Eighteen questions about mortar technology
1. What materials are used to make building mortar? What is the general use?
A: Building mortar is make up of inorganic cementitious materials, fine aggregates and water, sometimes mix with certain admixtures.Construction mortar is often use for masonry (such as brick, stone, block) structures, plastering of interior and exterior surfaces of buildings (such as walls, floors, ceilings), joints of large wall panels, masonry walls, and decorative materials. Bonding, etc.
2. How is the construction mortar classify?
A: Building mortar is classify according to use: it can be divide into masonry mortar and plastering mortar. The plastering mortar includes ordinary plastering mortar, decorative plastering mortar, and special mortar. Special mortars include waterproof mortar, acid-resistant mortar, thermal insulation mortar, sound-absorbing mortar and so on.
Construction mortar is classified according to cementitious materials: it can be divide into cement mortar, lime mortar and mix mortar. Mixed mortar can be further divided into: cement lime mortar, cement clay mortar, lime clay mortar, lime fly ash mortar and the like.
3. What is masonry mortar? What materials are used for masonry mortar?
A: The mortar that bonds bricks, stones, blocks, etc. into a masonry is call masonry mortar.
The material composition of the masonry 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 masonry mortar?
Answer: Cement can choose the appropriate cement type according to the design requirements, the masonry location and the environmental conditions. Choosing medium and low strength cement can meet the requirements. The cement used in cement mortar should not exceed 32.5 grades; the cement used in cement mortar should not exceed 42.5.
When the quicklime is mature into lime paste, the mesh with a pore diameter of not more than 3 mm×3 mm should be use for filtration, and the ripening time should not be less than 7 days; the ripening time of the ground fine lime powder should not be less than 2 days. The lime paste stored in the sedimentation tank should be take to prevent drying, freezing and pollution. It is strictly forbidden to use dehydrate and hardened lime paste. The consistency of the lime paste use should be controlled to about 120 mm.
The sand used for masonry mortar should be medium sand. The masonry should be coarse sand, and the mud content should not exceed 5%. The cement mortar with strength grade M2.5 should not exceed 10 mud. %. Mix the mortar with water, and use clean water without harmful impurities to mix the mortar.
5. What properties should the mortar after mixing have?
Answer: The mortar after mixing should have the following properties: meet the requirements of workability; meet the design type and strength grade requirements; have sufficient adhesion.
6. What are the properties of the masonry mortar and what is the content of the mortar?
A: The properties of masonry mortar include the workability of the mortar, the strength of the mortar and the adhesion of the mortar. Mortar workability includes fluidity and water retention.
7. What is the fluidity of the mortar, and what are the influencing factors?
A: The fluidity of mortar is also call consistency. It refers to the performance of flow under the action of self-weight or external force. It is expressed by “sinking degree”.
The sinking degree is large, the mortar has great fluidity, but the fluidity is too large, and the strength will be reduce after hardening; if the fluidity is too small, the construction operation is not convenient.
The fluidity of the mortar is relate to the types of masonry materials, construction conditions and climatic conditions. For porous water-absorbing masonry materials and dry and hot weather, the fluidity of the mortar is require to be larger; on the contrary, for dense and non-absorbent materials and wet and cold weather, the fluidity is required to be smaller.
8. What is the water retention capacity of the mortar, and what is the water retention capacity of the mortar? What are the requirements?
A: The ability of fresh mortar to retain moisture is called water retention. Water retention also refers to the property that the constituent materials in the mortar are not easily separate. The water retention of the mortar is expressed by “stratification”.
The stratification should be between 10 and 20 mm, and should not be greater than 30 mm. Mortar with a delamination of more than 30 mm is prone to segregation and is not convenient for construction; mortar with a stratification close to zero is prone to shrinkage cracking.
9. Why is the compressive strength often use as the main technical index of mortar in the project? How is the strength grade of the mortar determine? What are the strength grades of the masonry mortar?
Answer: Mortar mainly plays the role of transmitting load in the masonry. The test proves that the bond strength and durability of the 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 mature, the test is simple and accurate, so the engineering The compressive strength is often use as the main technical index of the mortar.
