It is very important to take measures to prevent common quality problems in construction projects. Only by preventing them before they happen can we achieve better results. It is even more important to do every detail well while achieving the expected results. Zhongda Consulting would like to introduce to you the measures to prevent common quality problems in construction projects.
1. Earthwork:
(1) Backfill soil should be sampled from each layer to measure the dry bulk density after compaction according to regulations. Only one layer of backfill soil can be backfilled after meeting the design or specification requirements. .
(2) Strictly control the thickness of each layer of backfill, and prohibit vehicles from unloading soil directly into the trench.
(3) Strictly selecting the quality of backfill soil, controlling the moisture content, and the number of compaction passes are important links in preventing backfill soil from sinking.
(4) The corners of mechanical tamping and the junctions between walls and floors and scattered water should be carefully tamped, and fine-grained soil should be used to backfill.
(5). Filling construction should not be carried out during heavy rain. If construction is necessary, it should be completed in sections as soon as possible, and fillers such as gravel soil, sand, and stone chips should be used. There should be rainproof and drainage facilities on site to prevent ground water from flowing into the pit (trough).
2. Formwork project:
(1) Before installing the formwork, check the quality of the formwork. If it does not meet the quality standards, it shall not be put into use.
(2) Beam formwork
Common phenomenon:
The beam body is not straight. The bottom of the beam is uneven and deflected. Beam side mold blasting. Part of the formwork is embedded between columns and beams, making removal difficult.
Preventive and control measures:
A. When setting up the formwork, the principle of covering the bottom formwork with the side formwork should be followed. The cutting size at the connection between the beam formwork and the column formwork should generally be slightly shortened.
B. Beam formwork measurement must have a presser foot plate, diagonal brace, and guy wire to nail the beam sides. The beam bottom formwork is arched according to regulations.
C. Before concrete pouring, the formwork should be fully poured with water.
(3) Column formwork:
Common problems:
Exploded formwork, bulging cross-section size, grout leakage, loose concrete, or honeycomb pockmarks , deflection, column distortion.
Preventive and control measures:
A. Nail firmly according to the specified distance between columns and hoops.
B. When erecting formwork for rows of columns, the column formwork at both ends should be erected first. After the alignment and positioning are correct, the long line should be pulled through the top, and then the middle column formwork should be erected.
C. The surrounding diagonal supports should be firm.
(4) Slab formwork
Common problems:
The middle part of the slab is deflected and the concrete surface at the bottom of the slab is uneven.
Prevention measures:
A. The thickness of the floor formwork should be consistent, the joist wood should have sufficient strength and stiffness, and the joist surface should be flat.
B. The support roof must meet the specified guarantee project requirements.
C. The formwork is arched according to regulations.
3. Steel bar engineering:
(1). Steel bar processing:
A. The cutting and cutting dimensions of the steel bars are not accurate, depending on the location and location of the structural steel bars. Determine the error after cutting the steel bar and determine whether to adjust or rework it.
B. The formed dimensions of the steel bars are inaccurate, the stirrups are skewed, and the shape error exceeds the allowable value of the quality standard: Grade I steel bars can only be re-straightened and bent once, and other grade steel bars should not be re-straightened and bent repeatedly. bending.
(2). Steel bar binding and installation
A. The outer dimensions of the steel frame are inaccurate: it is advisable to align the ends of multiple steel bars when tying to prevent a certain number of steel bars from deviating from the regulations. The position and frame are twisted and bent.
B. The thickness of the mortar pads of the protective layer should be accurate, and the spacing between the pads should be appropriate. Otherwise, cracks will appear on the flat cantilever plate and the ribs will be exposed on the bottom and column sides of the beam.
C. When hoisting the steel frame into the mold, it should be stable. The steel frame should be lifted with a "shoulder pole". The lifting point should be predetermined according to the shape of the frame. The intersection points of the steel bars of the frame should be tied firmly and welded firmly if necessary.
D. After the steel frame is tied, there will be a diagonal side. The iron wires should be tied into a figure-eight shape when tying. When tying the left and right ports, it was discovered that stirrups were missing. If the spacing is wrong, adjust it in time.
