RU2460701C2 - Complex additive for concrete mix and concrete mix - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: complex additive for a concrete mix including cement and sand contains 50-96 wt % of glycerine and 4-50 wt % of polyacrylamide. The concrete mix includes cement, sand and a complex additive. The complex additive contains relative to the cement weight 0.1-0.6% of glycerine and 0.025-0.1% of polyacrylamide.

EFFECT: increased strength of concrete stone.

6 cl, 1 tbl

Description

The invention relates to concrete mixtures with additives used to protect against corrosion and sanitation of metal and concrete pipelines by applying a layer of the mixture on their inner surface, as well as to perform repair and restoration or special construction work, for example, such as restoring the geometry of degraded concrete structures and structures, as well as to increase the adhesion and strength of building concrete.

There are a large number of additives in the concrete mixture, which allow regulating its properties such as adhesion to metal or concrete surfaces, reducing the probability of separation of concrete mixture into fractions, increasing its workability (plasticity), improving thixotropic properties, increasing the density and strength of concrete stone. These additives are currently widely used for the preparation of adhesive, thixotropic, repair and other concrete mixtures. At the same time, to give the desired properties of the concrete mix, it is often necessary to introduce a rather large number of additives into its composition, which significantly increases the cost of the mixture. Often the improvement of a certain characteristic of a mixture leads to a deterioration in its other properties. For example, improving the adhesion and strength characteristics of a concrete mixture by introducing polymer dispersions into its composition leads to a decrease in the strength of a concrete stone when it is wetted. The introduction of isocyanates into the concrete mixture improves its mechanical properties, but sharply reduces its survivability.

The influence of various polymers on the properties of concrete is most widely described in the monograph of Yu.M. Bazhenov "Concrete polymers", Stroyizdat, 1983, 472 p. Mixtures of diisocyanates with polyesters (GB 1192864 A) have proven themselves as reinforcing concrete additives. An increase in the strength of concrete stone is currently usually achieved by reducing the water-cement ratio, which is ensured by the use of plasticizers of the concrete mixture. The most widely used plasticizers are lignosulfonates and naphthalene derivatives. To control the rheological properties of the concrete mixture, polyalkylene oxides, polysaccharides, cellulose ethers, polyacrylic acid, polyacrylamide, starch and mixtures of these substances can be used (US 2009/0197991 A1). To regulate the properties of the concrete mixture, it is recommended to use derivatives of unsaturated bicarbonates (patent EP 0930321 A1). Resin from copolymers is recommended as an additive for concrete mixtures designed to fill gaps (EP 0968977 A).

Tests of various single and complex additives (combinations of various additives) showed that they do not provide such a change in the properties of the concrete mixture that would eliminate all the problems that arise, in particular, during the rehabilitation of degraded metal and concrete pipelines.

The concrete mixture applied to the inner surface of the pipe should have a relatively high mobility to ensure the possibility of mechanized supply to the place of work (the recommended draft of the concrete mix cone for pumping it should be within 3.8-10 cm), at the same time it should not run off the surface of the pipe and delaminate. Cured concrete must have high strength and deformability, especially under bending loads, and high adhesion to metal and concrete.

The basis of the invention is the task to develop such a comprehensive additive for concrete mixture, which gives the concrete mixture high thixotropic properties with a simultaneous increase in the strength of the formed concrete stone and its adhesion to metal and concrete.

Another objective of the invention is the development of a concrete mixture having high thixotropic properties and at the same time providing an increase in the strength of the formed concrete stone and its adhesion to metal and concrete.

In accordance with a first aspect of the invention, there is provided a comprehensive additive for a concrete mixture comprising cement and sand, containing 50-96 wt.% Glycerol and 4-50 wt.% Polyacrylamide.

Preferably, the complex additive further comprises a polyester in the following ratio of components: 50-63 wt.% Glycerol, 7-12 wt.% Polyacrylamide and 32-45 wt.% Polyester.

Preferably, the complex additive as polyester comprises polyethylene glycol maleinatftalat, polidietilenglikol maleinatftalat, politrietilenglikol maleinatftalat, maleate polyethylene glycol condensation product or propoxylated diphenylolpropane with maleic anhydride, fumarate polidietilenglikol, poli1,2-propylene glycol adipate, or polidietilenglikol hlormaleinat politrietilenglikol isophthalate.

