RU2802732C2 - Nanomodified cement of low water demand - Google Patents

Abstract

FIELD: hydraulic binders; cements.

SUBSTANCE: nanomodified cement with low water demand includes 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 dressing tailings, cullet, brick battle, expanded clay or glass expanded clay dust; barite; organic water-reducing agent - a superplasticizer taken from the group: alkali and/or alkaline earth metal salts of the condensation product of naphthalenesulfonic acid with formaldehyde or condensation product of melamine-containing resins with formaldehyde or complex salts of alkaline earth metals and sulphuric 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 components, pts. wt.: Portland cement 50-100; mineral silica filler 0-50; barite 0.5-20 by weight of Portland cement; superplasticizer in terms of dry matter 0.3-3.0. The method for producing nanomodified cement with low water demand consists in joint grinding of Portland cement or its mixture with mineral silica filler, barite and superplasticizer, preliminary grinding is carried out: Portland cement in an amount of 0.5-50% of its total mass, barite all the required quantity 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 m²/kg.

EFFECT: nanomodified cement with low water demand.

2 cl, 1 tbl

Description

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

Patent sources

1. Patent RU No. 2373163 C1, 05.15.2008, C04B 7/00, 7/52

2. Patent RU No. 2656270 C1, 04/17/2017, C04B 7/52, 7/13.

These disadvantages are to a lesser extent characteristic of the known method (prototype) for producing a low-water-demand binder 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 terms of silica, by joint grinding of Portland cement or its mixture with a mineral filler and superplasticizer, characterized in that Additionally, a siliceous nanomodifier is used, a dry mixture is first prepared by thoroughly mixing 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 of its total mass and nanomodifier, or a solution of the mixture is prepared by thoroughly mixing Portland cement or its mixture with a mineral filler, taken in an amount of 0.5-5% of its total mass, the entire solution of superplasticizer and nanomodifier, then the prepared 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 Portland cement or its mixture with a mineral filler and their final grinding is carried out to obtain cement of low water demand (LCW) to a specific surface of 5500-7500 cm ² /g. [2] However, in the production 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 concrete and mortars based on CNM.

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

The problem is solved by the composition of cement with low water demand, containing, as in the prototype, Portland cement and a superplasticizer, in contrast to the prototype TsNV in accordance with the invention, instead of a siliceous nanomodifier, it additionally contains barite, with 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 CNM (using silica filler taken from the group: granulated blast furnace slag, fly ash, ore tailings, cullet, volcanic ash, pumice, tuff, quartz sand, feldspar sand, grains from granite crushing, broken bricks, expanded clay or glass expanded clay dust, etc.) from 0 to 50 wt. parts, instead of the same part of Portland cement.

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

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

To prepare low water demand CNM we used:

- Portland cement grade CEM I 42.5N produced by Eurocement LLC in accordance with GOST 31108-2016

- Quartz sand according to GOST 8736-2014 with the largest particle size 1.2 mm

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

- 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 naphthalene sulfonic acid “SP-1” according to TU 5870-002-58042865-03 (as amended 1, Poliplast LLC)

- Synthetic siliceous product - silica sol "Leixil 20-HS" (STC Compass LLC) with a particle size of less than 100 nm

- Mineral siliceous filler (granulated blast furnace slag, fly ash, volcanic ash, pumice, tuff, quartz sand, feldspathic sand, grains from granite crushing, ore tailings, glass waste, brick waste, expanded clay or glass expanded clay dust, etc.) is used for 1-2% humidity.

Low water demand CNM was obtained as follows:

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

If a liquid superplasticizer is used, the 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 siliceous filler is added, and grinding is carried out to a specific surface of 450-700 m ² /kg.

After preparing the CNM, tests were carried out (see Table 1). Specific density was determined using a PSH-12 device, bending and compressive strength - according to GOST 310.4.

Setting times were determined according to GOST 310.3, water-cement ratio, cone spreading, activity after 1 day of normal hardening, activity after steaming, activity after 28 days of normal hardening - according to GOST 310.4. The grade 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 CNM due to an increase in the mechanochemical effect when using barite. It has been established that barium sulfate compounds are activators of PC hardening, which is explained by the acceleration of the hydration of Portland cement minerals. Using X-ray phase analysis, it was determined that in the presence of BaSO ₄ the residual reflections of tricalcium silicate and ettringite decrease, but the reflections of calcium hydrosilicate increase. The addition of barium oxide has a similar, but less significant effect. 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 BaSO ₄ , which accelerates hydration.

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

Claims (2)

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, feldspathic sand, screenings from granite crushing, tailings ore dressing, cullet, brick scrap, expanded clay or glass expanded clay dust; barite; organic water-reducing reagent - superplasticizer taken from the group: salts of alkali and/or alkaline earth metals of the condensation product of naphthalene sulfonic acid with formaldehyde or the 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 the number of carbon atoms 3-5; with the following ratio of components, wt. parts: Portland cement 50-100; mineral silica filler 0-50; barite 0.5-20 by weight of Portland cement; 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 or its mixture with a mineral silica filler, barite and superplasticizer, pre-grinding: Portland cement in the amount of 0.5-50% of its total mass, all barite the required consumption of superplasticizer is 0.1-10% of its total mass, after half an hour of grinding, add the remaining components, including, if necessary, a mineral silica filler, and grind to a specific surface of 450-700 m ² /kg.