E. Column stirrup joints are not staggered and should be checked before tying; check again after tying is completed. Any errors should be corrected immediately.
F. When pouring concrete, if the position of the steel bar is displaced due to lateral pressure, adjust it in time.
G. The number of steel bar joints of the same cross-section exceeds the specification: Before the skeleton is bound, the number of steel bar butt welding joints must be checked. If it exceeds the specification, adjustments must be made before binding. Avoid common quality problems in flash welding projects
(3), butt welding
Surface burns, joint axis offset and bending, poor joint bonding, joint oxidation defects, and joint over-burning defects , quenching embrittlement in the heat affected zone and cracks in the joint area.
(4). Arc welding:
A. During the welding process, the slag should be cleaned in time, the surface of the weld should be smooth and flat, the smooth transition of the weld should be strengthened, and the arc crater should be filled.
B. According to the steel bar grade, diameter, joint form and welding position, select the appropriate electrode diameter and welding current to ensure good fusion between the weld and the steel bar.
C. The size of the bars, the angle of the groove, the gap between the steel bar ends and the steel bar axis should comply with the relevant regulations to ensure that the weld size meets the requirements.
D. The welding ground wire should be in good contact with the steel bars to prevent the steel bars from being burned due to arcing.
E. When arc welding steel bars, the structural deformation caused by welding cannot be ignored. The following measures should be taken:
①. Symmetrical welding,
②. Carry out welding in turns in layers,
③. Choose a reasonable welding sequence.
(5) Electroslag pressure welding:
A. During the entire welding process, it is necessary to accurately grasp the welding power-on time and closely monitor the slag-making working voltage and electroslag working voltage. changes, and the upper steel bar is raised or lowered according to the changes in the welding working voltage, so that the welding working voltage is stabilized within the parameter range. When pressing the steel bar, maintain the pressure for a few seconds before releasing the joystick to avoid deflection of the joint or poor jointing. When welding the knots, measures should be taken to straighten the upper ends of the steel bars immediately to prevent dislocation of the upper and lower steel bars and deformation of the clamps. When the steel bar welding is completed, check immediately whether the steel bars are straight. If it is not straight, immediately straighten the steel bar while it is still in the thermoplastic state, and then remove the clamp after a slight delay of 1 to 2 minutes.
B. The electroslag pressure welding welding process is suitable for the welding of Class I and Class II steel bars with a diameter of 16~40mm. Other varieties can be used. When welding steel bars of specified specifications, the parameters of the welding process should be tested. It can be used after identification.
C. The flux must be stored properly to avoid moisture deterioration.
D. Welding working voltage and welding time are two important parameters. Parameters must not be changed at will during construction, otherwise the welding quality will be seriously affected.
E. Joint eccentricity and tilt: The main reason is that the end of the steel bar is twisted and not straight, and the clamp is incorrectly or tilted in the clamp; the clamp is relaxed prematurely after welding, and the joint is not cooled, causing the upper steel bar to tilt; the clamp Long-term use and wear may cause the upper and lower parts to become inconsistent.
F. Undercut: mainly occurs in steel bars. The main reason is that the current during welding is too high and the steel bar melts too fast; the end of the upper steel bar is not pressed into the molten pool, or the depth is not enough, the machine is stopped too late, and the power-on time is too long.
G. Not fused: The main reason is that during the welding process, the upper steel bar is lifted too high or the downward feeding speed is too slow, the end of the steel bar is poorly melted or an arc breaks; the welding current is too small or the power-on time is not enough. , so that the end of the steel bar failed to obtain the appropriate amount of melt, the equipment malfunctioned during the welding process, the upper steel bar got stuck, and could not be pressed down in time.
H. Uneven welding packets: There are two situations in welding packets. One is that the welding packets formed by the extruded molten metal are very uneven. One side is larger and the other is smaller. The height of the smaller side is less than 2mm. , the other is the uneven thickness of the weld formed on the end face of the steel bar. The main reason is that the end of the steel bar is tilted too much and the amount of melting is insufficient. The molten metal is unevenly distributed around the connection during top pressing or the iron wire ball is placed incorrectly and deviates to one side when iron wire is used to start the arc.
