FI81335C - FOERFARANDE FOER FRAMSTAELLNING AV TILLSATSMATERIAL FOER BETONGBLANDNINGAR MED HOEG SMIDIGHET. - Google Patents

Description

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The present invention relates to the preparation of an admixture for high-flexibility concrete mixtures which can be used to prepare concrete of improved strength for use in the manufacture of high-strength, large-sized articles and structures.

The additive prepared according to the invention can be used both in the manufacture of building structures and in sorting processes in which it is used as a aggravating agent in the separation of bulk materials, e.g. ash and slag waste generated in thermal power plants.

A method for preparing a suspension for use in the manufacture of mortar is known in the art, in which a suspension consisting of, for example, cement and water is vigorously mixed with an impeller mixer whose rotational speed generates cavitation (GB Patent No. 20,115,481).

This method produces colloidal suspensions in which 25% of the cement particles are covered with a gel-like surface layer, which improves the wettability of the particles.

This is an obstacle to the intensive treatment of cement, which could form the required amount of gel aggregates from the intermediates formed in the hydration of the cement, and at the same time it is an obstacle to improving the adsorption capacity of the suspension.

A method for mixing cement and water as a turbulent flow is also known (GB Patent No. 1,487,779, Cl. BolF 3/12).

In this method, water is fed to the vessel by a metering device system, then small portions of 2,81335 dry materials, e.g., cement, clay, or other bulk materials, are fed into the vessel and the resulting aqueous suspension is pumped by a turbulent flow for 30 seconds. The container is then emptied and refilled. Method 5 can quickly prepare a mortar, but not an activated cement slurry, because during the permitted 30-second mixing period, only strong wetting of the cement particles can occur, but not their abrasion, crushing and other processes necessary for gel formation. Thus, the method described above cannot solve the problem of soil to improve the strength of concrete made of high-flexibility mixtures, nor the problem of accelerating hardening.

A method is known in the art for intensifying physical processes and chemical reactions between solid particles and a liquid flow, in which the particles are suspended in a pulsating liquid stream containing a finely divided additive, e.g. malt used in the preparation of beer wort.

The continuous flow of the formed suspension is periodically forced through special nozzles with an adjustable orifice so that the flow rate alternately accelerates and decelerates (FR Patent No. 2,133,884, Cl. B01f 3/00, B01y 1/100, published in 1972).

25 Depending on the area of the directional opening, the pressure in the nozzle varies from 1 to 30 m H 2 O and the velocity of the pulsating liquid flow varies accordingly. Heating to 70-75 ° C accelerates the interaction between the reactants dispersed to the molecular fineness.

The absence of a cavitation phenomenon prevents the effective application of the method described above for the treatment of cement particles and the preparation of activated suspensions.

A method for preparing an admixture for concrete mixtures is known in the art, which is characterized by mixing cement and water belonging to the admixture.

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3,81335 in a ratio of 1: 0.001 to 1: 0.003. The formed admixture is fed into the concrete mixture and the latter is activated by vibration.

This procedure makes it possible to reduce the consumption of cement and water in the concrete mix by 10% (compared to the Akti-5 non-reinforced concrete composition) and at the same time the strength of the concrete samples (10 x 10 x 10 cm) reaches 29.0 MPa after steam hardening. the USSR No. 681,012, published 1979). However, this method cannot be applied to the production of high-flexibility concrete mixtures used in the production of high-strength concrete, because the grinding of cement by vibration activation requires that more admixture water be mixed into the concrete mixture due to the increased water consumption of the mixture.

A method for preparing an activated admixture for use in concrete mixtures is known, characterized in that cement, which is 5 to 40% by weight of the total amount of cement contained in the concrete, and admixture water are mixed continuously for 5 to 25 minutes. The maximum strength of grade-20 concrete-20 n is achieved in the samples after 25 minutes of activation due to the abrasion of the surface of the granules which takes place in part of the cement (Inventor's Certificate of the USSR No. 643,457, published in 1979). This method is not suitable for the production of improved strength concrete from high flexibility alloys and cannot be used for the production of highly reinforced concrete articles and structures.

A method for preparing an admixture for use in a concrete mix is known in the art, characterized in that the cement and the excess water are mixed and the mixture is heated to 50 ° C. The aggregate is added to the formed admixture and the concrete mixture is mixed for a long time. The strength of the concrete specimens is improved by 20% due to the increased stiffness of the concrete mix due to abrasion of the cement particles and the surfaces of the aggregate particles and the effect of elevated temperature 4,81335, which accelerates cement hydration (Inventor's Certificate of the USSR No. 485,089, published 1971). This method is not useful in the preparation of high-strength concrete from high-flexibility concrete mixtures.

