Anti-cracking and leakage prevention construction technology of autoclaved aerated concrete block wall?

What contents does the construction technology of autoclaved aerated concrete block wall crack prevention and leakage prevention specifically include? The following Zhong Da consults the bidding teacher to answer your questions for your reference.

1. Introduction

Building 1 ~ 12 # in Taishan Community is located in Fuwan Road, Fuzhou, with one underground floor and seven floors above ground, with a construction area of 25000m2.

The wall construction of this project began in September 2007, and all masonry construction was completed in June 5438+065438+ 10, and * * * the aerated concrete block was about 1500 cubic meters. In the process of construction, by strengthening on-site construction management and formulating feasible construction measures, the cracking of building walls is basically prevented and the quality of block walls is guaranteed. Up to now, no obvious cracks and leakage have been found in the whole project wall.

According to the design requirements, autoclaved aerated concrete blocks are used as the external wall materials. Block itself is a new building material, which has the characteristics of light weight, sound insulation, good thermal insulation performance and convenient construction, and meets the requirements of current energy-saving buildings. However, due to the obvious characteristics of block materials, such as excessive water absorption (up to more than 60%), poor wettability, expansion and drying shrinkage, and construction factors, some problems are easy to occur after wall construction. At present, the common problems in block construction are: mortar joint cracking, plastering layer cracking, hollowing, leakage, reduced thermal insulation and sound insulation effect, which affects the use function. In order to avoid the above problems, the whole process of masonry and plastering must be tracked and controlled.

2. Material selection control and material requirements

2. 1 material selection

(1) In order to ensure the quality, manufacturers' products with mature production technology and good curing conditions should be selected, and blocks with compressive strength of not less than 5MPa above grade 07 should be selected. The shrinkage rate of aerated concrete blocks after 5 ~ 7 days is 50% of the total shrinkage rate. It should be ensured that it will not be put into use before 28 days after it is taken out of the pot, which can greatly reduce the probability of cracks caused by drying shrinkage.

(2) Different types of cement shall not be mixed, and various aggregates, additives and water shall meet the requirements. Mortar shall be special mortar with good bonding performance, with strength grade not lower than M5 and good water retention.

2.2 material approach management

(1) Material engineers shall purchase materials 25 ~ 30 days before use as planned. And in strict accordance with the requirements of technical regulations for acceptance, unqualified block materials will not be accepted.

(2) Materials shall be piled up by classification after entering the site, and clearly marked. According to the production date, specifications and quality grades, they shall be stacked in covered places, and measures such as rainproof and drainage shall be taken to avoid collision or pollution. The stacking height should not exceed 2m, and proper ventilation spacing should be maintained when stacking, so that the blocks stacked in the middle can be dried quickly to reduce the moisture content of the upper wall of the blocks.

3. Preventive measures for construction technology

3. 1 Treatment before masonry

(1) Before construction, the building ground shall be washed clean, and the number control line and height control line of masonry shall be set out on the side of frame column and wall masonry, and the top brick position shall be reserved.

(2) Before laying 1 ~ 2 days, send someone to wet the surface of the block and masonry with water, and the water infiltration into the surface is generally 0.7 ~ 1.0 mm, and the water content of the block during laying is between 10 ~ 15%. Sprinkle water evenly to ensure that the water content of the block is basically the same, reduce the difference of expansion coefficient caused by the difference of water content and prevent the wall from cracking. Determination of moisture content of upper wall of block According to the dry density of block, three blocks (or several blocks) are randomly selected and calculated by weighing method. The water content of the test block = (wet weight-dry density)/dry density × 100%, and the average value of the sampling number is taken to compare whether it is less than 15%.

(3) After communicating with the design unit and the construction unit, the 200-mm-high plain concrete guide wall shall be poured under the foundation first, and it shall be leveled to facilitate the masonry on the horizontal plane. This can enhance the strength and impermeability of the wall and increase the durability of the house.

3.2 Masonry Construction Control

(1) Before laying, site layout. Masonry should be staggered, and the overlapping length of upper and lower skins should not be less than 150mm, and the block length should be 1/3, otherwise it will be 2? Six 700 mm long Rachel tendons. The corner of the wall and the edge of the vertical and horizontal piers should be laid at the same time, and the temporary breaks should be laid into oblique if, and the horizontal length should not be less than 2/3 of the height. C20 plain concrete window sills with a height of 200mm are used at the bottom of walls with waterproof requirements such as toilets and kitchens. Regular blocks should be selected on both sides of doors and windows, and blocks should be bitten at L-shaped joints to ensure the overall stability of masonry.

(2) In order to eliminate shrinkage cracks caused by temperature changes between the main structure and the retaining wall, Rachel reinforcement must be left at the junction of masonry and wall column, with a spacing of 500 ~ 600 mm and a specification of 2? 6. Both ends extend into the wall not less than1000 mm.. For each masonry 1.5m high, 2 Ф 6 long steel bars shall be used for Rachel to prevent shrinkage and cracking of the wall.

(3) The wall with large span or height shall be provided with constructional columns. When the wall length exceeds 5m, a reinforced concrete constructional column is set in the middle. The joint between the window sill and the wall outside the window is a place where the stress is concentrated, which is easily affected by the shrinkage of masonry and causes cracks. Therefore, the cast-in-place window sill plate is set at the window sill to resist deformation. The upper corners of doors and windows are also prone to cracks and hollowing, and ring beams are used instead of lintels to strengthen the integrity.

