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Home / News / Application and construction of self-leveling gypsum base

Application and construction of self-leveling gypsum base

Views:10     Author:Site Editor     Publish Time: 2021-01-20      Origin:Site

01PART gypsum base self-leveling overview

Gypsum-based self-leveling mortar is a kind of dry powder mortar specially used for ground leveling, which is prepared by carefully configuring and mixing gypsum as the main cementing material, special aggregates and various construction chemical additives in the factory. The mortar can be directly added with water and stirred (mechanical/manually) on the construction site into a self-flowing liquid, which can be automatically leveled, and can be used for leveling the ground of indoor buildings, such as filling uneven ground, fine cavities and cracks. It can be widely used in the leveling treatment of indoor carpets, PVC floors, wooden floors, floor tiles, etc. It is especially suitable for floor heating systems (water heating/electric heating).

Application and construction of self-leveling gypsum base

Development of domestic gypsum-based self-leveling

In the late 1980s, production was very scarce.

The research on gypsum-based self-leveling mortar in my country started relatively late, about in the late 1980s and early 1990s.

In 1986, the research and development stage.

In 1986, the gypsum-based self-leveling material with fluorine gypsum waste residue as the cementing material was successfully developed. However, due to the poor water resistance of gypsum and its neutral or acidic nature, it has the risk of rusting iron parts and is rarely used in production.

From 1986 to 2007, the market began to gradually apply.

The application cost of gypsum-based self-leveling is higher than that of cement mortar, and its promotion and application are hindered and the development is slow. There is still a certain gap with foreign countries in application technology and construction equipment. With the gradual maturity of domestic gypsum-based self-leveling products, in 2007, my country formulated and implemented the corresponding product standard JC/T1023-2007 "Gypsum-based self-leveling mortar".

2019, a blowout development.

With the continuous improvement of product quality and production technology, the country has become a state of blowout development, and market demand continues to rise. Under the guidance of relevant technologies, major small and medium-sized enterprises have begun to start production and construction.

The advantages of gypsum-based self-leveling mortar

1. The gypsum-based self-leveling construction ground has accurate dimensions, high levelness, no hollowing, no cracking; easy and convenient operation, high efficiency; and pumping construction can be used, and the daily paved floor can reach 800~1000㎡ , The construction speed is 5-10 times faster than traditional ground materials.

2. Used as a "floor heating" leveling overlay (compared with other heating methods, floor heating has an energy-saving range of about 20%. If a zoned temperature control device is used, the energy-saving range can be as high as 40%). It will not be like a cement mortar layer. Thermal expansion and cold contraction produce cracking, bulging and other phenomena.

3. The gypsum-based self-leveling hardened floor has a certain degree of flexibility, warm and comfortable feet; and has a certain sound insulation effect.

4. Good heat preservation performance is conducive to building energy saving. When used with floor heating, the energy saving range is about 20% compared with other heating methods. If the zone temperature control device is adopted, the energy saving range can be as high as 40%.

5. When gypsum-based self-leveling and cement mortar are used in the leveling layer of the building floor, the final cost of the two materials is similar. If gypsum self-leveling is used to replace cement mortar, the reduction in cement consumption will be a small proportion of the entire cement output, less than one percent; it will basically not affect the interests of cement manufacturers. Therefore, the promotion and application of self-leveling gypsum in my country's building materials market has low resistance and great prospects.

Gypsum-based self-leveling mortar and highly flexible bonding mortar form a floor heating system, which can completely solve the current domestic floor heating system of cement mortar cracking, low thermal conductivity, and easy damage to hot water pipes. It uses the entire ground as a heat dissipation surface to evenly radiate heat to the room. Compared with other heating methods (air conditioners, radiators, fireplaces, etc.), it has the characteristics of comfortable thermal feeling, heat balance and stability, energy saving, and maintenance-free. It is to create a comfortable living environment. The best heating method. In addition, as a floor heating system, the porosity of the gypsum material itself can play a role in sound insulation and heat preservation. The gypsum-based self-leveling density is low, which can reduce the weight of the building. It is a green and environmentally friendly energy-saving product.

