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The Global ETD Search service is a free service for researchers
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Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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Showing 1 to 8 of 8 (0.034 seconds)Spelling suggestions: "subject:"microdeval"" "subject:"froideval""
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Analysis of aggregate imaging system (AIMS) measurements and their relationship to asphalt pavement skid resistanceLuce, Anthony David 15 May 2009 (has links)
This thesis consists of two parts. The first part includes analyses of the
correlation between the results of two Aggregate Imaging System (AIMS) units. These
analyses have led to refinements of the AIMS analysis methods of angularity and
texture, which resulted in reduced variability in the results and better correlation between
the two AIMS units. The refined analysis methods were used to establish a database of
the shape characteristics of about 100 aggregate samples from the state of Texas and to
propose a new method for the classification of aggregates based on their shape
characteristics. This new method of classification is for use in the Texas Department of
Transportation (TxDOT) wet weather accident reduction program (WWARP). The use
of AIMS texture index and variability in texture within an aggregate source is proposed
instead of the British Polish Value (BPV) for classifying aggregates used in pavement
surfaces.
The second part of the thesis investigates the relationship between shape
characteristics and asphalt pavement skid resistance. Many states have implemented wet
weather accident reduction programs aimed at maintaining acceptable levels of pavement skid resistance. Proper aggregate selection before construction aids in
maintaining acceptable levels of skid resistance throughout the life of the pavement.
Several predictive models of pavement skid resistance have been developed over
the years. Some of these models account for the influence of aggregate characteristics
on pavement skid resistance, primarily through incorporating the results of the BPV test
in the model. However, the BPV test is known to have high variability and dependence
on experimental factors that are not related to the actual aggregate resistance to
polishing. AIMS offers a method to measure aggregate shape characteristics directly in
a relatively short period of time. The new method for relating aggregate shape
characteristics to pavement skid resistance was verified by relating skid resistance
measurements from field test sections to measured aggregate properties from the
laboratory. This methodology is expected to be the basis for further study to form a
more comprehensive and verified model for the prediction of pavement skid resistance
that incorporates measured aggregate properties from the AIMS system.
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Development of experimental methods for the evaluation of aggregate resistance to polishing, abrasion, and breakageMahmoud, Enad Muhib 25 April 2007 (has links)
Aggregate properties influence different aspects of asphalt pavement performance. Aggregate polishing characteristics are directly related to pavement surface frictional properties and thus to skid resistance. Aggregate resistance to degradation (abrasion and breakage) is another important property that influences pavement performance. Aggregate degradation could take place during production due to plant operations and during compaction, leading to change in aggregate characteristics and mix properties. In addition, aggregate resistance to degradation is important in mixes such as Stone Matrix Asphalt (SMA) and Open Graded Friction Course (OGFC) that rely on stone-to-stone contacts among coarse aggregates. Some aggregates in these mixes fracture due to the high stresses at contact points. Many test methods exist for measuring aggregate polishing and degradation, but a critical review of these methods reveals that they suffer from being time consuming, are unable to differentiate between aggregates with distinct resistance to polishing, or unable to differentiate between aggregate resistance to abrasion and breakage. New methodologies are needed to give better assessment of aggregate resistance to polishing, abrasion, and breakage. The thesis presents the development of new methods for measuring aggregate resistance to polishing, abrasion, and breakage. These methods rely on measurements using the Aggregate Imaging System (AIMS) and Micro-Deval. The new method for measuring aggregate resistance to polishing monitors change in aggregate texture as a function of polishing time. As such, it provides the initial texture, rate of polishing, and final texture. The new method for measuring aggregate degradation is capable of distinguishing between breakage and abrasion. In this method, abrasion is defined as the reduction in aggregate angularity, while breakage is defined by fracture of particles. The new methods are shown to be rapid and accurate, and they require reasonable training. Since both AIMS and Micro-Deval are used in the new methods, it was necessary to evaluate the repeatability of these two methods. Measurements using two AIMS units and two Micro-Deval machines were used to assess the variability. There was no statistical difference between the measurements of the two AIMS units or between the measurements of the two Micro-Deval units.
