FI65566C - FOERFARANDE FOER FRAMSTAELLNING AV BETONGMASSA - Google Patents

Description

, 65566

The present invention relates to a method according to the preamble of claim 1.

5 When preparing the concrete mass and striving for the ideal preparation situation, the grain size distribution and moisture content of the aggregate used must be known in order to dispense the right amount of water to achieve the desired water-cement ratio on the one hand and the desired flexibility on the other.

As the grain size distribution of the aggregates changes, the flexibility of the concrete mass, i.e. the workability, also changes with a certain predetermined water-cement ratio. On the other hand, the desired water-cement ratio is difficult to achieve, 15 because it is difficult to control the current moisture content of the aggregates. The grain size distribution of aggregates and sometimes also the shape coefficients that affect workability can be measured by screening the aggregates used, but this can be done quite infrequently with respect to the frequency of use. Measurements can be performed in laboratories even on a daily basis, although this is not common, and yet moisture and grain size distribution can vary from mix batch to batch.

Moisture can be measured with expensive infrared-25 or gamma-ray meters even continuously, but no cheap and simple method for measuring grain size distribution is hardly in use. In principle, the measurement can be made by automatically taking sample batches of the aggregate used from time to time and screening them with 30 test screens. However, such test screening equipment is expensive and susceptible to interference, as well as rapid wear.

Some measurement and control methods and devices used in connection with the production of concrete mass are known from the patent literature in order to control the amount of water to be added.

DE 65566 1 683 778 discloses a method for adjusting the addition of water so that the first target value is approached first, after which the addition of water is changed until the second target value is reached. The next target value can be computationally interpolated when the mixing torque curve is known. This method assumes that the torque curve is only a function of water. This limits the applicability of the method, as the addition of water 10 can control the torque along only one of the occurring torque curves, in which case it is not possible to deviate from the curve, e.g. when new shape shapes are required.

DE-A-2 855 324 discloses a method analogous to the previous method, in which the water content of the concrete mass is monitored by monitoring the electrical conductivity of the mass. The amount of water is adjusted in the same manner as described in the above-mentioned publication.

The device 20 according to DE-A-1 9 ^ 9 441 operates by first measuring the maximum torque of the concrete mixer and the corresponding water addition, after which the target addition can be controlled to correspond to the target torque. However, as in the solutions mentioned above, this requires that the grain size distribution and shape coefficients of the aggregate 25 remain constant.

The object of the present invention is to eliminate the shortcomings of the previous measuring and control methods and to provide a simple and inexpensive method for producing concrete-30 mass.

Surprisingly, a simple method has now been invented in which, to use a mathematical language, two unknowns can be determined using a single equation.

One unknown is the moisture content of the aggregate, and the other unknown is the combined effect of the grain size distribution and shape factor of the aggregate on the workability of the concrete mass.

3,65566

The power absorbed by a saw mixer in a normal concrete mix depends firstly on the type of mixer and the size of the batch to be mixed, i.e. the mass. However, these are normally constant. In practice, the power taken by the mixer depends on the water-cement ratio and the aggregate coefficient, which here means the ratio of the aggregates and the shape factor of the aggregates.

The power taken by the mixer normally depends on the water-cement ratio, so that the power take-off starts at a certain starting point, increases as the water-cement ratio increases, reaches a maximum water-cement ratio of about 0.2 and then decreases continuously according to a certain curve. Thus, one curve or equation is obtained to solve two unknowns.

Another corresponding curve, the shape of which differs substantially from the previous one, can be obtained for the same mixer by applying, in addition to the water-cement ratio, a known concrete-20 pulp softener, metered separately. By using different amounts of plasticizer, in principle a swarm of curves is obtained, whereby the maximum of all curves is below the maximum of the water-cement ratio curve alone. More than one equation can now be selected to solve the two variables experimentally 25 or computationally.

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

The method according to the invention will now be examined in more detail by means of an exemplary embodiment according to the accompanying drawing.

Figure 1 shows graphically the power of the mixer as a function of the water-cement ratio when using different plasticizers.

Figure 2 shows graphically the power of the mixer 4 65566 as a function of the water-cement ratio when applying the method according to the invention.

In Figure 1 means

Ky clean water curve, 5 Kjj1 softener curve 1, KN2 softener curve 2, VV constant size water addition, VN standard size softener addition, VVN calculated ratio of added water 10 and softener and V / S water-cement ratio.

Denote by X the quantity of water contained in the aggregates, which is unknown, and always add to the concrete mass a constant amount of water known to be so that the peak of said curve is ignored, and measure the power where P1 * Ρκν (X + constant water addition) where P ^ y denotes the function of the water-cement ratio alone.

A constant amount of known liquefier is then added to give

Pn = Pv (X + constant water volume + constant knocker-2 Kn volume) and further P. | - Pg = P ^ j. (X + number of standard doors + number of standard switches).

25 Now two unknowns have solved two unknowns. All of these curves with a given mixer and a given grade and quantity of cement can be measured in advance, and put into either mathematical or tabular form.

The power P 1 corresponding to the final flexibility can be calculated on the basis of the above, when the curves for water and the notch are known. In this case, the desired flexibility (power P 2) and the desired water-cement ratio can be reached simultaneously, e.g. in Figure 2 a value of 0.1 + 0.

35 This means that there is no dispersion in the workability or in the strength of the concrete 5 65566 other than that resulting from the power measurement error.

Eliminating dispersion is of great economic importance.

5 The curve shown in Figure 2 moves with the addition of water. Point Y is reached by adding a "pure anhydrous plasticizer". Point Z, in turn, is reached by adding a plasticizer.

The fact that it is practically not possible to move directly in the direction of the 10-point Y is due to the fact that the plasticizers are usually dispensed as aqueous solutions, so that a little water always enters the system with the plasticizer. As a result, the area A is the area in which it can be operated freely, whereas in the past it has only been possible to operate only either along the curve Ky or using stiffeners only along the lines parallel to the straight flock Z "- Z. Neither method has previously to the desired point 1. but there has always been scattering.If the machinability has been 20 constants sought, then there has been scattering in strength (V / S ratio) .In order for this scattering not to cause under-strengths, an overdose has always had to be applied to the cement, which in practice means 10-20% too much cement.

Claims (2)

6 65566 Claim: A method for producing a concrete mass by feeding cement, aggregates, water, plasticizers and other auxiliaries and mixers to a known mixer equipped with a power meter, the power being read after the addition of water and plasticizer, characterized in that a constant amount of water is added to the mix and the first power after feeding, then a constant amount of known plasticizer is added to the mixture and the second power is read after feeding, and the amount of additional water, the amount of plasticizer or the amount of water and plasticizer required to reach the final target point is calculated using empirical formulas and / or diagrams known per se. 20 Patenting: For use in the manufacture of concrete mass, the color of the effect of which is mixed with the cement, the stem material, the wadding, the flywheel and the 25-hour weight and the tillage, the color effect of the flywheel, the effect of constant blending is constant on the watten and the effect is constant after up to 30 times, after which the effect is constant on the fly and the effect is constant on the shape of the shelf, and then the value of up to 35 or a curved system of the upper part of the plunger of the plunger is shown at the bottom of the plunger, the plunger and the plunger.