Analysis on the application prospect of gypsum-based self-leveling market

As a ground leveling layer, self-leveling gypsum has the advantages that other materials cannot match, so it has a broad market prospect. According to data from the National Bureau of Statistics, self-leveling gypsum as a ground leveling layer has advantages that other materials can’t match, so its market prospects are broad. my country's new construction area is nearly 2 billion square meters every year. If 60% of the ground uses self-leveling gypsum (about 10-15 kg per square meter), there will be a market demand of 15-20 million tons per year. Self-leveling gypsum is the only product without large-scale industrial production among all gypsum products in my country's building materials market. Self-leveling gypsum is an important product that replaces cement and reduces carbon emissions in my country. Compared with the "gypsum dry mortar" that the government has issued policies to promote, it also has the social and economic benefits of energy saving and emission reduction.



Types of self-leveling gypsum base

1. α-High strength gypsum-based self-leveling mortar

Types of self-leveling gypsum base

Compared with cement-based self-leveling materials, gypsum-based self-leveling materials have lower strength and poor water resistance, and are mainly used indoors in the form of "bottom self-leveling materials". The use of α-high-strength gypsum as the base material of the self-leveling material can significantly improve the strength of the material. Natural gypsum is used to make high-strength gypsum with a compressive strength of more than 14MPa in 2 hours. At present, industrial by-product gypsum uses succinic acid, maleic anhydride and sodium succinate to prepare α-high-strength gypsum increasingly mature. However, the use of high-strength gypsum as a self-leveling material is now generally mature, mainly due to the superiority of high-strength gypsum The mechanical properties. Using high-strength gypsum with 2h compressive strength and flexural strength of 35.1MPa and 6MPa respectively as the cementing material, under the action of other polymer chemical additives, a self-leveling gypsum mortar with excellent performance is prepared.


2. Self-leveling mortar for construction gypsum

Self-leveling mortar for construction gypsum


Gypsum has unique thermal insulation properties, sound absorption properties, fire resistance, excellent shaping properties, beautiful decoration, etc., so it is more and more favored by the construction industry. However, the defects of building gypsum self-leveling mortar often limit its application, especially the industrial by-product gypsum affected by impurities, which needs to be mixed with polymer chemical additives to improve the compressive strength and flexural strength of the gypsum self-leveling material. "Odaxing gypsum-based self-leveling polymer special rubber powder" can reduce the mixing water consumption without reducing the fluidity of the gypsum slurry, and improve the structural compactness and mechanical properties of the hardened gypsum body. With the rapid development of special polymer chemical additives for gypsum-based self-leveling, the promotion and application of building gypsum self-leveling materials have been promoted.


3.Ⅱ Anhydrous gypsum self-leveling mortar

Ⅱ Anhydrous gypsum self-leveling mortar


Type Ⅱ anhydrous anhydrite is different from ordinary building gypsum. In the absence of excitation, its hydration rate is very slow, which cannot meet the requirements of development and utilization. When applying type II anhydrous anhydrite, we must first consider the excitation of type II anhydrous anhydrite and the durability of type II anhydrite hardened body. The two issues are organically unified at the same time. The low early hydration rate of type Ⅱ anhydrous anhydrite cement is the main reason for its poor durability, and the use of high-efficiency composite catalysts and the improvement of the fineness of type Ⅱ anhydrous anhydrite is to improve type Ⅱ anhydrous high hard rock sound water An effective method of conversion rate. Type Ⅱ anhydrous anhydrite must be effectively activated in order to increase its hydration speed and degree, especially the early hydration rate. Give full play to its gelling properties to achieve the purpose of development and utilization. The effect of type Ⅱ anhydrous anhydrite hydration and hardening activity activation is greatly related to its particle shape, fineness, particle gradation, calcination, and the type and dosage of the activator. Among them, the type and mixing of the activator Quantity is the most influential factor.



