The main technical properties of petroleum asphalt are:
1) Viscosity.
The viscosity of petroleum bitumen is also known as viscosity. Viscosity should be expressed in absolute viscosity, but because of its complex measurement method, the relative viscosity (conditional viscosity) is commonly used in engineering to express viscosity, and the viscosity is expressed by penetration degree for petroleum asphalt using viscosity (semi-solid or solid), and viscosity is expressed for liquid petroleum asphalt.
Plasticity. Plasticity refers to the property that petroleum asphalt is deformed under the action of external force without destruction, and can still maintain the shape after deformation after removing external force. The plasticity of petroleum bitumen is expressed by ductility. The greater the ductility, the better the plasticity.
Temperature sensitivity.
Temperature sensitivity refers to the properties of petroleum asphalt that vary in viscosity and plasticity with temperature fluctuations. Since bitumen is a polymer amorphous thermoplastic substance, it does not have a certain melting point. Temperature sensitivity is expressed in terms of softening point indicators. Because the asphalt material has a certain interval from the solid state to the liquid state, it is stipulated that one of the states is used as the starting point for the transition from the solid state to the viscous flow state, and the corresponding temperature is called the softening point of the asphalt. In addition, the brittle point of asphalt is another index that reflects the temperature sensitivity, which refers to the corresponding temperature of a specified state in the process of asphalt from high elastic state to glass state, which mainly reflects the low-temperature deformation ability of asphalt.
Atmospheric stability.
The ability of petroleum asphalt to resist aging under the long-term combined action of atmospheric factors such as heat, sunlight, oxygen and humidity is called atmospheric stability, which is also the durability of asphalt materials. The atmospheric stability of petroleum bitumen is evaluated by the percentage of heating evaporation loss and the ratio of penetration before and after heating.
Grade division of petroleum bitumen.
Petroleum bitumen is divided into grades according to the penetration index, and the grade number is about the average value of the penetration. The relationship between the grades and main properties of commonly used construction petroleum asphalt and road petroleum asphalt is as follows: the higher the grade, the smaller its viscosity (the greater the penetration), the greater the plasticity (i.e., the greater the ductility), and the lower the temperature stability (i.e., the lower the softening point).
The main property characteristics of coal pitch.
1) Overview.
Coal pitch, also known as coal tar pitch, is a type of asphalt that is extracted from coal tar. It is an important product in the process of coal tar processing and has unique physical and chemical properties. Understanding the main properties and characteristics of coal asphalt is of great significance for its application in industry, construction, transportation and other fields.
2) Physical properties.
1.Color: The color of coal pitch is usually dark brown or black, and its color shade is related to the nature of the raw coal, the coking process and the treatment method.
2.Density: The density of coal pitch is slightly higher than that of petroleum asphalt, generally at 115-1.25g cm.
3.Viscosity: Coal pitch has a higher viscosity and poor fluidity, which makes it a certain advantage in some applications.
4.Volatility: Coal pitch is highly volatile, which is also a problem that needs to be paid attention to during processing and storage.
3) Chemical properties.
1.Composition: Coal pitch is mainly composed of polycyclic aromatic hydrocarbons, fused aromatic hydrocarbons and asphaltenes. Among them, polycyclic aromatic hydrocarbons and fused aromatic hydrocarbons are the main components of coal pitch, which have high thermal and chemical stability.
2.Reactivity: Polycyclic aromatic hydrocarbons and fused aromatic hydrocarbons in coal pitch have high reactivity and can participate in a variety of chemical reactions, so they have certain application value in some fields.
3.Corrosiveness: Coal pitch has a certain corrosiveness, and has a certain corrosive effect on both metallic and non-metallic materials. Therefore, it is necessary to pay attention to protective measures during use.
Identification of coal pitch and petroleum asphalt.
Coal pitch and petroleum pitch can be distinguished by the following methods:
Determination of density. Greater than 11 is coal pitch;
Burn test. The smoke is yellow and has a pungent smell for coal pitch;
Knocking on the block asphalt, which is brittle (poor toughness) and has a crisp sound, is coal asphalt. The elastic and hoarse ones are petroleum asphalt;
Dissolve the asphalt with gasoline or kerosene, drop the solution on the filter paper, the inside is black and the outside is brown, the two circles of spots are coal pitch, and the brown evenly dispersed spots are petroleum asphalt.