CN115849846A - Surface plastering gypsum and preparation method thereof - Google Patents
Surface plastering gypsum and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the field of building materials, and provides surface plastering gypsum and a preparation method thereof, wherein the surface plastering gypsum is prepared from the following raw materials in parts by weight: 65-85 parts of modified gypsum powder; 10-15 parts of diatomite; 3-5 parts of heavy calcium carbonate; 5-10 parts of talcum powder; 0.2-0.5 parts of retarder; 0.1-0.4 part of water-retaining agent; 0.2-0.8 part of water reducing agent; 1-2 parts of redispersible latex powder; the modified gypsum powder is obtained by adjusting the pH value of building gypsum fine powder to 8-10 by using lime calcium. The surface plastering gypsum provided by the invention does not select gypsum sources, and all performance parameters meet the requirements of national standards; the prepared surface plastering gypsum has reasonable gradation, good plastering construction performance, higher whiteness and fine luster, can effectively reduce the phenomena of powder falling, falling and cracking, has lower cost and is beneficial to market popularization.
Description
Technical Field
The invention relates to the technical field of building materials, in particular to surface plastering gypsum and a manufacturing method thereof.
Background
In building construction, plastering gypsum is a novel leveling material which develops rapidly in recent years, is prepared by adding admixture, additive and the like into gypsum, and is widely applied to leveling and decorating building interior walls and roofs. The main chemical component of the gypsum is calcium sulfate hydrate, which is an industrial material and a building material with wide application; the plastering gypsum has good workability, fluidity, water retention, heat preservation and insulation performance and proper fireproof performance in building engineering. Therefore, the plastering gypsum is a wall plastering and leveling material with good material performance, construction performance and use function, and is applied to industrial and civil buildings.
For example, chinese patent publication No. CN 110436868A discloses a machine-sprayed surface layer plastering gypsum, which adopts phosphogypsum, curing agent, water, retarder and water-retaining agent which are subjected to neutralization, calcination, aging and curing treatment, and is uniformly mixed to obtain plastering gypsum powder, mainly solving the problem that the plastering gypsum cannot be mechanically constructed. The plastering gypsum which is developed rapidly in recent years is mainly light plastering gypsum prepared by doping lightweight aggregate such as vitrified micro bubbles and the like, and is rapidly accepted by the market due to light weight, high coating rate, simple and convenient construction and the like; however, the light plastering gypsum is mainly leveled by a bottom layer, and a surface layer still needs to be finely leveled by scraping putty, white and the like.
The surface plastering gypsum which is mainly part of desulfurized gypsum and is sold in the market at present adopts a large amount of titanium dioxide to improve the whiteness of powder, and has higher cost. Therefore, the market still needs a surface plastering gypsum which is simple and convenient to manufacture, good in construction performance and low in cost.
Disclosure of Invention
The invention aims to: the surface plastering gypsum has good material performance, excellent construction performance, simple and convenient manufacture and lower cost.
The invention provides a surface plastering gypsum which is prepared from the following raw materials in parts by weight:
65-85 parts of modified gypsum powder, which is obtained by adjusting the pH value of building gypsum fine powder to 8-10 by using lime calcium;
10-15 parts of diatomite;
3-5 parts of heavy calcium carbonate;
5-10 parts of talcum powder;
0.2-0.5 parts of retarder;
0.1-0.4 part of water-retaining agent;
0.2-0.8 part of water reducing agent;
1-2 parts of redispersible latex powder;
the mesh number of the building gypsum fine powder is below 20 meshes.
Preferably, the modified landplaster is obtained by modifying: firstly, grinding the calcined building gypsum into powder with the specific surface area of 2500-6000cm 2 And/g, removing large particles by using a 10-mesh and 20-mesh powder selection screen, grinding into fine powder, adjusting the pH value of the fine powder to 8-10 by using ash calcium powder, and optionally adding white cement.
Preferably, the raw material of the building gypsum fine powder is one or more of natural gypsum, desulfurized gypsum and phosphogypsum.
