FI101646B - Method for determining the workability or consistency of plastic concrete in a compulsory mixer - Google Patents

Description

101646

The invention relates to a method according to the preamble of claim 1 for determining the workability or flexibility of a plastic concrete in a forced bonding machine.

With the rapid development of concrete technology, increasing demands have been placed on concrete and its manufacturing technology. Concrete production has increasingly become a fully automated process. Controlling the workability properties of concrete has become an unsolved problem in this development so far. The significance of the problem is great, 15 because the deviations in the machinability decisively impair the average high performance and quality properties of the concrete. Good controllability of machinability also has a great effect on improving cost efficiency.

20 In traditional manual concrete production, the mill enters the mixer after dosing and visually adds the necessary additional water and achieves the most successful result in terms of flexibility and workability, even if, for example, there has been an error in dosing or. 25 changes in materials affecting water demand.

In automated concrete production, everything should happen automatically, including the determination of one of the most important properties of concrete mass, flexibility and workability.

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With the development of sensor and dosing technology, the dosing accuracy has significantly improved, as has the measurement of the moisture contained in the materials. These have improved the quality of the concrete mass and its evenness. However, it has been found that despite this, the flexibility of the concrete mass and the need for water vary widely. The reason for this is generally considered to be variations in the properties of materials used in concrete that affect water demand. These include variations in aggregate granularity 2 101646, variations in binder properties such as grinding fineness, chemical composition, and variations in power quality properties, etc. As a result, it is necessary to find a method that automatically determines the workability and flexibility properties of concrete mass This should be done in such a way that in automated production the quality of the concrete mass is uniform without additional mixing time. The mixing time must be made standardized, because as the mixing time 10 increases, the mass begins to change uncontrollably in its flexibility and workability properties. To this end, various methods, mainly based on electricity, have been made to determine the machinability during the mixing operation. These include measuring the current drawn by the mixer and measuring the electrical conductivity of the concrete mass 15 by means of sensors placed on the bottom of the mixer and calibrating the moisture and ductility dependence. However, the methods have proven to be understandably inaccurate. For example, the introduction of power reducers has changed the starting point considerably.

The object of the present invention is to obviate the shortcomings of the technique described above and to provide a completely new type of method for determining the workability of plastic concrete in a forced mixer.

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The invention is based on the fact that in the mixer the surface of the concrete to be mixed is measured by image processing methods during a periodic mixing event and the flexibility of the concrete is determined by means of the amplitude of the vertical displacement of the selected point on the concrete surface.

More specifically, the method according to the invention is characterized by what is set forth in the characterizing part of claim 1.

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The invention provides considerable advantages.

The invention provides real-time information on the ductility and workability of concrete, and thus the entire concrete production process can be reliably automated and the uniformity of the concrete ensured.

The invention will now be examined in more detail by means of exemplary embodiments according to the accompanying figures.

Figure 1 shows a traditional way of determining the workability and flexibility of concrete.

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Figure 2 shows a perspective view of a forced agitator applying the method according to the invention for determining the workability and flexibility of concrete.

Figure 3 shows graphically the behavior of concrete in the method according to the invention.

The measurement method is simplified by starting from the idea that the concrete mass in its plastic form corrugates in the same way as the mixer rotates, i.e. the point or points at which the amplitude of the plastic concrete wave is greatest can be easily determined from the mixer. In principle, one such significant point is sufficient, from which a sensor placed on the mixer cover measures the amplitude of the mass wave 25 at this point, from which the dependence on flexibility is calibrated.

According to the prior art, the flexibility of plastic concrete is determined according to concrete standards, often by a cone deflection test by filling the cone of Figure 1 in a certain way with concrete and then lifting the cone off and measuring the height difference h1-h2.

The invention measures flexibility and workability on the same 35 principles.

The forced agitator 1 according to Fig. 2 has a main shaft 6 rotated by a motor 2 with arms 4 and rotating stars 7 with mixing blades 3. These are synchronized together, i.e. with each revolution of the main shaft 6 the concrete mass receives the same mixing impulses at different points of the mixer. If the mixer is, for example, 2-stroke and the main shaft 5 rotates at a speed of 6 s / revolution, a maximum amplitude is generated every 3 seconds at a significant amplitude measurement point, which immediately tends to recover before the new access stroke generated by the star 7.

