RU2793093C1 - Raw mixture for compressed gypsum products and method of manufacturing thereof - Google Patents

Abstract

FIELD: construction materials.

SUBSTANCE: group of inventions relates to the field of production of building materials and can be used in production of gypsum products. Raw mixture for pressed gypsum products contains, in % by weight: gypsum binder obtained by firing of phosphogypsum at a temperature of 175^оC, 64-72, filler - phosphogypsum with a particle size of not more than 112 mcm, 8-16, the rest is 0.5% aqueous solution of Penostrom foam agent. A method for manufacturing pressed gypsum products from the above mixture includes mixing phosphogypsum with a gypsum binder, introducing the resulting raw mixture into the 0.5% solution of foam agent, mixing, moulding in moulds with plastic inner surface under a pressure of 2 MPa with holding at the specified pressure for 30 s, pressing out and drying the products in natural conditions to permanent weight.

EFFECT: increase in the strength of products, reduced consumption of a binder, lower energy costs for pressing and metal consumption, higher surface quality of products.

2 cl, 3 tbl, 1 ex

Description

The present invention relates to the field of production of building materials and can be used in the production of gypsum products.

A known method and composition for the manufacture of gypsum products, while wet natural dihydrate gypsum or citrogypsum is mixed with sulfuric acid, and then sequentially with dry quicklime and mixing water, then the resulting raw mixture is pressed while removing excess mixing water (Patent RU No. 2132310 C1 , published 06/27/1999).

The disadvantage of this method is the complexity of the process of manufacturing products, high costs for their production, as well as low water resistance of products, low strength.

Also known is a method and composition for the manufacture of gypsum products, which consists in using expanded perlite (fine aggregate) with a granule size of 75-100 microns, which is pre-saturated with water, filtering out water not retained by expanded perlite granules, mixing water-saturated perlite with gypsum, serving the resulting mixture into a mold for further pressing and pressed at a pressure of at least 10 MPa (Patent RU No. 2525412 C1, publ. 10.08.2014, bull. No. 22).

The main disadvantages of this composition and method are low strength, high water-binding (water-gypsum) ratio; the presence of additional operations associated with the need for water saturation and filtration of water from perlite. Also, with this technological solution, it is difficult to ensure a constant water-gypsum ratio, this is due to the neglect of the weight of perlite, as well as the fact that filtration does not ensure complete removal of water from the surface of perlite, and when it is dosed, free moisture will remain on all equipment involved in this operation. . The fluctuation of the water-gypsum ratio has a negative impact on ensuring the constancy of the strength characteristics of the final products.

The technical solution closest to the proposed invention, taken as a prototype, is the composition and method of manufacturing gypsum products, which consists in the fact that fine aggregate is a waste product of perlite production (perlite dust with a granule size of 5-100 microns, a bulk density of 75 kg/m ³ ) mixed with water, followed by the introduction of a modified gypsum binder obtained by roasting citrogypsum in a rotary kiln at a temperature of 120-140 ^° C, with a specific surface of 600-650 m ² /kg and molded under a pressure of 10 MPa, with keeping the products at the specified pressure 30 sec (Patent RU No. 2693808 (C1), published: 04.07.2019 Bull. No. 19).

The main disadvantages of this composition and method are low strength, increased energy costs for pressing and metal consumption (metal molds); the need to use perlite dust, which increases the cost of raw materials associated with its purchase and transportation; the high content of gypsum binder in the mixture, which increases the cost of products, also the low content of filler (perlite) in the mixture (1.5%) does not provide products with high surface quality, high adhesion of the gypsum binder to the metal mold contributes to the formation of defects on the surface of products in the form of delaminations and wedges, limited raw material base of citrogypsum.

The invention is aimed at increasing the strength of products, reducing the consumption of a binder, the cost of raw materials, energy costs for pressing, reducing the metal consumption of production, improving the quality of the surface of products, expanding the raw material base.

This is achieved by the fact that the raw mix for pressed gypsum products contains a binder, a filler, while gypsum binder obtained by roasting phosphogypsum at a temperature of 175 ^° C is used as a binder, phosphogypsum with a particle size of not more than 112 microns is used as a filler, and 0. 5% aqueous solution of foaming agent "Penostrom", pressing out of products is carried out in molds with a plastic inner surface at the following mass ratios of raw materials,%:

gypsum binder - 64-72;

phosphogypsum - 8-16;

the specified 0.5% solution of the foaming agent - the rest.

A method for producing gypsum stone includes preparing a molding mass, molding, pressing out, drying, while preparing the molding mass is carried out in the following sequence: preparing a raw mixture by mixing a binder and a filler, preparing a foaming agent solution, adding a raw mixture to a foaming agent solution, mixing, molding in molds with a plastic inner surface under a pressure of 2 MPa, with keeping the products at the specified pressure for 30 seconds, pressing out and drying in natural conditions to a constant weight.

Characteristics of the materials used.

1. Filler - waste from the production of fertilizers from phosphorite rock - phosphogypsum, with a particle size of not more than 112 microns. The chemical composition of phosphogypsum is presented in table 1.

