WO2023048595A1

WO2023048595A1 - Nano-modified cement with low water demand

Info

Publication number: WO2023048595A1
Application number: PCT/RU2022/000291
Authority: WO
Inventors: Максим Хусенович БАКОВ
Original assignee: Максим Хусенович БАКОВ
Priority date: 2021-09-24
Filing date: 2022-09-26
Publication date: 2023-03-30

Abstract

A nano-modified cement with a low water demand includes ingredients in the following proportions: Portland cement in an amount of 50-100 parts by weight, a mineral silica filler in an amount of 0-50 parts by weight, barite in an amount of 0.5-20 of the mass of Portland cement, and an organic water-reducing superplasticizer in an amount of 0.3-3.0 parts by weight on a dry basis. The following may be used as the superplasticizer: alkaline and/or alkaline-earth metal salts of a naphthalene sulfonic acid-formaldehyde condensate or of a melamine resin-formaldehyde condensate, or complex salts of alkaline-earth metals and sulphuric acid and/or nitric acid and/or formic acid and/or acetic acid and low-molecular weight saccharides having 3-5 carbon atoms. A method of producing the claimed nano-modified cement includes co-milling Portland cement or a mixture thereof with a mineral silica filler, barite and a superplasticizer, wherein preliminary grinding is carried out on 0.5-50% of the total mass of Portland cement, the entire amount of barite and 0.1-10% of the total mass of the superplasticizer. After grinding for half an hour, the remaining ingredients are added, including a mineral silica filler if necessary, and milling is carried out to a fineness of 450-700 m²/kg.

Description

CEMENT NANOMODIFIED (TSNM) LOW WATER DEMAND

The invention relates to the technology of building materials, mainly to the production of hydraulic binders, namely cements.

From the level of technological achievements, a method is known for the manufacture of cement with reduced water demand by joint grinding of Portland cement (PC), a mineral filler and an organic water-reducing agent, where a carbonaceous material with a proportion of calcium carbonate of at least 60 wt.% is used as a mineral filler to a specific surface of 400-700 m ² /kg at the following ratio of components, wt.%: Portland cement 50-70, carbonate-containing material 40-50, organic water-reducing agent superplasticizer 0.3-3.0 over 100%. [1] The main disadvantages of this technical solution include increased water demand, as well as low strength of the resulting cement stone.

Patent Sources:

1. Patent RU No. 2373163 C1, May 15, 2008, C04B 7/00, 7/52

2. Patent RU No. 2656270 C1, April 17, 2017, C04B 7/52, 7/13

These shortcomings are less characteristic of the known method (prototype) for the manufacture of a binder of low water demand from the following components, mass parts: Portland cement 50-100, mineral filler 0-50, superplasticizer in terms of dry matter 0.3-3.0, silica modifier 0.000004-0.0001 in in terms of silica, by joint grinding of Portland cement or its mixture with a mineral filler and a superplasticizer, characterized in that a silica nanomodifier is additionally used, a dry mixture is preliminarily prepared by thorough mixing of Portland cement or its mixture with a mineral filler, taken in an amount of 0.5-5% of the total mass , 0.1-5% of superplasticizer powder from its total mass and nanomodifier, or prepare a solution of the mixture by thoroughly mixing Portland cement or its mixture with mineral filler, taken in an amount of 0.5-5% of its total mass, the entire solution of superplasticizer and nanomodifier, then prepare the resulting dry mixture is combined with the rest of the Portland cement or its mixture with a mineral filler and the rest of the superplasticizer, or the specified prepared solution is mixed with the rest of the Portland cement or its mixture with a mineral filler and their final grinding is carried out until a low-grade cement is obtained.

CORRECTION SHEET (RULE 91) ISA/RU water demand (TsNV) to a specific surface of 5500-7500 cm ² /g. [2] However, in the manufacture of these cements, the main disadvantage of the compositions and, consequently, the method of their preparation is the relatively low strength properties of nanomodified cement (CNM).

The objective of the invention is to increase the strength of the resulting cement stone and, consequently, to increase the strength of concretes and mortars based on TsNM.

The technical result of the introduction of barite is to reduce the water demand of the cement matrix and the formation of a more durable cement stone due to sulfate - barium ions.

The problem is solved by the composition of cement of low water demand, containing, as in the prototype, Portland cement and superplasticizer, in contrast to the prototype TsNV in accordance with the invention, instead of silica nanomodifier, it additionally contains barite, in the following ratio of components, mass parts: Portland cement 100; superplasticizer 0.3 -3.0; barite 0-20 instead of the same part of Portland cement, and in the production of composite TsNM (using a silica filler taken from the group: granulated blast-furnace slag, fly ash, ore dressing tailings, cullet, volcanic ash, pumice, tuff, quartz sand, feldspar sand, screenings from granite crushing, brick breakage, expanded clay or glass expanded clay dust, etc.) from 0 to 50 parts by mass, instead of the same part of Portland cement.

The problem is also solved by the method of obtaining TsNM, in which, at the beginning, joint grinding of a part of Portland cement with barite and a superplasticizer is carried out, and then, after a half-hour grinding, the remaining amount of PC and superplasticizer, as well as, if necessary, a mineral silica filler, and final grinding is carried out to 450-700 m ² / kg.

Depending on the commodity form of the superplasticizer, it can be used in the form of a powder or solution with a concentration of 20-40%.

