1. Collaboration before construction
The main items of the approved node design: are the size of the material, the sealant, and the drainage treatment; the compatibility and adhesion of the approved sealant with the auxiliary materials and the substrate to be adhered.
2. Preparation before construction
1) Technical preparation
a. Preparation of construction schedule
According to the requirements of the construction schedule, the specified construction period, and the coordination and cooperation with other processes, determine the construction method of this process and the number of construction personnel required and prepare the construction schedule plan for this process.
b. Inspection and cleaning of the bonded base layer
Check whether the surface condition of the bonded base, the degree of dryness, and the size of the joints are consistent with the drawings, and whether they meet the construction requirements. The grassroots that do not meet the requirements shall be dealt with.
2) Material preparation
a. Selection of primer
In addition to preparing the sealing material according to the design requirements, it must be used in accordance with the primer provided by the sealant manufacturer to ensure that the sealant has good adhesion to the base layer.
Before application of the primer, if necessary, the adhesion test can be carried out according to the following simple method:
- Take the actual bonding base layer as the bonding body;
- Paste cellophane tape on one-third of the longitudinal part of the surface of the sealant to be bonded;
- Apply primer on the remaining two-thirds of the longitudinal direction;
- On the cellophane tape and primer, stick a 2mm thick strip of sealant;
- Place on site until cured; check adhesion
b. Selection of auxiliary materials
The auxiliary materials used in the construction of unshaped sealing materials include backing materials, isolation strips, anti-fouling strips, etc.
3. Inspection before construction
Confirm the construction conditions, the size of the joints, whether there are defects, etc.
4. Clean and dry the substrate to be adhered
Confirm whether the surface of the substrate to be adhered is dry. In order to prevent adhesion failure, the surface oil stains, dirt, etc. must be cleaned with a two-cloth wipe method with a solvent. Commonly used solvents are toluene, xylene, and methyl ethyl ketone. If it is necessary to dissolve the painted surface, use n-hexane.
5. Packing of gasket material (backing material, double-sided tape, etc.): Fix the size of the sealant. If the filling depth is insufficient, the bottom of the gasket must be posted to prevent three-sided bonding.
6. Pasting of the anti-fouling strip: prevent the anti-fouling strip from falling into the surface to be glued.
7. Coating of primer: The coating thickness of primer is moderate and uniform without leaving any residue; ensure the drying time required by the primer, and fill the sealant within the specified time.
8. For two-component sealants, the composition ratio must be tested. The specific method can be judged by comparing the curing time (the breaking time described in many materials) with the instructions of the supplier’s materials.
9. Apply sealant: Be sure to fill the gaps with the sealant. Before trimming the joints, use external force to compact the sealant into the joints to ensure that the sealant is in full contact with the surface to be bonded. During the construction of the structural adhesive, the same batch of adhesive materials can be bonded at the same time, and samples can be prepared for bonding inspection.
10. Modification: After the sealant is applied, the joints should be trimmed immediately. When trimming, the trimming pressure must be evenly completed in one direction; then quickly remove the anti-fouling strip to prevent the anti-fouling strip from being stuck on the sealant or substrate.
11. Sealant maintenance: For weather-resistant sealants, avoid the cross-construction period when the construction site is dusty; for the maintenance of structural sealants, especially for single-component structural sealants, there should be a place that can ensure the ambient temperature and humidity. It is especially important in colder areas in winter.
12. Comprehensive inspection: The focus of the inspection is the adhesion of the sealant to the substrate to be adhered. The method can carry out unit sampling inspection, and can also carry out adhesion inspection on samples prepared for adhesion inspection.
The above general construction procedures are applicable to weather-resistant sealants and structural sealants used in building curtain walls. More importantly, a quality control system is established in accordance with the procedures to effectively complete the expected construction quality. During the actual construction, the risk analysis of environmental factors after the application of a sealant on site, the training of high-quality construction personnel, and the final technical support of the material supplier are also very important.