GB2198124A

GB2198124A - Method of preparing make-up medium for high-slump concrete mixes

Info

Publication number: GB2198124A
Application number: GB8628795A
Authority: GB
Inventors: Vyacheslav Nikolaevi Obraztsov; Evgeny Aristarkhovich Antonov
Original assignee: VNII TRANSPORT STROITELSTVU
Current assignee: VNII TRANSPORT STROITELSTVU
Priority date: 1986-11-27
Filing date: 1986-12-02
Publication date: 1988-06-08
Anticipated expiration: 2006-12-02
Also published as: SE8605089L; SE458755B; JPS63166744A; SE8605089D0; DE3641198A1; GB8628795D0; GB2198124B

Abstract

In the preparation of high-slump concrete mixes, for preparing a make-up medium, cement is mixed with make-up water in a mass ratio of from 1:1 to 1:1.5; a yeast-sulphite waste liquor in an amount from 0.03% to 0.1% of the mass of cement in the concrete mix is added to the resulting mixture, and after that the make-up medium thus formed is subjected to pulsed vibrations, the frequency of medium pulsations ranging from 600 to 950 Hz. The invention has application in the manufacture of highly reinforced large-size articles and structures.

Description

METHOD OF PREPARING MAKE-UP MEDIUM FOR HIGH-SLUMP CONCRETE MIXES The present invention relates to a method of preparing a makeup medium for high slump concrete mixes, and to concrete mixes and articles manufactured by the method.

According to a first aspect of the present invention there is provided a method of preparing a make-up medium for a high slump concrete mix, which method comprises the steps of mixing cement, water and a yeast-sulphite waste liquor.

The present method enables the production of a concrete with improved strength, which may be used in the manufacture of large, reinforced structures and articles.

Typically, the make-up medium is activated by pulsed vibrations in the range 600 to 950Hz. Conveniently, the mass-ratio of cement to water in the make-up medium is in the range of 1:1 to 1:1.5 inclusive.

A sample of concrete prepared with the make-up medium of the present invention, hardened under isothermal conditions of wet heat treatment at 700C in 10 hours, to a tempered strength of 40MPa. The strength of steam-cured 0.1*0.1*0.1 m samples after 28 days of subseqent hardening under normal conditions was in the range 65.5 to 67.5 MPa. A reduction in cement consumption of 20% is obtained in comparison with concrete for which the make-up medium is prepared without activation by vibration.

For maintaining the effect of adsorption plasticizing of the concrete mix and for preserving the increase in the strength of concrete, it is expedient that, according to the present invention, a yeast-sulphite waste liquor should be added to the water-cement mixture in an amount of 0.03 to 0.1% of the mass of cement in the concrete mix.

Further objects and advantages of the present invention will become apparent from the following detailed description of the method of preparing a make-up medium for high-slump concrete mixes and from exemplary embodiments of said method, as well as from examples of preparing high-slump concrete mixes.

The herein-proposed method of preparing a make-up medium for high-slump concrete mixes resides in the following.

A make-up medium for a concrete mix is prepared by mixing cement with water in a mass ratio thereof ranging from 1:1 to 1:1.5 in the presence of a yeast-sulphite waste liquor in an amount of 0.03 to 1% of the mass of cement in the concrete mix. The resulting mixture in the form of an aqueous suspension of cement is pumped by means of a pump through a pulser apparatus in which the make-up medium is subjected repeatedly during a short period of time to pulsed vibrations, the frequency of the medium pulsations ranging from 600 to 950 Hz. The resulting activated medium with the yeastsulphite waste liquor is used as the make-up medium for the concrete mix.

Should the cement-water mass ratio be other than specified above (from 1;1 to 1:1.5), then, if the relative quantity of the treated cement is diminished, the effect of activation of the make-up medium for the concrete mix will be lowered, whereas an increase of cement concentration in the make-up medium will impair its applicability to the high-frequency treatment, because the viscosity of the makeup medium will exceed its permissible values. This will also result in lowering the activation of the make-up medium for the concrete mix.

Bringing the content of the yeast-sulphite waste liquor doen to less than 0.03% lowers the effect of adsorption plastisizing of the concrete mix; as a result, a higher content of make-up water is required, whereas an increase in the content of the yeast-sulphite waste liquor above o.l fails to cause any further increase in plasticizing, but brings down the increase in the strength of concrete.

