1、 How to prepare stable coarse particle vibration compaction test specimens for cement, lime, lime powder, and coal ash? Overview

With the continuous development of high-grade highway construction, the traffic volume is increasing, and the requirements for the technical level of high-grade asphalt pavement are constantly improving. The requirements for asphalt pavement design are also becoming stricter, and the requirements for construction equipment are also increasing. Considering the original compaction instrument method for obtainingbigThere is a certain gap between the data obtained from the dry density test method and the actual situation of vibration compaction in highway construction. Our company has jointly developed a new generation of vibration compaction molding machine with relevant research institutions. This instrument simulates the construction conditions of a vibration roller and uses vibration method to obtainbigThe relationship between dry density and moisture content, this equipment adopts an electromechanical integration control method, which has good reliability and simple operation.

2、 Scope of application

This method is applicable to the vibration compaction test of cement, lime, lime powder, and coal ash stabilized coarse-grained materials to determine the moisture content andbigDry density.

The nominal value of the experimental aggregatebigThe particle size value is controlled within 37.5mm.

3、 How to prepare stable coarse particle vibration compaction test specimens for cement, lime, lime powder, and coal ash? Technical Specifications

Voltage: 380V

1. Vibration motor power: 3KW

2. Lift motor power: 0.75KW

3. Excitation force: 6800~6900N, surface pressure is about 0.1MPA

4. Vibration frequency: 28-30HZ (adjustable)

5. The weight of the boarding system is 4.5KG/piece x 3, and the weight of the disembarking system is 5.5KG/piece x 6

6. Steel mold inner diameter 152mm, height 170mm, wall thickness 10mm

7. Steel mold ring inner diameter 152mm, height 50mm, wall thickness 10mm

8. The diameter of the cushion block inside the cylinder is 151mm and the thickness is 20mm

4、 Installation instructions

1. Make a solid foundation according to the size of the equipment base.

2. Connect the host and control power supply.

3. Press the power start button, then press the up or down button to observe if the motor direction is correct. If it is the opposite, switch the number of phases of the power supply.

4. The vibration motor rotates clockwise.

5、 Instrument and equipment

1. Vibration compaction molding machine: static pressure, excitation force, and frequency can be adjusted (the same equipment used to determine compaction standards by vibration method).

2. Cylindrical specimen mold

Steel mold, steel mold ring.

The above components can be fixed together with bolts.

VIHow to prepare stable coarse particle vibration compaction test specimens for cement, lime, lime powder, and coal ash? Sample preparation

1. Screen the aggregate and grade it according to the predetermined gradation. If the nominal value of the aggregate isbigIf the particle size is not greater than 37.5mm, prepare the material directly. If the content of particles larger than 37.5mm exceeds 10%, sieve them through a 37.5mm sieve and record the percentage of oversized particles after sieving.

2. On the day before the scheduled experiment, take a representative sample and measure its air dried moisture content. For fine-grained materials, the sample size should not be less than 100g; for medium grained materials, the sample size should not be less than 1000g; for various aggregates of coarse-grained materials, the sample size should not be less than 2000g. At the same time, the moisture content of lime and cement should be measured.

Determined according to the compaction standard testbigCalculate the weight of various aggregates and mix them according to the dry density, designed aggregate gradation, and volume of the specimen. The number of ingredients to be mixed is determined by the testing requirements.

7、 Sample making steps

1. Adjust the vibration parameters of the vibration forming machine, and generally choose a compaction condition with a surface pressure of about 0.1MPA, an excitation force of 6800~6900N, and a vibration frequency of 28~30Hz for stable inorganic binder pellets. Then carefully determine the vibration compaction of the mixture and the required size, and adjust the position of the scale on the vibrator of the vibration compactor accordingly.

2. Take one sample and lay it flat in a metal plate. Calculate the amount of water to be added to each sample based on the moisture content determined by the compaction standard test beforehand. Spray the water evenly on the sample and mix it thoroughly with a small shovel until it is in a uniform state.

