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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>
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    <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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    <item>
      <title>Identification of microstructural characteristics in semi-flexible pavement material using micromechanics and nano-techniques</title>
      <link>https://trid.trb.org/View/1690925</link>
      <description><![CDATA[Semi-flexible pavement (SFP) has been promoted to apply in pavement engineering mainly for its excellent performance in rutting resistance. However, due to the material characteristics of three-phase heterogeneous phase and the structural characteristics of dense skeleton interlocking structure, the microstructure of semi-flexible pavement material is complicated, greatly influencing the mechanical properties of the material. This research aims to identify the two characteristics of SFP employing micromechanical models as well as nano-techniques, including nanoindentation (NI), Scanning Electron Microscope (SEM) and energy dispersive spectrum analysis (EDS). Two interlocking factors were introduced in the three-phase micromechanical model to characterize the interlocking effect. Identification of the asphalt mastic phase in SFP was implemented as the basis of stiffening correction in the micromechanical model. Because four different layers were found in the asphalt phase of SFP that was difficult to simulate, a general stiffening correction was used in the improved micromechanical model. The final model considering the interlocking and asphalt stiffening effects can characterize the property of SFP well. It was found that grouting cement has an enhancement function on the viscoelastic interlocking effect while does little on the elastic interlocking effect. Meanwhile, more grouting cement will lead to more asphalt-cement stiffening effect. An equivalent dynamic modulus of the asphalt phase-phase from the micromechanical model was proposed in the end, which has been proven corresponding to the experimental results of NI test.]]></description>
      <pubDate>Thu, 23 Apr 2020 15:58:15 GMT</pubDate>
      <guid>https://trid.trb.org/View/1690925</guid>
    </item>
    <item>
      <title>Performance evaluation of semi-flexible permeable pavements under cyclic loads</title>
      <link>https://trid.trb.org/View/1685071</link>
      <description><![CDATA[Traditional permeable pavements are constructed with rigid aggregates and have low load-bearing capacity. The crack development due to loads and unpredicted ground movements reduces their service life. The widespread cracks on the surface of conventional asphalt accelerate the pavement structure deterioration and reduce the overall service life. In this research, the end-of-life tyre products shredded to tyre-derived aggregates (TDAs) were utilised along with crushed rock (CR) in different fractions of a porous structure to enhance the flexibility of permeable pavement whilst maintaining the minimum load-bearing capacity for use in footpath and low-volume roads. The transitional behaviour from a semi-rigid structure owing to the rigidity of CR aggregates to a more flexible structure for mixtures at higher TDA content was investigated. The impact of rigid-rigid and flexible-rigid inter-particular contacts at low and high stress levels is investigated. The plastic and recoverable deformations of the flexible-rigid blends under monotonic and repeated loadings are compared. Also, the impact of polyurethane binder content on improving the mixtures flexural strength is investigated. The lightly bonded flexible-rigid mixtures are a viable replacement for traditional porous pavements to improve the load-bearing mechanism and increase the flexibility of pavement.]]></description>
      <pubDate>Tue, 17 Mar 2020 14:27:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/1685071</guid>
    </item>
    <item>
      <title>Optimal proportioning of grout constituents using mathematical programming for semi flexible pavement</title>
      <link>https://trid.trb.org/View/1635364</link>