02PART gypsum base self-leveling performance

Table 1 shows the basic performance indexes of the gypsum-based self-leveling mortar configured with α-hemihydrate gypsum (desulfurized gypsum from power plants). *For the convenience of comparison, the technical performance indicators of cement-based self-leveling mortar are also listed at the same time.


gypsum base self-leveling performance


Shrinkage

It can be seen from Table 1 that the performance indicators of these two mortars are very similar. In order to ensure the corresponding fluidity, compared with ordinary mortar, the water requirement of self-leveling mortar is usually much higher. In self-leveling mortar, these excess water will evaporate into the air. If this process happens too fast, it will cause very obvious mortar shrinkage, which will lead to cracks in the mortar. However, this situation will not occur in gypsum-based self-leveling mortar, (Figure 1)

As shown in Figure 1, the shrinkage rate of cement-based self-leveling mortar is much higher than that of gypsum-based self-leveling mortar. By 28 days, the shrinkage rate of cement-based self-leveling mortar is about 1.17mm/m. With the continuation of time, the shrinkage rate of cement-based self-leveling mortar reached about 1.31mm/m in 3 months, but the gypsum-based self-leveling mortar remained at about -0.19mm/m, that is, the self-leveling cement-based self-leveling mortar The high shrinkage rate in the mortar is likely to cause cracks in the self-leveling mortar. Therefore, in the actual construction process, necessary maintenance measures should be taken for the cement-based self-leveling mortar to ensure the quality of the project.


Shrinkage


The strength development of gypsum-based self-leveling mortar has a great relationship with the dryness of the mortar itself. In addition to the crystal water required for the formation of dihydrate gypsum, the remaining excess water in the voids of the mortar will rely on the mortar. The medium pores evaporate into the air to form strength, which means that the strength development is proportional to the drying rate of the gypsum-based self-leveling mortar. Figure 2 is the compression/flexural strength development curve of gypsum-based self-leveling mortar. It can be seen from Figure 2 that the gypsum-based self-leveling mortar not only has high early strength (6h>6N/mm2), but also has a rapid development of late strength, which can be used in 28 days. Achieve above 20 N/mm2.

In order to evaluate the relationship between the development of the internal strength of the gypsum-based self-leveling mortar and the dryness of the mortar itself, the bonding strength of the gypsum-based self-leveling mortar was tested in different drying cycles (1d, 2d, 7d) in the laboratory. , That is, after the gypsum-based self-leveling mortar is dried for 1 day, 2 days and 7 days, tiles are attached to test the corresponding bonding strength. The corresponding results are shown in Figure 3 and Figure 4. Figure 3 shows the bonding strength of gypsum-based self-leveling mortar in different drying cycles (after 1d, 2d and 7d). It can be clearly seen from Figure 3 that with the extension of the drying cycle of gypsum-based self-leveling mortar, the corresponding The bond strength increases rapidly. For example, the bond strength at 28 days is 0.8 N/mm2 (bonding after 1d) to 1.4 N/mm2 (bonding after 7d), and the increase is about 35%.

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In other words, for gypsum-based self-leveling mortar, the extension of the drying time will help the development of the strength of the gypsum-based self-leveling mortar, and under the same conditions, the development of the early bonding strength of cement-based self-leveling mortar It is significantly better than gypsum-based self-leveling mortar (Figure 4)


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In order to simulate the application of gypsum-based self-leveling mortar in the floor heating system, the gypsum-based self-leveling mortar was placed in a thermal environment of 50 ℃ to detect the changes in strength and thermodynamic properties. All test blocks (40×40×160mm) are cured for 7 days under standard curing conditions at 20℃/65% relative air humidity, and then directly placed in a drying oven at 50℃.

The data in Table 2 shows that the gypsum-based self-leveling mortar remains basically stable at 50°C, that is, there is no much change. For example, the shrinkage value and compressive strength of 28 days and 194 days are almost the same. It also proved that the gypsum-based self-leveling mortar is particularly suitable for floor heating systems.