Preferably, the diatomite is ground diatomite with the fineness of 425 meshes; the ground calcium carbonate is selected powder with the fineness of 80-100 meshes; the fineness of the talcum powder is 325 meshes.
Preferably, the water retaining agent is hydroxypropyl methyl cellulose ether, and the weight part is 0.15-0.3 part.
Preferably, the water retaining agent is hydroxypropyl methyl cellulose ether with the viscosity of 60000-100000mPa.s.
Preferably, the retarder is a bone collagen retarder; the water reducing agent is a polycarboxylic acid water reducing agent.
Preferably, the water retention rate of the surface layer plastering gypsum is 90-95%, and the application whiteness is more than 73%.
The invention provides a method for preparing the surface plastering gypsum, which comprises the following steps:
adjusting pH of the building gypsum fine powder with a particle size of less than 20 meshes to 8-10 by using lime calcium, and cooling to obtain modified gypsum powder;
weighing the raw materials according to the proportion, mixing the modified gypsum powder, the diatomite, the ground limestone and the talcum powder for 30-60s, sequentially adding the weighed retarder, the water-retaining agent, the redispersible latex powder and the water-reducing agent in the mixing process, and stirring and mixing for 2-3 minutes to obtain the surface layer plastering gypsum.
Preferably, the stirring speed during the mixing process is 130-150rpm; the surface plastering gypsum is applied by mechanical spraying.
Compared with the prior art, the surface plastering gypsum provided by the invention is prepared from the following raw materials in a certain proportion: 65-85 parts of modified gypsum powder, 10-15 parts of diatomite, 3-5 parts of heavy calcium carbonate, 5-10 parts of talcum powder, 0.2-0.5 part of retarder, 0.1-0.4 part of water-retaining agent, 0.2-0.8 part of water reducing agent and 1-2 parts of redispersible latex powder; the pH value of the modified gypsum powder is 8-10, and the modified gypsum powder is obtained by modifying building gypsum fine powder with the particle size of less than 20 meshes mainly by using ash calcium. The surface layer plastering gypsum provided by the invention does not select gypsum sources, and all performance parameters meet the requirements of national standards; the prepared surface plastering gypsum has reasonable gradation, good plastering construction performance, higher whiteness and fine luster, can effectively reduce the phenomena of powder falling, falling and cracking, has lower cost and is beneficial to market popularization.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides surface plastering gypsum which is prepared from the following raw materials in parts by weight:
65-85 parts of modified gypsum powder;
10-15 parts of diatomite;
3-5 parts of heavy calcium carbonate;
5-10 parts of talcum powder;
0.2-0.5 parts of retarder;
0.1-0.4 part of water-retaining agent;
0.2-0.8 part of water reducing agent;
1-2 parts of redispersible latex powder;
the modified gypsum powder is obtained by adjusting the pH value of building gypsum fine powder to 8-10 by using ash calcium, and the mesh number of the building gypsum fine powder is less than 20 meshes.
The surface plastering gypsum has good material performance and excellent construction performance, is simple and convenient to manufacture and has lower cost.
In the invention, the surface plastering gypsum takes modified refined gypsum powder as a main raw material, the weight portion of the surface plastering gypsum is 65-85 parts, preferably 68-84 parts, and the pH value is 8-10. The modified gypsum powder of the invention is mainly prepared by using building gypsum fine powder and a certain amount of lime calcium to adjust the pH value of the building gypsum fine powder.
Preferably, the modified gypsum powder is obtained by the following modification mode: drying and calcining a dihydrate gypsum raw material, and controlling 4.8-5.4% of crystal water to prepare calcined building gypsum; firstly, grinding the calcined building gypsum powder by a needle mill and/or a column mill, preferably grinding the building gypsum powder with the specific surface area of 1500-2800 cm 2 The/g is adjusted to 2800-5600cm 2 The coarse particles with the particle size of more than 10 meshes are directly removed and discarded through a powder selecting sieve (10 meshes plus 20 meshes), the coarse particles with the particle size of 10-20 meshes are returned to a grinding machine for continuous grinding, and the fine powder with the particle size of less than 20 meshes passes through and enters the next working procedure; the pH value of the building gypsum fine powder is adjusted to 8-10 by mainly adopting ash calcium powder, white cement is optionally added at the same time, and finally the modified gypsum powder can be cooled to 40-45 ℃ by adopting a cooling device.
