Reinforcement planting and anchoring adhesive

Reinforcement planting and anchoring adhesive

an adhesive 　
Bonded rebars

[　 application 3]　
Application of planting bar technology in reconstruction and reinforcement project
1　 Principle of planting reinforcement technology
The planting bar connection technology is a new type of reinforced concrete structure transformation technology, which belongs to a post anchoring technology. It is a method of taking concrete, etc. as the base material, drilling, cleaning, injecting * * * chemical adhesive (commonly known as structural adhesive) and implanting the required reinforcement on the old concrete component according to the number, specification and position of reinforcement determined by structural stress analysis, so that the reinforcement can be anchored into the old structural component, and then pouring new concrete for effective connection, In order to achieve the reinforcement and reconstruction technology of joint action and overall stress. The liquid rebar planting glue will penetrate into the cracks and pores of the concrete in the concrete. After the solidification * * * in the normal temperature range in Table 1, it will not only produce friction, but also produce a locking force between the concrete and the rebar. Therefore, the required reliable bonding force between the embedded rebar and the old concrete can be obtained by using this adhesion and locking principle. 　
surface 1　 Setting time of rebar planting adhesive

2　 Advantages of planting reinforcement technology
1) It has the advantage of flexible design. The number and specification of planting bars can be designed at any position of the reinforced concrete according to the structural stress characteristics according to the needs of the use function of the structure, and the reliability is better than the embedded parts. It can be used for horizontal, vertical and top device bearing; 2) The embedded steel bar structure is firm, which can produce high load bearing capacity after construction, can resist shear force and tension, and is not easy to produce displacement. It is pulled out, and has good sealing performance, without any waterproof treatment; 3) For the implanted substrate, no expansion force is produced, and the anchorage strength can be exerted to a greater extent; 4) It is applicable to a wide range of base materials, and can be used for various solid and hollow building materials such as concrete, lightweight concrete, slag concrete, natural stone, etc; 5) The operation is fast and simple, the binder hardens rapidly, and the strength is high, which can effectively shorten the construction period; 6) It has a wide range of applications, and can be used for various structural reinforcement and reconstruction and expansion projects of old buildings, and is safe and environmentally friendly.
3　 Applicable scope and position of planting reinforcement technology
1) Anchoring of reserved steel bars for storey addition, continuation, reconstruction and expansion of various reinforced concrete structures; 2) The continuous connection of beams, columns, floors and shear walls and the anchoring of reinforcement reserved reinforcement between beams and columns, slabs and columns, beams and shear walls, foundation beams and column caps; 3) Anchoring of reserved reinforcement for reinforcement of bridges, culverts, tunnels and other special structures; 4) All kinds of steel structures and mechanical equipment, screw anchoring of supports, and anchoring of metal profiles with base materials such as concrete, rock, brick walls, etc.
4　 Three elements of rebar planting process
1) Rebar planting glue (also called anchoring glue): the anchoring performance of anchoring glue used for chemical rebar planting shall be determined through special tests. For the approved anchoring glue, in addition to the instructions, quantitative admixtures can be added, and other admixtures should not be added during site construction. Anchoring adhesive can be divided into pipe mounted, mechanical injection type and on-site preparation type according to the use form. During construction, it shall be reasonably selected according to the characteristics of the objects and site conditions. However, no matter what type of anchoring adhesive is selected, its performance indicators should meet the relevant provisions of the national standard JGJ 145 － 2004.
2) Smaller value of reinforcement * * *: I　 b min ≥ 20d ≥ 24 0 ㎜ 。 Where, d is the diameter of embedded reinforcement; 　 I　 B is the implantation of reinforcement when yielding * * *.
3) The determination of the diameter and depth of embedded reinforcement is shown in Table 2.
5　 Process flow of planting reinforcement
Remove concrete protective layer → position and set out rebar planting → drilling → hole cleaning → secondary drilling → roughening → secondary hole cleaning → verify the hole diameter and depth → dry and clean the hole → prepare rebar planting structural adhesive → clean the rebar → inject rebar planting adhesive into the hole → implant and solidify the rebar and temporarily fix and protect it → rebar planting and pull-out test * * * → connect the implanted rebar with the newly added structural rebar after acceptance → Formwork erection and fixation → new structure pouring and tamping concrete. 　
surface 2　 Rebar model, aperture and implantation of planting rebar design***