We have found that the treatment of said aqueous suspension of cement, i.e. of the make-up medium, by subjecting it to high-frequency pulsed vibrations at the frequency of medium pulsations ranging within 600 to 950 Hz, proposed in the present invention, leads to qualitative changes of the medium as a disperse system, namely: in addition to an increase in the degree of dispersity of the solid phase, as a result of the fining and at rition of the surface of cement grains, the pH value of the make-up medium increases due to splitting of some part of the water molecules.Instantaneous hydration of cement particles with the grain size less than 5 jim under the conditions of high-frequency treatment leads to an increase in the volume of highly dispersed hydrate new formations in the form of a gel and to an intensive liberation of calcium hydroxide; therefore, introducing of a small amount of a surfactant, such as yeast-sulphite waste liquor contain ing hydrocarbon radicals with a different degree of polarity, causes development of the adsorption plasticizing effect on the monomolecular level.The action of the abovesaid factors raises the wetting capacity not only of the grains of cement, but also of fine and coarse filler in the course of intermixing of the concrete mix with the make-up medium,this being favoured by an enhanced interaction of the dipole molecules of water with the ions of alumosilicate particles in the surface layer thereof.

The development of the above-stated processes leads to preservation of the concrete mix placeability (without increasing its rigidity), whereas elimination of the excess of surfactant leads, due to the activation effect, to an enhancement of the concrete strength and to a more rapid concrete hardening.

If the pulsation frequency is brought down to less than 600 Hz, the effect of activation of the make-up medium diminishes, and this results in lowering of the concerete strength and in a longer period required for concrete hardening under the conditions of its wet heat treatment.

An increase in the pulsation frequency over 950 Hz causes overfining of cement, and this impairs the concrete strength as well as brings about a smaller increase in the concrete strength upon the wet heat treatment thereof.

Example 1 A make-up medium for high-slump concrete mixes is prepared by mixing 176 kg of cement, 176 1 of make-up water and 132 g of a yeast-sulphite waste liquor in a conventional mixer till an aqueous suspension of cement is obtained. Then this suspension is pumped by means of a pump through a pul ser apparatus, wherein said suspension is subjected during 1.5 to 2 minutes repeatedly to pulsed vibrations, the medium pulsation frequency being equal to 600 Hz.

The make-up medium thus activated is charged into a rotary concrete mixer, into which dry components of a concrete mix, sufficient for obtaining 1 m3 of concrete, have already been metered: 264 kg of cement, 1130 kg of crushed granite of 5-20 mm fraction, and 685 kg of quartz sand. As a result, a high-slump concrete mix is obtained, having a placeability of 5 5 upon compaction by vibration. The hardening time of the resulting concrete under isothermal conditions of wet heat treatment at 700C, till the required tempered strength of 40 MPa is attained, is 10 h. The strength of steam-cured concrete (10x10x10 cm sample) after 28 days of subsequent hardening under normal conditions is 66.0 :,IPa.

Example 2 A make-up medium for high-slump concrete mixes is prepared by following a procedure similar to that described in Example 1, using 117 kg of cement, 176 1 of water, and 323 g of a yeast-sulphite waste liquor. Treatment of the make-up medium by subjecting it to pulsed vibrations is carried out at the frequency of pulsations of 950 Hz.

The make-up medium thus activated is charged into a rotary concrete mixer, into which dry components of a concrete mix, sufficient for obtaining 1 m3 of concrete, have already been metered: 206 kg of cement, 1130 kg of crushed granite of 5-20 mm fraction, and 685 kg of quartz sand. The hardening time of the resulting concrete under isothermal conditions is 10 h, the strength of steam-cured concrete after 28 days of storage is 65.5 MPa.

Example 3 A make-up medium for a high-slump concrete mix is prepared by following a procedure similar to that described in Example 1, using 140 kg of cement, 176 1 of water and 195 g of a yeast-sulphite waste liquor. The treatment of the makeup medium by pulsed vibrations is carried out at the frequency of 775 Hz.

The make-up medium thus activated is charged into a rotary concrete mixer, into which dry components of a concrete mix, sufficient for obtaining 1 m3 of concrete, have already been metered: 160 kg of cement, 1130 kg of crushed granite of 5-20 mm fraction, and 685 kg of quartz sand.

The hardening time of the resulting concrete under isothermal conditions is 9.5 h till its tempered strength is attained, whereas the strength of steam-cured concrete after 28 days of storage is 67.5 MPa.

Example 4 A high-slump concrete mix is prepared for making highly reinforced articles and structures with a place ability of 5 s (on compaction by vibration) and with the tempered strength of 40 MPa in the course of wet heat treatment at 700C.

For preparing 1 m3 of concrete 550 kg of cement, 1075 kg of crushed granite of 5-20 mm fraction, 610 kg of quartz sand, 200 1 of water, and 0.7 kg (0.15%) of a yeast-sulphite waste liquor are used.

