CS244351B1 - Quick binder - Google Patents

Abstract

The solution relates to a fast-setting binder and a method of producing it. The essence of the fast-setting binder is that it contains a binder with a specific surface area of over 500 m2/kg and a plasticizing additive with a significant steric effect, which reduces the surface tension of water by a maximum of 15%, in an amount of 0.01 to 10% by weight on dry matter, and preferably 0.2 to 2.5% by weight. The binder with a specific surface area of over 500 m2/kg is obtained from the scrubbers from mills for grinding conventional or dispersion cements with a plasticizing additive. Sulfonated polycondensates of phenol, melamine, naphthalene or urea with formaldehyde can be used as a plasticizing additive. The phychloasing binder can be used for work with low material consumption, with high initial strength required, for grouting and highly stressed structures.

Description

(54)

Quick-setting binder

The solution relates to a fast-setting binder and a method of producing it. The essence of the fast-setting binder is that it contains a binder with a specific surface area of over 500 m2/kg and a plasticizing additive with a significant steric effect, which reduces the surface tension of water by a maximum of 15%, in an amount of 0.01 to 10% by weight on dry matter, and preferably 0.2 to 2.5% by weight. The binder with a specific surface area of over 500 ^m2 /kg is obtained from scrubbers from mills for grinding conventional or dispersion cements with a plasticizing additive. Sulfonated polycondensates of phenol, melamine, naphthalene or urea with formaldehyde can be used as a plasticizing additive.

The phychlovaz binder can be used for work with low material consumption, with high initial strength required, for grouting and highly stressed structures.

- 1,244,351

The invention relates to a fast-setting binder, which includes very fine hydraulic and air binders.

Theoretically, the idea of using very fine binders with a high specific surface area and a high content of the finest particles is well known and attractive, as it promises a more perfect use of the binding capabilities of the binder. For example, with normal fineness of grinding of cements to specific surfaces of about 300 m^/kg, even under favorable conditions, after very long periods in hardened mixtures, approximately 50% of the weight of the cement remains unhydrated. However, the preparation of very fine cements and their processing in hydrating mixtures with favorable utility properties brings with it considerable difficulties.

Grinding cement to high specific surface areas by traditional methods appears to be uneconomical and, when a certain fineness is reached - the so-called grinding limit - impossible. Progress can be achieved by using suitable surfactants as intensifying grinding additives, for example diethyl carbonate or substances based on sodium lignosulfonate. However, this approach has been shown to be effective only on a laboratory scale or when grinding in batch mills with discontinuous operation, the productivity of which is low. When grinding in conventional tube mills, the intensifying additive is ineffective in terms of grinding fineness, since it only causes an acceleration of the flow of the grinding material through the mill, thereby reducing energy consumption, but the specific surface area remains practically unchanged. When grinding in circulating mills with a classifier, it is possible to increase the fineness of grinding by using intensifying additives, but at the cost of an almost order of magnitude reduction in performance in order to achieve substantially higher specific surfaces. Ensuring the production of very fine cement by both of the above industrial methods would require disproportionately high costs, especially investment costs. The only viable option seems to be to be satisfied with the mass production of cements of conventional or

244 3S1

- 2 not very high fineness and to obtain very fine cements only in relatively small quantities from this mass production by sorting with special sorters or by using fly ash from clinker mills or even from kilns. However, it should be noted that so far the use of fly ash from ground cement without gypsum addition and preferably with the use of surfactants, for example based on sodium lignosulfonate, has been proposed.

To achieve favorable utility properties of hardened hydrating mixtures made of very fine cements, especially high strengths and their rapid increase, acceptable shrinkage, high impermeability and others, these mixtures need to be processed with the lowest possible water content by effective means. However, such mixtures are very difficult to liquefy and require very effective means for processing, for example, activation mixing. A certain solution is possible by using surfactants as grinding and mixing agents and plasticizing additives; the disadvantage is the reduction of the surface tension of water, which causes aeration of the mixture, especially in mixtures made of very fine cement. This aeration, on the one hand, makes it difficult to liquefy the mixture at the beginning of mixing, and on the other hand, has an adverse effect on the strength and other utility properties of the hardened mixture. Help is possible at least partially by using vacuum mixing, which is, however, difficult and expensive. Another solution is to plasticize the mixture with excessive doses of surfactants, which may be present in the fine cement from the grinding stage and/or which are added during the processing stage. Although this approach does not require vacuum mixing to liquefy the mixture, the adverse effect of aeration remains. If we use large doses of substances based on sodium lignosulfonate as surfactants, it is inevitable to exclude the gypsum additive from the cement, which would precipitate the lignosulfonates. In this case, the lignosulfonate, together with another necessary additive in the form of normal or alkaline metal or alkaline earth carbonate, functions as a setting and hardening regulator. However, the effect of this regulatory system is unreliable, as both of these additives can both accelerate and slow down setting depending on the concentration and other conditions, and therefore an inversion of the effect can occur, which cannot be safely prevented even by other additives. The beneficial physicochemical effect of lignosulfonates, consisting in the possibility of reducing the amount of mixing water, is therefore nullified by their overdose due to uncertain chemical effects,

