The meaning of the PI value of asphalt

See page 21 of \"Q&A on Asphalt Production and Application Technologies\".

This post was last edited by pjf_pll on 2010-8-30 at 22:23. This refers to the penetration index of asphalt, with the measurement method specified on page 21 of \"Questions and Answers on Asphalt Production and Application Technology\". Asphalt can be mainly divided into three types: coal tar pitch, petroleum asphalt, and natural asphalt. 1. Coal tar pitch: Coal tar pitch is a by-product of coking; it is the black substance that remains in the distillation vessel after the distillation of tar. It differs from refined tar only in terms of physical properties, with no clear boundary; the common classification method is to consider substances with a softening point of 26.7°C or below (using the cube method) as tar, while those with a softening point above 26.7°C are considered asphalt. Coal tar pitch mainly contains non-volatile compounds such as anthracene, phenanthrene, pyrene, and ■. These substances are toxic, and the properties of coal tar pitch vary depending on the levels of these components. Temperature changes have a significant impact on coal tar pitch; it tends to become brittle in winter and soft in summer. It has a special smell when heated ； After being heated to 260°C for 5 hours, components such as anthracene, phenanthrene, pyrene, and ■ will volatilize. II. Petroleum asphalt: Petroleum asphalt is the residue remaining after the distillation of crude oil. Depending on the degree of refinement, it appears as a liquid, semi-solid, or solid at room temperature. Petroleum asphalt is black and shiny, with a high temperature sensitivity. Since it was distilled to temperatures above 400°C during the production process, it contains very few volatile components; however, there may still be hydrocarbons from polymers that have not evaporated, and these substances are more or less harmful to human health. III. Natural asphalt: Natural asphalt is stored underground; some forms mineral deposits or accumulates on the Earth’s surface. Most of this asphalt has undergone natural evaporation and oxidation, and generally contains no toxins anymore. Asphalt materials are divided into two main categories: natural asphalt and tar asphalt. Earth asphalt is further divided into natural asphalt and petroleum asphalt; natural asphalt is the residue left after oil seeps to the surface and is exposed to the elements and undergoes evaporation over time ； Petroleum asphalt is a product obtained by subjecting the residue oil remaining from the refining of petroleum to appropriate processing. Tar pitch is a product obtained by further processing the tar derived from the dry distillation of organic materials such as coal and wood. The asphalt used in engineering is predominantly petroleum asphalt, which is a mixture of complex hydrocarbons and their non-metallic derivatives. Typically, the flash point of asphalt ranges from 240°C to 330°C, and its ignition point is about 3°C to 6°C higher than its flash point; therefore, the construction temperature should be kept below the flash point.

Reply to 3# pjf_pll: He is referring to the penetration index of asphalt

The penetration index is a parameter that indicates the temperature sensitivity of asphalt binders, reflecting the degree to which penetration changes with temperature; it is calculated using the penetration values at different temperatures according to specified methods. It can be found using the asphalt penetration and softening point on a pre-drawn nomogram. It can also be calculated using a formula: PI = [30/(1+50A)] – 10, where A is the penetration-temperature sensitivity coefficient, which can be determined easily from penetration and softening point values. It can also be obtained by performing a regression A on the penetration values at three or more different temperatures. 　　The penetration index can also be used to indicate the colloidal type of asphalt. Soluble PI+2. As PI increases, the elasticity and thixotropy of asphalt increase. Most oxidized asphalts are of the sol-gel type.