M. R. Nivitha

Bio: M. R. Nivitha is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Asphalt & Composite material. The author has an hindex of 3, co-authored 7 publications receiving 127 citations. Previous affiliations of M. R. Nivitha include PSG College of Technology.

Ageing in modified bitumen using FTIR spectroscopy

Abstract: Modified binders exhibit complex rheological behaviour due to the interaction of the modifiers with the base binder and the manner in which they age during field applications. Quantification of the interaction and the ageing of such modified binders is currently a necessity. In this investigation, three modified binders (elastomer, plastomer, and crumb rubber) and the base bitumen were subjected to different ageing conditions and the evolution of the chemical functionalities during ageing were tracked using FTIR spectroscopy. Analysis of the spectra of modified binders immediately after the production process showed that while the elastomer modified binders exhibited physical interaction, the plastomer and crumb rubber modified binders exhibited physical and chemical interactions. During ageing, there was no subsequent evolution of the interactions and one could only see chemical functionalities related to oxidation. Analysis of the spectra showed that the carbonyl and sulphoxide exhibit identical trends ...

Transitions in unmodified and modified bitumen using FTIR spectroscopy

Abstract: The transitions in bitumen in the temperature range of 25–75 °C are normally investigated using rheological tools. Considering the complex response of the material in such temperature range, it will be helpful if the precise nature of the material is investigated at the macromolecular level also. In this study, an attempt is made to use FTIR spectroscopy to identify the thermal transitions in unmodified and three modified bitumen. The changes in peak position and intensity of the C–H stretching vibration at 2953, 2923 and 2853 cm−1 were analyzed. Transitions, predominantly solid–solid in nature were identified in the temperature range of 35–65 °C which can be attributed to the change in conformation of the crystalline fraction. While certain peaks distinguished the effect of modification and aging, few other peaks indicated multiple transitions in the solid state of the material. The degree of crystallinity, also calculated from the FTIR spectra, indicated changes in the conformation of the material in the temperature range of 45–55 °C.

What is Transition Temperature for Bitumen and How to Measure It

Abstract: In a typical year and for any typical location in India, the lowest temperature of the pavement can go up to 0 °C or below and the highest temperature can reach up to 70 °C or above. During such temperature changes, the binder exhibits behaviour ranging from a glassy material (at lower temperature) to a viscoelastic/non-Newtonian fluid (at higher temperature). The range of temperature change which is of interest to a pavement engineer is the transition between viscoelastic solid to viscoelastic fluid. Two measurements are normally used for quantifying the transition temperature and they are the G′–G″ cross over point and the point when tan δ is independent of frequency (Winter-Chambon criterion). These measures are applicable when the material has a single relaxation time (typically a single constituent material). Since bitumen is a mixture of several complex hydrocarbons each with different relaxation time, it is natural that such measures are also frequency dependent. This investigation will focus attention on determining the frequency dependence of G′–G″ cross over point as well as the relationship of tan δ with frequency. An unmodified binder of VG30 grade as per IS73-2013 and a crumb rubber modified binder of meeting CRMB 60 grade as per IS:15462-2004 were used in this investigation. To estimate the viscoelastic solid–fluid transition temperature, frequency domain tests were performed in the temperature range of 25–75 °C for frequencies in the range of 50–1 Hz. All the tests discussed in this study were performed at two aging conditions, unaged and short-term aged. Due to the frequency dependent nature of bitumen, the transition temperature is not a sharp point as in the case of polymers but occurred gradually over a temperature range. Contrary to what one expected, modification process did not drastically change the transition temperature and one could see a change of only 3 °C for CRMB 60 when compared to VG30. Aging of the modified bitumen proportionally shifted the transition temperature in a similar manner to that of the unmodified bitumen. It was also clearly seen that the Winter-Chambon criterion was not met for all the binders investigated in this study.

Rheological characterisation of unmodified and modified bitumen in the 90–200°C temperature regime

Abstract: Developing an understanding of the compaction mechanics during the production process of the bituminous mixture is an essential step in the construction of bituminous pavement. As the binder is mix...

