. The moisture sensitivity of the AC was based on Retained Stability Index (RSI). The study utilised results from 319 plant-produced asphalt mixtures. The  was modelled as a function of aggregates and mix’s variables using Artificial Neural Network (ANN). The variables studied include air voids , void in mineral aggregates , clay lump , Los Angeles’s abrasion , soundness value (SV), sand equivalence value , gradation and mix type. Profile method along with weight-connection relative importance ranking were employed to analyse the influence of the input variables on the . The relationship between these variables and the  fits higher order polynomial functions.]]></description>
      <pubDate>Mon, 23 Oct 2023 16:52:52 GMT</pubDate>
      <guid>https://trid.trb.org/View/2255842</guid>
    </item>
    <item>
      <title>Ballast degradation: Effect of particle size and shape using Los Angeles Abrasion test and image analysis</title>
      <link>https://trid.trb.org/View/2064726</link>
      <description><![CDATA[Ballast track is the most widely used track for the railway transport, and ballast bed plays a significant role to provide resistances during train operation. Generally, the ballast bed consists of crushed stones. To achieve the mitigation of ballast degradation, the first priority is to describe the degradation development and to study its effect factors.The influence of ballast morphology (particle size and shape) on ballast degradation is examined here using the Los Angeles Abrasion (LAA) test in combination with 3-D image analysis. LAA tests are used to obtain the deteriorated ballast. Then, based on the 3-D images, the changes of ballast particles after the tests were analysed. To quantify the ballast degradation (abrasion and breakage), the Abrasion Depth based on the analysis of 3-D images were proposed, while ballast breakage was estimated using the broken particles ratio.The results have shown that ballast degradation is directly related to the ballast morphology. The proposed image-based procedure can effectively be applied to assess ballast degradation. The results can be used for ballast material standardization, modelling of ballast degradation process and maintenance cycle prediction.]]></description>
      <pubDate>Tue, 24 Jan 2023 09:31:41 GMT</pubDate>
      <guid>https://trid.trb.org/View/2064726</guid>
    </item>
    <item>
      <title>Evaluation of High Los Angeles Abrasion Loss Aggregate in Stone Matrix Asphalt</title>
      <link>https://trid.trb.org/View/1929462</link>
      <description><![CDATA[Stone matrix asphalt (SMA) was developed in Germany over 40 years ago to resist rutting from studded tire wear. In recent years, there has been increased interest in SMA in the U.S.A. The foundation of SMA mixes is a coarse aggregate stone skeleton that forms a load-bearing matrix. Typical requirements of aggregate are between 30% and 40% loss measured by Los Angeles abrasion test. South Carolina’s granitic aggregate sources are mostly between 45% and 60% loss. In this study, sources with 44%, 53%, and 56% loss were evaluated for pavement rutting, moisture susceptibility, draindown, and cracking potential. The original plan started with designs using 12.5?mm nominal maximum aggregate size (NMAS) to increase macrotexture, from a safety standpoint, but eventually changed to 9.5?mm NMAS to be more consistent with typical coarse aggregate stockpile gradations in South Carolina. The designs were tested with and without fiber. The fiber designs met draindown requirements while the fiberless ones failed at elevated temperatures. The designs met the rut susceptibility criteria and the data indicated that moisture damage did not compromise the designs. The cracking test index (CTindex), a measure of cracking potential, showed good resistance for all of the designs with the exception of the 9.5?mm NMAS with fiber, which had poor results even when compared with high RAP (reclaimed asphalt pavement) dense-graded mixtures. The macrotexture for the 12.5?mm NMAS designs was comparable with other South Carolina open-graded friction course mixtures. Overall, the sources with 44% and 53% loss by Los Angeles abrasion test performed equivocally, with the 9.5?mm fiber design having lower cracking resistance.]]></description>
      <pubDate>Mon, 21 Mar 2022 17:50:50 GMT</pubDate>
      <guid>https://trid.trb.org/View/1929462</guid>
    </item>
    <item>
      <title>Analysis of influence of ballast shape on abrasion resistance using discrete element method</title>
      <link>https://trid.trb.org/View/1757517</link>
