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Self-leveling gypsum is the abbreviation of self-leveling ground leveling gypsum, also known as gypsum-based self-leveling mortar. It is a kind of special purpose made from gypsum materials, special aggregates and various construction chemical additives that are carefully configured and mixed uniformly in the factory. Dry powder mortar leveled on the ground.

Construction Preparation

1. Material: 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 gauge, fluidity tester.

(3) Auxiliary equipment: water pipe, wire and cable, bottom coating roller brush, soft brush, measuring cylinder, toothless scraper, special scraper for gypsum-based self-leveling mortar (fine tooth scraper), defoaming roller, spike shoes, trowel Knife, trowel, shovel, etc.

3. Staffing

The configuration of construction personnel should be determined according to the construction area, and generally should include: mechanics (self-leveling mixing, ground polishing, vacuum cleaners, electric cutting machines, etc.), bricklayers (repair, leveling), workers (sweeping, handling, painting) Brush interface agent), management personnel (site management, quality control, etc.)

Electric mixer

Trowel, spikes, defoaming roller, fine tooth scraper

Construction technology

1. Close the 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 to close the site. Construction requires the cleanliness of the base and the environment, without interference from other types of work, and no interruption or pause is allowed.

2. Grassroots inspection

Thoroughly check the surface of the base layer for defects such as sanding, hollowing, shelling, peeling, loosening, pitting, grease, dust, cracks, etc. The surface dryness and flatness should meet the requirements.

3. Grassroots cleanup and treatment

(1) Remove the grease, wax and other contaminants on the base layer with a cleaning agent. If necessary, use a scrubber to clean the ground. Dust, unsturdy concrete surface, grease, cement slurry or putty and may affect the bonding strength The impurities, etc. are cleaned up, so that the base is dense, and the surface is free of looseness and debris.

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

(3) Use special repair mortar to repair the honeycomb and holes of the base layer. Large areas of hollow drums should be completely removed and re-constructed; local hollow drums should be treated with grouting or other methods.

4. Elevation control.

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

5. Brush the interface agent

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

(2) According to the requirements of the interface agent instructions, use a roller to apply the interface agent to the ground. The coating should be even, without omission, and it should not be allowed to form local effusion; it should be processed twice for dry, strong water-absorbing substrates , The second pass should be applied after the first pass of the interface agent.

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

(4) Ensure that the interface agent is completely dry, and there is no accumulation before proceeding to the next step of construction.

6. Self-leveling mortar construction

(1) It should be partitioned in advance to ensure continuous pouring of the entire area at one time.

(2) Accurately weigh the right amount of clean water into a clean mixing bucket with a water tank, start the electric mixer, slowly add the entire package of self-leveling material, and continue to mix evenly for 3 to 5 minutes. Make it into a fluid slurry with uniform consistency and no caking, 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) Tilt the agitated fluid self-leveling material to the base surface within the construction time, and let it flow like water. It should be tilted into strips, and ensure that the cast-in-place strip and the previous one can flow together.

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

(5) Continuous casting should be performed. The interval between the two castings should be within 10 minutes to avoid difficult removal of the stubble.

(6) After spreading the slurry, spread the slurry with a toothed scraper and control the appropriate thickness. Let it stand for 3 to 5 minutes to let the bubbles inside be discharged, and then use the defoaming roller to deflate. To help the slurry flow and remove the bubbles generated, to achieve a good stubble effect.

(7) Before the initial leveling of the self-leveling, you must wear spiked shoes to walk into the self-leveling ground and quickly roll the cast self-leveling ground with a defoaming roller to discharge the air brought in during stirring to avoid bubbles, pits and strips. The height difference between the interfaces.

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

7. Maintenance

After the construction is completed, the self-leveling ground should be maintained under the construction environment for more than 24h before it can be used. During the curing period, strong wind flow should be avoided, and the temperature should not 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

After the construction is completed, the self-leveling ground shall be well protected. During the protection of finished products, garbage, debris, paint and construction machinery should not be piled on the self-leveling ground that has been prepared to avoid contamination; the surface layer of the self-leveling ground cannot be hit or scored with blunt objects, sharp objects, or Can’t walk on it.

Matters needing attention

1. Construction environment requirements: the temperature of the dry ground should not be lower than +10C, and the relative humidity of the ground should be kept below 90%; do not have excessive wind through the hall to avoid local premature drying.

2. The self-leveling ground has higher requirements for the base layer. The base layer must not have loose concrete, grease, debris, and dust; the floor drains, trenches, grid joints, etc. on the ground must be sealed with sponge strips; the original cushion place The remaining joints should be closed with the same material as the self-leveling mortar.

3. Before brushing the second interface agent and before self-leveling construction, the surface of the interface agent should be dried in order to obtain better connectivity. Care should be taken to maintain ventilation during construction.

4. The best water for construction is clean tap water, so as not to affect the appearance and quality of the surface.

5. The self-leveling ground must be constructed continuously without stopping in the middle; the use time after adding water is 20~30 minutes. After exceeding, the self-leveling mortar will gradually solidify, producing strength and losing fluidity. The pouring width can be determined according to the capacity of the pump and the thickness of the paving, usually not more than 10~12 meters; the too wide ground needs to be separated into small pieces with sponge strips for construction.

When dry POP(plaster of paris) powder is mixed with water it hardens. This material which can be applied over brick, block or concrete surface to form a smooth surface is called gypsum plaster.

Earlier, a 6 mm coat of gypsum plaster (termed as POP punning) is usually applied on the top of cement plaster to give a smooth finish to it before painting. This is a two stage process and involves various elements like sand, cement and water which has to be mixed onsite. This process is slowly being replaced by a direct application of single coat of gypsum plaster. In gypsum plaster, readymade POP powder is mixed with water and applied directly on the wall.

Gypsum Plaster can be applied directly on any brick, solid or hollow blocks, AAC blocks and plaster boards. Gypsum plaster has good insulation properties, fire resistant and impact resistant. Also, gypsum saves a lot of time during construction and has superior finish. These properties have clearly drawn attention of real estate builders and contractors towards choosing gypsum plaster over traditional cement plaster.

The autoclaved aerated concrete product is a new type of light and porous green environmental protection building material that uses cement, lime and silica sand as the main raw materials and then adds different amounts of anti-corrosion reinforced steel mesh according to the structural requirements. After high-temperature, high-pressure and steam curing, its density is lower than that of ordinary cement materials, and it has good performances such as fire resistance, fire prevention, sound insulation, heat insulation and heat preservation.

(1) Thermal insulation, thermal insulation

During the production of autoclavedaerated concrete products, numerous tiny pores are formed inside. These pores form a static air layer in the material, so that the autoclavedaerated concrete product has good thermal insulation performance. Its thermal insulation is six times that of glass, seven times that of clay bricks, and ten times that of ordinary concrete.

(2) Fire resistance, flame retardant

Autoclaved aerated concrete is an inorganic substance that will never burn and will not produce harmful gases even at high temperatures. At the same time, the thermal conductivity of autoclaved aerated concrete is very small, which makes the heat conduction slow, effectively resists fire, and protects its structure from fire.

(3) Sound absorption,noise reduction

The autoclaved aerated concrete is filled with small pores, which has good sound insulation effect, and can reduce the noise of 30~50 dB by its thickness.

(4) Portability

The weight of autoclaved aerated concrete is only 550~650 kg per cubic meter, which is 1/4 of ordinary concrete and 1/3 of clay brick, which is equivalent to wood. The use of autoclaved aerated concrete in construction can reduce the weight of the building, reduce the cross-sectional size of structural members, reduce the cost of foundation, and reduce the difficulty of construction of weak foundation.

(5) Workability

Just like wood, autoclaved aerated concrete products can be sawed, drilled, nailed, and ground more easily.

