混凝土楼板开裂原因及处理方法Causes and treatment methods of con.docx

1、混凝土楼板开裂原因及处理方法Causes and treatment methods of con混凝土楼板开裂原因及处理方法（Causes and treatment methods of concrete floor cracking）Causes of cracking of concrete floor slab and processing methodResidential projects currently filled concrete floor and wall cracks are more common, according to the relevant mater

2、ials and combining the situation of my company, analysis of the causes and Countermeasures of cast-in-place concrete floor and masonry wall cracks are as follows, for reference in the work.The types of cracks in the concrete floor, the cast-in-place1. longitudinal cracks: cracks along the longitudin

3、al direction of the building, there are in the leather, down through the individual.2.: the transverse cracks in the span range of 1/3, the cracks along the building transverse direction, there are in the leather, down through the individual.The 3. corner cracks in the inclined cracks appear four co

4、rner of the room, in the majority of epithelial.4. irregular crack: crack distribution and direction are irregular.5. floor: the root of transverse cracks from crack bearing in 30cm, located in the epithelium.6. embedded along the crack direction of the wire pipe.Causes of cracks in the floor, two1.

5、 design1.1 structure design safety reserve is relatively small, insufficient reinforcement or smaller section, the beam forming poor rigidity, the overall deflection, caused by the four corners of the board crack.1.2 design of plate thickness is not enough, nor do the deflection, the overall deflect

6、ion, caused by the four corners of the board crack.The 1.3 house is long not set expansion joints, cracks in the weak link. (American Concrete Institute data suggest that concrete shrinkage and temperature deformation of two kinds of dry shrinkage deformation of each 30.48m about 19mm. shrinkage cau

7、sed by the change of temperature is 37 DEG C, the temperature change of each 30.48m contraction or extension of 19mm. Some people think longitudinal contraction 40m long floor due to hardening and freezing was 8 - 20mm.)1.4 basic design improper treatment caused by uneven settlement, so the structur

8、e to generate additional stress, resulting in floor cracks.The 1.5 floor two-way force by one-way slab reinforcement, causing cracks.2. reasons for commercial concrete2.1 water cement ratio, cement content.2.2 high performance retarder dosage is too large, not in the solidification front stone sink,

9、 produced heavy crack, often occur in the beam plate junction.2.3 gravel gradation quality is not good, not good, large amount of mud, containing large amount of powder.3, construction3.1 maintenance is not in place, the mandatory requirements of concrete curing to cover and water, now most do not c

10、over, watering can not guarantee often moist.3.2 the construction speed, bearing on early, especially brick residential floor, the day before pouring floor, second days on the brick, take the car, resulting in early concrete damage.3.3 during the cold winter.3.4 or early form removal of formwork sup

11、port system stiffness is not enough.3.5 concrete surface laitance thickness, surface strength is not enough.3.6 during the construction of concrete slab reinforcement cover is stepped on bending, stepped down, the protective layer is too thick, the decrease of bearing capacity.Three, to prevent the

12、concrete floor cracking measures1. design1.1 in the use of small diameter steel case, appropriately increasing the reinforcement ratio, the ultimate tensile strain of concrete can be improved.The 1.2 corners of the negative reinforcement two-way configuration,Unidirectional plate is also surrounded

13、by both the configuration of negative reinforcement.1.3 in the same reinforcement rate, reinforced with smaller diameter, reducing reinforcement spacing, can improve the crack resistance of cast-in-place slab.2. construction2.1 cast-in-place floor try to set expansion joints, longitudinal length of

14、expansion joint spacing of about 14m or desirable residential building a unit, located in the slab, width of 10mm, the middle of the soft materials, and continuously reinforced concrete break.2.2 steel binding to ensure uniform spacing, ensure the negative reinforcement position unchanged, pouring c

15、oncrete set Ma Road, not on the negative reinforcement.2.3 using the plate vibrator, two pressing activity, second times wiping pressure in the final setting.2.4 in the pre buried wire pipe with steel mesh, embedded pipe as far as possible along the arrangement direction of reinforcement force.2.5 b

16、y using the method of covering and watering maintenance, coverage and watering is mandatory requirements, we are only watering, no cover, water after drying can not guarantee the timely supplement, the maintenance period can not guarantee continuous concrete in wet state, not up to the effect of mai

