Reinforcement with rebar-planting adhesive is one of the commonly used reinforcement methods, which has the advantages of low cost, high efficiency and good reinforcement effect. Its principle is to closely combine steel bars with concrete by utilizing the strong adhesive force of the rebar-planting adhesive, and to provide the load-bearing capacity of the concrete structure by taking advantage of the toughness of the steel bars, so as to achieve the purpose of seismic reinforcement. Generally speaking, rebar-planting reinforcement is applicable to a wide range of building types, but not all components are suitable for it. Since rebar-planting requires drilling holes, certain requirements are imposed on concrete components.

Requirements for Concrete Substrate in Rebar-Planting

I. Requirements for Concrete Strength

If the concrete strength is too low, it may not be able to achieve the purpose of jointly bearing loads with the implanted steel bars. During the destructive pull-out test, the concrete may break and collapse while the bond between the steel bars and the rebar-planting adhesive remains intact. Therefore, the concrete strength for rebar-planting reinforcement shall not be lower than C20. It is stipulated in national standards that when the newly added component is a cantilever component, the working strength grade of the original concrete component shall not be less than C25; when the newly added component is other structural components, the design strength grade of the original concrete material shall not be less than C20, and there shall be no local defects. If there are local defects, they should be strengthened or reinforced first.

II. Requirements for Concrete Condition

If cracks, damages or other situations occur in concrete components themselves, rebar-planting reinforcement cannot be carried out. If rebar-planting must be done, it is necessary to maintain and reinforce the concrete first before the rebar-planting construction.

III. Requirements for Concrete Thickness

Since rebar-planting construction requires drilling holes in components and there are requirements for the drilling depth, which is generally 15 times the diameter of the steel bar, the concrete component is also required to have a certain thickness. If the concrete thickness is insufficient and rebar-planting is forced, only shallow holes can be drilled and a small amount of adhesive can be injected, and it cannot be ensured that the steel bars, the rebar-planting adhesive and the concrete are completely bonded. In this case, if rebar-planting is forced, it is easy to bury potential safety hazards.

IV. Requirements for Concrete Material Density

If the concrete material is too dense and the reinforcement ratio is high, it will also cause difficulties for drilling. The larger the diameter of the steel bar, the more prominent this problem will be. For example, if the designed drilling diameter is 31 mm, but sometimes the clear distance between the main bars of the substrate is only 28 mm, holes cannot be formed.

The reinforcement of the substrate concrete is beneficial for the transfer and diffusion of the anchoring steel bar load to a wider range and for the improvement of the anchoring force. Theoretically speaking, the higher the strength of the substrate and the denser the reinforcement, the relatively higher the anchoring will be.

The above are the requirements for concrete in rebar-planting adhesive reinforcement. During rebar-planting reinforcement, construction personnel need to first check the strength, thickness and condition of the concrete to ensure that they are correct, and then carry out rebar-planting.