6　 Quality control requirements and precautions for planting reinforcement
1) Requirements for rebar planting adhesive: it must have the factory certificate and date of production, and it is in the warranty period. The on-site ratio must be accurate and reasonable. 2) The embedded rebar must have a factory certificate, factory date and test report, and be qualified in * * *. It can only be used after rust and oil removal treatment. 3) Before planting reinforcement, the drill hole shall be cleaned to ensure that the hole is free of dust, dry, and the key indicators such as hole depth and aperture meet the design requirements before entering the next process. 4) Before the formal construction, the anti pulling test of embedded reinforcement shall be carried out on site, and the * * * construction can be carried out only after it is qualified. 5) Low temperature, rainy and other bad weather shall be avoided during rebar planting. 6) The newly embedded rebar shall be temporarily fixed, and can be removed only after the rebar planting glue is completely solidified, and shall not be moved during the curing period. 7) After planting reinforcement, anti pulling test must be carried out for planting reinforcement according to the design requirements. (If the design does not require 10% * * *) The next process can be started only after it is qualified. 8) Although the rebar planting glue is * * *, there is no strong * * * smell, but the adhesive force is * * * strong. During construction, try to avoid direct contact between * * * and the rebar planting glue. 　
7　 Application of planting reinforcement technology in practical projects
In practical projects, the planting reinforcement technology has been widely used in the reconstruction, expansion and reinforcement of various structures, and most of them have achieved the expected results. For example, the courtyard structure of Guangzhou Jinmao Mansion, which was originally designed as a 35 story shared space, was changed into a cast-in-place reinforced concrete cantilever slab structure. Due to the change of use function, the roof panel of a building in Kunming was thickened and the plate was supplemented. As well as the commercial and residential building No. 44, Century Garden, Xianda Real Estate, Guilin, which is under construction now, the original project has completed part of the foundation and underground garage construction in 1997. Due to the change of its use function, the original foundation beams, slabs, columns, shear walls, etc. are strengthened by planting reinforcement technology, and its superstructure is changed from the original frame brick concrete structure to the frame shear small high-rise structure. 　
Rebar diameter → planted rebar * * * → concrete strength. The research also shows that, on the premise of meeting the structural strength requirements, and the structure is complete and reliable, from the perspective of economy, practicality and ease of construction, the smaller the steel bar diameter is, the better. This not only reduces the amount of rebar planting glue, facilitates the hole forming construction, and reduces the damage to the original structure, thus saving investment. On the premise of meeting the design strength requirements of planting reinforcement engineering such as structural reinforcement, structural leakage repair and structural modification, the smaller the concrete strength, the better, because the concrete strength is smaller, it is easy to form holes, and the construction is convenient.

Sticking steel technology Sticking steel reinforcement is a reinforcement method that uses * * * building structure adhesive to stick thin steel plates (2~6mm thick) on the surface of concrete members to supplement the insufficient reinforcement inside the members, so as to improve the structural bearing capacity of concrete members. It can be used for the reinforcement of concrete structures with insufficient bearing capacity of concrete structural members due to improper design or construction, material quality not meeting Colombo's requirements, use function change, disaster and durability.
Steel cladding technology The column encased steel reinforcement technology is that after the angle steel and the plate hoop are welded, * * * inorganic bonding materials or epoxy grout is poured under pressure to make them reliably connected with the original concrete column as a whole. This strengthening method uses the transverse action of new angle steel and steel hoop to achieve the bearing capacity of high columns with large triaxial restraint energy.
Steel bar planting technology According to the strength of the base material, the different characteristics and functional requirements of the reinforcement or connection parts, the imported glue or * * * structural anchor glue is used, and the reinforcement or bolts are embedded in the base material to achieve reliable connection of the components, which is equivalent to adding embedded steel components to the structure. It is widely used in reconstruction and expansion projects such as adding awnings, balconies, cantilever beams, connecting columns, expanding column sections, and enlarging foundations.

