1. Brief introduction of vitrified brick materials:
Vitrified brick originated in Italy and Spain, and was introduced to China in 1980s. Since 1993, the output of vitrified bricks in China has been ranked first in the world. Vitrified brick has noble tone, elegant texture, smooth surface, easy cleaning and maintenance, wear and corrosion resistance, stable performance, high strength, low water absorption, good decorative effect, luxurious atmosphere and wide application.
2. The vitrified brick falls off:
The hollowing and falling off of vitrified brick wall mainly refers to the problem of overall hollowing and falling off after being stuck with cement mortar or ordinary tile glue for 2-3 months. In general, the bottom of a brick is clean.
3. The bonding mechanism of vitrified brick;
Cement is a kind of hydraulic cementing material, and its adhesion depends on the penetration of cement slurry into the pores of the bonding matrix, gradually forming needle-like crystals and generating friction, thus achieving mechanical nailing adhesion. Vitrified brick is dense, and its water absorption is only 1‰, so it is difficult for traditional cement mortar and common tile binder to bond effectively and firmly.
4. The factors of empty drum falling off:
With the continuous development of the decoration industry, the problem of hollowing and falling off of tiles after paving in the decoration process accounts for a considerable proportion of customer complaints. The reasons for hollowing and falling off are very complicated. To sum up, there are several problems such as tile quality, material selection, climate and environmental factors, construction technology and so on.
1. Characteristics of vitrified brick:
Vitrified brick has dense texture, few pores on the surface, smooth back, low water absorption and residual release agent on the back. Because there are almost no micropores or pits to "lock" cement mortar, it is difficult for ordinary cement mortar to penetrate and adhere, forming an effective and firm mortar locking mechanism. Even stress changes (internal stress and shear force) caused by heating or structural deformation can lead to bonding failure.
2. Internal and external stress:
The main sources of material deformation are wet expansion and dry contraction caused by humidity change, thermal expansion and cold contraction caused by temperature change, shrinkage of base material with age development, shrinkage of concrete and cement mortar caused by seasonal temperature difference change, vibration of partition wall, flue pipe and secondary structure during construction, and too small joint between brick and non-special joint filling material. , will cause the deformation of ceramic tile, adhesive layer and base material, and will produce great internal stress on wall and floor tiles. The deformation of adhesive layer is inconsistent with that of ceramic tile and base material. Due to the inconsistency of the performance, initial state and environment of various materials, the deformation of materials is bound to be inconsistent. This inconsistency will lead to the interaction between them. When the internal stress is greater than the resistance of mortar itself, the bond will be destroyed.
3. Cement bonding mortar:
The material of vitrified brick is very different from that of wall matrix and binder. As a bonding material between two very different materials, the bonding layer should not only have sufficient bonding strength, but also have the ability to eliminate the different expansion and contraction stresses between the vitrified brick and the foundation wall, so as to prevent hollowing, because most of the causes of hollowing are caused by unsynchronized stresses. If the bonding strength of the mortar layer is strong enough and it has good flexibility, it will become a deformation transition zone between the ceramic tile and the base. By absorbing energy through deformation, the internal force generated is small, thus avoiding damage.
Direct use of ordinary cement mortar binder, cement is the only binder that plays a bonding role, the bonding strength is not very high, and the deformation performance is not good, so the traditional bonding materials and methods are prone to quality problems such as hollowing, falling off and arching of tiles under various actions. Moreover, this bonding method requires the thickness of the bonding layer to be 10 ~ 25mm, so it is extremely expensive in terms of materials and man-hours.
The internal force of ceramic tile adhesive under various deformations is quantitatively analyzed, and the method to solve the problem of ceramic tile adhesion is explored. The analysis shows that reducing the elastic modulus of mortar, that is, increasing the flexibility of mortar, can reduce the internal force of bonding mortar layer, thus improving the damage resistance of bonding mortar.
5. Water absorption and expansion rate:
1. Water absorption and expansion rate of materials:
According to the deformation coefficient table of materials under the action of humidity, stoneware tiles and ceramic tiles are sensitive to water and may have obvious expansion reaction. So these tiles are used in places that are often flooded, such as bathrooms, and the deformation of tiles may be much larger than that of the base material.
