Alkalinization of the wall surface, the causes of yellowing and the means of prevention and control

After the decoration of the house, the wall often appears pan alkali, coating bubbling, the day will be peeled and powdered, pan alkali this situation often appears in the bottom floor from the ground below 1.5 meters below the wall, the upper floor often appears below 80cm from the ground wall, and indoor cement cast-in-place roof, more common, especially in the southern water network area air humid area is the most common.

Alkaline on the wall

Pan-alkali genesis:

In the process of building a house, the bricks need to invade the water, the mortar will not dry quickly during masonry, and the water in the wall will remain saturated and semi-saturated, at this time, the bricks contain a large amount of salt nitrate and alkali salts in the cement mortar as the water evaporates, and slowly penetrates and migrates to the interface. The house is more than one meter from the ground, the ventilation is good, the water is quickly taken away by the air, the wall is dry fast, the nitrate is sealed in the wall body, no longer migrating to the interface, the lower wall is not circulating due to air circulation, the humidity in the wall is maintained for a long time, and the nitrate alkali in the wall is infiltrated with the evaporation of the water, and a large number of them migrate to the wall, which lays hidden dangers for the later decoration. In particular, the indoor cement cast-in-place roof is the most common, the reason is that in the top plate pouring process, the alkaline substances in the cement mortar accumulate between the bottom of the top plate and the template with water precipitation, after the water is dried and evaporated, the surface of the indoor cement roof will show a high alkalinity, plus the template is oily when cast in place, the decoration batch putty is prone to small bubbles, and the phenomenon of cracking and patent skin peeling is common in the later stage.

As we all know, the interior wall decoration generally uses ordinary putty with a low price, and the adhesive used in the putty is carboxymethyl cellulose CMC, etc., and the carboxyl adhesive will gel reaction with the alkaline substances in gray calcium and cement. The filler used in the putty is heavy calcium, which is neutral, slightly weaker and water-resistant. The walls are cement or lime mortar interfaces and are alkaline. The air humidity is easy to absorb moisture and return to moisture, and it will have a chemical reaction with the alkaline wall, cracking, bubbling, mold, peeling and shedding.

Reason: Because the indoor wall is not completely dry to decorate, when the summer room temperature rises, the water remaining in the wall is evaporated into a moist gas when it encounters the paint film, it is sealed under the paint film and cannot be released. Gel chemical reaction occurs in alkaline substances at the interface of putty and walls in humid environments. The initial appearance of bubbling, peeling, mold, and pan alkali is inevitable.

Processing method:

1. Symptoms: shovel off the serious parts of pan-alkali pulverization, treat it with pan-alkali inhibitors, and then remove the alkali on the wall slightly, and then apply the pan-alkali inhibitors to the wall, penetrate into the wall (preferably twice), and scrape the putty after drying.

2. Before decoration, open the indoor doors and windows for ventilation until the wall is completely dry, and then batch putty, and decorate the wall with the interface agent.

3. Putty adhesive is selected from hydroxypropyl to lakeized starch glue or starch ether and hydroxypropyl methylcellulose HPMC as adhesive. This can be avoided. Especially in the southern coastal areas of the air humidity, should be selected water-resistant putty, water-resistant putty is characterized by the more humid the strength, acid and alkali resistance is not easy to peel pan alkali.