What is the thickness of the ready-mixed masonry mortar layer?

Construction and quality acceptance of masonry mortar in technical specification for application of ready-mixed mortar

1 general provisions

1. 1 Code for Design of Masonry Structures (GB 50003) gives the mortar design values of different blocks and different strength grades.

1.2 When the compressive strength of masonry mortar and block is quite different, that is, the elastic modulus is quite different, their deformation is inconsistent, and mortar is easy to crack. So the compressive strength of mortar should be similar to that of block.

1.3 Code for Acceptance of Construction Quality of Masonry Engineering (GB 50203) is being revised, and Table 1.3 is the revised draft referring to this code.

1.4 The moistureproof layer of foundation wall is easy to be eroded by water, so the impermeability requirements are put forward for the masonry mortar used.

1.5 The early shrinkage values of concrete perforated brick, ordinary concrete brick, lime sand brick and fly ash brick are larger. If it is used on the wall at this time, it is easy to have obvious shrinkage cracks. Therefore, it is required that the production age of brick should not be less than 28d, so that most of its early shrinkage value can be completed during this period, which is an important technical measure to prevent early cracking of wall.

1.6 Rainy days will change the wet state of the brick surface, easily form a water film on the brick surface, and also change the consistency of mortar, affecting the masonry and masonry strength, which is not suitable for construction. Cover the masonry wall to prevent rainwater from entering the mortar.

Zone 2 therapy

2. 1 If the moisture content of non-sintered products is too large, it will lead to a large shrinkage of masonry in the later period, so the moisture content should be controlled when climbing the wall.

2.2 Before laying the sintered brick, it should be watered and wetted 1d ~ 2d in advance to make the surface dry and moist, and there should be no Mingshui on the surface. The wetting degree of brick has a great influence on the construction quality of masonry. Experiments show that proper moisture content can not only improve the bonding force between brick and mortar, but also improve the shear strength of masonry, and maintain the normal growth of mortar strength and improve the compressive strength of masonry. At the same time, the appropriate moisture content can also make the mortar maintain a certain paving fluidity on the operation surface, which is convenient for construction operation and conducive to ensuring the fullness of the mortar. Therefore, it is very beneficial to ensure the mechanical properties and construction quality of brick masonry.

Many unit tests have proved that dry brick masonry will greatly reduce the shear and compressive strength of masonry, and it will also cause masonry difficulties and affect the normal growth of mortar strength. When building a brick soaked by water, it will not only make the newly built masonry unstable, but also affect the bonding force between mortar and brick.

Due to the different water absorption characteristics of various masonry bricks, such as water absorption rate, initial water absorption rate and water loss rate, and the difference of environmental humidity, the appropriate water content of bricks is also different. In order to understand and control the appropriate moisture content more clearly in construction, the appropriate moisture content of blocks should be expressed as relative moisture content, and according to the experimental research results and construction practice experience of relevant units and scholars, the appropriate relative moisture content range of sintered blocks and non-sintered blocks is specified.

2.3 Ordinary small concrete blocks have the characteristics of low water absorption rate and slow water absorption rate, so it is generally unnecessary to water the wall. Small lightweight aggregate concrete blocks have high water absorption rate and should be watered and wetted in advance.

2.4 Aerated concrete blocks have the characteristics of slow water absorption and large total water absorption, so the method of sprinkling water in advance is not suitable for aerated concrete blocks. The size deviation of aerated concrete block is small, so it can be constructed by thin mortar dry method.

3 architecture

3. 1 Thin-layer masonry mortar is often mixed with a small amount of additives, which has good water retention and bonding performance and can realize thin-layer masonry.

3.2 Ensuring the masonry quality of small block masonry can be simply summarized as six words: aligning holes, staggered joints and reverse masonry. The so-called hole alignment is to align the holes in the epithelial small pieces with the holes in the lower skin small pieces on the premise of ensuring the requirements of the upper and lower skin small pieces, so that the walls and ribs of the upper and lower skin small pieces can better transmit vertical loads and ensure the integrity and strength of the masonry. The so-called staggered joints, that is, staggered masonry (masonry) of small blocks with upper and lower skins to enhance the integrity of masonry, belong to the basic requirements of masonry technology. The so-called reverse masonry means that the bottom of small blocks is laid on the wall during production, which is convenient for laying mortar and ensuring the fullness of horizontal mortar joints. This is also the basic masonry method to determine the strength index of masonry.

3.3 Ensure the horizontal and vertical positions of the blocks.

3.4 Daily masonry height control of wall masonry aims at ensuring masonry quality and safe production.

3.5 Specify the mortar joint size and mortar plumpness of various block wall masonry to ensure the masonry quality and safe use.

3.6 The plumpness of vertical mortar joint generally has little influence on the compressive strength of masonry, but has obvious influence on the shear strength of masonry. In addition, transparent joints, blind joints and false joints will also have an adverse impact on the use function of the house. Therefore, the quality requirements of vertical mortar joint in masonry construction are stipulated accordingly to ensure the fullness of vertical mortar joint and avoid false joint, blind joint and through joint.

3.7 The change of block position will affect the bonding performance with mortar and reduce the safety of masonry.

4 Quality acceptance

4. 1 The dosage of masonry mortar is large, and the quality of ready-mixed masonry mortar is relatively stable. According to the actual use and construction progress, the acceptance batches of wet-mixed mortar and dry-mixed mortar are specified respectively.

4.2 Ready-mixed mortar is produced in a professional factory, with stable materials, accurate measurement, good mortar quality and small dispersion of strength value. The production of field mortar test blocks can be reduced appropriately, and the number of test block groups retained for each acceptance batch of ready-mixed mortar of various types and strength grades should not be less than 3 groups.

4.3 The acceptance standard of compressive strength test block is based on the revised Code for Quality Acceptance of Masonry Engineering (GB 50203). Only when the average value and minimum value of mortar in the same acceptance batch meet the specified requirements can the strength of the acceptance batch be considered qualified.

4.4 In order to reinforce the masonry whose test results of mortar block can no longer meet the design requirements, or when the engineering accident needs further analysis, the actual strength of mortar or masonry in the engineering entity should be determined.