      <description><![CDATA[The ballast resistance performance—an important indicator of the performance and maintenance of railway ballast—is strongly dependent on the ballast shape, but this relationship is not yet fully understood. Despite many attempts to model the constitutive behavior of the ballast under cyclic loading using the discrete element method (DEM), few studies have obtained any conclusive results on the ballast breakage behavior. Therefore, in this study, a series of innovative techniques have been adopted to develop a crushable-ballast DEM model, and this model is further calibrated using the results of the Los Angeles abrasion (LAA) test. The results indicate both needle-shaped and flake-shaped ballast samples tend to break more easily than the normal-shaped samples. Thus, only the normal-shaped ballast samples are recommended for LAA test. Furthermore, by considering the ballast dynamic stability, a strict restriction on the proportion of needle-shaped ballast (≤10%) was recommended as the relevant technical standard.]]></description>
      <pubDate>Fri, 29 Oct 2021 15:40:11 GMT</pubDate>
      <guid>https://trid.trb.org/View/1757517</guid>
    </item>
    <item>
      <title>Mechanical and durability assessment of unconfined recycled concrete aggregates and natural aggregates used in road constructions</title>
      <link>https://trid.trb.org/View/1880732</link>
      <description><![CDATA[In the past few decades, recycling crushed concrete pieces and producing recycled concrete aggregate (RCA) has emerged as an effective way for controlling and managing construction and demolition wastes. Among all construction applications of RCA, its consumption in road facilities has increased significantly over the last few years. In this paper, the feasibility of utilising RCAs as an unconfined aggregate in road structure courses was evaluated. For this purpose, six types of natural aggregates (NAs) and three types of RCAs were selected. Then, various physical, mechanical, and durability tests including water absorption, specific weight, proctor test, impact test, crushing test, Los Angles abrasion test, California bearing ratio (CBR) test, sulfate soundness test and different frost soundness tests such as CSA A23.2-24A and AASHTO T103 were conducted on the specimens. The results indicated that all RCAs were acceptable for general applications in road construction. Although the sulfate soundness test suggested that RCAs were durable, they failed in both frost soundness tests. CSA frost soundness tests had the best correlation with the physical and mechanical properties of the aggregates compared to the other durability tests. Also, the AASHTO test method with its defined time-temperature cycles was not satisfactorily applicable to RCAs.]]></description>
      <pubDate>Mon, 11 Oct 2021 19:44:55 GMT</pubDate>
      <guid>https://trid.trb.org/View/1880732</guid>
    </item>
    <item>
      <title>Evaluation of Optimized Compaction Energy for Coarse Aggregates by Gyratory Compactor</title>
      <link>https://trid.trb.org/View/1850823</link>
      <description><![CDATA[Aggregate durability is crucially important for performance of granular roadways. Therefore, proper laboratory durability evaluations of aggregates that will be used during construction and maintenance of granular roadways are very critical. Los-Angeles (LA) abrasion and Micro-Deval tests were two conventional methods that are used for laboratory during tests. However, it is very well known that these tests are not adequate to simulate the durability of aggregates under vehicle and compactor loads. The current study proposes to use the gyratory compaction method to evaluate the durability of aggregate materials. During gyratory tests, gradations, shear resistances, void ratios, and maximum dry unit weights of each material were monitored before and after tests. The results of this study showed that the fines content of the materials did not change significantly, while the gravel and sand contents of all materials changed considerably. It was also observed that the energy required to gain the optimum void ratio and dry unit weight were always higher than those required for the modified and standard Proctor tests energy levels. However, two out of three materials achieved 90% of the maximum shear strength at lower energy levels that were required for the modified Proctor test.]]></description>
      <pubDate>Wed, 30 Jun 2021 11:59:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/1850823</guid>
    </item>
    <item>
      <title>Effects of Crumb Rubber Size and Percentage on Degradation Reduction of Railway Ballast</title>
      <link>https://trid.trb.org/View/1598034</link>
      <description><![CDATA[Higher speed, more freight and frequent maintenance increase ballast degradation and reduce the ballast lifespan. To reduce ballast degradation, crumb rubber used as buffering aggregates in ballast bed is relatively unexplored and needs more studies, because using it has the advantage of reusing the waster rubber and absorbing the noises. The effects of crumb rubber (CR) size and percentage on ballast degradation reduction is studied in this paper, and the optimal CR size and percentage are proposed. Three CR size ranges are utilised, i.e., 3 ∼ 5 mm, 10 ∼ 15 mm and 20 ∼ 25 mm, and the percentages are 0, 10, 20 and 30% by weight. Three kinds of ballast material with two size ranges are utilised. The deteriorated ballast particles were generated using Los Angeles Abrasion (LAA) tests, and the ballast degradation was evaluated with the 3D image analysis. The results indicate that ballast abrasion can be alleviated by adding the CR, while the CR has few influences on the ballast breakage. When CR size is close to ballast particle size, the effects of degradation reduction are not obvious. The corner and edge loss are the main types of ballast abrasion, although different ballast materials significantly influence the abrasion type and degree. Most importantly, the image analysis method is proved to have the ability to present ballast degradation process and has great potential for further degradation-related studies.]]></description>