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Water consumption for initial mobility:

Weigh (300±0.1)g sample, measure the estimated amount of added water and pour it into the stirring pot, evenly sprinkle the sample into the water within 30s, stir with a spoon for 1min after wetting, and then stir slowly with a mixer for 2min to obtain Uniform slurry. Place the fluidity test mold horizontally in the center of the test board, and the surface of the test board is smooth and clean without water droplets. Fill the prepared slurry into the test mold, start timing, and lift it vertically upwards by 50-100mm within 2s, and keep it for 10-15s to make the slurry flow freely. After the flow stops, measure the diameters in two vertical directions with a ruler, and take the average of the two diameters to the nearest 1mm. If the flow is within 145±5mm, the flow is the initial flow of the sample. If the fluidity is not within 145±5mm, the amount of water added should be adjusted and retested according to the above steps until the fluidity is within 145±5mm. The ratio of the water volume W1 to the sample volume W0 is the initial fluidity water volume. 30min fluidity loss: the material that meets the initial fluidity will be allowed to stand within 30±0.5min in the agitator, and then stirred slowly at each other for 1min, and the fluidity will be retested according to the initial fluidity water consumption. 30min fluidity loss is initial fluidity (mm) -30min fluidity (mm)


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Tensile bond strength:

Weigh 500±0.1g sample, add water according to the initial fluidity, place the forming frame on the forming surface of the concrete slab, pour the prepared material into the forming frame, smooth it, and leave it for 24±0.5h. Model, 10 components are a group. After demoulding, the test piece is dried in a 40±2℃ electric heating blast drying oven for 48 hours. The dried test piece is polished with 260 sandpaper to remove the scum on the surface, and then the drawing head is glued with a suitable high-strength adhesive Knot on the molding surface of the test piece, continue to place it for 24 hours under standard test conditions, and measure it with a tensile bond strength testing machine. The tensile bond strength MPa = maximum breaking load N/2500mm2.


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Shrinkage:

Spread a thin layer of release agent on the inner surface of the shrinking mold, and fix the shrinking head in the holes on both ends of the test mold so that the shrinking head is exposed to the end surface of the test piece by 8±1mm. Weigh 500±0.1g sample, add water according to the initial fluidity, pour the slurry into the shrink mold without vibration, remove the excess slurry with a metal scraper, make the slurry completely fill the mold and make the surface smooth, three The test piece is a group. The test piece is placed under standard test conditions for 24±0.5h. Remove the mold, number it, and indicate the test direction. Within 30 minutes after removing the mold, measure the length of the test piece in the indicated direction, which is the initial length of the test piece. Use a standard rod to adjust the shrinkage before measurement. The origin of the dial indicator of the meter. After the initial length of the test piece is measured, it is placed in a 40±2 degree electric heating air drying box and dried to a constant weight (the mass change within 24h is less than 0.2g), and the constant weight of the test piece is cooled to room temperature under laboratory conditions. Measure the length of the test piece in the direction of, which is the length after drying, shrinking furnace = (the length of the test piece after drying mm-the length of the test piece 24h after molding is the initial length mm) / (the length of the test piece is 160mm-two shrinkage heads are embedded The sum of the lengths in the slurry, ie 20±2mm). )

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Β-type hemihydrate gypsum prepared by calcining first-grade dihydrate gypsum with a purity of more than 90% or α-type hemihydrate gypsum prepared by autoclave method or hydrothermal synthesis method.

Active admixture: Self-leveling materials can use fly ash, slag powder, etc. as active admixtures. The purpose is to improve the particle size distribution of the material and improve the performance of the hardened material. The slag powder undergoes hydration reaction in an alkaline environment, which can improve the compactness and later strength of the material structure.

Early-strength cementitious materials: In order to ensure the construction time, self-leveling materials have certain requirements for early strength (mainly 24h flexural and compressive strength). Sulphoaluminate cement is used as an early-strength cementing material. Sulphoaluminate cement has a fast hydration speed and high early strength, which can meet the requirements of the early strength of the material.

Alkaline activator: gypsum composite cementitious material has the highest absolute dry strength under medium to alkaline conditions. Quicklime and 32.5 cement can be used to adjust the pH value to provide an alkaline environment for the hydration of the cementitious material. Coagulant: Setting time is an important performance index of self-leveling materials. Too short or too long time is not conducive to construction. The coagulant stimulates the activity of gypsum, accelerates the supersaturated crystallization speed of dihydrate gypsum, shortens the setting time, and keeps the setting and hardening time of the self-leveling material in a reasonable range.

