Murali Krishnan

Murali Krishnan
Indian Institute of Technology Madras | IIT Madras · Department of Civil Engineering

Ph.D.

About

142
Publications
36,972
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
1,412
Citations
Introduction
Skills and Expertise

Publications

Publications (142)
Preprint
The effects of temperature and age on stress relaxation were investigated for a set of seven asphalt binders from a northern Ontario pavement trial. It was found that between binders there were rather wide variations for different modes of relaxation. The first peak in the relaxation spectrum, originating from the rapid relaxation within the mobile...
Article
The one-to-one contact of coarse aggregate is considered to be the main source for the resistance to permanent deformation and to an extent to fatigue damage. Therefore, it is imperative that the mixture is placed with an interlocked coarse-aggregate skeleton. The conventional mix design approaches generally follow dense graded aggregate gradations...
Article
The delineation of the linear/nonlinear response of bituminous material in the frequency domain is conducted using the small-amplitude oscillatory shear test, wherein only the peak stress and strain are available. In contrast, the large-amplitude oscillatory shear tests provide complete waveform data. Analysis of such data can help to unravel the l...
Article
Complex issues persist in quantifying the fatigue response of warm mix asphalt (WMA). Due to reduced aging, WMA is expected to perform better in fatigue when compared to hot mix asphalt (HMA). However, the fatigue life of WMA can reduce due to the potential for increased moisture damage. To reduce the moisture induced damage, hydrated lime is usual...
Article
Full-text available
Foam characteristics, including density, stability, and texture, influence the properties of end products like foamed concrete. The present work investigates the individual and combined influence of xanthan gum and low-cost sodium-based admixtures (NaOH, NaCl, and Na2CO3) on the viscosity of sodium lauryl sulfate (SLS) foaming solution and the foam...
Article
Full-text available
Modification using elastomeric thermoplastic polymers is commonly adopted to improve the high-temperature performance of paving bitumen. The performance of modified bitumen classified under the same grade is highly variable depending on the type of base bitumen, the polymer architecture, and its dosage. The current specification parameters are inse...
Article
The performance of modified binders and mixtures has been assessed through different tests performed in the laboratory. Scarcely, any study has compared it with the performance of the bituminous mix depending on its placement, i.e., whether it is placed in the wearing course or in the binder course. To evaluate the same, four binders, namely, unmod...
Chapter
This investigation reports the use of stress-strain-time data for different frequencies at a given temperature for computing the retardation spectra. While the existing attempts use a master curve based approach with continuous relaxation spectra, the use of a discrete retardation spectrum at a given temperature directly computed from the model par...
Chapter
Bituminous mixtures offer varying compactive resistance due to gradation, binder type, its content, and temperature. Most of the attempts to quantify laboratory-scale compaction resistance have used Superpave Gyratory Compactor (SGC). However, SGC has criticism related to poor spatial uniformity of air voids, whereas the Shear Box Compactor (SBC) i...
Article
In the AASHTO T-378 protocol for computing dynamic modulus and phase angle, the bituminous mixture sample is subjected to a continuous loading from high frequency to low frequency. The postprocessing method involves fitting a regression equation to the stress and the strain data. The influence of confinement pressure and rest period between the fre...
Article
Cold recycling of asphalt pavement is an effective rehabilitation technique in terms of saving natural resources and cost of construction. The current study focuses on cold-recycled asphalt mixture designated as emulsified cold-recycled mixture (ECRM) that contains 100% reclaimed asphalt pavement material and slow-setting asphalt emulsion. Here, a...
Article
This investigation pertains to the bitumen production using component blending. During the manufacture of blended bitumen, the proportion of the constituents, the temperature during blending, and the duration of blending are selected to meet the penetration at 25°C and the absolute viscosity at 60°C as per the Indian specifications. The choices of...
Article
Pond ash is a mixture of fly ash and bottom ash obtained from thermal power plants. It has pozzolanic properties and is commonly treated with cement to impart cohesion and improve strength. The increase in strength gain in cemented pond ash is attributed to the hydration of cement and pozzolanic reactions due to silica present in the pond ash. Unco...
Article
Elastomers, plastomers, and Reactive Ethylene Terpolymers (RETs) are some of the most commonly used polymers for modification of bitumen. Each type of modifier can have a considerably different influence on the rheological behavior of the binders and therefore, the performance of bituminous mixtures in pavements. In this study, for comparing the ef...
Article
A majority of the approaches currently available for predicting rutting suggest limiting the vertical compressive strains on top of the subgrade in a pavement structure. Such approaches do not explicitly consider the rutting in individual layers. To factor the influence of axle loads, and environmental conditions on bituminous layer rutting, a rut...
Chapter
Full-text available
Rutting in bituminous pavements predominantly depends on the aggregate gradation. In particular, for fine graded mixtures, the aggregate gradation below 2.36 mm play a critical role since more than 60% of aggregates will pass through this sieve. The present work is focused on quantifying the rut resistance of three different fine aggregate gradatio...
Chapter
One of the major parameters which influence the performance of bituminous mixtures is a packed aggregate skeleton with minimum particle rearrangement during traffic loading. The current practice of aggregate design for bituminous mixtures is mostly based on the Fuller-Thomson model to achieve maximum density. However, this approach does not explici...
