Poor mortar adhesion means that the fullness of the mortar in the horizontal mortar of the masonry is less than 80%; blind joints appear in vertical joints, especially hollow brick walls, and more transparent joints often occur. The depth of the shrinkage joint is even more than 20mm, which affects the fullness of the mortar. The bricks were not watered and moistened before the masonry, dry bricks were on the wall, or the length of the ash was too long, resulting in poor adhesion between mortar and bricks.
The specific reasons for the poor adhesion between mortar and brick are as follows:
1
For low-strength mortar, such as cement mortar, the cement mortar has poor workability, and it is difficult to squeeze the mortar during masonry. After the operator spreads the mortar with a shovel or a trowel, the cavities of the bottom ash are generated, and the mortar is not full.
2
Drying the wall with dry bricks reduces the early dehydration of the mortar and reduces the strength, and the adhesion to the bricks decreases, while the dust on the surface of the dry bricks acts as a barrier, weakening the adhesion of the bricks to the mortar layer.
3
The masonry method is used for masonry. Sometimes the masonry speed cannot keep up because the masonry is too long. The water in the mortar is absorbed by the bottom brick, which causes the brick layer on the masonry to lose its bond with the mortar.
4
In order to avoid the cracking and cracking process, the ashing method with large necking was adopted to make the cracking depth of the masonry bricks more than 20mm, which not only reduces the fullness of the mortar, but also increases the jointing workload.
Preventive measures:
1
Improving the workability of the mortar is the key to ensuring the fullness of the mortar joint mortar and improving the bond strength. The choice of mortar raw materials is important. Sand cement should be within the shelf life, thickener cellulose ether and redispersible polymer powder to improve the adhesion of mortar should be selected from regular enterprises.
2
Improve masonry methods. It is not advisable to adopt the method of laying bricks or laying bricks, and the "Three One Bricklaying Method" should be promoted, that is, using a large shovel, a brick, a shovel, and a squeeze method.
3
When the grouting method is used for masonry, the length of the grouting must be controlled. In general, the temperature should not exceed 750mm, and when the temperature exceeds 30 ° C during construction, it should not exceed 500mm.
4
It is strictly forbidden to use in brick wall. The bricks should be wetted 1 to 2 days before masonry, so that the moisture content of sintered ordinary bricks and porous bricks can reach 10% to 15% during masonry; the moisture content of lime sand bricks and fly ash bricks can reach 8% to 12%.
5
During winter construction, the brick surface should also be properly wet under positive temperature conditions before laying. When it is impossible to pour bricks under negative temperature, the consistency of mortar should be appropriately increased. For the 9-degree seismic fortification area, masonry cannot be built when bricks cannot be burned in the severe winter.