In the embodiment of the invention, the modified gypsum powder can adopt industrial by-product gypsum such as desulfurized gypsum, phosphogypsum and the like as raw materials, and can be made of natural gypsum; in addition, 0.02-5 parts by weight of ash calcium is added to adjust the pH value of the building gypsum fine powder in the embodiment of the invention. The invention adopts gray calcium (the main component of calcium hydroxide Ca (OH) 2 ) Adjusting the pH value, more preferably the ash calcium powder usedIs 400 meshes of fineness; compared with the method of adjusting the pH value by using quicklime powder (calcium oxide CaO), although the dosage is slightly more, the dispersing effect is better, the reaction is softer, and the influence of uneven local excessive content on the retarder effect is avoided. In addition, through repeated tests in the embodiment of the invention, the ash calcium powder with the fineness of 400 meshes can sufficiently react to quickly adjust the pH value, and the cost of the ash calcium is not too high due to too small fineness and too small grinding.
In some embodiments, desulfurized gypsum is adopted, the pH value is generally between 6 and 8, and a proper amount of small calcium lime is added; in some examples, phosphogypsum is adopted to prepare gypsum powder, the pH value is about 4.5-6 after pulping, and a little large amount of lime calcium is needed; in other embodiments, the natural gypsum used may be lightly doped with calcium ash. When the whiteness of the calcined gypsum powder is less than 70, partial white cement can be properly added, for example, the adding amount is less than 20 parts by mass, the using amount of dark-color gypsum is reduced, the pH value of the gypsum powder can also be adjusted, the color of the gypsum is partially covered, and the whiteness of the gypsum mortar is improved. The white cement is short for white portland cement, takes calcium silicate as a main component, belongs to an alkaline material, and has high whiteness. Some embodiments of the invention adjust the pH of the powder by using an alkaline material such as white cement or lime calcium.
At present, the surface layer produced in real industrialization is mainly natural gypsum, and the surface layer is partially desulfurized gypsum and the like. Natural gypsum is relatively easy to control, but is increasingly expensive. The industrial by-product gypsum such as phosphogypsum, desulfurized gypsum and the like has relatively concentrated grain composition and contains a plurality of harmful impurities due to the limitation of upstream raw materials. For example, the phosphogypsum is generally 90 μm, the content of the desulfurized gypsum is generally more around 30-60 μm, the distribution curve forms a peak, the gradation is unreasonable, the water requirement of the gypsum is large, the fluidity is poor, the strength is not high, the plastering gypsum product is difficult to directly produce, and particularly, one or more indexes are often unqualified, and the construction property is poor. In the gypsum industry, the most effective and easy industrial production for improving the particle size distribution is grinding modification.
The gypsum powder has many indexes of influence of gypsum modification. After grinding before grinding, the water requirement is reduced, the fluidity is enhanced, the grain gradation is gentle (the grain size distribution is relatively even), the specific surface area is increased, the loose volume weight is reduced, the mechanical properties (the flexural strength and the compressive strength) are improved, and the like. In the application, the modified gypsum powder is applied to plastering gypsum products, and is beneficial to improving the construction property and the like.
In some embodiments of the present invention, the modified landplaster has the following modifications and specifications: calcining gypsum powder by using phosphogypsum in a place, wherein the pH value after calcination is about 4.8, the detected whiteness is 67, the loose volume weight is 650g/L, and the specific surface area is about 2100cm 2 (iv)/g, three-phase composition DH3.16%, HH75.62%, AIII4.18%; after being ground and modified by a ball mill, the mixture is sieved by a vibrating screen with 10 meshes and 20 meshes, and then about 1 to 2.5 parts of ash calcium and 8 parts of white cement are added and mixed evenly; the treated gypsum powder cooled to about 45 ℃ has the pH value of 9.1, the detected whiteness of 70, loose bulk weight of 680g/L and specific surface area of about 3700cm 2 The three-phase composition was DH2.63%, HH77.33%, and AIII2.79%.