In particular, the process of the present invention is a process for preparing an admixture for use in concrete mixtures, characterized in that the entire amount of cement and water is mixed and then activated by vibration, the vibration being carried out with a dipole vibrator operating at 50 Hz. The duration of the vibration activation of the admixture is 5 to 10 minutes, after which the dry components of the concrete mix are added to the admixture.

The strength of the concrete 15 prepared with the activated additive doubles and reaches a value of 80.0 MPa (Invertor's Certificate of the USSR No. 568,612, published in 1,975). In this method, the increase in strength is mainly due to the increase in the viscosity of the concrete mix, which is achieved by using a low water-cement ratio. Such concrete mixtures 20 can be prepared with a shrinkage value greater than 300 s by compacting them by vibration. There are some technical and production inconveniences associated with their use, as they require prolonged sealing with vibrated overload. The addition of an additional amount of water 25 to maintain the required compressibility impairs the increase in strength of the concrete until complete loss of strength. This method is not useful in the production of high-flexibility concrete mixes and, moreover, it cannot solve the problem of accelerating the curing of concrete-30 under conditions of moist heat treatment and normal curing.

It is an object of the present invention to provide a process for the preparation of an admixture for the preparation of high-flexibility concrete mixtures by modifying the technical properties of the mixtures so that the additive

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5 81335 makes it possible to accelerate the hardening of concrete during the wet heat treatment of concrete and during normal hardening.

The object of the invention is solved by preparing an admixture for high-flexibility concrete mixtures 5 by a method known from mixing cement and water, adding yeast sulphite waste slurry to the resulting mixture and finally activating the prepared admixture by vibration to mix cement and water in a weight ratio of 1: 1. ... 1: 1.5 and Akti-10 can then be prepared by vibrating the additive so that the oscillation frequency of the additive is in the range of 600 to 950 Hz.

The time required to cure the concrete prepared with the additive of the present invention under the isothermal conditions of the wet heat treatment at 70 ° C so that the required strength of 40 MPa is reached by hardening is 10 hours. The strength of the steam-hardened concrete in the 10x10x10 cm samples after 28 days of further curing under normal conditions ranged from 65.6 to 67.5 MPa and the consumption of cement was 20% less than that of the concrete, the additive of which was prepared without vibration activation.

In order to maintain the adsorption plasticizing effect of the concrete mix and to maintain the increase in the strength of the concrete, it is expedient according to the present invention to add 0.03 to 0.1% yeast sulphite waste slurry to the water-cement mix, based on the weight of the cement in the concrete mix.

Other objects and advantages of the present invention will become apparent from the following description, which describes in detail a method for preparing an admixture for high-flexibility concrete mixes, and examples of the implementation of said method, and high-flexibility concrete mixes.

The method proposed here for preparing an admixture for high-flexibility concrete mixes is characterized by the following.

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The admixture for the concrete mix is prepared by mixing cement and water in a weight ratio of 1: 1 to 1: 1.5 in the presence of yeast sulphite waste liquor in an amount of 0.3 to 1% by weight of the cement in the concrete mix. The mixture formed in the form of an aqueous cement suspension is pumped through a vibrator, in which the medium is repeatedly vibrated for a short time so that the oscillation frequency of the additive is in the range from 600 to 950 Hz. The formed medium Ί0 containing activated yeast sulphite waste slurry is used as an additive in the concrete mix.

If the weight ratio of the cement-water mixture must be different from that defined above (1: 1 ... 1: 1.5) and if the relative amount of treated cement is reduced, the activation of the admixture in the concrete mix will deteriorate, while increasing the cement concentration in the admixture will impair the suitability of the viscosity of the additive exceeds the permitted values. For this reason, the activation of the additive used in the concrete mix also deteriorates.

Reducing the concentration of the yeast sulphite waste liquor to less than 0.03% reduces the adsorption plasticisation of the concrete mix and therefore more water must be used in the admixture. Increasing the concentration of yeast sulfite waste liquor above 0.1% does not increase plasticization, but inhibits the increase in the strength of concrete.

