Prefabricated Concrete Inspection for Houses
The inspection of prefabricated concrete for houses mainly includes two aspects: on-site acceptance and inspection requirements, as well as special inspections.
On-site Acceptance and Inspection Requirements
According to relevant specifications, structural performance inspections are required for flexural prefabricated components. However, for stairs and floor slabs with a span of less than 3m, beams and composite flexural components with a span of less than 4m, inspections may be waived unless specifically required by the design. Inspections are conducted either at the prefabricated component production plant or on the construction site. For each batch of the same type of prefabricated components, with no more than 1000 pieces, one component is randomly selected for inspection. 'Same type' refers to components made of the same steel grade, with the same concrete strength grade, production process, and structural form. The selection should preferably be made from components with the maximum design load, the most unfavorable stress conditions, or the largest production quantity. The inspection methods are specified in Appendix B of the national standard. Different types of components have varying inspection requirements. Reinforced concrete components and prestressed concrete components that allow cracks are inspected for load-bearing capacity, deflection, and crack width. Prestressed concrete components that do not allow cracks are inspected for load-bearing capacity, deflection, and crack resistance. Large components (with a span greater than 18m) and components with reliable application experience may only be inspected for crack width, crack resistance, and deflection. Components with a small quantity of use (less than 50 pieces) and reliable basis may be exempt from inspection. For components that do not undergo structural performance inspections, a strict on-site supervision system or physical inspections must be implemented. On-site supervision requires the construction unit or supervision unit to send representatives to supervise at the factory, register relevant information on the supervision platform, and confirm their identity and location through a mini-program. Physical inspections are conducted when the prefabricated components arrive on site, checking the quantity, specifications, spacing, protective layer thickness, and concrete strength of the main load-bearing reinforcement in full. The procedures and time nodes are specified in the special acceptance plan.
Special Inspections
Special inspections are carried out in different regions. For example, Anhui Province inspects the quality of ready-mixed concrete, covering in-progress housing and municipal engineering projects as well as ready-mixed concrete production enterprises. The inspection content includes enterprise qualifications and raw material management, among others. Concrete strength tests are conducted on the main load-bearing components, and problematic projects are traced and tested, with legal actions taken accordingly. Pinghu City conducts joint inspections on the production quality of commercial concrete supply enterprises, uncovering numerous issues in the laboratories and construction sites of these enterprises, such as non-standard environmental control in laboratories and non-compliance in sample preparation and delivery. These issues lead to insufficient concrete component strength and a high incidence of appearance defects, affecting the safety and durability of the projects.