In other embodiments of the present invention, the modified landplaster has the following modifications and specifications: calcined gypsum powder of phosphogypsum mixed desulfurization gypsum in a place has the pH value of about 6.1 after calcination, the detected whiteness of 71, the loose volume weight of 680g/L and the specific surface area of about 2300cm 2 The three-phase composition of DH3.45%, HH78.67%, AIII4.81%, through ball mill grinding modification, use 10 mesh +20 mesh vibration sieve to sieve, add about 0.5-1.5 part of gray calcium, mix; the pH value of gypsum powder obtained by modification after treatment and cooling to about 43 ℃ is 8.9, the detected whiteness is 70, the loose volume weight is 710g/L, and the specific surface area is about 3500cm 2 The three-phase composition was DH2.78%, HH81.23%, and AIII2.65%.
In other embodiments of the present invention, the modified landplaster has the following modifications and specifications: calcining gypsum powder of the desulfurized gypsum in a certain place, wherein the pH value of the calcined gypsum is about 6.8, the detected whiteness is 72, the loose volume weight is 730g/L, and the specific surface area is about 1900cm 2 The three-phase composition DH3.81%, HH84.66%, AIII3.88%, through ball mill grinding modification, use 10 mesh +20 mesh vibration sieve to sieve, add about 1-1.5 part of lime-calcium, mix; gypsum powder treated and cooled to about 45 ℃, pH value of 9.2, detected whiteness of 73, loose volume weight of 700g/L and specific surface area of about 4300cm 2 The three-phase composition was DH2.94%, HH86.43%, and AIII2.77%. The gypsum is different from place to place, and the gypsum is taken in this exampleOne class is represented.
In addition, the raw materials for preparing the surface plastering gypsum comprise: 10-15 parts of diatomite, 3-5 parts of heavy calcium carbonate and 5-10 parts of talcum powder, and the particle grading and the like can be optimized, so that the construction performance is improved. The chemical composition of diatomaceous earth is mainly silicon dioxide (SiO) 2 ) Containing a small amount of Al 2 O 3 、Fe 2 O 3 CaO, mgO, etc. and organic matter, the density is generally 1.9-2.3g/cm 3 And has a porous structure. Ground Calcium Carbonate (also known as Ground Calcium Carbonate, GCC), abbreviated as "heavy Calcium", has a sedimentation volume of 1.1-1.9mL/g. The main component of the talcum powder is hydrous magnesium silicate and white or off-white powder. Particularly, aiming at the fact that phosphogypsum usually tends to become grey and dark in color due to oily impurities, diatomite and other porous materials are adopted for physical adsorption, and a series of high-whiteness auxiliary materials such as white cement, talcum powder, ash calcium, heavy calcium and the like are adopted for neutralization and improvement, so that the improvement of the overall whiteness of powder is facilitated.
In the preferred embodiment of the invention, the selected diatomite is ground diatomite with the fineness of 425 meshes, the selected ground diatomite is ground diatomite with the fineness of 80-100 meshes, and the selected talc powder is ground diatomite with the fineness of 325 meshes. The invention preferably selects the fineness of a plurality of auxiliary materials to form a gradient gradation, can exert the loose and porous performance of the diatomite, has strong adsorbability, effectively improves the water retention performance of powder, and has good construction performance, sag resistance and smooth coating.
The raw materials of the surface plastering gypsum comprise the following additive components in parts by weight: 0.2 to 0.5 portion of retarder, 0.1 to 0.4 portion of water-retaining agent, 0.2 to 0.8 portion of water reducing agent and 1 to 2 portions of redispersible latex powder, which is beneficial to improving indexes of slurry fluidity, mechanical property and the like.
