Strength of Prefabricated House Slabs
The strength of prefabricated house slabs is generally high, with a compressive strength typically conforming to the C30-C50 concrete standard (30-50 MPa). The flexural strength, enhanced by prestressed technology, can reach 5-8 kN/m², but their overall structural strength and seismic performance are inferior to those of cast-in-place concrete buildings.
Compressive Strength: C30-C50 Concrete Standard
The compressive strength of prefabricated slabs primarily depends on the concrete grade. Typically made from C30-C50 concrete, these slabs have a compressive strength of 30-50 MPa. This value indicates that a prefabricated slab can withstand a vertical load of 3,000-5,000 tons per square meter, sufficient to meet the load requirements of ordinary residential floors and roofs. For example, a prefabricated slab made from C30 concrete has a compressive strength more than 15 times that of the typical live load on a residential floor (2.0 kN/m²), ensuring high safety.
Flexural Strength: Enhanced by Prestressed Technology
The flexural strength of prefabricated slabs is significantly improved through prestressed technology. Ordinary non-prestressed prefabricated slabs have lower flexural strength, whereas those using prestressed processes can achieve a flexural strength of 5-8 kN/m². Prestressed technology involves applying tension to steel bars before concrete pouring, causing the concrete to generate reverse compressive stress under load, thereby offsetting part of the bending moment and improving crack resistance and load-bearing capacity. For example, in large-span roof slabs, prestressed technology can reduce slab thickness or increase span while ensuring structural safety.
Structural Limitations: Insufficient Integrity and Seismic Performance
Despite the high strength of individual prefabricated slabs, their overall structure has significant flaws. Prefabricated slabs are connected at nodes (e.g., by welding or bolting) to form floors or roofs, and the node strength is generally lower than the integrity of cast-in-place concrete, making the structure prone to separation or displacement under horizontal loads (e.g., earthquakes or wind loads). Additionally, the connection between walls and floor slabs in prefabricated houses is weak, making them susceptible to collapse due to excessive 'inter-story displacement' during earthquakes. Therefore, the application of prefabricated slab buildings is limited in areas with high seismic fortification requirements (e.g., earthquake zones of intensity 8 or higher), necessitating measures such as adding structural columns and ring beams to enhance overall integrity.
Application Scenarios and Improvement Directions
Prefabricated slabs are still widely used in low-rise residential buildings, temporary structures, or non-seismic areas due to their fast construction speed and low cost. To improve performance, modern prefabricated slabs often use high-strength concrete (e.g., above C60), fiber reinforcement, or composite materials (e.g., carbon fiber cloth reinforcement) and optimize node connection methods (e.g., wet connections, mechanical anchoring) to narrow the gap with cast-in-place structures.