- 5,244,351 which can cause in particular premature solidification of the mixture before its processing into a mold or even in a mixer or conveyor»

Progress can be achieved by using so-called superplasticizers, which have so far been used only to increase the workability of conventional mixtures made from cement of normal fineness, i.e. around 500 m^/kg or even less. Their use has so far generally appeared uneconomical to increase the strength by reducing the water content in the mixture, which these superplasticizers make possible. Their use in the preparation of hydrating mixtures from very fine cements is not yet known.

The above-mentioned shortcomings are eliminated by a fast-setting binder, in particular an air or hydraulic mortar, according to the invention, which consists in containing a binder with a specific surface area of over 500 m^/kg and a fluidizing additive based on sulfonated polycondensate of phenol or its derivatives, sulfonated or sulfurized polycondensate of melamine or its derivatives, sulfonated or sulfurized polycondensate of naphtha, or sulfonated or sulfurized polycondensate of urea or its derivatives, with formaldehyde or polycyclic sulfonate, which has a pronounced spherical effect and reduces the surface tension of water by a maximum of 15%, in an amount of 0.01 to 10% by weight on dry matter, preferably 0.2 to 2.5% by weight.

As a binder with a specific surface area of over 500 m^/kg, it is preferable to use dust from mills for grinding conventional cements or for grinding dispersion cements with a fluidizing additive. Cement obtained by grinding with the addition of other substances, for example limestone, quartz, slag, bentonite, or their mixtures, can also be used, with the filler to binder ratio ranging from 1:1 to 10:1 by volume and the ratio of the average grain sizes of the filler to the rapid-setting binder being less than 1:2.5 and at the same time the coefficient of variation of the frequency distribution of the grain sizes of the filler being less than 50%.

The advantage of the plasticizing additives according to the invention is the fact that it does not reduce or only slightly reduces the surface tension of water, because it contains only weak surfactants, and that it does not fundamentally affect the chemical reactions taking place in the solidifying and hardening materials.

- 4 244 3S1 drying and/or hydrating mixtures. Therefore, these plasticizers can be added in relatively large doses compared to ordinary plasticizers, for example lignosulfonate ones, without undesirable effects on the course of chemical reactions. This makes it possible to significantly reduce the water coefficient while maintaining the required workability.

The main advantage of using suitable plasticizing additives for mixtures of very fine cements, prepared with the lowest possible water content, is the reliability of the regulation of hydration processes, especially setting and achieving a rapid increase in strength and other useful properties. The mixtures can be prepared primarily from cements containing gypsum, which has proven to be the most reliable regulating additive so far. If setting is very fast with very fine cement, the gypsum content can be increased. If, on the contrary, faster setting and hardening of the mixture is required, very fine cement with a reduced gypsum content can be used. Since it is practically only possible to use a fraction of fine cement from the production of ordinary cement, in the latter case the basic product of this production will be poorer in gypsum. However, this usually does not matter much with less fine cements, because their setting occurs slowly, or it is possible to extend the start of their setting by additionally mixing ground gypsum into the cement, or preferably by creating a mixed cement from Etruscan with a higher sulfate content.

The use of a plasticizer of a type suitable for hydrating mixtures of very fine cements is, however, advantageous even in cases where these cements do not contain gypsum at all and their hydration is possibly regulated in other ways. Plasticizers themselves inhibit the initial stages of cement dissolution by making it difficult for water to reach the cement grains and thus delay the start of the mixture's setting. However, this effect is limited in time, so that in later stages they do not limit the formation of cement stone ₍ and thus the increase in strength.

Since many fluidizing additives also have an intensifying effect during clinker grinding, another advantage lies in the possibility of their simultaneous use as a grinding additive, while later, when processing the hydrating mixture, this grinding additive is again used favorably.

- 5,244,351 will be used as a superplasticizer. However, the intensification effect during grinding by industrial methods cannot be expected to significantly increase the overall fineness of grinding, but only to accelerate the grinding process, save energy and possibly increase the yield of the finest particles or even increase the proportion of fine cement fractions obtained.

