How to control the alkalinity of cement-based composite materials?

A

anna

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In cement-based materials, how to effectively inhibit the generation of alkali, or how to avoid the continuous generation of a large amount of alkali? Especially in dry powder coatings, wear-resistant grounds, and caulking compounds?
 
There seems to be no cure for the problem of alkali returning in terms of formula, and the main thing is to try to avoid the occurrence of alkali returning from the aspect of the application. The main principle of alkali returning is that the alkaline ions are brought out of the surface by the water, and the sodium and calcium ions crystallize on the surface and generate salt to form a white powder, such as a dry powder mortar. If the ground is bleeding, many alkaline and sodium calcium ions will be dissolved on the surface and turn white after crystallization. Before the foundation is dry, there must be no water on the surface. In applying caulking compounds, ensure that the surface moisture evaporates as soon as possible after the sponge is wiped, or use a sponge that is not too wet.
 
Moreover, alkali returning is related to construction operations and the environment. There is no solution to solve it at present fundamentally but to reduce the probability of its occurrence as much as possible. There may be a way in the future
 
Alkali return always occurs with the migration of water, so controlling the amount of water added to the mortar is an improvement method, and preventing the water absorption after the mortar is formed into a film is also an excellent way to improve, and the inhibitor will also play a particular role.
 
If alkali return appears on the exterior wall, wash it with 2%-3% oxalic acid and rinse it with clean water. As for the phenomenon of water seepage on the outer wall, you only have to do the waterproof treatment. The easiest way is to apply waterproof paint. The dampness of the division mainly causes the efflorescence of the external wall bricks. The small-scale water seepage on the exterior wall should be caused by the insufficient fullness and compactness of the seams of the face bricks, which leads to the seepage of water from the brick seams to the wall in the rainy season. Water seepage and dampness on the wall directly lead to the occurrence of alkali return, and the two are closely related. Attention: 1. The masonry mortar used on the external wall should be saturated and reach more than 85% according to the requirements. The cement mark for the outer wall should be higher than that of the internal wall to prevent the exterior wall from water seepage. The mortar cannot mix with soil. 2. The type of cement used in the caulking mortar is also significant: it is recommended to use composite Portland cement mixed with 15%-30% fly ash (because fly ash has the function of inhibiting efflorescence); Polymer caulking material can also be used for caulking; it must be dense when pointing.
 
1. Reduce the amount of water

2. Improve maintenance conditions

3. Lower the freezing point

4. Make cement strength in the early phase
 
I agree with you guys, and I'll add one more thing. We all know that alkali return generally occurs when the temperature is relatively low or in a humid environment for a long time. Therefore, we can make it dry relatively fast to reduce alkali return. In addition, some say that the product of Elotex is used, called ERA-100. However, reverse alkali can not be changed entirely after use but can only be alleviated to some extent. If you add too much, the cost is also a big problem. There is no conclusion on whether there are disadvantages to mortar.
 
1. Reduce the water-cement ratio; 2. Control the particle gradation of the sand; 3. Select the cement with a higher mark.
 
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