Recently, our company has compiled some information regarding asphalt aging.The main causes of asphalt aging can be summarized into two major categories:physical hardening and chemical aging.This is a complex process involving multiple factors.

This is also one of the main reasons why asphalt pavements lose their flexibility and crack over time.

I.What are the main causes of aging?

1.Oxidation reaction:

Core mechanism:The active components in asphalt(especially aromatic compounds and resins)react with oxygen in the air,generating more polar oxygen-containing functional groups(such as carbonyl and sulfoxide groups).

2.Volatilization:

During heating,mixing,and construction,the light oil components in the asphalt volatilize.

The more volatilization occurs,the harder the asphalt becomes.

High temperatures and prolonged heating significantly exacerbate this process.

High temperatures accelerate:

Oxidation reactions.

The evaporation process.

The higher the temperature and the longer the duration,the more severe the aging.

3.Photoaging(Ultraviolet Radiation)

Ultraviolet rays in sunlight can damage the molecular structure of asphalt.

This mainly occurs in:

The asphalt film on the road surface.

It usually only affects the surface layer,but can lead to:

Surface hardening and cracking.

4.Effects of Water and Environmental Media

Water,acid rain,salt spray,and other environmental media:

Promote oxidation.

Damage the adhesion between asphalt and aggregates.

Indirectly accelerate aging.

5.Repeated Loading and Microstructural Changes

Under traffic loading:

The internal structure of the asphalt gradually rearranges.

This causes the material to exhibit:

Increased stiffness.

Decreased fatigue performance.

6.Summary of the Aging Process Stages:

Stage 1:Aging during construction(short-term aging)

Main locations:Asphalt storage tanks,mixing plants,transportation process,paving and compaction.

Dominant factors:High temperature(causing volatilization and intense oxidation).

Stage 2:Aging during service life(long-term aging)

Main locations:Paved road surfaces.

Dominant factors:The long-term combined effects of oxygen in the environment,temperature cycles,ultraviolet radiation,water,and traffic loading.

II.So how do we solve this problem?

The RTFO/RTFOT(Rolling Thin Film Oven Test)is a standard laboratory method(ASTM D2872/AASHTO T240)used to simulate the short-term aging of asphalt that occurs during asphalt mixing and paving.

1.The purpose of the Rolling Thin Film Oven Test is:

To simulate the short-term thermal aging process of asphalt during the mixing,transportation,and paving stages of construction.

2.RTFO/RTFOT primarily simulates three short-term aging mechanisms:

(1)Oxidative Aging

•Asphalt molecules react with oxygen

•Aromatic compounds and resins→asphaltenes

•Leads to hardening of the asphalt

(2)Volatile Aging

•Light oil components volatilize at high temperatures

•The content of light components in the asphalt decreases

(3)Thermal Effects Accelerate Aging

•High temperatures significantly increase the reaction rate

•Shortening the test time can reflect the aging results during construction

3.RTFO Measurement Results

What is the significance of the test results?

Asphalt aged by RTFO/RTFOT is commonly used for subsequent performance evaluation:

•Mass loss(%)–caused by volatilization and oxidation.

Excessive mass loss=excessive volatile matter→potential durability problems.

•Changes in physical properties–viscosity,penetration,softening point,DSR parameters.