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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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      <title>Effect of the sand relative density on the tunneling-induced ground settlement in three-dimensional space</title>
      <link>https://trid.trb.org/View/2594363</link>
      <description><![CDATA[Relative density (Dr) is a critical factor that determines the physical and mechanical properties of cohesionless soil. The existing literature investigated its effect on the transverse ground settlement trough induced by tunnel excavation, but a comprehensive understanding about its effect in three-dimensional space has not been provided. In this work, a series of shield excavation model tests was carried out in sandy ground. Two filling methods were used to control the relative density of the sand in the strongbox, and a scaled shield machine whose cutterhead can advance and rotate was employed to simulate the shield construction procedure. The results show that when Dr = 35 %, ground surface settlement is produced before the cutterhead reaches the monitoring section, whereas when Dr = 55 % or 80 %, settlement does not appear until the cutterhead has already passed. As Dr increases, the surface settlement trough in the transverse section becomes shallower and narrower, with its shape evolving from a normal distribution curve to a triangle. The ground volume loss increases with decreasing depth when Dr = 35 %, indicating contraction of the sand above the tunnel. In contrast, dense sand experiences shear dilation, which restricts the spread of volume loss away from the tunnel excavation section. Additionally, the soil arching effect is introduced to explain the hysteresis observed in the surface settlement relative to the position of the cutterhead. According to the test results, different measures should be taken for tunnel construction in the ground with different compactness degree.]]></description>
      <pubDate>Thu, 16 Oct 2025 17:02:34 GMT</pubDate>
      <guid>https://trid.trb.org/View/2594363</guid>
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    <item>
      <title>A Study of Air Voids and Effective Air Voids in Hot Mix Asphalt</title>
      <link>https://trid.trb.org/View/2600579</link>
      <description><![CDATA[The concept of air voids (AV) continues to be used as the primary control parameter in the mix design of hot mix asphalt (HMA). AV are estimated from the bulk specific gravity and the maximum specific gravity. Their accurate estimation is very important, since samples for various tests are compacted to target AV, which are calculated on their basis. This study explored the impact of gradation and asphalt content on the AV, effective air voids (EAV), and apparent and maximum specific gravity of a fine- and a coarse-graded HMA. Samples were tested for bulk specific gravities, apparent and maximum specific gravities, rutting tolerance index, and cracking tolerance index. The results indicate that significant differences exist between AV measured by the different procedures and EAV, and that the differences are greater for a coarse-graded mix than for a fine-graded mix. Major sample-to-sample variations exist for the apparent specific gravity values, which could be significantly different from the generic maximum specific gravity values that are used for each mix. This has a significant impact on the estimation of AV and variability of test results. A strong correlation between the ratio of EAV and AV is presented. Based on the results of this study, and because EAV are strongly correlated to permeability and aging, it is recommended that the concept of EAV be considered in the regular mix design of coarse-graded HMA.]]></description>
      <pubDate>Thu, 18 Sep 2025 15:11:57 GMT</pubDate>
      <guid>https://trid.trb.org/View/2600579</guid>
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    <item>
      <title>Development of Precision Estimates for AASHTO T 84 Using Fine Aggregate</title>
      <link>https://trid.trb.org/View/2562006</link>
      <description><![CDATA[The California Department of Transportation (Caltrans) has established rigorous specifications and test methods to ensure that aggregates used in pavement construction meet the required standards. One of the tests required by Caltrans at Job Mix Formula (JMF), JMF verification, Production Start-Up Evaluation (PSUE), and renewal during road construction is AASHTO T 84, Standard Method of Test for Specific Gravity, and Absorption of Fine Aggregate. This test is an important element for the determination of volumetric properties of hot mix asphalt (HMA). AASHTO T 84 is a standard test method used to determine fine aggregate’s specific gravity and absorption. An interlaboratory study (ILS) was conducted by Caltrans in 2022 in conjunction with the Reference Sample Program (RSP) to determine the variability of AASHTO T 84 for California aggregates. Eighty-three Caltrans-accredited laboratories participated in this study. Two replicate samples for each participating laboratory were used. This study was conducted to provide an estimate of precision for the AASHTO T 84 test procedure in all three specific gravity conditions [i.e., bulk (dry), bulk (SSD—saturated