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Development of experimental methods for the evaluation of aggregate resistance to polishing, abrasion, and breakageMahmoud, Enad Muhib 25 April 2007 (has links)
Aggregate properties influence different aspects of asphalt pavement performance. Aggregate polishing characteristics are directly related to pavement surface frictional properties and thus to skid resistance. Aggregate resistance to degradation (abrasion and breakage) is another important property that influences pavement performance. Aggregate degradation could take place during production due to plant operations and during compaction, leading to change in aggregate characteristics and mix properties. In addition, aggregate resistance to degradation is important in mixes such as Stone Matrix Asphalt (SMA) and Open Graded Friction Course (OGFC) that rely on stone-to-stone contacts among coarse aggregates. Some aggregates in these mixes fracture due to the high stresses at contact points. Many test methods exist for measuring aggregate polishing and degradation, but a critical review of these methods reveals that they suffer from being time consuming, are unable to differentiate between aggregates with distinct resistance to polishing, or unable to differentiate between aggregate resistance to abrasion and breakage. New methodologies are needed to give better assessment of aggregate resistance to polishing, abrasion, and breakage. The thesis presents the development of new methods for measuring aggregate resistance to polishing, abrasion, and breakage. These methods rely on measurements using the Aggregate Imaging System (AIMS) and Micro-Deval. The new method for measuring aggregate resistance to polishing monitors change in aggregate texture as a function of polishing time. As such, it provides the initial texture, rate of polishing, and final texture. The new method for measuring aggregate degradation is capable of distinguishing between breakage and abrasion. In this method, abrasion is defined as the reduction in aggregate angularity, while breakage is defined by fracture of particles. The new methods are shown to be rapid and accurate, and they require reasonable training. Since both AIMS and Micro-Deval are used in the new methods, it was necessary to evaluate the repeatability of these two methods. Measurements using two AIMS units and two Micro-Deval machines were used to assess the variability. There was no statistical difference between the measurements of the two AIMS units or between the measurements of the two Micro-Deval units.
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Recommendations for coarse aggregate testing requirements for use in portland cement concreteClement, John Christopher, 1985- 24 February 2014 (has links)
Coarse aggregate is often one of the largest volume occupying components in a portland cement concrete system. With increases in transportation costs and depletion of many of the aggregate sources currently in use the need to reevaluate the performance of aggregates in concrete has arisen. Current aggregate testing requirements for many organizations have not been updated in decades, even with the advancements in aggregate testing equipment that are currently available.
This research project investigates current used and potential test methods for evaluating coarse aggregate for use in portland cement concrete. Testing focused on determining the most appropriate aggregate property to evaluate and then determining the correlation to mechanical concrete properties. Relationships between potential aggregate tests and currently used aggregate tests were evaluated to determine if compatible relationships between methods were evident.
For this purpose concrete mixtures were made at a fixed aggregate volume to establish if a link was evident between aggregate test properties and concrete. To establish a link between laboratory and real world performance field sites with known distress were visited to better establish limits for aggregate testing requirements. Results obtained provided the basis for recommendations for testing requirements and limits to be used for aggregates in portland cement concrete. / text
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An Assessment of Moisture Induced Damage in Asphalt PavementsHtet, Yar Zar Moe 29 April 2015 (has links)
Moisture-induced damage is one the major causes of deterioration of asphalt pavements and extensive research has been conducted on this topic. Theoretical and experimental results have led the researchers to believe that moisture-induced damages are caused mainly by the generation of pore water pressure in asphalt mixtures when traffic passes over a pavement. The Moisture Induced Sensitivity Tester (MIST) has been recently developed to simulate the phenomenon of repeated pore pressure generation and deterioration in the laboratory. The objective of this study was to evaluate moisture-induced damage in typical Maine Department of Transportation (DOT) asphalt mixes, with the use of MIST, pre and post testing, and analysis of data. The MIST was used to condition Hot Mix Asphalt (HMA) samples that were compacted from eight typical Maine DOT mixes, with different types of aggregates and asphalt binder. A modified Dynamic modulus test in Indirect Tensile Mode was used for the determination of damage. A layered elastic model, along with a fatigue-cracking criterion, was utilized to assess the total impact on the pavement lives. Monte Carlo analysis was conducted to determine the distribution of number of repetitions to failure of pavements that are subjected to moisture damage. The major conclusions are that most of the mixes are likely to experience a reduction in their life due to the effect of moisture and that the Micro-Deval and the fine aggregate absorption test results can be related to such damage. A composite factor, consisting of both of these test results, is recommended for regular use by the DOT to screen mixes with high moisture damage potential.
