4.8 Reinforcement Sleeve Grouting Connection Technology
4.8.1 Technical Overview
Reinforcement sleeve grouting connection technology involves using a grouting sleeve into which ribbed steel bars are inserted. The inner cavity of the sleeve forms a concave-convex surface, and a specialized high-strength cement-based grout is injected into the gap between the sleeve and the steel bars. Once the grout hardens, the steel bars become securely anchored within the sleeve, creating a reliable connection method for prefabricated components.
This technique embeds grouting sleeves within concrete components. At the construction site, grout is injected into the sleeves from outside the prefabricated components via grouting pipes to complete the steel bar connections. It serves as the primary load-bearing steel bar connection method in prefabricated concrete structures and is widely applied in various assembled integral concrete buildings.
The grouting connection joint consists of three main materials: steel reinforcement, the grouting sleeve, and the grout itself. Grouting sleeves are classified as either semi-grouted or fully grouted. Semi-grouted sleeves feature one end connected by grouting and the other end by mechanical means.
The construction process typically includes factory assembly of the sleeve and steel reinforcement connection for prefabricated elements, installation and fixation of the sleeve on the formwork, and connection of inlet and outlet pipes to the sleeve. At the construction site, component installation, sealing of the grouting chambers, preparation of the grout mix, and grouting of the sleeve are performed.
For vertical prefabricated components, load-bearing steel bars can be connected using either semi-grouted or fully grouted sleeves. Grouting is performed through connected cavities, which should be properly segmented. Components may also be grouted individually using a single sleeve, with a grout layer applied at the horizontal joint before positioning. The grout used must be compatible with the sleeve and validated through joint type inspection.
Pressure grouting is carried out using equipment matched to the grout’s properties. Grout is injected via the inlet hole below the sleeve and flows out through the outlet hole above. Both holes must be promptly sealed to ensure the effective connection area inside the sleeve is completely filled.
For horizontal prefabricated components, longitudinal load-bearing steel bars are connected at cast-in-place strips using fully grouted sleeves. After the sleeve is installed, the grout inlet and outlet holes should be positioned above the sleeve. Pressure grouting is performed with special tools or equipment designed for single sleeves. Grout is injected from one end and exits from the other, with the grout surface at the inlet and outlet joints rising above the highest point of the sleeve’s outer surface.
Following sleeve grouting, the grout must reach a compressive strength of 35 MPa under the same curing conditions as test specimens before any subsequent construction that might disturb the joint is carried out.
4.8.2 Technical Specifications
The use of steel sleeve grouting connection technology must comply with relevant national standards, including the “Technical Specification for Prefabricated Concrete” (JGJ 1), “Technical Specification for Application of Steel Sleeve Grouting Connection” (JGJ 355), and “Technical Standard for Prefabricated Concrete Buildings” (GB/T 51231). The force transmission mechanism of grouted steel sleeves is more complex than traditional mechanical connections. As such, JGJ 355 prescribes detailed requirements for performance, type testing, process inspection, construction, and acceptance of steel sleeve grouting joints.
Grouting sleeves are categorized by manufacturing method into cast and mechanically processed types. Cast sleeves are made from ductile iron, while mechanically processed sleeves use high-quality carbon structural steel, low-alloy high-strength steel, alloy structural steel, or other steels that have passed joint type testing and meet required standards.
Design, production, and manufacturing of grouting sleeves must adhere to the current industry standard “Grouting Sleeves for Steel Bar Connections” (JG/T 398). The specialized cement-based grout must meet the “Grouting Material for Steel Bar Connection Sleeves” standard (JG/T 408). If sleeves are made from other materials, their performance indicators must comply with applicable product standards.
Main performance criteria for sleeve materials:
– Ductile iron sleeves must have a tensile strength of at least 550 MPa, elongation at break no less than 5%, and a spheroidization rate of at least 85%.
– Steel sleeves must have tensile strength ≥ 600 MPa, yield strength ≥ 355 MPa, and elongation at break ≥ 16%.
– Sleeves made from alternative materials must meet corresponding product standards.
Main performance criteria for grouting materials:
– Initial flowability ≥ 300 mm
– Flowability after 30 minutes ≥ 260 mm
– Compressive strength after 1 day ≥ 35 MPa
– Compressive strength after 28 days ≥ 85 MPa
When elongation and other requirements are met, sleeve materials with tensile strengths above 600 MPa (such as 900 MPa or 1000 MPa) can be used to reduce sleeve wall thickness and outer diameter. Other high-strength steels may also be used depending on production methods. Grouts exceeding 85 MPa compressive strength (e.g., 110 MPa or 130 MPa) can connect large-diameter or high-strength steel bars and shorten sleeve lengths while maintaining required fluidity and other properties.
4.8.3 Scope of Application
This technology is suitable for connecting HRB400 and HRB500 steel bars ranging from 12 to 40 mm in diameter within assembled integral concrete structures. Typical applications include longitudinal load-bearing steel bars in prefabricated frame columns, integrated decorative prefabricated beams, and vertical steel bars in prefabricated shear walls. It can also be applied to vertical and horizontal steel bar connections in cast-in-place structures during renovation of existing buildings.
4.8.4 Engineering Examples
Projects utilizing this technology include Beijing Changyang Peninsula, Ziyun Community, Changyang Tiandi, Jinyu Huafu, Shenyang Chunheli, Shenyang Twelve Games Security Center, Nanke Fortune Building, CR Ziyun Mansion, Vanke Tiexi Blue Mountain, Changchun FAW Technology Center Parking Building, Dalian Vanke City, Nanjing Shangfang Youth Apartment, Vanke Jiudu Hui, Hefei Shushan Phase IV Public Rental Housing, Luyang Lake New City, Shanghai She Bei Large Residential Community, Qingpu New City, Pudong New Area Minle Large Residential Community, Longxin Elderly Apartment, Longxin Square, Zhongnan Century City, Chengdu Jinfeng New City, Xi’an Xingsheng Community, Wulumuqi Longxi Jiayuan, Fujian Jianchao Industrial Building, among others.
Must log in before commenting!
Sign Up