The amount of water added can be calculated according to the following formula:

Mw=

Mn Mc Mn Mc

（ ＋ ）×0.01w－ ×0.01wn－ ×0.01wc

1+0.01wn 1+0.01wc 1+0.01wn 1+0.01wc

In the formula: the amount of water to be added in the Mw mixture (g);

The mass of aggregate in Mn mixture (g), its original moisture content is wn, which is the air dried moisture content (%)

The mass of cement or lime in Qc mixture (g), with an original moisture content of wc (%);

The required moisture content (%) of the mixture for W.

3. Add the required binders, such as cement, fly ash, etc., to the soaked sample and mix thoroughly with a small shovel, trowel, or other tool until uniform. For samples with added cement, the following compaction test should be completed within 1 hour after mixing. Samples that exceed 1 hour after mixing should be invalidated (except for lime stabilization and lime fly ash stabilization).

4. Connect the steel mold ring, steel mold, and steel mold bottom plate tightly, then place them on a solid ground. Divide the mixed material into four parts according to the quartering method, pour the mixture into them one by one, and use a wooden stick with a diameter of about 2cm to compact one side while pouring. After the mixture is loaded once, level its surface and press it slightly, then cover it with a pre cut piece of plastic paper. Place the steel mold and mixture on the steel bottom plate of the vibratory compactor, and fix the steel mold bottom plate and the vibratory compactor bottom plate together with bolts.

5. After aligning the vibration head with the steel mold, lower the vibrator to ensure that the vibration head is in close contact with the mixture inside the steel mold. Check the bolts and related connections on the vibration compaction forming machine to ensure that there are no items placed on the machine.

6. Activate the vibration compaction molding machine switch to start vibration compaction. Carefully observe the position change of the vibrator ruler on the vibration compaction molding machine, and immediately turn off the machine after 120 seconds.

7. Lift the vibration pressure head. Loosen the bolts on the bottom plate of the steel mold, and remove the steel mold together with the compacted mixture. After loosening the bolts, remove the steel mold collar. At this time, the top surface of the compacted mixture should be level with the upper edge of the steel mold.

8. Support the cushion block at the bottom of the steel mold, carefully place the steel mold and the mixture in the appropriate place, let it stand for a period of time according to the type of material, and then use a demoulder to push the compacted mixture out of the steel mold.

9. After the test piece is demolded or can be moved, it should be immediately wrapped in plastic film and placed in a curing room for curing. The curing conditions are the same as the static pressure method 2 in the specifications.

8、 Precautions and related instructions

1. For cement stabilized materials, the longer the interval between mixing with water and conducting compaction tests, the greater the hydration effect and hardening degree of cement. Therefore, it is required that the compaction test be completed within 1 hour after the experimental mixing with cement as the binder.

2. Due to the potential damage caused by vibration to the instrument, it is necessary to carefully check the tightness of the instrument bolts before vibration compaction. During operation, it is essential to follow the operating procedures and not be careless. The vibration compaction process is relatively short, and it is important to carefully observe whether the vibrator head has reached the jumping state. Do not let the vibration compaction molding machine run in a bouncing state for a long time.

3. For the mixture after vibration compaction, in order to prevent deformation or looseness, cylindrical specimens should not be immediately demolded. The time for demolding after vibration should be determined according to the structural type of the mixture;

Suspended dense structure mixture: 2-3 hours;

Dense skeleton structure mixture: 5-6 hours;

Bone and void structure mixture: 10-12 hours;

4. After the mixture is molded and its surface is roughly leveled, plastic paper should be laid on it, and then vibration compaction should be carried out. This is mainly done to prevent the fine slurry in the mixture from sticking to the vibration head. The adhesion of fine materials on the vibration head not only affects the vibration, but also easily causes unevenness on the surface of the specimen when the vibration head is lifted after vibration.

5. The mixing and loading of the mixture should be strictly carried out according to the quartering method. For semi steel base layer mixtures, segregation has a significant impact on the results of indoor tests.