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Saravanan Umakanthan
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Saravanan Umakanthan
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Saravanan Umakanthan
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Saravanan, Umakanthan
Sarvanan, U.
Saravanan, U.
Umakanthan, S.
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3 results
Now showing 1 - 3 of 3
- PublicationCharacterization of petroleum pitch using steady shear experiments(01-11-2010)
;Chockalingam, Kanmani; Murali Krishnan, J.Asphalt for highway and runway construction is processed by either air blowing or blending with different petroleum streams. In the blending process, petroleum pitch, a by-product of solvent deasphalting of the vacuum residue is mixed with heavy extract to produce asphalt of the desired specifications. The rheological response of blended asphalt hence depends to a large extent on the constitutive property of petroleum pitch. In an aim to develop robust models for blended asphalt, modeling the mechanical behavior of petroleum pitch hence becomes necessary. In this work reported here, petroleum pitch from crude sources such as Basrah Light, Arab Mix and Arab Light are subjected to steady shear for 99 min at temperatures ranging from 70 to 120 °C for different shear rates. Each of these material exhibited different stress overshoot and decay during steady shear depending on the temperature and shear rate. A viscoelastic fluid model of the rate type is selected to model the response of the material. Using the recent thermodynamic framework based on Gibbs potential proposed by Rajagopal and Srinivasa [27], restrictions on the proposed model are obtained. The rotational flow problem is solved and the material parameters are estimated. The model predictions are corroborated with the experimental observations and they are found to be reasonably good. © 2010 Elsevier Ltd. All rights reserved. - PublicationOn measurement of dynamic modulus for bituminous mixtures(02-09-2019)
;Deepa, S.; Murali Krishnan, J.The AASHTO:TP-79 (2010), Standard method of test for determining the dynamic modulus and flow number for hot mix asphalt using the asphalt mixture performance tester (AMPT) stipulates the test procedure for the measurement of dynamic modulus of bituminous mixtures. In this test, the stress–strain–time data for different frequencies (from 25 to 0.01 Hz) are generated and used in the calculation of dynamic modulus. In this investigation, dynamic modulus data of four types of bituminous concrete mixtures (an unmodified binder and three modified binders) are studied using this protocol. The experiments showed that the total strain decreased with time at higher temperatures and at lower frequencies while at lower temperatures and higher frequencies, the total strain was seen increasing. It was also observed that at higher temperatures and low frequencies, the phase lag decreased with a decrease in frequency. While many studies have reported such results, these are normally called as ‘anomalous’ and ascribed to the errors in measurement mechanisms. These observations seem to have not been investigated within the context of the viscoelastic behaviour of the material. This study shows that the so called ‘anomaly’ is a response shown by a viscoelastic material. In the current study, the analysis of the data showed that the increasing and decreasing trend in strain can be attributed to two phenomena: the creep due to successive loading and the recovery of the residual deformation in the material due to a reduction in load level. It is demonstrated that the observed material response for the test conducted as per this test procedure can be qualitatively predicted using many viscoelastic models, however, one has to take into account the entire load history. - PublicationIssues related to measurement of dynamic modulus of bituminous mixtures(01-01-2016)
;Deepa, S.; Murali Krishnan, J.The AASHTO: TP 79-10 standard stipulates the test procedure for the measurement of dynamic modulus of bituminous mixtures. In this investigation, dynamic modulus data of two types of bituminous concrete mixtures (an unmodified binder and crumb rubber modified binder) are studied using TP-79-10 protocol. The experiments showed that the total strain decreased with time at higher temperatures and at lower frequencies. Also, for some mixtures, the phase lag decreased with decreasing frequency. While many studies reported such observations, these anomalous results are normally ascribed to the errors in measurement mechanisms and have not been explained within the context of the material behavior. Here it is shown that Burgers' viscoelastic model exhibits these phenomena. Also, the need for data processing techniques using the complete loading history and a viscoelastic model is emphasized.