What is the sound of snapping in a house with a frame structure at night? Is there anything wrong with the quality of the house?

If it's the sound of a glass ball falling to the ground, and it's coming from the ceiling, I remember it's the sound of a fungus in popular science ... I'll show it to you.

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It turns out that the culprit is mold! !

It is an incomplete fungus that mainly corrodes industrial materials and cement. It lives on a porous surface and feeds on minerals in cement.

Generally, the ceiling is supported by thin steel bars on the upper and lower floors. In fact, when grouting, the steel bar is not vertically stuck in the cement. Due to the flow and weight of cement slurry, there may be upward or left stress accumulation, or after the house is built for several years, it will be affected by earthquake or slight displacement of foundation, and the thin steel bar will produce new stress.

On the lower floor of the ceiling, there is a pipe outlet for electric light lines, with temperature and air. So the mold will gradually invade the cement along this hole, and the contact surface between the fine steel bar and the cement is the ideal joint, where the mold accumulates and the mycelium begins to erode into the surrounding hollow pipes. When the cement around the reinforced bar is eroded to a certain extent, it will rebound in the hollow tube, which is the source of marble sound.

Therefore, the next step in the experiment is to deliberately make cement blocks; A plastic bar slightly thicker than the steel bar is sandwiched in the middle to form a hollow channel. After the cement is half dry, take out the plastic pipe and insert the steel bar, and then pour some cement from the other end to fix it.

As it turns out, the sound of thin steel bars bouncing in pipes is most similar to that of marbles.