      <pubDate>Thu, 23 May 2019 10:24:37 GMT</pubDate>
      <guid>https://trid.trb.org/View/1598034</guid>
    </item>
    <item>
      <title>Investigation of Aggregate LA Abrasion on Laboratory Performance of Open Graded Friction Course (OGFC) Mixtures</title>
      <link>https://trid.trb.org/View/1497206</link>
      <description><![CDATA[Open graded friction course (OGFC) and porous friction course (PFC) wearing surfaces are used by many transportation agencies in the US and around the world primarily to improve safety in wet weather. However, durability (i.e., raveling) of these mixtures has been an issue and a topic of study. The primary objective of this study was to study the influence of the LA abrasion value of the aggregate on the performance (raveling resistance and porosity) of the OGFC mixture in lab. This study evaluated OGFC mixtures made with 11 different aggregate sources having LA abrasion values ranging from 20 to 54. The results indicated that higher LA aggregate yielded more resistance to raveling. However, further study and analysis indicated that the aggregate particles fractured during mixing and compaction and the degree of aggregate breakdown was quantified by calculating the uniformity coefficient (Cᵤ) of compacted and uncompacted OGFC mix specimens. Aggregate breakdown resulted in the gradation changing to a finer, more well-graded aggregate distribution (higher Cᵤ) with a higher packing density, thus reducing the porosity, which increased performance in the Cantabro abrasion test. The results also indicated that compaction effort of 50 gyrations of the Superpave Gyratory Compactor resulted in breakdown that increased the Cᵤ by a factor of approximately 1.5 compared to the Cᵤ after mixing alone in the laboratory bucket mixer.]]></description>
      <pubDate>Tue, 27 Mar 2018 11:15:19 GMT</pubDate>
      <guid>https://trid.trb.org/View/1497206</guid>
    </item>
    <item>
      <title>Effect of Flat and Elongated Aggregate on Stone Matrix Asphalt Performance</title>
      <link>https://trid.trb.org/View/1465434</link>
      <description><![CDATA[The importance of this study is driven by asphalt mixture economics since the in‐place cost of stone matrix asphalt (SMA) mixtures is up to 80% higher than conventional dense‐graded mixes. The production of SMA aggregate alone is believed to cost approximately twice that of conventional aggregate production. Therefore, it is essential to determine whether the need for such high quality aggregate products is necessary for satisfactory SMA performance. European specifications were adopted in AASHTO M325 and typically require SMA aggregates to have no more than 30 percent Los Angeles abrasion loss and no more than 20 percent flat and elongated (F&E) particles when measured at a 3:1 ratio of length to maximum thickness. However, these strict aggregate requirements were developed for use in Europe, where studded tires are used for winter travel, and may not be necessary for other countries. The objective of this study was to evaluate the performance of SMA mixes designed with different percentages of F&E aggregate to determine how critical this aggregate property is. Quarries that produce both SMA and non‐SMA stone and two quarries that do not produce SMA stone (due to high F&E values) were evaluated. The study concludes that there is generally no significant adverse effect on performance from using high F&E aggregate if that aggregate has low abrasion loss values. A recommendation is made to use the same F&E requirements for SMA mixes as is used for Superpave mixes.]]></description>
      <pubDate>Mon, 22 May 2017 17:06:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/1465434</guid>
    </item>
    <item>
      <title>Relationship Between Lifespan and Mechanical Performance of Railway Ballast Aggregate</title>
      <link>https://trid.trb.org/View/1465341</link>
      <description><![CDATA[As lifespan is the main criterion for the selection of aggregate for ballast and for planning the maintenance of railroad, it is important to define the relationship between the particle load resistant characteristics and the ballast‘s lifetime in structure. Assessment of the quality of the ballast particles under dynamic and static loading should reflect both the toughness and hardness, and these can be identified with the values of Los Angeles Abrasion and microDeval Abrasion. In order to predict the amount of loads, expressed in cumulated tonnes, the model formerly developed by Canadian Pacific Railroads was adapted. A number of different aggregate mixtures were tested in the laboratory including dolomite and granite rocks. The results were used to assess the gross tonnage possible to transport during the lifetime of ballast until repair or reconstruction should be done. The outcome of this study is the possibility to classify the requirements for aggregates‘ Los Angeles abrasion and micro-Deval abrasion values attributing them to designed traffic volumes.]]></description>
