Prefabricated Floor Slab Installation
The installation of prefabricated floor slabs in buildings requires focused attention on key aspects such as base treatment, support and slab joints, overall connectivity, material specifications, and applications of special types. Here are the specific operational points:
1. Base Treatment: Ensure a Flat and Moist Bearing Surface Before installation, the top surface of the load-bearing wall must be rigorously treated. First, check the flatness of the wall top. If there are any irregularities, use high-grade cement mortar (such as M15 or above) for leveling, ensuring the mortar layer is full and uniform. It is strictly prohibited to use dry bricks or crushed stones for leveling to avoid slab cracking due to uneven local stress. Second, moisten the wall top with water one day before lifting, but avoid standing water to prevent poor adhesion between the mortar and the wall. The purpose of base treatment is to provide a stable bearing surface for the floor slab and reduce the risk of later settlement.
2. Slab Bottom Support and Slab Joint Treatment: Strengthen Structural Stability Temporary supports must be installed at the bottom of the slab during installation, typically using wooden beams or steel pipe brackets. The spacing between support points should not exceed 1.5 meters to prevent the prefabricated slab from bending or cracking due to insufficient strength. Slab joint treatment is crucial for waterproofing and structural safety: The width of slab joints should be controlled between 30-50 millimeters. The joints should be cleaned and moistened, then filled with C30 fine aggregate concrete (which can be mixed with a micro-expansion agent), vibrated densely, and the surface smoothed and polished. Improper slab joint treatment can easily lead to water leakage or slab misalignment due to thermal expansion and contraction.
3. Overall Connectivity: Avoid 'Independent Operations' The core of prefabricated slab installation is to connect individual slabs into an integral structure. The connection between the slab and the wall should be anchored using reserved or post-installed reinforcement bars, with a diameter of not less than 8 millimeters and an anchoring depth meeting design requirements. Between slabs, connecting reinforcement bars (such as Φ6@300) should be installed at the slab joints, and concrete should be poured to form an integral structure. If the connection is inadequate, weak points can form between the slab and the wall, or between slabs, which may lead to cracks or even collapse under load.
4. Materials and Specifications: Match Building Requirements The characteristic thickness of a prefabricated concrete floor slab is 120 millimeters, typically equipped with 8 main reinforcement bars (such as Φ8@150). The specific dimensions should be determined based on the building's bay size and lifting capacity. For example, rooms with larger bays require slabs with greater spans and increased reinforcement ratios to enhance load-bearing capacity. Hollow floor slabs (made of prefabricated prestressed reinforced concrete) are widely used in high-rise buildings due to their light weight and high stiffness. Their internal longitudinal channels save materials and reduce structural weight, but it is essential to ensure the channel direction aligns with the load direction.
5. Special Type Applications: Construction Points for Hollow Floor Slabs When installing hollow floor slabs, special attention should be paid to protecting the channels to prevent damage from construction machinery or heavy objects. Before lifting, verify that the channel direction matches the design drawings. After installation, seal the channel ends with mortar to prevent debris from entering. Additionally, the slab joint treatment for hollow floor slabs should be more stringent, and it is recommended to use high-strength grout for filling to ensure structural integrity.