I. Porosity: The main reason is that the flux is damp, a large amount of gas is generated during the welding process and penetrates into the molten pool, the steel bars are severely corroded or the surface is not clean.
J. Burns on the surface of steel bars: The main reason is that the ends of the steel bars are severely corroded and the rust is not removed before welding; the clamp electrodes are not clean; the steel bars are not clamped and slippage occurs during pressing.
K. Slag inclusion: The main reason is that the power-on time is short, the upper steel bar is pressed before forming a convex surface during the melting process, and the slag cannot be discharged; the welding current is too large or too small; after the flux melts The shape hRft9 slag has a high viscosity and is not easy to flow. The top pressure is too small. Gases penetrate into the melting pool during the melting process of the upper steel bars. The steel bars are severely corroded or the surface is not clean.
L. Poor forming: The main reason is that the welding current is large, the power-on time is short, and the upper steel bar melts more. If the force is too strong when pressing, the end of the upper steel bar is pressed into the molten pool more and is extruded. The molten metal is easy to turn up; during the welding process, the flux leaks, and the molten iron loses its restraint and flows downstream with the flux leakage.
4. Concrete engineering:
(1) Concrete pouring:
A. Honeycomb
Cause: Inadequate vibration Or vibration leakage; too large gaps in the formwork lead to loss of cement slurry, dense steel bars or excessively large stones.
Precautions: Use and move vibrators as directed. When pouring again after a pause, the old and new joints should be carefully vibrated. Before installing the formwork, the surface of the formwork and the glue at the joints of the formwork should be cleaned to ensure tight joints. If the joint width exceeds 2.5mm, it should be filled. If the beam reinforcement is too dense, the corresponding gravel particle size should be selected.
B. Exposed bars
Cause: Insufficient protective layer pads for the main bars, causing the steel bars to be close to the formwork; the vibration is not solid.
Preventive measures: The thickness of the steel bar pads must comply with the thickness of the protective layer specified in the design; the pads should be placed at appropriate intervals. When the diameter of the steel bars is small, the spacing between the pads should be closer to reduce the deflection of the steel bars; use a vibrator It is necessary to wait until the air bubbles in the concrete are completely eliminated before moving.
C. Pockmarked surface
Causes: The surface of the template is not smooth; the template is not moist enough; the isolation agent is missed.
Preventive measures: The formwork should be flat and smooth. The slurry should be cleaned before installation and fully coated with isolation agent. The formwork should be watered and moistened before pouring.
D. Holes
Cause: In the denser parts of the steel bars, the concrete is stuck or vibrates.
Preventive measures: Parts with dense steel bars (such as beam-column joints) should be cut in batches to reduce the thickness of layered vibration; use vibrators in accordance with regulations.
E. Gaps and slag inclusions
Cause: The construction joints were not cleaned and grouted as required, especially the column heads and ladder feet.
Preventive measures: Before pouring, re-check the column heads, construction joints, ladder feet and other parts, and clean up debris, sediment and sawdust.
F. Defects at the bottom of wall columns (rotten feet)
Cause: The gap at the bottom of the formwork is not tight, resulting in leakage of cement mortar; or insufficient cement mortar of more than 50mm thickness is not poured before pouring. .
Preventive measures: Formwork gaps with a width exceeding 2.5mm should be filled tightly, especially to prevent side panels from hanging; pour 50~100mm thick cement mortar before pouring concrete.
G. The cross-sectional size deviation at the beam-column nodes (joints) is too large
Reason: The stiffness of the column head formwork is poor, or the column head formwork is installed at the last stage of the floor formwork installation. Yin, lack of quality control and supervision.
Preventive measures: Before installing the beam-slab formwork, install the beam-column joint formwork first, and check its cross-sectional size, verticality, and stiffness. The beam formwork is allowed to be connected only if it meets the requirements.
H. The flatness of the floor surface is poor
Cause: no mop board or scraper was used to smooth the surface after vibrating; there is no mold positioning that meets the size of the falling and sloping water parts; People are walking and working on the concrete before it has reached final setting.