Operation Instruction for Planting Rebar Glue

1　 General

1.1 In order to make the application of rebar planting glue in the reinforcement of reinforced concrete structure, the technology is advanced, economic, reasonable, safe and reliable.

1.2 This instruction is applicable to the design and construction of planting reinforcement in reinforced concrete structures.

1.3 When planting reinforcement in reinforced concrete structures with planting adhesive, in addition to the provisions of this Guide, the provisions of current national standards and specifications shall also be observed. The anchoring parameters can be adjusted according to the results of the field pull-out test.

1.4 When planting reinforcement in reinforced concrete structures with planting adhesive, the design shall be carried out by professional designers, and the construction shall be carried out by professional construction teams with construction experience.

1.5 The strength grade of the concrete base material should not be less than C15. When the strength grade of the base material is greater than C30, the planting bar parameter (anchoring * * *) is still considered as C30.

1.6 The anchoring of rock, brick and other solid substrates can be carried out according to this instruction.

2　 Explanation of terms and symbols
　　　 Gelling time - the time from the mixing of resin mastic and curing agent to the heating of anchoring adhesive (the temperature of mastic rises by 2 ℃).
Curing time - the time from the mixing of anchoring adhesive A and curing agent B to the end of the reaction.
As - sectional area of anchor bar;
D - Borehole diameter;
D - diameter of anchor bar;
F cr - standard value of bond strength between rebar planting glue and concrete;
F yk - standard value of anchor bar strength;
L - effective anchorage * * *;
L b - yield anchorage of anchor bar * * *;
N sd - design value of single anchor bar tension, or design value of larger tension in group anchor bars;
N Rk, s - standard value of tensile bearing capacity of anchor bar;
N Rk, c - standard value of bond bearing capacity between rebar planting glue and concrete interface;
V sd - shear design value of single anchor bar or larger shear design value of group anchor bars;
V RK, s - standard value of shear bearing capacity of anchor bar;
Y mc - partial coefficient of bond bearing capacity between rebar planting glue and concrete interface;
Y ms - partial coefficient of tensile or shear bearing capacity of anchor bar;
V - specific gravity of rebar planting glue, 2;
K - Excess coefficient of drilling glue, 1.1;
W - Amount of rebar planting glue.

3　 Features and application range of planting adhesive

3.1 Product characteristics

(1) This product is used for reinforced concrete, as well as reinforcement anchorage of brick wall, rock and other base materials

(2) Fast bearing, large drawing force, * * *, anti vibration

(3) The construction is fast and convenient, and the horizontal hole and upward hole are easy to construct and can ensure that the hole is filled with glue

(4) The anchoring effect is similar to that of pre embedding, and the cost is low

(5) It can be solidified under negative temperature (- 15 ℃) without affecting the anchoring force

(6) The anchoring reinforcement can be welded after solidification

3.2 Scope of application

(1) Enlarged section planting reinforcement of beam and column, corbel and horizontal planting reinforcement of column

(2) Wall thickening, tie bar planting

(3) Vertical planting bar of column head for structural layering

(4) Beam body extension horizontal planting bar

(5) Beam and slab cantilever horizontal planting bar, column on beam, vertical planting bar