In accordance with a second aspect of the invention, there is provided a concrete mixture comprising cement, sand and a complex additive containing 0.1-0.6% glycerol and 0.025-0.1% polyacrylamide with respect to the cement mass.

Preferably, the complex additive included in the concrete mixture additionally contains a polyester with the following components in relation to the mass of cement: 0.1-0.6% glycerol, 0.025-0.1% polyacrylamide and 0.01-0.5% complex polyester.

The use of each of the components of a complex additive separately or as part of other complex additives is known.

So, there is a known method of preparing a concrete mixture (SU 624896), in which cement, sand, crushed stone and mixing water are mixed into which glycerin is previously added in an amount of from 0.05 to 0.3% by weight of cement.

The addition of glycerol causes the formation of calcium polyglycerates, which, together with the crystals of calcium hydrosulfoaluminates, quickly grow together to form a colloidal dispersed shell around cement hydrates. The disadvantage of glycerol as a modifying agent for concrete mixes is that the addition of glycerol leads to an increase in the strength of concrete only after its steaming.

From the above document US 2009/0197991 A1, the use of polyacrylamide in a concrete mixture is known. It can be assumed that, when a polyacrylamide solution is introduced into the concrete mixture, the polymer forms a spatial phase network, which leads to the formation of a coagulation structure in the mixture that ensures the thixotropic properties of the mixture. At the same time, due to the fact that the structure is formed due to weak physical forces, it is easily destroyed when mechanical loads are applied to the mixture; therefore, the viscosity of the mixture does not increase during transportation. Thus, the introduction of polyacrylamide into the concrete mixture prevents the concrete from dripping off the vertical surface, but at the same time does not cause a change in the cone precipitation.

At the same time, partial saponification of amide groups occurs in polyacrylamide, the resulting carboxyl groups react with calcium hydroxide, located on the surface of cement grains. This interaction leads to the immobilization of relict cement grains, this makes it difficult to connect them into large globules, which is directly related to the strength of the formed concrete stone. Some of the carboxyl groups of the polyacrylamide react with calcium hydroxide dissolved in water, while the polymer's diphilicity sharply increases and, consequently, its surface activity increases. It can be assumed that it is the presence of such a polymer in the concrete mix that leads to a significant increase in its adhesive strength.

Polyester is used in the method of preparing a concrete mixture (SU 1065370), according to which the adhesive composition "Octopus-9" is introduced into the mixture in an amount of 0.1-0.5% by weight of cement. The strength of concrete stone increases. This adhesive composition consists of an unsaturated complex polyester resin, modifier, initiator and polymerization accelerator. When introduced into the concrete mixture, polymerization of this composition does not occur. It can be assumed that the main active ingredient of the composition is a polyester resin. So, if, when a polyester resin was introduced into the concrete mixture, an increase in the strength of the formed concrete stone was noted, the addition of other ingredients that are part of the Sprut-9 adhesive composition (initiators and polymerization accelerators, modifiers, etc.) to the resin, led to its decrease durability.

The mechanism of the effect of esters on the mechanical properties of concrete is as follows. The ester groups in the oligomers, upon contact with the surface of glass, concrete and some other alkaline materials, hydrolyze and chemisorption of the hydrolysis products on the surface of the solid occurs, and these processes proceed at a very high speed. (R.A. Veselovsky, V.N. Kestelman. Adhesion of Polymers, McGraw Hill, New-York, 400p; Adamson A.W. Physical Chemistry of Surfaces, third edition (John Willey and Sons, New York), p. 134.). When a limited amount of ester oligomer is introduced into the concrete mixture, it will chemisorb on the surface of the cement grains. The amount of introduced oligomer should be such that it fills only part of the grain surface, while it acquires a mosaic structure consisting of alternating hydrophilic-hydrophobic sites. In this case, the aggregation of cement grains will cause not the formation of large globules, relatively weakly connected with each other, but fibrils, the structure of the concrete stone in this case will be a system of interpenetrating fibrillar networks.

Tests of concrete samples made from concrete mix were carried out using each of the components of the complex additive separately and all their possible combinations. For the test, concrete samples were made - beams 4 × 4 × 16 cm. Portland cement of grade 400 and sand in a ratio of 1: 3 were used to prepare the samples. The amount of each component of the additive based on the mass of cement is indicated in the table.

