1. What materials are used to construct mortar?
Answer: The building mortar is composed of inorganic cementitious materials, fine aggregate and water, sometimes mixed with some admixtures. Construction mortar is often used for masonry (such as brick, stone, block) structure, the surface of the building's internal and external surfaces (such as wall, floor, ceiling), the joint of large wall panels, masonry walls, and decorative materials Bonding etc.
2. How is the construction mortar classified?
Answer: The construction mortar is classified according to the purpose: it can be divided into masonry mortar and surface mortar. The surface mortar includes ordinary surface mortar, decorative surface mortar, and special mortar. Special mortars include waterproof mortar, acid-resistant mortar, thermal insulation mortar, sound-absorbing mortar, etc. Construction mortar is classified according to cementing materials: it can be divided into cement mortar, lime mortar and mixed mortar. Mixed mortar can be divided into: cement lime mortar, cement clay mortar, lime clay mortar, lime fly ash mortar, etc.
3. What does masonry mortar consist of?
Answer: The mortar that bricks, stones, blocks, etc. are bonded into masonry is called masonry mortar. Material composition of masonry mortar: cement, other cementitious materials (such as lime paste, clay paste, etc.), fine aggregate and water.
4. What should be paid attention to when choosing masonry mortar?
Answer: Cement can be selected according to design requirements, masonry location and environmental conditions. Choose low and medium strength cement to meet the requirements. The strength grade of cement used in cement mortar should not be greater than 32.5; the strength grade of cement used in cement mixed mortar should not be greater than 42.5.
When the quicklime is matured into lime paste, it should be filtered with a mesh with a pore size of not more than 3mm×3mm, and the curing time should not be less than 7 days; the curing time of the ground quicklime powder should not be less than 2 days. The lime paste stored in the sedimentation tank shall take measures to prevent drying, freezing and pollution. The use of dehydrated lime paste is strictly prohibited. The consistency of the lime paste used should be controlled at about 120mm.
Medium sand should be used for masonry mortar, and rough sand should be used for masonry masonry, and its mud content should not exceed 5%; for cement mixed mortar with strength class M2.5, the sand content of sand should not exceed 10 %. For mixing mortar water, clean water without harmful impurities should be used for mixing mortar.
5. What properties should the mixed mortar have?
Answer: The mixed mortar should have the following properties: meet the requirements of workability; meet the requirements of design type and strength level; have sufficient adhesion.
6. What are the properties of masonry mortar?
Answer: The properties of masonry mortar include the ease of mortar, the strength of the mortar and the adhesion of the mortar. Mortar and workability include fluidity and water retention.
7. What is the fluidity of mortar? What are its influencing factors?
Answer: The fluidity of mortar is also called consistency, which refers to the performance of flowing under the action of self-weight or external force, and is expressed by "submergence". The immersion degree is large, and the mortar has high fluidity, but the fluidity is too large, and the strength will be reduced after hardening; if the fluidity is too small, it is not convenient for construction operations.
The fluidity of mortar is related to the types of masonry materials, construction conditions and climatic conditions. For porous masonry materials and dry and hot weather, the fluidity of the mortar is required to be greater; on the contrary, for materials that are dense and non-absorbent and wet and cold weather, the fluidity is required to be less.
8. What is the water retention of mortar, what is the water retention of mortar, and what are its requirements?
Answer: The ability of freshly mixed mortar to retain moisture is called water retention, and water retention also refers to the property that the constituent materials in mortar are not easy to separate. The water retention of mortar is expressed by "degree of delamination". The degree of delamination is preferably between 10 and 20mm, and shall not be greater than 30mm. Mortar with a delamination greater than 30mm is prone to segregation and is not convenient for construction; mortar with a delamination close to zero is prone to dry shrinkage cracks.
9. Why the compressive strength is often used as the main technical index of mortar in engineering? How to determine the strength level of mortar? What are the strength grades of masonry mortar?
Answer: The mortar mainly plays the role of transferring load in the masonry. The test proves that the bonding strength and durability of the mortar increase with the increase of the compressive strength, that is, there is a certain correlation between them, and the test method of the compressive strength is more mature, the test is simpler and more accurate, so the engineering Compressive strength is often used as the main technical index of mortar.