(6) Foundation and continuous wall planting reinforcement

(7) Prefabricated beam repair and rebar planting

(8) Embedded parts of curtain wall

(9) Aerial rooting

(10) Advertising board footing fixation, mechanical equipment fixation, etc

(11) Anchorage of rock and brick masonry

4　 Material Science

4.1 Base material
The main anchoring base materials for planting steel bars are reinforced concrete, prestressed concrete structures and brick walls. Anchor bars are often used as tie bars when strengthening brick walls. The strength grade of concrete should be between C15 and C60.
The strength of concrete base material has a significant impact on the anchorage force of embedded bars. The lower the concrete strength is, the lower the anchorage force of embedded bars is; The higher the concrete strength is, the higher the anchoring force of embedded reinforcement is. However, the anchoring force of embedded reinforcement is not linear with the concrete strength.

4.2 Reinforcement
Grade II and Grade III rebars shall be preferentially used for structural planting rebar.
Grade I reinforcement can be used for wall tie planting reinforcement.

4 ． 3
Planting adhesive

4.3.1 See Table 4.3.1 for the mechanical property parameters of planting adhesive.

Mechanical properties of rebar planting glue

4.3.2 The influence of temperature on the curing time of adhesive is shown in Table 4.3.2

Influence of temperature on curing time Table 4.3.2

4.3.3 See Table 4.3.3 for the influence of welding on anchoring force.

Table 4.3.3 Influence of Welding on Anchoring Force

Figure 4.3.3

4.3.4 Influence of drilling humidity on anchoring force

The impact of water in the borehole on the anchoring force is obvious, and the anchoring force will be reduced. It is advisable to use heating and drying measures before construction, as shown in Table 4.3.4.

Table 4.3.4 Influence of Drilling Humidity on Anchoring Force

4.3.5 See Table 4.3.5 for the impact of construction hole cleaning on anchoring force.

Table 4.3.5 Impact of hole cleaning on anchoring force

4.3.6 See Table 4.3.6 for the influence of drilling hole direction on anchoring force.

Table 4.3.6 Influence of Orifice Direction on Anchoring Force

4.3.7 See Table 4.3.7 for the relationship between the drilling diameter and the corresponding value of anchor bar diameter.

Table 4.3.7 Relation between Borehole Diameter and Anchor Bar Diameter

4.3.8 Calculation of drilling glue consumption
Experience consumption: 2/3 of the drilling hole shall be filled.
Calculation amount: W=π/4 (D 2 － d 2) h ef · v · K
In the formula, v - specific gravity of rebar planting glue is 2; K -- Excess coefficient of drilling glue is 1.1;
H ef - effective anchorage * * *; W -- Amount of rebar planting glue

5　 Design and construction

5.1 General provisions

(1) The design of anchor bars shall be based on the load distribution of members and the relevant provisions of the Load Code for the Design of Building Structures, and the design values of the large tensile force of single anchor and group anchor bars or the composite tensile force and shear internal force under the combined action of tension and bending shall be calculated.

(2) Safety level importance coefficient

According to the importance of the project and the severity of the consequences of anchor failure, the design value should be multiplied by the corresponding safety level importance coefficient, as shown in Table 5.1.

Table 5.1 Safety Level Importance Coefficient

(3) Failure type of anchoring component

Through a series of tests and many years of engineering practice, anchoring is carried out in reinforced concrete components. The failure of anchoring components usually has two conditions, namely, the failure of anchoring bars, the failure of anchoring adhesive and the failure of concrete substrate. The failure of anchoring adhesive can be divided into the failure along the interface between anchor bar and adhesive, and the failure of concrete and adhesive.

(i) When the anchor * * * is greater than or equal to the smaller yield anchor * * * of the anchor bar, the failure of the anchor bar usually plays a controlling role.

(ii) When the anchoring * * * is smaller than the smaller yield anchoring * * * of the anchor bar, the anchoring component may be damaged by the anchoring adhesive and the concrete substrate. Under the same bond length, the possibility of failure along the interface between anchor bar and adhesive is far less than that between adhesive and concrete, so the failure of the interface between anchor bar and concrete plays a controlling role.

