![]() The serviceability, durability and maintenance factor is dependent primarily on viscosity property of bitumen type used. The bitumen used for an area having high temperature is not the same that is used in lower temperature areas (cold regions). This factor is also a governing factor that assures the exposure of bitumen to open environment. It is very essential to understand the viscosity variations of the bitumen used in the construction process, with the temperature. Bases on different varieties of bitumen, the viscosity changes with temperature also differs. Influence of Temperature on The Viscosity of Bitumenīitumen tend to soften, when subjected to a temperature rise and will harden when the temperature falls. The Brookfield and Thermocel rotational viscometer let the measurement of bitumen viscosity at varying temperatures. Now, the most practical means to measure the viscosity of bitumen is with the help of rotational viscometer test (ASTM D4402 -02). This is also called the absolute viscosity. The coefficient of viscosity is represented by ?. Relative speed of movement of one plate with respect to other -V.The resistance of force is represented by ‘F', which is dependent on the: The arrangement involves keeping the bitumen layer between metal plates for different combinations of loading time and temperature. The force in the layer is also calculated. The displacement happening on a thin layer of bitumen can be determined with the help of a sliding plate test. Atmospheric capillary tube viscometer is employed to measure the kinematic viscosity. The vacuum capillary tube viscometer is used to find absolute viscosity. The specifications kept for measurement is the absolute viscosity at 60 degree Celsius and a Kinematic viscosity at 135 degree Celsius. The dynamic viscosity can also be calculated in terms of kinematic viscosity in units m 2/s or mm 2/s.īased on absolute or kinematic viscosity requirement, the bitumen viscosity can be measured by a variety of devices. The viscosity can be defined as the ratio of shear stress applied to the rate of shear strain. Influence of Temperature on The Viscosity of Bitumen.Greater the aggregation, greater is the viscosity. The asphaltenes have aggregation tendency.The change in viscosity is governed by the asphaltenes particles.The viscosity increases with increase in asphaltenes quantity.The influence of asphaltenes on viscosity of bitumen can be summarized as: These effects are depended on the aromatic stabilization. So, two opposing factors are said to exist. This on other hand makes the aggregation of asphaltenes miscelles, causing viscosity decrease. The increase in saturated oil quantity would bring the viscosity down, but it increases the aggregation of asphaltenes with aggregates, making the structure gel type. This has a low viscosity and low molecular weight. Now the saturated oil quantity will affect the maltenes continuum. Sol Type Bitumen Schematic Diagramįig.2.Schematic Diagram of Gel type bitumen If it's not sufficient the micelles will join as shown in figure-1.įig.1. This layer is stable and promotes dispersion. The aromatics in sufficient quantity provide a layer around the Asphaltenes. The asphaltenes dispersion is controlled by the above mentioned elements in bitumen. Gel type bitumen have a higher viscosity.īitumen consist of resins, aromatics and some form of saturated oil after their manufacture. Aggregation is the factor that governs the viscosity of gel type bitumen. As the asphaltenes content reduces, the viscosity of bitumen also decreases. ![]() In bitumen sol, the asphaltenes miscelles are dispersed in maltenes continuum. The bitumen is a composition of two factors ( Structure of Bitumen) asphaltenes miscelles and maltenes. ![]() The two factors that define the viscosity of bitumen are: Under the action of force, the fluid reflects higher resistance when the viscosity is high. The resistance of a liquid in flowing is defined as the viscosity of that fluid. □ Reading time: 1 minute Introduction to Viscosity and Rheology of Bituminous Materials ![]()
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