Determination of Dynamic Modulus of Cold In-place Recycling Mixtures with Foamed Asphalt

김용주,이호신 한국도로학회 2009 한국도로학회논문집 Vol.11 No.1

A new mix design procedure for cold in-place recycling using foamed asphalt (CIR-foam) has been developed for Iowa Department of Transportation. Some strengths and weaknesses of the new mix design parameters were considered and modified to improve the laboratory test procedure. Based on the critical mixture parameters identified, a new mix design procedure was developed and validated to establish the properties of the CIR-foam mixtures. As part of the validation effort to evaluate a new CIR-foam mix design procedure, dynamic moduli of CIR-foam mixtures made of seven different reclaimed asphalt pavement (RAP) materials collected throughout the state of Iowa were measured and their master curves were constructed. The main objectives of this study are to provide: 1) standardized testing procedure for measuring the dynamic modulus of CIR-foam mixtures using new simple performance testing (SPT) equipment; 2) analysis procedure for constructing the master curves for a wide range of RAP materials; and 3) impacts of RAP material characteristics on the dynamic modulus. Dynamic moduli were measured at three different temperatures and six different loading frequencies and they were consistent among different RAP sources. Master curves were then constructed for the CIR-foam mixtures using seven different RAP materials. Based upon the observation of the constructed master curves, dynamic moduli of CIR-foam mixtures were less sensitive to the loading frequencies than HMA mixtures. It can be concluded that at the low temperature, the dynamic modulus is affected by the amount of fines in the RAP materials whereas, at the high temperature, the dynamic modulus is influenced by the residual binder characteristics. A new mix design procedure for cold in-place recycling using foamed asphalt (CIR-foam) has been developed for Iowa Department of Transportation. Some strengths and weaknesses of the new mix design parameters were considered and modified to improve the laboratory test procedure. Based on the critical mixture parameters identified, a new mix design procedure was developed and validated to establish the properties of the CIR-foam mixtures. As part of the validation effort to evaluate a new CIR-foam mix design procedure, dynamic moduli of CIR-foam mixtures made of seven different reclaimed asphalt pavement (RAP) materials collected throughout the state of Iowa were measured and their master curves were constructed. The main objectives of this study are to provide: 1) standardized testing procedure for measuring the dynamic modulus of CIR-foam mixtures using new simple performance testing (SPT) equipment; 2) analysis procedure for constructing the master curves for a wide range of RAP materials; and 3) impacts of RAP material characteristics on the dynamic modulus. Dynamic moduli were measured at three different temperatures and six different loading frequencies and they were consistent among different RAP sources. Master curves were then constructed for the CIR-foam mixtures using seven different RAP materials. Based upon the observation of the constructed master curves, dynamic moduli of CIR-foam mixtures were less sensitive to the loading frequencies than HMA mixtures. It can be concluded that at the low temperature, the dynamic modulus is affected by the amount of fines in the RAP materials whereas, at the high temperature, the dynamic modulus is influenced by the residual binder characteristics.

공용중인 아스팔트 포장의 아스팔트층 동탄성계수와 FWD 역산 탄성계수의 상관관계 분석

박희문(Park, Hee Mun),박홍준(Park, Hong Joon) 한국도로학회 2015 한국도로학회논문집 Vol.17 No.5

PURPOSES: The objective of this study is to analyze the relationship between the FWD back-calculated modulus and dynamic modulus of asphalt layers for existing asphalt pavements. METHODS: To evaluate the dynamic modulus of the asphalt mixture in the existing and new asphalt layers, the uniaxial direct tension test was conducted on small asphalt specimens obtained from the existing asphalt-covered pavements. A dynamic modulus master curve was estimated by using the uniaxial direct tension test for each asphalt layer. The falling weight deflectometer (FWD) testing was conducted on the test sections, and the modulus values of pavement layers were back-calculated using the genetic algorithm and the finite element method based back-calculation program. The relationship between measured and back-calculated asphalt layer moduli was examined in this study. The normalized dynamic modulus was adopted to predict the stiffness characteristics of asphalt layers more accurately. RESULTS: From this study, we can conclude that there is no close relationship between dynamic modulus of first layer and back-calculated asphalt modulus. The dynamic moduli of second and third asphalt layers have some relation with asphalt stiffness. Test results also showed that the normalized dynamic modulus of the asphalt mixture is closely related to the FWD back-calculated modulus with 0.73 of R square value. CONCLUSIONS: The back-calculated modulus of asphalt layer can be used as an indicator of the stiffness characteristics of asphalt layers in the asphalt-covered pavements.