We have found that the treatment of said cement aqueous suspension or additive as proposed according to the invention by high frequency vibration at 600-950 Hz changes the properties of the additive acting as a dispersed system, i.e. the degree of solid phase dispersion improves due to pH particle surface grinding and grinding water molecules are broken down. Immediate hydration of cement particles with a size of less than 5 μm during high-frequency 35 treatment results in a highly dispersed

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V 81335 hydrate volume increase, new gel growth, and vigorous release of calcium hydroxide. Thus, the addition of a small amount of a surfactant, e.g., a yeast sulfite waste liquor containing hydrocarbon radicals of varying polarity, produces an adsorption plasticizing effect at the monomolecular level. The factors described above improve not only the wettability of the cement particles, but also the wettability of the fine and coarse aggregate in the mixing step of the concrete mix and the admixture. This phenomenon is promoted by the interaction between the dipole molecules of water and the aluminosilicate particle ions on the surface of the particles.

The development of the processes described above leads to the preservation of the compressibility of the concrete mix (without an increase in stiffness) and, on the other hand, the elimination of excess surfactant leads to an improvement in the strength of the concrete and faster curing of the concrete.

If the oscillation frequency is reduced to less than 600 Hz, the activation of the admixture decreases and, as a result, the strength of the concrete 20 decreases and the curing time of the concrete increases under the conditions of moist heat treatment.

Increasing the oscillation frequency above 905 Hz causes the cement to be over-finished and this degrades the strength of the concrete and a smaller increase in the strength of the concrete after moisture heat-25 treatment.

Example 1

An admixture for use in high-flexibility concrete mixes was prepared by mixing 176 kg of cement, 176 l of admixture water and 132 g of yeast sulfite waste slurry in a conventional mixer until an aqueous cement suspension was obtained. This suspension was then pumped through a vibrator in which said suspension was repeatedly vibrated for 1.5-2 minutes at an additive oscillation frequency of 600 Mz.

8 81335 The thus-activated aggregate was charged to a rotating concrete mixer already fed with the dry components of the concrete mix to form 1 m 2 of concrete: 264 kg of cement, 1,130 kg of granite chippings, a fraction of 5-20 mm, and 685 kg of 5 quartz sand. A high-flexibility concrete mixture with a compressibility value of 5 s after vibration compression was obtained. The time required to cure the formed concrete under the isothermal conditions of the wet heat treatment at 70 ° C so as to reach the required strength of 40 MPa was 10 hours. The strength of steam-hardened concrete (sample size 10 x 10 x 10 cm) after 28 days of further curing under normal conditions was 66.0 MPa.

Example 2

An admixture for high flexibility concrete mixes was prepared as described in Example 1 using 117 g of cement, 176 l of water and 323 g of yeast sulphite waste broth. The additive was treated by vibrating it at an oscillation frequency of 950 Hz.

The thus-activated aggregate was charged to a rotating concrete mixer 20, which had already been metered into the dry components of the concrete mix to form 1 m of concrete: 206 kg of cement, 1,130 kg of granite chippings, a fraction of 5-20 mm, and 685 kg of quartz sand. The curing time of the formed concrete under isothermal conditions was 10 hours; the strength of the steam-hardened concrete after 28 days of storage was 65.5 MPa.

Example 3

An additive for use in a high-flexibility concrete mix was prepared as described in Example 1 using 140 kg of cement, 176 l of water and 195 g of yeast-30 sulphite waste broth. The additive was treated by vibrating it at 775 Hz.

The admixture thus activated was charged to a rotating concrete mixer to which the dry components of the concrete mix had already been metered to form 1 m of concrete: 160 kg of cement, 35 l of 130 kg of granite chippings, a fraction of 5-20 mm, and 685 kg of quartz sand.

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The curing time of the formed concrete under isothermal conditions was 9.5 hours, at which time the hardening strength was achieved; the strength of steam-hardened concrete after 28 days of storage was 67.5 MPa.

5 Example 4

A high-flexibility concrete mix was prepared for use in the manufacture of highly reinforced articles and structures with a compressibility value of 5 s (when compacted by vibration) and a hardening strength of 40 MPa during wet-10 heat treatment at 70 ° C.

550 kg of cement, 1,075 kg of granite chippings, a fraction of 5-20 mm, 610 kg of quartz sand, 200 l of water and 0.7 kg (0.15%) of yeast sulphite waste broth were used to make one cubic meter of concrete.

15 In this case, the additive was water. The high density concrete mix was prepared by mixing the mix components in a concrete mixer.

This technique was able to achieve the hardening strength of the concrete defined above only after an 18-hour isotherm-20 after its hardening. Thus, the energy requirement for steam hardening of concrete was 30-35% higher than in the technique described in Example 1; the strength of the steam-hardened concrete after 28 days of curing was only 52.5 MPa.