For the preparation of CNM low water demand used:

- Portland cement brand CEM I 42, 5N produced by Eurocement LLC in accordance with GOST 31108-2016

- Quartz sand according to GOST 8736-2014 with the largest fineness of 1.2 mm

- Granulated blast-furnace slag of the Novolipetsk Metallurgical Plant quality factor -1.69 of the first grade according to GOST 3476-2019

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CORRECTION SHEET (RULE 91) ISA/RU - Barite concentrate KB-5, barium sulfate content 86%, true density 4200 kg/m ³ according to GOST 4682-84

- Organic water-reducing reagent superplasticizer (powder) based on naphthalenesulfate acid "SP-1" according to TU 5870-002-58042865-03 (as amended 1, Poliplast LLC)

- Synthetic silica product - silica sol "Laxil 20-XC" (OOO STC "Compass") with a particle size of less than 100 nm

- Mineral siliceous filler (granular blast-furnace slag, fly ash, volcanic ash, pumice, tuff, quartz sand, feldspar sand, screenings from granite crushing, ore dressing tailings, cullet, brick cullet, expanded clay or glass expanded clay dust, etc.) is used when 1-2% humidity.

Low water demand CNM was obtained as follows:

In the case of using a powdered superplasticizer, Portland cement (0.5-50% of the total mass), superplasticizer (0.1-10% of the total mass) and the entire required consumption of barite are first ground together. After half an hour of grinding, the remaining components are added (including, if necessary, a mineral silica filler) and grinding is carried out to a specific surface area of 450-700 m ² /kg.

In the case of using a liquid superplasticizer, barite is thoroughly mixed with a concentrated solution of the entire superplasticizer. Then Portland cement is introduced and, after half an hour of mixing, if necessary, a mineral silica filler, and grinding is carried out to a specific surface area of 450-700 m ² /kg.

After preparing the CNM, tests were carried out (see Table 1). The specific density was determined on a PSKh-12 instrument, and the flexural and compressive strength was determined according to GOST 310.4.

The setting time was determined according to GOST 310.3, water-cement ratio, cone flow, activity after 1 day of normal hardening, activity after steaming, activity after 28 days of normal hardening - according to GOST 310.4. The brand of cement was determined according to GOST 10178.

The results of the tests (Table 1) confirm an increase in the true density of cement, a decrease in water demand and an increase in the strength of the resulting cement stone and cement-sand mortar. This result is associated with an improvement in the characteristics of the CNM due to an increase in the mechanochemical effect at

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CORRECTION SHEET (RULE 91) ISA/RU using barite. It has been established that barium sulfate compounds are hardening activators of PC, which is explained by the acceleration of hydration of Portland cement minerals. Using X-ray phase analysis, it was determined that in the presence of BaSO4, the residual reflections of tricalcium silicate and ettringite decrease, but the reflections of hydrocalcium silicate increase. A similar but less significant effect is exerted by the addition of barium oxide. This effect is explained by a decrease in the pH of the mixing water from 12.26 to 11.97 in the presence of BaO and to 11.75 with BaSC, which contributes to the acceleration of hydration.

For the first time, the influence of barium sulfate on the stability and strength characteristics of individual clinker phases has been determined. It has been established that barium sulfate has the maximum positive effect on cement strength due to the formation of an increased proportion of calcium hydrosilicates. This provides an increase in the strength of the cement stone.

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CORRECTION SHEET (RULE 91) ISA/RU table 1

Characteristics of TsNM of low water demand, made according to the present invention, in comparison with the control cement (CEM 142.5 N without SP-1) and with TsNV according to the prototype

Notes:

1) The amount of SP-1 is the same and is 1.5 mass parts from Portland cement (PC).

2) The ratio in the cement-sand mortar C/P=1/3.

3) R izg - bending strength,

R szh - compressive strength.

Claims

CLAIM

1. Nanomodified cement (CNM) of low water demand, including Portland cement or its mixture with a mineral silica filler taken from the group: granulated blast-furnace slag, fly ash, volcanic ash, pumice, tuff, quartz sand, feldspar sand, screenings from granite crushing, ore beneficiation tailings, cullet, brick cullet, expanded clay or glass expanded clay dust, etc.; barite; organic water-reducing agent (superplasticizer) taken from the group: salts of alkali and/or alkaline earth metals, condensation product of naphthalenesulfonic acid with formaldehyde or condensation product of melamine-containing resins with formaldehyde, or complex salts of alkaline earth metals and sulfuric and/or nitric and/or formic and/or acetic acids and low molecular weight saccharides with 3-5 carbon atoms; with the following ratio of the components of the mass. parts: Portland cement 50-100; mineral silica filler 0-50; barite 0.5-20 by weight of Portland cement, in excess of the total weight; superplasticizer in terms of dry matter 0.3-3.0.

2. The method for producing nanomodified cement with low water demand according to claim 1, obtained by joint grinding of Portland cement (PC) or its mixture with mineral silica filler, barite and superplasticizer, preliminary grinding is carried out: Portland cement (PC) in an amount of 0.5-50% of its total mass, barite, all the required consumption and superplasticizer 0.1-10% of its total mass, after half an hour of grinding, the remaining components are added, including, if necessary, a mineral silica filler, and grinding is carried out to a specific surface of 450-700 m ² /kg.

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CORRECTION SHEET (RULE 91) ISA/RU