Article
Full-text available
Production of bitumen for paving purposes is a complex operation at the refinery considering the variability in the crude source. At any instant of time, refineries process a blend of different crudes, and the associated process parameters are varied in real time to maximize the throughput of the lighter ends. Such changes influence the chemical co...
Chapter
Full-text available
Distresses such as rutting in bituminous mixtures are known to be largely influenced by the aggregate skeleton. For a given optimum binder content, the challenge lies in making a choice of aggregate gradation which will lead to optimal performance in rutting and fatigue cracking. As a first step, the present work is focused on quantifying the rut r...
Chapter
Within the context of warm mix asphalt (WMA), there is a necessity to re-look at the distress mechanisms. Since the WMA undergoes reduced aging during mixing and compaction, one expects a reduction in the stiffness of the initial in-place material. Such reduced stiffness can lead to a widely varying mechanical response of the mixture during the per...
Chapter
Full-text available
Within the context of the mechanistic-empirical pavement design guide, the rut depth transfer function used consists of local calibration and material-specific coefficients. The material-specific coefficients ensure that the material-specific creep and recovery data can be used within the context of simulation for quantification of rutting. In this...
Chapter
Full-text available
IRC:37-2012 suggests to use resilient modulus as an input parameter in the design of bituminous pavements in India. IRC:37 specifies the values of resilient modulus at different temperatures for Bituminous Concrete (BC) and Dense Bituminous Macadam (DBM) mixes with various grades of unmodified and modified binders. However, IRC:37 recommends identi...
Chapter
Full-text available
Air blowing and propane deasphalting (PDA) blending are the two processes used by the refineries in India to produce paving grade bitumen. In the PDA blending process, the proportion of the constituents (PDA pitch and flux) used in producing bitumen is decided based on the grade of bitumen to be processed. One main issue in the production of bitume...
Article
Full-text available
Different methods are available to quantify the fatigue damage of the asphalt mixtures. Among these, methods based on the concept of dissipated energy are used predominantly. Characterizing fatigue damage using the concept of dissipated energy is complicated due to the presence of other modes of dissipation, for instance, viscous dissipation. Hence...
Article
Laboratory fatigue characterization of bituminous mixtures is carried out typically by conducting a beam bending test at a given frequency and temperature for various strain/stress levels. In the current fatigue test methods, the material is tested at 20°C with continuous loading, and the fatigue life is estimated based on the stiffness modulus and...
Article
Rutting is one of the major distresses observed in bituminous pavements. In the majority of the design approaches including the Indian Road Congress (IRC) guidelines for the design of bituminous pavements, the rut depth is predicted by limiting the vertical compressive strain at the top of the subgrade. Here, due consideration is not given to the r...
Conference Paper
Full-text available
For a realistic estimation of stresses and strains in the pavement, it is necessary to consider the dynamic normal load transferred from a truck to the pavement. The roughness of the pavement, and driving maneuver influences the dynamic load transferred. This study investigates the role of acceleration for a given pavement roughness profile. The re...
Article
Full-text available
Warm-mix asphalt (WMA) additives are widely used to reduce the mixing and compaction temperatures of the bituminous mixes. Due to lower aging temperature, one can expect a reduction in aging compounds in a WMA mix in comparison with the hot-mix asphalt (HMA) mix. In this study, an attempt is made to address the influence of the production process a...
Article
Full-text available
This investigation reports the influence of processing condition (air rectification and component blending) on ageing and stress relaxation behaviour in bitumen. FTIR spectra were recorded on two samples of bitumen at unaged, short-term aged and long-term aged conditions. Indices such as aliphaticity, aromaticity, carbonyl and sulphoxide calculated...
Article
Full-text available
This study focuses on the laboratory investigations carried out to quantify the fatigue life of viscosity grade 40 (VG40) and crumb rubber modified bituminous (CRMB) mixtures and the influence of rest period. Four-point beam bending experiments were carried out with strain-controlled loading at 20 ∘C and 10 Hz frequency with and without rest period...
Article
Full-text available
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 spectr...
Article
Full-text available
The measurement of rheological properties of binders is dependent on various factors such as time, temperature as well as on aging. The common causes of erroneous measurements that occur during the rheological tests are related to the sample conditioning and sample loading. Bituminous binders are subjected to steric hardening while stored at room t...
Article
Full-text available
This paper investigates the influence of gauge length on the measurement of resilient modulus of bituminous mixtures with modified and unmodified binders tested at 25 °C. From this investigation, it is clear that for the tests carried out using a quarter-gauge length, the cumulative vertical deformations at the end of 200 preconditioning load cycle...
Article
Full-text available
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 mixed with the aggregate particles and subjected to compaction, the binder exhibits interesting transitions from a Newtonian fluid to a non-Newtonian fluid...
Conference Paper
Full-text available
The bituminous pavements in India are designed as per the guidelines provided in IRC: 37-2012. The design procedure follows layered linear elastic theory for computing the critical strains and stresses and the input material property for bituminous mixtures is resilient modulus to be measured following ASTM D7369-11. While ASTM D7369-11 mentions th...
