ANALYSIS OF COMMON CRACKS IN AAC PANEL

Differences between AAC panel and AAC block:

1. There is steel reinforcement and cage frame inside the plate, and the production process is different between them.

2. Various quality problems are prone to occur in the production of aerated concrete slabs, and its production technology is more complex than ordinary aerated concrete blocks.

Edge crack

Side and corner cracks mainly occur at the two corners of the plate near the mold frame, which are most likely to occur in winter. The main reason is that after the blank body is cut, the heat loss at the two corners is too large, and there is no strength or temperature at the corners. The cracks cannot be seen before entering the kettle.Always pay attention to the production.

Horizontal fissure

Horizontal crack refers to a crack along the length direction of the plate, is a crack through the plate, often appear in the entire mold, more than 200 thick and below the plate. 

There are two cases of horizontal fracture:

1. One is a short, thick seam, resembling an earthworm.This situation is mainly due to the fact that the air generation speed of the slurry is faster than the thickening speed. After the air generation of the slurry is completed, the thickening does not keep up with the slurry, and the slurry does not sink with the support of dense mesh, clips and other structural parts. As a result, stratification occurs in this part, resulting in the horizontal crack of coarse joints in the above figure.

2. The other is elongated and very straight, mainly because the air flow rate of the slurry is slower than that of the thickening speed, and the air flow is still not finished after the completion of the thickening of the slurry, and the stoma inside the slurry forms a large internal pressure, which is easy to cause the porosity to flow through at the bottom of the main rib, thus forming this crack.

The inner cause of horizontal crack formation is steel mesh, and the direct cause is choking or sinking caused by inconsistency of thickening and gas emission speed.

In particular, we often fail to pay attention to the subsidence. During the production of blocks, the slurry subsidence is the overall subsidence without stratification. In the plate, the dense mesh and the upper pulp of clips do not sink together, so the stratification occurs. 

Vertical fracture

The vertical crack is not allowed to be repaired according to the national standard, and the damage caused is very large.Vertical fracture often occurs in roof panels, floors, and thicker wall panels.

The coefficient of expansion of reinforcement is greater than that of aerated concrete, and the main reinforcement used in roof slab, floor and thicker wall slab is more and thick, so it is easier to tear aerated concrete.

End crack

End layer cracks often appear at the lower mesh of the end of roofing board.

The reason why this kind of end layer crack generally appears in the roof board is that the number and diameter of the main reinforcement of the upper and lower mesh are inconsistent. The number and diameter of the main reinforcement of the lower mesh are large. In the process of autoclaving, due to the inconsistency of the expansion force of the upper and lower steel mesh, shear force is generated, so that the end cracks of the plate are formed.

The tail protective layer fell off

The rear reinforcement protection layer falls off, which is easy to appear in the plate of 10 cm or less, especially the thinner outer wall board and roof board.

The last anchorage bar at the tail of the plate is densely distributed, which easily leads to the loss of the tail protection layer.