Solutions to Ten Major Problems in Cement Concrete
The total time for concrete transportation, firing, and intermission shall not exceed 2 hours.
The mud content and impurities in the stones shall not exceed 2%.
Cement should be retested after one month of leaving the factory, otherwise it cannot be used for load-bearing structures.
And it is necessary to pay attention to the appropriate time for primary leveling and secondary polishing (not exceeding two hours) Sand should be sieved and clean sand should be used as much as possible Strictly mix according to the ratio.
4.
③ Water too early.
② Before final setting, add pure cement and repeatedly press and plaster.
Reason: ① The concrete loses water too quickly before initial setting.
Complete combination of secondary pressure polishing.
7.
The problem of concrete solidification is that the concrete solidification is slow or damaged, the strength cannot meet the requirements, the surface of the concrete is scattered, and the surface is peeled off
.
Concrete peeling and sand flipping: The phenomenon of peeling and sand flipping on the surface of concrete, resulting in a layer of white surface when rubbed with feet, manifested as about half a centimeter of non solidification on the top but achieving solidification effect on the bottom.
Concrete should be thin in summer, thick in winter, and suitable for spring and autumn.
8.
④ Concrete contains a large amount of mud Concrete is damaged by freezing in winter.
5.
Precautions for concrete maintenance: 1.
Sand.
2.
After the completion of concrete pouring: ① Summer: After the initial setting (usually two hours), cover it with plastic film, straw bags, corn straw, etc., and after the final setting (usually no more than five hours), timely “water replenishment” maintenance must be carried out.
3.
Cement precautions: 1.
⑥ Factors such as uncertain mix proportions and uneven drying and thinning.
The use of additives (early strength, antifreeze…) must be strictly measured according to the manufacturer’s instructions.
It is strictly prohibited to mix different brands of cement.
6.
Prevention: ① Use water replenishment and insulation measures.
3.
The curing time of concrete shall not be less than 7 days.
It is best to choose a mixer for concrete mixing (the time should be controlled at least 2 minutes).
Concrete formwork removal: The span of the beam and slab is within 6 meters, and the strength must reach over 70% (i.e.
Manual mixing must be done four or more times, evenly mixed, and with consistent dryness.
over 7 days); If the span exceeds 6 meters, the strength must reach 100% (including cantilever structures), and the column should reach more than 50%.
Strictly control the proportion of cement and water in concrete (commonly known as dry, thin, and adhesive).
2.
If the template needs to be removed in advance, measures must be taken to strengthen it.
② When pressing and plastering, cement or pure water slurry cannot be directly used, and a portion of sand (1:1 plain cement for surface treatment) must be added Strengthen the leveling work of concrete pouring and try to achieve one-time leveling.
② Winter: After the initial setting, it is necessary to cover it with straw bags, corn stalks, or other items for insulation treatment or add anti freezing and drought agents Early spring and late autumn: Pay attention to weather changes at all times and decisively take insulation measures.
When plastering or building walls, pay attention to keeping the bricks moist.