      <description><![CDATA[This study proposes a mathematical approach to obtain the optimal proportion of the grout constituents for a semi-flexible pavement. Grout mixes were prepared using three different water-cement ratios, three sand sizes, one sand-cement ratio, four/five different percentages of super plasticizer, and two different types of super plasticizer. The grout mixes were tested for flowability and strength using Marsh cone test and cube compressive strength test, respectively. The laboratory results were utilized to validate the proposed mathematical programming approach while obtaining the optimal proportion of grout constituents. Experimental results indicated that a minimum of 2% naphthalene super plasticizer and 1% polycarboxylate super plasticizer are required, irrespective of any combination, to achieve the desired flow time of the grout. The flow time and compressive strength were found to be associated with type of super plasticizer used. The proposed approach was found to be statistically satisfactory, with 95% confidence level, for determining the optimum grout constituents. The validation of the grout penetrability, using the proposed approach, has also been provided. Researchers and field engineers may consider to employ this analytical approach for grout constituent proportioning by partial or total replacement of cement with silica fume or fly ash.]]></description>
      <pubDate>Wed, 14 Aug 2019 14:31:32 GMT</pubDate>
      <guid>https://trid.trb.org/View/1635364</guid>
    </item>
    <item>
      <title>Hybrid Concrete for Advancing Pavement Performance</title>
      <link>https://trid.trb.org/View/1592056</link>
      <description><![CDATA[Rutting, caused by a depression or groove of traveling wheels worn into a road, is a major problem of conventional asphalt or flexible pavements, and is primarily due to plastic deformation of the asphalt concrete near the pavement surface. To overcome this problem, a hybrid, made with asphalt (flexible) pervious concrete filled with Portland cement (rigid) mortar, called casting cement asphalt mixture (CCAM), has been developed. During the development process, various CCAMs were made with Iowa concrete materials. Experiments were conducted to gauge optimal porosity of asphalt pervious concrete and optimal flowability of mortar for CCAMs. The basic engineering properties of these CCAMs, such as strength, shrinkage, and freeze-thaw durability, were evaluated. The results show that CCAMs can be produced successfully by using pervious concrete of 25% porosity and rapid set cement grout with very high flowability. The calcium sulphoaluminate cement grout used in this study attained strength greater than 18 MPa (2,600 psi) in less than 12 hours. Therefore, a CCAM pavement could open to traffic at a much earlier time than a conventional Portland cement concrete roadway. While asphalt concrete displayed a 9 mm rut after being subjected to 10,000 wheel track cycles during a wheel track rutting test, the CCAM showed a less than 1 mm rut. However, as the CCAM is neither asphalt nor Portland cement concrete, a big project challenge was to find appropriate test methods for evaluating key properties of CCAM, especially the method for testing its freeze-thaw durability. Although CCAM has attracted a great deal of attention in Europe and Asia, most applications have been in warm climate regions. Few applications of CCAM have been conducted in the US, especially in cold climate regions. Further investigation needs to be done on the CCAM freeze-thaw durability before this new material is applied to Iowa pavements.]]></description>
      <pubDate>Sun, 24 Mar 2019 20:11:27 GMT</pubDate>
      <guid>https://trid.trb.org/View/1592056</guid>
    </item>
    <item>
      <title>Development of Hierarchical Ranking Strategy for the Asphalt Skeleton in Semi-Flexible Pavement</title>
      <link>https://trid.trb.org/View/1577350</link>
      <description><![CDATA[This study evaluates the suitability of seven different asphalt mixes, prepared at a wide range of binder content (2–5%), to be used for semi-flexible pavement. A hierarchical list of tests, including draindown, air void content, voids in coarse aggregate (VCA) ratio, permeability and Cantabro loss have been selected for accepting/rejecting the mixes based on limiting values assigned to each test parameter. Indirect tensile strength (ITS) test is finally used as a fatigue performance criteria to evaluate the relative performance of the mix. This study also proposes a simple methodology of ranking the mixes based on the priority given to the ‘type’ of test. The proposed method tends to eliminate the constraint imposed by the limiting criteria under each test.The hierarchical method of eliminating/selecting mixes was found to be appropriate for arriving at the mixes with most desirable properties as a surface layer in semi-flexible pavement. Eight mixes including M-1 (BSI): 3.5%, M-1: 4%, M-2 (Boundy): 3.5%, M-3 (Densiphalt 8): 4%, M-3: 4.5%, M-4 (Densiphalt 12): 4%, M-4: 4.5% and M-5 (Setyawan): 4% were found to satisfy all the limiting criteria imposed on various test parameters. It was shown, using a suitable example of six different cases, that the final rank based on the proposed methodology is a function of the priority given to the type of test by the designer. Out of the eight mixes, meeting all the desirable properties, M-4: 4%, M-1: 4% and M-4: 4.5% were ranked highest and are recommended to be used for semi-flexible pavement.]]></description>