List of water absorption and expansion rate of decorative materials of various textures
2. The linear expansion coefficient of materials:
As can be seen from the following table, the deformation coefficients of various materials under the action of temperature are inconsistent. The linear expansion coefficient of mortar is about twice that of concrete and four times that of ceramic tile. When subjected to the same temperature change, the deformation of adhesive layer is much greater than that of ceramic tile and concrete. When the ambient temperature decreases, the shrinkage of the bonding layer is much greater than that of the base layer and tiles, and the shrinkage of the bonding layer is limited, which will produce tensile stress in the mortar layer. The tensile capacity of mortar layer is limited. When the resistance is less than the tensile stress, the adhesive layer will crack.
The base material shrinks and deforms. With the development of age, foundation concrete will produce many kinds of shrinkage, such as autogenous shrinkage, drying shrinkage, carbonation shrinkage and creep shrinkage. The shrinkage of concrete mainly occurs in the early stage, so many countries, such as Germany, have regulations on this, and decorative projects such as tiling must be carried out after the main project is completed for half a year or even longer. In fact, the drying of the base surface takes 1 ~ 3 years to complete, so the peeling of tiles often occurs at this time. In addition, the mortar layer itself will also produce drying shrinkage. The shrinkage of ordinary cement mortar can reach 2 ~ 3 times that of concrete. Under certain conditions, carbonation shrinkage and creep shrinkage may occur in concrete or mortar, and considerable shrinkage value may be generated. The shrinkage of mortar is greatly limited at the interface with ceramic tile.
3. Elastic modulus of materials:
When the adhesive elastic modulus is low, that is, the flexibility is good, the thickness of the adhesive layer can be reduced. For the thickness of the adhesive layer, the common bonding mortar is 10mm, the flexible adhesive layer is 5mm, and the shrinkage rate of the substrate is 0.25mm/m. The shear stress distribution of the adhesive is shown in the following figure. It can be seen that the use of flexible adhesive will greatly reduce the shear stress in the adhesive layer. On the premise of ensuring a certain bond strength, reducing the elastic modulus of the bond layer is an effective method to reduce the internal stress of the bond layer and ensure the firm bond. When the elastic modulus is less than 1000MPa and the bonding is greater than 1.5 MPa, the bonding layer can have a large safety reserve, which can ensure that the bonding layer will not be destroyed when the environment changes.
6. Common adhesive configurations:
1. Bonding strength and flexibility are important indexes for preparing bonding mortar. Bond strength can be measured by bond shear strength and bond tensile strength. It is generally believed that the bond strength of two materials is equal to the sum of mechanical bond strength and special bond strength. Mechanical bond strength is the bond strength produced by wedging, which has weak external force resistance, mainly shear stress resistance and tensile stress. The special binding force is chemical force, that is, molecular attraction between two substances. Special adhesion can resist tensile force, shear force and peeling force.
2. The ratio of lime to sand is an important index related to the technical economy of mortar. Different lime-sand ratio will have a great influence on the properties of bonding mortar, especially its mechanical properties. To prepare bonding mortar, we must first ensure its good workability and workability, which is directly related to the content of cement slurry. The demand of cement slurry depends on the porosity between sand grains and the total surface area. Smaller porosity and smaller total surface area can reduce the need for cement slurry. For fine aggregate with large porosity and surface area, if the amount of cement slurry is insufficient, the performance of the mixture is difficult to guarantee. If the dosage of cement is blindly increased at this time, it will not only be uneconomical, but also lead to excessive shrinkage of mortar because it does not contain coarse aggregate, which may lead to cracking of mortar. Therefore, the ratio of lime to sand is an important index related to the technical economy of mortar. Therefore, this paper has carried out experimental research and selected a more reasonable lime-sand ratio.
3. Lime sand mixture ratio and strength inspection data sheet:
The main purpose of adding 5% interfacial agent to ordinary mortar is to improve the bonding strength, flexibility and workability of mortar.
4. From the above analysis results, the mortar with the ratio of 1: 2 is obviously higher than that with the ratio of 1: 3. Although the flexural strength, compressive strength and bond strength of the mortar with the ratio of1:0 are higher than those with the ratio of 1: 2, the cement consumption is large and uneconomical. Compared with the mortar with the lime-sand ratio of 1: 3, the bond strength of mortar with the lime-sand ratio of 1: 2 is greatly reduced. Although the flexural compression ratio is slightly higher than that of mortar with the lime-sand ratio of 1: 2, the effect is not obvious. Therefore, considering comprehensively, the lime-sand ratio of 1: 2 is the most suitable.
