Concrete cracks occur for many reasons and different. These may be cracks on the degree of risk may affect the life of the building. The following classification of cracks causes rated as applicable to all facilities that are in the site or precast.
Classification of cracks:
1_ non-structural cracks (for reasons other than construction) and distinguish them:
Thermal contraction cracks:Generated during the early hardening heat resulting from chemical reaction between water and cement. And often deal with the elements Almsph-made steam STEAM CURING This heat treatment generates a large amount of heat through the concrete. When it cools and shrinks concrete interpretations thermal begin to emerge and grow, especially if cooling is through a regular item. It may happen diligence tensile thermal cracks very accurate estimates to be structurally important. But, there is weak within the concrete surfaces, and the contraction of the normal drought leads to expansion of these cracks after linking prefabricated elements.
Plastic shrinkage cracks:Occur as a result of the rapid evaporation of water from the surface of the concrete during the Dinh Tsldha. This rapid evaporation depends on many factors, mainly temperature and speed of direct sunlight makes the rate higher than the evaporation rate of water floating on the surface of the concrete.
The plastic shrinkage cracks are usually short and superficial and appear in two directions Eksien at the same time. In the case of precast elements of facilities that are made in closed places and a good deal is not feared the danger of plastic shrinkage cracks of age.
Shrinkage cracks drought DRYING SHRINKAGE CRACKINGThis type of cracks when the corresponding elements of the short-armed a few barriers hindered (as in the case of contact Kornishih with a thickness of a small slab terrace with thickness large). In the beams precast the concrete parties articular dumped into streams of links Mtsaldh prefabricated (template). Due to the narrowness of the sewage is relatively easier for the casting process, and occur in the vertical joints are often a result of shrinkage cracks minutes.
Differences in thermal stress DEFFERENTIAL THERMAL STRAINS:The method of construction in precast facilities help to vulnerable depending on the temperature difference as a result of weather or natural heating STEAM CURIG. Therefore, cracks appear in the seas is confined at the connection is solid and Jhiaa origin. The sudden temperature effect last born, where the sudden rise in temperature is also a series of cracks if there is a significant difference in temperature between the sides of the slab or beam. This effect is rare in a residential installation. But may occur at certain facilities, such as the walls of reservoirs and in special cases when the liquid inside the stock tank hot or too cold. Stresses occur as a result of origin the temperature difference between the different Odzih, for example, the parties to the interface exposed to direct sunlight Vtaatmdd, while the temperature remains low the rest of origin, thereby creating the appearance of cracks in the corners of the country flooring installations very long or very strong. There are other types of cracks may occur under this influence, especially with a noise and vibration, and reduce the cracks resulting from shrinkage and temperature differences of the strength of origin, this means that the jurisprudence does not increase after the occurrence of cracks.Cracks as a result of corrosion:There are two main types of defects help to increase the impact of erosion on the concrete origin, namely:
Rebar corrosion:Growing and growing rust on the steel product cracks along the length. This may lead to the fall of the concrete exposing reinforcing steel and helps calcium chlorides, based in the concrete appearance of this defect, it also helps moisture saturated salt in coastal areas with calcium chloride, and therefore the seriousness of corrosion of iron becomes large in this case. The corrosion of iron serious cracks on the age of origin and where the bear reduce the area of iron in the concrete sector, and this phenomenon is particularly serious in the pre-stressed concrete.
Erosion of concrete:There are chemical reactions lead to the breakdown of the concrete and the most common case is to configure all the result of the Union ETTRINGIT aluminate cement with sulfur in the presence of water. And the resulting salt with a larger size of its constituent elements, and the resulting expansion cracks lead to the eruption and the collapse of parts of the concrete Almthtkh.
May appear as a result of a chemical imbalance choice granules (gravel) is appropriate, the bumps and holes that appear on the surface of the concrete means that the granules isolated had fragmented.Structural cracks:Reinforced concrete exposed to the jurisprudence of tensile load at the origin, and therefore spoke of cracks in the beams (and this is normal) in the side to grab the exhibition under the influence of bending moment.If the user arms distributed properly (individualize iron) and were of good quality concrete, these cracks are sufficiently accurate to avoid the corrosion of iron. Generally, these cracks are acceptable if the thickness of 0.2 mm has proven to be corrosion and rust are increasing rapidly only when the rift than the thickness of 0.4 mm.
Has been showing some cracks as a result of the jurisprudence of storytelling, though rare, are cracks country (slash) in the direction of bars reinforcement (Altkchrist) and occur due to defects in conjunction bars of iron with a large diameter with concrete, especially if the cover of iron a few fish, or if Jnc short rods, which lead to a weak link between the bars of iron, concrete, or if the cracks in the reasonable limits and refers to the behavior of a natural origin there is no danger of it, but in some cases, this phenomenon of degree cracks pose a threatSuch as:
Cracks bending moments or shear increasingly wide an ongoing basis.Cracks occur in parts of the concrete before the pressure and this points out that there is an unusual behavior occurs in origin.Disintegration of concrete in the pressure areas (columns or beams or slabs in the side exposed to the pressure) and this situation of extreme danger to the origin.When these types of cracks may be necessary to strengthen the origin and still loads of Foix, and then examines the basis and source of the imbalance in the origin, and we begin to solve the problem of strengthening of origin and how to address the cracks.
