| Causes of cracks | Characteristics of cracks |
| 1. Concrete materials | 1. Cement setting (time) is abnormal | Irregular cracks appear in the initial stage of concrete setting of larger area |
| 2. Abnormal expansion of cement | Radial network crack |
| 3. Floating slurry and sinking when concrete is set | One or two hours after the concrete is poured, it occurs intermittently on the steel bar and at the junction of the wall and the floor. |
| 4. Mud in aggregate | Irregular net-like dry cracks appear on the surface of the concrete |
| 5. Heat of hydration of cement | 1 to 2 weeks after the mass concrete is poured, straight cracks at regular intervals appear at regular intervals, some on the surface and some through
|
| 6. Hardening and drying shrinkage of concrete | Two or three months after pouring, it gradually appeared and developed. Oblique cracks appeared in the windows and the end corners of beams and columns. |
| 2. Construction | 1. The mixing time is too long | Reticulated cracks and irregular long and short cracks appear across the board |
2. Increase the amount of water and cement when pumping | Easy to appear net-like and irregular long and short cracks
|
3. Reinforcement stepped on chaotically, and the steel protective layer was thinned
| Occurs around the concrete ribs and along the surface of the reinforcement and piping
|
4. Pouring speed is too fast
| After pouring for 1 to 2 hours, cracks appeared on the steel bar, at the junction of the wall and the slab, and the beam and the column.
|
5. Pouring is uneven and not dense
| Easy to become the starting point of various cracks
|
6. the template bulges
| Parallel to the moving direction of the template, some cracks appear
|
7. Poor handling of stubble
| Cold stubble cracks appear at the stubble
|
8. Vibrate or load before hardening
| Cracks in the stressed state appear after hardening
|
9. Insufficient initial maintenance
| Shortly after pouring the letter, irregular short cracks and fine cracks appeared on the surface. After demoulding, the concrete surface appears white, hollow, etc. |
| 10. Formwork pillars sink | Cracks appear on the ends of beams and floor slabs and below the middle part |
| 3. Influence of climate and environmental factors | 1. Temperature, temperature change | Similar to shrinkage cracks, the existing cracks change with the environmental temperature and temperature changes |
| 2. The temperature and humidity difference between the two sides of the concrete member | On the side of low temperature or low humidity, it is easy to occur at the corners |
3. Multiple freeze-thaw cycles | On the side of low temperature or low humidity, it is easy to occur at the corners |
4. The fire surface is heated
| Turtle head cracks appear on the entire surface |
5. Corrosion and expansion of steel bars, large cracks, even spalling, and rusty water flow along the steel bars, etc.
| Large cracks appear along the steel bars, even peeling off, rusty water, etc. |
| 6. Corroded by acid and salt | Or the surface of the concrete is corroded, or expansive substances are produced, and it collapses |
| 4. Structure and external influence | 1. Overload | Vertical cracks appear on the tension side of the beam and the floor |
| 2. Earthquakes and accumulated loads | 45° oblique cracks occur in columns, beams, walls, etc. |
| 3. Insufficient amount of steel bars in section | Vertical cracks appear on the component under tension |
| 4. Uneven subsidence of the foundation of the structure | 45° big crack occurred |
Línguas: Portuguese
