Bitumen Penetration grading history:
The early beginnings of asphalt construction are traced, and some of the milestones with respect to the development of specifications and test methods for asphalt materials and Bitumen Penetration are recorded. Only the major sources of asphalt obtained from native deposits and from the refining of petroleum are considered. Comments are made on some of the first asphalt pavements, and on some of their advantages.
From 1878 to 1900 most of the asphalt used in the construction of sheet asphalt, penetration macadam and mixed macadam (asphalt concrete) was obtained from Trinidad Lake. Petroleum asphalts came into use about 1900. The development of test methods and specifications is reviewed from the first specification for asphalt based on the appearance of crude Trinidad asphalt and analytical tests to determine the amounts of bitumen insoluble organic and inorganic matter, to the 1903 penetration test method (for measuring consistency), the ductility test (for measuring adhesion and cementing characteristics), the loss on heating test and the penetration of the residue (to determine the stability of asphalt during heating and mixing), solubility in carbon disulphide and petroleum naphtha, and a water resistance test.
A 1918 bulletin (No. 691) giving typical specifications for bituminous road materials is outlined. Standard methods of test are reviewed, and a list of test methods for bituminous and related materials are tabulated. Major steps in the development of standard specifications for asphalt are noted. Various types of liquid asphalts are described, and the development of, and tests for emulsified asphalts are outlined. Methods of design and control of asphalt paving mixtures are briefly covered.
ASTM for road industry (Bitumen Penetration):
ASTM Committee D04 has 100 years history on Road and Paving Materials. Generally corresponds to the history of development of paved roads suitable for automobiles in U.S.A. There were just 6,000 miles “improved roads” in there. In 1903 this committee came into existence. According to 2001 highway statistics compiled by Federal Highway Administration, there are 3.95 million miles improved roads in United States. In addition, 2.46 million miles have some sort of bituminous surface.
more than 100 years, Committee D04 has made significant quota to road paving through the development of test methods. Also used specs for design, construction, and repair road pavements.
The committee has met challenge of keeping pace with growing demands on highways in terms of increasing traffic volume and loads. Also even increasing tire pressure.
Asphalt testing conducted primarily to determine the suitability of a material to be used as a flux for natural lake asphalts . Road oils derived from the distillation of petroleum crude were used mostly as dust palliatives for unsurfaced roads. The so-called “artificial” asphalts (harder residue obtained from refining petroleum) were being introduced as binders for hot-mix asphalt pavements and were significantly less expensive than Trinidad and other natural asphalts. The suppliers of Trinidad asphalt fought very hard to stop the influx of the “cheap artificial product.” In fact, A.W. Dow, who was the asphalt inspector for the District of Columbia, was ordered by the congressional committee responsible for district affairs to stop using petroleum asphalt in road building or face dismissal. It appealed to the courts and won a decision permitting the broadening of the binder specification to include Bitumen Penetration also other petroleum asphalts.
The first standard ASTM specifications developed for penetration graded asphalt cements for paving purposes were adopted in 1921, after many years of using tentative or provisional standards. The number of penetration grades was reduced from 10 to five in 1968 following the “skip-grading” concept adopted by AASHO in 1960.
All of the early tests for consistency (viscosity) of bituminous binder, such as the penetration test, were empirical tests. In 1937, Committee D04 sponsored a symposium on using absolute viscosity units to measure the consistency of bituminous materials. Despite this early interest in using fundamental tests, little progress was made in this area until the late 1950s and 1960s. Committee D04 adopted two fundamental viscosity tests in 1963: D 2170, Test Method for Kinematic Viscosity of Asphalts (Bitumens), and D 2171, Test Method for Viscosity of Asphalts by Vacuum Capillary Viscometer. However, viscosity-graded asphalt cement specifications using these test methods were not adopted by ASTM until 1975.
In the late 1980s, the Strategic Highway Research Program (SHRP) initiated a $50 million, five-year research program to develop performance-based asphalt binder tests and specifications. On completion of this project in 1993, a PG asphalt binder specification and related tests were recommended by SHRP. Committee D04 has adopted most of the new binder test methods.
Committee D04, an emphasis was placed on tests and specifications for individual materials. The direct involvement of committee in designing bituminous mixtures did not begin until the late 1940-50s. Prior to that, individual states and organizations were using either recipe-type mixtures or their own mix design and quality control tests. The first and most widely used mix design test was the Hubbard-Field test developed by Hubbard and Field in the early 1920s.
Although this method filled the early need for a rational mix design procedure, it was only useful for sand mixtures with all of the aggregate passing the No. 4 sieve. There is some methods for better mix design procedures.Hveem method based on surface area or surface capacity was developed in California by Francis Hveem, and Marshall method, based on a testing device developed by Bruce Marshall of Mississippi Highway Department. It was researched and adopted by U.S. Army Corps of Engineers. A gyratory testing machine (GTM) was later developed by Engineers for conducting mix designs.
There was a need to improve the precision and interchangeability of mix design test results from different laboratories, so Committee D04 adopted a standardized version of several of these procedures. Hubbard-Field test adopted in 1952, Hveem and Marshall methods adopted in 1958, also GTM method adopted in 1974. Committee D04 is in process of adopting the Superpave mix design method developed by SHRP, which uses a Superpave gyratory compactor.
Bitumen Penetration Grades Analysis: