18 strategies to answer common application questions of lightweight gypsum mortar

1. What materials are construction lightweight gypsum mortars made of? What are the common uses for lightweight gypsum mortar in construction?

Answer: Construction lightweight gypsum mortar is composed of inorganic cementitious materials, fine aggregate and water, sometimes mixed with certain admixtures. Construction lightweight gypsum mortar is often used for masonry (such as brick, stone, block) structures, plastering of internal and external surfaces of buildings (such as walls, floors, ceilings), joints of large wall panels and masonry walls, and Bonding of decorative materials, etc.

2. How are construction lightweight gypsum mortars classified?

Answer: Construction lightweight gypsum mortar is classified according to its use: it can be divided into lightweight gypsum mortar for masonry and lightweight gypsum mortar for plastering. Plastering lightweight gypsum mortar includes ordinary plastering lightweight gypsum mortar, decorative plastering lightweight gypsum mortar, and special plastering lightweight gypsum mortar. Special lightweight gypsum mortar includes waterproof lightweight gypsum mortar, acid-resistant lightweight gypsum mortar, insulating lightweight gypsum mortar, sound-absorbing lightweight gypsum mortar, etc.

Construction lightweight gypsum mortar is classified according to cementing materials: it can be divided into cement lightweight gypsum mortar, lime lightweight gypsum mortar, and mixed lightweight gypsum mortar. Mixed lightweight gypsum mortar can be further divided into: cement lime lightweight gypsum mortar, cement clay lightweight gypsum mortar, lime clay lightweight gypsum mortar, lime fly ash lightweight gypsum mortar, etc.

3. What is lightweight gypsum mortar for masonry? What materials does lightweight gypsum mortar for masonry consist of?

Answer: The lightweight gypsum mortar that binds bricks, stones, blocks, etc. into masonry is called masonry lightweight gypsum mortar.

The material composition of lightweight gypsum mortar: cement, other cementitious materials (such as lime paste, clay paste, etc.), fine aggregate and water.

4. What should you pay attention to when choosing lightweight gypsum mortar for masonry?

Answer: The appropriate cement variety can be selected according to the design requirements, masonry location and environmental conditions. Selecting medium and low strength cement can meet the requirements. The strength grade of cement used in cement lightweight gypsum mortar should not be greater than 32.5; the strength grade of cement used in cement mixed light gypsum mortar should not be greater than 42.5.

When quicklime is slaked into lime paste, it should be filtered through a mesh with a pore size no larger than 3mm×3mm, and the slaking time should not be less than 7 days; the slaking time of finely ground quicklime powder should not be Less than 2 days. For lime paste stored in the sedimentation tank, measures should be taken to prevent drying, freezing and pollution. It is strictly prohibited to use dehydrated and hardened lime paste. The consistency of the lime paste used should be controlled at about 120mm.

The sand used for lightweight gypsum mortar should be medium sand, among which coarse sand should be used for rubble masonry, and its mud content should not exceed 5%; strength M2.5 cement mixed with light gypsum mortar, the mud content of the sand should not exceed 10%. When mixing light gypsum mortar, clean water without harmful impurities should be used to mix light gypsum mortar.

5. What properties should the mixed lightweight gypsum mortar have?

Answer: The mixed lightweight gypsum mortar should have the following properties: meet workability requirements; meet design type and strength grade requirements; have sufficient bonding force.

6. What are the properties of lightweight gypsum mortar for masonry construction? What does the workability of lightweight gypsum mortar include?

Answer: The properties of lightweight gypsum mortar for masonry include the workability of lightweight gypsum mortar, the strength of lightweight gypsum mortar and the bonding force of lightweight gypsum mortar . The workability of lightweight gypsum mortar includes fluidity and water retention.

7. What is used to express the fluidity of lightweight gypsum mortar, and what are its influencing factors?

Answer: The fluidity of light gypsum mortar is also called consistency, which refers to the flow performance under its own weight or external force, expressed by “sinkage”. The degree of sinking is large and the lightweight gypsum mortar has high fluidity, but if the fluidity is too large, the strength will be reduced after hardening; if the fluidity is too small, it will be inconvenient for construction operations.