A multistep methodology based on developed Takayanagi, Paul and Ouali models for tensile modulus of polymer/carbon nanotubes nanocomposites above percolation threshold assuming the contribution of interphase regions

Jamalzadeh, Navid,Heidary, Sahar,Zare, Yasser,Rhee, Kyong Yop Elsevier 2018 POLYMER TESTING -LONDON- Vol.69 No.-

<P><B>Abstract</B></P> <P>In this study, a multi-step technique is suggested to estimate the tensile modulus of polymer/carbon nanotubes (CNT) nanocomposites (PCNT) assuming the percolating effect of interphase regions. At the first step, Paul model calculates the modulus of regions containing dispersed nanoparticles and surrounding interphase. Secondly, the modulus of interphase-networked CNT is predicted by Ouali model. Finally, the developed Takayanagi model estimates the modulus of PCNT using the moduli of supposed regions. Additionally, some parameters such as the fraction of nanoparticles in the network (f) and the percolation threshold of interphase regions are formulated. The predicted modulus shows good agreement with the experimental results of samples. The thinnest and the longest CNT as well as the thickest and the strongest interphase cause the highest modulus. However, the interphase properties more significantly affect the modulus compared to material characteristics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A multi-step technique is suggested for tensile modulus of polymer/CNT nanocomposites. </LI> <LI> Paul model predicts the modulus of the regions containing dispersed CNT and interphase. </LI> <LI> Ouali model calculates the modulus of the networked CNT and surrounding interphase. </LI> <LI> The developed Takayanagi model estimates the modulus of nanocomposite. </LI> <LI> The predicted modulus shows fine agreement with the experimental results of some samples. </LI> </UL> </P>

실내 및 현장실험을 통한 DCPT의 노상토 다짐관리기준 정립에 관한 기초연구

최준성 한국도로학회 2008 한국도로학회논문집 Vol.10 No.4

In this study, in-situ testing method, Dynamic Cone Penetration Test(DCPT) was presented to establish a new compaction control criteria with using mechanical property like elastic modulus instead of unit weight for field compaction control. Soil chamber tests and in-situ tests were carried out to confirm DCPT tests can predict the designed elastic modulus after field compaction, and correlation analysis among the DCPT, CBR and resilient modulus of subgrade were performed. Also, DCPT test spacing criteria in the construction site was proposed from the literature review. In the result of laboratory tests, Livneh's equation was the best in correlation between PR of DCPT and CBR, George and Pradesh's equation was the best in the predicted resilient modulus. In the resilient modulus using FWD, Gudishala's equation estimates little larger than predicted resilient modulus and Chen's equation estimates little smaller. And KICT's equation estimates the modulus smaller than predicted resilient modulus. But using the results of laboratory resilient modulus tests considering the deviatoric and confining stress from the moving vehicle, the KICT's equation was the best. In the results of In-situ DCPT tests, the variation of PR can occur according to size distribution of penetrate points. So DCPT test spacing was proposed to reduce the difference of PR. Also it was shows that average PR was different according to subgrade materials although the subgrade was satisfied the degree of compaction. Especially large sized materials show smaller PR, and it is also found that field water contents have influence a lot of degree of compaction but a little on the average PR of the DCPT tests. In this study, in-situ testing method, Dynamic Cone Penetration Test(DCPT) was presented to establish a new compaction control criteria with using mechanical property like elastic modulus instead of unit weight for field compaction control. Soil chamber tests and in-situ tests were carried out to confirm DCPT tests can predict the designed elastic modulus after field compaction, and correlation analysis among the DCPT, CBR and resilient modulus of subgrade were performed. Also, DCPT test spacing criteria in the construction site was proposed from the literature review. In the result of laboratory tests, Livneh's equation was the best in correlation between PR of DCPT and CBR, George and Pradesh's equation was the best in the predicted resilient modulus. In the resilient modulus using FWD, Gudishala's equation estimates little larger than predicted resilient modulus and Chen's equation estimates little smaller. And KICT's equation estimates the modulus smaller than predicted resilient modulus. But using the results of laboratory resilient modulus tests considering the deviatoric and confining stress from the moving vehicle, the KICT's equation was the best. In the results of In-situ DCPT tests, the variation of PR can occur according to size distribution of penetrate points. So DCPT test spacing was proposed to reduce the difference of PR. Also it was shows that average PR was different according to subgrade materials although the subgrade was satisfied the degree of compaction. Especially large sized materials show smaller PR, and it is also found that field water contents have influence a lot of degree of compaction but a little on the average PR of the DCPT tests.

