With increasingly stringent global requirements for the long-term performance of road materials,asphalt aging research has become a core topic in materials science.Accurately simulating and evaluating the performance changes of asphalt after years of use is crucial for designing long-life pavements.Standardized preparation of accelerated aging residue samples is a key first step in ensuring reliable and comparable test data.

I.Why is Accelerated Aging Testing Necessary?

The aging of asphalt in the natural environment is a slow process involving oxidation,loss of volatiles,and physical hardening.To quickly obtain long-term performance data in the laboratory,researchers use accelerated aging tests,simulating the effects of natural aging over several years under controlled high temperature,high pressure,and ventilation conditions.The resulting residues are the direct indicator for evaluating the asphalt's resistance to aging and its remaining performance potential.

II.Standardized Preparation Process:From Aging to Molding

1.Aging Test Execution

The starting point for preparation is conducting a standard accelerated aging test.Currently,the most widely used method is the pressure aging vessel(PAV)test.This method places the asphalt film,which has undergone short-term aging(such as RTFOT treatment in a rotating thin film oven),into a high-temperature(typically 90-110°C)and high-pressure air(2.1 MPa)environment for a certain period of time(typically 20 hours)to simulate the long-term aging of pavement asphalt over 5-10 years.

The key international standard to be followed here is ASTM D6521,"Standard Implementation Procedure for Pressure Aging Vessels Accelerated Aging Bituminous Adhesives"or AASHTO R 28.This standard strictly specifies equipment parameters,sample containers,temperature and pressure control,and safety procedures,and is the cornerstone for ensuring consistent aging conditions across different laboratories worldwide.

2.Recovery and Treatment of Aging Residues

After the PAV test,the aged asphalt residues from multiple stainless steel pans must be carefully combined and recovered.This is typically done by heating(at a temperature strictly controlled to a minimum for easy pouring,usually not exceeding 163°C)and scraping to collect them into a single container.To ensure the residues are homogeneous,gentle and thorough stirring is necessary,but excessive stirring should be avoided to prevent the introduction of air bubbles or additional thermal aging.

3.Sample Casting and Conditioning

Based on subsequent performance testing requirements(such as Dynamic Shear Rheology(DSR),Bending Beam Rheology(BBR),Direct Tensile Rheology(DT),etc.),homogenized aged asphalt is cast into specific standard molds.

DSR specimen:A thin film of asphalt of a specific thickness is poured between two parallel or conical molds.

BBR specimen:A small beam specimen cast and trimmed to standard dimensions.

After casting,the specimen must be adequately conditioned under specified temperature and time conditions to eliminate thermal history and internal stress,bringing it to the stable state required for testing.

III.The Cornerstone of Quality Control:International Standards Throughout

Every step of sample preparation is guided by international standards.In addition to the ASTM D6521 standard for the aging process mentioned above,there are also detailed specifications for the sample molding stage.

For example,the preparation of test specimens for the rheological properties of aged asphalt must strictly adhere to the specific requirements regarding specimen size,casting method,and temperature conditioning in AASHTO T 315,"Standard Method for Determination of Rheological Properties of Asphalt Binders by Dynamic Shear Rheometer".This standard ensures that the prepared specimens are dimensionally accurate and defect-free,thereby guaranteeing that the rheological test data accurately reflects the material properties and allows for effective comparison globally.

Following these international standards means that our research results can be aligned with international cutting-edge advancements,providing solid and reliable data support for developing more resistant-aging modified asphalt and optimizing the compatibility of recycled asphalt.

IV.Towards a More Durable Road Future

Standardized accelerated aging residue sample preparation acts like a precise ruler,helping us measure the impact of time on asphalt materials.It is not merely a laboratory procedure,but a core link connecting materials research and development,performance prediction,and engineering practice.By rigorously adhering to international standards such as ASTM and AASHTO,we can extract reliable information from simulated"acceleration times,"thereby guiding the design of more durable,reliable,and cost-effective road structures.

Precise preparation,insight into the future.As research into the mechanisms of material aging deepens and global standards become increasingly unified,this standardized sample preparation method will continue to contribute significantly to improving the sustainability and resilience of road infrastructure.