The heart rate monitor of the forced agitator 1 is in principle according to Fig. 3. The amplitudes a1 and a2 are used to determine the dependence on the flexibility and workability of the concrete mass. A larger of the amplitudes in practice means greater flexibility and machinability than with a smaller amplitude a2.

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The current high-grade concretes are power-curved and dixotropic in order to reduce the amount of water, i.e. the concrete is quite stable in size until the mass is obtained, for example, by vibration, whereby the plasticizer acts as a bearing 20 between the granules.

In the method in question, every few seconds a kind of deflection result of the determination of flexibility is obtained in the situation when the mass is in motion and thus takes into account 25 important dixotropy properties. Most of today’s even more demanding concretes are plasticized with chemical additives that lower the surface tension of concrete masses for a specified machining time.

30 Manufacturing steps in automated manufacturing: 1. Dosing on scales (material moisture measurement).

2. Dosing in mixer + base water.

35 3. Mix for approx. 1 min.

4. Adding a plasticizer.

5 101646 5. Amplitude measurement of the concrete mass according to Fig. 2 with the camera 5 and additional water or plasticizer is added by automation if the amplitude a is not large enough (step 5, approx. 1 min). Excessive amplitude 5 is corrected, if necessary, by adding dry matter.

6. Empty.

There must be 10 accurate measurements for the addition of water or softener in step 5 and an automatic alarm limit in the control system that indicates if too much extra water or softener is going. For example, a situation where an exceptional amount of water is required and the pulp is good in terms of workability and flexibility requires inspection of the other 15 components.

Adjusting the flexibility may make sense with a plasticizer, because in hardened concrete, the granules are already almost completely coated with the plasticizer, so that the addition of water does not provide as much li-20 slippage as before the plasticizer is applied. Ts. final adjustment with a plasticizer when the measurement is accurate may usually make more sense.

It is also possible that the method is so accurate that the plasticizer is dispensed in a controlled manner in an amount that results in a target amplitude.

If several paddle stars or a higher star rotation speed are used, the amplitude describing the actual flexibility may not be achieved in the graph 30 of Fig. 3. In this case, instead of measuring the amplitude, the rate of change in the height of the surface, i.e. the derivative of the function of Fig. 3, can be measured.

According to the invention, the height of the plastic concrete surface is preferably measured optically, but the movement of the surface can be measured, for example, by means of ultrasound or mechanical sensors.

Claims (8)

A method for determining the workability or consistency of plastic concrete in a composite mixer (1), wherein the surface of the concrete in the composite mixer (1) is monitored, characterized in that - the surface of the concrete is monitored in such a way that a decision on the application of additional water or diluent is taken out from a periodic level change at a selected point. Method according to claim 1, characterized in that the surface of the concrete is measured by optical methods. Method according to claim 1, characterized in that the surface of the concrete is measured by ultrasound. 20 Method according to claim 1, characterized in that the surface of the concrete is measured by a mechanical sensor. 5. A method according to claim 1, characterized in that from the amplitude (a) of the periodic level change of the selected point, the decision to supply additional water or diluent in the forced mixer (1) is made. Method according to claim 1, characterized in that from the rate of change of the periodic level change of the selected point, the decision to supply additional water or diluent in the forced mixer (1) is made. 35 Method according to claim 1, characterized in that the surface of the concrete in the forced mixer (1) is monitored by means of a 101646 row camera (5). 8. Preparation process for concrete, wherein 5 - the materials intended for mixing are portioned on roads, - the material is portioned in the mixer together with 10 base water, - the material is mixed for a predetermined time, for example about 1 minute, 15. Diluent is added after and - the mixer (1) is emptied, characterized in that - before emptying, the amplitude of the surface of the concrete mass is periodically measured at a desired point and by automation add additional water or diluent in accordance with the measured amplitude. 25