The fluidity of lightweight gypsum mortar is related to the type of masonry material, construction conditions, climate conditions and other factors. For porous water-absorbent masonry materials and dry and hot weather, the lightweight gypsum mortar is required to have greater fluidity; on the contrary, for dense non-water-absorbent materials and humid and cold weather, it is required to have less fluidity.

8. What is the water retention of lightweight gypsum mortar? What is the water retention of lightweight gypsum mortar used to express? What are its requirements?

Answer: The ability of freshly mixed lightweight gypsum mortar to retain moisture is called water retention. Water retention also refers to the difficulty in separating the various components of lightweight gypsum mortar. nature. The water retention of lightweight gypsum mortar is expressed by the “degree of delamination”.

The degree of delamination is preferably between 10~20mm and should not be greater than 30mm. Lightweight gypsum mortar with a delamination degree greater than 30mm is prone to segregation and is inconvenient for construction; lightweight gypsum mortar with a delamination degree close to zero is prone to shrinkage cracks.

9. Why is compressive strength often used as the main technical indicator of lightweight gypsum mortar in engineering?Standard? How is the strength grade of lightweight gypsum mortar determined? What are the strength grades of lightweight gypsum mortar for masonry?

Answer: Lightweight gypsum mortar mainly plays a role in transmitting loads in masonry. Tests have proved that the bonding strength and durability of lightweight gypsum mortar increase with the increase of compressive strength, that is, there is a certain correlation between them, and the test method of compressive strength is relatively mature and the test is relatively simple and accurate. Therefore, compressive strength is often used as the main technical indicator of lightweight gypsum mortar in engineering. The strength grade of lightweight gypsum mortar is based on a cube test block with a side length of 70.7mm. Under standard curing conditions (cement mixed lightweight gypsum mortar is a temperature of 20±2°C and a relative humidity of 60%~80%; cement lightweight gypsum mortar It is determined by measuring the compressive strength at the age of 28 days using standard test methods at a temperature of 20±2℃ and a relative humidity of more than 90%. The strength grades of lightweight gypsum mortar for masonry include M20, M15, M10, M7.5, M5, and M2.5.

10. What are the factors that affect the strength of lightweight gypsum mortar?

Answer: There are many factors that affect the strength of lightweight gypsum mortar. Experiments have shown that when the quality of raw materials is constant, the strength of lightweight gypsum mortar mainly depends on the cement strength grade and cement dosage.

11. What factors affect the adhesion of lightweight gypsum mortar?

Answer: The bonding force of lightweight gypsum mortar for masonry increases with its strength. The higher the strength level of lightweight gypsum mortar, the greater the bonding force. The bonding force of lightweight gypsum mortar is related to the surface condition, cleanliness, moisture and construction and maintenance conditions of the masonry. Therefore, before masonry, the bricks should be watered and moistened, and their moisture content should be controlled at about 10% to 15%. The surface should not be stained with soil to improve the bonding force between the lightweight gypsum mortar and the bricks and ensure the quality of the masonry.

12. What basic requirements should be met for the mix design of lightweight gypsum mortar for masonry construction?

Answer: The mix design of lightweight gypsum mortar for masonry should meet the following basic requirements:

( 1) The workability of the lightweight gypsum mortar mixture should meet the construction requirements, and the volume density of the mixture: cement lightweight gypsum mortar ≮1900kg/m3; cement mixed lightweight gypsum mortar ≮1800 kg/m3.

(2) The strength and durability of lightweight gypsum mortar for masonry construction should meet the design requirements.

(3) It should be economically reasonable, and the amount of cement and admixtures should be small.

13. What are the applications of lightweight gypsum mortar in masonry construction?

Answer: Cement lightweight gypsum mortar is suitable for masonry construction in humid environments and high strength requirements; cement lime lightweight gypsum mortar is suitable for masonry construction Masonry in a dry environment; walls of multi-story houses generally use cement lime light gypsum mortar with a strength grade of M5; brick columns, brick arches, reinforced brick lintels, etc. generally use cement light gypsum with a strength grade of M5~M10 Mortar; Brick foundations generally use cement light gypsum mortar not less than M5; low-rise houses or bungalows can use lime light gypsum mortar; simple houses can use lime clay light gypsum mortar.