In the invention, the water retaining agent is preferably hydroxypropyl methyl cellulose ether, and the weight portion can be 0.15-0.3. The water retaining agent is more preferably hydroxypropyl methyl cellulose ether (HPMC) with the viscosity of 60000-100000mPa.s, and is further preferably hydroxypropyl methyl cellulose ether with the room-temperature viscosity of 100000mPa.s, and a thin coating layer of 1-3mm of surface plastering gypsum can provide a better water retaining effect. Hydroxypropyl methylcellulose is a propylene glycol ether of methylcellulose in which the hydroxypropyl groups and methyl groups are combined by ether linkages with the anhydrous glucose ring of the cellulose, is a white to off-white powder or granule of cellulose having cold water-soluble and hot water-insoluble properties similar to those of methylcellulose. Hydroxypropyl methylcellulose is also named as Chinese: cellulose hydroxypropyl methyl ether; hypromellose, and the like.
In the present invention, the retarder is preferably a bone collagen retarder; the water reducing agent is preferably a polycarboxylic acid water reducing agent. The protein retarder, the polycarboxylic acid water reducer and the redispersible latex powder are all commercially available products, and the embodiment of the application is not particularly limited. Retarders are generally of three types: 1) Alkaline phosphates, mainly including sodium hexametaphosphate and sodium polyphosphate; 2) Protein and amino acid retarders; 3) Organic acid and its soluble salt retarder mainly includes citric acid, sodium citrate, tartaric acid, potassium tartrate, acrylic acid and sodium acrylate, etc. The invention preferably adopts the bone collagen retarder for compounding, and has better effect.
The invention provides a method for preparing the surface plastering gypsum, which comprises the following steps:
adjusting pH of the building gypsum fine powder with a particle size of less than 20 meshes to 8-10 by using lime calcium, and cooling to obtain modified gypsum powder;
weighing the raw materials according to the proportion, mixing the modified gypsum powder, the diatomite, the ground limestone and the talcum powder for 30-60s, sequentially adding the weighed retarder, the water-retaining agent, the redispersible latex powder and the water-reducing agent in the mixing process, and stirring and mixing for 2-3 minutes to obtain the surface layer plastering gypsum.
Wherein the preparation process of the modified gypsum powder is as described above. In the embodiment of the present invention, the order of mixing the raw materials is preferably: firstly, mixing and stirring the modified gypsum powder, the diatomite, the coarse whiting powder and the talcum powder, then sequentially adding the retarder, the water-retaining agent, the redispersible latex powder and the water-reducing agent, stirring, and uniformly mixing to obtain a surface plastering gypsum product.
The blending control of the preferred embodiment of the invention mainly comprises: controlling the quality of gypsum, controlling the total grain composition of powder, controlling the setting time and controlling the evaporation and water loss. The gypsum provides the main mechanical property index of the plastering gypsum, can control the three phases of calcination, increases the content of the active ingredient hemihydrate gypsum as much as possible, and reduces the content of under-burning (residual dihydrate gypsum) and over-burning (anhydrous gypsum); for example, the dihydrate gypsum is high in content and easy to cause poor mechanical property, the anhydrous gypsum is too high and also has poor mechanical property, and apparent cracks, powder falling and the like. The particle size distribution mainly influences the workability of plastering gypsum and is mainly adjusted by grinding modification of gypsum powder and various auxiliary materials (different fineness and passive change). Most of the additives such as retarder, water-retaining agent and the like have the best effect in a weak alkaline environment, so the weak alkaline environment is formed by adding alkaline materials. Among the general additives, the retarder mainly adjusts the setting time, and the water-retaining agent generally provides the water-retaining effect; the addition of talcum powder, water reducing agent, rubber powder and the like can improve the construction effect, and the action of the water reducing agent and the rubber powder is beneficial to the sagging resistance of the powder.
In a specific embodiment of the present invention, the above mixing step is preferably performed in a coulter type stirring mixer; the stirring rate during mixing is preferably 130-150rpm. The time for stirring and mixing the modified gypsum powder, the diatomite, the coarse whiting powder and the talcum powder is preferably 30-60s, and the time for mixing the modified gypsum powder, the diatomite, the coarse whiting powder and the talcum powder by adding the retarder, the water-retaining agent, the redispersible latex powder and the water-reducing agent is preferably 2-3 min.