심층혼합 시료의 탄성계수에 관한 실험적 연구

박춘식,박환기 한국지반공학회 2018 한국지반공학회논문집 Vol.34 No.10

In this study, aimed at determining the elastic modulus of deep mixed samples, 320 test specimens were developed by mixing 8%, 10%, 12%, and 14% of stabilizer mixture in the granular conditions of clay, sand and gravel. Uniaxial compression tests were carried out using these specimens, and the uniaxial compression strength and strain were analyzed to determine the secant elastic modulus and tangent elastic modulus. Laboratory test results showed that the uniaxial compression strength of all deep mixed samples increased with increasing curing time and stabilizer mixing ratio, and that the secant elastic modulus and the tangen elastic modulus also increased. The increase of the elastic modulus according to the curing period turned out greater in the tangent elastic modulus than in the secant elastic modulus. In order to measure elastic modulus with changes in stabilizer mixing ratio, the correlation coefficient between the elastic modulus for stabilizer mixing ratio of 8% and that of 10%, 12% and 14% was calculated respectively by the specimen condition. The elastic modulus tended to increase as the grain size in a deep mixed specimen increased. The distribution of grain size that had the greatest effect appeared when the composition ratio of sand was high. On the other hand, the increase in the elastic modulus was larger in the sand specimens than in the clay and gravel specimens. Based on these results, it is suggested that a pertinent soil parameter of the deep mixed ground in the field may be obtained by the particle size distribution and the mixing ratio of stabilizer of the deep mixed soil.

Adaptive Modulus와 Adaptive Stepsize를 이용한 CR-MMA 적응 등화 알고리즘의 성능 개선

임승각 한국인터넷방송통신학회 2019 한국인터넷방송통신학회 논문지 Vol.19 No.5

This paper proposes the Hybrid-CRMMA adaptive equalization algorithm that is possible to improves the performance of CR-MMA based on adaptive modulus and adaptive stepsize. The 16-QAM nonconstant modulus signal is reduced to 4-QAM constant modulus signal, and the error signal were obtained based on the fixed statistic modulus of transmitted signal. It is possible to improving the currently MMA adaptive equalization performance. The proposed Hybrid-CRMMA composed of adaptive modulus which is propotional to the power of equalizer output and adaptive stepsize which is function of the nonlinearties of error signal, and its improved equalization performance were confirmed by computer simulation. For this purpose, the output signal constellation, the residual isi and maximum distortion and MSE that is for the convergence characteristics, the SER that is meaning the robustness of external noise of algorithm were used. As a result of computer simulation, it was confirmed that the proposed Hybrid-CRMMA has more superior performance in every index compared to currently CR-MMA. 본 논문에서는 CR-MMA (Constellation Reduction-Multi Modulus Algorithm) 등화 알고리즘에 adaptive modulus와 adaptive stepsize를 적용하므로서 등화 성능을 개선할 수 있는 Hybrid-CRMMA 알고리즘을 제안한다. CR-MMA 알고리즘은 16-QAM과 같은 nonconstant modulus 신호를 constant modulus 신호로 reduction한 후, 송신 신호의 통계치인 고정 modulus를 이용하여 오차 신호를 발생하므로 기존 MMA의 적응 등화 성능을 개선시키기위하여 등장하였다. 제안 방식인 Hybrid-CRMMA는 CR-MMA의 constellation reduction 개념에 등화기 출력 신호의 전력에 비례토록 adaptive modulus와 오차 신호의 비선형성을 이용하여 adaptive stepsize를 적용하였으며, 이의개선된 등화 성능을 컴퓨터 시뮬레이션을 통해 확인한다. 이를 위한 성능 지수로는 등화기 출력 신호 성상도, 수렴 특성을 나타내는 잔류 isi, 최대 찌그러짐, MSE 및 알고리즘의 외부 잡음에 대한 강인성을 나타내는 SER을 사용하였다. 컴퓨터 시뮬레이션 결과 제안 Hybrid-CRMMA가 기존 CR-MMA보다 모든 성능 지수에서 우월함을 확인하였다.

탄소섬유 복합재의 Bi-modulus 특성을 반영한 풍력 터빈 블레이드 구조해석

주근수,문진범,김시현,강민규,김지훈 한국풍력에너지학회 2022 풍력에너지저널 Vol.13 No.3

This paper deals with the structural analysis of wind turbine blades considering the bi-modulus property of CFRP, known as a more economic and efficient material for very large blades. The bi-modulus property is an unique characteristic of CFRP that shows higher tensile modulus than compressive modulus. Due to this characteristic, it is needed to apply the bi-modulus property to the computational analysis of CFRP blades to achieve more accurate results. In this paper, a novel method is proposed to apply the bi-modulus property of CFRP in a numerical simulation. To demonstrate the bi-modulus effect in FE analysis, the actual bi-modulus of CFRP was measured and applied to the structural analysis of a wind turbine blade. Moreover, the effects of the proposed method were evaluated by comparing the analysis results with actual full-scale blade static test results. As a result, it was verified that the proposed method could appropriately simulate the bi-modulus during FE analysis. Moreover, the accuracy of blade structural analysis was improved in accordance with the application of the bi-modulus property.