      <pubDate>Thu, 21 Feb 2019 09:54:56 GMT</pubDate>
      <guid>https://trid.trb.org/View/1577350</guid>
    </item>
    <item>
      <title>Study on the mechanical performance and application of the composite cement–asphalt mixture</title>
      <link>https://trid.trb.org/View/1563305</link>
      <description><![CDATA[The rigidity of matrix mixture asphalt (MMA) is increased by the combination with cement mortar, and the performance of asphalt pavement has been better changed in the stabilities of high temperature rut and low temperature cracking and water damage. The research problems in this project mainly focus on the combinations among cement mortar and MMA and mechanical performance of composite cement–asphalt mixture (CCAM), etc. In the project, the CCAM is produced by pouring cement mortar into MMA, and the mechanical performance of CCAM has been researched. The research contents include the production technology and mechanical performance and construction technology of CCAM. Through the test data of CCAM in the mechanical performance, and compared with the performance of AC-16 MMA, the paper has analysed the mechanical performance and application of CCAM in high temperature rut and low temperature cracking and water damage, the components design and production technology and construction technology of CCAM have been put forward. The rigidity of MMA has been improved and the mechanical performance of CCAM has also met the design standards, it is suggested that CCAM can be applied as a new composite pavement materials.]]></description>
      <pubDate>Sat, 03 Nov 2018 15:17:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/1563305</guid>
    </item>
    <item>
      <title>The Evaluation of an Innovative Semiflexible Pavement Wearing Course Mixture Using Fast Falling Weight Deflectometer</title>
      <link>https://trid.trb.org/View/1496371</link>
      <description><![CDATA[Road pavements are traditionally classified in three categories, according to their global stiffness. Another type of pavement called semi-flexible pavement has been also successfully applied especially in those areas subjected to heavy and slow moving loads. Semi-flexible pavements are characterised by a wearing course of Grouted Macadam, a composite pavement material. It combines the properties of the asphalt pavements with the concrete ones. On the other side the laying process is slow and expensive, commonly divided into two phases: the laying of the porous asphalt layer and the filling of the voids with a cementitious fluid grout. The realization complexity leads to long realization times and high initial costs. Therefore the use of semi-flexible pavements has been limited to some fields of application and areas. During the last years an innovative material has been developed to be used in semi-flexible pavements. The basic idea was to find an alternative to Grouted Macadam, easier and cheaper to be realized. This material has to provide similar or even superior characteristics compared to traditional Grouted Macadam and meanwhile its construction time has to be reduced, avoiding the need for dividing the laying process. In this paper an experimental program involving the use of Fast Falling Weight Deflectometer (FastFWD), as an Accelerated Pavement Testing (APT) device, to evaluate the long term performances of this innovative material is presented. Results regarding the validation of this new material by means of FastFWD appear promising both in terms of material stiffness evolution and resistance to dynamic load repetitions.]]></description>
      <pubDate>Wed, 28 Feb 2018 13:25:58 GMT</pubDate>
      <guid>https://trid.trb.org/View/1496371</guid>
    </item>
    <item>
      <title>Semi-Flexible Base's Material Properties and Pavement Structure Applicability</title>
      <link>https://trid.trb.org/View/1113844</link>
      <description><![CDATA[For the special nature of semi-flexible base's road performance, this paper studies the Marshall stability, splitting strength and compressive strength tests of the semi-flexible mixture. First, several steps which should be taken to achieve the optimal mix proportion are presented as below: optimal gradation, optimal fluid content, optimal asphalt content, optimal cement content. Secondly based on a project, the paper introduces systematically the performance, proportioning design and construction process of semi-flexible mixture. Finally, with analysis of strengths, weaknesses and pavement applicability between semi-rigid and semi-flexible base material, proposing that semi-flexible base as a structural layer can be a good solution to the problem of reflecting crack phenomenon of asphalt pavements. It introduces the application of three semi-flexible bases in pavement structures in detail, including the construction and reconstruction of asphalt and cement concrete pavements, aiming at providing reference to its extension and application.]]></description>
