RU2766258C1 - Portland cement with mineral additives - Google Patents

Abstract

FIELD: chemistry; construction.SUBSTANCE: invention relates to compositions of cements and can be used to produce concrete mixtures and mortars used at enterprises for production of prefabricated reinforced concrete and concrete mixing units. Essence of the invention consists in the fact that Portland cement with mineral additives includes Portland cement clinker, TPS slag, chamotte-kaolin powder, limestone, gypsum dihydrate and a chemical additive in the form of superplasticizer C3, in the following ratio of components, wt.%: Portland cement clinker (PCC) — 63–75; gypsum dihydrate (DG) — 4.4–5.3 (in terms of SO3); TPS slag — 5–10; chamotte-kaolin powder (CKP) — 2.5–7.5; limestone (L) — 13–14; chemical additive — superplasticizer C-3 — 0.1–0.2.EFFECT: increased ultimate compressive strength in early hardening period due to introduction of two types of mineral additives (chamotte-kaolin powder and limestone) into the composition of Portland cement and reduced water demand of Portland cement due to introduction of chemical additive (superplasticizer C-3).1 cl, 2 dwg, 5 tbl

Description

The invention relates to the composition of cements and can be used for the manufacture of concrete mixtures and mortars used in enterprises for the production of prefabricated concrete and concrete mixing units.

The composition of Portland cement is known (see RU 2496728 C1, C04B 7/52, C04B 7/52, publ. 27.10.2013), containing Portland cement clinker, gypsum dihydrate and an additive. Sodium fluoride is used as an additive. The composition of Portland cement includes, wt. %:

Portland cement clinker 95.93–98.77 gypsum dihydrate 0.50–1.92 sodium fluoride rest

A mixture of Portland cement with a mineral additive is known (see RU 2476391 C1, C04B 7/02, C04B 7/02, publ. 27.02.2013). As a mineral additive, natural wollastonite with a particle size of less than 40 microns is used in the following ratio of components, wt. %:

Portland cement 85–95 natural wollastonite mechanically activated 10–15

The closest technical solution is the composition of Portland cement (see RU 2460699 C1, C04B 7/02, C04B 7/02, publ. 09/10/2012), containing the following components, wt. %:

unfired dolomite (ND) 5.0–15.0 blast-furnace granulated slag (DGSh) 5.0–15.0 Portland cement clinker (PCC) 75.0–77.5 gypsum dihydrate (DG) 2.5–5.0

The most significant disadvantage of the known composition of Portland cement is the use of unfired ground dolomite, belonging to the class of carbonates with the chemical composition CaCO ₃ ·MgCO ₃ , since in this case it may contain harmful magnesium oxide MgO, which causes uneven volume changes. In addition, the content of magnesium oxide is limited to no more than 5% in Portland cements of any type, this mineral additive is not provided for by the GOST 31108-2016 standard “General construction cements. Specifications”, and also has an increased water demand in comparison with ground limestone (CaCO ₃ ).

The objective of the present invention is to obtain Portland cement with lower water demand and increased compressive strength in the early stages of hardening.

The essence of the invention lies in the fact that Portland cement with mineral additives, including Portland cement clinker, TPP slag, chamotte-kaolin powder, limestone, gypsum dihydrate and a chemical additive in the form of C3 superplasticizer, in the following ratio, wt. %:

Portland cement clinker (PCC) 63–75 gypsum dihydrate (DG) 4.4–5.3 (in terms of SO ₃ ) TPP slag 5–10 fireclay-kaolin powder (PShK) 2.5–7.5 limestone (I) 13–14 chemical additive - superplasticizer C-3 0.1–0.2

The technical result is obtained by introducing two types of mineral additives into the composition of Portland cement (fireclay-kaolin powder and limestone), which allows the formation of calcium carboaluminates during hydration, which in turn increase the compressive strength in the early stages of hardening, and the chemical additive - ( superplasticizer C-3) reduces the water requirement of Portland cement.

For experimental verification of the proposed composition, several compositions of Portland cement with additives were developed and tested, which are shown in table 1.

