In recent years, with the development of the social economy and the improvement of urban appearance, stone curtain wall has been favored by the majority of owners and architects in the exterior decoration of buildings, and has occupied a considerable proportion of the existing buildings. Moreover, the height and volume of the stone curtain walls are getting higher and higher; More and more stone materials are used, from the original single granite to marble, limestone, sandstone, and other varieties; The modeling is more and more complex, the requirements for installation and construction technology are more and more strict, and the requirements for safety are also higher and higher.
However, the domestic stone curtain wall material market is in chaos, the construction unit lacks technical specifications for production technology, and the technical quality of construction personnel is low, all of which bring great potential safety hazards to the project. Due to various reasons, the selection of stone slabs, dry hanging glue, dry hanging parts, and the fabrication and installation of pre (post) embedded parts are most easily ignored. A brief analysis is made of how to select these four materials.
1、 Stone slab
The stone curtain wall, as the outer enclosure structure, does not bear the load of the main structure, but it is located on the outer surface of the building. In addition to bearing its own weight, it also bears the impact of wind load, earthquake, and temperature changes. Therefore, the stone must be safe and reliable. The performance and quality requirements for stone materials include compressive strength, flexural strength, flexural strength, hardness, abrasion resistance, frost resistance, fire resistance, processability, etc.
The stone used for the stone curtain walls is naturally formed. The natural stone is mined from the mountain. Its important performance depends on the mineral composition and structure. However, each sample has a difference in the above series of properties tested by sampling, which is not as different as that of industrial products. Due to the different sampling surfaces, the measured properties will not be completely consistent. Based on the above situation, when the architect determines the type of stone, he must be careful in the use of stone slabs, and should do a good job in the following aspects:
1. Basic material property test: its compressive strength, flexural strength, flexural strength, hardness, abrasion resistance, frost resistance, fire resistance, processability, etc. must meet the specification and design requirements. At the same time, each batch of stone slabs used for the curtain wall shall be subject to a flexural strength test. Freezing and thawing tests are also required for areas where negative temperatures may occur. It can be used only when all performance indicators meet the design and specification requirements.
2. Control the processing accuracy of stone to avoid secondary cutting at the construction site. Affected by the installation process, the commonly used stone dry-hanging process requires drilling or grooving on the cross-section of the stone slab. Therefore, the thickness of the stone is limited by the installation process, and structural thickness must be guaranteed. Therefore, special attention should be paid to the thickness of the stone slab during the process of acceptance of the stone slab. The allowable deviation is+2mm, and no negative difference is allowed. It should be checked piece by piece.
3. Damage shall be avoided during mining, transportation, cutting, and installation. Once the formed stone plates collide, the damage, especially the internal injury, is difficult to be detected, but it will develop over time, and in serious cases, it will break, bringing potential safety hazards. The processing, transportation, and installation of stone materials shall be strictly controlled.
4. Protect the stone surface to ensure the dryness of the stone interior and that the natural property of the stone remains unchanged.
5. The area of a single stone shall not be too large, and the Technical Code for Metal and Stone Curtain Wall Engineering shall not exceed 1.5 square meters.
6. Stacking of stone:
① Stack in the specified site according to the specifications of the plates;
② It is strictly prohibited to mix with corrosive materials. Avoid contact with acid and alkali substances;
③ The product processing sequence number shall be marked, and attention shall be paid not to collision, pollution, etc. Use long permeable materials to pad 100mm at the bottom of the plate and ensure its stability.
2、 Stone dry hanging adhesive
The load borne by the stone curtain wall panel is transferred to the pendant by the glue between the stone and the pendant and then transferred to the supporting structure by the pendant. Therefore, the dry hanging glue of the stone curtain wall must be structural glue. At the same time, the dry hanging glue must have good adhesion with the stone and the pendant (the material of the pendant can be stainless steel or aluminum alloy). The adhesive layer itself must have appropriate strength, good toughness, and elasticity.
On the basis of the correct selection of stone dry hanging adhesive, compatibility and adhesion tests of dry hanging adhesive shall also be conducted, and it can be used in the project only after passing the test. It is also very important to use dry hanging adhesive reasonably during construction, and the following points should be noted:
1. The stone hanging slot, the preparation and application of dry hanging glue, and the fixation of dry hanging parts shall be directly carried out in the processing workshop; The slotting of stone must be machined, and the slotting process control and processing inspection shall be strengthened to avoid damaging the stone.
2. The pasting surface shall be dry and dry (the humidity shall not be higher than 15%), free of dust, clean, rough, and oil stain.
3. The physical and mechanical properties of the dry hanging adhesive are directly related to the adhesive thickness (generally 1 mm~2 mm). The processing of dry hanging parts and dry hanging slots should be strict to ensure processing size and accuracy. The matching of dry hanging parts and dry hanging slots should be strict to ensure the thickness and depth of dry hanging adhesive.
4. As the strength of the stone dry hanging adhesive is related to the curing time and temperature, it is necessary to ensure that there is enough curing time and that it cannot be moved or loaded at the initial stage of curing.