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Softening Point of Bitumen: A Practical Guide for Ring-and-Ball Apparatus

LDHs was introduced into 70# asphalt binder by different weight ratio. Asphalt penetration test, soft point test, ductility test, viscosity test, dynamic shear rheometer (DSR) test and Fourier transform infrared (FTIR) test, were conducted to characterize and predict the LDHs modified asphalt. Research results indicated that the LDHs has great effect on resistance to UV of asphalt, which makes the asphalt absorb less ultraviolet radiation under the same UV intensity. Complex modulus, phase angle and FTIR test results indicate that the LDHs can significantly enhance the property of anti-ultraviolet aging of asphalt. The test results show that the LDHs has an obvious improvement on the anti UV aging of asphalt.

Softening Point Test For Bitumen Pdf Download

Technical warning - The change from mercury thermometers to electronic temperature devices has revealed that the temperature definition in the mercury thermometer has not been precise enough to make a correct, unbiased transfer to electronic devices. Care should be taken for softening points ring and ball above 100 C as the condition may have changed from previous practise to present days testing equipment. Below approx. 100 C the difference in temperature readings between electronic and mercury stem thermometer is acceptable compared to the repeatability of this test methods. [Reference: ASTM E20 Group]

The current experimental method used in Europe to characterise asphalt binder at high temperature is based on the Ring & Ball softening point. However, for modified binders it was demonstrated that such a method is unable to correctly characterise the material. In the present work, an alternative solution to determine the high-temperature properties of asphalt binders using the dynamic shear rheometer (DSR) is proposed: the Binder-Fast-Characterisation-Test (BTSV) (Bitumen-Typisierungs-Schnell-Verfahren, in German). Two parameters are identified for the rheological characterisation of asphalt binders: the temperature TBTSV, which is related to the Ring & Ball softening point and is an indicator of the binder stiffness, and the phase angle δBTSV, which provides information on the degree of binder modification. These two key parameters are used to discriminate among the different asphalt binder domains in the high-temperature range.

For a suitable determination of bitumen performance in different environments, different systems of classifications have been adopted based on empirical tests (like penetration grade classes, European classification EN 12591 [1]) or fundamental tests based on rheology (like Superpave specifications) [3, 16]. According to the European Standard EN 12591 [1], the penetration grade of bitumen is determined by two main characterization tests: Penetration (PEN) and Softening Point (SP) measures [17, 18]. The penetration and softening point of bitumen are used to characterize the consistency and stiffness of bitumen at ambient and high service temperature respectively, which are undoubtedly affected by the physical and chemical properties of bitumen [3, 16]. The interpretation of these two standard tests is difficult and cannot be directly linked to the temperature susceptibility or the viscoelastic properties of bitumen [16]. However, the penetration grade classes system is still widely used in European countries for bitumen classification.

In consequence, researchers have put a lot of effort to correlate and possibly model the penetration and softening point test of bitumen with its different physical or chemical properties by using different analytical techniques. It was found that an increase of viscosity leads to a SP increase and a PEN decrease. Some models have been proposed to predict SP or PEN from viscosity [19, 20]. A proven relationship between SARA fractions and SP or PEN has been demonstrated by many researchers [14, 21, 22]. For instance, increasing asphaltenes content has a similar effect to viscosity on PEN and SP. Weigel and Stephan [11] proposed prediction models of PEN and SP based on the contents and the molecular weights of SARA fractions. A more recent trend is the use of spectroscopic techniques to model SP and PEN, like Fourier Transform Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance (NMR). Jaimes et al. proposed some models for SP and PEN predictions based on Low Field NMR (LF-NMR) and H-NMR [10]. However, most of the proposed predictive models of SP or PEN were built by using samples with narrow ranges of SP and PEN, and the predicted results are relatively unreliable compared to the standard methods. To the best of our knowledge, no comparison has been made between the different analytical approaches used for SP and PEN predictions. Since every author has used this own set of samples to develop the models, and on a quite limited prediction window, the performance of each approach has not been yet compared using the same set of bitumen samples.