May be caused by an increase in load imbalance on the origin, or that the reinforcement is
Enough, or that the concrete quality is poor or there is a decline in soil ... ... etc..
Maintenance and repair cracks in structures:
Monitor the cracksIt should be noted when cracks appear in the concrete of origin and when it should test the thickness of the crack length and depth.
It is important to note whether the chasm expands over time or not. There are many ways this study uses (such as the use of patches of plaster over the cracks and a follow-up cracks in plaster, or using a device that measures the width between the two balls of iron fixed on both sides of the divide. (
The measure must distort or bend the elements of origin that occur in structural cracks using the reference points of known elevations of the measurement (it is necessary to know the final landing of the foundations) will lead us Ahz observation and various readings to know what type of cracks in terms of their causes. And often affect a number of reasons at one time.
Now possible to propose a method for treatment (restoration) strengthening of origin for example, or injection of cracks ... ... and so on.
Address the cracks and restoration of origin:
Capillary non-structural cracks (caused by reasons other than construction)Supposed in this case that the concrete of good quality, accurate, and that the cracks are detrimental to the continuity of bearing arms. If has been examined the cracks, and were caused by the natural behavior of the building as in the case of links between units Precast, For the designer to take these cracks in the account, in particular links the vertical and horizontal face of the building, which should be handled carefully to avoid damage caused by the cracks (such as water leaks through them). And therefore should expect that in the feminization of the interior walls. And usually is performed laboratory tests on links Musharuchh to get the real strength of the joints in the case of actual use, and must be designed rebar and choose the uniqueness widening cracks in such a manner is dangerous. It is often put additional iron is calculated structurally necessary (such as rebar Almaxh country) and is perpendicular to the direction of the expected cracks in the corners of the building.
In general, good design and good implementation gives us better control in the cracks. And address the non-structural cracks poetry (such as plastic shrinkage cracks) metal brush to clean the surface, and then addicted to cracks on the layers of cement slurry injection adhesive?. When the noodles are deep and cracks perpendicular to the direction of the forces of pressure in the origin it is necessary to inject the cracks carefully using products that are thermally hardened. It is necessary to choose the managing low-viscosity
Wide cracksWhen the width of a large and deep rift within the concrete so that up to arms must be addressed to avoid the corrosion of iron. If this happened corrosion in iron really should remove the cover concrete envelope of iron, clean the bars of iron, and replaces the lid removed concrete of a good cover for Iron (It is important to j this case the use of eucalyptol colloidal adhesives and repair concrete of high resistance to pay the air using the gun cement CEMENT GUN) and is often characterized by cracks caused by concrete expansion of its proximity to the high proportion of sulfate. It may be necessary in this case, remove the concrete Almaabh and changed. If the cracks due to mechanical reasons (such as increasing the loads or lack of reinforcement or the use of concrete is poor or falling soil) must make sure that control of these reasons before starting the restoration of the building, especially if the cracks continue to increase.
It may be necessary to remove and change the concrete Almaabh and add a layer of new concrete, for example (we get to link concrete the old concrete using new layer of paint, special glue elastic or using epoxy adhesive EPOXYDE GLUE. It may be necessary to develop rods rebar additional streams or holes engraved in the old concrete (grown using iron mortar Epoxy adhesives) and the injection of cracks when we decide you should care Allzoj choose the product that will be used according to the order and distribution of cracks, according to the results of the injection.
If the cracks are active and the display changes as a result of thermal effects must be to make sure you do not see the impact of tensile stresses and cracks after the filling of new cracks.
Treatment of fractures using flexible materialsHere will Ntaul solutions and problems filling cracks with concrete follow-up other necessary repairs.
Materials used:Using organic polymers and cement in the treatment of cracks and will refer to the links. And more organic polymers used in the structural repairs are links Epoxy. It is a basic compound or resin EPOXY BINDERS, tempered or accelerated hardening, where the mixing proportions must be specified. Links and Epoxy property Alatsaq Kkhersana ores, iron, and lack of the recession, as they are of tensile strength and pressure highs. The disadvantage of organic polymers weak resistance to fire and high temperatures. Epoxy Tantmte and links to the thermal hardening type polymers and include within the composition Albulirthan equipped in the form of two compounds mix them when in use and is the polyester of the same species. It usually consists of three vehicles
(Based on resin, broker assistant, and hardening accelerator).
There is another faction of the organic ties consist of polymers of plastic THERMOPLASTIC POLYMERS or links acrylic ACRYLAMID BINDER a quick sclerosis not stick to concrete, which are shrinking high in dry conditions and so the main use is to bridge the cracks in the cases of humidity and saturation of the leakage resistance of the water and cement used here is Ordinary Portland cement, and cement a little deflation and quick-setting cement can mix them with organic polymers.
Selection of raw materialsCement injections used (Allbani) to fill the voids and Altashecat important, and rapid hardening cement is used in some cases are used to fill cracks and Alpolamaat plastic (resin seminary), mainly to fill the cracks under the pressure of the water to stop the water permeable. Also used Oadaalpolamrat thermal hardening.
Reduction of the capacity of cracks:
Can avoid the arrival of cracks in reinforced concrete elements to limit unauthorized taking
Heavy use of concrete as possible.Ensure sufficient layer of concrete to protect reinforcing steel against corrosion, including not less than 2 cm in the tiles before the effects of air, and 2.5 cm for the beams and columns, that not less than the thickness of this layer for the largest diameter of the reinforcing steel user.