Preventive measures: When pouring the floor, it is recommended to use a mop or scraper to smooth it. The leveling should be straight, the thickness meets the requirements and the mold is positioned; only when the concrete reaches 1.2Mpa is it allowed to be placed on the concrete surface. operate.
I. Displacement of foundation axis, displacement of screw holes and embedded parts
Causes: weak template support, improper fixation of embedded parts, and collision during pouring.
Preventive measures: The concrete foundation is a thick and large component, and the formwork support system must be fully considered; when the concrete is pounded to the bottom of the screw hole, double-line inspection must be carried out and corrected in time. When pouring concrete, materials should be cut evenly around the screw holes, and important embedded bolts should be fixed with steel frames. Second pouring if necessary.
J. Irregular cracks on the concrete surface
Causes: Generally, watering and maintenance are not timely, insufficient moisture, water evaporates too quickly or the temperature difference of thick and large components shrinks, and relevant regulations are not implemented .
Preventive measures: Carry out water spray maintenance immediately after the concrete is finally set; cover it with sacks, straw bags, etc. in high temperature or dry weather to keep the components moist for a long time. For thick and large components, refer to the relevant regulations for large-volume concrete construction.
K. Missing edges and corners
Causes: inaccurate feeding, uneven mixing, local low strength; or the formwork is removed too early or the formwork is removed improperly.
Preventive measures: Designate a dedicated person to monitor the feeding, and measure the feeding accurately; the mixing time should be sufficient; the formwork should be removed only when the strength of the concrete ensures that its surface and edges will not be damaged when the formwork is removed. The edges and corners of components should be protected during dismantling.
L. The reinforced protective layer pad is brittle and cracked
Cause: The strength of the pad is lower than the strength of the component; the impact force is too large when the steel cage is placed.
Preventive measures: The strength of the cushion block shall not be lower than the strength of the component, and it shall be able to withstand the impact force when the steel bars are placed; when supporting the beam reinforcement of the master, steel bars or iron wires shall be added to the cushion blocks for reinforcement; After the pads are made, they should be watered and cured.
M. When the strength of the column concrete is higher than the strength of the beam-slab concrete, steel mesh or wooden boards should be positioned around the beam-column joints as shown in the figure, and the beam-column joints should be poured first, and then the beam-slab concrete should be poured.
N. The measurement is inaccurate. Sand, stone, cement (including bulk cement and water) are not measured or measured inaccurately: the admixtures are not operated according to the procedures, resulting in a decrease in the quality of the concrete.
O. For components with steps, you should wait until the lower step pouring layer has settled before continuing to pour the upper layer of concrete to prevent mortar from emerging from under the hanging lever and causing root rot.
P. Pads should be used when pouring cantilever beams to ensure the correct position of the steel bars.
Q. Treatment of concrete defects
①. Pockmarked surface: First rinse the surface with clean water and then smooth it with 1:2 or 1:2.5 cement mortar.
②. Honeycomb and exposed reinforcement: First remove the loose and weak concrete around the holes, then clean them with pressure water or a wire brush. Use 1:2 or 1:2.5 cement mortar for small honeycomb holes. Flat compaction, large honeycomb exposed ribs are processed according to holes.
③. Holes: Chisel out the loose and weak concrete, clean it with pressure water or a wire brush. After setting the formwork, tamp it with high-grade concrete and apply pure water epoxy cement slurry on the surface for sealing treatment; cracks are relatively small In severe cases, buried pipe pressure grouting can be used.
R. It is strictly prohibited to step on the steel bars and ensure that the steel bar configuration meets the design requirements.
(2). Production and transportation of ready-mixed concrete:
A. If rainwater affects the moisture content of sand and stone, the tester should be notified in time for testing and the mix ratio should be adjusted. .
B. Frequently check whether the automatic metering system for admixtures and admixtures is in normal working condition.
C. Before unloading the concrete mixer truck, check whether the mixture in the mixer is evenly mixed.
D. When the slump of the concrete mixer truck randomly inspected at the on-site delivery location exceeds the allowable deviation value, it should be dealt with promptly.
