Prefabricated Concrete Slabs in Housing Construction

Prefabricated concrete slabs for housing construction were commonly used concrete prefabricated components in the early 20th century. They were prefabricated in factories and installed on-site, and were widely used in the construction of affordable housing. However, they had issues such as weak earthquake resistance and limited lifespan, and have gradually been replaced by cast-in-place concrete and prefabricated buildings.

Definition and Manufacturing Process of Prefabricated Slabs

Prefabricated slabs are concrete components produced and processed in prefabrication yards. During manufacturing, a hollow mold is first made using wooden planks. Reinforcing bars are then arranged inside the mold, and cement is poured. After drying, the wooden planks are knocked off to form the finished product. Depending on their structure, prefabricated slabs are divided into two types: solid and hollow. Hollow prefabricated slabs achieve lightweighting by reducing the non-load-bearing concrete, lowering material costs and facilitating transportation and installation.

Application Scenarios and Historical Status of Prefabricated Slabs

From the 1970s to the 1990s in the 20th century, prefabricated slabs became the mainstream structural form for affordable housing and economically affordable housing due to their high construction efficiency and low cost. Most residential buildings constructed in China before 1985 used prefabricated slab floors. Their application scenarios included:

• Floor Components: Serving as load-bearing structures between building floors;
• Non-load-bearing Components: Such as highway ditch covers and roof insulation layers.
  The popularity of prefabricated slabs during this period reflected the demand for rapid and large-scale construction in building technology at that time.

Main Issues with Existing Prefabricated Slab Buildings

1. Weak Earthquake Resistance: Prefabricated slabs are connected at nodes, resulting in poor integrity and susceptibility to dislocation or collapse during earthquakes.
2. Poor Sound and Heat Insulation: The hollow structure or low material density leads to poor sound insulation and insufficient heat insulation.
3. Difficult Structural Adjustments: Internal pipelines are pre-embedded, making it difficult to renovate and resulting in low flexibility in spatial layout.
4. Risk of Water Seepage: Cracks are prone to appear at node connections due to aging or construction defects, leading to rainwater leakage.
5. Limited Service Life: The design lifespan is usually 30-50 years, and structural safety declines after exceeding this lifespan.

Replacement and Renovation Policies for Prefabricated Slab Buildings

With the advancement of building technology, cast-in-place concrete (with strong integrity and good earthquake resistance) and prefabricated buildings (with modular production and a 30% reduction in construction period) have gradually replaced prefabricated slab structures. Since 2022, China has implemented renovation policies, adopting differentiated approaches to prefabricated slab buildings:

• Renovation and Upgrading as the Main Approach: Strengthening, waterproofing, and functional upgrades are carried out for buildings that do not meet the criteria for dilapidated housing;
• Demolition and Reconstruction as a Supplementary Measure: Only dilapidated buildings with severe structural damage and safety hazards are demolished.

The rise and fall of prefabricated slab buildings reflect the transformation of building technology from 'rapid construction' to 'safety and durability', and their historical status and existing issues provide important references for the development of modern architecture.