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CONSTRUCTION MATERIALS. CONSTRUCTION COMPOSITIONS, MIXTURES AND COMPOSITIONS FOR MANUFACTURING BUILDING MATERIALS AND CONSTRUCTION OF CONSTRUCTION WORKS
INVENTION
Patent of the Russian Federation RU2085542

A METHOD FOR PREPARING A WATER SUSPENSION OF A MICROCRADEZE

The name of the inventor: Caprielov SS; Batrakov VG; Sheynfeld A.V.
Name of the patentee: Center for Modified Concretes
Address for correspondence:
Date of commencement of the patent: 1994.08.04

Use: in the preparation of concentrated and stable suspensions of microsilica, used as an active mineral additive for concrete.

SUMMARY OF THE INVENTION: Increasing the fluidity and aggregative stability of a slurry in time and its activity in concrete. For this purpose, in the process for preparing the aqueous suspension, a two component substance based on nitrilotrimethylene phosphonic acid and the condensation product is used as the stabilizing component - naphthalenesulfonic acid with formaldehyde with the following ratio of components, mass% : microsilica 40-70 , nitrilotrimethylenephosphonic acid 0.02-0.14 , condensation product of a-naphthalenesulfonic acid with formaldehyde 0.02-0.14 , water remaining.

DESCRIPTION OF THE INVENTION

The invention relates to methods for preparing fluid, concentrated and stable microsilica suspensions used as an active mineral additive for concrete.

A method for the preparation of concentrated slurries from microsilica (TU 67-602-9-88 Pulp Sulkram) is known , which includes the introduction of 20-30% concentration in aqueous suspension from microsilica, sodium sulfate (23-25% of MK mass) and sodium nitrite 5% of the mass of Na 2 SO 4 ) [1]

The disadvantage of Sulcream pulp is its instability in long-term storage: periodic mixing of the suspension is required to prevent delamination.

The closest to the technical essence and the achieved result is the method of preparing concentrated stable suspensions from microsilica, including mixing an aqueous suspension of microsilica of 70-75% concentration with a stabilizing component hydrochloric, sulfuric, or acetic acids (0.35% 0.74% 0.37% Mass MK, respectively) [2]

The disadvantage of this method is that the use of hydrochloric, sulfuric or acetic acid as a stabilizer causes a relatively short-term effect of aggregative stability of the suspension (up to 15 days ), since the acid is constantly neutralized by alkaline components of microsilica. Therefore, during long-term storage or transportation of the suspension, microsilica particles aggregate and it becomes necessary to periodically add new amounts of acid, which in turn leads to a decrease in the activity of the microsilica suspension as an additive to the concrete.

The technical task is to increase the aggregative stability and fluidity of the suspension in time, as well as its activity as a mineral additive for concrete.

This object is achieved in such a manner that a mixture of nitrilotrimethylene phosphonic acid and a condensation product is used as the stabilizing component in the process for preparing an aqueous suspension comprising mixing microsilica, water and a stabilizing component, -naphthalenesulfonic acid with formaldehyde with the following component ratio, wt .

  • Microsilica 40-70
  • Nitrilotrimethylenephosphonic acid 0.02-0.14
  • The condensation product of b- naphthalenesulfonic acid with formaldehyde is 0.02-0.14
  • Water Other

The proposed method differs from the prototype in that, with the new component ratios, a mixture of nitrilotrimethylene phosphonic acid and the condensation product of b-naphthalenesulfonic acid with formaldehyde is used as the stabilizer, which, due to the complex action, leads to the dispersion of microsilica aggregates, more complete binding of metal ions on the particle surface to poorly soluble Complexes, the formation of low-permeability adsorption layers and the modification of the double electric layer on the surface of microsilica particles. This leads to a combined steric and electrostatic suspension stabilization effect, which increases the aggregate stability and fluidity in time and, as a consequence, increases its activity as a mineral additive for concrete.

Consequently, the claimed method meets the criteria of "novelty" and "inventive step".

The method of preparing aqueous suspensions is as follows: the calculated amount of components, Water 29.44-59.90 ; Stabilizer-nitrilotrimethylenephosphonic acid 0.02-0.14 and the condensation product of b- naphthalenesulfonic acid with formaldehyde 0.02-0.14 ; Microsilica 40-70 , which are vigorously mixed until a homogeneous suspension of 40-70% concentration is formed.

Example
The characteristics of the materials used for the preparation of suspensions are given below.

As microsilica (MK), ultradispersed waste from the ferrosilicon production of the Chelyabinsk Electrometallurgical Combine of the grade MK-85 according to TU 7-249533-01-90 was used .