 

As a new product to replace cement mortar, gypsum mortar has the strength of traditional cement, and is more environmentally friendly and durable than cement. It has a strong adhesive force and is not prone to powdering, cracking, hollowing, etc., and it is easier to use. The cost is lower. So what is the construction process of gypsum mortar plastering? Let’s take a look at the plaster mortar plastering construction method.

Grassroots processing

1. Clean up dust, oil stains, dirt, separators and other impurities on the surface of the grassroots before construction;

2. The uneven parts and openings on the base should be handled clearly and kept flat and firm;

3. The gap between the door and window frame and the wall should be infilled according to the doors and windows of various materials;

4. Wet the base layer with water in advance, pay attention to the surface without clear water before plastering;

5. Start to make corners around walls, doors, windows and pillars.

Gypsum mortar plastering process

1. Ceiling

Spring line-plastering cake-lower ruler-upper ruler-plastering the concrete window sill-wall punching-plastering of the floor-plastering of the face.

2. Wall

Find the rules to paste the gray cake-wipe the skirting-make the corner of the door and window hole-wipe the cement window sill-wall punching-wipe the bottom dust-wipe the face dust.

Gypsum mortar plastering operation process

1. Determine the plastering sequence, first up and then down, starting from the side of the door, the entire wall is continuously operated;

2. The ordinary concrete ceiling can be plastered with plaster plaster;

3. According to the flatness of the wall base, signs or standard bars should be set; the distance between the vertical standard bars should be 1.2-1.5 meters, and the width of the standard bars should be 0.03-0.05 meters;

4. If the thickness of plastering is less than 0.05 meters, it can be plastered directly with gypsum mortar, if it is more than 0.05 meters, it can be directly grounded with a light bottom layer, and then plastered with a surface layer;

5. Plaster the gypsum mortar to the base layer according to the designed thickness, and then use H-shaped ruler and scraper to stick closely to the ribs and scrape the flat layer of ash on the top, bottom, left and right;

6. Press with a trowel, then check the flatness of the wall with a ruler;

7. After plastering, pay special attention to clean up the relevant positions in time;

8. When plastering mortar, plaster should be cleaned. After calendering, pay attention to good ventilation and avoid washing the finish with water. After the construction is completed, remember to clean the plastering tools in time.

The above is all about the construction process of gypsum mortar plastering. The selection of gypsum mortar plastering can reduce about 10-15%, and effectively reduce the rework phenomenon. It is a high-quality environmental protection product with the development of new technologies.

The choice of plastering gypsum raw materials and proper aggregate gradation are the main reasons that directly affect the quality of the product. Sand is one of the main raw materials for the production of plastering gypsum mortar. The demand and use of construction sand in plastering gypsum mortar are very large. The demand for natural sand accounts for the vast majority, but their distribution is extremely uneven, and in recent years in the large-scale exploitation in the past, natural sand resources have been quite scarce. In addition, as the requirements for environmental protection are getting higher and higher, many areas have banned the excavation of natural sand, which makes the contradiction between supply and demand of sand increasingly prominent. The situation is forced to find resources to replace natural sand. Taking materials locally and making full use of local resources or some industrial solid waste such as tailings sand, slag, coal gangue, steel slag to replace natural sand. This is not only environmentally friendly, but also canachieve better economic and social benefits. Therefore, we must understand and treat separately in the application of plastering gypsum mortar according to different regions, different sand source conditions, and different aggregates.

1. The role of natural sand in plastering gypsum mortar and its influence on performance

Sand is an inert material that does not participate in chemical reactions in plastering gypsum mortar. It acts as a skeleton or filler in plastering gypsum mortar. The density of plastering gypsum mortar can be adjusted by sand gradation to control the crack resistance of plastering gypsum mortar. The adjustment of sand grading should take into account the fineness and gradation of sand. In the configuration of plastering gypsum mortar, it has poor water retention, good crack resistance, high strength and low fluidity with coarse sand. And it has good water retention, excellent adhesion, but the surface with poor crack resistance, easy to produce micro-cracks on the surface with fine sand.

