Different methods for grading bitumen that is important to know
The construction of roads is one of the bitumen's many applications. Therefore, there are different methods for grading and categorizing this substance that is important to know according to the application.
modified bitumen roof
Even though it is one of the oldest materials in modern highways, it nevertheless holds a significant amount of popularity within this sector.
The relatively low cost of manufacturing, adaptability of both its physical and rheological qualities and the capacity to be recycled are the primary benefits of using bitumen as a binder in the road construction business.
It is vital to grade bitumen according to particular physical features so that asphalt manufacturing can continue to achieve the highest possible level of adhesion.
Throughout the course of history, numerous approaches and grading systems have developed, ranging from straightforward subjective inference to laborious test procedure-based classifications.
Bitumen Penetration Grading System
After undergoing numerous iterations, the penetration test machine was first commercially available in 1888.
By 1910, it had become the preeminent method for testing and controlling the consistency of bitumen at 25 degrees Celsius in the United States.
This temperature was decided upon as the best representation of the annual average ambient temperature.
The American Society for Testing and Materials (ASTM) Committee D04 on Road and Paving materials decided to grade bitumen based on the results of a penetration test conducted at 25 degrees Celsius.
In the United States of America, the American Association of State Highway and Transportation Officials (AASHTO) developed the first bitumen specification in 1931.
This specification was implemented in 1931.
According to the penetration grading system, bitumen is classified as a material that falls into the semi-solid category.
In the tests for penetration and ductility, the temperature was set at 250 degrees Celsius.
These tests are naturally empirical and can only give index properties.
There is no meaningful control on temperature sensitivity as it relates to pavement conditions.
These are the two primary reasons why these tests may be flawed.
Penetration grading includes tests at 25 degrees Celsius, but there is no way to measure how sensitive bitumen is to temperature or how well it performs at different temperatures.
As a result, many different kinds of bitumen, each with a unique combination of temperature sensitivity and performance, could all be considered the same grade.
softening point of bitumen
Bitumen Viscosity Grading System
In the early 1960s, a grading system for viscosity was initially implemented for the first time.
Other than the penetration at 25 degrees Celsius, this new grading system takes into account the absolute viscosity at 60 degrees Celsius and the kinematic viscosity at 135 degrees Celsius (ASTM D3381).
This grading technique was created in 1960 after taking into consideration the grading of old bitumen residue.
In order to determine how much bitumen had aged, a thin film oven test was performed.
This viscosity grading system was not well received by the majority of people for a variety of reasons, the most significant of which were the persistent absence of low-temperature properties, the expansive acceptance limits, and the absence of a mechanism for long-term aging.
In the early 1970s, efforts were made to maximize fuel output, which led to the discovery of additional resources.
As a result, both the supplies and the refining processes had to be varied, and the viscosity grading system required some modifications.
The modifications to the specifications included changes to the temperature susceptibility, the shear susceptibility, the primitive rheological parameters, and other compositional features.
The amendments that were made to the viscosity grading system for bitumen were causing significant issues for bitumen suppliers.
Around the middle of the 1980s, more than thirty-five distinct specifications were developed.
It was because of this perplexing grading scheme that the Strategic Highway Research Program (SHRP) was established in 1987.
The goal of this program was to create a countrywide consistent bitumen specification.
The viscoelastic nature of bitumen was the primary focus of their attention as they investigated its physical properties.
The first iteration of a performance grading system that was founded on fundamental rheological qualities was presented to the public in the year 1991.
If you look more closely at the various grades of viscosity-graded bitumen, you'll notice that they can be used for a variety of purposes.
These applications are divided into the following categories according to grade level:
- VG 10 is the grade that is the softest and has specifications that are near 80-100 for its penetration grade.
The majority of the time, it's utilized in extremely cold climates.
Additionally, it is utilized in applications involving spraying and in the production of bitumen emulsion.
- VG 20: The most common application for it is highway construction in areas with low temperatures and high altitudes.
– VG 30 is the grade that is utilized most frequently in the construction of heavy-duty roads.
It is possible to use it in place of 60/70 penetration grade bitumen without any noticeable difference.
– VG40: This grade has qualities and applications that are very similar to those of the 30-40 penetration grade.
penetration test of bitumen
Because of its higher viscosity, bitumen can be mixed into stiffer substances, which can improve the material's resistance to shoving and other issues that arise as a result of higher temperatures and heavier traffic loads.
Superpave Performance Grade
Evaluation of how well bitumen performs in actual applications is the most up-to-date method for ranking its overall performance.
Between 1987 and 1992, the Strategic Highway Research Planning organization was responsible for its development.
Included in the following are characteristics of the Superpave Performance Grading system:
It contains tests for binders that are made of bitumen.
The performance of the bitumen in the field, as determined by engineering principles, will have an effect on its physical attributes.
The performance of the bitumen is painstakingly attempted to be replicated over a period of five to ten years so that the developing performance of the bitumen may be understood.
The purpose of the testing and specifications for the Superpave system is to protect bitumen against the following three main types of damage which are Raveling, Fatigue cracking, and Thermal cracking.
At high, intermediate, and low temperatures, respectively, these defects manifest themselves.
The asphalt road is subjected to temperature tests across the entire scale, from fifty to one hundred and thirty-five degrees Celsius.
Measurements of the rheological characteristics of bitumen are carried out at the construction site using a bending beam rheometer and a direct tension tester during the winter months.
For any more information on bitumen in different grades suitable for different applications, feel free to contact our sales executives.
They will guide you and give you all the necessary information that you might need.
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