Table 1

Consumption of Portland cement components with mineral additives

No. Consumption of materials, % PCC DG TPP slag PShK AND Chem. S-3 additive one 60–80 3.5–5.5 4–11 2.0–8.3 10–15 0.1–0.2 2 63–75 4.4–5.3 5–10 2.5–7.5 13–14 0.1–0.2 3 63–75 4.4–5.3 5–10 2.5–7.5 10–15 0.1–0.2 4 63–75 4.4–5.3 5–10 2.5–7.5 13–14 0.1–0.2 5 60–80 3.5–5.5 4–11 2.0–8.3 10–15 0.1–0.2

Characteristics of the original components :

1. Binder: Portland cement obtained by joint grinding in a laboratory ball mill of clinker and gypsum stone to a specific surface of 320 m ² /kg;

The chemical and mineralogical composition of the binder is presented in Table 2.

table 2

Chemical and mineralogical composition of the binder

Chemical composition, % Mineralogical
compound, % MgO _{SiO2 Al2O3 _ Fe2O3 _} CaO SO ₃ RFP _R2O C ₃ S β-C ₂ S C ₃ A _C4AF cement clinker 1.22 23.69 4.06 5.06 64.61 0.48 0.66 0.22 58.61 25.15 6.3 9.94

Physical and mechanical properties of the binder are presented in table 3.

Table 3

Physical and mechanical properties of the binder

Name Specific surface area,
m ² /kg Normal density, % Setting time, h-min Activity, MPa Start the end R _out R _szh CEM I 314 26.5 0-45 3-40 6.4 52.5

2. Chemical additive: chemical modifier - superplasticizer S-3 (TU 2481-001-51831493-00). A naphthalene-formaldehyde-based product in the form of a water-soluble brown powder or a dark brown aqueous solution with a concentration of at least 32%. Manufacturer - TPO "Universal Concrete" (Russia, Stavropol Territory, Lermontov).

According to GOST 31108-2016 “General construction cements. Specifications” for cements, organic or inorganic materials are used as special and technological additives. The amount of organic additives in a dry state should not exceed 0.2% by weight of cement.

3. Mineral supplements

- dihydrate gypsum (DG)

- TPP slag;

- fireclay-kaolin powder (PShK).

- limestone (I).

To obtain cement with mineral additives, the following mineral additives were used, which are by-products of various industries. The chemical composition of mineral additives is presented in table 4.

Table 4

The chemical composition of mineral additives

Content of oxides, % Additive name PShK TPP slag AND _SiO2 50.67 55.66 3.73 _{Al2O3 _} 34.20 22.40 0.44 _{Fe2O3 _} 1.13 15.00 0.63 _TiO2 0.71 0.75 0.03 CaO 5.11 2.10 50.90 MgO 0.69 1.60 1.99 _{P2O5 _} 0.03 0.07 0.40 _K2O 0.32 2.26 0.14 _Na2O 0.14 0.78 0.08 SO ₃ <0.1 <0.01 0.12 RFP 6.62 0.02 41.50

3.1 Chemically pure gypsum dihydrate consists of 32.5% CaO, 46.5% SO ₂ and 21% H ₂ O. Gypsum dihydrate is a soft mineral, its hardness on the Mohs scale is 2. The color of the mineral approaches white (depending on the type , the presence and amount of impurities can be gray, yellowish-brown). The supplier is Mineral-Khors LLC, Voronezh.

3.2 The glass phase contains a sufficiently large amount of crystalline compounds in the form of minerals akermanite (d = 0.309; 0.287 nm), gelenite (d = 0.285; 0.243; 0.219 nm), merwinite (d = 0.268; 0.265 nm) and other compounds. In this case, the total content of crystalline phases is 33.3%.

TPP slags are formed at high temperatures as a result of the physical and chemical interaction of the components of the initial solid materials (fuel, ore and floodplain) and the gaseous medium. Basically, TPP slag is represented by a glassy phase, without any crystalline inclusions.

3.3 Analysis of chamotte-kaolin powder is illustrated by drawings, where in Fig. 1 – X-ray diffraction pattern of chamotte-kaolin powder, fig. 2 - IR spectra of a sample of chamotte-kaolin powder.

X-ray phase analysis of chamotte-kaolin powder samples showed the presence of a significant amount of kaolinite mineral in the sample, as evidenced by diffraction reflections (d = 0.277; 0.256; 0.248; 0.233; 0.199; 0.189; 0.178; 0.166; 0.148 nm).