5. When the mortar without interfacial agent is bonded and sheared, the failure surface is that the tiles fall off, and there is almost no mortar stuck on the fallen tiles, leaving only some cement stains. However, when the bonding of mortar containing interfacial agent occurs shear failure, mortar is stuck on both sides of the tile, indicating that the bonding layer first undergoes shear failure, and then the bonding surface is destroyed.
6. The picture below is a photo of the test block with tensile bond failure. Mortar without interfacial agent causes tile surface to fall off when it is damaged, and polymer mortar causes mortar on half of the damaged surface of tile. Obviously, the adhesion between polymer mortar and ceramic tile surface is greatly enhanced.
7. The following figure shows the SEM scanning photos of benchmark mortar and polymer mortar at the age of 14 days respectively. There are many needle-like and flocculent hydration products in the benchmark mortar, and there are many gaps. In polymer mortar, many polymer particles adhere to and accumulate around the hydration products of cement. These polymer particles are connected with each other, or covered on the hydration products in the form of polymer films, which play a bridging role, and the polymer films constitute a part of the hole wall, thus sealing the gaps of the mortar and improving the bonding strength of the mortar as a whole. Polymer particles and polymer films have low elastic modulus, but good flexibility, so polymer mortar reduces the compressive strength of mortar, but improves the flexibility of mortar. The polymer particles and polymer films dispersed in the slurry make the propagation of cracks in the hardened slurry more complicated and the toughness is improved.
8. The following picture shows the SEM scanning photo of the interface between polymer mortar and ceramic tile. On the interface, the polymer film between the polymer mortar and the ceramic tile interface can be clearly seen. It is this polymer that provides the bonding strength between mortar and ceramic tile. However, because the surface of ceramic tile is highly smooth, the benchmark mortar can not form a mechanical locking effect, and there is no polymer film to provide special bonding force, so the bonding strength is very low.
9. After adding 0.5% cement alkali inhibitor EL 1290 to polymer interface mortar, the content of ettringite in hydration products has been significantly improved, which shows that the addition of cement alkali inhibitor EL 1290 is beneficial to the formation of ettringite. Ca(OH)2 generated by hydration decreases and ettringite increases. It is found that the alkali-inhibiting additive of cement reacts chemically with hydrated calcium hydroxide to form a gel substance. Consume calcium ions and reduce the content of calcium hydroxide. But this paper mainly describes the safe bonding of vitrified bricks, and the alkali inhibition of cement is not described and discussed here.
7. Safe bonding of vitrified brick:
1. At present, no special vitrified brick adhesive product with high flexibility has been found. The sampling test of vitrified brick binder in the market shows that the tensile strength of the material can rarely reach more than 0.5MPa, and the common problem is that the flexibility of mortar is relatively low. Although the bonding force of mortar is stronger than that of cement mortar, it is still not enough to stick vitrified bricks for a long time. For the bonding strength of high-density vitrified brick, considering the safety of resisting expansion and contraction stress, the tensile strength of bonding material should be above 65438±0.0 MPa.
2.2 construction. AB glue or steel hanger glue can keep the bonding ability for a long time, and can better solve the problem of thermal expansion and cold contraction. But the price is very expensive, and the whole tile is very expensive, so five-point bonding is often used for bonding. Because it is point bonding, there is a big gap between the tile and the wall, which is easy to become a place where cockroaches, ants and other filth are hiding, and the tile is easy to be destroyed by external forces. Because of the paste, water vapor is easy to enter, the smell is easy to transpiration in summer, and the bathroom smells heavy. Moreover, because AB glue is a chemical oily component, it contains volatiles such as formaldehyde, which is not environmentally friendly. Because it is a chemical product, it is easy to cause aging and other problems, and there is still a problem of falling off in a certain period of time.
3. The quality of ceramic tile adhesives on the market is mixed, and the products are difficult to distinguish. At present, vitrified brick binder is generally not flexible, so it can't overcome the stress of expansion and contraction, and can't achieve the practical effect of solving the problem of hollowing and falling off of vitrified brick. The high-grade vitrified brick binder is expensive, and the cost of general engineering is unbearable. In addition, special adhesive is generally suitable for thin-layer bonding, which requires high flatness and verticality of the base. Therefore, the applicability, flexibility and bonding safety of special adhesives need to be improved.
