RU2793557C1 - Method for control of compressive strength of hardened masonry solutions - Google Patents

Abstract

FIELD: construction of buildings.

SUBSTANCE: non-destructive methods for quality control of mortar in brick and stone structures. Invention can be used to determine the brand of mortar in load-bearing and enclosing structures of buildings. The structure is cleaned of plaster at a section exceeding dimensions of the device by 5 cm. For each type of mortar joint, the required number of screw-type elements is set, in which the number of screw-type metal elements for homogeneous masonry sections is at least 15 pieces. A leading hole is drilled without impact with a power tool, in which the diameter of the leading hole drill is at least 5 mm, and the hole is drilled without impact. The screw-type elements 100 mm long are installed to a depth of 40 mm by the impact method, while the length of the console for the grip must be at least 50 mm. After the screw-type elements are installed, the elements are pulled out of the brick seam with the measurement of the pulling force, and the compressive strength of the solution is calculated by the formula. The compressive strength of the solution is calculated as the arithmetic mean of the test results for at least five samples.

EFFECT: accurate determination of the compressive strength of the hardened mortar in the joints of brick and stone buildings.

5 cl, 4 dwg

Description

Technical field

The invention relates to non-destructive methods for quality control of mortar in brick and stone structures and can be used to determine the brand of mortar in load-bearing and enclosing structures of buildings.

State of the art

A known method for determining the strength of concrete (patent No. 2247352, published 27.02.2005, bull. No. 6), which relates to non-destructive methods of quality control of concrete. A hole is drilled in the concrete body, an annular groove is cut in the concrete body coaxially with the hole, a metal cylindrical clip is placed in it, an anchor head is fixed in the hole, which is pressed in until the sample is destroyed. Strength is determined by the formula.

, где

, Where

R - strength of concrete, MPa;

N - breaking force, N;

d - sample diameter, m;

H - sample height, m.

A known method for determining the strength of concrete (patent No. 2486488, published 06/27/2013, Bulletin No. 18), which relates to the determination of the mechanical properties of building materials, in particular strength. The method is used both in the intermediate control of products at the stage of formation of physical and mechanical properties, and in the examination of the structures of already constructed buildings and structures. A method for determining the strength of concrete by a non-destructive method according to a predetermined dependence is that drops of liquid are applied to the surface of the object under test. Next, the wetting angles of the samples θ are measured. Then a graph of the functional dependence cosθ-1=f(1/σ _w ), where σ _w is the surface tension of the liquid, is determined, the tangent of the slope of this functional dependence is determined, and the strength of concrete samples is calculated from the previously constructed dependence.

Known methods for non-destructive assessment of the strength of the solution include methods of plastic deformation, elastic rebound, ultrasonic method, wave impact method, and others. The elastic rebound method is based on the relationship between the strength of concrete and the rebound value of the striker from the surface of the concrete (or the impactor pressed against it). Pendulum-type devices (Schmidt sclerometer) should be referred to elastic rebound devices. The shock pulse method is based on the relationship between the strength of concrete and the impact energy and its change at the moment of impact of the striker with the concrete surface. The essence of the method is to estimate the loss of impact energy of the striker and its subsequent conversion by an electromechanical converter into an instrument reading. The method allows to determine low strength readings (for example, plaster mortar), but requires 10-15 samples for one strength measurement to have a flat area with a diameter of about 7-10 cm, which is not always feasible when determining the strength of the mortar in the joints of reconstructed buildings.

Ultrasonic methods use surface testers that are versatile in their application, but their range of sensitivity does not cover the full range of brands of solutions. In addition, the readings of the device may be influenced by the material of the substrate or the material of the masonry.

A known method of non-destructive determination of the strength of concrete using a reference hammer Kashkarov. The method is based on the relationship between the strength of concrete R and the value of the indirect characteristic of the strength of concrete H, defined as the ratio of the diameter of the imprint on concrete to the diameter of the imprint on a reference steel rod.

A significant disadvantage of non-destructive methods is that the surface layer of the solution is evaluated, while the strength can differ significantly along the thickness of the structure.

A known method for determining the strength of the solution according to the test results of samples - cubes with a size of 70.7×70.7×70.7 mm in laboratory conditions on stationary equipment. A destructive, time-consuming method that is applicable for determining the strength of a masonry mortar for newly erected buildings, but is unacceptable for determining the compressive strength of a hardened mortar in existing buildings. It is used in the construction of buildings and masonry work.

