RU2421423C2 - Nanomodified concrete and preparation method thereof - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to construction materials and can be used to make articles from nanomodified concrete in civil and industrial construction. The nanomodified concrete contains portland cement, glauconitic sand, superplasticiser C-3 and water, and the nanomodifying additive is silica sol obtained by titrating citric acid with a mother solution, with the following ratio of components in wt %: portland cement 18.65-22.93; glauconitic sand 74.53-68.8; said additive 0.005-0.02; superplasticiser C-3 0.18-0.23; water - the rest. Method of producing nanomodified concrete involves mixing portland cement, glauconitic sand and 2/3 water, followed by addition of superplasticiser C-3, mixed with the remaining amount of water and said additive.

EFFECT: high ultimate compression strength and reduced water absorption of concrete.

2 cl, 2 tbl, 1 ex

Description

The invention relates to building materials and can be used for the manufacture of concrete products, both in civil and in industrial construction.

Known raw mix for the manufacture of concrete, containing cement, sand and water (Bazhenov Yu.M. Concrete technology. M: Publishing house ASV, 2002. - S.274-275).

Fine-grained concrete based on this raw material mixture has a reduced compressive and bending strength and increased porosity.

Known raw mix for the manufacture of fine concrete, including Portland cement 19.00-20.00, sand 58.80-61.92, water, aluminum powder 0.024-0.025, surfactant SDB 0.009-0.01, sodium sulfate 0, 24-0.25, spent catalyst for isoprene production 1.56-4.68 and water (Patent 2198861).

The disadvantages of this mixture for fine-grained concrete are: low compressive strength, low density, a large number of components (7 pieces) that reduce the uniformity of the mixture, as well as the complexity of its manufacture.

The closest in technical essence to the claimed invention is fine-grained concrete, consisting of Portland cement, glauconite sand, water, superplasticizer C-3 and a filler - ground glauconite sand (Positive decision on patent application No. 2008103138/03 (003432) dated February 16, 2009 .).

The disadvantages of this technical solution are the low compressive strength, the loss of activity of the filler - ground glauconite sand during storage and, therefore, lower strength of concrete.

The objective of the invention is to develop a composition and method for producing nanomodified concrete with high strength and low water absorption.

The solution to the problem is achieved by the fact that concrete, including Portland cement, glauconite sand, S-3 superplasticizer and water, contains a silicic acid sol as a nanomodifying additive, in the following ratio, wt.%:

Portland cement 18.65-22.93 Glauconite sand 74.53-68.8 Nanomodifying additive 0.005-0.02 Superplasticizer S-3 0.18-0.23 Water Rest

The silicic acid sol is obtained by titration with citric acid. A method of producing nanomodified concrete is obtained by mixing Portland cement, glauconite sand and 2/3 of water, followed by the addition of C-3 superplasticizer mixed with a solution of silicic acid sol.

Glauconite sand (phosphate rock dressing) is a greenish loose material of the following chemical composition,%: SiO ₂ - 90.1; Al ₂ O ₃ - 1.3; Fe ₂ O ₃ - 2.2; FeO - 0.4; TiO ₂ 0.15; CaO - 2.0; MgO - 0.3; K ₂ O + Na ₂ O - 1.2; P ₂ O ₅ - 1.4; SO ₃ - 0.4; F is 0.13; p.p.p. - 0.42.

The introduction of superplasticizer C-3 allows you to increase the mobility of the concrete mixture, reduce the water-cement ratio.

Nanoparticles are obtained by the condensation method using sol-gel technology. In the interaction of a dilute solution of sodium silicate with citric acid, a new amorphous phase is released with the formation of a silica sol.

Nanomodifying additive consists of SiO ₂ , sizes 5-10 nm, which have tremendous kinetic energy and are active centers of crystallization. Entering into the chemical reactions of SiO ₂ , it provides the formation of crystalline intergrowths of low-basic calcium hydrosolicates instead of primary crystalline hydrates such as Portlandite and highly basic calcium hydrosolicates, which contributes to an increase in density and strength due to the filling of the micropore space with crystalline intergrowths.