After the treatment, the surface layer plastering gypsum is obtained and is applied by mechanical spraying. Specifically, the water retention rate of the surface layer plastering gypsum can be 90-95%, and the application whiteness is more than 73%; the mortar is a plastering and fine leveling mortar product with low manufacturing cost and good construction performance.
The plastering gypsum market is competitive, and the requirement on the product is more emphasized on the constructability. Besides economy, construction performance is mainly as follows: the coating is easy to coat and resist sagging when workers are in construction, the shrinkage rate is small, the appearance is uniform and attractive, and the yield is high (the coating area of a product per unit mass is large). The embodiment of the invention mainly provides a plastering gypsum formula which is relatively low in cost, easy to produce and suitable for most industrial by-product gypsum, the basic performance of the plastering gypsum formula meets the national standard and the industrial requirement, and the plastering gypsum formula has better construction performance.
The present invention will be further illustrated by the following examples in conjunction with comparative examples, but the present invention is not limited to the following examples. Wherein, the raw materials are mainly sold in the market. The diatomite is ground diatomite with the fineness of 425 meshes, the heavy calcium carbonate with the fineness of 80-100 meshes and the talcum powder with the fineness of 325 meshes. The bone collagen retarder is a protein retarder of Hebei Shenhui company, the polycarboxylate superplasticizer is a polycarboxylate superplasticizer pc1021 of Suzhou Xingbang company, and the redispersible latex powder is redispersible latex powder Wake 328.
Example 1
1.1 starting materials
Wherein:
the specification of the modified gypsum powder is as follows: the temperature is 45 ℃, the pH value is 9.1, the whiteness is 70, the bulk density is 680g/L, and the specific surface area is about 3700cm 2 The three-phase composition is as follows: DH2.63%, HH77.33%, AIII2.79%. Obtained by the following steps: after the phosphogypsum is calcined and ground and modified by a ball mill, the phosphogypsum is sieved by a 10-mesh and 20-mesh vibrating screen, about 60 parts of undersize powder is mixed with 2 parts of ash calcium and 8 parts of white cement (the trade name is 425, the same as the following example), the mixture is uniformly mixed, and a cooling device is adopted to reduce the temperature of the powder to 45 ℃.
The phosphogypsum calcined gypsum powder (the same as the following examples) has the pH value of about 4.8 after calcination, the detected whiteness is 67, the bulk volume weight is 650g/L, and the specific surface area is about 2100cm 2 The three-phase composition was DH3.16%, HH75.62%, and AIII4.18%.
1.2 preparation:
the feeding is controlled by a screw feeder, modified gypsum powder, diatomite, ground calcium carbonate and talcum powder are respectively weighed by a material scale, and simultaneously the materials are added into a colter mixer to be stirred for 60s, wherein the stirring speed in the mixing process is 130-150rpm (the same as the following embodiment); and meanwhile, sequentially weighing a retarder, 100000mPa.s hydroxypropyl methyl cellulose, a polycarboxylic acid water reducing agent and redispersible emulsion powder by a small scale, adding the mixture into a mixer after stirring for 60s, and continuously stirring for 3min to obtain the surface layer plastering gypsum.
Example 2
1.1 starting materials
Wherein:
the specification of the modified gypsum powder is as follows: the temperature is 43 ℃, the pH value is 8.9, the whiteness is 70, the bulk volume weight is 710g/L, and the specific surface area is about 3500cm 2 The three-phase composition is as follows: DH2.78%, HH81.23%, AIII2.65%. Obtained by the following steps: mixing 50% of phosphogypsum and 50% of desulfurized gypsum in percentage by weight, calcining, grinding and modifying by a ball mill, sieving by a 10-mesh and 20-mesh vibrating screen, adding 1.5 parts of lime calcium into the sieved fine powder by 73.5 parts, uniformly mixing, and reducing the temperature of the powder to 43 ℃ by a cooling device.