The composition of the additive Bending Strength, MPa Adhesive Strength, Concrete-Steel, MPa Adhesive Strength, Concrete, MPa №№ The amount of glycerin
% The number of PAA,% The amount of polyester,% Type of polyester one - - - - 5,4 0.9 0.3 2 0,07 - - - 5,4 0.9 0.3 3 0.2 - - - 5.5 0.9 0.3 four 0.5 - - - 5.5 1,0 0.4 5 0.6 - - - 5.3 0.8 0.3 6 - 0,025 - - 5,4 0.9 0.4 7 - 0.1 - - 5.7 1,0 0.5 8 0.125 - - 5,4 0.9 0.4 9 - - 0.1 Polydiethylene glycol maleate phthalate 6.3 1.9 2.1 10 - - 0.5 Polydiethylene glycol maleate phthalate 6.9 2.1 2.1 eleven - - 0.7 Polydiethylene glycol maleate phthalate 5.5 1.3 1.4 12 - - 0.01 Polyethylene Glycol Isophthalate 5.3 0.9 0.3 13 - - 0.02 Polyethylene Glycol Isophthalate 5.4 0.9 0.3 fourteen - - 0.05 Polyethylene Glycol Isophthalate 5,4 1,2 0.4 fifteen - - 0.1 Polyethylene Glycol Isophthalate 6.1 1,6 1.9 16 - - 0.5 Polyethylene Glycol Isophthalate 7.0 2.1 2.2 . 17 - - 0.7 Polyethylene Glycol Isophthalate 5,4 1.4 1,5 eighteen 0.2 - 0.5 Polydiethylene glycol maleate phthalate 6.8 2.0 2.2 19 - 0.1 0.3 Polyethylene glycol maleate 6.3 3.0 3.2 twenty 0.05 0,025 - - 5.3 1,2 0.4 21 0.1 0,025 - - 6.1 1.3 0.8 22 0.2 0.02 - - 5.5 1.3 0.6 23 0.2 0,025 - - 6.2 1.4 0.9 24 0.2 0.1 - - 7.2 2.1 2.0 25 0.2 0.175 - - 5,6 2.0 2.1 26 0.5 0.1 - - 6.7 2.0 2,3 27 0.6 0.01 - - 5,4 1,2 1,0 28 0.2 0.1 0.3 Polydiethylene glycol maleate phthalate 9.2 3.2 2.4 29th 0.2 0.1 0.5 Polydiethylene glycol maleate phthalate 7.9 3,1 2.6 thirty 0.2 0.1 0.3 Polyethylene glycol maleate phthalate 7.7 3.2 2,3 31 0.2 0.1 0.3 Polyethylene glycol maleate 6.2 2.9 3.0 32 0.2 0.1 0.3 Polycondensation product of hydroxypropylated diphenylolpropane with maleic anhydride 8.9 3.1 3.3 33 0.2 0.1 0.3 Polydiethylene glycol fumarate 6.9 3,1 2,8 34 0.2 0.1 0.3 Poly 1,2-propylene glycol adipate 7.4 3.0 2.5 35 0.2 0.1 0.3 Polydiethylene Glycol Chlorormaleinate 7.6 3.0 2.7 36 0.2 0.1 0.01 Polyethylene Glycol Isophthalate 7.5 2.5 2.1 37 0.2 0.1 0.02 Polyethylene Glycol Isophthalate 7.7 2.5 2.1 38 0.2 0.1 0.05 Polyethylene Glycol Isophthalate 7.8 2,8 2.7 39 0.2 0.1 0.1 Polyethylene Glycol Isophthalate 8.0 3.0 2.7 40 0.2 0.1 0.3 Polyethylene Glycol Isophthalate 8.1 3,1 2.9 41 0.2 0.1 0.3 Polyethylene Glycol Isophthalate 8.0 3.2 2.9 42 0.2 0.1 0.3 Polyethylene Glycol Isophthalate 8.1 3,1 2.9

Example 1 shows the performance of the concrete mixture without additives, the table below shows the performance of the concrete mixture using: only glycerol in examples 2-5, only polyacrylamide (PAA) in examples 6-8, only polyester in examples 9-17 , glycerol and polyester in Example 18, polyacrylamide and polyester in Example 19. In the remaining examples, the use of the complex additive according to the invention is presented, moreover, in examples 20-27 a two-component additive is presented, and in examples 28-42 a three-component additive .