Ordinary 1:2 cement mortar with 4.5% interfacial agent plays a role in sealing the mortar gap, making the mortar a whole, improving the bond strength, flexibility, shear bond strength and tensile bond strength of the mortar, reducing the internal force of bonding mortar layer and improving the failure resistance of bonding mortar. The linear expansion coefficient of mortar mentioned above is about twice that of concrete and four times that of ceramic tile. When subjected to the same temperature change, the deformation of adhesive layer is much greater than that of ceramic tile and concrete.
Therefore, only adding 5% interfacial agent to ordinary mortar to modify mortar can not achieve safe and firm bonding between mortar layer and base, and can not resist various stresses on the bonding surface between mortar layer and ceramic tile, especially vitrified brick, which has dense texture and almost no micropores or pits on its surface, and can form an effective and firm mortar locking mechanism with cement mortar. Under the constant impact of complex stresses such as thermal expansion, cold shrinkage, vibration and hardening shrinkage, the tensile capacity of mortar layer is limited, and the bonding layer is still in danger of bonding failure.
5. Back gluing can be divided into three types: one-component sand-free mold, one-component sand mold and two-component mixed mold. One-component masonry adhesive is made of alkali-resistant ultrafine nanoparticle emulsion and other additives. Two-component adhesive for back coating of masonry, component A consists of imported polymer emulsion and additives, and component B consists of inorganic filler and additives. The back coating of masonry is specially used for the back treatment of hard masonry with low water absorption, such as vitrified brick and stone, which can improve the bonding strength between ceramic tile and bonding material and effectively solve the common problems of hollowing and falling off in wet bonding between ceramic tile and stone.
6. Back gluing is a kind of water-resistant material that combines rigidity with flexibility. It is evenly coated on the back of vitrified brick with brush, roller and spray gun to form a uniform rivet shape as an intermediate bonding layer to adapt to temperature changes and resist expansion and contraction stress. A large number of practical engineering applications have proved that it is the safest, economical, easy to control and practical way to paste vitrified bricks with self-made 1:2 cement mortar containing 5% interfacial agent. Cover the back of the hidden shield with super-viscous adhesive, and the back of the brick has texture at the interface. Its super-strong adhesion and double-sided affinity with bonding materials make the bonding more firm. Latent shielding backing adhesive has excellent processability, cohesiveness, flexibility, weather resistance, high temperature resistance, wet heat resistance and water resistance. It can not only be simply replaced to improve the construction efficiency, but also improve the pasting quality and simplify transportation and handling. The glue on the back of the submarine shield can't be knocked off once, and it's no longer necessary to shut out the vitrified brick.
Eight. Basic requirements and treatment:
Concrete beams and slab columns shall be thoroughly and firmly painted, plastered without hollowing, the base surface shall be clean without dust and oil pollution, the wall surface shall be watered and wetted in advance, the grooves, holes, chisels, buries and cleaning shall be completed, the surface of waterproof materials shall meet the requirements of tiling, and steel wire mesh shall be attached to light walls and smoke pipes.
1. Alkali-resistant polymer waterproof slurry is suitable for waterproof parts. After the surface of this waterproof material is coated with interfacial agent, tiles can be pasted directly. The alkali-resistant waterproof slurry can control the occurrence of alkali flooding after ceramic tiles are pasted, and ensure the bonding strength and waterproof performance.
2. Non-load-bearing lightweight wall tiles, such as lightweight partition walls, air ducts, keel cement slabs, etc. It is easy to cause settlement, deformation and displacement due to the heavy weight of ceramic tiles, and it is easy to cause hollowing and falling off due to unfavorable factors such as large vibration induction and rapid water loss. In this part, in order to reduce the possibility of hollow tiles, a layer of steel wire mesh is usually hung before tiling, because the steel wire mesh is a horizontal and vertical structure, which can disperse and uniformly stress.
3. In addition to the brushed base, other base walls should be coated with emulsion interface agent before tiling, so as to enhance the cohesive force and reduce the moisture of the binder being absorbed by the base too quickly.
4. Avoid heating the floor tiles in a short time after paving. If the ceramic tile is heated in the process of paving or in a short time after completion, the water in the cement will evaporate rapidly, and the water vapor and thermal expansion and contraction will make the ceramic tile empty and form an empty drum.
