Design compressive strength of concrete v25. Concrete protective layer. Regulatory data for calculations of reinforced concrete structures

Table 6 shows the regressions and the values \u200b\u200bof the obtained correlation coefficients. Note that the correlation coefficients obtained satisfactory values, i.e. values \u200b\u200bclose to the value. It has been verified that, as expected, the regressions are nearly parallel to each other and create families of curves depending on the bar diameter. It is observed that all obtained slope coefficients are always positive, i.e. for all rod diameters, a tendency of noticeable behavior is observed, characterized by an increase in the maximum adhesion tension in proportion to an increase in the axial compressive strength of concrete, in the tested resistance range.

Statistical analysis showed that the maximum bond stress depends on the change in the diameter of the bar, the composition and age of the concrete. When analyzing the correlations, it can be concluded that the increase in the maximum adhesion tension is proportional to the increase in the compressive strength of concrete, however, observing the features of the tests, as it turned out at the beginning of this work.

It is believed that the introduction of this type of fast adhesion test in addition to or even an alternative compression test method traditionally used in civil engineering can significantly improve work quality control, allowing concrete quality control to be carried out in a shorter time, quickly and safely, "in the locomotive." ...

There is a strong and clear relationship between these variables if other factors, such as the diameter of the rods, are kept constant. Research includes not only experimental activities, but also numerical simulations to identify simplified and reliable ways to conduct the test on construction sites.

Aspects studied include the format and preparation of the test form, as well as the procedure for pulling the plate. Bond's weirdness is a state of the art. Concrete dosage and control manual. Concrete Structures - Basic Scaffolding Principles reinforced concrete structures.

Quality control of building concretes: test for adhesion of steel and concrete. Compressive strength assessment based on wire tie tests for in-situ quality control of concrete. Bond strength and rib geometry: a comparative study of the effect of deformation patterns on bond strength.

Analysis of the effect of changes in the geometry of reinforcement on the bond strength in the push-out test. Facing deformed rebars to concrete: effects on the retention and strength of concrete. The dissertation for the degree of candidate of historical sciences Paulist, Ilha Solteyr.

Β is the angle of inclination of the angle. And - the distance between the maximum heights of the ribs. Ø is the diameter of the steel bar. Durability depending on exposure to rain. Fire resistance, which considers the blocks, on the one hand, as non-combustible, and on the other hand, that the walls must guarantee the following functions for a certain period of time: fire resistance, flame cut and fire cut.

In addition, they must be covered and must not be intruded. The concrete block is widely used in Brazil. This was the first block on which the Brazilian standard for calculating structural masonry. On the other hand, since there are many suppliers, it has a lack of quality problem. High resistance is only available in some factories, and the block is heavier. In Brazil, there are already more than 20 floors with structural concrete blocks. For other assemblies, the concrete block wall serves structural and enclosing functions by eliminating posts and beams and reducing the use of reinforcement and molds.

The block must ensure the quality and economy of buildings. This means that it must represent adequate size and shape, compactness, strength, good geometric finish, good appearance, especially when the project does not prevent coating. In addition, it must guarantee thermoacoustic insulation. These parameters are decisive for the quality of the blocks and have their limits set in the relevant technical standards.

Some characteristics constitute regulatory requirements and serve as quality indicators or to indicate blocks. The compactness depends on the dosage criteria and directly affects the strength of the block, as well as the absorption rate. Resistance is the ability of the masonry wall to withstand various mechanical actions provided for in the structure, such as loads on the structure, wind, deformations, impacts, etc. this resistance is directly related to several factors, such as: characteristics of components and joints, adhesion of the assembly, flexibility of the wall, connection between walls, and others.

It is directly related to the impermeability of the products, the unexpected addition of weight and saturated wall and durability. The absorption index is used as a measure of durability. The individual absorption of concrete blocks must be less than or equal to 10%.

The initial absorption corresponds to the suction capacity of the block. This absorption depends on the porosity of the blocks, which are higher for more porous blocks. Therefore, it is important to find the equilibrium point, as absorption at the correct value promotes the penetration of binders, which, when cured, make the block, mortar and coating solid together. However, when the absorption is too great, it can jeopardize the chemical reactions required for hardening. It is important to use a solution with adequate retention properties to ensure balance.

Dimensional accuracy and geometric perfection

The quality and type of the concrete block are fundamental to the good performance of the structural system. Therefore, it is important to know whether the region has enterprises blocking manufacturers that offer the corresponding product and within technical standards... The manufacturing process gives products more regularity in shape and size, allowing work to be modulated from the project itself, avoiding improvisation and the usual waste resulting from this. It is important to respect the dimensions specified in the standard, as well as their tolerance limits.

If leaking, also observe the thickness of the walls that make up the blocks so as not to compromise their strength. The standardized block sizes admit the tolerances shown in the table. If discrepancies are found in the block sizes, this means, in general, a failure in the production process, that is: during the manufacture or checking of lots. Dimensional accuracy issues directly affect modular coordination and contribute to increased block waste.

The blocks must be uniform, compact and sharp. They must be free of cracks, fractures, so as not to impair their seating, strength and durability. Surface texture is important in bare masonry, where the block is a finish, or in coated masonry, where it must have a roughness, texture and surface porosity suitable for adhesion with mortar and contributing to overall solidity. In general, texture ranges from smooth to fine depending on the materials used and the manufacturing conditions.

Block types and their classification

Concrete blocks can be different types and forms. The type of aggregate is one of the differentiation factors, being normal or light. The blocks have a variable modular shape, which, in general, must meet the requirements of processing and applicability, that is, the mass must be such that the block is processed.

Brazilian standardization basically defines two types of concrete blocks, depending on their application: for fencing, a simple concrete block for masonry without a structural function and with a structural function - a single concrete block for structural masonry. Regardless of the application, the block must be leaked, that is, no bottom. In this material, only blocks with a structured function are considered.

Hollow block, i.e. without a bottom, allows the use of holes for the passage of installations and for the application of gravity. The Brazilian standard makes the designation of blocks by width. The table shows the classification of building blocks. That is, the length of the blocks is always a multiple of the width, which avoids the use of compensating elements, with the exception of adjusting the window frames. Compensating elements are required not only to adjust the window frames, but also to compensate for low-level modulation.

The mooring process is used when joining the walls, without the need to fractionate whole blocks. Compensation blocks are used for this process. In addition to the common block, a semi-interlocked block is also produced, which allows masonry with a mooring connection without having to cut the block in operation.

Concrete blocks can be with or without a bottom. Bottomless blocks make it easy to pass piping, hydraulic pipes through the interior, without the need for cutting into brickwork... Blocks, by definition, serve to lift walls and have a charge transfer function. For this, one of its most important properties is compression resistance. Block resistance classes represent the breaking strength of blocks calculated on the shaft section of the block. Within the class, eighty percent of the blocks must have a compressive strength equal to or greater than this value, and the result must not be less than 90% of the class value.

The determination of the characteristic strength is calculated as follows.






The values \u200b\u200bof the individual compressive strength test results are as follows.







Compression resistance is a fundamental property of structural blocks precisely because of their function and also because durability, water absorption and wall tightness are closely related to this property.