civil engineering-->>ASPHALT

ASPHALT

asphalt	A dark brown to black cementitious material in which the predominating constituents are bitumens, which occur in nature or are obtained in petroleum processing.
asphalt cement	A fluxed or unfluxed asphalt specially prepared as to quality and consistency for direct use in the manufacture of bituminous pavements, and having a penetration at 25° C (77° F) of between 5 and 300, under a load of 100 grams applied for 5 seconds.
bitumen	A class of black or dark-colored (solid, semi-solid or viscous) cementitious substances, natural or manufactured, composed principally of high molecular weight hydrocarbons, of which asphalts, tars, pitches, and asphaltenes are typical.
flux	A bituminous material, generally liquid, used for softening other bituminous materials.

This section uses the generic term, "asphalt binder", to represent the principal binding agent in HMA. "Asphalt binder" includes asphalt cement as well as any material added to modify the original asphalt cement properties. The term "asphalt cement" is used to represent unmodified asphalt cement only.

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civil engineering-->>Asphalt Binder Modifiers

Asphalt Binder Modifiers Some asphalt cements require modification in order to meet specifications. Asphalt cement modification has been practiced for over 50 years but has received added attention in the past decade or so. The added attention can be attributed to the following factors (Roberts et al., 1996): Increased demand on HMA pavements . Traffic volume, loads and tire pressures have increased substantially in recent years, which can cause increased rutting and cracking. Many modifiers can improve the asphalt binder's stiffness at normal service temperatures to increase rut resistance, while decreasing its stiffness at low temperatures to improve its resistance tothermal cracking. Superpave asphalt binder specifications . Superpave asphalt binder specifications developed in the 1990s require asphalt binders to meet stiffness requirements at both high and low temperatures. In regions with extreme climatic conditi...

civil engineering-->>Determinacy, Indeterminacy and Stability of Frames

Determinacy, Indeterminacy and Stability of Frames : Structural engineers must be able to apply judgment rather than stated rules. The most important aspect of structural design is not the ability to apply formulas or manipulate mathematics. The most important skill for the structural engineer is to be able to stand back, look at a drawing or sketch and determine whether a structure is stable, and if it is stable, to be able to determine how it will carry the applied loads. For a very complicated structure this might be more difficult and a computer can provide some help, but ultimately it is the skill and concern of a good structural engineer which produces good structural designs which have integrity. Another important closely related skill is the ability to determine whether, and to what degree, a structure is statically indeterminate. There really aren’t many rules and rules may be difficult to apply in any case. For this reason, we need experience. A skilled structural...

civil engineering-->>Properties of Bitumen

Properties of Bitumen Adhesion : Bitumen has the ability to adhere to a solid surface in a fluid state depending on the nature of the surface. The presence of water on the surface will prevent adhesion. Resistance to Water : Bitumen is water resistant. Under some conditions water may be absorbed by minute quantities of inorganic salts in the bitumen or filler in it. Hardness: To measure the hardness of bitumen, the penetration test is conducted, which measures the depth of penetration in tenths of mm. of a weighted needle in bitumen after a given time, at a known temperature. Commonly a weight of 100 gm is applied for 5 sec at a temperature of 77 °F. The penetration is a measure of hardness. Typical results are 10 for hard coating asphalt, 15 to 40 for roofing asphalt and up to 100 or more for water proofing bitumen. Viscosity and Flow : The viscous or flow properties of bitumen are of importance both at high temperature during processing ...

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