9. The main links in the construction:
1. After the back of vitrified brick is coated with latent shielding adhesive, it shall be pasted with 1:2 cement mortar mixed with 5% latent shielding interface agent. Before pasting, all pasting bases except the wall surface shall be coated with latent shielding interface agent.
2. Lightweight wall plastering of non-load-bearing structures such as lightweight partition walls, air ducts and keel cement slabs shall be performed after hanging steel wire mesh plastering and brushing interface agent.
3. The bottom of the brick should be fixed with wood square to prevent the tiles from falling off, and the whole space should be laid layer by layer to avoid the tiles falling off due to the short setting time of cement mortar.
4. The mixing of polymer cement mortar should be fully uniform to prevent it from being too thin. The thickness of bonding layer is generally 10 ~ 20 ㎜, and the working procedure should be arranged to minimize the knocking vibration after pasting.
Joint materials with Tenuto vitrified brick:
After the vitrified brick is pasted for 24 hours, the jointing material should not be directly jointing with white cement, but a flexible special jointing agent with alkali inhibition, hydrophobicity, compactness and mildew resistance should be used. It is recommended to use alkali-resistant advanced tile caulking agent to invent patented products. The flexibility and hydrophobic property of special caulking material can effectively prevent the tiles from hollowing out and falling off.
XI。 Inspection, acceptance and handling:
1. Metal objects hit the four corners and the core of the tile. If each tile has more than two points, it means that the tiles are not pasted correctly. There is a difference between the drumming of smoke pipes or lightweight partition boards and the drumming of structural wall tiles.
2. Generally speaking, regarding the hollowing rate of tiles, the hollowing rate of tiles should be controlled within 3%, and the hollowing rate of wall tiles should be controlled within 5%, that is, the hollowing area of a tile should not exceed 5% of the tile area. If the empty drum area exceeds the regulations, it needs to be reworked and repaired.
3. If the ceramic tile is hollowed out, the ceramic tile manufacturer and the constructor may pass the buck to each other. Among them, improper construction in tile paving stage is the most likely to lead to hollow bricks, which need special attention.
4. In order to avoid tile hollowing, first of all, the wall and ground base of tile paving must be cleaned. Be sure to remove all kinds of dirt on the wall, and wet the base with water one day in advance, and control the humidity at 30 ~ 70%. 2 ~ 5 mm expansion joints should be reserved when sticking bricks. If there are not enough expansion joints, adjacent tiles may be squeezed under the action of thermal shock expansion or moisture expansion, resulting in hollowing and falling off.
5. Wall construction, should be layered paste from bottom to top. In the process of layered pasting, the layered rotary pasting method should be adopted, that is, the horizontal construction of each layer of tiles: wall tile → Yin and Yang angle → wall tile → Yin and Yang angle → wall tile, etc. This kind of paste can make the angle of yin and yang tight and firm, which is much better than sticking the angle of yin and yang after all the wall tiles are pasted.
6. The surface of lightweight masonry such as aerated block should be cleaned, and the plastering surface should be watered and wet one day and night in advance. Except for the bonding base that needs to be brushed in advance, the emulsion-type latent shield interface agent should be brushed before pasting.
7. Adding EL 1290 cement alkali inhibitor into the modified ordinary 1:2 cement mortar mixed with 5% latent shield interface agent can effectively prevent tile from alkali flooding and reduce the probability of tile hollowing.
Twelve. List of recommended materials:
Thirteen. Maintenance knowledge of vitrified brick:
1. For stains such as tea stains, fruit stains, coffee sauce vinegar, shoe prints, etc., use sodium hypochlorite diluent (bleach). Soak for 20-30 minutes and then wipe with a cloth.
2. Use sodium hypochlorite thinner (bleach) for the mildew spots formed by the mildew of ink and antifouling wax. Apply bleach to the stain and soak it for a few minutes to wipe it off.
3. Wipe cement, scale, water rust and rust spots with EL 1300 cleaner for several times.
4. Use alkaline cleaner or organic solvent (acetone, triethylene) to clean paint, oil stain mark and surface antifouling wax layer, and remove paint and grease remover.
5. Rubber hammer marks are first soaked in 40% sodium hydroxide solution for 24 hours and then wiped off, and then soaked in 50% hydrochloric acid solution for 30 minutes and then wiped off with a cloth.
6. Ice cream alkaline cleaner.
7.EL 1300 cleaning agent is used for lime scale.