By removing the finest particles from the produced basic cement type according to the invention, the risk of premature setting of mixtures from this basic cement type, which exists when using intensifying additives for clinker grinding and is undesirable for the common use of cements, is eliminated or mitigated.

When clinker is ground with an increased gypsum addition, this addition is selectively ground to a higher specific surface area than the clinker and is therefore preferentially graded into the produced very fine cement, which needs an increased amount of gypsum to regulate its setting at high fineness.

To obtain even finer cements with even higher initial and final strengths and other advantageous properties for special applications, the fine fractions obtained by screening or in the form of fly ash can be further ground, either dry and/or activated, usually in a hydrating mixture by intensive stirring or vibration. In this grounding, the grinding efficiency is high, since the coarser grains are removed and therefore do not disturb the grinding process. '

The creation of a mixed binder from very fine cement and even finer inactive filler, primarily clays, especially bentonites, is of great importance for grouting work, where the relatively coarse grains of conventional cements penetrate poorly into the finest cavities and capillaries, thereby limiting the applicability of clay-cement grouting to relatively coarse-grained materials and to environments with relatively wide cracks or cavities.

The use of very fine binders with the processing method according to the invention appears to be particularly effective from an economic point of view if the very fine binder is obtained as a by-product from the production of conventional binders, either by sorting or in the form of drifts. In such a case

- 6 244 351 case, the price of this very fine binder may not be significantly higher than the price of a conventional basic product, but its quantity is relatively small. Therefore, it is possible to count on the use of mixtures of very fine binders, processed by the method according to the invention, primarily for work with low material consumption, such as various grouts with the required high strength - especially initial, as well as bonding and sealing including repairs, injection with increased requirements for the fluidity and penetration ability of the mixture and others. However, smaller-scale applications are not excluded for highly stressed elements and structures, for example for arches of large spans, for columns of very tall buildings, for prestressed concrete, for sealing curtains, for structures or protective layers in chemically aggressive environments and the like, or in cases where a rapid initial increase in strength is required, that is, especially during reconstructions, possibly to a limited extent also during winter concreting and prefabrication.

The rapid-setting binder and its production method are illustrated in the following examples.

Example 1

The possibility of preparation and some advantageous properties of the quick-setting binder of the invention were verified by an orientation test, when the dust collected during the production of Portland cement of class 400 in a cement mill showed a specific surface of 700 m2/kg according to Blaine, a residue on a 0.06 mm mesh of 5% and residues on coarser sieves of zero. From these dusts, with the addition of 0.5% sulfonated polycondensate of phenol and formaldehyde by weight per amount of binder, a mortar was prepared without any problems in accordance with ČSN 72 2117 at a mixing ratio by weight of binder:sand = 1:5, but with a reduced water coefficient v;c = 0.5¾ on a standard mixer. This mortar began to set after 50 minutes and its compressive strength after 5 days of hardening reached 62 MPa.

Example 2

The favorable properties of the quick-setting binder of the invention have been proven by standard tests according to ČSN 72 2114, 72 2115, 72 2116,

2117 and ON 72 2142. During the grinding of Portland cement of class 400, samples of dust were taken from the filters of cement mills, these samples were homogenized with the addition of dried plasticizer in an amount of 0.4% by weight and subjected to technological tests in accordance with the standards mentioned (specific surface area, density and setting, volume stability, strength, flowability). More detailed data and results of these tests are clearly compiled below:

Series Filters Specific surface Liquidating agent: sulfonated polycondensate A hose 552 ^m2 /kg phenol with formaldehyde B II 600 ^m2 /kg melamine with formaldehyde Ό electric 625 ^m2 /kg naphthalene with formaldehyde D hose 600 ^m2 /kg urea with formaldehyde Solidification volumetric stability flowability beginning end

A 1.3 hours 7.5 the hour is suitable 210 mm B 1.1 hours 8.8 hour 215 mm C 1.3 hours 5.6 hour 215 mm D 1.1 hours 7.5 hour ” 210 mm Series Fortresses in bending MPa Fortresses in pressure MPa Days 1 3 7 28 1 3 7 28 A 4.8 8.3 9.1 11.2 18.5 40.5 49.5 60.8 B 7.6 8.7 9.5 10.1 37,'9 41.5 44.5 53.5 0 6.5 '7.8 8.8 9.5 35.5 39.9 42.2 53.8 D 7.4 8.2 9.3 10.6 39.5 42.5 45.7 54.8 Example In next row exams were monitored properties which expression