The strength grade of the mortar is a cubic test block with a side length of 70.7mm, under standard curing conditions (cement mixed mortar temperature 20±2℃, relative humidity 60%~80%; cement mortar temperature 20±2℃, relative humidity Under 90%), the compressive strength at 28 days of age is determined by standard test methods. The strength grades of masonry mortar are M20, M15, M10, M7.5, M5, M2.5.
10. What are the factors that affect the strength of mortar?
Answer: There are many factors that affect the strength of mortar. Experiments show that when the quality of raw materials is fixed, the strength of mortar depends on the strength of cement and the amount of cement used.
11. What are the effects of the bonding strength of masonry mortar?
Answer: The cohesive force of masonry mortar increases with its strength. The higher the mortar strength level, the greater the cohesive force. The cohesive force of mortar is related to the surface condition, cleanliness, wetness of the masonry and construction maintenance conditions. Therefore, the bricks should be watered and wetted before masonry, the water content should be controlled at about 10% to 15%, and the surface should not be soiled to improve the adhesion between the mortar and the brick to ensure the quality of the masonry.
12. What basic requirements should the design of masonry mortar mix ratio meet?
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 ≮1900kgm3; cement mixed mortar ≮1800 kgm3.
(2) The strength and durability of masonry mortar should meet the design requirements.
(3) Economically reasonable, the amount of cement and admixture should be less.
13. What are the applications of masonry mortar in engineering?
Answer: Cement mortar is suitable for masonry in wet environment and with high strength requirements; cement lime mortar is suitable for masonry in dry environment; the wall of multi-storey houses is generally made of cement lime mortar with strength class M5 ; Brick columns, brick arches, reinforced brick lintels, etc. generally use cement mortar with strength class M5~M10; brick foundation generally use cement mortar not less than M5; low-rise houses or bungalows can use lime mortar; simple houses can use lime Clay mortar.
14. What are the requirements for plastering mortar?
Answer: The surface mortar is required to have good workability, and it is easy to spread into a uniform and thin layer for easy construction. It should also have a high cohesive force, and the mortar layer should be able to adhere firmly to the bottom surface without cracking or falling off for a long time. It should be in a humid environment or vulnerable to external forces (such as ground, wall skirt, etc.), and should also have high water resistance and strength.
15. What are the functions of ordinary plastering mortar?
Answer: The function of ordinary plastering mortar is mainly to protect the wall and ground from the erosion of wind, rain and harmful impurities, improve the performance of moisture resistance, corrosion resistance, weathering resistance and increase durability; at the same time, the building can achieve a smooth, clean and beautiful surface effect.
16. What is the surface mortar? According to the different functions of the surface mortar, which types can it be divided into?
Answer: The mortar applied on the surface of a building or building component is collectively referred to as mortar. According to the different functions of the surface mortar, the surface mortar can be divided into ordinary surface mortar, decorative mortar and surface mortar with some special functions (such as waterproof mortar, thermal insulation mortar, sound-absorbing mortar, acid-resistant mortar, etc.).
17. Ordinary plastering mortar is usually divided into several layers. What are the different roles and requirements of each layer of mortar?
Answer: The ordinary plastering mortar is usually divided into two or three layers for construction. Each layer of mortar has different requirements, so the mortar selected for each layer is also different. Generally, the bottom mortar plays the role of bonding the base layer. The mortar should have good workability and high adhesion. Therefore, the water retention of the bottom mortar is better, otherwise the water will be easily absorbed by the base material and affect the adhesion of the mortar. The rough surface of the base layer is conducive to the bonding with the mortar. The middle layer plastering is mainly for leveling, and sometimes it can be omitted. The surface layer plastering is mainly for smooth and beautiful appearance, so fine sand should be selected.
18. How to choose the bottom plastering of brick walls, slatted walls or slatted ceilings, concrete walls, etc. and places where it is easy to collide or wet?
Answer: For the plastering of the bottom layer of the brick wall, lime mortar is used; for the plastering of the slat wall or slat ceiling, the mixed mortar or lime mortar is used; for the concrete wall, beam, column, roof and other bottom layer, the mixed mortar is used. , Mortar or lime mortar.
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