surface-dry), and apparent] and absorption. In the test method, the mass of a fine aggregate sample is determined in three separate conditions: Oven-dry, SSD, and submerged in water. These three masses are then used to calculate bulk (dry) specific gravity, bulk (SSD) specific gravity, apparent specific gravity, and absorption. Data from the participating laboratories were evaluated in accordance with ASTM C802 and ASTM C670. This study showed that the allowable difference (d2s) for properly conducted tests on the same material under the three conditions [bulk (dry), bulk (SSD), and apparent specific gravity] was lower than the precision estimates in AASHTO T 84 test method. However, the d2s determined in this study for absorption was higher than the precision estimate in AASHTO T 84 test method.]]></description>
      <pubDate>Mon, 30 Jun 2025 09:17:02 GMT</pubDate>
      <guid>https://trid.trb.org/View/2562006</guid>
    </item>
    <item>
      <title>Simple Analytical Procedure to Estimate Optimum Asphalt Content</title>
      <link>https://trid.trb.org/View/2522002</link>
      <description><![CDATA[Asphalt concrete mix design is an iterative process that involves material selection, testing, and evaluation to meet the design criteria. Traditional mix design procedures require many samples to establish the aggregate structure and optimum asphalt content. For a trial aggregate blend, the Marshall and Superpave mix design methods require at least 17 and 12 samples, respectively, for determination of the optimum asphalt content portion of the mix design. This article proposes a new methodology for estimating the optimum asphalt content of a mix. The proposed procedure is based on the same equations that are currently used in the traditional asphalt mix design procedures but requires fewer samples (4 or 5). It is based on the premise that although both compaction level and aggregate structure control the optimum asphalt content and volumetrics of a mix, in practice, only the latter is used by designers to meet mix design requirements, including the compaction level. The procedure is based on the estimation of the asphalt content required to achieve a bulk specific gravity of a mix that meets simultaneously the selected design air voids and voids in mineral aggregate. To validate the procedure, a mix design was developed in the lab and two additional datasets with existing designs were compiled from producers and public sources and analyzed. The validation process with the lab sample demonstrated the effectiveness of the procedure by eliminating the first selected aggregate blend and estimated asphalt content based on only five samples. The validation with existing data sources also showed excellent agreement.]]></description>
      <pubDate>Wed, 28 May 2025 12:01:52 GMT</pubDate>
      <guid>https://trid.trb.org/View/2522002</guid>
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    <item>
      <title>Understanding and Improving Pavement Milling Operations</title>
      <link>https://trid.trb.org/View/2529819</link>
      <description><![CDATA[Asphalt milling is an essential construction activity. It requires concentrated high-intensity applications of force to the existing pavement to remove the asphalt material. The impact that the induced stresses have on the pavement below the mill line is unknown. Consequently, selected milling parameters rarely consider the impact the milling may have on the remaining layers. This study evaluates milling parameters to provide an enhanced understanding of their impacts on the layer directly below the mill line. Five parameters were evaluated and include the time between milling and post-mill overlay construction, existing pavement structure, temperature while milling, depth of milling relative to layer interface, and rotor speed. Pre- and post-milling cores were collected adjacent to each other and evaluated for physical and mechanical properties. The measured properties of the pre- and post-milling cores were statistically compared to determine the impact of milling operations on the integrity of the asphalt concrete immediately below the mill line. Based on the results from this study, it was determined that leaving milled pavement exposed for longer periods of time or milling at cooler temperatures can cause a decrease in the strength of the layer below the mill line and a decrease in the expected pavement life of the new pavement structure. The depth of milling or changing the rotor speed while milling did not have significant impacts on the layer directly below the mill line. In consideration of the results of this study, research with a wider variety of pavements and milling conditions is warranted.]]></description>
      <pubDate>Thu, 03 Apr 2025 09:07:35 GMT</pubDate>
      <guid>https://trid.trb.org/View/2529819</guid>
    </item>
    <item>
      <title>Implementation of Asphalt Mixture Automated Testing System with Zero Intervention (AMAZE)</title>
      <link>https://trid.trb.org/View/2437697</link>