They distinguish the fast-setting binder of the invention from conventional cements and from dusts without a plasticizer. Dusts obtained during the production of Portland cement class 400 from hose filters of cement mills and the aforementioned Portland cement were used for comparison. From these binders, mortars were tested with a mixing ratio of binder:sand = 1:2 and a reduced water coefficient v;c = 0.4, the other conditions were in accordance with ČSN 72 2117 and CN 72 2142. Sulfonated melamine polycondensate with formaldehyde was used as a plasticizer. More detailed data and results are again clearly compiled below:

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Binder Series

Specific surface area Liquefaction Flowability Volume stability

I PC 400 580 ^m2 /kg - 110 mm conforms II PC 400 580 ^m2 /kg 2 % mass 290 mm conforms III dusting 610 ^m2 /kg - 80 mm conforms IV dusting 610 ^m2 /kg 2 % mass 160 mm conforms in dusting 622 ^m2 /kg 2 % mass 170 mm conforms VI dusting 750 ^m2 /kg 2 % mass 185 mm conforms The Solidification Series Fortresses in bending Compressive strength beginning end MPa MPa

after 4 hours 6 hours 24 hours after 4 hours 6 hours 24 hours I 1 hour 50 minutes 9 hours immeasurable 4.1 unmeasurable 25.5 II 5 hours 30 minutes 9 hours 50 minutes 5.0 H 14.7 III 10 minutes 20 minutes 0.4 0.5 1.2 2.2 2.5 10.8 IV 50 minutes 1 hour 5 minutes 5.1 4.9 6.9 15.9 22.9 44.1 in 55 minutes 1 hour 2.4 5.7 8.9 9.4 14.5 48.1 VI 25 minutes 50 minutes 4.7 5.9 9.5 20.4 25.2 51.5 The results table shows a significant synergistic effect at the same time-

The use of a binder with an extremely high specific surface area and a plasticizer. The initial strengths of mortars made from the rapid-setting binder according to the invention are exceptionally high and such strengths cannot be achieved with conventional silicate cements with a specific surface area below 500 m^/kg.

In contrast, dusting alone without a plasticizer, with a reduced water coefficient, produces a mortar that is difficult to work with, sets too quickly and has insufficient strength. Also, with ordinary Portland cement, the plasticizer in a given amount has an adverse effect, namely in reduced strength and in the tendency of the mortar to split.

Example 4

Finally, the suitability of the rapid-setting binder of the invention for the production of concrete with such high initial strengths was demonstrated, which cannot be achieved when using conventional Portland cements with a specific surface area below 500 m^/kg without accelerating hardening. From the dust as in example 4, but with a specific surface area of 675 m ² /kg and a chemical composition of 51.5% CaO, 20.0% S1O2, 11.5% A1 ₂ O ₅ , 5.4% SOj, 15.7% R2O5, with a plasticizing additive of sulfonated polycondensate

- 9,244,351 melamine 8 formaldehyde mixed in a laboratory mixer with forced movement of the mixture two concrete mixtures /a, b/ with the following compositions: dust removal 100 wt. J.

liquidifying agent /amount of dry matter/ 2 wt.

river sand Particles 0 to 4 mm 150 hDotd· quartz sand particles 4 to 8 mm 200 hmcIA water /including moisture of sand and water in the plasticizer/ a/ 55 hmptd· b/ 55 hmptd.

Claims (4)

SUBJECT OF THE INVENTION 244 351, 1. A binder, in particular air or hydraulic mortar, comprising a binder having a specific surface area above 500 m @ 2 / kg and a liquefying additive based on sulfonated polycondensate of phenol or its derivatives, sulfonated or sulfurated polycondensate of melamine or its derivatives, sulfonated or sulfuric polycondenate of naphthaea or sulfonated or sulfuric polycondensate of urea or its derivatives with formaldehyde or polycyclic sulfonate, which has a significant steric effect and reduces the surface tension of water by not more than 15%, in an amount of 0.01 to 10% by weight on dry matter, preferably a weight concentration of 0.2 to 2.5 2. The binder as claimed in claim 1, characterized in that mills for milling conventional cements are used as a binder having a specific surface area above 500 m @ 2 / kg. 3. A binder as claimed in claim 1, characterized in that dusts from mills for grinding dispersion cements with a liquefying additive having a significant steric effect and reducing the surface tension of the water by a maximum of 15 are used as a binder with a specific surface area above 500 m ² / kg. %. 4. The binder as claimed in claim 1, wherein the cement with a specific surface area above 500 m @ 2 / kg is a cement obtained by grinding with the addition of other substances, for example limestone, quartz, slag, bentonite or mixtures thereof.