Cause analysis and solution of cracking of the hot

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Cause analysis and solutions of cracking of small concrete hollow blocks

small concrete hollow blocks are widely used because of their advantages of high strength, light self weight, low cost, fast masonry speed, low labor intensity, and the advantages of saving land, protecting resources, reducing environmental pollution, reducing project cost, shortening construction cycle, increasing the use area of houses, etc, Small concrete hollow block buildings also have shortcomings and weaknesses, such as:

it is easy to produce wall cracks, especially in the longitudinal and transverse walls of the top floor end Bay of multi-storey residential buildings; Rainwater leakage; Thermal performance is not good compared with clay brick; Inconvenient secondary decoration, etc. Among the above problems, the main problem that seriously puzzles the design, construction, real estate and property management units is cracks

through the investigation and research of the built small concrete hollow block building, from the position and characteristics of the cracks in the wall of the small concrete hollow but the unit adopts the alumina block building imported from abroad, it is preliminarily believed that the reasons for the cracks are mainly the following:

1, the reasons of the block material itself

(1) the shrinkage of the concrete block itself, That is, the shrinkage of the colloid inside the cement cementitious material in the concrete

(2) dry shrinkage caused by evaporation of free water in concrete

(3) block is a kind of hollow wall material made of concrete for medical supplies and food packaging. It has the brittleness of concrete, and it will produce small cracks in the process of production and transportation. After being put on the wall, it will produce macro cracks on the wall under the action of external factors since this year

(4) due to the material of the block itself, the concrete needs to be shaped and cured for 28 days. At this time, the deformation of the block is about 60%, and it takes up to 3-5 years for the block deformation to be completely stable. In fact, the blocks have been delivered before the age, and the age is difficult to check and control

(5) the strength of the block itself cannot meet the requirements, the geometric dimension error is too large, and the edges and corners are missing

2. Causes of temperature difference

the linear expansion coefficient of concrete block masonry is about 10 ×, It is twice as sensitive to temperature as the solid clay brick masonry. Therefore, the effect of humidity on the plastic performance of the block wall is mainly that the sensitivity to the process of infiltration and absorption is higher than that of the brick masonry. It is easy to be deformed by temperature changes, resulting in wall cracking, and temperature causes early cracks in the wall

3. Design reasons

due to the designers' insufficient understanding of the properties of block wall materials, traditional design methods are often used in the design process, and crack prevention and anti crack measures are not taken in the structure, forming the phenomenon of "wearing new shoes and following the old road"

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