      <description><![CDATA[The research team will assist the Texas Department of Transportation (TxDOT) with implementing Asphalt Mixture Automated Testing System with Zero Intervention (AMAZE) developed in research project 0-6674-03, “Automated IDEAL Cracking and Rutting Tests”. The researchers will write test procedures tailored for AMAZE. Working with TxDOT, the research team will enhance AMAZE to measure specimen dimension and handle field cores with various thickness. The researchers will then use the findings and data generated from this implementation project to develop and teach implementation workshop for TxDOT.]]></description>
      <pubDate>Thu, 03 Oct 2024 11:39:11 GMT</pubDate>
      <guid>https://trid.trb.org/View/2437697</guid>
    </item>
    <item>
      <title>Impact of Laboratory Air Voids Using AASHTO T 166 versus AASHTO T 275 for HMA Specimens Compacted under AASHTO T 312</title>
      <link>https://trid.trb.org/View/2389925</link>
      <description><![CDATA[Hot mix asphalt (HMA) materials engineering is the process of identifying mix characteristics that reasonably reflect expected field performance. Air voids is a fundamental mix property used for the acceptance of HMA mixes. Two test methods, AASHTO T 166 and AASHTO T 275, are currently used by Caltrans to determine the bulk specific gravity of the compacted HMA mix to determine air voids in accordance with AASHTO T 269. The AASHTO T 166 procedure is required to determine bulk specific gravity for the determination of mix air voids for California Test 389 and AASHTO T 283. The current study aims to evaluate the practicality of using AASHTO T 166 (using saturated surface-dry) in lieu of AASHTO T 275 (using paraffin) for the determination of laboratory air voids for dense-graded HMA mixes as part of AASHTO T 269. This effort used data generated from a previous interlaboratory study conducted by the Caltrans Reference Sample Program. The study was done using a 3/4″ Type A HMA with 15% reclaimed asphalt pavement meeting Caltrans specifications. Seventy-six Caltrans-accredited laboratories participated in this study. Results showed that the average bulk specific gravity (Gmb) using AASHTO T 166 and T 275 were 2.475 and 2.484, respectively. The resulting air voids calculated based on theoretical maximum specific gravity (Gmm) from AASHTO T 209 were slightly higher when using AASHTO T 166 (5.21%) as compared to AASHTO T 275 (4.86%). The practical implication of this change would be that, to achieve a target 4% air voids when using AASHTO T 166 in place of AASHTO T 275, a marginal increase in binder content of 0.1% would be required for this dense-graded HMA mix. Three additional mixtures were also evaluated. The increases in binder content were: 0.05%, 0.2%, and 0.3%, respectively. It is anticipated that this trend would be valid for all HMA mixtures; however, the actual increase in binder content will be mix-specific.]]></description>
      <pubDate>Mon, 24 Jun 2024 09:31:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/2389925</guid>
    </item>
    <item>
      <title>Jämförande provning korndensitet och vattenabsorption : jämförelse mellan laboratorier</title>
      <link>https://trid.trb.org/View/2388967</link>
      <description><![CDATA[Test comparisons have been carried out between road material laboratories in Sweden for particle density and water absorption according to SS-EN 1097-6:2013 in 2020. The comparison was made with four materials, two with the grading 11/16 mm and two with the grading 0/4 mm. Each participant performed double tests of each material. There were 49 laboratories participating. Generally, are there small variations for particle density between the participants. The coefficient of variation1 is less than 1%. For the water absorption, the variations between the participating laboratories are relatively large. However, this can partly be explained with that the results consists of low values and the "natural" variation is almost as great as the results, about 0.3%. Water absorption has just under 30% in variation coefficient1for the coarser materials in grading 11/16 mm and about 60–70% for the finer ones in grading 0/4 mm. Clearly anomalous participants for particle density for the finer materials is laboratory number 20 with very low results, where even laboratory No. 6 is located low. For water absorption, is it mainly laboratories 33, 12 and 50 that most clearly stand out in a negative way. In general, are the repeatability and the reproducibility, in this comparing analysis better or equal with SS-EN 1097-6:2013.]]></description>
      <pubDate>Mon, 10 Jun 2024 14:04:47 GMT</pubDate>
      <guid>https://trid.trb.org/View/2388967</guid>
    </item>
    <item>
      <title>Determining Asphalt Mixture Properties Using Imaging Techniques</title>
      <link>https://trid.trb.org/View/2239872</link>
      <description><![CDATA[This study introduces imaging technology to determine the bulk specific gravity (Gmb) of compacted asphalt mixture specimens. Using an advanced three-dimensional scanner, a fast, accurate technique for determining compacted asphalt mixture specimen Gmb was developed. The feasibility of this technique was evaluated by testing a collection of asphalt mixtures, including dense-graded and stone mastic asphalt mixtures. The results were compared with those obtained using the currently-specified Gmb measurement methods of AASHTO T166 and CoreLok. The proposed scanning technique was also used for both laboratory-prepared and field-cored specimens to determine its reliability and reproducibility. The study results suggest the proposed imaging technique is effective in decreasing Gmb measurement variation as well as in improving the accuracy and reproducibility. Additionally, the results indicate the proposed technique can be applied to any asphalt specimen, regardless of mixture type, aggregate sizes, or fabrication technique.]]></description>
      <pubDate>Tue, 12 Sep 2023 09:20:15 GMT</pubDate>
      <guid>https://trid.trb.org/View/2239872</guid>
    </item>
    <item>
      <title>Development of a Correlation between CoreLok® and AASHTO T 85 Tests for Specific Gravity of Coarse Aggregates used in Idaho</title>
      <link>https://trid.trb.org/View/2229002</link>
      <description><![CDATA[Specific gravity and absorption values of coarse aggregates are typically measured in accordance with the AASHTO T 85 standard. The test requires considerable experience to recognize the stage when a soaked sample reaches the saturated surface dry (SSD) condition upon drying. The CoreLok device offers an alternative approach which can be completed in less than 45 minutes compared to the 24 hours required by the AASHTO procedure. This study investigated the results from AASHTO T 85 and CoreLok testing of coarse aggregates to develop a correlation between bulk (dry) specific gravity (Gsb) values measured using the two test procedures. Blended samples, consisting of coarse and fine aggregates, were also tested to evaluate the use of the CoreLok method to reliably determine Gsb values. After testing 15 coarse aggregates and 17 blended aggregates, this study developed three equations that may be used to modify the CoreLok Gsb results to more closely reflect Gsb values based on AASHTO T 85 tests. The recommended equation uses the CoreLok Gsb and the fine aggregate percentage to predict the equivalent AASHTO T 85 Gsb with an R² = 0.967. Furthermore, five reclaimed asphalt pavement (RAP) materials were also tested to see if the Gsb of the uncoated aggregate could be determined using the CoreLok method. Preliminary results indicate that the CoreLok Gsb results can be reliably calculated if the effective and absorbed binder content is known, or presumed, based on experience.]]></description>
      <pubDate>Tue, 29 Aug 2023 16:47:01 GMT</pubDate>
      <guid>https://trid.trb.org/View/2229002</guid>
    </item>
    <item>
      <title>Superpave Design Aggregate Structure Considering Uncertainty: II. Evaluation of Trial Blends</title>
      <link>https://trid.trb.org/View/2129490</link>
      <description><![CDATA[The current evaluation of Superpave design aggregate structure is deterministic. The design involves evaluation of selected trial blends based on volumetric, compaction, and dust proportion requirements. This article incorporates the uncertainties of all 17 variables involved in the process, measured by the coefficient of variation (CV), and develops a revised procedure for comparing mixture properties with the performance-based criteria. The uncertainties of eight measured properties are propagated through the calculation and make the uncertainty of some variables very large. Issues related to the reliability of some variables (CV > 25 %) are discussed and criteria to resolve them are established. The developed mathematical formulas of uncertainty were verified using Monte Carlo simulation. The results show that the potentially unreliable variables are as follows: volume of absorbed asphalt, percentage of absorbed asphalt, and percent voids in total mix at the design compaction level. A tool is provided to help the designer trace the uncertainty of the unreliable variables back to the measured properties so that their precisions may be revised. The current National Cooperative Highway Research Program–recommended precisions for specific gravities were found to be generally satisfactory. However, further research should continue to improve the precision of specific gravity measurements as some intermediate variables may still become unreliable.]]></description>
      <pubDate>Thu, 27 Apr 2023 17:05:02 GMT</pubDate>
      <guid>https://trid.trb.org/View/2129490</guid>
    </item>
    <item>
      <title>Laboratory Dielectric Measurement System (LDMS) for Asphalt Mixture Bulk Specific Gravity Determination</title>
      <link>https://trid.trb.org/View/2122503</link>
      <description><![CDATA[Bulk specific gravity (Gmb) is measured routinely during mixture design and quality assurance processes for asphalt mixtures. The current AASHTO (American Association of State Highway and Transportation Officials) specifications for measuring (Gmb) are: AASHTO T331: Bulk Specific Gravity (Gmb) and Density of Compacted Asphalt Mixtures Using Automatic Vacuum Sealing Method; and AASHTO T166: Standard Method of Test for Bulk Specific Gravity (Gmb) of Compacted Asphalt Mixtures Using Saturated Surface-Dry Specimens. A dielectric profiling system (DPS) is a new technology that is being used to evaluate variations in the air void content and density of asphalt pavements in the field during and after construction for quality control purposes. The DPS technology utilizes measurement of the dielectric constant of pavement materials using a miniaturized ground penetrating radar (GPR) system. The technology within DPS has been adapted for routine laboratory measurement of dielectric constant of asphalt concrete specimens using a miniaturized source and receiver. This project explores the use of a laboratory dielectric measurement system (LDMS) which measures the dielectric constant of pavement materials using ground penetrating radar (GPR) system for determining Gmb measurement as an alternative procedure to the current AASHTO specifications. Due to the minimal equipment needs and low operational cost, routine usage of LDMS has the potential for increased efficiency and accuracy of laboratory Gmb measurements.]]></description>
