Natural Asphalt Analysis
Some types of asphalt are made by nature as a result of the slow change of Crude oil and evaporation of its volatile materials during many years. Such an asphalt is called natural asphalt and survives more than oil asphalts. Such an asphalt may exist in nature as a pure element (asphalt of the lake) such as asphalt lake of Behbahan in Iran and Trinidad asphalt lake in America or be extracted from mines (mineral asphalt). Natural asphalt is also known as Uintaite.
One of the ways of quality evaluation of asphalt is to analyze. Analysis of natural asphalt shows the quality, lasting and use of asphalt in different industries.
Many items will be calculated in asphalt analyze including mass color, powder color, softening point, moisture, penetration, ash, mesh, solubility, the amount of carbon, etc.
Measuring and analyzing some of the important items about mine asphalt is as follows:
Ash of natural Asphalt
shows the impurities of asphalt and is among the important parameters in the quality of natural asphalt but unfortunately, the inexperienced buyers ask the reason of its different cost whose answer is so simple: difference in other parameters of asphalt including density, carbon, etc. which are important for the quality evaluation of Natural Asphalt. These parameters are important in determination their cost and must not be taken for granted.
But natural asphalt in mines have a feature and its quality increases and decreases according to the amount of ash which is combined with it. For example, some asphalts have less than 50% ash which is among the best asphalts and it reaches to less than 10%, 15%, 20%, 30% and even 50% and the more its ash, the less its quality. Separation is more important which is a difficult step and lessons the quality and cost of asphalt.
The most important feature of natural asphalt which makes it be used in different scopes include:
Asphalt softening point is the thermal resistance of it. The more the softening point of asphalt, the higher its thermal resistance and its usage in warmer regions and the less the softening point, the less its thermal resistance and its usage in colder regions.
Penetration is the sensibility of asphalt to change of temperature and the relative hardness of asphalt will be measured in this way. The more the penetration, the softer the asphalt and the more into usage in colder areas.
Proper natural asphalt is a type of asphalt which has a good amalgamation with oil asphalt and after their combination, we will have a product whose feature is in line with road construction asphalts. The previous experiences have shown that such an asphalt must have a low melting point, high solubility in CS2 and low mineral ash.
50 to 200: Mesh
5% to 25% : Ash
%2.5≤ : Moisture Content
Carbon and Hydrogen
Measuring carbon and Natural Asphalt Hydrogen amount is done on low samples and it is important for the test to be accurate. The sample will be burnt completely in oxygen and 800 centigrade degree. The productions of this burning will pass over the copper oxide and the rest of carbon and hydrogen change into CO2 and H2O.
The amount of nitrogen in asphalt will be measured by the popular method Kjeldahl.
Sulfur is present in natural asphalt in different forms. In order to measure all the sulfur in the asphalt an amount of asphalt must be dissolved with a combination of water-less sodium carbonate and two parts of magnesium oxide and then they must be heated.
In order to measure the amount of sulfur in asphalt, which is in the form of sulfate, it must be dissolved in Hydrochloric acid and sediment it in barium sulfate and weigh the sediment. A number of organic sulfur results from the total sulfate weight minus mineral sulfur.
The amount of oxygen in asphalt will not be measured accurately. In order to measure it, first, we measure all the elements of asphalt sample according to the previous methods and consider their sum difference from 100 equal to oxygen percentage of asphalt.