Asphalt CEMENT Flashcards
Since when Asphalt have been used?
since 3500 BC
What is asphalt cement?
Viscous cementitious material composed primarily of high molecular weight hydrocarbons.
What is asphalt concrete?
asphalt cement of asphalt cement, mineral agg., and possibly some admx.
Asphalt cement is a bituminous material. Bitumen occurs ___?
Naturally: as rock asphalt and lake asphalt
Industrially: leftover when lighter constituents of crude oil are distilled away during refining.
What are the main properties of asphalt cement?
- Waterproof
- ability to adhere to agg.
- viscoelastic material that depending on T can be either solid or liquid
What are the 3 methods to go from solid asphalt cement to liquid asphalt cement? (control time frame of liquid asphalt)
- Melting
- Dissolving
- Emulsifying
Describe the melting process of asphalt cement
heating above 140°C (if lower than 140, asphalt cement becomes solid)
Describe the dissolving process of asphalt cement
Controlling setting time with type of petroleum solvent. (this process is called cutting back). Hardening occurs as the solvent evaporate.
Describe the Emulsifying process of asphalt cement
Dispersing the asphalt cement in water. Asphalt and water don’t mix but emulsifying agents such as soaps, fine clay make them mixable (this mix results –> fluid=emulsified asphalt). After, water evaporates and asphalt particles recombine.
How do we differentiate asphalt?
with their physical & rheological properties
what are the composition of asphalt cements?
In general; 80-87% carbon, 9-11% H, 2-8% O, 0-1% Nitrogen (azote)
What are the 3 components of asphalt cement and their contribution to it?
- Oil (viscosity and fluidity)
- Asphaltene (Strength and stifness)
- Resin (Adhesion and ductility)
The oil acts as a solvent for the ____.
The oil acts as a solvent for the resin. (oil dissolve resins)
The ___ acts as a solvent for the asphaltenes.
The resin acts as a solvent for the asphaltenes. (resin dessolve asphaltenes)
How can the temperature decrease the viscosity of the asphalt cement?
By increasing the T, asphaltenes become more soluble in resins, which in turn become more soluble in the oils. Then the material becomes less viscous.
How can the temperature increase the viscosity of the asphalt cement?
By decreasing T, asphaltene becomes less soluble, form micelles, and the material becomes more viscous.
What is the glass transition temperature ?
Tg= 140°C; separates the solid and liquid transition of asphalt cement
asphalt is a thermo____ material. +definition of the word
Thermoplastic (very sensitive to T)
When do you have a newtonian fluid?
when T>140 °C (liquid–> Flexible)
When do you have a visco-elastic solid?
When T<140°C (the structure is effectively frozen and the material becomes rigid and brittle)
What is the age hardening phenomenon?
Asphalt cement hardens and becomes less ductile (Volatilization of lightweight carbon and oxidization by reacting with oxygen)
What are 2 artificial aging method to evaluate changes due to aging in asphalt cement?
- ASTM D-2872 (rolling thin film oven [RTFO])
- AASHTO provisional standard PP1: previously aged in RTFO is exposed to high P and T.
How did Asphalt cement have been traditionnaly graded?
Penetration
Viscosity
Performance grading
What is the PEN test?
Needle at T=25deg C
In the PEN test, if the gauge read 290, what is the penetration?
PEN=29mm
the higher the penetration #(PEN grade–>gauge reading), the _____.
the higher the penetration #, the lower the viscosity.
What is the viscosity grade?
AC–> viscosity asphalt cement
AR–> Viscosity on aged residue
the higher the number of poises, the higher ____.
the higher the number of poises, the higher the viscosity.
What is the PG?
Performance grading is penetration/viscosity grading with properties and conditions of the asphalt cement
what does PG XX YY represent?
XX= 7 days maximum pavement T, 52 to 70 deg C
YY= minimum expected pavement temperature, -16 to -40 deg C
PG 64-16
7 days max pavement T during summer is 64deg C and minimum pavement T during winter is -16deg C
What are the 3 things that asphalt cement stiffness depend on?
Temperature
Loading rate
Loading duration
Low temperature and/or short duration behavior?
Elastic behviour
High temperature and/or long duration behaviour?
Viscous behaviour; Approaches a viscous Newtonian fluid % stiffness approaches (S) 3*viscosity/time of aging
Low temperature and/or short duration behaviour?
Elastic behaviour (S=E)
Intermediate loading time behavior?
elastic + viscous, stiffness decreases nonlinearly