Calcined gypsum powder of desulfurized gypsum from some place (same as in the following examples), pH of about 6.8 after calcination, whiteness of 72, bulk volume weight of 730g/L, specific surface area of about 1900cm 2 The three-phase composition was DH3.81%, HH84.66%, and AIII3.88%.
1.2 preparation:
controlling feeding by adopting a screw feeder, weighing modified gypsum powder, diatomite, ground calcium carbonate and talcum powder respectively by using a material scale, and adding the modified gypsum powder, the diatomite, the ground calcium carbonate and the talcum powder into a coulter mixer to stir for 50s; and simultaneously weighing a retarder, 100000mPa.s hydroxypropyl methyl cellulose, a polycarboxylic acid water reducing agent and redispersible latex powder in turn by a small scale, adding the mixture into a mixer after stirring for 50s, and continuously stirring for 3min to obtain the surface layer plastering gypsum.
Example 3
1.1 starting materials
Wherein:
the specification of the modified gypsum powder is as follows: the temperature is 43 ℃, the pH value is 9.2, the whiteness is 73, the bulk volume weight is 700g/L, and the specific surface area is about 4300cm 2 G, three-phase composition: DH2.94%, HH86.43%, AIII2.77%. Obtained by the following method: after the desulfurized gypsum is calcined and is ground and modified by a ball mill, the desulfurized gypsum is modified bySieving with 10 mesh +20 mesh sieve, adding 1 part of calx into the sieved fine powder according to 79 parts, mixing, and cooling to 45 deg.C with cooling device.
1.2 preparation:
controlling feeding by adopting a screw feeder, respectively weighing modified gypsum powder, diatomite, ground calcium carbonate and talcum powder by a material scale, and simultaneously adding the materials into a coulter mixer to stir for 45s; and meanwhile, sequentially weighing a retarder, 100000mPa.s hydroxypropyl methyl cellulose, a polycarboxylic acid water reducing agent and redispersible emulsion powder by a small scale, adding the mixture into a mixer after the 45s stirring is finished, and continuously stirring for 2.5min to obtain the surface layer plastering gypsum.
Comparative example 1
The same procedure as in example 1 was repeated, except that the modification treatment was not carried out on the phosphogypsum-made building gypsum powder in example 1.
The building gypsum obtained by direct calcination has the main indexes: the temperature is 44 ℃, the pH value is 5.8, the whiteness is 68, the bulk density is 670g/L, and the specific surface area is about 3900cm 2 The three-phase composition is as follows: DH3.21%, HH83.65%, AIII2.9%.
Comparative example 2
According to a certain embodiment of the invention patent document 'a method for making plastering gypsum of machine-sprayed surface layer', the plaster is made of phosphorus building gypsum.
Comparative example 3
Some commercially available surface plastering gypsum is made of desulfurized gypsum.
The basic performance of the mechanically sprayed surface layer plastering gypsum obtained in the examples is detected according to the national standard GB/T28627-2012 plastering gypsum, and the results are shown in Table 1.
TABLE 1 Performance results for the topcoat render gypsum obtained in the examples of the invention
The wall whiteness is obtained by smearing a sample on a flat wall, polishing and drying, and then taking part of the smeared surface to test the whiteness. The water consumption and whiteness of the standard consistency are dimensionless and are expressed in percentage.
As can be seen from the test results in Table 1, the parameters of the surface plastering gypsum prepared in the embodiments 1-3 of the invention all meet the requirements of national standard, and the performances are relatively balanced. The applicant finds that each index is not higher and better in multiple research and development experiments, and certain performances such as high index in one-sided pursuit can cause the cost to rise sharply, and in addition, the effect of other indexes can be influenced. Compared with the comparative example, the water consumption for the standard consistency of the embodiment of the invention is less, so that the risks of cracking, hollowing and the like caused by large evaporation capacity are reduced; in addition, the whiteness of the wall surface is 5-8% higher than that of gypsum powder before treatment, 3-10% higher than that of the gypsum powder before treatment, and the wall surface is white with naked eyes, can be independently used as an external surface (without painting, putty and the like), and can also reduce the difficulty degree of covering the ground color (painting).