E. Before unloading the concrete mixer truck, the retarding time specified in the mixing ratio has been exceeded and should be dealt with in time.
F. The speed of the mixer truck should be based on the loading of the mixing station. Different requirements such as mixing and unloading or the requirements of the mixer truck product manual require rotation to ensure product quality.
G. Before starting the mixer truck, the mixing drum should be wetted with water, and the accumulated water should be drained before loading.
(3). Pumping concrete:
A. The straight pipe arrangement of the concrete transportation pipeline should be straight, the pipe joints should be dense and without leakage, and the anchorage at the turning position should be firm and reliable. .
B. The distance between the concrete pump and the vertical upward pipe should be greater than 10m to offset the reverse falling impulse and ensure that the vibration of the pump is not directly transmitted to the vertical pipe. A shut-off valve should be installed at the root of the vertical pipe to prevent When the pump is stopped, the concrete in the upper pipe flows back to generate negative pressure.
C. When pumping downwards, the slump of concrete should be appropriately reduced. There should be a section of horizontal pipes and curved pipes in front of the concrete pump before turning downwards. And the vertical downward installation method should be avoided to prevent segregation and air mixing, which is detrimental to pressure feeding.
D. The location where the pipeline passes must be flat, and the pipeline should be secured with brackets or wooden pads, etc., and must not be connected to the formwork. If the steel bars are in contact with each other, reinforcement measures should be taken if they are placed on scaffolding.
E. When vertical pipes pass through each floor, they should be anchored with wooden beams or embedded bolts.
F. For newly connected pipelines during construction, debris in the pipes should be removed first, and the pipe walls should be lubricated with water or cement mortar.
G. Minimize the number of transfers of the distributor. Please remove the concrete mixture from the pipe before each transfer.
H. When pouring concrete with a distributor, avoid direct impact on the side formwork.
I. The vertical upward pipes and the initial concrete delivery pipes close to the concrete pump should be new pipes or pipes with less wear.
J. When using ready-mixed concrete, if the slump loss is found to be too large (more than 2cm), with the consent of the on-site tester, cement slurry with the same water-cement ratio as the concrete can be added to the mixer truck. Or cement mortar with the same proportion as concrete can be discharged into the pump after being fully stirred. It is strictly prohibited to add water to the storage hopper or mixer truck.
K. The pause time during pumping should generally not exceed 60 minutes. Otherwise, pipe cleaning or self-mixing concrete must be added to ensure continuous operation of the pump.
L. Before unloading the mixer truck, it must be stirred at the mixing speed for a period of time before it can be discharged into the hopper. If it is found that the first concrete mixture has many stones and less cement slurry, appropriate mortar should be added and mixed well before pumping.
M. The initially pumped mortar should be evenly distributed on the larger working surface and cannot be poured in one place.
N. If ready-mixed concrete is supplied off-site, cement with the same proportion as the concrete must be properly reserved on-site in order to make mortar or mix a small amount of concrete by yourself.
O. During the pumping process, pump start records and mechanical operation records must be kept. Record the pressure of the pressure gauge, record the pipe plug and its treatment, record the amount of concrete pumped, and record the cleaning. Maintenance records must be kept during maintenance. When ready-mixed concrete is used for burial, slump spot check records must be kept.
5. Masonry engineering:
(1) Wall axis displacement. Cause: During the masonry operation, the relationship between the axis and the edge of the masonry was not checked, and the hanging alignment line was too long and failed to meet the requirements of straight and consistent light.
(2). The thickness of horizontal gray seams is uneven. Causes: The elevations of vertical skin poles (or horizontal lines drawn on frame columns) are inconsistent, each mortar joint is unevenly controlled when laying bricks at the corners, and the brick laying alignment is not tightened.
(3). There are gaps in the wall. Causes: The length and width dimensions of the bricks have large errors. There was no actual measurement and selection before laying. When laying the bricks, the vertical joints were not arranged evenly, or the window position was not led out so that the vertical joints of the bricks should be as close as possible to the edge of the window. During the masonry operation, it was not noticed that the center line of the D-bricks must coincide with the center line of the lower strip bricks, causing the D-bricks to wander and the upper and lower vertical joints to be misaligned; there was no vertical joints at intervals of 2m or so along the wall. Use a supporting board to hang the straight spring line upward and extend it as a benchmark to control the seam movement of the player.