      <pubDate>Fri, 14 Sep 2012 11:15:01 GMT</pubDate>
      <guid>https://trid.trb.org/View/1113844</guid>
    </item>
    <item>
      <title>The Application of Semi-Flexible Pavement on Heavy Traffic Roads</title>
      <link>https://trid.trb.org/View/904178</link>
      <description><![CDATA[Semi-flexible pavement mixture and AC-16 asphalt concrete performance is this paper's focus. Aggregates meeting the lower limit, middle value, and upper limit of the mother mixture gradation curves were used to prepare semi-flexible mixtures. The low temperature performance of both mixtures was investigated through the indirect tensile test and the low temperature bending test. There was determination of brittle point temperatures and strain energy density indices. Study results showed that, in comparison with AC-16 styrene-butadiene-styrene (SBS) modified asphalt concrete, semi-flexible pavement mixture has excellent low temperature crack resistance. Also, crumb rubber modified semi-flexible pavement water stability, low temperature crack resistance, and high temperature stability were studied in the laboratory, and there was comparison with AR-AC-16 asphalt concrete with asphalt rubber. Finally, there was construction of test pavement. That semi-flexible pavements with asphalt rubber give excellent performance was shown in both laboratory tests and the test pavement. Good application prospects are enjoyed by such pavements, especially for service as a surface course on pavements with heavy traffic.]]></description>
      <pubDate>Mon, 30 Nov 2009 08:54:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/904178</guid>
    </item>
    <item>
      <title>A Review of Practical Experience Throughout Europe on Deterioration in Fully-Flexible And Semi-Rigid Long-Life Pavements</title>
      <link>https://trid.trb.org/View/795037</link>
      <description><![CDATA[This article looks at some of the observations that have been made in a number of European countries on the behavior of fully-flexible and semi-rigid pavements.  Evidence for the existence of long-life pavements has been collected from expert opinion on deterioration as well as practical measurements from pavements on national networks. Observations on rutting, cracking, deflections and overall performance are presented from the UK, The Netherlands and Hungary. These observations confirm that certain pavements do not deteriorate structurally and hence can have unexpectedly long-lives, i.e. they can be classified as ‘long-life pavements’, thus providing the highway authorities with many potential economic benefits. The European Long-Life Pavements Group (ELLPAG) is seeking to further promote these benefits through the more widespread use of these pavements in Europe and is aiming to develop coordinated research to achieve this; a short description of ELLPAG is provided.]]></description>
      <pubDate>Fri, 29 Dec 2006 11:06:34 GMT</pubDate>
      <guid>https://trid.trb.org/View/795037</guid>
    </item>
    <item>
      <title>JOINT LESS PAVEMENTS FOR HEAVY-DUTY AIRPORT APPLICATION: THE SEMI-FLEXIBLE APPROACH. IN: ADVANCING AIRFIELD PAVEMENTS</title>
      <link>https://trid.trb.org/View/742661</link>
      <description><![CDATA[The study examined the experience of the semi flexible pavement (SFP) concept in Copenhagen Airport that dates back 25 years. Several significant improvements have been added to the original concept and a very high performance has been achieved.  It is possible today to design SFP for all types of aircraft.  Since the 1970s, a total of 300,000 square meters  of SFP has been applied.  For an alternative to concrete slab pavement, the Copenhagen Airport introduced the heavy duty semi flexible pavement (HDSFP) which can be used on heavy loaded areas and especially areas subject to repeated static loads present at stand gates equipped with electronic docking systems.  The HDSFP design strives to minimize the total layer thickness of the bituminous binder and base layers to minimize the risk of deformations in these layers.]]></description>
      <pubDate>Tue, 26 Oct 2004 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/742661</guid>
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