(4) Considering that the reinforced concrete members are affected by such uncertain factors as long-term carbonization, freeze-thaw, corrosion, wear and tear, resulting in large dispersion of concrete strength, the bearing capacity of the anchor is multiplied by the reduction factor ф.

5.2 Checking calculation of bearing capacity of anchor components

5.2.1 Checking calculation of tensile bearing capacity of anchor bar

The tensile bearing capacity of anchor bar shall be calculated according to Formula (5.2.1)
　　 N sd ≤ фN RK ， S /Y ms (5 ． 2 ． 1)
Where, N sd is the design value of single anchor bar tension, or the design value of larger tension in group anchor bars.
N RK, S -- standard value of tensile bearing capacity of anchor bar.
Y ms - partial coefficient of tensile bearing capacity of anchor bar, see Table 5.2.
ф - reduction coefficient of bearing capacity, its value is 0.8.

Partial factors of anchor bearing capacity Table 5.2

5.2.1.1 The standard value of tensile bearing capacity of anchor bar shall be calculated according to Formula 5.2.1 and 1
　　 N RK,s =A s ·f yk (5 ． 2 ． 1 ． 1)
Where, A S - sectional area of anchor bar;
F yk -- standard value of anchor bar strength.

5.2.2 The bonding bearing capacity of the interface between the anchoring adhesive and the concrete shall be as per Formula 5; 2.2 Calculation
　　 N sd ≤ ф N Rk,c / Y mc (5 ． 2 ． 2)
Where, N sd -- design value of tensile force of single anchor bar or design value of larger tensile force of group anchor bars
N Rk, c - standard value of bond bearing capacity of anchorage adhesive and concrete interface
Y mc - partial coefficient of bond bearing capacity of anchorage adhesive and concrete interface
ф - reduction coefficient of bearing capacity, which is 0.8

5.2.2.1 The standard value of the bond bearing capacity between the anchorage adhesive and the concrete interface shall be calculated according to Formula 5.2.2.1
　　 N Rk,c = π D·L·f cr (5 ． 2 ． 2 ． 1)
Where, D - drilling diameter
L - effective anchorage***
F cr -- standard value of bond strength between anchor adhesive and concrete, which is 6~7MPa

5.2.3 Shear checking calculation of anchor bar
When the anchor * * * of the anchor bar is not less than the yield anchor * * * of the anchor bar in tension, the shear checking calculation of the anchor member, considering that the shear force is borne by the anchor bar, is calculated according to Formula 5.2.3
　　 V sd ≤ фV RK,S /Y ms (5 ． 2 ． 3)
Where, V sd - design value of shear force of single anchor bar or larger shear force of group anchor bars
V RK, S - standard value of shear bearing capacity of anchor bar
ф - reduction coefficient of bearing capacity, which is 0.8
Y ms - partial coefficient of shear bearing capacity of anchor bar

5.2.3.1 The standard value of shear bearing capacity of anchor bar shall be calculated according to Formula 5.2.3.1
　　 V RK,s =0.6 A s ·f yk (5 ． 2 ． 3 ． 1)
Where, As - sectional area of anchor bar
F yk - standard value of tensile strength of anchor bar

5.2.4 Checking calculation of tension shear composite bearing capacity
When the anchor bar is under the combined stress state of tension and shear, the bearing capacity of anchor bar failure shall be checked according to Formula 5.2.4.
　　 (N sd /N Rds ) 2 ( V sd / V Rds ) 2 ≤ 1 (5 ． 2 ． 4)
Where N Rds=N Rks/r ms
　　 V Rds =V Rks / r ms

5.3 Practical table of standard value and design value of tensile bearing capacity of anchor bar series
In order to simplify the calculation and facilitate the design, we comprehensively consider the series of test and engineering practice data, and combine a series of calculations of Formula (5.2.1), (5.2.2) and (5.2.3) to provide the standard value and design value of anchor bar bearing capacity for different concrete strength grades. The designer calculates the internal force design value of a single anchor bar according to the internal force analysis, and calculates the corresponding anchor bar diameter, anchor * * *, drill hole diameter and anchor bar quantity by multiplying the corresponding coefficient with the relevant provisions in Table 4.3.4-4.3.6.