Comparison of self-leveling gypsum and traditional cement mortar floor


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Comparison of self-leveling gypsum and traditional cement mortar floor


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Comparison of self-leveling gypsum and traditional cement mortar floor

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Comparison of self-leveling gypsum and traditional cement mortar floor


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03PART gypsum base self-leveling application

The main features of gypsum-based self-leveling mortar: fast hardening time, light bulk density, adjustable thickness, laying thickness 0.5cm-8cm, no cracking, no hollowing, sound absorption and sound insulation, environmental protection, easy construction.

Scope of application

1. It can be used as a cushion leveling material for indoor tiles, carpets, wood floors, etc.

2. It can be used as a basic leveling material for indoor PVC, PU, etc.

3. It can be used as interior color decorative surface material

4. It can be used as an indoor floor heating overlay for leveling

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The gypsum-based self-retaining mortar floor project is designed according to the material performance, use function, ground structure type, environmental conditions, construction technology and engineering characteristics.

Classification of gypsum-based self-retaining mortar floor:

Gypsum-based self-retaining mortar floors are divided into five types: combined type, isolation type, insulation board type, plumbing type A, and plumbing type B

The combined type is composed of base layer, interface agent, and gypsum-based self-leveling mortar floor.

The isolation type is composed of base layer, isolation membrane, and gypsum-based self-leveling mortar floor.

The insulation board type is composed of base layer, insulation board, isolation membrane, and gypsum-based self-leveling mortar floor.

Plumbing type A and plumbing type B are composed of base layer, insulation board, isolation film or reflective film, plumbing pipe, and gypsum-based self-retaining mortar floor.


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The gypsum-based self-retaining mortar floor project is designed according to the material performance, use function, ground structure type, environmental conditions, construction technology and engineering characteristics.

Classification of gypsum-based self-retaining mortar floor:

Gypsum-based self-retaining mortar floors are divided into five types: combined type, isolation type, insulation board type, plumbing type A, and plumbing type B

The combined type is composed of base layer, interface agent, and gypsum-based self-leveling mortar floor.

The isolation type is composed of base layer, isolation membrane, and gypsum-based self-leveling mortar floor.

The insulation board type is composed of base layer, insulation board, isolation membrane, and gypsum-based self-leveling mortar floor.

Plumbing type A and plumbing type B are composed of base layer, insulation board, isolation film or reflective film, plumbing pipe, and gypsum-based self-retaining mortar floor.


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Combined schematic

1—Interface agent (optional); 2—Gypsum-based self-leveling mortar; 3—Interface agent; 4—base layer

The thickness of the combined gypsum-based self-leveling mortar floor is determined by the load above the floor and the strength of the selected gypsum-based self-leveling mortar. The strength of the gypsum-based self-leveling mortar shall not be lower than the minimum strength level required by the product standard. The thinnest construction thickness is not allowed to be less than 5mm.


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Isolated schematic

1—Elastic tape; 2—Gypsum-based self-leveling mortar; 3—Isolation film; 4—base layer

The thickness of the isolated gypsum-based self-leveling mortar floor is determined by the load above the floor and the strength grade of the selected gypsum-based self-leveling mortar. The grade strength of the gypsum-based self-leveling mortar shall not be lower than the minimum strength requirements of the product standard. The thin area is not allowed to be less than 20mm.


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1—Elastic tape; 2—Gypsum-based self-leveling mortar; 3—Film (isolation film); 4—Insulation board; 5—Base layer

The thickness requirements of the insulation board type floor for non-heating systems: If the flatness of the base layer under the insulation board is not enough, rough leveling should be carried out. The thickness of the rough leveling layer is determined by the flatness of the ground, but the thickness of the rough leveling is the thinnest. Not less than 5mm. During the construction of the insulation board floor, the difference between the minimum thickness of the on-site construction work and the designed standard value should be ≤5mm, and the minimum construction thickness should not be less than 30mm.