The study has involved 13 samples of bitumen, which were obtained from different crude oil straight run distillation. The list of the samples is presented in Table 1. The samples are distillation residues, which differ from each other in terms of the geochemical and geographical origin of the crude oils used for distillation, with a wide SP/PEN range. Due to the important diversity of origin, the sample characteristics such as the density, penetration, and softening point are relatively diversified. This variability indicates that the studied samples have different chemical compositions.

Bitumen characterization remains a challenging task owing to its extreme complexity. More effort is still needed to achieve more knowledge of the relationship between the physical, chemical properties of bitumen and SP and PEN tests. In this study, characterization of 13 different bitumen samples was done using a variety of physicochemical properties and techniques. These multi-criteria analyses were studied to determine their correlation with two standard characterization tests of bitumen: Softening Point (SP) and Penetration (PEN) using correlation matrix and Principal Component Analysis (PCA). Some predictive models for SP or PEN tests have been proposed based on viscosity, FT-IR, H-NMR or a combination of parameters. The following conclusions could be drawn:

Although the sample set used in this study is very diverse and covers a very wide range of SP or PEN, it is recommended that this work is reproduced by using a larger amount of samples, other types of bitumen samples (such as air-blown bitumens or bitumens with polymer additives), and more analytical techniques to further assess the correlation of many properties of bitumen with SP and PEN. External validation is needed in order to ensure that models are not overfitted, especially for the multiparameter models. The scope of this work can be extended in the future to study the correlation between these different analytical techniques and the evolution of SP or PEN with different standard aging tests like Rolling Thin film Oven Test (RTFOT) and Pressure Aging Vessel (PAV).

It measures the hardness or softness of bitumen by measuring the depth in tenths of a millimeter to which a standard loaded needle will penetrate vertically in 5 seconds. BIS had standardized the equipment and test procedure.

The penetrometer consists of a needle assembly with a total weight of 100g and a device for releasing and locking in any position. The bitumen is softened to a pouring consistency, stirred thoroughly and poured into containers at a depth at least 15 mm in excess of the expected penetration. The test should be conducted at a specified temperature of 250C.

Ductility is the property of bitumen that permits it to undergo great deformation or elongation. Ductility is defined as the distance in cm, to which a standard sample or briquette of the material will be elongated without breaking. Dimension of the briquette thus formed is exactly 1 cm square. The bitumen sample is heated and poured in the mould assembly placed on a plate. These samples with moulds are cooled in the air and then in water bath at 270C temperature. The excess bitumen is cut and the surface is leveled using a hot knife. Then the mould with assembly containing sample is kept in water bath of the ductility machine for about 90 minutes. The sides of the moulds are removed, the clips are hooked on the machine and the machine is operated. The distance up to the point of breaking of thread is the ductility value which is reported in cm.

The test is conducted by using Ring and Ball apparatus. A brass ring containing test sample of bitumen is suspended in liquid like water or glycerin at a given temperature. A steel ball is placed upon the bitumen sample and the liquid medium is heated at a rate of 50C per minute. Temperature is noted when the softened bitumen touches the metal plate which is at a specified distance below.

The viscosity expressed in seconds is the time taken by the 50 ml bitumen material to pass through the orifice of a cup, under standard test conditions and specified temperature. Viscosity of a cutback can be measured with either 4.0 mm orifice at 250C or 10 mm orifice at 25 or 400C.

At high temperatures depending upon the grades of bitumen materials leave out volatiles. And these volatiles catch fire which is very hazardous and therefore it is essential to qualify this temperature for each bitumen grade. BIS defined the ash point as the temperature at which the vapour of bitumen momentarily catches fire in the form of ash under specified test conditions. The fire point is defined as the lowest temperature under specified test conditions at which the bituminous material gets ignited and burns.

The apparatus consists of an aluminum oat and a brass collar filled with bitumen to be tested. The specimen in the mould is cooled to a temperature of 50C and screwed in to oat. The total test assembly is floated in the water bath at 500C and the time required for water to pass its way through the specimen plug is noted in seconds and is expressed as the oat value.


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