Mixed and Prefabricated Slab House Structure

There is a fundamental difference between the mixed structure and the prefabricated slab structure in house construction, and they should not be confused.

Mixed structure typically refers to a load-bearing structural system composed of two or more different materials. The most common type is the brick-concrete structure, where brick walls serve as vertical load-bearing components and concrete slabs serve as horizontal load-bearing components. This structure combines the compressive strength of brick walls with the load-bearing capacity of concrete slabs through the combination of different materials, and was widely used in multi-story residential construction in the last century. Its core characteristics are material diversity and structural synergy, such as the formation of an overall load-bearing system through the connection of brick walls and concrete slabs with steel bars.

Prefabricated slab structure, on the other hand, uses factory-prefabricated concrete slabs (available in solid and hollow forms) as the main horizontal load-bearing components, with floor construction completed through on-site assembly. Old buildings constructed from the 1970s to the 1990s often adopted a brick-concrete structure combined with prefabricated hollow floor slabs model: brick walls bore vertical loads, and prefabricated slabs were directly placed on top of the walls to form the floor. Although this combination met housing demands at the time, it had significant drawbacks:

1. Poor integrity: Prefabricated slabs were connected to walls and to each other only through simple overlaps or a small number of steel bars, lacking effective overall anchoring, and were prone to displacement or even detachment under horizontal forces (such as earthquakes);
2. Weak seismic performance: The floor system assembled from prefabricated slabs had difficulty transmitting the shear forces generated by earthquakes, leading to structural disintegration during earthquakes;
3. Difficult renovation: The limited space for embedded pipelines within prefabricated slabs made it easy to damage structural integrity during later renovations or equipment updates.

To enhance building safety, China has gradually phased out prefabricated slabs since 2008 and promoted cast-in-place floor slabs (integrally poured concrete floor slabs) and composite floor slabs (a combination of prefabricated slabs and cast-in-place layers). Although composite floor slabs include prefabricated components, they form an assembled monolithic structure with the prefabricated slabs through the cast-in-place layer, retaining the high construction efficiency advantage of prefabricated slabs while enhancing structural integrity through the cast-in-place layer, meeting modern building requirements for safety and functionality. The fundamental difference from traditional prefabricated slab brick-concrete structures lies in the fact that the prefabricated slabs in composite floor slabs serve only as structural components and permanent formwork, ultimately achieving reliable connections with vertical components through the cast-in-place layer to form a continuous load-bearing system.