Specification for Grouting Sleeves in Prefabricated Houses

The specifications for grouting sleeves in prefabricated houses are primarily based on the 'Technical Specification for Application of Grouted Sleeve Splicing of Steel Bars' (JGJ355-2015) (2023 edition) and the 'Grouting Sleeve for Steel Bar Connection' (JG/T 398-2019). The core requirements are as follows:

1. Definitions and Scope of Application

'Grouted sleeve splicing of steel bars' refers to the method of inserting a single ribbed steel bar into a metal sleeve, injecting a grout mixture, and forming a monolithic structure through hardening to achieve force transfer in steel bar butt connections. This technology is applicable to the connection of steel bars in vertical or horizontal components of prefabricated houses, meeting structural safety and durability requirements.

2. Pre-construction Preparations

1. Technical Preparations

   • Verify the model, specifications, corresponding steel bar diameters, and installation positions of grouting sleeves in the drawings to ensure consistency with the design.
   • Conduct targeted technical briefings, with all participants signing the briefing records for confirmation.
   • Before large-scale construction, create process samples and conduct tensile pull-out tests on test joints. Formal construction can only commence after passing the tests.

2. Material Inspection upon Arrival

   • Grouting sleeves: Inspect for cracks or deformations on the exterior and check if the wall thickness meets standards through sampling.
   • Grout: Check the integrity of the packaging, ensure there is no moisture absorption or clumping, and store different batches separately.
   • Supporting materials: Sealing materials, rubber plugs, and adhesive strips must be free from aging or damage to ensure sealing performance.

3. Equipment and Personnel Preparations

   • Pre-inspect tools such as grout pumps and electric mixers, and conduct trial runs of the grout pumps.
   • Grouting operators must undergo specialized training and be familiar with the process flow and safety regulations.

3. Construction Process Requirements

1. Process Inspection and Reports

   • Provide type inspection reports for joint specimens at the construction site. Grout joint process inspection and tensile strength specimens must be prepared by actual construction personnel under witness.

2. Construction Tools and Inspection Equipment

   • Use tools that facilitate observation and have grout replenishment functions, equipped with portable endoscopes and other equipment to ensure traceability of grout compactness.

4. Inspection Requirements

1. Grout Quality Inspection

   • Transfer floors: 100% inspection of grout sleeve quality is required.
   • Other floors: Randomly select at least 10% of the total number of floors and no less than one floor, covering all floors worked on by grouting teams; inspect at least five prefabricated components per inspected floor and at least three sleeves per component.

2. Grout Performance Inspection

   • Upon arrival, inspect the 30-minute fluidity and bleeding rate of the mixture, as well as indicators such as 3d/28d compressive strength, 3h vertical expansion rate, and the difference between 24h and 3h expansion rates to ensure compliance with design requirements.

5. Supplementary Industry Standards

The 'Grouting Sleeve for Steel Bar Connection' (JG/T 398-2019) specifies requirements for the material, dimensional deviations, and mechanical properties of sleeves. It is used in conjunction with JGJ355-2015 to jointly ensure the quality of grout connections.