5.4 Structure
5.4.1 The strength of the anchored reinforced concrete base material should not be less than C15, the thickness of the base material should be greater than or equal to L 2D, and should not be less than 100mm, where L is the effective anchoring of the anchor bar * *, and D is the diameter of the drill hole.
5.4.2 The anchor bars shall be arranged away from the decoration layer and the plastering layer. If they cannot be avoided, their thickness shall be deducted, and they shall be better arranged in the area with reinforcement arrangement, as shown in Figure 5.4.2.
5.4.3 The spacing and edge distance of group anchor bars shall be greater than or equal to 4 times the diameter of anchor bars. When the edge distance is less than 0.5 times the embedded depth of anchor bars, it is required to have at least one ф 6 bar within the edge distance range, otherwise the edge distance value shall be increased.
5.4.4 When anchor bars are used to anchor decorative components such as curtain walls, the thickness of anchor plates should not be greater than 12mm or less than 8mm, and the diameter of anchor bars should be controlled at 10, 12, 14, 16 mm.

Figure 5.4.2 Schematic Diagram of Anchor Bar Setting Position

6　 construction

6.1 Drilling
Use electric hammer or other equipment to drill holes with proper hole diameter and depth.

6.2 Hole cleaning
(1) Clean the dust on the hole wall repeatedly with a brush; (2) Blow the dust on the hole wall from the hole bottom with strong wind; (3) Repeat steps (1) and (2) at least three times until there is no dust on the hole wall.

6.3 Glue injection
Fully mix material A and material B in the rebar planting glue (see the product specification for the ratio of material A and material B), and put them into the hole. The amount of glue should meet the requirements of full filling of the glue in the hole after the rebar is inserted.

6.4 Reinforcement planting
Insert the anchor into the hole (rotation or vibration can be used), and it is forbidden to disturb the anchor before curing the adhesive, so as not to affect the anchoring effect.

Construction Diagram

7　 testing

7.1 Product delivery test
The rebar planting glue has passed a series of performance tests before leaving the factory. The test basis is GBJ81-85 JC/T547 — 94 、 MTl46.1 — 95 、 Product enterprise standards, etc.

7.1.1 Raw material inspection
All raw materials are supplied by designated manufacturers, and each batch of incoming raw materials is inspected before use. Those whose performance fails to meet the requirements are not allowed to be used, so as to ensure the quality of raw materials.

7.1.2 Production process inspection
Each production process is in the charge of a specially assigned person, and self inspection is carried out. The unqualified ones will not be produced in the next process, and the product quality will be guaranteed from the production process.

7.1.3 Delivery inspection
Each batch of products shall be tested for anchorage mechanical properties before delivery, and each group of test pieces shall not be less than 3. The test shall be conducted according to the enterprise standard, and unqualified products are strictly prohibited from leaving the factory.

7.1.4 Inspection by National Quality Inspection Center
Every year, the products are sent to the relevant national quality testing center for inspection and are recognized by the department for quality.

7.2 Field pull-out test
According to the user's requirements, the relevant quality inspection center recognized by the state shall be entrusted to carry out the field pull-out test.

[　 Application Example 4

Engineering application of anchoring adhesive

Epoxy resin adhesive has many advantages such as excellent mechanical properties, mechanical properties, chemical media resistance, aging resistance and good construction performance. Since its appearance, it has been widely used in many occasions such as bonding reinforcement, anchoring and planting reinforcement, grouting and joint repair, waterproof and leakage stoppage, corrosion prevention, etc. in building engineering, bridge engineering, highway engineering, etc. The anchoring and planting reinforcement technology is one of the important applications, which is to anchor the reinforcement or bolt in the pre drilled concrete structure through the building structural adhesive, so as to enhance the strength of the concrete structure and extend its service life.
This paper introduces the important parameters of the formulation design, material selection and application value of epoxy resin adhesive.

