42 research outputs found
Tyre - Road Noise, Surface Characteristics and Material Properties
No full textNoise levels due to road traffic have reached intolerable high levels in and around many urban areas all around the world. Because of health reasons and reasons of well- being these noise levels have to be reduced. The noise produced from the interaction between the rolling tyre and road surface is one of the most important contributions in the overall traffic noise. Therefore solutions for noise level reduction have to be found in that interface. A noise reducing pavement is considered as an effective way to reduce the tyre - road noise from the source where it generates. Towards further understanding and improvement of the noise reduction ability of pavements, research was carried out in this PhD thesis to determine the relationship between the road material properties, surface characteristics and the noise levels, and to develop models which can be used for guiding the design of noise reducing pavements. As one of existing road surfaces, the thin layer surfacing eliminates the tyre - road noise by combining a small surface texture and a high porosity. In recent years, it became popular for using it on urban and provincial road sections in the Netherlands and some other European countries. Replacing porous asphalt with thin layer surfacings on highways is also considered an option in the Netherlands. As there are limited investigations on the relation between tyre - road noise and the influencing parameters for this type of surface, the research in this thesis focuses on thin layer surfacings. The study starts with a review of existing researches on tyre - road noise. It provides basic knowledge about tyre - road noise and the influencing parameters related to the road surface. The related measurement methods and models developed were summarized. Comments were made on these existing studies and the shortcomings were pointed out. A research plan was then proposed based on the comments of the current researches and aiming for improving the existing knowledge of tyre - road noise on thin layer surfacings. Measurements were carried out for investigating the influence of mixture compositions on surface characteristics. Both laboratory and in-situ measurements were involved. In the laboratory tests, thin layer surfacing samples with different mixture compositions were designed and produced; core samples were also used which were drilled from trial road sections in the Netherlands. The surface characteristics studied included: surface texture, sound absorption, mechanical impedance and stiffness. Methods for testing the surface characteristics and mixture compositions were discussed. Experimental work was also undertaken for developing new methods in testing the surface characteristics. A contribution of this thesis to tyre - road noise related measurement is the application of a new type of technology for measuring the sound absorption of a road surface. It is based on testing the sound pressure and sound particle velocity close to the sample surface. According to the analysis of the test results, this measurement method proved to provide reliable results of sound absorption for road surface samples. Furthermore, suggestions were given for the application of the method in road engineering measurements. Surface characteristics and mixture compositions of thin layer surfacings were then measured. The influence of the material properties on surface characteristics, including texture, sound absorption, mechanical impedance and stiffness, were observed based by comparing test results obtained on materials with different mixture compositions. Moreover, in the study, the degree of connectivity of air voids in the road surface sample was determined. A relationship between the mechanical impedance and stiffness of road surface material was also developed. Comments were given for noise reduction by taking into account the mechanical impedance of road surfaces. The investigation of the effect of surface characteristics on tyre - road noise was performed by means of statistical analyses. Data used in the analysis were from thin layer surfacing sections in the Netherlands. The two important surface characteristics, surface texture and sound absorption were taken in to account. Correlation analysis and linear regression analysis were adopted for observing the relationship between the surface characteristics and noise levels. The individual effect of a certain surface characteristic can be reflected by the regression equations. Furthermore, the influence of driving speed of the vehicle, the tyre types and small changes of surface characteristics were also discussed. In the end, a model which predicts the tyre - road noise levels for thin layer surfacings was developed. The model was built by means of regression analysis by using the data from the laboratory measurements and an existing database. With the model, noise levels can be predicted using a small number of input parameters of material properties or surface characteristics. The model was validated by using data from in service thin layer road surfaces. The model can be used for predicting noise levels and helps to improve the design of noise reducing surfaces.Structural EngineeringCivil Engineering and Geoscience
Permanent deformation of asphalt mixes