The presence of crystalline β -quartz (d = 0.424; 0.357; 0.334; 0.245; 0.231; 0.212; 0.181; 0.154 nm) and a small amount of α -quartz (d = 0.230; 0.220 nm) were noted. The diffraction pattern also contains lines of the mineral tricalcium aluminate (d = 0.270; 0.220; 0.189 nm).

According to infrared spectroscopy, the presence of a significant amount of the kaolinite mineral was noted in the PSC sample, as evidenced by the lines on the spectrogram in the region 1115-1110, 1035, 1010 cm ^-1 - stretching vibrations of the Si - O (Si) and Si - O bonds; 940 and 915 cm ^-1 - deformation vibrations of structural hydroxyl minerals associated with Al ³⁺ cations; 545 cm ^-1 - mixed deformation Si - O and stretching Al - O (H) vibrations; 470 and 430 cm ^-1 - deformation Si - O vibrations; 3695-3700, 3665-3670, 3620-3625 cm ^-1 - stretching vibrations of structural hydroxyl groups.

Thus, using X-ray phase and IR spectral analyzes, it was found that chamotte-kaolin powder is represented by such crystalline phases as kaolinite, β and α -quartz, as well as the tricalcium aluminate mineral. It is logical to assume that the PSC should contain a significant amount of X-ray amorphous metakaolinite formed during the dehydration of the original kaolinite. This means that metakaolinite and tricalcium aluminate will determine the hydraulic activity of chamotte-kaolin powder. A significant effect on the hydration processes of Portland cement with the addition of PSHK should also be expected from the kaolinite mineral.

3.4. Limestone (I) is a natural stone material of white-gray-yellow color. The deposit is Pravoberezhnoye. It is located in the Krasnodar Territory, Labinsk District, on the right bank of the river. Malaya Laba, 4 km east of the railway. station Shedok. The chemical composition is shown in table 4.

The compositions were made as follows:

For all compositions, the value of normal density was determined, after which prism samples were molded with dimensions of 4 × 4 × 16 cm according to GOST 30744-2001 “Cements. Test methods using polyfractional sand. The data obtained (table 5) indicate that the ultimate compressive strength, determined at the age of two days of normal hardening on prism samples, is within the standard values according to GOST 31108-2016 “General construction cements. Specifications” for cements and correspond to a strength class of at least 42.5B (compressive strength, MPa, not less than 20 and 42.5 at the age of 2 and 28 days, respectively).

The compressive strength values for the developed composition are higher than those of other similar compositions.

Table 5

Compositions of Portland cement

No. Portland cement composition, % Ultimate compressive strength at the age of 2 days of hardening, MPa Normal density of cement paste NG, % PCC DG DGSh TPP slag PShK AND ND C-3 one 60 5.5 - eleven 8.3 15 - 0.2 12.1 25 2 63 5.3 - 10 7.5 14 - 0.2 21.2 23 3 70 5 - eight 5 11.9 - 0.1 8.1 26 4 75 4.4 - 5 2.5 thirteen - 0.1 20.8 23 5 78 5.9 - 4 2 10 - 0.1 13.8 24 EN 2460699 75.0 3.5 10 - - - 11.5 - 9.8 27

The development of Portland cement compositions with mineral additives based on industrial waste has been carried out. The area of optimal values in the dosages of mineral additives has been determined, and it has also been established that the introduction of chamotte-kaolin powder in combination with ground limestone has a significant effect on increasing the compressive strength of cement stone in the early stages of hardening, and the introduction of the chemical modifier C-3 reduces the water demand of Portland cement .

Claims (2)

Portland cement with mineral additives, including Portland cement clinker, TPP slag, chamotte-kaolin powder, limestone, gypsum dihydrate and a chemical additive in the form of C3 superplasticizer, in the following ratio, wt. %: Portland cement clinker (PCC) 63–75 gypsum dihydrate (DG) 4.4–5.3 (in terms of SO ₃ ) TPP slag 5–10 fireclay-kaolin powder (PShK) 2.5–7.5 limestone (I) 13–14 chemical additive - superplasticizer C-3 0.1–0.2

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