The Asphalt Marshall Test is an important experiment to evaluate the performance of asphalt mixtures, which aims to analyze the degree of compaction of asphalt mixtures by determining their theoretical maximum relative density and porosity. The test uses a negative pressure vessel and vacuum method to ensure that the specimen is effectively controlled during the construction process, so as to optimize the performance of the asphalt mixture and improve the durability and safety of the pavement. This method is widely used in road engineering to ensure the construction quality and long-term stability of asphalt pavement.
Marshall test of asphalt pavement core samples
Purpose and Scope of Application
The Marshall test is mainly used to drill core samples from asphalt pavement to evaluate whether the construction quality of asphalt pavement meets the design requirements or to conduct road condition investigations. The diameter of the standard core sample drilling specimen is 100mm, and the height is 30-80mm. The diameter of the large drilled specimen is 150mm, and the height is 80-100mm.
Instrumentation and material requirements
The instruments and materials used in this method must comply with the relevant standard T0709 to ensure the accuracy and reliability of the test.
Methods and Steps:
1. Core sample drilling - drilling the core sample of compacted asphalt mixture pavement according to the method of "Highway Subgrade Pavement Field Test Regulations" (JTG E60).
2. Clean the specimen – Before the test, the specimen needs to be cleaned of the viscous oil, permeable oil and loose particles. For the core sample of multi-layer asphalt mixture, different layers should be separated by cooling and chiseling.
3. Specimen storage - specimens should be stored in a cool place to avoid deformation caused by high temperature.
4. Determination of density - if there is a lack of asphalt dosage, mineral mix ratio and density data, the theoretical maximum relative density of asphalt mixture should be determined according to T0711.
5. Determination of porosity and other indexes - the density of the specimen is determined by the prescribed method, and the volume indexes such as porosity, asphalt volume percentage, asphalt saturation and ore clearance ratio are calculated.
6. Marshall test - use calipers to determine the diameter and height of the specimen, carry out the Marshall test according to the prescribed method, and calculate the correction coefficient according to the measured stability of the test to obtain the stability of the standard height specimen.
Precautions
The height of the specimen may not meet the requirements of the standard, so the Marshall test method needs to be adjusted accordingly. In particular, the structural condition of the core sample of multi-layer asphalt mixture can be complex, so special care needs to be taken when separating to ensure the integrity of the specimen.
Theoretical maximum relative density test of asphalt mixture (vacuum method)
Purpose and Scope of Application
This method is suitable for determining the theoretical maximum relative density of asphalt mixture by vacuum method, which is used for asphalt mixture mix design, road condition investigation or pavement construction quality management. It is worth noting that this method is not suitable for asphalt mixture of porous aggregate with water absorption greater than 3%.
Instrumentation and material requirements
Balances – weighing equipment with an inductance of more than 5kg and 0.1g and less than 2kg and an inductance of 0.05g.
Negative pressure vessel – the right type for the number of specimens, with a rubber stopper and a transparent viewing window for air bubbles.
Vacuum negative pressure device - capable of generating negative pressure of 3.7kPa ± 0.3kPa.
Temperature control equipment - the temperature of the thermostatic sink is controlled at 25°C±0.5°C, and it is equipped with a thermometer.
Methods and Steps:
1. Specimen preparation- Samples are obtained from asphalt mixtures, the quantity should meet the requirements, and the samples should be properly treated.
2. Calibration of negative pressure vessels- Soak the negative pressure container in a constant temperature water tank and measure its quality.
3. Test procedure
The asphalt mixture specimen is loaded into a dry negative pressure container and the total mass is weighed.
Fill a negative pressure container with water at 25°C±0.5°C to completely immerse the mixture.
A vacuum vacuum device is used to evacuate until the predetermined negative pressure conditions are reached.
The buoyancy of the specimen is determined and the theoretical maximum relative density of the asphalt mixture is calculated.
Result calculation
Through the measured buoyancy and the mass of the sample, the theoretical maximum relative density of the asphalt mixture can be calculated, and the pavement construction quality can be evaluated and controlled on this basis.
conclusion
The above methods provide standardized processes and technical requirements for the detection of asphalt, and ensure the scientificity and accuracy of the construction quality and performance evaluation of asphalt pavement. These detection methods are not only suitable for daily construction quality management, but also provide important data support for the maintenance and management of asphalt pavement.