Article
Various testing methods, such as the static triaxial test, cyclic resilient modulus test, repeated-load static triaxial test, repeated-load California Bearing Ratio (CBR) test, and repeated-load oedometer test, were explored to characterize pavement granular materials. Using such methods, an experimental data set of the stress–strain response of a...
Article
Full-text available
The working temperature of a bituminous pavement can typically range from 75 C to C. Bitumen shows a wide spectrum of mechanical behaviour in this temperature range and these include those of a viscoelastic fluid, a viscoelastic solid and an elastic solid. Due to the amorphous nature of the material, the transitions between such mechanical response...
Article
Rutting is one of the most common distresses observed in bituminous pavements. A number of test procedures, associated parameters, and correlations have been developed for the binder and the mixture to evaluate their rutting performance. In this investigation, the rutting performance of an unmodified, and three modified binders (Elastomer, Plastome...
Conference Paper
Full-text available
This paper investigates the variation of dynamic modulus and phase lag with confinement pressure and rest period. In this investigation, bituminous mixtures fabricated with unmodified VG30 binder were used and tested as per AASHTO: TP-79 (2010) protocol incorporating confinement pressure and rest period between successive frequencies. The analysis...
Article
Full-text available
Warm mix asphalt (WMA) technology is used to reduce mixing and compaction temperature of the binder; however, such addition is also expected to influence the rheological response of the binder during pavement service. This investigation is focused on WMA binders produced using Evotherm (Evotherm-VG30) and Sasobit (Sasobit-VG30) with a base binder (...
Article
Cold in-place recycling technology for reclaimed material in pavement rehabilitation holds promise as a solution to resource scarcity. This paper reports results of a systematic experimental investigation of the material produced by this technique and in particular the role of cement and air void content. The internal structure is characterized usi...
Article
Cold in-place recycling technology for reclaimed material in pavement rehabilitation holds promise as a solution to resource scarcity. This paper reports results of a systematic experimental investigation of the material produced by this technique and in particular the role of cement and air void content. The internal structure is characterized usi...
Article
Full-text available
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...
Conference Paper
Full-text available
The production of bitumen in Indian refineries is carried out by air blowing and component blending. In the component blending process, a highly viscous propane deasphalted (PDA) pitch is blended with a less viscous flux. The choice of the proportion of these two components is normally arrived at to meet the required technical specification such as...
Article
Full-text available
This investigation was conducted to critically look at the IS73:2006 specification for bitumen and suggest selection criteria to enhance the confidence of the user about the quality of bitumen to be used in road construction. Towards this effort, 300 samples of bitumen from refineries and construction sites were collected. All the samples were chec...
Article
This work details the experimental and analytical procedures related to the quantification of dynamic modulus for Bitumen Stabilized Material (BSM). It is shown that the existing dynamic modulus test protocol followed for Hot Mix Asphalt (HMA) cannot be used for BSM material due to certain anomalies noticed in phase lag and strain evolution. To add...
Article
Full-text available
In this investigation, the fatigue life of bituminous mixtures is characterised using the four-point bending test. Two sets of bituminous concrete samples, one produced with unmodified binder and other with plastomer-modified binder, are subjected to repeated strain-controlled sinusoidal loading at 10 Hz frequency and 20°C. The test is conducted fo...
Article
Full-text available
Two major types of warm mix asphalt (WMA) technologies exists and they are wax-based and chemical-based. The wax-based additive melt completely in the binder at the mixing and compaction temperatures and hence enable construction at lower temperature. The chemical-based additives facilitate similar results during construction, however, by reducing...
Article
Bituminous pavements constructed across India undergo premature failure much before their design life. There could be many reasons attributed to such failure and these include inappropriate selection of materials, lack of dependable traffic and axle load data and limited information related to distresses for analysis. In this paper, using a compreh...
Article
In this study, four point beam tests were conducted on bituminous mixture sample pertaining to Bituminous Concrete (BC) grade II as per MORTH specification. The samples were produced using unmodified binder and modified binders. Two types of modified binders, one with crumb rubber and other with polymer were used. A beam sample of size 450×150×160...
Article
The Warm Mix Asphalt (WMA) technologies allow a significant reduction in mixing and compaction temperatures of asphalt mixtures through lowering the viscosity of binders. In WMA, different types of additives are added to the binder depending on the technology used and such addition of these materials brings down the viscosity drastically thus reduc...
Conference Paper
One of the main distress criteria affecting the performance of bituminous pavement is fatigue cracking. Such cracks appear in the wheel path and are due to myriad of factors including aging, stiff binders, traffic repetitions and large magnitude of loads. Taking into account the increased emphasis on the use of warm mix asphalt (WMA) technologies,...
Conference Paper
One of the main distress criteria affecting the performance of bituminous pavement is fatigue cracking. Such cracks appear in the wheel path and are due to myriad of factors including aging, stiff binders, traffic repetitions and large magnitude of loads. Taking into account the increased emphasis on the use of Warm Mix Asphalt (WMA) technologies,...