Repair Of Roof Beams And Slabs Of A High-span Workshop

1 Project Overview

The high-span workshop of the Changzhou Plant of CSSC Huangpu Wenchong Shipbuilding Co., Ltd. is a single-story bent frame factory building with a precast concrete beam-slab roof structure. The high-span section was completed in 1972, and the extension section was completed in 2004, with a construction area of approximately 11748m2.

According to the site survey and the report provided by the appraisal unit, the main concrete diseases in this project include moldy and shedding of the protective layer of the roof beams, corrosion of steel bars, multiple leaks, and corrosion of the roof steel beam structure.

After in-depth discussion by our company, the roof beam slab is due to the thickness of the original roof slab concrete protective layer that does not meet the specification requirements. The moisture in the surrounding environment of the workshop accelerates the carbonization of the concrete under the roof slab and reduces the alkalinity of the concrete. The damage of the passivation film on the surface of the steel bar leads to the corrosion of the steel bar. In addition, due to the long-term disrepair and failure of the waterproof surface of the roof slab, the concrete slab is eroded by rain for a long time, and the corrosion of the steel bar intensifies the rust and swells, forcing the concrete protective layer to peel off. The roof steel beam structure is caused by the lack of daily durability maintenance and other reasons.

According to the above disease analysis, concrete floor slabs have different degrees of problems in terms of structural safety and durability. In order to ensure the safety and durability of the concrete beam and slab structure, restore the original functions of the various components of the concrete beam and slab structure, and meet the technical standard requirements of the concrete beam and slab structure, the concrete beam and slab structure should be repaired and reinforced immediately. Prevent the disease from further aggravating. Otherwise, the structural safety and service life of the concrete beam-slab structure cannot be guaranteed.

For the corrosion of steel bars caused by the peeling of part of the concrete, the loose concrete should be removed first, and the corroded steel bars should be derusted. Then apply anti-rust paint on the steel bars, and finally use the carbon fiber grid spray mortar reinforcement system for reinforcement.

2 Carbon fiber mesh reinforcement scheme

2.1 Advantages of carbon fiber grid reinforcement method Compared with ordinary carbon fiber reinforcement methods, the advantages of carbon fiber grid reinforcement method are mainly:

(1) The reinforcement strength is high, and its reinforcement effect is roughly equivalent to φ6mm@150mm steel mesh.

(2) After the overall reinforcement, the thickness of the sprayed mortar is thin, which can improve the mechanical properties of the structure without changing the cross-sectional size of the structure.

(3) The ability to restrain the structure is strong, so that it has an excellent ability to control the crack propagation.

(4) The active ingredients in the mortar ensure the bonding strength between the carbon fiber grid and the concrete, while the sprayed mortar ensures the joint action of the carbon fiber grid and the concrete, and the reinforcement effect is good.

(5) Carbon fiber is an inert material with strong corrosion resistance. It is suitable for repairing parts directly in contact with rainwater such as roof beams and slabs in factories.

(6) The construction and laying are convenient and easy to carry out, and it is suitable for the structure of the factory building with large building area and simple structural force.

(7) Good fire resistance, 1cm mortar protective layer can meet the requirements of F60 in ISO834 for fire resistance and flame resistance test of building materials.

2.2 Carbon fiber grid construction technology

The carbon fiber mesh can be used in conjunction with the wet-process polymer mortar to strengthen and repair the structure.

1) Surface treatment

2) Mortar mixing

3) Spray the first layer of polymer mortar

4) Cutting and laying of carbon fiber grid

5) Spray the second layer of polymer mortar

6) Curing and surface treatment of mortar

3 Conclusion

Carbon fiber reinforcement method is a common structural reinforcement method, which has the characteristics of convenient construction, simple operation and little impact on the structure itself. However, the carbon fiber grid reinforcement method not only inherits the advantages of the original carbon fiber materials used in the form of sheets and ribs in structural reinforcement, but also greatly improves its mechanical properties, standardization of construction, and economic benefits. Therefore, the research and implementation of the carbon fiber grid reinforcement method and its supporting high-strength polymer mortar is one of the important development directions of the structural reinforcement industry in the future.