SU771516A1 - Device for determining static shering strain - Google Patents

Description

-. one ,

The invention relates to the building materials industry and can be used to determine the static shear stress of coarse dispersed, exfoliating mixtures with 5 inclusions of various fractions, such as construction, backfill concrete, etc. To calculate the transport parameters of such mixtures, it is necessary to know their rheological properties, "O in particular static shear stress determining head loss.

To determine the shear stresses (static and limiting), devices are used in which the value of shear-15 ha is calculated by the force of pulling out the working organ, for example, the mesh, from the medium under study.

Depending on the coarse aggregate fraction, the size of 20 mesh cells is selected. The disadvantage of this device is the low accuracy of the measurements, since the particles of the mixture falling into the grid cells hang in them, distorting the results of the experiments. 25

Viscometers are also used, with coaxial cylinders, for example, a technical viscometer, A.E. Desov L2J With this device, the static shear stress with the required accuracy is measured.

It is impossible, because in the process of measurement the mixture is stratified due to vibrations.

Thus, it is impossible to carry out the determination of the static shear stress of exfoliating mixtures with large particles of solid aggregate by known devices, since these devices are designed to work with dispersed fine fraction of hydraulic mixtures.

The closest to the proposed technical condition and the achieved effect can be considered a rotational viscometer with coaxial cylinders,. installed with a relatively large gap between them. Such devices include the SNS-2 instrument, commercially available in the domestic industry, designed to measure the static shear stress of clay solutions. The device consists of a tank, a passive sensing element and a drive.

However, this device cannot be used to determine the static shear stress of coarse-grained, coarse-grained systems, since the coarse fraction remains between the walls of the cylinders, does not enter the notches of the passive sensing element, and does not actually participate in the shear resistance of one layer of the mixture relative to another.

The purpose of the invention is to improve the accuracy in measuring the static shear stress of coarsely dispersed mixtures with inclusion of fractional fractions.

This goal is achieved by the fact that the passive sensing element is made in the form of blades with the possibility of changing the internal angle between them. In this case, the distance between the blades along the chord should be at least twice the size of the largest particles of the mixture under study.

The drawing shows a device for determining a static shear stress.

It consists of a tank 1, a passive sensing element 2, a drive 3. The container is hermetically sealed with the ends of the covers 4. The passive sensitive element 2 is connected to the balancing counterweight 6 by means of an axis 5.

The test mixture is placed in the container 1, hermetically closed with the ends of the covers 4. In this case, the passive sensing element 2, located inside the container, is balanced by the counterweight 6 and occupies a fixed position. By means of drive 3, capacitance 1 begins to rotate around axis 5, the passive sensing element 2 is carried along. At the moment when a shift occurs, the counterweight 6 deflects by a maximum angle, measuring which the value of static shear stress is determined by the calibration table.

A passive sensing element, made in the form of blades, divides the test mixture into volumes located in the sectors of the element that slide relative to the layer of the mixture, which is located near the walls of the vessel.

The variable internal angle of the blades of the passive sensing element makes it possible to investigate compositions with different aggregate sizes, the change in angle proportional to the size of the aggregate grains.

To ensure measurement accuracy, it is necessary to create such conditions that a sufficient number of the largest aggregate particles enter the volume of the mixture enclosed between two adjacent passive sensitive element blades.

According to the laws of mechanics, at least two grains are traversed for this NB. Therefore, the chordal distance between the blades should satisfy the condition

, and Z- 2,0 d / wOKC /

where a is the chordal distance between the blades;

max. maximum size of the aggregate used in the mixture.

The length of the blades is selected from the same condition.

The preferred location of the device is horizontal, this removes the mixture as much as possible.

Thus, the proposed device allows the measurement of the static shear stress of coarse layered mixtures with the inclusion of various fractions, which is necessary for calculating the parameters of hydrotransport.

Claims (3)

1. A device for determining the static shear stress, containing a capacitance with a drive and a passive sensitive element, characterized in that, in order to improve the accuracy in measuring the static shear stress of coarse, exfoliating mixtures with the inclusion of different fractions, the passive sensitive element is made in the form of blades with the possibility of changing the internal angle between them. 2. A device according to claim 1, characterized in that the distance between the blades along the chord must be at least twice the size of the largest particles of the mixture under study. Sources of information taken into account in the examination 1. The USSR author's certificate LR 297904, cl. G 01 N 11/10, 1969. 2.Faypolson L.A. To the determination of the rheological characteristics of concrete mixes.-Sat. Studies on concrete and reinforced concrete, vol. V. Publishing House of the Academy of Sciences of the Latvian SSR, I960, p. 14. 3. Device SNS-2 Instructions for the operation of V / o. Mashpribor, USSR, M., (prototype). Xi- / u / i 1 g - - - - -t f f - f f f