BG3539U1 - Two-dimensional inclusion nano-reinforced concrete - Google Patents

Abstract

The utility model relates to concrete, containing up to 1/10 of its binding component (cement) binder, based on kaolin clay, which represents a geopolymer of the silico-aluminate family with a composition, expressed as oxides, as follows: 1/3х Li2О 2/3х K2O: Аl2O3: у SiO2: z H2O, where in fully hydrated form "z" is a value greater than 0 and at most equal to 5, "y" is a value in the range 3 to 4, and "x" is a value in the range 1 to about 1.5. These mineral polymers necessarily contain kaolin, which is a source of Аl2O3 and SiO2, but its content in the geopolymer nano-reinforcement is not limited to this. The composition represents a mixture of solid solutions, as one phase is potassium-lithium polysilicate with the formula: (1/3х-1) Li2O: (2/3х-1) K2O: (у-2) SiO2: (z-1) Н2O and the second phase of potassium-lithium polysialate polymer. The sources of the elements are not necessarily limited to oxide forms, as in this case of lithium, the hydroxide form is preferred. In the composition must be present Kaolin (kaolinite), which has a dual role. Kaolin is a 1:1 aluminosilicate, composed of connected planes with structure of tetrahedral silicon atoms and octahedral aluminium atoms. The single layers (nano-sized thickness) are connected to each other by hydrogen bonds. In an alkaline environment, the zeta potential (electrical potential at the slipping plane) decreases and reaches strongly negative values, which allow the exfoliation of the kaolin crystal to individual layers with a thickness of the nanometre range. For this purpose, the hydrogen bonds holding the kaolin crystal (secondary structure) must be weakened and this is possible through the presence of lithium cations, which have a small diameter and intercalate between the layers, with which separating them from each other and leading to the dissociation of the secondary crystal structure. The thus obtained layers, in addition to participating in the formation of a mineral polymer, also act as internal nano-sized reinforcement (huge specific surface area), increasing the compressive strength of ready-mixed concrete products. The binding action is due to the formation of mineral polymers in the reaction between silico-aluminates and alkalis in an aqueous medium, i.e. it is an unevadable artefact of the medium required for the intercalation and exfoliation of kaolin clay to nano-sized in situ reinforcement in the concrete composition.

Description

Field of technology

The present utility model belongs to the field of concretes and in particular to concretes with high reinforcing strengths and in particular those with polymer reinforcement.

BACKGROUND OF THE INVENTION

Concrete compositions have been known to mankind since the time of the Roman Empire. Concretes, like steel, are constantly evolving and fine-tuning.

Technical essence of the utility model

The present utility model relates to a composition of concrete reinforced with nano-sized inclusions resulting from the stratification of three-dimensional secondary crystals in the concrete composition, which act as internal reinforcement preventing the appearance and spread of cracks leading to the destruction of the material. Nano-reinforcement is obtained in situ, i. within a crosslinking reaction, which guarantees its dispersion and the possibility of homogenization.

The nano-reinforcement of concrete is achieved within the process of production of geopolymer, which after complete crosslinking falls into the classification of zeolite. Numerous patents and other references describe methods for preparing zeolites and molecular sieves. DV Breck's book, Zeolite Molecular Sieves, published by Interscience in 1974, is a textbook. In general, syntheses of silicoaluminate gels in strong or highly concentrated aqueous alkalis are carried out by the hydrothermal route. The mixture of reagents, containing a large excess of water, is sealed in a container at constant pressure and temperature. Preferably the pressure is atmospheric and the temperature is in the range of about 25 ° C to 125 ° C. The reaction lasts more than ten hours until crystallization of the products occurs. These products are very porous and have poor mechanical properties, even when agglomerated with a binder and contain an aggregate, i. are included in the composition of concrete.

The utility model relates essentially to a concrete composition which is nano-reinforced with two-dimensional concrete inclusions and containing from 1/100 to 1/10 of its bonding component a silico-aluminate mineral polymer compound obtained by polycondensation of a reagent mixture which has composition, expressed as oxides, as follows: 1/3 x Li ₂ O 2/3 x K ₂ O: A1 ₂ O ₃ : y SiO ₂ : z H ₂ O, where in fully hydrated form "ζ" is a value of greater than 0 and at most equal to 5, "y" is a value in the range 3 to 4, and "x" is a value in the range 1 to about 1.5. This mineral polymer necessarily contains kaolin, which is a source of A1 ₂ O ₃ and SiO ₂ , but its content in the geopolymer nano-reinforcement is not limited to this, but aims to be leafy to two-dimensional nano-reinforcement in situ in the composition of concrete according to the utility model to which it is added at an initial stage, i.e. this part of the binder is mixed and prepared before the addition of other components such as water, aggregate, sand and cement. The composition is a mixture of solid solutions, one phase being potassium lithium polysilicate with the formula: (l / 3x-1) Li ₂ O: (2 / 3x-1) K ₂ O: (y-2) SiO ₂ : (z -1) H ₂ O and the second phase of potassium-lithium polysialate polymer.

