Concrete Prefabricated Slabs for Houses

Concrete prefabricated slabs for houses were commonly used floor components in early 20th-century architecture. They have gradually been replaced by cast-in-place structures. Existing prefabricated slab houses have numerous issues that need to be addressed based on actual conditions.

Definition and Production of Prefabricated Slabs

Concrete prefabricated slabs for houses are concrete prefabricated components produced and processed at a prefabrication yard and then directly transported to the construction site for installation. During production, a hollow mold is first made using wooden planks. After reinforcing bars are placed in the hollow part of the mold, cement is poured to fill the hollow section. Once it dries, the wooden planks are knocked off, leaving behind the prefabricated slab. Prefabricated slabs come in two types: solid and hollow. The hollow structure achieves lightweighting by reducing the non-load-bearing concrete portion. The production purpose is to leave the non-load-bearing areas hollow when the hollow part of the slab is not under stress, thereby reducing weight and saving costs.

Load-Bearing Capacity of Prefabricated Slabs

An ordinary concrete prefabricated slab can bear a maximum load of about 500 kilograms per square meter, roughly equivalent to the weight of five adults. National standards stipulate that residential floor slabs must be able to withstand at least 200 kilograms of live load. In reality, considering the self-weight of the floor slab, the total load-bearing capacity can reach about 760 kilograms. However, this figure is influenced by factors such as thickness, material, span, and construction. For example, a 10-centimeter-thick slab can only bear 150 - 250 kilograms, while a 12-centimeter-thick one can bear up to 250 kilograms. The higher the concrete grade, the stronger the load-bearing capacity. But if the span exceeds 4 meters or the supports are not properly installed, the load-bearing capacity is directly reduced by 30%. Construction quality is also crucial. Improperly treated joints or excessive cement application can make the floor slab fragile.

Current Situation and Issues of Prefabricated Slab Houses

Prefabricated slab houses are buildings constructed mainly using prefabricated slabs. They originated in the early 20th century and were mainly used for floor slabs and roof insulation layers. Most residential buildings constructed in China before 1985 adopted this structure. With the development of building technology, cast-in-place concrete and prefabricated buildings have gradually replaced traditional prefabricated slab houses. Since 2022, China has implemented a policy of renovating old buildings, focusing on repairing and renovating prefabricated slab houses and only demolishing those that meet the criteria for dangerous buildings. Existing prefabricated slab houses generally have issues such as weak earthquake resistance, poor sound and heat insulation, and a service life of about 30 - 50 years. Some regions have already initiated demolition work.