No full textThis dissertation describes the results of a research that was conducted on the permanent deformation of asphalt mixtures. Central to this research was the separate characterization of the contribution of the aggregate skeleton and the bituminous mortar towards resistance to permanent deformation. The mixtures considered in this research included porous asphalt, stone mastic asphalt and dense asphalt concrete. The test program comprised of modulus testing as well as monotonic tension and compression tests on the asphalt mixtures, monotonic and repeated load triaxial tests on the aggregate skeletons along with dynamic shear and direct tension tests on the bitumen and the bituminous mortar. Prior to testing, the compaction homogeneity of the aggregate skeleton and asphalt mixture specimens was examined by means of X-ray tomography. The repeated load triaxial tests conducted on the aggregate skeleton included constant and cyclic confinement tests. The cyclic confinement tests offered a more realistic means of characterizing the permanent deformation behaviour of the aggregate skeleton in comparison to the constant confinement tests. In addition, the permanent deformation under cyclic confinement was higher than the permanent deformation under constant confinement. The approach developed in this research was based on the Desai plasticity model. In order to demonstrate the practical implications of this plasticity approach, two test pavements with a significant amount of permanent deformation were analysed. The analyses showed that the observed permanent deformation could be explained by the approach developed in this research.Civil Engineering and Geoscience
Hot Mix Asphalt Recycling: Practices and Principles
No full textHot mix asphalt recycling has become common practice all over the world since the 1970s because of the crisis in oil prices. In the Netherlands, hot recycling has advanced to such an extent that in most of the mixtures more than 50% of reclaimed asphalt (RA) is allowed. These mixtures with such a high RA content are produced in a batch plant to which a parallel drum is attached. In this drum RA is pre-heated to approximately 130°C. Since 2007 another hot mix recycling techniques became available in which RA is mixed in cold and moist condition in contrary to conventional methods. It is a so called double barrel drum mixer. In this method virgin aggregates are superheated in the inner drum and mixed with cool and moist RA and fines and virgin bitumen in the outer drum. In both cases, double drum and partial heating methods, the virgin aggregates have to be pre-heated to higher temperatures than with mixtures without RA in order to achieve a mixing temperature of around 170°C. Dependent on RA amount, moisture, pre-heating, etc. in the batch plant the virgin aggregates have to be pre-heated to around 300° C and in the double barrel drum to around 500°C. These high temperatures have led to concerns about the quality of the produced mixtures. Since 2008, a new Dutch specification system for asphalt mixtures is in place in line with the European standards (EN13108 series). The new regulation gives contractors freedom to select their own material such as bitumen grade and the amount of recycling; however, in return it makes them responsible for the quality of the mixture. The mixture should fulfill the requirement of fundamental performance characteristics of the mixtures such as resistance to fatigue and permanent deformation. In this research two major questions have been investigated. One of the questions is whether these high temperatures have a negative effect on the bituminous binder, while the other important question is whether the RA binder will blend totally with the virgin binder that is added. The focus of this research was on four objectives. The first objective was to develop a laboratory mixing method to simulate the real recycling process in the field. The second objective was to assess the effect of the double barrel drum on the mixture quality in comparison with conventional batch plant. Third, it was aimed to measure the blending degree between two binders. And finally, to increase the understanding of the mechanism behind blending RA binders with virgin bitumen, with focus on their micro structure. To cover all research topics, this dissertation is organized in two parts in which the first part is devoted to laboratory and field mixture evaluation while the second part is presenting the exploratory research on the fundamental aspects of blending. Research in part 1 is conducted in two phases, laboratory simulation and field experimentation. The conventional partial warming recycling method (PW) the upgraded double drum mixing method (UPG) were simulated in the lab and the quality of mixtures were compared with the standard mixing method (SM) in the lab at different RA content and different moisture content. This research showed that higher percentages of RA results in higher stiffness and lower fatigue life. However in the UPG method with 4% moisture and 60% RA, the mixture became remarkably lower in stiffness and durable against fatigue. This might be because of the lack of blending or the effect of foaming of bitumen. It was concluded that the UPG method could not effectively be simulated in the lab. In the next experimental phase of the study, three identical mixtures were produced with 50% RA and 4.3% bitumen. One mixture was produced in a batch plant (BB) while the second one was mixed using a double drum mixer by the same contractor (A). The third mixture was produced in the laboratory (L) using a lab pugmill mixer. The comparison between three mixtures shows that mixture L has a higher stiffness than A and BB. Mixture BB has as slightly higher stiffness than A. Furthermore, mixture A has the lowest stiffness which is most probably due to the system of cold and moist RA feeding into the double drum system. Besides the 4PB fatigue and stiffness test, monotonic uniaxial tension (UT) and compression (UC) tests were performed to be used in material modeling and to determine a fatigue endurance limit. The limit value of the stress ratio parameter (Rlimit) was determined which is useful in the determination of the endurance limit in a three-dimensional state. It shows that different mixing methods lead to different endurance limits. It turns out that the plant produced mixture has a higher endurance limit than the laboratory mixture. In this research an infrared thermography method was used in every material preparation stage. The temperature homogeneity of the mixtures in the lab and in the field was investigated. It proved to be a useful method in visualizing the temperature exchange during mixing and compaction. In Part 2, the effect of superheating aggregates is studied by simulating RA and real aggregates with glass beads and artificial aged binder. The stage extraction method was evaluated in this research with respect to size and shape of aggregates. The blending and diffusion mechanism between old and new bitumen is studied at the microstructure level by means of Nano indention and Nano-CT scanning. The morphology of different types of bitumen was detectable by these techniques; however the blending zone couldn’t be characterized.Structural EngineeringCivil Engineering and Geoscience