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1—Elastic tape; 2—Gypsum-based self-leveling mortar; 3—Film (isolation film); 4—heating reflective film; 5—insulation board; 6—heating tube; 7—base layer

The thickness of the plumbing gypsum-based self-leveling mortar floor on the thermal insulation board should meet the design requirements. Among them, the height of the gypsum-based self-leveling mortar covering the plumbing pipe shall not be less than 20mm.


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1. Construction preparation

1Materials: interface agent, gypsum-based self-leveling mortar

2 Construction tools

(1) Mechanical tools: electric mixers, buckets, buckets, scrubbers, vacuum cleaners, electric cutting machines. 

(2) Testing tools: level, fluidity tester.

(3) Auxiliary equipment: water pipes, wires and cables, bottom coating roller brush, soft brush, measuring cylinder, toothless scraper, gypsum-based self-leveling mortar scraper (fine tooth scraper), defoaming roller, spikes, trowel Knife, trowel, spatula, etc. …

3 Staffing

The number of construction personnel should be determined according to the construction area. Generally, it should include: mechanics (self-leveling mixing, ground grinding, vacuum cleaner, electric cutting machine, etc.), bricklayers (repairing, leveling), power workers (cleaning, handling, painting) Interface agent), management personnel (on-site management, quality control, etc.)


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Gypsum-based self-leveling mortar floor heating system: It is a system that uses indoor ground for heating. The system adopts advanced self-leveling mortar and high-flexible bonding mortar technology, which completely solves the quality problems of cracking, low thermal conductivity, and easy damage to hot water pipes in the domestic floor heating system. It uses the entire ground as heat dissipation Compared with other heating methods (air conditioner, radiator, fireplace, etc.), it has the characteristics of comfortable thermal feeling, stable heat balance, energy saving, and maintenance-free. It is the best heating method for creating a comfortable house.


2. Construction technology

1 closed site

The site should be closed and cross operation is strictly prohibited. During indoor construction, the self-leveling ground will crack due to indoor ventilation, so doors and windows should be closed and the site closed. The construction requires the cleanliness of the grassroots and the environment, without interference from other types of work, and does not allow interruptions or pauses.

2 Basic inspection

Thoroughly check the surface of the base layer without sanding, hollowing, shelling, peeling, looseness, pitted surface, grease, dust, cracks and other defects, and the surface dryness and flatness should meet the requirements. 

3 Grassroots cleaning and treatment;

(1) Use detergent to remove grease, wax and other pollutants on the base layer. If necessary, use a scrubber to clean the ground to remove dust, weak concrete surface, grease, cement paste or putty, and may affect the bond strength Clean up the impurities, so that the base layer is dense, and the surface is free of loose and debris. 

(2) The floating soil on the surface of the base layer must be cleaned up with a vacuum cleaner.

(3) Use special repair mortar to repair the honeycombs and holes of the base layer. The large-area empty drum should be completely removed and re-construction; the local empty drum should be treated by grouting or other methods. Special materials should be used to infuse, level and seal the cracks in the base.

(4) The base must be firm and compact, the compressive strength of concrete should not be less than 20Mpa, and the compressive strength of cement mortar should not be less than 15Mpa, otherwise, reinforcement treatment or re-construction should be adopted. For the ground with waterproof and moisture-proof requirements, the construction of the waterproof and moisture-proof layer should be completed in advance below the base layer. 

4 Elevation control.

Use a level to measure the elevation and thickness of the self-leveling mortar to be constructed, and mark the elevation of the base layer with elevation screws. Generally, the construction thickness of self-leveling mortar is not less than 4mm.



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5 Brush the interface agent;

(1) The purpose of applying the interface agent is to seal the base layer to prevent the self-leveling mortar from losing water prematurely; to enhance the bonding strength between the ground base layer and the self-leveling mortar layer; to prevent the generation of bubbles; to improve the fluidity of the self-leveling mortar. 

(2) According to the requirements of the interface agent instructions, use a roller to paint the interface agent on the ground. The application must be even and not missed, and it must not form a local effusion; the dry, strong water-absorbing substrate must be treated twice , The second pass must be done after the interface agent in the first pass has dried. 

(3) Generally, the drying time of the first interface agent is about 1 to 2 hours, and the drying time of the second interface agent is about 3 to 4 hours.