The thickness of the sand directly affects the required amount of gypsum mortar, which affects the mix design of the plastering gypsum mortar, and also affects the performance of the mortar and the performance of the mortar hardened body. When the particle size of the sand is large, the specific surface area is relatively small, and the amount of gypsum material covering the sand is relatively small. As the particle size of the sand becomes finer and the specific surface area increases, the demand for gypsum mortar coating the sand increases significantly. As the fineness of the sand decreases, the water consumption of the plastering gypsum mortar increases, and the density of the mixedplastering gypsum mortar decreases, resulting in a decrease in its strength. The thickness of the sand has a decisive influence on the strength of the plastering gypsum mortar.

Natural sand has a smooth surface and is mostly round. In the process of configuring plastering gypsum mortar, lower gypsum dosage and mixing water can meet the needs. Natural sand with reasonable gradation is undoubtedly ideal aggregatefor producing plastering gypsum mortar.

Generally, the particles of natural sand are more uniform, and the gradation is also good. The dry density of the plastering gypsum mortar hardened body using medium sand is higher than that using fine sand (in the case of the same strength), but per cubic meter of the amount of hydrated gypsum powder, admixtures and additives in lime gypsum are all reduced. If the fineness of the sand becomes finer, the amount of water used increases, the density of the mortar decreases, the stability of the mortar also deteriorates, and the bleeding phenomenon is also likely to occur, which increases the amount of additives such as retarder and water retaining agent in the formulation. At the same time, the compressive strength of the plastering gypsum mortar hardened body will also be reduced, which will increase the cost of plastering gypsum mortar materials.

In construction sand, the sand with a fineness modulus in the range of 3.7–3.0 is coarse sand, the sand in the range of 3.0–2.0 is medium sand, the sand in the range of 2.0–1.0 is fine sand, and the sand in the range of 1.0–0.1 is extra fine sand. Plastering gypsum mortar generally uses the gradation of medium sand with fine sand and extra fine sand. A large amount of medium sand forms the skeleton, a small amount of fine sand fills the larger voids, and the extra fine sand fills the smaller voids. The gypsum mortar is evenly wrapped and adheres to the sand grains to form a relatively dense system. The mud in natural sand is harmful to plastering gypsum mortar, and its content must be strictly controlled. Because the mud is an inactive substance with very fine particles, it will absorb a lot of water, which will make the interface between the gypsum mortar and the aggregates poor. In addition, the water it adsorbs is free water, which will cause poor water retention and easy cracking of plastering gypsum mortar.

2. Effect of extra fine sand on plastering gypsum mortar configuration

At present, there is less and less medium-fine sand resources for construction. In some areas, due to the causal relationship between geographical location and climatic conditions, a large amount of extra-fine sand is generated. The use of extra-fine sand in the configuration of plastering gypsum mortar should obviously affect the workability of plastering gypsum mortar  and the strength of hardened body. The ultra-fine sand particles are fine and have a large specific surface area. When using it to prepare plastering gypsum mortar, the sand content is lower. The reason is that the ultra-fine sand particles are poorly graded, the mud content exceeds the standard, and the amount of water used increases and it is easy to bleed. The amount of gelling materials and additives should be increased. When the proportion of extra-fine sand is increased, the adhesion performance of plastered gypsum mud is increased, the fluidity and workability are deteriorated, and the risk of shrinkage and cracking is increased. When used in gradation with medium sand, extra-fine sand accounts for 20%-30% is better.

In the application of extra fine sand, adding appropriate amount of secondary fly ash can effectively improve the workability of plastering gypsum mortar, make up for its inherent deficiencies, the role is to replace part of the fine aggregate to improve the strength and performance of plastering gypsummortar. In short, the larger the cement-to-sand ratio of ultrafine sand, the lower its strength and the worse its adhesion.