A known method for determining the strength of the hardened mortar in the seams of reconstructed buildings, which involves sawing bream from the mortar joints of finished structures, gluing them and subsequent compression tests in the laboratory. The method is time-consuming, laborious, expensive equipment is used and does not allow to accurately determine the strength of the hardened solution.

The proposed method for controlling the compressive strength of hardened mortars of masonry is mechanical, non-destructive and allows you to determine the brand of mortar at the site.

The technical result when using the proposed method is the accurate determination of the compressive strength of the hardened mortar in the seams of brick and stone buildings.

The method for controlling the compressive strength of hardened masonry mortars requires special equipment and methods. The method does not lead to the destruction of structures, is easy to use, allows you to determine the strength of the solution in the body of the masonry, does not require preparation of the surface of the joints before testing.

The essence of the invention

The definition is carried out as follows.

1. The design, in which it is supposed to determine the strength of hardened mortars, is cleaned of plaster in an area that exceeds the dimensions of the device by 5 cm.

2. For each type of mortar joint, the required number of screw-type elements is established. The number of screw-type metal elements for homogeneous masonry sections is at least 15 pieces.

3. Mortar joints are cleaned with a metal brush.

4. Drill the leading hole without hitting it with the power tool. The drill diameter of the leading hole is 5 mm. Hole drilling is carried out without impact.

5. The screw-type elements 100 mm long are installed to a depth of 40 mm by the impact method, while the length of the console for the grip must be at least 50 mm.

6. After the elements of the auger type are installed, the elements are pulled out of the masonry seam with the measurement of the pulling force.

7. The compressive strength of the solution is calculated by the formula

, где

, Where

R is the strength of the solution, N/mm ² ;

F - pulling force of a screw-type metal element, N;

K* - dimensionless coefficient;

d is the diameter of the screw type element, mm;

l - embedment depth of the screw type element, mm.

*for new solutions it is determined according to the technical documentation of the manufacturer of the solution; for reconstructed buildings K=0.3.

8. The compressive strength of the solution is calculated as the arithmetic mean of the test results of five samples.

Brief description of the drawings

In FIG. 1 shows a screw-type element installed in the mortar joint of the masonry.

In FIG. 2 shows a device for pulling a screw-type element.

In FIG. 3 is a diagram of the installation of a device for testing by a non-destructive method using screw-type elements.

In FIG. 4 is an example of a calibration curve for the dependence of the mortar strength R (MPa) on the pulling force F (kN).

Implementation of the invention

For testing, commercially available devices should be used, the design of which provides for:

- support frame;

- capture;

- a mechanism that provides load supply.

It is allowed to use hydraulic and mechanical jacks, the devices of which allow you to fix the amount of force at which the connection strength is lost.

The method is based on the dependence of tangents on normal stresses. Consistent results are achieved by making a pre-drilled pilot hole.

To assess the strength of the solution, a calibration curve for the dependence of the strength of the solution on the pulling force is used.

Claims (10)

1. A method for controlling the compressive strength of hardened mortars of masonry, including a structure in which the strength of hardened mortars is determined, which is cleaned of plaster in an area exceeding the dimensions of the device by 5 cm, and for each type of mortar joint, the required number of screw-type elements is set, in which the number of screw-type metal elements for homogeneous masonry sections is at least 15 pieces, then the leading hole is drilled without hitting with a power tool, in which the diameter of the leading hole drill is at least 5 mm, and the hole is drilled without impact, then the screw elements are installed type with a length of 100 mm to a depth of 40 mm by the impact method, while the length of the console for the grip must be at least 50 mm, after installing the elements of the auger type, the elements are pulled out of the masonry seam with the measurement of the pulling force, and the compressive strength of the mortar is calculated by the formula

Where R is the strength of the solution, N / mm ² ; F is the pulling force of a screw-type metal element, N; d is the diameter of the screw type element, mm; l is the depth of embedding of the screw type element, mm; K - dimensionless coefficient for new solutions is determined according to the technical documentation of the manufacturer of the solution; for reconstructed buildings K = 0.3, while the compressive strength of the solution is calculated as the arithmetic mean of the test results of at least five samples. 2. The method according to p. 1, characterized in that the determination of the compressive strength of the hardened solution is performed using screw-type metal elements. 3. The method according to p. 1, characterized in that the determination of the strength of the hardened mortar is carried out directly in the building structures. 4. The method according to claim 1, characterized in that when determining the compressive strength of the hardened mortar, the amount of force is fixed at which the strength of the mortar joint is lost. 5. The method according to p. 1, characterized in that to assess the strength of the solution, a calibration curve is used for the dependence of the strength of the solution on the pulling force.

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