Select glue solution to add fine aggregate and cement on site, and mix well before use. The selected materials must meet the following requirements:

1) Cement shall use qualified products with field grade of 32.5.

2) Fine aggregate should be medium sand with qualified quality, and the silt content should not be too large.

3) The variety, model, package number and production date of the glue used shall be inspected according to JC∕T907 Concrete Interface Treatment Agent. Re-check the shear strength, tensile bond strength and other necessary performance indicators.

4) Tap water can be used as the interface agent.

In addition, glue is a special material, and a second-round exam report and factory certificate should also be provided. Glue is also a special material for preservation and use, and the supplier should also provide the instruction manual of glue to guide the field use. Cement, sand and other basic materials should meet the design requirements and the provisions of the current national products, and should have the factory certificate.

Construction machinery and tools:

1) Construction equipment for shotcrete at the interface between concrete base and plastering layer includes: bench scale, shotcrete machine with air compressor, electric mixer and sprayer.

2) When selecting the above equipment, the following requirements shall be met:

(1) platform scales and air compressor pressure gauges must be calibrated according to relevant national regulations and within the validity period.

⑵ The weighing accuracy of the platform scale should be 50g.

(3) The pressure gauge should match the air compressor.

Process flow:

Basic treatment → basic acceptance → wall watering → slurry preparation → on-site spraying → maintenance.

1) substrate treatment: the substrate surface should be treated before shotcrete construction.

(1) Clean up the oil stain and demoulding machine attached to the concrete base, and remove the old formwork and other sundries on the surface of the structure, so that the sprayed concrete layer can be effectively and firmly attached to the concrete base.

(2) The expanded formwork on the concrete surface shall be chiseled and cleaned in advance, and the repair and installation of trunking shall be completed before shotcreting.

(3) In order to ensure the effective and firm bonding with the concrete base surface, the holes on the base surface should be repaired with the same cement mortar as sprayed concrete, and the concrete base surface should be fully wetted with water.

(4) For some staggered concrete structures and masonry structures, the staggered positions should be leveled and cleaned.

2) After the grass-roots treatment, please ask Party A and the supervisor for acceptance, and the next working procedure can be carried out only after passing the acceptance.

3) Spray the wall to be sprayed with clear water, and rinse the wet wall. The wall should be watered and wetted one day in advance.

4) Slurry preparation, which is the key to the quality of shotcrete engineering.

(1) The mixing slurry shall be prepared in strict accordance with the instructions for the use of glue solution, and shall be determined after trial mixing, taking into account the requirements of raw material performance, consistency and cohesive force, construction technical level, construction conditions and other factors. The dosage of raw materials must be measured during preparation, and the allowable deviation should meet the requirements in the following table. All materials are measured by mass method.

Allowable error of weighing raw materials per plate

⑵ Forced mixer should be used to mix the slurry, and the consistency meets the requirements. The stirring time should be 2.5~3min.

(3) The mixed slurry should be put into the air compressor (shotcrete machine) in time and used up within 3h.

5) shotcrete construction:

(1) Before spraying concrete, the base should be clean and free of oil pollution, and the holes in the wall should be repaired and accepted as above.

⑵ Before spraying, the base should be properly watered and moistened according to the actual situation to ensure the effective and firm bonding of the interface agent.

(3) During spraying construction, the spraying pressure should be 0.4 MPa ~ 1.0 MPa, the distance between the spray gun and the structural surface should be 0.6 m ~ 1.5 m, the included angle between the spray gun and the wall should be greater than 30, and the spraying construction should move at a constant speed from top to bottom or from right to left.