Example 5 An admixture for use in a high flexibility concrete mix was prepared as described in Example 1, but the vibration treatment of the admixture was performed at an oscillation frequency of 50 Hz. The thus-activated additive was added to the dry components of the concrete mix in the same manner as in Example 1. The sealability of the concrete mix was maintained, the strength of the formed concrete was 45.1 MPa, and the steam hardening time of the concrete was 18 hours.

These values are due to the fact that in order to maintain the required flexibility of the concrete mix after grinding the cement, it is necessary to add more water due to the increase in the degree of dispersion of the cement and thus the higher water demand. This negatively affects the strength properties of the concrete due to the increase in the water-cement ratio.

Example 6 5 (Corresponding to the technique disclosed in Inventor * a Certificate of Teh USSR No. 568 612 applied to high flexibility concrete mixes.)

The admixture to be used in the concrete mix was prepared by mixing 550 kg of cement and 220 l of admixture water.

The resulting mixture was activated by vibrating with a dipole vibrator at 50 Hz. The activated admixture was used to prepare a high-flexibility concrete mix with the following amounts of material per cubic meter of concrete: 1,075 kg of crushed stone, fraction 5-20 mm, 590 kg of quartz sand.

15 The strength of the concrete formed was 57.8 MPa after steam hardening and subsequent 28-day storage.

The time required to cure the concrete under moist heat treatment isothermal conditions at 70 ° C to achieve the required 80% strength was 18 hours.

20 Example 7

A high-flexibility concrete mix was prepared for use in the manufacture of highly reinforced articles and structures with a compressibility value of 5 s (when compacted by vibration) and a hardening strength of 40 MPa during wet heat treatment at 70 ° C.

To prepare one concrete cubic meter, 440 kg of cement, 1,130 kg of granite chippings, a fraction of 5-20 mm, 705 kg of quartz sand, 150 l of water and 3.52 kg (0.8% super-plasticizer) were required.

30 In this case, the additive was water. The concrete mix was prepared by mixing the components in a concrete mixer.

This technique was able to achieve the hardening strength of the concrete defined above only after 18 hours of isothermal hardening. Thus, the energy requirement for steam hardening of concrete was 30-35% higher than in Example 1

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11 81335 in the described technique; the strength of the steam-hardened concrete after 28 days of curing was only 54.0 MPa.

Comparison of the physical-mechanical properties of concretes made from the high-flexibility concrete mixtures described in the examples

No. Characteristics Concrete manufacturing technology

Like Like Like Like _esim. 4 eg 7 eg 1 eg 6 10 __J_2_3_4_5_6 1. Compressibility of concrete mix 5 5 5 5 3 2. Consumption of material per m of concrete: 15 2.1 Cement kg 550 440 440 550 2.2 Crushed stone kg 1075 1130 1130 1075 2.3 Sand kg 610 705 685 590 2.4 Water 1 200 158 176 220

Additive% by weight of cement 20 2.5 Superplasticizer - 0.8 - 2.6 Yeast sulphite waste broth 0.15 - 0.03 0.15 3. Curing time of concrete under isothermal conditions of moist heat treatment at 70 ° C to achieve the required 80% strength h 18 18 10 18 4. Strength of steam-hardened concrete after 28 days of storage under normal conditions MPa 52.5 54.0 66.0 57.8

Claims (2)

12 81 335 1. A process for preparing additives for high-flexibility concrete mixtures by mixing cement and water, adding yeast sulfite effluent to the obtained mixture and activating the thus-obtained additive material by the vibration, characterized in that cement and water are mixed in the weight ratio of 1: 1 ... 1: 1.5 and that the prepared auxiliary material is then activated by vibrations within the vibrational range of the auxiliary material 600 - 950 Hz. 1. Menetelmä lisäaineen valmistamiseksi suuren notkeuden omaavia betoniseoksia varten siten, eenä sekoite- taan sementti ja vesi, muodostuneeseen seokseen lisätään hiiva-sulfiittijätelää si lopuksi näin valmistettu lisäaine aktivoidaan täryttä 1: 1.5 yes one valmistettu lisäaine activoidaan sit täryttämällä 10 sitä lisäaineen verähtelytaajuudella 600 - 950 Hz. 2. Patenttivaatimuksen 1 mukainen menetelmä, tunnettu siitä, one vesi-cementtiseoxyene lisätään 0.03-0.1% hiiva-sulfiittijätelientä betoniseoksessa olevan sementin painosta laskettuna. 15 2. A process according to claim 1, characterized in that in the water-cement mixture is added 0.03 - 0.1% yeast sulfite effluent calculated on the weight of cement in the concrete mixture. Il