1, the core sample can only be taken after the curing period, otherwise the cement will not reach the strength and the crushed stone will not bond. It usually takes 7 days to core. If the coring is unsuccessful, it means that the paving water is not in place when it is stable, or the base is unqualified.

2. After paving is stable, it shall be maintained in time. Don't let vehicles walk on it, or the lower part will be good after coring, but the surface will be hairy or loose, which will affect the acceptance.

3. When sampling, the core should be drilled at an appropriate position. If it is not drilled to the bottom of the cement stabilized base, the core sample will not be lifted.

4, drilling to the end, can not lift the core sample, can not form a whole, indicating that the amount of cement is small, need to do it again.

5. The coring of water-stabilized macadam layer mainly detects the thickness, compressive strength, integrity and compactness of the core sample, and at the same time, it can identify the gradation of macadam through the core sample, which can be avoided to a certain extent by good protection.

Extended data:

Composition design of cement stabilized macadam mixture;

Road materials such as cement, fly ash, stabilized macadam, sand and stone chips are used as cement stabilized macadam base.

First of all, through a certain number of raw material tests, laboratory mix design and compaction tests to determine the maximum dry density and the best water content. Then, the specimens were made according to this ratio, kept moist for 6 days at the specified temperature, and soaked in water for 65438 0 days, and then the unconfined compressive strength test was carried out.

The following picture shows the heavy compaction test report of cement 4%, fly ash 10% and graded crushed stone 86%.

Experiments show that:

(1) Through the test of two kinds of mixture ratios with sand, crushed stone and cement as the aggregate and fly ash, crushed stone and cement as the aggregate, it is found that the cement stabilized mixture mixed with fly ash not only has good workability, but also is easy to form, and the formed sample has good appearance and high 7-day average strength.

⑵ The 7-day unconfined compressive strength of lime-soil specimens with different proportions is about 0mpa, while the 7-day unconfined compressive strength of water-stabilized specimens with different proportions is between 4 and 7 MPa.

(3) After several freeze-thaw cycles, the compressive strength of lime-soil specimens with different proportions is almost zero; However, the strength of water-stabilized specimens mixed with cement and fly ash can still be measured after 10 freeze-thaw cycles.

Through observation and analysis, the slab performance of lime-soil base with different proportions is poor, and the dry shrinkage and temperature shrinkage coefficients are high. After the base surface is soaked in water, its strength is reduced. Under the repeated action of driving load, it is easy to be chewed into powder by the surface material, and the infiltrated water is easy to mix with mud and flow away, gradually hollowing out the surface layer, causing the oil surface to sink, crack and fall off, which is the main cause of asphalt pavement diseases.

The water-stabilized base composed of cement, fly ash, gravel, sand and stone chips has the characteristics of high strength, thin surface layer, good plate, good water stability and good frost resistance, which just makes up for the defects of lime-soil base, thus greatly improving the service life of asphalt concrete roads.

Construction method

Problems in construction:

First check the subbase and recheck the elevation of control piles.

Before laying cement stabilized macadam, the subbase should be cleaned and sprayed with proper amount of water to keep it moist.

Mixing adopts factory centralized mixing. Before using the plant mixing equipment, the plant mixing equipment and various metering systems should be debugged to make the water content, aggregate gradation and cement content of the mixed mixture meet the matching requirements, so that the machine can operate normally and the output of the mixer is consistent with the paving production capacity used.

When paving and rolling, the paving coefficient is between 3 and 5. The principle of "rather high than low, rather scraping than mending" must be implemented in the construction, and all construction projects should be completed before the final setting of cement. After rolling, the compactness test shall be conducted immediately. If the test result is not up to standard, roll again.

In general, cement stabilized macadam can not be constructed until 24 hours after the operation is completed. The interval between it and the kerb should not be too long, otherwise, after the mixture forms the slab, the slab will become hard, which will increase the construction difficulty, and it is easy to destroy the integrity of the slab by knocking the slab.

The curing time shall not be less than 7 days. During this period, vehicles are prohibited from passing, and they are maintained with sprinklers 2~4 times a day to keep them moist.

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