1. Avoid moisture, damp cement will reduce or even lose the original strength..
2. Avoid exposure, concrete or plaster will be exposed after the operation, with the rapid evaporation of water, its strength will be reduced or even completely lost.
3. When the temperature of the bottom avoids freezing and the concrete or mortar is mixed, if it is frozen, the cement cannot be hydrated.
4. Avoid hot and hot, solidified mortar or concrete components, if often under high temperature and hot conditions, there will be loss of strength.
5. Avoid the base layer is dirty and soft, the cement can be firmly bonded or gripped together with the hard, clean base layer, but its adhesive grip strength is related to the smoothness of the base surface. In the smooth construction of the grass-roots level, it must be brushed in advance to make the cement and the grass-roots layer firmly bonded.
The grime, greasy, acid and alkali substances on the grassroots level all play an isolation role and must be carefully cleaned. After that, a single grout is first brushed, and mortar or concrete poured.
Cement in the solidification process to produce shrinkage, and in the wet and dry, hot and cold changes in the process, it and the loose, weak base of the volume change is very incoherent, will inevitably occur emptying or cracks, making it difficult to bond firmly. Therefore, wood, slag mats, and lime soil cushions cannot be firmly bonded with mortar or concrete.
6. Avoid aggregate impure, as sand or gravel of concrete or cement mortar aggregate, if there is dust, clay or other organic impurities, it will affect the bond strength between cement and sand, stone, and ultimately will reduce the resistance Pressure strength. Therefore, if the impurity content exceeds the standard, it must be cleaned before use.
7. Avoid thick gray water, concrete is very thin. Since hydration requires only about 20% of the weight of the cement, the excess moisture will leave a lot of voids in the concrete, which will reduce the strength of the concrete. Therefore, under the premise of ensuring the compaction of cast, the mixing water should be minimized.
Many people think that the more cement used for plastering, the more sturdy the plaster layer. In fact, the greater the amount of cement, the thicker the mortar, the greater the amount of shrinkage of the plaster layer and the more cracks that result. Under normal circumstances, plastering should first use 1: (3 - 5) of coarse mortar to wipe the leveling layer, then use 1: (1.5-2.5) cement mortar to wipe a thin surface layer, avoid using too much cement. .
8. Avoid acid corrosion, acid substances and calcium hydroxide in the cement will occur a neutral reaction, the product volume is loose, swelling, easy to hydrolyze powder after encountering water. Causes the concrete or plastering layer to be gradually eroded and disintegrated, so the cement should not be subject to acid corrosion..
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