Experimental Study on SAFETY Estimation of Subgrade Modulus of In-Service Ballasted Tracks in KOREA

Choi Jung youl,Chung Jee seung J-INSTITUTE 2018 International Journal of Crisis & Safety Vol.3 No.2

The subgrade modulus is an important parameter in the railway safety and the analysis of the behavior of a ballasted track. However, because such analyses often use the design subgrade moduli, their results seldom agree with those of finite element(FE) analyses, which use the theoretically determined subgrade moduli. Moreover, it is difficult to experimentally determine the subgrade modulus and spring stiffness of an in-service track because track components such as the ballast, sleepers, and rails are installed over the subgrade. In this study, the subgrade modulus of an in-service ballasted track was estimated by measuring the dynamic response of the track for railway safety. The subgrade modulus was further predicted from a proposed subgrade modulus map developed from the results of field tests and empirical equations for comparison with the design value. The rail displacement of the ballasted track was also predicted by an FE model that considers the spring stiffness at the rail support point, which includes the subgrade stiffness. It was confirmed that the subgrade modulus of an in-service ballasted track could be reliably predicted on the basis of the dynamic wheel load and rail displacement using the proposed subgrade modulus map.

Effects of Span-to-depth Ratio and Poisson’s Ratio on Elastic Constants from Bending and Plate Tests1

Gi Young Jeong,Jin Hyuk Kong 한국목재공학회 2015 목재공학 Vol.43 No.2

The goal of this study is to evaluate the limitation of ASTM D 198 bending and ASTM D 3044 in determination of elastic modulus and shear modulus. Different material properties and span to depth ratios were used to analyze the effects of material property and testing conditions. The ratio of true elastic modulus to apparent elastic modulus evaluated from ASTM D 198 bending sharply decreased with increment of span to depth ratio. Shear modulus evaluated from ASTM D 198 bending decreased with increment of depth, whereas shear modulus evaluated from ASTM D 3044 was hardly influenced by increment of depth. Poisson’s ratio influenced shear modulus from ASTM D 198 bending but did not influence shear modulus from ASTM D 3044. Different shearing factor was obtained for different depths of beams to correct shear modulus obtained from ASTM D 198 bending equivalent to shear modulus from theory of elasticity. Equivalent shear modulus of materials could be obtained by applying different shearing factors associated with beam depth for ASTM D 198 bending and correction factor for ASTM D 3044.

Prediction of complex modulus in phase-separated poly (lactic acid)/poly (ethylene oxide)/carbon nanotubes nanocomposites

Zare, Yasser,Garmabi, Hamid,Rhee, Kyong Yop Elsevier 2018 Polymer testing Vol.66 No.-

<P><B>Abstract</B></P> <P>This study focuses on the modeling of complex modulus in phase-separated poly (lactic acid) (PLA)/poly (ethylene oxide) (PEO)/carbon nanotubes (CNT) nanocomposites. Palierne model for complex modulus of immiscible blends is developed assuming the significances of CNT and interphase regions. The predictions of developed model are compared to the experimental data from rheological experiment and the predictability of the developed model is studied. Furthermore, the roles of main parameters in the complex modulus of nanocomposites are explained to validate the developed model. The calculations show proper agreements with the experimental data confirming the predictability of the developed model. A higher concentration of continuous matrix and a smaller content of PEO droplets cause thicker and stronger interphase in nanocomposites. High CNT concentration and thin CNT mainly improve the complex modulus. Additionally, both thickness and complex modulus of interphase regions directly control the complex modulus of nanocomposites. This study can afford an insight for researchers to control and optimize the complex modulus in immiscible nanocomposites.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Palierne model for complex modulus of immiscible blends is developed for nanocomposites. </LI> <LI> The complex modulus in phase-separated PLA/PEO/CNT nanocomposites is predicted. </LI> <LI> The developed model assumes the significances of CNT and interphase regions. </LI> <LI> The calculations show proper agreements with the experimental data. </LI> <LI> Thickness and stiffness of interphase directly control the complex modulus of samples. </LI> </UL> </P>