(4) Make sure that the interface agent is completely dry and has no accumulation before proceeding to the next step of construction

6. Self-leveling mortar construction:

(1) Partitions should be made in advance to ensure that a complete area is continuously poured at one time. 

(2) Accurately weigh the appropriate amount of clean water with a graduated cylinder and place it in a clean mixing bucket, start the electric mixer, slowly add the whole package of self-leveling materials, and continue to mix evenly for 3 to 5 minutes. Make it form a fluid slurry with uniform consistency and no agglomeration, and check the fluidity of the slurry. The amount of water added must be strictly controlled according to the requirements of self-leveling materials. 

(3) Pour the mixed fluid self-leveling material onto the base surface within the construction time, and let it flow flat like water. Should be tilted into a strip, and to ensure that the cast-in-situ strip and the previous can be merged together.

(4) The poured strip self-leveling material should reach the design thickness. If the design thickness of the self-leveling construction is less than or equal to 10mm, it is necessary to use a special self-leveling scraper for scraping to assist in leveling. 

(5) Pouring should be continuous, and the interval between two pourings should be within 10 minutes to avoid difficult to eliminate stubble. …

(6) After the slurry is spread, use a toothed scraper to spread the slurry and control the appropriate thickness. Let it stand for 3~5 minutes to let the air bubbles out of the package, and then use the defoaming roller to deflate. Help the slurry flow and remove the bubbles generated to achieve a good stubble effect. 

(7) Before self-leveling and initial setting, you must wear spikes to walk into the self-leveling ground and quickly roll the poured self-leveling ground with a defoaming roller to expel the air brought in during mixing, to avoid bubbles, hemp noodles, and noodles. The interface height difference between. 

(8) Used tools and equipment should be cleaned with water in time.


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7 Maintenance

The self-leveling ground after the completion of construction should be cured for 24 hours or more under the construction environmental conditions and can be used. During the curing period, avoid strong wind and air flow, and the temperature cannot be too high. When the temperature or other conditions are different from the normal construction environment conditions, the curing time needs to be adjusted according to the situation.

8 Finished product protection

The self-leveling ground after construction should be protected by finished products. During the protection period of the finished product, garbage, debris, paint and construction machinery should not be piled on the self-leveling ground to avoid contamination; blunt or sharp objects should not be used to hit or scratch the surface of the self-leveling ground. Can't walk on it.


Three, matters needing attention

1. Construction environment requirements: the temperature of the dry ground should not be lower than +10℃, and the relative humidity of the ground should be kept below 90%; there should be no excessive draught to avoid premature local drying.

2. Self-leveling ground requires higher requirements for the base layer. The base layer must not have loose concrete, grease, debris, or dust; the floor drain, trench, and split joints on the ground must be sealed with sponge strips; the original cushion The split joints should be sealed with the same material as self-leveling mortar. 

3. Before brushing the second interface agent and before self-leveling construction, the surface of the interface agent should be dry in order to obtain better connectivity. Pay attention to maintaining ventilation during construction.

4. It is best to use clean tap water for construction, so as not to affect the quality of surface perception.

5. The self-leveling ground must be continuously constructed without stopping; the use time is 30 minutes after adding water. After exceeding, the self-leveling mortar will gradually solidify, resulting in strength and losing fluidity. The pouring width can be determined according to the capacity of the pump and the thickness of the paving, usually no more than 10-12 meters; the ground that is too wide needs to be divided into small pieces with sponge strips for construction.


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6. After the gypsum-based self-leveling mortar is poured, the initial window ventilation and drying should be treated differently according to the material characteristics of the supplier. When pure semi-aqueous gypsum is used as the cementing material, the first opening of the window for ventilation shall not be earlier than 24h. When using type II anhydrous gypsum, or a cementing system mixed with cement and type II anhydrous gypsum, the initial opening of the windows for ventilation shall not be earlier than 72 hours.

7. In the gypsum-based self-leveling mortar with heating system, when the heating method is used for drying, first use natural ventilation to dry for 2 to 3 days, and then start to use heating assisted drying for drying.

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