Thus, according to the utility model, the composition is a mixture of solid solutions, one phase being potassium-lithium polysilicate with the formula: (l / 3x-1) Li ₂ O: (2 / 3x-1) K ₂ O: (y-2 ) SiO ₂ : (z-1) H ₂ O and a second phase potassium-lithium polysialate polymer.

The amounts of reagents for this part of the binder preferably follow the ratio (K ₂ O + Li ₂ O) / A1 ₂ O ₃ in the range from about 1 to 1.5 and the ratio SiO ₂ / A1 ₂ O ₃ is in the range from 3 to 4. Higher ratios cause a phase of free potassium or lithium silicate in hardened concrete and cause migration of potassium or lithium silicate, which can disrupt the physical and mechanical properties of the resulting concrete products. The source of SiO ₂ and A1 ₂ O ₃ must be kaolin clay, with the remainder of the SiO ₂ in proportion being supplied by other minerals such as diatomaceous earth. The content of a lithium compound with an alkaline reaction is obligatory, preferably lithium hydroxide. The alkaline reaction of the solution minimizes the zeta potential of kaolinite, and lithium cations intercalate between the layers of kaolinite and lead to its decomposition into two-dimensional nano-sized crystallites, serving as internal

3148 Descriptions to utility registration certificates № 04.2 / 30.04.2020 reinforcement. The geopolymer reaction is an artifact of the composition and pH of the medium, and the correction of the silica content aims to prevent undesirable physicochemical consequences of SiO ₂ deficiency and to expand the action of the mixture and as a binder, i. binder in the composition of concrete, where it provides the presence of nano-sized two-dimensional reinforcing agents - layers of chemically exfoliated in situ kaolinite.

The sequence of mixing steps to obtain this mineral polymer compound and nano-reinforcement involves mixing aluminosilicate oxide (kaolinite) and diatomaceous earth in a mixer. The mixing of potassium and lithium hydroxide can be done by mixing the alkalis in water is polysilicate (diatomaceous earth) and then adding this solution to the aluminosilicate oxide. Preferably, the mixing of the aluminosilicate oxide is aqueous polysilicate precedes the addition of alkalis which are introduced by means of an aqueous solution. The reagent mixture thus obtained is stable and retains its reactivity even after long periods of storage. In addition, this mixture is easy to handle and store. Maturation of the mixture lasts from 1 to 4 hours at room temperature, during which time the kaolinite will undergo chemical stratification in situ to a two-dimensional nano-sized viscous mixture. After the maturation stage, the mixture is introduced into the concrete composition without the need to modify its composition. The effect of the inclusion of two-dimensional nano-sized layers in the composition of concrete is its strengthening.

Example

The following example illustrates a method of preparing a nano-reinforced concrete containing a nanosized reinforcing agent obtained in situ according to the present utility model.

860 g of reagent mixture containing 11.33 [mu] g are prepared. water, 1.1 sho1 potassium hydroxide, 0.5 sho1 lithium hydroxide, 4.46 sho1 silicon dioxide and 1,081 sho1 aluminum trioxide. The source of aluminum trioxide is entirely kaolinite (calculated as 1: 1 silicon dioxide and aluminum trioxide). The residue of silica was added as diatomaceous earth. The hydroxides mentioned above are dissolved and mixed in the water. The remaining components are mixed until a homogeneous dry mixture in a blender. The alkaline solution was added to the mixture and the two components were mixed in a blender.

The stirred mixture was then removed and stored in a PE sealed container during maturation at room temperature for 4 hours. From the composition thus obtained, a 60 g aliquot was taken for X-ray diffraction analysis, which confirmed the presence of nano-sized two-dimensional layers of kaolinite and identified the geopolymer two-phase structure.

The rest of the mixture is added as a filler to the reference concrete mixture without corrections to the water-cement ratio, ie. mechanically added as a fine aggregate and mix the remaining components of the concrete composition in a blender. The weight ratio of the reinforcement in the concrete mixture is 1/10 of the weight of the cement mixture. Numerous test blocks were made and tested to check the strength characteristics of the obtained concrete on the 7th and 28th day, as well as reference values for non-reinforced concrete were compared, ie. standard. Surprisingly, a statistically significant increase in the bending strength (+ 7%) and pressure (+ 22%) of the reinforced concrete compared to that of the standard was found, as well as a reduction in the scatter of values for the strengths, ie. the test specimens of the reinforced concrete have indicators in (44%) a narrower range around the average value.

Claims (2)

Claims A nano-reinforced concrete composition comprising water, aggregate, sand and a binder comprising cement, characterized in that the binder further comprises a lithium compound and kaolinite and diatomaceous earth, such as 1/100 to 1/10 of the total weight of the binder is formed in situ mineral geopolymer from the group of silico-aluminates with a composition expressed as oxides, as follows: 1/3 x Li ₂ O 2/3 x K ^ O: A1 ₂ O ₃ : y SiO ₂ : z H ₂ O, wherein "x" is a number from 1 to 1.5; "Y" is a number between 3 and 4; and "ζ" is a number greater than 0 and at most 5. Composition according to Claim 1, characterized in that the lithium compound is lithium hydroxide.