(4). The elevation difference between the same brick layer is one brick thickness. Cause: Before masonry, due to the excessive elevation deviation of the top surface of the foundation or the floor surface, it was not leveled and straightened, and the skin number rod could not match the brick layer; during masonry, the skin number of the bricks was not controlled according to the skin number rod.
(5). The wall is rough. Causes: Concentrated use of half-end bricks during masonry resulted in open joints, and a large deviation in straightness on the back of a one-brick thick wall; the gray stains (tongue ash) that overflowed the wall were not scraped smoothly.
(6). The structural columns are not built according to the specifications. Cause: The side brick wall of the structural column was not built into a horse-toothed structure, the tie bars were not set up, and the first step back from the column foot was not done; when the tooth depth was 120mm, the top edge was not pressed in 60mm and then the top edge was added. 120mm; the dust, bricks and debris that fell into the structural columns were not cleaned up.
(7), The top of the wall and the beam. Cracks appear at the bottom joint of the board. Cause: During masonry, the connection between the top of the wall bowl and the bottom of the beam plate was not tightly packed with side bricks or vertical bricks at an angle (60°).
6. Floor engineering:
(1) Cement mortar surface layer.
A. Sanding and blistering:
The reasons are: poor cement quality (expired or dampened to the point of reduced strength), uneven mixing of cement mortar, too fine sand or The mud content is too large, the water-cement ratio is too large, the number of calendering passes is insufficient, the calendering is too early or too late, improper maintenance, etc. therefore.
Raw materials must pass the test before they can be used; strictly control the water-cement ratio, and the consistency of the cement mortar used for the ground surface layer should not be greater than 5cm (based on the standard cone sinking degree); master the calendering time of the surface layer. The cement floor should generally be calendered no less than three times. The first pass should be carried out as the cement is laid. The second pass of calendering should be completed after the initial setting and before the final setting. The third pass is mainly to eliminate scratches and block fine pores. It should also be avoided after the final setting of the cement. It takes a lot of continuous curing. On 7 days and nights.
B. Hollowing (shelling) of the surface layer:
The reasons are: the sand particles are too fine, the water-cement ratio is too large, the base layer is not cleaned cleanly, the surface of the base layer is not moist enough or the surface area is not enough Water, plain cement slurry cannot be used to make surface mortar as soon as it is swept. Therefore, before the construction of the surface cement mortar, the bottom layer should be strictly treated (clean, smooth, and moist), and the quality of raw materials should be paid attention to. The plain cement mortar should be closely matched with the surface layer, and it should be strictly done as it is brushed and laid.
(2) Floor tile surface layer:
A. Hollowing of the fabric and base layer: Mainly due to the base layer not being clean enough and moist enough; the cement slurry being applied unevenly or the bonding layer After being left for too long after completion, the blocks were not sprinkled with water to moisten them when laying them; the glazed tiles and cement flower-step tiles were not soaked in water and moistened before being laid; the ceramic mosaic tiles were not soaked in water with a brush to remove the dust on the surface before being laid; cement paste Uneven application, etc.
B. Wrong stitching: The fabrics are of different sizes and specifications, and they are not carefully selected and classified for use in advance; when laying, the thread hanging standards are not carefully followed and the stitching is not aligned.
C. The two adjacent boards are uneven (large notch): due to the unevenness of the block material itself: improper paving operation; people walking and trampling or stacking items too early after paving (sometimes loosening occurs) ).
7. Decoration works:
(1). General plastering:
A. Plastering space on door and window openings, walls, skirting boards, and wall skirts. The main reasons for drums and cracks are as follows:
①. The dust on both sides of the door and window frames is not tight, the distance between the embedded wooden bricks in the wall is too large or the wooden bricks are loose, and the doors and windows are vibrated by the door and window switches. Hollows and cracks occur around the frame. Attention should be paid to the work of plugging the door and window frames, and a dedicated person should be responsible for plugging the cracks.
