Cast-in-Place Concrete on Prefabricated Concrete Houses

It is feasible to add a layer of cast-in-place concrete on the prefabricated slabs of prefabricated concrete houses to enhance the toughness and hardness of the floor, provided that specific conditions are met and construction specifications are strictly followed.

I. Feasibility Conditions
The core premise of this plan is that the house structure must include columns, beams, and cantilever beams. These load-bearing components provide necessary support for the cast-in-place layer, preventing structural damage caused by concentrated loads. Without such components, the weight of the cast-in-place layer may directly act on the prefabricated slabs, leading to the risk of overall collapse.

II. Key Construction Details

1. Interface Treatment: Use an electric pickaxe to chisel a 12 cm wide and 10 cm deep circular groove along the edge of the prefabricated slab. This operation aims to expose the internal reinforcement bars of the wall, enabling the reinforcement mesh of the newly added cast-in-place layer to form a reliable connection with the original structure. Meanwhile, the prefabricated slab serves only as a formwork and does not directly participate in load-bearing.
2. Reinforcement Configuration: The cast-in-place layer must adopt a double-layer bidirectional reinforcement mesh and incorporate radial reinforcement bars. The radial reinforcement bars, arranged radially centered around columns or beams, effectively disperse local loads and reduce impact on the prefabricated slabs. It is recommended that the diameter of the reinforcement bars be no less than 10 mm, with a spacing controlled between 150-200 mm.
3. Concrete Performance: Commodity concrete with a strength grade of C30 or higher should be selected, with an appropriate amount of micro-expansion agent added to compensate for shrinkage. During pouring, the concrete should be vibrated and compacted in layers to avoid defects such as honeycombing and pitting.

III. Potential Risks and Countermeasures

1. Structural Integrity Defects: Prefabricated slabs are connected only by cold-drawn reinforcement bars (14#) and lack transverse reinforcement bars, making them prone to slab joint cracking after long-term use. Countermeasure: Apply an interface agent at the interface between the cast-in-place layer and the prefabricated slab, and lay steel wire mesh sheets to enhance bonding.
2. Concrete Cracking Risk: Shrinkage deformation of the joints between prefabricated slabs may propagate to the cast-in-place layer, causing reflection cracks. Countermeasure: Preset dividing strips at the slab joints and perform joint filling treatment later.
3. Load Exceedance Issues: The self-weight of the cast-in-place layer is approximately 1.2 kN/㎡, necessitating a review of the original structure's load-bearing capacity. Countermeasure: Commission a professional institution to conduct structural testing before construction and reinforce beams and columns if necessary.

IV. Explanation of Professional Disputes
Some engineers argue that this plan is not feasible, primarily based on two points: the significant difference in deformation modulus between the prefabricated slab and the cast-in-place layer, which can easily lead to interface delamination; and the potential for slab joint shrinkage to trigger连锁 (chain reaction) cracking. Therefore, strictly adhering to the aforementioned construction specifications and strengthening quality supervision are key to ensuring the success of the plan.