As can be seen from comparative example 1, part of the gypsum can not be used for producing plastering gypsum without modification treatment, and many performance indexes can not meet the national standard requirements. The comparison shows that the comparative example 2 has high water retention rate which reaches 98.32 percent, and uses a great amount of additives, so that the cost is higher and the market popularization is not facilitated; in addition, the excessive water retention rate and the higher water consumption of the standard consistency easily cause the bleeding phenomenon, the wall surface is easy to be bonded, the construction experience is not good, the defects of hollowing, bag lifting and the like are easily caused, and the trouble is caused to the subsequent construction.
In the formula of the embodiment of the invention, various powder materials and additives are mutually influenced, so that a good application effect is achieved. The plastering gypsum has the overall requirements that various indexes meet the national standard (hard index), the construction performance is good, and the cost performance is high. In conclusion, the surface plastering gypsum provided by the invention has the advantages of good material performance, excellent construction performance, simplicity and convenience in manufacturing, lower cost and contribution to market popularization and application.
The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. The surface plastering gypsum is characterized by being prepared from the following raw materials in parts by weight:
65-85 parts of modified gypsum powder;
10-15 parts of diatomite;
3-5 parts of heavy calcium carbonate;
5-10 parts of talcum powder;
0.2-0.5 parts of retarder;
0.1-0.4 part of water-retaining agent;
0.2-0.8 part of water reducing agent;
1-2 parts of redispersible latex powder;
the modified gypsum powder is obtained by adjusting the pH value of building gypsum fine powder to 8-10 by using ash calcium, and the mesh number of the building gypsum fine powder is less than 20 meshes.
2. The surface plastering gypsum of claim 1, wherein the modified gypsum powder is obtained by modifying: firstly, grinding the calcined building gypsum into powder with the specific surface area of 2500-6000cm 2 And/g, removing large particles by using a 10-mesh and 20-mesh powder selection screen, grinding into fine powder, adjusting the pH value of the fine powder to 8-10 by using ash calcium powder, and optionally adding white cement.
3. The surface plastering gypsum of claim 1, wherein the raw material of the building gypsum fine powder is one or more of natural gypsum, desulfurized gypsum and phosphogypsum.
4. The surface plastering gypsum of any of claims 1 to 3, wherein the diatomaceous earth is ground diatomaceous earth with a fineness of 425 meshes; the ground calcium carbonate is selected powder with the fineness of 80-100 meshes; the fineness of the talcum powder is 325 meshes.
5. The surface plastering gypsum of any of claims 1 to 3, wherein the water retaining agent is hydroxypropyl methyl cellulose ether in an amount of 0.15 to 0.3 parts by weight.
6. The surface plastering gypsum of claim 5, wherein the water retaining agent is hydroxypropyl methyl cellulose ether with viscosity of 60000-100000mPa.s.
7. The surface plastering gypsum of any of claims 1 to 3, wherein the retarder is a bone collagen retarder; the water reducing agent is a polycarboxylic acid water reducing agent.
8. The surface plastering gypsum according to any one of claims 1 to 3, wherein the water retention of the surface plastering gypsum is 90 to 95% and the whiteness of application is more than 73%.
9. The method of making surface rendered gypsum according to any one of claims 1 to 8, comprising the steps of:
adjusting pH of the building gypsum fine powder with a particle size of less than 20 meshes to 8-10 by using lime calcium, and cooling to obtain modified gypsum powder;
weighing the raw materials according to the proportion, mixing the modified gypsum powder, the diatomite, the ground limestone and the talcum powder for 30-60s, sequentially adding the weighed retarder, the water-retaining agent, the redispersible latex powder and the water-reducing agent in the mixing process, and stirring and mixing for 2-3 minutes to obtain the surface layer plastering gypsum.
10. The method of claim 9, wherein the stirring rate during the mixing is 130-150rpm; the surface plastering gypsum is applied by mechanical spraying.
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