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Revamping aggregate property requirements for portland cement concreteStutts, Zachary William 18 June 2012 (has links)
Current Texas Department of Transportation (TxDOT) procedures for evaluating coarse aggregate for portland cement concrete (PCC) have been in place for over 39 years. Item 421 in the TxDOT "Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges" describes the tests and test limits that must be met by aggregates before they can be approved for use in portland cement concrete applications. The intention of Item 421 is to ensure that only strong, durable aggregates are used in concrete so that the life of concrete is not cut short by common distress mechanisms which ultimately lead to costly repairs and replacements. The two main tests currently used by TxDOT to evaluate aggregates are the magnesium sulfate soundness test and the Los Angeles abrasion and impact test. These tests are meant to characterize the overall soundness and resistance to abrasion and impact of an aggregate respectively. Unfortunately, past research has shown that the magnesium sulfate soundness and test and the Los Angeles abrasion and impact test are not able to successfully predict the field performance of an aggregate in concrete. The requirements of item 421 have thus far done a reasonably good job of ensuring long-lasting concrete; however the current tests and test limits may be unnecessarily precluding the use of some local materials. As high quality aggregate sources are depleted and transportation costs increase, it will become more necessary to distinguish good performers from marginal and poor performers in the future. If aggregate tests can be found that demonstrate better correlations with field performance, it may be possible to use more local aggregate sources and still provide the desired level of reliability for pavements, bridges, and other TxDOT concrete applications. Researchers are in the processing of collecting coarse and fine aggregates commonly used in Texas and testing these aggregates on a variety of alternative tests. Researchers will attempt to relate this test data to concrete behavior and ultimately recommend tests for improved TxDOT aggregate specifications. / text
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Étude de la durabilité à l'écaillage en présence de sel fondant des bétons avec liant ternaireMorin-Morissette, Pierre-Olivier January 2017 (has links)
L’écaillage de la surface du béton dû aux sels fondants est un phénomène dont les mécanismes sont relativement peu connus. Plusieurs publications et plusieurs recherches se sont penchées sur cette problématique de durabilité du béton. Encore aujourd’hui, aucune théorie prise individuellement ne permet d’expliquer entièrement les causes de ce phénomène et le rôle protecteur d’un bon réseau de bulle d’air sur les bétons qui sont dans des conditions à risque.
À prime à bord, les tests sous leur forme actuelle, peuvent sembler moins bien adaptés lorsque l’utilisation de liant ternaire est préférée au liant avec seulement du ciment Portland. Cette recherche s'intéresse donc à valider la sévérité du test d’écaillage BNQ 2621-905 lorsqu’on utilise des liants ternaires. Ce projet se penche également sur l’effet du type et la durée de la cure, du type de superplastifiant utilisé, de la variation du L ̅ et de l’utilisation d’un granulat marginal sur les résistances à l’écaillage des bétons avec liant ternaire.
Les travaux réalisés dans le cadre de ce projet démontrent qu’il est possible d’avoir des résultats qui satisfont la norme d’écaillage BNQ 2621-905 avec des paramètres de formulations d’un béton de type V-S avec presque tous les liants ternaires utilisés. De plus, lorsque le réseau d’air est de bonne qualité (L ̅ < 230 µm) l’utilisation de superplastifiant PCP ou PNS ne semble pas d’avoir d’effet marqué. Le facteur d’espacement, actuellement prescrit dans la norme CSA A23.1, moyen inférieur à 230 µm avec aucune valeur dépassant 260 µm permet d’obtenir de bons résultats à l’écaillage en laboratoire pour le liant C. Finalement, l’utilisation d’un granulat marginal au micro-Deval peut avoir un effet sur la quantité de débris de surface d’un échantillon soumis au gel-dégel.
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Samband mellan geologiska och bergmekaniska egenskaper i bergmaterial som bärlager till riksväg 51 : Riksväg 51 sträckan Svennevad - KvarntorpskorsetLandeman, Philip January 2018 (has links)
This thesis was created to ensure the quality of the rock which would be crushed to base layer construction material, in a road cut at Swedish highway 51, and to find a possible link between the rock's abrasion resistance and its mineralogy. Rock samples were collected, and among other things, several ball mill tests were carried out. The design of the road project was carried out by Loxia Group AB with NCC Group as contractor.A total of 18 rock samples and 2 base layer samples were taken in the area and they were all tested in a ball mill. The results showed that of the 18 rock samples, 2 samples had a ball mill value of less than 16 on the scale, 10 samples had values from 16 to 20, in addition to this, 3 samples had values from 20 to 21 and 3 samples had values in excess of 21 on the Swedish ball mill scale.Of the 3 samples with a ball mill value higher than 21, all contained a larger amount of biotite. Biotite did not appear to the same extent among the samples that ended up further down the ball mill scale. This link was so clear that a conclusion was subsequently drawn from this. The samples taken on the prefabricated base layer both had a ball mill value between 16 and 20. Overall, both the base layer and the rock material passed the Swedish Government’s Transport Administration’s requirements according to "TRVKB 10, Obundna lager". The rock type that was on the south part of the rock cut, adjacent to a deformation zone, had way too poor quality to undergo a ball mill test and therefore there are no values taken from that area.The conclusion of the work is that the rock material overall meets the Swedish Government’s Transport Administration’s requirements for base layer construction materials according to "TRVKB 10 Obundna lager", that a clear link between the proportion of biotite in a rock material and its abrasion resistance exists, and that the broken rock in the south should not be used as construction materials since the rock has insufficient mechanic capacity.
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