14. What are the requirements for plastering lightweight gypsum mortar?

Answer: The lightweight gypsum mortar for plastering the surface requires good workability and can be easily spread into a uniform and thin layer for easy construction. It should also have high bonding strength, and the lightweight gypsum mortar layer should be firmly bonded to the bottom surface and will not crack or fall off for a long time. Parts that are in humid environments or susceptible to external forces (such as floors, wall skirts, etc.) should also have high water resistance and strength.

15. What are the main functions of ordinary plastering lightweight gypsum mortar?

Answer: The function of ordinary plastering lightweight gypsum mortar is mainly to protect walls and floors from erosion by wind, rain and harmful impurities, and to improve moisture resistance, corrosion resistance and weathering resistance. performance, increase durability; at the same time, it can make the surface of the building smooth, clean and beautiful.

16. What is plastering lightweight gypsum mortar? What categories can plastering lightweight gypsum mortar be divided into according to its different construction functions?

Answer: Any lightweight gypsum mortar applied to the surface of a building or building component is collectively called plastering lightweight gypsum mortar.

According to the different functions of plastering lightweight gypsum mortar, plastering lightweight gypsum mortar can be divided into ordinary plastering lightweight gypsum mortar, decorative lightweight gypsum mortar and certain types of plastering lightweight gypsum mortar. Some special functions of plastering lightweight gypsum mortar (such as waterproof lightweight gypsum mortar, thermal insulation lightweight gypsum mortar, sound-absorbing lightweight gypsum mortar, acid-resistant lightweight gypsum mortar, etc.).

17. Ordinary plastering of lightweight gypsum mortar is usually divided into how many layers of construction? What are the different functions and requirements of each layer of lightweight gypsum mortar?

Answer: Ordinary plastering of lightweight gypsum mortar is usually divided into two or three layers for construction. Each layer of lightweight gypsum mortar has different requirements, so the lightweight gypsum mortar selected for each layer is also different. Generally, the bottom layer of lightweight gypsum mortar plays the role of bonding the base layer. It is required that the lightweight gypsum mortar should have good workability and high bonding force. Therefore, the bottom layer of lightweight gypsum mortar should have good water retention, otherwise the water will easily be absorbed by the base layer material. Absorption affects the adhesion of lightweight gypsum mortar. The rougher surface of the base layer is beneficial to the bonding with light gypsum mortar. The middle layer of plastering is mainly for leveling, and sometimes it can be omitted. The main purpose of plastering the surface is to make it smooth and beautiful, so fine sand should be used.

18. How to choose the bottom plaster for brick walls, slat walls or slat ceilings, concrete walls, etc., and places that are prone to collision or moisture?

Answer: For the bottom plaster of brick walls, lime light gypsum mortar is mostly used; for the bottom plaster of lath walls or lath ceilings, mixed light gypsum mortar is mostly used. High-quality gypsum mortar or lime light gypsum mortar; for bottom plastering of concrete walls, beams, columns, roofs, etc., mixed light gypsum mortar, hemp lime mortar or paper reinforced lime mortar is often used.

�The bottom layer of lightweight gypsum mortar must have good water retention, otherwise the water will be easily absorbed by the base material and affect the adhesion of the lightweight gypsum mortar. The rougher surface of the base layer is beneficial to the bonding with light gypsum mortar. The middle layer of plastering is mainly for leveling, and sometimes it can be omitted. The main purpose of plastering the surface is to make it smooth and beautiful, so fine sand should be used.

18. How to choose the bottom plaster for brick walls, slat walls or slat ceilings, concrete walls, etc., and places that are prone to collision or moisture?

Answer: For the bottom plaster of brick walls, lime light gypsum mortar is mostly used; for the bottom plaster of lath walls or lath ceilings, mixed light gypsum mortar is mostly used. High-quality gypsum mortar or lime light gypsum mortar; for bottom plastering of concrete walls, beams, columns, roofs, etc., mixed light gypsum mortar, hemp lime mortar or paper reinforced lime mortar is often used. </p