The complex additive according to the invention was made either by simple mixing of its components, taken in the amounts indicated in the table, based on the amount of cement, or by mixing the same components, but with the introduction of polyacrylamide in the form of a 2.5% solution in water.

The concrete mixture was prepared in two ways.

In the first method, cement grade 400 and sand, taken in a 1: 3 ratio, were first mixed, and then the resulting mixture was mixed with a complex additive. Before the manufacture of concrete beam samples, the resulting mixture was closed with water (water-cement ratio was 0.65) and mixed. It is clear to the skilled person that the ratio of cement to sand, cement grade and water-cement ratio may be different.

In the second method of manufacturing a concrete mixture, cement and sand taken in the same ratio were first mixed, the required amount of water with a complex additive was mixed, and then the mixture of cement and sand was mixed with a mixture of water and a complex additive.

The concrete mixture obtained using the complex additive according to the invention had a cone draft of between 4.5 and 5.5 cm.

Hardening of concrete was carried out at 20 ° C. Testing of the images was carried out 28 days after their preparation. To carry out adhesive tests, a layer of concrete mixture 10 mm thick was applied to the surface of a concrete or metal plate and covered with a plastic film. After 28 days, a metal fungus was glued to the hardened concrete layer, the hardened concrete extending beyond the perimeters of the fungus was removed and the tear-off force was determined on the adhesiometer. Bending tests of the samples were carried out on a UMM-20 hydraulic press. The test results are presented in the table.

As can be seen from the table, the concrete strength (bending) without additives is 5.4 MPa (example 1), one additive gives a maximum value of concrete strength of 7.0 MPa (example 16), if the additive is a polyester. In this case, the increase in concrete strength is 1.6 MPa. Two-component additives not covered by the invention (examples 18, 19) give worse results. When using a two-component additive glycerol-polyacrylamide according to the invention, the concrete strength of 7.2 MPa is achieved (Example 28), that is, a strength increase of 1.8 MPa. When using a three-component additive glycerol-polyacrylamide-complex polyester achieved concrete strength of 9.2 MPa (example 28), that is, an increase in strength of 3.8 MPa. As you can see, there is a pronounced synergy - the increase in strength exceeds the sum of the gains realized with the introduction of each component individually or in combinations not covered by the invention.

In addition, as indicated in the aforementioned document SU 624896, the disadvantage of glycerol as a modifying agent of the concrete mixture can be attributed to the fact that the addition of glycerol leads to an increase in the strength of concrete only after its steaming. The use of glycerin together with the polyacrylamide according to the invention does not require steaming of concrete to increase its strength.

It should also be noted that even a very low content in the complex additive of polyester leads to an increase in the strength of concrete stone.

Claims (6)

1. A complex additive for a concrete mixture comprising cement and sand containing glycerin, characterized in that it contains polyacrylamide in the following ratio of components: 50-96 wt.% Glycerol and 4-50 wt.% Polyacrylamide. 2. The complex additive for concrete mix according to claim 1, characterized in that it further comprises a polyester in the following ratio of components: 50-63 wt.% Glycerol, 7-12 wt.% Polyacrylamide and 32-45 wt.% Polyester . 3. The complex additive for the concrete mixture according to claim 2, characterized in that it contains polyethylene glycol maleate phthalate, polydiethylene glycol maleate phthalate, polytriethylene glycol maleate phthalate, polyethylene glycol maleate or a condensation product of hydroxypropylated diphenylene polypropylene, polyethylene glycol propylene glycol adipate, polydiethylene glycol chlorormaleinate or polyethylene glycol isophthalate. 4. A concrete mixture comprising cement, sand and a complex additive, characterized in that the complex additive contains 0.1-0.6% glycerol and 0.025-0.1% polyacrylamide with respect to the mass of cement. 5. The concrete mixture according to claim 4, characterized in that the complex additive further comprises a polyester with the following content of components with respect to the mass of cement: 0.1-0.6% glycerol, 0.025-0.1% polyacrylamide and 0.01 -0.5% polyester. 6. The concrete mixture according to claim 5, characterized in that the complex admixture as polyester contains polyethylene glycol maleate phthalate, polyethylene diethylene glycol maleate phthalate, polyethylene glycol maleate phthalate, polyethylene glycol maleate or a condensation product of hydroxypropylated diphenylene glycol polyethane, polyethylene glycol , polydiethylene glycol chloromaleinate or polytriethylene glycol isophthalate.