The make-up medium in this case is water. The technology of preparing the high-slump concrete mix consists in intermixing the mix components in a concrete mixer.

This technology allows the attaining of the above-spe cified tempered strength of the concrete only after 18 h of its isothermal curing. Therefore, the energy requirements for steam-curing the concrete are 30 to 35% higher compared with the technology described in Example 1, whereas the strength of the steam-cured concrete after 28 days of subsequent hardening is 52.5 MPa only.

Example 5 A make-up medium for a high-slump concrete mix is prepared by following a procedure similar to that described in Example 1, but treatment of the make-up medium by pulsed vibrations is carried out with the frequency of pulsations of 50 Hz. The make-up medium thus activated is combined with dry components of a concrete mix in a manner similar to that set forth in Example 1. With the placeability of the concrete mix being preserved, the strength of the resulting concrete is 45.1 MPa, the time of concrete steam-curing being 18 h.

This is due to the fact that for the required slump of the concrete mix to be preserved upon fining of cement, it is necessary to introduce an additional quantity of water because of an increase in the cement dispersity and, hence, because of higher water requirements. This factor has a negative effect on the strength characteristics of the concrete, since the water-cement ratio increases.

Example 6 (in conformity with the technology disclosed in Inventor's Certificate of the USSR No. 568612, as applied to high-slump concrete mixes).

A make-up medium for a concrete mix is prepared by mixing together 550 kg of cement and 220 1 of make-up water.

The resulting mixture is subjected to activation by vibration with the aid of a dipole vibrator at the frequency of 50 Hz.

The activated make-up medium is used for preparing a highslump concrete mix with the following amounts of materials per m3 of concrete: 1075 kg of crushed stone of 5-20 mm fraction, 590 kg of quartz sand. The resulting concrete has a strength of 57.8 MPa after steam-curing and subsequent storage during 28 days. The time of concrete hardening under isothermal conditions of wet heat treatment at 709C till the attainment of the required 80% strength is 18 he Example 7 A high-slump concrete mix is prepared for making highly reinforced articles and structures, having a placeability of 5 s (on compaction by vibration) and a tempered strength of 40 ;a in the course of wet heat treatment at 700 C.

For preparing 1 m3 of concrete 440 kg of cement, 1130 kg of crushed granite of 5-20 mm fraction, 705 kg of quartz sand, 150 1 of water, and 3.52 kg (0.8%) of a superplasticizer are required.

In this case water is used as the make-up medium The concrete mix is prepared by intermixing the components in a concrete mixer.

This technology allows the attaining of the above-stated tempered strength of concrete only after 18 h of isothermal curing; this involves a 30 to 35% increase in power requirements for steam-curing of the concrete, compared with the technology set forth in Example 1; the strength of the steamcured concrete after 28 days of subsequent hardening is 54.0 MPa only.

Comparison of the physico-mechanical characteristics of concretes prepared from high-slump concrete mixes as set forth in the Examples Nos. Characteristics Technologyof concrete preparation ~~~~~~~~ ~~~~~~~~~~~~~ ~~ ~~~~~~~~~~ As in As in As in As in Ex Examp- Example Example ample 6 le 4 7 1 1 2 3 4 5 6 1. Placeability of concrete mix, s 5 5 5 5 2. Consumption of 3 materials per m of concrete: 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 in %0 of the mass of cement: 2.5 superplasticizer - 0.8 2.6 yeast-sulphite waste liquor 0.15 - 0.03 0.15 3. Time of concrete hardening under isothermal con ditions of wet heat treatment at 70"0 till the required 80% strength is at tained, h 18 18 10 18 4. Strength of steam cured concrete after storage under normal conditions during 28 days, MPa 52.5 54.0 66.0 57.8

Claims

CLAIMS; 1) A method of preparing a make-up medium for a high slump concrete mix. which method comprises the steps of mixing cement, water and a yeast-sulphite waste liquor.
2) The method of claim 1. wherein the make-up medium is activated by pulsed vibrations in the range 600 to 950Hz.
3) The method of claim 1 or 2 wherein the mass-ratio of cement to water in the make-up medium is in the range of 1:1 to 1:1.5 inclusive.
4) The method of any of claims 1, 2 or 3 wherein the yeastsulphite waste liquor is added to the cement/water mixture in an amount from 0.03% to 0.1% of the mass of the cement in the concrete mix.
5) A method of preparing a make-up medium for a high slump concrete mix as hereinbefore described by way of example.
6) A high-lump concrete mix or article produced by the method of any of claims 1-4.