      <pubDate>Mon, 27 Feb 2023 17:41:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/2122503</guid>
    </item>
    <item>
      <title>Properties of Tropical Black Clay Treated with Selected Admixtures</title>
      <link>https://trid.trb.org/View/1974614</link>
      <description><![CDATA[The properties of tropical black clay (also known as black cotton soil, BCS) treated with cement kiln dust (CKD) and locust bean waste ash (LBWA) was studied. Tests performed include index and compaction using British Standard light (BSL); West African Standard (WAS) (or Intermediate) and British Standard heavy (BSH) energies. Statistical analysis was performed using two-way analysis of variance (ANOVA) incorporated in Microsoft excel software. Results obtained show that the specific gravity value of the natural BCS (2.4) reduced to a minimum value of 2.33 at 2% CKD/10% LBWA treatment. Peak liquid limit (LL) value of 55.6% was recorded at 3% CKD/6% LBWA treatment, minimum plastic limit (PL) value of 15.6% recorded for 3% CKD/6% LBWA treatment, while plasticity index (PI) value recorded a peak value of 40.0% at 3% CKD/6% LBWA treatment. The compaction characteristics, that is, maximum dry density (MDD and optimum moisture content (OMC) decreased and increased, respectively, with higher CKD/LBWA treatment. Generally, ANOVA results show that CKD and LBWA had significant effects on BCS. Although CKD/LBWA treatment improved the properties of BCS; however, the Nigerian General Specifications requirements of LL ≤ 35.0% and PI ≤ 12.0% for sub-base material in road construction were not met. It is recommended that BCS be minimally treated with 1% CKD/10% LBWA for use as subgrade material for the construction of low-volume roads.]]></description>
      <pubDate>Wed, 22 Feb 2023 09:57:43 GMT</pubDate>
      <guid>https://trid.trb.org/View/1974614</guid>
    </item>
    <item>
      <title>Asphalt mix design: Discussion on the bulk specific gravity procedure influence on the results obtained from empirical, volumetric, and performance-based methods</title>
      <link>https://trid.trb.org/View/1970933</link>
      <description><![CDATA[The purpose of this paper is to shed light on the impact of laboratory procedures for air void content determination on the design and mechanical performance of an asphalt mixture. A dense-graded AC20 and gap-graded SMA12.5 mixtures were designed using empirical and volumetric design methods. Volumetric properties are determined based on several bulk gravity procedures: dry, SSD (saturated surface dry), paraffin coated, vacuum-sealed and dimensions. Relationships between the mixtures designed with bulk specific gravity procedures and their performance made it possible to analyze the impact of these procedures on the properties and performance of the mixtures. Global performance variations were relevant, although the differences were moderate considering the common procedures (less than 10%). Impact on a determined performance property can be considerable, with variations up to 70%. For specific applications, this can have a significant effect on the overall in-service performance.]]></description>
      <pubDate>Mon, 27 Jun 2022 17:16:29 GMT</pubDate>
      <guid>https://trid.trb.org/View/1970933</guid>
    </item>
    <item>
      <title>Effect of MIST conditioning on the air voids and permeability of hot asphalt mixes containing reclaimed asphalt pavement</title>
      <link>https://trid.trb.org/View/1976730</link>
      <description><![CDATA[Traffic traversing on an asphalt pavement leads to the development of hydrodynamic stress. Hence, moisture-induced stress tester (MIST) was developed to simulate the phenomenon. However, MIST has the propensity to affect the air voids (Vₐ) and permeability (k) characteristics of the conditioned mix. In this study, an attempt has been made to understand the effect of varying stress cycles of MIST on Vₐ and k. Furthermore, due to the advantages associated with recycled asphalt pavement (RAP) mixes, this study also considers RAP in varying proportions of 10%, 20%, 30% and 40% by weight. The results indicate that MIST conditioning affects both Vₐ and k of asphalt mixes. RAP mixes were observed to undergo higher changes in Vₐ and depicted higher k than control mix. It is expected that the results of the current study may prove to be significant in explaining the change in performance parameters due to MIST conditioning.]]></description>
      <pubDate>Fri, 17 Jun 2022 17:07:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/1976730</guid>
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