The stabilizing components used were:

  • Sulfuric acid (H 2 SO 4 ) , corresponding to GOST 4204-77 ;
  • An aqueous solution of nitrilotrimethylenephosphonic acid (NTP ) -N (CH 2 PO 3 H 2 ) 3 corresponding to TU 6-09-5283-86 (with notices 1-4 );
  • Condensation product of b- naphthalenesulfonic acid with formaldehyde - superplasticizer S-3 NGO Orgsintez (one of the representatives of products of this class) corresponding to TU 6-36-0204229-625-90 .

To determine the viscosity and aggregative stability over time, aqueous suspensions of microsilica were prepared. As a control sample, a suspension prepared according to the prototype method [2]

Aggregative stability of the suspensions was evaluated by sedimentation analysis using the " Lumosed " photometry "RETSCT" (FRG) from the change in the intensity of the light flux passing through the cuvette with the suspension sample over a certain period of time. This allowed us to determine the concentration of suspensions along the height of the cell, and, due to mathematical transformations according to Stokes's formula, determine the diameter and mass content of aggregates.

For visual illustration, the data on granulometric compositions of the suspensions were transformed in accordance with the Rosin-Ramler equation and the characteristic particle sizes were given.

The viscosity of the suspensions was determined on a rotational viscometer (RPE-1M Polymer) with a gap between coaxial cylinders of 2.1 mm with a shear rate gradient of 1.05 s -1 and a temperature of 22 ± 1 ° C.

The pH of the suspensions was determined on a pH meter , grade I-120M .

The results of the studies of suspensions are given in Table 1

To determine the activity of suspensions from microsilica as additives to concrete, concretes with an additive of Compositions N 1 and 4 were examined ( Table 1 ). As a control, concrete is added with the addition of a superplasticizer C-3 and a suspension prepared according to the prototype method [2] (composition No. 1 , Table 1 ). The concretes had the same composition, and the suspensions stored for 90 days were added in an amount in which the dosage of microsilica (on dry matter) was 20% of the mass of the cement, the water included in the suspension being taken into account as mixing water.

The activity of suspensions was estimated from the mobility of concrete mixtures (OK) and the strength of concrete at 1, 3, 7, 14 and 28 days of normal hardening, which was determined on samples of cubes 10x10x10 cm according to the standard procedure.

Materials used:

  • Portland cement M400 of the Voskresensky plant, corresponding to GOST 10178 ;
  • Superplasticizer S-3 NGO "Orgsintez" , corresponding to TU 6-36-0204229-625-90 ;
  • Quartz sand with M cr = 2,1 ;
  • Rubble granite fraction 5-20 mm .

Compositions of concrete mixtures and test results are given in Table. 2 .

As can be seen from the results, the pH of the suspensions of formulations N 2-6 is in the range from 6.9 to 8.4 , which indicates the neutral character of the medium of the suspensions and their non-aggressive nature with respect to metals ( Table 1 ).

A 70% concentration suspension prepared according to the composition of the prototype ( No. 1 , Table 1 ), having stable aggregative stability and a viscosity of up to 15 days at a pH of 4.0-5.0, with an increase in shelf life of up to 90 days as the pH rises Suspension to 7.9 loses its stability with a simultaneous increase in the viscosity of the system.

The proposed microsilica suspensions (formulations N 3-5 , Table 1 ) have significantly greater fluidity and aggregative stability, which practically do not change until 90 days of storage, i.e. Have a consistent consistency over time. The production of higher concentration suspensions (Composition No. 6 , Table 1 ) leads to a sharp increase in the viscosity of the system, despite significant dosages of the stabilizer. Reduction of the dosages of the stabilizer (composition No. 2 , Table 1 ) leads to the separation of the solid and liquid phases.

As can be seen from the results of the concrete test ( Table 2 ), the use of a mixture of nitrilotrimethylenephosphonic acid and the condensation product of b- naphthalene sulfoxide with formaldehyde as a stabilizer of a suspension of microsilica results in some increase in the mobility of concrete mixtures and a significant increase (by 130-210 % ) in the strength of concrete in Early dates of hardening, which indicates an increased pozzolanic activity of these suspensions compared with the control one.

Thus, the proposed microsilica suspensions are not aggressive to metals, have increased fluidity, prolonged up to 90 days aggregative stability and increased in comparison with the prototype pozzolanic activity.

CLAIM

A process for the preparation of an aqueous microsilica slurry comprising mixing microsilica, water and a stabilizing component, characterized in that a mixture of nitrilotrimethylene phosphonic acid and a condensation product of beta-naphthalenesulfonic acid with formaldehyde is used as the stabilizing component at the following component ratio,

  • Microsilica 40-70
  • Nitrilotrimethylenephosphonic acid 0.02-0.14
  • The condensation product of beta-naphthalenesulfonic acid with formaldehyde 0.02-0.14
  • Water Ostalog

print version
Date of publication 26.11.2006гг