②. The base layer is not cleaned or handled improperly, and the wall surface is not watered through. After plastering, the moisture in the mortar is quickly absorbed by the base layer (or bottom ash). It should be carefully cleaned and watered in advance.
③. The base deviation is large, the plastering is too thick at one time, and the dry shrinkage rate is large. It should be leveled in layers, and the thickness of each pass should be 7~9mm.
④. If the quality of the prepared mortar and raw materials is poor or improperly used, the required mortar should be prepared according to different base layers, and the management of the use of raw materials should be strengthened.
B. The plaster surface layer is blistered and has smears. Flowering (explosive gray boy). The main reasons are as follows:
A. After the surface layer of plaster is applied, the mortar is calendered before it absorbs water, resulting in bubbling. It is more common when the base layer is concrete.
①. The bottom ash is too dry and not watered thoroughly. After the top layer of ash is applied, the water is quickly absorbed by the bottom layer, so there is no time to calender, so smear marks remain.
② When making lime paste, excessively large ash particles and impurities are not filtered well, and the maturation time of the lime paste is short. After plastering, it continues to absorb moisture and mature, causing the volume to expand, causing blooming (explosion of ash) on the plastered surface.
C. The plastered surface is uneven, and the yin and yang angles are not vertical or square. The main reason is that the vertical lifting before plastering, the square setting and the punching of the mortar piers are not careful, or the interval after punching is too short or too long, causing the punching ribs to be damaged and the surface to be uneven; the punching ribs and the plastering layer shrink differently, so There are uneven levels, and the yin and yang angles are not vertical or square.
D. The gray stains on door and window openings, walls, skirting boards, dados and other surfaces are obvious or the colors are inconsistent. It is mainly caused by leaving construction joints at will during operation. Construction joints should be left as far as possible at dividing bars, inner corners or edges of door and window frames.
E. The thickness of the skirting board, cement dado and window sill board is inconsistent, and the top edge is burred and the corners are not square, etc. The main reason is that the operation is not careful. When the wall is plastered, the lower part close to the skirting board is uneven and has a large concave and convex deviation. Or the skirting board and other constructions are not straightened by pulling wires, and after plastering, the upper part is not leveled and calendered with a ruler.
F. The pipes are unevenly plastered. The main reason is that the work is not careful and meticulous, and there is no layering, leveling and calendering.
(2) Glazed tile project:
A. Hollow: The base layer is not clean enough; when applying primer, the base layer is not kept moist; the tiles are not soaked before laying. Or the foundation is gray but not kept moist; the cement applied on the back of the facing bricks is not even enough or the amount is insufficient; the mortar mix ratio is inaccurate, the consistency is not well controlled, the sand content in the mortar is too large, the pasting mortar is not full, and the joints of the facing bricks are not tight. Cause hollow drum.
B. Dirty walls: Mainly because the walls were not cleaned in time after the paving was completed, cement paste was used to adhere the bricks, and excess white cement slurry was not thoroughly cleaned when wiping joints. At this time, the cotton yarn can be scrubbed with dilute hydrochloric acid and 20% water, and then rinsed with clean water.
(3). Latex paint project:
A. Transparent bottom: The reason is that the coating is thin. Therefore, in addition to paying attention to not leaking the brush when applying latex paint, the latex should also be kept Do not add too much water to the consistency of the paint. Sometimes when sanding paper is worn through, it will show through.
B. The joints are obvious: When painting, brush up and down. The last row of pens follows the previous row of pens. If the interval is longer, it is easier to see the joints. Therefore, when painting a large area, There should be enough personnel to connect with each other.
C. The brushing pattern is obvious: the consistency of the latex paint should be moderate, the amount of paint dipped in the brush should be appropriate, and the brushing pattern should be smooth and smooth to prevent the brushing pattern from being too large.
D. When brushing the color separation line, draw the pink line carefully before construction, use even force, lift and fall lightly, dip the brush in an appropriate amount of paint, and brush from top to bottom or from left to right.
E. When applying colored latex paint, the ingredients should be appropriate to ensure that the same batch of paint is used for each independent surface and is used up at one time to ensure consistent color.
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