Asphalt with sol-gel structure: It has low temperature sensitivity at high temperatures and good deformation ability at low temperatures.

Therefore, asphalt with this structure is mostly used for highway construction.

It is the ability of asphalt materials to resist viscous deformation under the action of external forces.

component; temperature

sticky asphalt

liquid asphalt

The greater the penetration, the smaller the viscosity of the viscous petroleum asphalt; The greater the standard viscosity, the greater the viscosity of liquid petroleum asphalt.

It is the property that the asphalt material deforms without being damaged under the action of external force. After the external force is removed, it can still maintain the deformed shape. →It reflects to a certain extent the self-healing ability of asphalt after cracking.

Composition; temperature; thickness of asphalt film layer

Ductility → The length that the asphalt sample stretches when it breaks when stretched in a water tank at a specified temperature at a rate of 50mm/min.

Refers to the degree to which the viscosity and plasticity of asphalt are affected by temperature changes. →Asphalt with high temperature sensitivity quickly becomes soft and flows when the temperature rises; when the temperature drops, it easily becomes brittle and damaged.

When the temperature rises and falls within a certain range and the viscosity and plasticity of petroleum asphalt change little, it means that the temperature stability of the asphalt is good.

Components

"Softening point" (the temperature at which asphalt goes from a solid state to "a certain viscous flow state {that is, the penetration value of asphalt at the softening point temperature is 800}"). →Measurement using the "ball and ball method": heating glycerin or water at a speed of 5C/min, the water temperature T (C) when a steel ball with f=9.53mm and G=3.5g droops 25.4mm.

"Penetration index PI":PI=30/(1 50A)-10, Where A=[Ig800-Ig(25°C,100g,5s)]/[T-25]. →The larger the PI value, the smaller the temperature sensitivity of asphalt.

In engineering, when using asphalt, talcum powder, lime powder or other mineral fillers are often added to reduce its temperature sensitivity.

The performance of asphalt remains stable (without significant deterioration) under the long-term combined effects of heat, air, sunlight and other factors.

Ultraviolet light; heat; water; oxygen; oxidizing agent; stress.

evaporation loss

penetration ratio

The smaller the evaporation loss rate or the larger the penetration ratio, the better the atmospheric stability of the asphalt, that is, the better the aging resistance.

The greater the penetration → the smaller the viscosity

The greater the ductility → the better the plasticity

The lower the softening point → the greater the temperature sensitivity (i.e. the worse the temperature stability (heat resistance))

Three major technical indicators

If the test temperature increases, the asphalt will become softer, so the measured penetration value will increase. Therefore, special attention should be paid to the test temperature during the asphalt penetration test (the standard temperature specified in the specification is 25°C)

① For parts in "warm areas, susceptible to sunlight or severe heat": In order to prevent the asphalt from being excessively softened by heat, → asphalt with "smaller markings" should be selected.

② In "cold areas" and in locations that are "exposed to the sun in summer and freezing in winter": not only softening by heat but also low-temperature embrittlement must be considered, → so it is appropriate to choose "medium grade" asphalt.

③ For some parts that are not easily affected by temperature (such as expansion joints, asphalt water stop wells): → You can choose asphalt with a "larger number".

④When there is a lack of asphalt of the required grade, asphalt of different grades can be blended with each other.

It is required to have good adhesion, temperature stability and atmospheric stability. Therefore, the softening point of the asphalt is required to be 20°C higher than the highest local roof temperature reached over the years to ensure that it does not flow during high temperatures in summer. But it should not be too high, otherwise it will easily become hard, brittle or even crack when the temperature is low in winter.

It is required to have high viscosity, good plasticity and toughness, but does not have high requirements for temperature stability and atmospheric stability.

"Asphalt with large ductility and moderate softening point" is a road engineering pavement material.

Reason: "Asphalt with a large ductility value" has good plasticity, so it is not easy to cause damage when deformed by force. "Asphalt with a moderate softening point" has the characteristics of not easily brittle at low temperatures and not easy to flow at high temperatures.

Therefore, it is not advisable to mix coal pitch into petroleum asphalt to improve its anti-corrosion properties.

liquid petroleum asphalt