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In the construction process, in order to increase the quality of concrete projects, the concrete ratio will be fine-tuned according to the actual situation at the construction site, so in order to detect the design strength of concrete, the practice of a simple method is to produce concrete sampling test, and the production of concrete sampling good or bad, whether the project can be successfully completed and accepted, so how to make a good concrete samples? And what matters should be noted?
How to take concrete samples
Concrete samples production process to comply with the following requirements
1. make a sample of the mold disassembly. Clean slag. Assembling process should be carefully. The non-vertical degree of each adjacent surface after assembling should not be more than ±0.5°. The mold release agent should be painted evenly. 2.
2. Before pouring concrete, the samples personnel should carefully check the mix ratio sheet. The construction area on the concrete ticket. The concrete strength, etc. shall be consistent with the design requirements.
3. After the mixer truck enters the construction site, its slump shall be tested in time, and each truck shall be tested. The test material shall be randomly sampled from 1/4 to 3/4 of the mixer truck.
4. Before making a sample, concrete clinker shall be selected jointly in accordance with the specification requirements and in the presence of the supervisor. The test material shall be randomly sampled from 1/4 to 3/4 of the mixer truck.
5. After the sample volume is selected, the sample shall be mixed evenly by hand twice.
6. clinker in two layers into the mold pounding, each layer of roughly equal thickness. The steel pounding rod for inserting pounding is 600mm long, 16mm in diameter and the end should be rounded. Pounding is carried out evenly from the edge to the middle according to the spiral direction. The pounding rod should be kept vertical and should not be tilted when pounding. The number of pounding per layer should be based on the cross-section of the test piece, the general standard sampling ≧ 27 times. After inserting and pounding, scrape off the excess concrete, the surface of the test piece should be 2 ~ 3 mm higher than the test mold.
7. In the plug pounding at the same time with a flat shovel repeatedly penetrate, to exclude the air within the sampling. When finishing the sample surface, pay attention to the fullness of the material slurry, so as not to let the concrete appear depressed due to plastic deformation.
8. After the sample is formed, it is often placed in situ or in the open air before final setting. In order not to make the water evaporate and affect the hydration rate of cement, the sample should be covered tightly with black plastic sheet or sack in time.
9. before the final set (3 ~ 4h after the specimen is ready), the surface will be smoothed with an iron plate, and according to the requirements of the testing unit, with iron nails inscribed on the surface of the sample: concrete strength. Production time. Part and other information.
10. samples hardening after demoulding, should be sent to the temperature 20 ± 3 ℃. Humidity of more than 90% of the standard curing room for maintenance. If the Concrete sampling is cured under the same conditions, the surface should be covered after forming, and the demoulding time of the specimen should be the same as the demoulding time of the actual member.
Concrete Sampling Standards
Concrete mixing plant production of concrete samples production should pay attention to what? Here is a look at some of the contents we summarize for you:
1. Before molding, the size and angle of the test mold (150mm side length) should be checked, and the test mold should not be deformed. The inner surface of the test mold should be coated with a thin layer of mineral oil or other release agents that do not react with the concrete.
2. Concrete samples concrete should be mixed in as short a time as possible after the molding, generally not more than 15 minutes.
3. test cast-in-place concrete or precast concrete, test forming method should be the same as the actual method used.
4. Concrete samples of the concrete mix should be at least three times with a shovel and then mixed back and forth.
5. The test mold should be moved carefully after it is made, so that it does not vibrate significantly, after the initial setting, that is, after “hardening”.
6. Do not think that the long vibration can be dense or high strength during the production process, but vibrate strictly according to the above method. The test mold should be tightly packed and squeezed before use.
7. each time it is appropriate to make two groups (6 test molds), one of which is the standard raising sampling.
Concrete sampling is good or bad, the human factor also plays an important role, so NFLG recommends choosing a technical level. Strong sense of responsibility. Have the patience of the staff to operate, after the staff, do not change frequently.