1　 Selection of raw materials and determination of main technical indicators

1.1 Selection of epoxy resin and its main parameters
The epoxy resin adopts low molecular weight epoxy resin, such as E-44 (6101 type), E-42 (634 type), E-51 (618 type). E-44 (6101 type) is more commonly used, and E-44 (6101 type) is selected in this paper. Its appearance is light * * * or brown * * * viscous transparent liquid, molecular weight is 350-450, oxygen equivalent (g/Eq) 210~240, * * * chlorine (equivalent/100g) ≤ 0.02, inorganic chlorine (equivalent/100g)

1.2 Selection of curing agent and its main parameters
Curing agent generally includes T31, C20, ethylene diamine, etc. This paper uses ethylene diamine, which is a strong alkaline colorless liquid with fast curing speed, volatility, and odor. It is a commonly used curing agent with purity>90% and water content

1.3 Selection of diluent
The diluent is non active diluent acetone, which does not participate in curing reaction, does not change chemically with epoxy resin, has good dilution effect, and is relatively less toxic.

1.4 Selection of toughening agent
Toughening agent is mainly used to improve the brittleness of epoxy resin and improve the bending and impact strength of products. This method uses dibutyl phthalate.

1.5 Selection of filler
This method uses ordinary silica 42.5 cement, which shall not be caked, and shall be screened through 4900 holes/cm2, with a sieve residue of no more than 15%.

2　 Test analysis and main reaction mechanism of epoxy resin adhesive
2.1 Test overview
Grade II deformed steel bars are used for the design and treatment of test planting bars. Divide into 5 groups according to the diameter: 6.5, 8, 10, 12, 14; Each group consists of 3 rebars, embedded * * * is 15 times the diameter of the rebar, polished and derusted to expose metallic luster before planting the rebar, and the anchor end is cleaned with acetone. Hole diameter and hole treatment: the diameter of the drill hole is 10%~20% larger than the diameter of the planted reinforcement, generally 20%. After the drill hole is blown clean by a blower, it is cleaned with acetone.
After a lot of experiments, orthogonal design, formula design and performance tests, an epoxy resin adhesive was developed. Its basic components are shown in Table 1.
The epoxy resin adhesive entrusts Tianjin Construction Engineering Quality Supervision and Inspection Center to carry out the pull-out test. Grade II deformed steel bars are used, and the concrete strength grade is C30. See Table 2 for the test results
From the test results, it can be seen that under the action of the external pulling force, the anchorage reinforcement can be damaged in two forms: ① the reinforcement yielding, ② the reinforcement pulling out. Both of these conditions meet the requirements of structural planting reinforcement.

Table 1 Basic composition of epoxy resin adhesive

Table 2 Results of anchor bar pull-out test

Note: d　 —　 Rebar diameter D　 —　 Borehole diameter L　 —　 Drilling***

2.2 Main reaction mechanism of epoxy resin adhesive
The reaction formula of polyamine and epoxy group is as follows:

Addition curing reaction of liquid bisphenol A epoxy resin with ethylene diamine, К 1 К 2 =0.5/1 ； Addition curing reaction of liquid bisphenol A epoxy resin with aromatic amine, К 1 К 2=(0.14-0.08)/1. That is, the addition reaction rate of primary amine and epoxy group is significantly higher than that of secondary amine and epoxy group. The hydroxyl generated in the reaction promotes the addition curing reaction of ammonia (amine) based on epoxy group, which is called autocatalytic effect. When ethylene diamine and epoxy resin undergo addition curing reaction at 80 ℃, the relationship between reaction time of various functional groups is shown in Figure 1.