Duurzaamheid van Elastocoast
No full textIn dit onderzoek is een voorzet gemaakt voor een sterktebeproeving van verouderd Elastocoast door middel van cilindrische proefstukken. Daarnaast is een vervolgevaluatie gemaakt van de proefvakken bij Petten en Zuidbout, alsmede een eerste evaluatie van het productievak Elastocoast bij Bath langs de Oosterschelde.Hydraulic EngineeringCivil Engineering and Geoscience
Analysis of wave impact on the elastocoast system
No full textThe elastocoast system can be used as an armour layer on revetments. The bonding system exists of a mix of crushed stones and 2-component polyurethane. This bonding system creates bonding forces between the stones and an open (porous) structure can be obtained. Elastocoast is developed by Elastogran GmbH, a BASF subsidiary. The response of an elastocoast layer which is placed directly (without a filter layer) on a geotextile and sand foundation is analyzed in this study from several tests executed in the Large Wave Channel in Hannover. The stiffness of an elastocoast beam is determined in a three point bending test with a dynamic load. The indirect tensile splitting strength and compression strength is determined from several cubes. A model in which the dynamic load of a wave impact event is created (a finite element method program, Plaxis v8, is used) and adapted with the results of all analyzed experiments. The resulting behaviour of the elastocoast layer around the wave impact was predicted according to this model for two cases. First, the elastocoast layer is supported on the foundation over the total length of the layer. Secondly, in case of a gap was formed around the wave impact point in the foundation under the elastocoast layer. The amount and type of the used polyurethaan determines the stiffness of an elastocoast layer. The amount of used polyurethaan increases when an elastocoast beam or cube is formed in a closed framework compared to an layer which of formed on a revetment. The resulting maximum pressure during a wave impact event on top of the elastocoast reduces due to the open structure of elastocoast. The maximum stress inside the elastocoast layer increases significantly when a gap in the foundation is formed. Maximum allowed gap width values in combination with different (regular) wave conditions are shown in several figures in order to avoid breaking of the elastocoast layer due to a wave impact event. The eigen frequency of the elastocoast layer is determined from the vibrations of the layer after each wave impact event. High stresses inside the layer can be expected if it is loaded around the eigen frequency. A static schematization (without dynamic effects) as used in the program GOLFKLAP should not be used in order to determine the maximum stress (or minimum required layer thickness in order to avoid breaking of the layer) inside the elastocoast layer (without a filter layer between the geotextile and elastocoast layer). It is recommended to execute more experiments in order to determine the stiffness and tensile flexural strength from an elastocoast beam with different type and amount of used polyurethaan and with different type and grading crushed stones.Hydraulic EngineeringCivil Engineering and Geoscience
Experiment analysis: The relation between wave loading and resulting strain in an asphaltic concrete
No full textIn the year 1991 the Technical Advisory Commission (TAW-A4) ordered a full scale investigation on wave impacts on an asphaltic concrete revetment. The goal of the experiment was to gain insight into the mechanisms which would lead to failure, cracking of the revetment. Also the behaviour of the revetment after failure (residual strength) was studied. To gain insight in the behaviour of the revetment, strain measuring devices and pressure transducers were placed into the revetment. The measured strains were compared with calculated strains by several researchers. One of the researchers concluded there was almost no resemblance between the measured and calculated strain and recommended to perform a sensitivity analysis on the calculations. This conclusion and recommendation is what resulted into the subject of the thesis. Due to extensive testing of materials in the last fifteen years a better understanding of material behaviour is achieved. This concerns in particular the modulus of elasticity of asphaltic concrete and the modulus of subgrade reaction. This knowledge is used in the thesis to get new results, by recalculation, from the same model. To perform a sensitivity analysis a stochastic simulation is used. A choice is made for using the Monte Carlo method for simulation of the strains and the results of the simulations are compared with the measured strains. The conclusions are divided into conclusions regarding the recalculation and conclusions regarding the Monte Carlo simulation. In the recalculation a better agreement between the measured and calculated strain is obtained. The model describes the calculated dynamic strain in a good way. This is also concluded by Ruygrok, one of the researchers who also investigated this Delta flume experiment. The simulated strains calculated with the Monte Carlo method are not in agreement with the measured strains. The difference between the calculation and the measurements are assigned to the differences between the quasi-static and the dynamic strain. Another reason for the differences is that the information of the wave impacts stored in the impact factor distribution cannot be divided into time and space, which leads to a too rough approach in the simulation.It is recommended to investigate the relation between the quasi-static or dynamic strain with the total strain. If the quasi-static strain adds extra damage to the revetment this part should be taken into account when a safety assessment is performed.Civil Engineering and Geoscience