The use of a solution of silicic acid sol as an nanoadditive, introduced into an aqueous solution of C-3 superplasticizer, provides a total effect, which manifests itself in increased compaction and hardening of the structure of the formed artificial stone, the result of which is an increase in strength in the design age under compression by more than 1, 5 times and a decrease in water absorption by 20%.

The claimed combination of essential features exhibits a new property, which provides an increase in the hydration activity of the components of the concrete mixture at a lower W / C ratio and the formation of a structure with tight packaging.

Thus, the formation of a dense structure due to the plasticizing effect and, as a consequence, a decrease in mixing water, an increase in the hydration activity of the components of the concrete mixture, made it possible to obtain nanomodified concrete, which is characterized by increased compressive strength, bending and reduced water absorption.

Example. Portland cement grade 400 is mixed in a dry state with technogenic glauconite sand and 2/3 parts of water.

Superplasticizer C-3 is dissolved in the rest of the water, mixed and a silica sol (with a mother liquor) is added. All is mixed and poured into a concrete mixture of Portland cement, glauconite sand and water. Prepared beam forms measuring 40 × 40 × 160 mm are lubricated with machine oil, filled with prepared concrete mixture, vibrated for 5 s and placed in a bath with a hydraulic shutter at a temperature of 20 ± 2 ° C and a relative humidity of 95-100%. Samples were tested after 3 and 28 days of hardening.

The compositions and test results are presented in tables 1, 2.

Table 1 Example The composition of concrete, wt.% Portland cement Glauconite sand Filler ground glauconite sand with S = 350 m ² / kg Silicic acid gel (SiO ₂ in terms of dry matter) S-3 Water Prototype 18.0 68.1 2.0 - 0.2 11.7 one 22.94 68.81 - - 0.23 8.01 2 22.98 68.95 - 0.02 - 8.05 3 18.65 74.53 - 0.02 0.18 6.62 four 22.93 68.80 - 0.005 0.23 8,035 5 22.93 68.80 - 0.01 0.23 8.03 6 22.93 68.80 - 0.02 0.23 8.02 7 22.93 68.79 - 0,03 0.23 8.03 Note: the prototype uses Portland cement PC 500-DO.

table 2 Indicators Compositions Prototype one 2 3 four 5 6 7 The compressive strength after 3 days, MPa - 9.1 7.9 10.1 10.3 12.9 14,4 12.1 The compressive strength after 28 days, MPa 18.9 16,4 15.3 23.5 24.8 28.6 30.9 27.1 Water absorption,% 2.9 6.5 6.9 2,8 4.3 2.5 2,4 2.9

From table 2 it is seen that with these ratios of the components of the concrete mixture and the method of obtaining a technical result is achieved.

The proposed raw material mixture according to this invention provides for obtaining nanomodified concrete, which differs from the prototype in increased compressive strength (1.5-1.6 times) and reduced water absorption by 20%.

The claimed invention is industrially applicable and can be used in industrial and civil engineering.

Claims (2)

1. Nanomodified concrete obtained from a mixture containing Portland cement, sand, C-3 superplasticizer, a nanomodifying additive in the form of sol and water, characterized in that the mixture as a nanomodifying additive contains a silicic acid sol obtained by titration of citric acid with a mother liquor, and as sand - glauconite sand, in the following ratio of components, wt.%:
Portland cement 18.65-22.93 Glauconite sand 74.53-68.8 Specified Additive 0.005-0.02 Superplasticizer S-3 0.18-0.23 Water Rest 2. A method of producing nanomodified concrete, comprising mixing Portland cement, glauconite sand and 2/3 of water, followed by the addition of C-3 superplasticizer mixed with the remaining water and the specified additive.