Curing reaction time /min

Figure 1 Relationship between functional group change and curing reaction time
　　　 For the reaction of liquid bisphenol A epoxy resin with aliphatic diamines, in the isothermal speed curve without external accelerator, due to the post curing of unreacted functional groups, an exothermic peak is generated. In the peak region, the post curing reaction mainly caused by the autocatalytic effect of the hydroxyl group of the cured product is a third-order reaction. When the conversion rate of epoxy resin is 55%~75%, the diffusion rate of products is limited due to the increase of reaction system viscosity, and the consumption rate of reactants drops sharply when epoxy resin reacts with nearly equivalent diamine. When the addition curing reaction between bifunctional epoxy resin and tetrafunctional amine takes place, the critical conversion rate for forming an infinite cross-linking network is 58%. The post curing reaction of aliphatic diamine with liquid bisphenol A epoxy resin is shown in Figure 2.

Figure 2 DSC of post curing reaction between liquid epoxy resin and ethylene diamine curve

3. Engineering application and technical analysis of epoxy resin adhesive technology
3.1 Project overview
An engineering training center is located in Beichen District, Tianjin. It is a three storey frame structure. According to the use needs, it is planned to cover an activity room with an area of about 2200m2 on the top floor. In the original design, structural glue was required to be used for the rooting construction of grouted and rebar planting columns. After being approved by the design, self prepared high-performance epoxy resin glue was used for rebar planting. 78 ф 20HRB335 rebars are embedded on the original roof column.

3.2 Quality inspection
Due to the tight construction period and high quality requirements of the project, the pull-out force test of planting bars was carried out on two test bars three days after planting bars. Under the design load, the planting bars only produced elastic deformation, and there was no damage, cracking, shrinkage and other phenomena of mortar in the tunnel, which fully met the design requirements.

3.3 Economic benefit analysis
The construction cost is 8580 yuan if the structural adhesive is used in the original design, while the cost is only 5491 yuan if the self prepared epoxy resin adhesive is used in the construction, which reduces by 36% and achieves high economic benefits.

3.4 Technical analysis
Through engineering practice, we believe that the epoxy resin adhesive rebar planting technology has the following advantages:
(1) Reliable quality, safe performance, little damage to existing structures, especially the problem of tight connection between new and old structures. If the structural reinforcement is embedded in the old structure according to the old construction method, it is necessary to drill holes and then fill the holes with cement mortar. The drilling * * * needs to meet the anchorage length of the reinforcement, which * * * is about 2.5 times of the planting * * *, and the hole diameter is large, generally more than 30 mm. The hole filling mortar is difficult to firmly combine with the old concrete, becoming the weak link of the structure. If it is necessary to connect the new reinforcement with the original reinforcement mesh, it is necessary to chisel away the concrete in a large area to expose the structural reinforcement before welding. Due to the thermal effect of chiseling concrete and welding, the original concrete is greatly damaged, so it is called "breaking muscles and bones". The planting steel bar technology has shallow hole depth, small hole diameter and firm bonding, which eliminates the potential quality hazard.
(2) Design flexibility: according to the use needs, the number and specification of planting bars can be designed at any position of reinforced concrete according to the structural stress characteristics.
(3) The stress is even than that of ordinary riveting and welding, the material will not produce stress concentration (such as thermal effect during welding), and the planted rebar is more resistant to fatigue. (4) The process is simple, which can greatly reduce the construction period, and can be used in 1-2 days or less.
(5) Low cost: Take the anchor between the frame column and the block infilled wall with more planting bars as an example, after the survey of the construction unit, it is generally possible to plant 100 anchor bars per kilogram of structural planting bar glue, and the cost of the structural glue used for planting bars is less than 0.5 yuan. Because the construction process of planting anchor bars is simple, ordinary steel workers can operate, and at least 50 anchor bars can be planted per workday, The comprehensive cost of planting single reinforcement is about 1-2 yuan, which is more economical than other anchor bar construction methods.