Table 1

The chemical composition of phosphogypsum

Content of oxides, % SO ₃ CaO SrO _{P2O5 _} CeO ₂ MgO rest 48.84 46.44 2.52 0.68 0.36 0.15 1.01

2. Gypsum binder - calcined phosphogypsum with a specific surface area of 350-400 m ² /kg.

Gypsum binder is obtained by firing phosphogypsum at a temperature of 175 ^o C.

3. Foaming agent "Penostrom". The characteristics of the foaming agent are presented in table 2.

table 2

Characteristics of foaming agent Penostrom

Indicators Values Density at 20 ^o C, kg / m ³ within - 1020-1090 Hydrogen index (pH) 1% aqueous solution within - 7.5-10.0 Kinematic viscosity, at 20 ^o C, mm ² s ^-1 no more - 40 Pour point, ^o C no higher, minus - 3 Foam stability, s not less than - 240 Foam ratio at least - 4

4. Water GOST 23732-2011 “Water for concrete and mortar. Specifications".

The developed compositions of the raw mixture and the strength characteristics of the studied composition of products and the prototype are shown in table 3.

Table 3

Compositions of the raw mix and physical and mechanical characteristics

investigated pressed gypsum products

Product type Material consumption % wt. Water binder
attitude Pressing pressure, MPa Ultimate compressive strength 2 hours after pressing, MPa Tensile strength at
compression of dry products, MPa Gypsum binder Perlite dust Phosphogypsum 0.5% foaming agent solution research composition No. 1 72 - 8 20 - 2 16 29 study composition No. 2 64 - 16 20 - 2 13 25 prototype 83 1.5 - 15.5 0.18-0.19 10 15-16 19-20

Example (table 3 composition No. 2): phosphogypsum in the amount of 1.6 kg (16% by weight) and gypsum binder in the amount of 6.4 kg (64% by weight) are mixed until a homogeneous mass is obtained. Next, the resulting raw mixture is poured into a 0.5% aqueous solution of a foaming agent, taken in an amount of 2 l (20% by weight), followed by thorough mixing until a homogeneous molding mass is obtained. After that, the resulting molding mass is sent to a mold with a plastic inner surface and pressed under a pressure of 2 MPa, the duration of holding under the specified pressure is 30 seconds, then it is pressed out and dried in natural conditions to a constant weight.

The developed method for manufacturing products with the proposed ratio of components, the presence of a foaming agent solution and a mold with a plastic inner surface in the system contributes to the maximum and uniform compaction of the molding sand. The low adhesion of the mold material to the molding mass and the additional effect of using a foaming agent provide products with a high surface quality, and also contribute to an increase in the density of the gypsum stone and, as a result, its strength at low pressing pressures.

The introduction of phosphogypsum into the composition of the raw mix also helps to reduce the cost of the product by reducing the consumption of gypsum binder and the costs associated with the purchase and transportation of perlite dust.

Based on the fact that phosphogypsum is a waste, the accumulation of which, unlike citrogypsum, is ubiquitous throughout the world, this invention also makes it possible to significantly reduce the burden on the environment and expand the raw material base of the regions.

The use of the specified pressure (2 MPa) and the molding mode of products helps to reduce energy costs. The use of a mold with a plastic inner surface and low pressing pressure significantly reduces the metal intensity of production, low adhesion of the mold material to the molding mass allows you to abandon lubricants, which reduces the duration of the process due to the elimination of this operation, and also reduces the costs associated with purchasing lubricants.

Reducing the pressing pressure below 2 MPa and increasing the content of the filler (phosphogypsum) in the system above 16% contributes to a decrease in the average density of products and, as a result, strength, below the strength values of the prototype. At the same time, an increase in pressing pressure above 2 MPa and a decrease in the content of the filler (phosphogypsum) increase the energy costs for production and the cost of raw materials - gypsum binder. With the complete exclusion of phosphogypsum and foaming agent, defects appear on the surface of the product.

Increasing the concentration of the foaming agent above 0.5% does not improve the physical and mechanical (average density, strength) characteristics of products, but negatively affects their cost.

Claims (3)

1. Raw mixture for pressed gypsum products containing a binder, filler and foaming agent solution, characterized in that the raw mixture contains gypsum binder obtained by roasting phosphogypsum at a temperature of 175 ° C, as a filler - phosphogypsum with a particle size of not more than 112 microns , 0.5% aqueous solution of foaming agent "Penostrom", the preparation of the mixture is carried out at the following mass ratios of raw components,%: gypsum binder 64-72 phosphogypsum 8-16 specified 0.5% foaming agent solution rest 2. The method of manufacturing pressed gypsum products according to claim 1, including the preparation of a molding mass, molding, pressing out, drying, characterized in that the preparation of the molding mass is carried out in the following sequence: mixing phosphogypsum with a gypsum binder, introducing the resulting raw mixture into 0.5% foaming agent solution, mixing, molding in molds with a plastic inner surface under a pressure of 2 MPa, keeping the products at the specified pressure for 30 s, pressing out and drying in natural conditions to a constant weight.