The compaction density and Marshall stability test of asphalt mixture are important indicators to evaluate the performance of asphalt mixture in road engineering. The compaction density reflects the density of the mixture, which affects its strength and durability; The Marshall stability, on the other hand, evaluates the load-bearing capacity and deformation resistance of the mixture under the action of external forces. These two tests provide a scientific basis for road design and construction, ensure the stability and safety of the road surface, and are an important part of ensuring the quality of the project.
The density test of compacted asphalt mixture (volumetric method) aims to determine the relative density of the gross volume or the gross volume density of the asphalt mixture. This method is suitable for asphalt gravel mixtures with large porosity and large void permeable open-graded asphalt mixtures (0GFC) that cannot be determined by surface drying method or wax sealing method. The relative density of gross volume measured by this method can be used to calculate various volume indexes such as void ratio and mineral clearance ratio of asphalt mixture.
Electronic Balance - the maximum weight is less than 3kg, the inductance is not more than 0.18g, and the maximum weight is more than 3kg.
Calipers – used to measure the dimensions of the specimen.
1. Choose the right electronic balance to ensure that its maximum weight meets the requirements of the specimen quality.
2. Clean the surface of the specimen and weigh the air mass of the dried specimen to an accuracy of 0.1g or 0.58g. If the specimen is in a non-drying state, use an electric fan to blow it to a constant weight, and the drying method shall not be used.
3. Use calipers to determine the various sizes of the specimens, accurate to 0.01cm.
4. Calculate the gross volume according to the specimens of different shapes: the calculation formulas of cylindrical specimens and prismatic specimens refer to the relevant standards respectively.
After calculating the gross volume density, the theoretical density, porosity, asphalt volume percentage and other volume indexes of the specimen were calculated according to the relevant regulations. Referring to the ASTM D3203 standard, the gross bulk density is divided by the density of water at 25°C to obtain the relative density determined by the volumetric method.
The Marshall stability test is used to test the mix ratio design of the asphalt mixture or the construction quality of the asphalt pavement, especially the flooded Marshall stability test is used to evaluate the water stability of the asphalt mixture to test its ability to resist water damage.
Marshall Tester - should have the function of control device, recording load and displacement curves, divided into automatic and manual type. For asphalt mixtures on highways and primary roads, an automatic Marshall Tester is recommended.
Constant temperature sink - the temperature control accuracy should reach ±1°C, and the depth should not be less than 150mm.
Vacuum saturated containers, ovens, balances, thermometers, calipers and other auxiliary equipment.
Preparation
According to the standard molded Marshall specimens, the size must meet the specified requirements.
Use calipers to measure the diameter and height of the specimen, and calculate its density, porosity, and other indicators.
Adjust the Thermostatic Water Bath to the required test temperature, and the holding time is determined according to the size of the specimen.
Test procedure
Place the specimen in a Thermostatic Water Bath to keep warm.
Prepare the Marshall Tester and place the test piece between the upper and lower pressure heads.
The loading device is started, the load is applied at the specified loading rate, and the data is recorded.
The pressure-deformation curves obtained by means of an automated Marshall Tester or manually are used to determine the maximum load and flow values. The stability and flow values are the maximum load and the corresponding deformation of the specimen, respectively.
The compaction density and Marshall stability of asphalt mixtures are key indicators to evaluate their quality and suitability. Through standardized testing methods, the performance and durability of asphalt mixtures in road construction can be ensured. Future research should continue to optimize the detection technology, improve the accuracy of the test, and reduce the impact on the environment.