Determination of mechanical properties of hydraulic asphaltic concrete by means of a three-point bending test
No full textTAW A4 Asfalttoepassinge
Invloed van kruip op het vermoeiingsgedrag in de driepuntsbuigproef (Paper Wegbouwkundige werkdagen)
No full textIn de nieuwe wet op de waterkeringen moet de beheerder van een zeedijk iedere 5 jaar een uitspraak doen over de veiligheid van zijn dijk. Het betreft dan het kunnen doorstaan van een zogenaamde superstorm. Met de aktuele vermoeiingseigenschappen van het asfalt wordt berekend of de bekleding een superstorm kan doorstaan. De vermoeiingseigenschappen aan materiaal uit de dijk worden in een driepuntsbuigopstelling bepaald. Een bijkomend effekt tijdens de als sprongbelasting uitgevoerde proeven, de permanente doorbuiging, wordt in deze paper nader beschouwd. Aangegeven wordt wat de invloed op de vermoeiingslijnen kan zijn, afhankelijk van temperatuur, frekwentie en belastingstijd.TAW A4 Asfalttoepassinge
Structural Analysis of Polyurethane Bonded Aggregate on Block Revetments
No full textFor centuries dikes in the Netherlands have been protected against wave attack by revetments constructed of pitched blocks. Due to new insights into the behaviour of pitched blocks and increased hydraulic boundary conditions, a significant part of those dikes does not meet the current prescribed standards and safety norms anymore. As a result, large parts have to be reinforced in the coming years. The main failure mechanism of a placed block revetment is uplifting due to water overpressures. This happens when the upward pressures, caused by a hydraulic head difference over the revetment, exceed the dead weight of the structure. The concrete elements are lifted up and the waves subsequently induce erosion of the dike body. Therefore, the renovation of these revetments is currently done by adding more weight to the structure by covering the block revetment with large rocks, or even completely replacing the elements by bigger concrete blocks. In view of the large renovation areas, replacing the concrete elements is a time consuming process and will require considerable financial efforts. Therefore, innovative refurbishment techniques are desired and researched. A relatively new type of revetment is the polyurethane bonded aggregate (PBA) which consists of aggregate glued by the adhesive polyurethane (PU) and is currently marketed under the brand name Elastocoast. This study focuses on the use of PBA in strengthening pitched stone revetments. In this report an effort is made to describe the mechanical behaviour of refurbished block revetments under wave loading. A PBA refurbishment layer adds coherence to the revetment and will prevent the blocks from uplifting. Another notable advantage is its high permeability. Firstly, an analytical model was elaborated to gain a first general insight into the structural behaviour of a composite PBA/block revetment. In the analytical model, the interaction and stress distribution between the revetment and subsoil were modelled as an elastically supported beam (Winkler model). Furthermore the structure was modelled with a finite element package. Although this research is based on multiple assumptions, it is possible to formulate some qualitative statements that resulted from this study. \u95 The findings suggest that a rigid connection between the PBA layer and the existing block revetment is most effective in reducing the bending stresses in the PBA layer. \u95 The results of this study support furthermore the idea that the composite PBA/block revetment could be schematized as an Euler Bernoulli bending beam. \u95 The findings also indicate that the current design method is conservative. In this design method it is assumed that only the PBA cover layer contributes to the flexural strength of the structure. The results of this thesis indicate that this design approach is conservative and therefore resulting in thick PBA layers. \u95 Lastly, two conventional refurbishment techniques (Open Stone Asphalt (OSA) and hydraulic asphalt concrete) were compared with the PBA. Calculations were performed what the most effective approach would be. On the one hand, an impermeable cover layer constructed by asphalt concrete resulting in higher water pressures but increasing its dead weight (asphalt concrete), or on the other hand, applying a permeable refurbishment layer (PBA and OSA) which is less heavy but resulting in lower water overpressures. The results suggest that it is more effective to use a less heavier but more permeable material as a refurbishment than the other way around. It must be noted that this greatly depends of its permeability. If its leakage length is increased by clogging or when applying the refurbished material, it results in a significant increase of the maximum bending stresses. In this case the refurbishment techniques with asphalt concrete becomes more effective since it is heavier.Structural EngineeringHydraulic EngineeringCivil Engineering and Geoscience
Burostudie naar de draagkracht van de ondergrond
No full text1. Inleiding 2. Principe berekening met GOLFKLAP 3. Literatuur 4. Voorstel procedure beddingsconstante uit literatuur en expert opinion 5. Rapporten NPC en bestaande procedure. 6 Vergelijking voorstel met bestaande procedure. 7. Conclusies en aanbevelingen Literatuurlijst BIJLAGE 1. Globale analyse beddingsconstante uit [2] BIJLAGE 2. Gevoeligheidsanalyse GOLFKLAP BIJLAGE 3. DCP proef: korte impressieAsfaltbekledinge
