Analysis Diagram of Cracks in Prefabricated Slab Houses
The following are the common types of cracks in prefabricated slab houses and key points of the analysis diagram:
1. Cracks at the End Face of Prefabricated Slabs
Appearance: Cracks run vertically along the side of the slab end, mostly short and resemble 'vertical cracks'.
Causes: Caused by construction defects, such as warping deformation during the production of prefabricated slabs or uneven support pads during installation leading to stress concentration at the slab corners.
Impact: These are local residual cracks that usually do not affect the overall load-bearing capacity of the structure but may reduce aesthetics. It is necessary to monitor whether the cracks continue to expand.
Diagram Reference: Cracks are concentrated on the side of the slab end, perpendicular to the slab surface, and are relatively narrow (generally less than 0.3mm) in width.
2. Floor Cracks in Old Prefabricated Slab Houses
Appearance: Cracks extend unidirectionally and are parallel to one side wall of the house, mostly in a straight line.
Causes: Occur due to the asynchronous deformation of two adjacent prefabricated slabs, often caused by temperature changes (thermal expansion and contraction) or differences in foundation settlement leading to an imbalance in stress between the slabs.
Impact: If there is no obvious deflection of the floor (i.e., no visible bending deformation), the cracks generally pose no safety risks but may cause rainwater leakage. It is necessary to check whether the waterproof layer is damaged.
Diagram Reference: Cracks extend along the length of the floor and run through the joints of multiple prefabricated slabs.
3. Cracks at the Joints and Post-pouring Strips
Appearance: Cracks run vertically or obliquely along the construction joint surface, resembling 'construction joint cracking'.
Causes: Caused by construction defects, such as inadequate concrete pouring and curing at the joints or the failure to set up tie bars in the post-pouring strips according to regulations.
Impact: Cracks may damage the structural integrity and cause leakage problems but usually do not affect the vertical load-bearing capacity. It is necessary to monitor whether the cracks penetrate through.
Diagram Reference: Cracks are located at the junction of new and old concrete, cracking irregularly obliquely or vertically, and the width may change with the seasons.
4. Key Precautions
- Crack Width Threshold: If the crack width exceeds 0.7mm or is accompanied by obvious deflection of the floor (such as visible bending), immediately entrust a professional organization for inspection and identification, and carry out reinforcement if necessary.
- Hazard Assessment: Cracks in prefabricated slab houses are mostly related to construction defects or material shrinkage characteristics. A comprehensive assessment should be made by combining the crack appearance, location, and expansion trend to avoid blind panic.
- Diagram Reference: Detailed classification diagrams of cracks can be found in the 'Technical Standard for Building Structure Inspection' (GB/T 50344) or professional structural engineering atlases, which will mark the crack appearance, causes, and treatment suggestions.
If further analysis of specific crack cases is required, it is recommended to provide crack photos or detailed descriptions (such as location, width, and direction) for targeted judgment in accordance with regulations.
