Cracks in the concrete Part 1

Cracks in the concrete Part 1

The cracks in the concrete of the most important elements that give a clear indication on the state of origin, they vary according to their seriousness and their impact on facilities and the duration of its appearance and vary in terms of breadth, depth and degree of impact on the origin.Therefore, the scientists divided cracks, according to several criteria, including:- By type of cracks and their impact on the Origin:1 - minor cracks.2 - serious cracks.- Or according to their nature:1) Self-cracks: the result of plastic shrinkage or landing Owaltqls early or drought.2) Foreign cracks: due to increased payloads or misuse of the building or the poor implementation or poor design or non-use of materials in conformity with the specifications.- Or, as the causes of cracks:1 - non-structural cracks.2 - Structural cracks.- Or, as the hardening of concrete:1 - cracks before hardening.2 - cracks after hardening.And other criteria that all agree that the phenomenon of cracking in the concrete is a dangerous phenomenon must be studied to see as soon as possible or prevention of the occurrence and then deal with what appeared, in order to avoid problems before they occur.• the causes of cracks:1 - plastic shrinkage cracking:Produces mainly due to rapid dehydration as a result of exposure surfaces to air currents, leading to severe water evaporates, a much higher degree than the rate of bleeding in the water out of concrete and the resulting strain leads to stress cracks.2 - plastic cracks down:Occurs when there is a high rate of bleeding and landing after the completion of the casting and rolling and finishing where it continues to increase the density of concrete self-as long as it is in the case plastic and when hampered this movement or be constrained by reinforcing or Alkovraj or otherwise lead to cracks adjacent to the elements impeding the movement where cracks appear over the reinforcing rods fixed in the form of reinforcement and curvature appear at the confluence of the column prizes.3 - Early thermal contraction cracks:Generated during the hardening process of early heat resulting from chemical reaction between cement and water are often generated a large amount of heat and temperature of concrete more Its frequency for ambient temperature, especially in the elements of the huge, and after a few days does not exceed / 10 / days down the rate of heat generation to less than the rate of loss (to the low degree of interaction) exerting downward pressure on concrete temperature to ambient temperature, during which changes in the temperature of the concrete hindered the movement of contraction resulting from the low temperature and are generated as a result of that tension stresses cause cracks.And these stresses commensurate with the amount of change in temperature coefficient of thermal expansion and modulus of elasticity and the degree of disability movement.4 - shrinkage cracking resulting from the drought:Show contraction when exposed structural elements of small arms to prevent this shrinkage through some structural installation.5 - web cracks (fissures cancer):Result from the stresses of tensile strength against the surface as a result of obvious differences in the amount of water surface from those available in the class of the lower (internal) and is not linked to time, but circumstances of extreme weather such as low relative humidity, the type of Alkovraj, and the amount of cement in the mixture, the method of shaking for Bethune, which sometimes leads to a surface layer is smooth and rich with water.6 - cracks due to reinforcement corrosion:Which result from oxidation of iron due to ambient moisture or water leakage from water pipes or increase the proportion of chlorides or Mixed Concrete carbon shift of Foreign Affairs or cracks as a result of reasons other than rust, which facilitates access to moisture and begin reinforcing rust.7 - cracks due to interaction of Alkali Aggregate:It is produced from the interaction of alkalis with silica that appear when the cement hydration and source of the alkali metal salts is either in cement or in the addenda or to use ground water or sea water or cladding materials they contain.8 - cracks caused by the interaction of concrete with sulphate:Result from the use of water containing sulfate soluble or soil containing sulfate, and when the leak of these materials to the concrete and reacts with aluminate hydrated calcium interacts with them composed aluminate calcium sulfate is accompanied by a significant increase in size lead to stress strain localized high cause corrosion of concrete and cracking with time.9 - Structural cracks:9-1 - cracks due to design errors:Produce these errors to some or all of the following reasons:A - Failure to follow the requirements of standards and rules applied to the design and implementation of concrete (such as concrete mix design).B - Choose a phrase that is appropriate for construction.C - computational errors.D - The use of arm is not enough.E - neglecting the impact of thermal stresses.And - neglecting the impact of restrictions on the movement of members exposed to the volumetric changes.G - Neglect of rebar details and places of abating and distributed and the differences in diameter and lack of attention to the details of iron and iron link between the elements and iron in the horizontal and the use of different iron in the same item.H - the lack of data or failure to clarify the places expansion joints and contraction and the value of the concrete cover and the lack of places breaks down and you do not specify locations breaks casting.I - errors caused by erroneous movement of loads and weights on the origin or not taking into account some loads such as wind and earthquakes.J - not taking the impact of stress concentration into account, especially at the corners of the Interior.K - poor choice of foundations suitable for soil-borne origin.For - not to account for the overall decline is expected