The strength grade of mortar is a cube test piece with a side length of 70.7mm. Under standard curing conditions (cement mixing mortar is 20±2°C, relative humidity is 60%~80%; cement mortar is temperature 20±2°C, relative humidity). Above 90%), the compressive strength at 28 days of age was determine by standard test methods. The strength grade of masonry mortar is M20, M15, M10, M7.5, M5, M2.5.
10. What are the factors that affect the strength of the mortar?
A: There are many factors affecting the strength of mortar. Experiments have shown that when the quality of raw materials is constant, the strength of mortar depends mainly on the strength grade of cement and the amount of cement.
11. What are the effects of the bonding strength of masonry mortar?
Answer: The adhesion of masonry mortar increases with the increase of its strength. The higher the mortar strength grade, the greater the adhesion. The adhesion of the mortar is related to the surface state, cleanliness, wetness and construction and maintenance conditions of the masonry. Therefore, the bricks before the masonry should be water and moist, and the water content should be control at 10%~15%. The surface should not be soil to improve the adhesion between the mortar and the brick to ensure the quality of the masonry.
12. What are the basic requirements for masonry mortar mix design?
Answer: The mix design of masonry mortar should meet the following basic requirements:
(1) The workability of the mortar mixture should meet the construction requirements, and the bulk density of the mixture: cement mortar ≮ 1900kg / m3; cement mixed mortar ≮ 1800 kg / m3.
(2) The strength and durability of the masonry mortar should meet the design requirements.
(3) It should be economically reasonable, and the amount of cement and admixture should be less.
13. What are the applications of masonry mortar in the project?
Answer: Cement mortar should be use for masonry with high humidity and high strength; cement lime mortar should be used for masonry in dry environment; wall of multi-storey building is generally cement mortar with strength grade M5 Brick mortar, brick arch, reinforced brick lintel, etc. generally use cement mortar with strength grade M5~M10; brick foundation generally adopts cement mortar not lower than M5; limestone mortar can be used for low-rise houses or bungalows; lime can be used for simple houses Clay mortar.
14. What are the requirements for plastering?
Answer: The mortar is require to have good workability, and it is easy to be smear into a uniform and even thin layer for easy construction. It should also have a high cohesive force, and the mortar layer should be able to bond firmly to the bottom surface without cracking or falling off for a long time. In a humid environment or vulnerable to external forces (such as the ground, wall skirts, etc.), should also have high water resistance and strength.
15. What are the main functions of ordinary plastering mortar?
A: The function of ordinary plastering mortar is to protect the wall and the ground from the wind and rain and harmful impurities, improve the moisture resistance, corrosion resistance, weathering resistance and durability, and at the same time make the building surface smooth, clean and beautiful. effect.
16. What is the plastering mortar? Which types can be classified according to the different building functions of the plastering mortar?
A: Any mortar apply to the surface of a building or building component is collectively refer to as a mortar.
According to the different functions of the plastering mortar, the plastering mortar can be divide into ordinary plastering mortar, decorative mortar and plastering mortar with certain special functions (such as waterproof mortar, thermal insulation mortar, sound absorbing mortar, acid resistant mortar, etc.)
.
17. Ordinary plastering mortar is usually divide into several layers of construction. What is the difference between the functions and requirements of each layer of mortar?
A: Ordinary plastering mortar is usually divide into two or three layers for construction. The mortar requirements vary from layer to layer, so the mortar use for each layer is different. Generally, the bottom mortar acts as a bonding base layer, and the mortar should have good workability and high adhesion. Therefore, the water retention of the bottom mortar is better, otherwise the moisture is easily absorbe by the base material and affects the adhesion of the mortar. The surface of the base layer is rougher to facilitate bonding with the mortar. The middle plaster is mainly for leveling, sometimes it can be omitted. The surface plastering is mainly for the sake of smoothness and beauty, so fine sand should be select.
18. How should brick walls, slat walls or slat roofs, concrete walls, etc., and underlying plasters that are prone to collision or moisture?
A: The bottom layer plaster used for brick walls, mostly with lime mortar; the bottom layer plaster used for slat wall or slat roof is mix mortar or lime mortar; the concrete wall, beam, column, roof and other bottom plastering mixed mortar , hemp mortar or paper gluten lime slurry.