7.
If the test block is cured under the same conditions, its surface shall be covered after forming.
In a sense, the quality of making concrete test blocks determines the quality of a project.
After the formwork is removed, the test piece shall still be cured under the same conditions.
After tamping, gently tap around the test formwork with a leather hammer until the hole of the tamping rod disappears, scrape off the excess concrete, and the surface of the test piece shall be 5mm higher than the test formwork.
Precautions in the manufacturing process 1.
Each layer shall be tamped The number of times is generally 25.
The surface of the test pieces shall be kept wet and shall not be directly washed by water.
[11] It means that after the test block is hardened and removed, it shall be sent to a standard curing room with a temperature of 20 ± 2 ℃ and a humidity of more than 95% for curing.
Another reason is that the test value of a single test block is inaccurate due to too fast loading during the test..
Enter the chip content: manufacturing date and number, concrete strength grade, manufacturing time, position and other information.
Therefore, it is particularly important to do a good job of concrete test block.
The manufacturing time and number of the test pieces shall be marked in time.
When tamping the bottom layer, the tamping rod shall reach the bottom surface of the test mold; when tamping the upper layer, it shall penetrate the lower layer for 2 ~ 3cm.
4.
Only one group (3 for each group) shall be made for mortar test block and mortar in the same tray × seventy point seven × 70.7 cube test piece) the standard curing test piece shall take the same mortar strength grade, the same mix proportion, the same raw material, each floor or 250m3 masonry mortar as a sampling unit, and the retention of standard curing test pieces per sampling unit shall not be less than one group.
The tamping shall be carried out evenly from the edge to the center in the spiral direction.
The size and size are inappropriate, and shall meet the requirements of specifications and drawings.
3/4.
The sampled and mixed concrete shall be formed as soon as possible after mixing, generally not more than 15 minutes.
The strength increases the fastest in the first 7 days, and there is basically no increase in strength after 28 days.
(3) In case of any change in materials, mix proportion or construction method, it shall be retained separately according to the above provisions.
Impermeable concrete test blocks (1) when the continuous pouring amount of concrete is less than 500m3, two groups (12) of impermeable test blocks shall be retained.
When the temperature decreases, the time can be appropriately extended, but it should not exceed two days and nights, and then the test piece is numbered and the formwork is removed.
The specific methods are as follows: [certain] The designated personnel shall take the post, and the operators shall not change frequently.
[three checks] Before pouring and tamping concrete, the sampling personnel shall carefully check whether the construction parts and concrete strength grade on the mix proportion sheet and concrete ticket are consistent with the design requirements.
When the surface of the test block is polished, pay attention to the fullness of the slurry to prevent the depression of the concrete due to plastic deformation.
[10] Now, according to the local requirements, the test block is implanted into the chip for tracking management.
[IX cover] After the test block is formed, it shall be plastered after the initial setting of the concrete, troweled and polished along the surface of the test formwork, and often placed in situ or in the open air before the final setting.
5.
When it is less than 100m3, sampling shall not be less than once; When the quantity of concrete with the same mix proportion continuously supplied in a subdivisional project is greater than 1000 m3, the sample shall be no less than once for every 200 m3 of concrete.
The tamping rod shall remain vertical without inclination.
If the produced concrete test blocks are unqualified, rebound or core drilling sampling will be carried out, which is bound to cause a waste of money and energy and bring great pressure to the work.
The project department shall select comrades with certain technical quality and strong sense of responsibility as the test block.
One group (6 blocks) of the two groups of test blocks left shall be cured in the standard curing room, and the other group (6 blocks) shall be cured under the same conditions as the site.
The sampled concrete mixture shall be mixed again with a shovel for at least three times to ensure uniform concrete mixing.
The key to the growth of concrete strength is 28 days 。 However, the first 7 days of 28 days are especially critical.
The curing period shall not be less than 28 days.
Requirements for retention of concrete test block 1.
After the formwork removal, the test pieces shall still be cured under the same conditions.
The test mold shall not be used after missing angle or damage to avoid affecting the strength.