17、ntenance should be.2.6 concrete up to 1.2MPa not, but early dismantling, or by early removing system, keep the vertical support after stripping.3, mixing station3.1 to ensure the slump of production design, to the scene found segregation to two mixing.3.2 to ensure the quality of cement and sand, en

18、sure the scientific and reasonable mix.3.3 SRA will soon be available, reducing agent in concrete mixing can reduce shrinkage cracks.Four, concrete floor cracks4.1 crack width less than 0.3mm with 6202 cement closed.4.2 crack width is greater than 0.3mm by chemical grouting, the practice is as follo

19、ws:(1): chisel chisel seam along the crack, crack cut according to the width and depth of 15 20mm V slot.(2): embedded grouting pipe along the crack direction every 50cm drilling a buried grouting nozzle, fixed by glue.(3): a closed fracture structure adhesive repeatedly scraped, and closed around t

20、he crack and crack branching.(4) air pressure test: fill seal leakage site.(5): Injection Grouting grouting grouting liquid prepared by air compressor, 0.2MPa pressure grouting, grouting mouth from one end, generally from the adjacent Grouting grouting liquid overflow mouth after stopping grouting,

21、grouting and closed mouth, in order to carry out the next filling.(6) open mouth, closed mouth filling.Cast-in-situ concrete slab; crack; control; processing: in building construction, concrete slab casting in site often vary in size, depth of the crack phenomenon, through the analysis of cracks in

22、cast-in-place concrete floor performance status, reveals the causes of cracks, and puts forward how to control the fundamental measures of prevention and treatment.One of the important problems of cracks control of reinforced concrete construction, cast-in-place concrete floor crack is one of the mo

23、st difficult problems in the construction of recognized, these cracks not only affects the appearance of the building, and the influence of the building use function, greatly reduces the durability of building structure; destruction of structural integrity, reduce the stiffness;Rebar corrosion. So h

24、ow to solve the common concrete cracks, designers and construction personnel can not be ignored. A crack, inclined crack performance: distribution in the floor of the room on the corner of the housing wall cracks, general 45o oblique, sometimes a corner two cracks appear at the same time, basically

25、to crack down through. As a seven storey frame residential building project, the total length of the structure is about 100m, equipped with two temperature joint, the side of the base for the rest of strip foundation and independent foundation slab. In about two months after the handover suddenly fo

26、und on one span column plate a turret temperature cracks 45. Cracks, from three layers to six floors each have 3, but not through the floor.The vertical and horizontal cracks: mainly for the longitudinal and transverse cracks. As a teaching building, the cast-in-place reinforced concrete floor of la

27、rge area width of 0.1 0.3mm ranging from longitudinal and transverse cracks.The surface cracks: such cracks mainly cracks in the construction process, easy control and treatment. As a project under construction, because the surface area is large, in the evening poured concrete, the morning of the se

28、cond day for watering, but before pouring back to kill, surface cracks appeared at noon, with the naked eye can identify. Effect of two reasons, concrete floor crack 1. concrete materialsThe effect of cement cement shrinkage value depends on the C3A, like SO3, gypsum content and fineness of cement e

29、tc. The contents of C3A, the fineness of fine cement shrinkage. The content of gypsum insufficient cement, has a larger contraction, while the content of SO3 on the influence of concrete shrinkage significantly.The influence of aggregate: with the increase of the content of aggregate concrete shrink

30、age decreases with the increase of aggregate elastic modulus decreases, at the same time, and increased with the increase of clay content in aggregate. In addition, in the concrete, the aggregate gradation is not very reasonable is the main factors causing cracks in concrete.The influence of concret

31、e mix ratio: including unit water, cement content, water cement ratio, sand ratio and mortar ratio. In the unit water use and dosage of cement concrete shrinkage depends, and water effects than the cement content; in water under certain conditions, shrinkage increases with the increase of the dosage

32、 of cement dry concrete, but increased in the mass ratio; under certain conditions, shrinkage increases with the increase of water cement ratio significantly increased dry concrete; mix in the same conditions, the dry shrinkage rate increases with the increase of sand concrete, but to a lesser extent.The additive type and content: the influence of mixed with chemical admixtures can make the shrinkage of concrete increases. Superplasticizer used to improve concrete workability, increase slump, superplasticizer concrete is greater than the non doped charge shortening