Viscoelastic transitions exhibited by modified and unmodified bitumen

Abstract: The working temperature of a bituminous pavement can typically range from 75∘C to −20∘C. Bitumen shows a wide spectrum of mechanical behaviour in this temperature range and these include those of a...

FTIR spectral analysis of bituminous binders: reproducibility and impact of ageing temperature

Abstract: This RILEM round robin study with nine participating laboratories investigated bitumen ageing, its effect on chemical properties and its reproducibility. The impact of temperature used for short-term (RTFOT) binder ageing on the combined short- and long-term (PAV) aged samples was investigated; thereby the effect of reduced mixing temperature such as those relevant for warm mix asphalt technologies on long term ageing was examined. Four 70/100 penetration graded bituminous binders from different sources were selected. In addition to the standard RTFOT temperature of 163 °C, two additional temperatures, 143 and 123 °C were used. The Fourier transform infrared spectroscopy (FTIR) analysis was carried out using an integration method which considers the area below the absorbance spectrum around a band maximum using baseline and tangential approaches. A statistical investigation into the reproducibility of FTIR spectra analysis based on the accumulated data was done. To assess the reproducibility, the coefficient of variation (CV) was taken as a benchmark parameter. Carbonyl and sulfoxide indices were calculated using different baseline correction methods and tangential and baseline integration, respectively. It was shown that the tangential method was not influenced by the applied baseline correction. However, in all considered cases, the tangential method led to significantly worse reproducibility (CVs ranging from 20 to 120%) compared to the baseline method. The sulfoxide indices calculated by both methods were not affected by the baseline correction method used. Impacts of changes in the short-term ageing temperature on short- or long-term aged samples could not be found whereas differences between different binder sources could be detected. RTFOT temperature and therefore mix production temperature had a stronger impact on the formation of sulfoxide structures than for carbonyl structures. The findings from this study show the most reproducible of all considered methods when more than one laboratory is providing FTIR data.

Repeatability and sensitivity of FTIR ATR spectral analysis methods for bituminous binders

Abstract: Bituminous binders as organic materials are prone to aging mainly by oxidation. Aging changes the viscoelastic behavior of the material over time towards higher stiffness and brittleness. FTIR has been increasingly used lately to investigate impacts of oxidative aging on the chemical structure of bitumen. Especially the carbonyl and sulfoxide bands are affected by aging and commonly used to describe changes due to evolving oxidation of a binder. However, spectra obtained from FTIR can be analyzed in fundamentally different ways and the analysis method applied to a spectrum has an impact on the gathered results and especially on the repeatability and sensitivity with regards to oxidative changes. For the presented study, two bituminous binders, a PG 64-16 and an SBS modified PG 76-22 PM were aged by RTFO and PAV and subsequently measured by FTIR. The obtained spectra (up to 90 individual spectra per aging state) were analyzed employing various methods using either the original or a normalized spectrum, a band maximum or integration based calculation of indices from an absolute or tangential baseline. By analyzing the coefficient of variation of the different analysis methods, it was found that not all analysis methods exhibit the same repeatability and sensitivity. From the findings of the study it can be recommended to work with normalized spectra, use an absolute baseline and work with integration of areas for index production in favor over band maximum based methods.

Effect of ageing on the mechanical and chemical properties of binder from RAP treated with bio-based rejuvenators

Abstract: Reclaimed asphalt pavement (RAP) is harder than virgin bitumen due to ageing and it needs to be rejuvenated. Three bio-based rejuvenators are used and the rejuvenating effects are evaluated. Rheological tests show how the rejuvenators may restore the mechanical properties of RAP binder. An ageing index is proposed to show that the rejuvenators are affected differently by ageing. Despite their addition, physio-chemical oxidation did not reverse. Mechanical changes were not caused by chemical changes at functional groups level but a rearrangement of polar/nonpolar components. The results show that considering the effect of aging is vital in identifying how rejuvenators affect the RAP binder chemically and mechanically.