[five choices] Before making the test block, the concrete should be selected according to the requirements of the code and the concrete should be selected from the 1/4.
[12 delivery] Before the test block reaches its age, take the test block out of the standard curing room, wipe dry the water and send it to the testing unit for testing.
The steel tamping rod used for tamping shall be: round steel with a length of 600mm and a diameter of 16mm, and the end shall be rounded.
[solution] the test blocks shall be numbered while the test block formwork is removed, and the test block fabrication table shall be made and filled in carefully.
Common problems and solutions 1.
[second brush] the non perpendicularity of each adjacent surface of each test mold shall not exceed ± 0.5 °.
[seven] It means that the clinker is rammed into the mold in two layers, and the charging thickness of each layer is roughly the same.
In order to prevent the internal water evaporation from affecting the hydration speed of the cement, the test block shall be covered tightly with plastic cloth or wet sack in time to prevent the internal water evaporation from affecting the hydration speed of the cement.
The isolating agent shall be painted evenly, and the precipitated oil stain shall be wiped clean.
Before concrete sampling, the slump of concrete shall be tested.
Now commercial concrete is used on the construction site.
8.
(two more groups are recommended) 2.
（2） Two groups (12 pieces) of impermeability test blocks shall be added for every 250 ~ 500m3 of concrete added.
The inner surface of the test mold shall be coated with a thin layer of mineral oil or other release agent that does not react with the concrete (pay special attention to the thin layer) 。 3.
The sample must be randomly sampled from 1 / 4 ~ 3 / 4 of the mixer truck.
[eight rows] While inserting and tamping, use a spatula to insert repeatedly along the inner wall of the test mold to eliminate the air inside the test block.
Standard curing room The test pieces in the shall be placed on the support at an interval of 10 ~ 20mm from each other.
Three test pieces in a group exceeding the tolerance The arithmetic mean value of the measured strength value of is taken as the strength value of this group of test pieces (accurate to 0.1MPa) If the difference between the maximum or minimum of the three measured values and the middle value exceeds 15%, the maximum and minimum values shall be rounded off, and the middle value shall be taken as the strength value of the group of test pieces; if the difference between the maximum and minimum values and the middle value exceeds 15%, the test results of the group of test pieces are invalid, which is out of tolerance.
[four tests] after the mixer truck enters the construction site, its slump shall be tested in time, and each truck shall be tested.
The formwork removal time of the test pieces cured under the same conditions can be the same as that of the actual components.
The formwork removal time of the test piece is the same as that of the actual component.
Based on the relevant specifications and regulations such as ready mixed concrete, code for acceptance of concrete structure engineering quality, test method for mechanical properties of ordinary concrete, understand and check them one by one, and summarize the problems in the production of test blocks in combination with the experience and lessons in the production of concrete test blocks in the past The 12 step operation procedure of “certain, two brushing, three inspection, four measurement, five selection, six mixing, seven tamping, eight rows, nine covers, ten planting, eleven maintenance and twelve delivery” can effectively control the errors caused by poor manufacturing of test blocks.
The concrete must be mixed evenly with two times.
Before forming, check the test mold (100mm side length) The size and angle of the test mold shall not be deformed, and the non perpendicularity of each adjacent surface after assembly shall not exceed ± 0.5 °.
12 steps to complete the production and maintenance of concrete test blocks.
For ordinary commercial concrete, sampling of concrete with the same mix proportion shall not be less than once per 100m3 (standard curing, the same conditions and formwork removal).
(4) The impermeable test block shall be made at the pouring site.
After the selection of the test material, the concrete mixture should be mixed with the shovel for three times at least three times.
6.
[main reason] For human reasons, the number is not timely, and the test blocks at different times and different levels are mixed and stacked, resulting in confusion in sample delivery and out of tolerance of test block values.
3.
2.
Do not miss the test block, which will bring a lot of unnecessary trouble to the work.
The test block is allowed to stand indoors at 20 ± 5 ℃ for 1 day and night.