(4) Aerated concrete blocks with different dry densities and strength grades cannot be mixed, and aerated concrete blocks cannot be mixed with other brick blocks. Non-integral bricks at door and window openings, constructional columns and wall ends are cut and formed by toothless saws. During the masonry process, the daily masonry height shall be controlled within 1.5m, and the masonry shall be stopped in rainy days. After the joints between masonry and frame columns and shear walls are filled with mortar point by point, each side is divided into grooves with a depth of 30mm; After each 5 skin bricks are laid, the mortar joint inside and outside will be compacted with caulking trowel. Close the capillary. Pause when the building is 200mm away from the bottom of the frame beam. After 7 days, after the mortar is solidified and dried, the masonry will shrink, settle and deform to some extent, and then the top brick will be processed.

(5) Waterproof and sunshade work should be done well after masonry, and water conservation should be done properly.

(6) Before plastering construction, stick 100× 100 steel wire mesh at the junction of block wall and concrete beam and column, door window frame and internal corner. The width of each side is 200mm, the mesh is flat and firm, and it is fixed with steel nails.

3.3 Plastering process control

(1) Plastering process: setting out and leveling-door and window frames-caulking and plugging holes-embedded parts treatment-masonry surface cleaning, watering and wetting-roofing jointing-leveling by hanging vertical sleeves-scribing-framing joints and strips-detail treatment-adhesive layer-covering surface-cleaning.

(2) At the grass-roots level, cement mortar is used to roughen the wall surface, and the wall surface is drenched with water, and plastering can only be carried out after 7 days. The penetration depth of masonry wall is 8 ~ 10 mm, and the water content is between/kloc-0 ~15%. Full scraping interface agent (beneficial cement or special interface agent) is adopted. At the joint of frame column, beam and block, local hanging net can strengthen the bonding force between base and plastering layer. Due to the low strength of the aerated block, the external angle of the wall should be 1.8m high, each side should be protected by polymer cement mortar with a width of 50mm 1:2.5, and alkali-resistant grid cloth with a width of 100mm should be pasted on each side of the corner.

(3) The plastering thickness of each layer should not be too thick, and each layer should be controlled within 7 ~ 9mm. If the middle plastering is too thick, it should be smeared in layers. Mortar materials should be compatible with aerated concrete block materials, and materials with good water retention performance should be adopted. In order to prevent and reduce wall cracking, elastic putty or elastic coating is used for both internal and external walls.

4. Key technologies for preventing leakage

4. 1 Masonry shall be carried out in accordance with the specification requirements. During masonry construction, before each block is laid, clean up the floating sand (dust) on the surface of the block with a brush, and then brush the adhesive at the horizontal and vertical mortar joints after cleaning up, and brush evenly, because a slight uneven thickness may affect the mortar fullness, which must meet the construction requirements, reaching the requirements of 90% for horizontal mortar joints and 80% for vertical mortar joints. The thickness of mortar joint shall be controlled at 5 ~ 6mm, and the maximum shall not exceed 8mm. Vertical mortar joint can not have transparent joint or blind joint; Masonry walls shall be smooth and clean, and mortar joints shall be free of grout or adhesive; The upper wall of the block or the newly built block shall not be hit or moved at will. If correction is needed, the adhesive should be laid again for masonry, and leveling and smashing are not allowed. In order to avoid excessive shrinkage and deformation of masonry, the daily masonry height should be strictly controlled within1.5m..

4.2 Set Rachel bars reasonably. The most common setting method of Rachel reinforcement in autoclaved aerated concrete block wall is embedding or planting reinforcement. Masonry and reinforced concrete wall column contact, using 2? 6. Rachel reinforcement should be embedded or buried. During construction, a long slot should be opened on the horizontal mortar joint of the block in advance. After adding the reinforcement, fill it with adhesive or cement mortar M 10 until the notch is smooth. However, some construction workers adopt the construction without slotting, and directly bury the steel bar in the mortar joint of the block.

Slotted bar planting method is more convenient and has good quality. Because this method is reasonable and accurate, and the slotting embedded reinforcement is firmly bound, the problem is that slotting requires more manpower. Grooving is now a special hand saw, and the width and depth of grooving are 10mm, but attention should be paid to cleaning up the brick chips to ensure the bonding quality.

4.3 Contact points of different materials should be flexibly connected. Interface joints between infilled wall and column, wall and beam slab should be handled flexibly. According to the characteristics of autoclaved aerated concrete blocks, in order to reduce the cracks between different materials and blocks, many parts of the country require flexible treatment of the application of blocks to adapt to the changes of temperature and dry and wet environment. However, many construction workers are always used to using the traditional clay brick masonry method, such as filling walls and columns (walls) with close joints, building walls and beams with ordinary bricks or cement bricks or inclined bricks, and filling joints with ordinary cement mortar. In order to reduce the project cost, some construction units prefer to use traditional ordinary cement mortar to fill joints rather than spend money on PU foaming agent. This kind of hard connection treatment is bound to be difficult to overcome the stubborn disease of filling wall cracks.

Therefore, it is still required to deal with the interface joints flexibly: at the joint between the infilled wall and the reinforced concrete column (wall), a gap with a width of 10 ~ 15 mm and a depth of 30mm should be reserved during masonry, a PE bar should be embedded in the gap, and PU foaming agent should be used. In addition to waterproof with PU foaming agent, the gap on the outdoor side should also be closed with external wall elastic putty. There should also be a gap 10 ~ 25mm wide and 30mm deep between the infilled wall and the beam bottom or slab bottom of the upper floor, and the filling in the gap should be carried out at least 7d (preferably 14d) after the completion of wall masonry. Wedge the two sides of the middle part of each block at the top of the wall with wooden wedges that have been dried and treated with anti-corrosion, and fix them on both sides of the wooden wedge, and embed flexible connecting materials that meet the deformation requirements. From the engineering practice, using flexible connection to deal with interface cracks has greatly improved the control of cracks.

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