under the foundations and compared to the limits allowed by the quality of the soil.M - Non-Henajat strong attention to the design of the foundations of the Association and especially to the foundations of which are located next to existing installations.N - neglect of the circumstances surrounding the site that may affect the design such as the level and quality of the foundations of nearby buildings and the forthcoming change in the level of groundwater.9-2 - cracks due to errors of implementation:1 - Lack of attention to detail given to the adoption of plans and engineer the port on his own experience and personal.2 - not care to read the notes and warnings on the charts.3 - Do not connect the engineer designed to clarify some technical aspects of others and clear diagrams.4 - Do not follow the amendments and the successive stages of design and its amendments.5 - Not aware of and familiar with the port engineer specifications and technical conditions for implementation of the subject of origin.6 - volume is not suitable for the materials, either concrete or gravel, sand or additions.7 - do not examine the constituent materials for concrete so as to indicate their conformity with standard specifications.8 - the use of rebar or steel it greases and oils or clay or other components that lead to lack of cohesion with the concrete after casting.9 - Aggregate use of non-progressive and non-identical with the percentages of mix design or contain impurities such as salts or organic materials or soft materials are many.10 - Expired term use of cement or cement does not suit the nature of the weather conditions surrounding the origin or does not fit and the quality of salt in the soil, directly adjacent to the foundations.11 - the use of water is not suitable for mixing, such as sea water or ground water containing salts or acids or harmful use of water more than the allowable limit.12 - the presence of defects in the concrete cover in terms of strength and poise and dimensions and non-Nvaveth and is falling, leading to a decline during and after the pouring of concrete.13 - lack of proper calibration of the materials used.14 - defects in the casting method of hand mixing, transport or shaking, or treatment or the use of excessive amounts of water or too much in the work of shaking and not to take the necessary protection for concrete in conditions of heat drought and strong winds or freezing or under water or jaw early Couvraj before the arrival of concrete resistance appropriate to the load and so on.15 - neglecting to do the implementation of the necessary laboratory tests to make sure the quality of the concrete, such as compression set resistance and the degree of absorption or rate of compaction or interoperability.16 - Errors modified iron in terms of types or diameters of iron and not to put in its places and spaces correct the specific schemes and composition and lengths and the appropriate extension with the installation of a good iron supply and Almaxh and Atari.17 - shook the iron after doubt concrete primary and shook the bars especially the columns leading to the fall of Atari and accumulation in the bottom of the column spacing, or for the prescribed limits, which affects the efficiency of the column.18 - do not leave enough distance between the iron and wooden Alkovraj to get the proper coverage according to the type of item and its own specifications.19 - not to put chairs under the rebar Alborndat (nails), leading to the fall of the iron during casting top to bottom and the lack of iron in the areas of tension.20 - not to put links of iron in the right place and the specific lengths and a sufficient number of iron and with the same diameter.21 - lack of attention to the implementation of the casting breaks in places not subjected to high forces and stresses and not afraid to surface cohesion at the follow-up casting.22 - lack of attention to the implementation of the expansion joints and landing at the facility or the structural elements are good and not care for cleanliness and dealt with according to assets, which means it will become a weak area for moisture and groundwater, affecting the long-term occurs in the reinforcing steel and cracking concrete.23 - lack of integrity of the columns, especially the necks of the columns.24 - Non-drainage water from the areas adjacent to the foundations.25 - casting on the soil are not valid contain organic material or clay.26 - lack of attention to filling material between the foundation and the use of soil containing sulfur or organic working on rebar corrosion.27 - Non-isolated foundations in the case of high water levels groundwater level foundations.28 - error in the application of the methods of delivery and mixing them, such as the implementation of the central nucleus and great heights using a sliding template example and create the building in the traditional manner (templates Basic), which leads to a relative decline is calculated.29 - error in the implementation of fit-outs that lead to the occurrence of cracks and flaws in construction, such as lack of attention to extensions of health leading to the infiltration of muddy water to the walls and foundations and their interaction with iron.30 - or break open big holes to pass the plumbing ground in dangerous places.31 - Non-implementation of the layers of insulation to moisture or water, especially the last Bishop of origin or Baloaqbip or the implementation of that is poorly matched to the technical specifications or the use of insulating material is intact.32 - lack of interest in the basements of leprosy soil well before tiling, leading to cracking of these floors and the leakage of water into the soil foundation which leads to a decline in those foundations are clustered for cracks lead to a serious origin.33 - done by pouring concrete from high altitudes, leading to the separation of its components, and thus get gaps in it (Altashecat).34 - Althver others sound by construction workers, electrical, health, and especially in columns.