      <pubDate>Fri, 28 Apr 2017 16:50:38 GMT</pubDate>
      <guid>https://trid.trb.org/View/1465341</guid>
    </item>
    <item>
      <title>Effect of Flat and Elongated Aggregate on SMA Performance</title>
      <link>https://trid.trb.org/View/1438961</link>
      <description><![CDATA[The importance of this study is driven by asphalt mixture economics since the cost of Stone Matrix Asphalt (SMA) mixtures in-place is as much as 80% higher than conventional dense-graded mixes. The production of SMA aggregate alone is believed to cost approximately twice that of conventional aggregate production. Therefore, it is essential to determine whether the need for such high quality aggregate products are necessary for satisfactory SMA performance. European specifications were adopted in AASHTO M325 and typically require SMA aggregates to have no more than 30 percent Los Angeles abrasion loss and no more than 20 percent flat and elongated (F & E) particles when measured at a 3:1 ratio of length to maximum thickness. However, these strict aggregate requirements were developed for use in Europe where the use of studded tires for winter travel is an issue, and may not be necessary for other countries. The objective of this study is to evaluate the performance of SMA mixes designed with different percentages of flat and elongated aggregate to determine how critical this aggregate property is. Quarries that produce both SMA and non-SMA stone and two quarries that do not produce SMA stone (due to high F & E values) were evaluated. The study concludes that there is generally no significant adverse effect on performance of using high F & E aggregate if that aggregate has low abrasion loss values.]]></description>
      <pubDate>Mon, 13 Mar 2017 16:05:39 GMT</pubDate>
      <guid>https://trid.trb.org/View/1438961</guid>
    </item>
    <item>
      <title>Real Time Laser Scanning of Aggregate Materials in Highway Construction</title>
      <link>https://trid.trb.org/View/1440694</link>
      <description><![CDATA[The quality and service life of the roadways that make up the highway transportation infrastructure are dependent upon the selection and use of high quality aggregate materials. Five state transportation agencies participated in this Transportation Pooled Fund (TPF) study, which was designed to demonstrate the use of laser scanning as a means to assess, in real-time, the quality of aggregate used in highway construction. Participating states included Kansas, New York, Ohio, Oklahoma, and Pennsylvania. The referenced technology is based on a process referred to as Laser Induced Breakdown Spectroscopy (LIBS). In this process, a high-powered laser pulse is used to excite atoms that make up the aggregate. This excitation results in the emission of light from a range of unique wavelengths (spectrum) that can be thought of as a “fingerprint” of the material. The development of a database of spectra or fingerprints of many aggregate materials with known engineering properties provides the basis for employing numerical techniques (models), similar to “fingerprint matching,” to identify the properties of unknown aggregate material. Scanning data generated in this demonstration show that the technology can differentiate between approved and unapproved aggregate sources. It has the potential to quantify specific test parameters such as acid insoluble residue (AIR), Micro-Deval loss, and specific gravity, as well as to identify the presence of deleterious materials, such as reactive chert, ASR and ACR, and D-cracking susceptible aggregate. It can be used to identify the aggregate source or sources of a stockpile of unknown material(s). A total of 113 aggregates supplied by the participating states were laser-scanned using a field prototype system located in a field materials testing laboratory in South Bethlehem, New York. The analyses in this demonstration focused on specific gravity (bulk and SSD) and absorption, D-cracking, acid insoluble residue, Micro-Deval, and Los Angeles (LA) Abrasion Loss. The results show that laser scanning can successfully predict the properties of aggregate, opening up a whole new way of analyzing aggregate materials. Based on the results presented, recommended future work is outlined, some of which has been initiated and presented herein to refine the scanning and modeling process to enhance data quality.]]></description>
      <pubDate>Mon, 09 Jan 2017 17:16:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/1440694</guid>
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