CN111170661B

CN111170661B - Green process for preparing gypsum whisker reinforced cement-based material from titanium gypsum

Info

Publication number: CN111170661B
Application number: CN202010088328.9A
Authority: CN
Inventors: 王波; 陈进龙; 高旭; 孙桂红; 张晓慧
Original assignee: Yantai University
Current assignee: Yantai University
Priority date: 2020-02-12
Filing date: 2020-02-12
Publication date: 2021-09-21
Anticipated expiration: 2040-02-12
Also published as: CN111170661A

Abstract

The invention discloses a green process for preparing a gypsum whisker reinforced cement-based material by titanium gypsum, which comprises the following steps: 1) pretreating titanium gypsum to prepare powder; 2) a decoloring treatment process; 3) preparing a whisker; 4) and preparing the reinforced cement-based material. The invention has the advantages that: 1. the green and clean production process design for preparing the gypsum whisker from the titanium gypsum realizes an industrial chain of green environmental protection, low cost and high added value and sustainable development. 2. The gypsum whisker reinforced cement-based material prepared from the titanium gypsum meets the high-performance green quality requirement of engineering on the cement-based material.

Description

Green process for preparing gypsum whisker reinforced cement-based material from titanium gypsum

Technical Field

The invention belongs to a new technology for producing a cement reinforcing agent by using wastes, and particularly relates to a green process for preparing a gypsum whisker reinforced cement-based material by using titanium gypsum.

Background

The trend of people to good life in new generations is urgent for the need of safety, health, functionality, long-life and durable infrastructure. Cement is one of indispensable building cementing materials at present, and cement-based materials have high compressive strength, but are brittle, have small deformation capacity and have low strength under tension and bending load. The defects of compactness are hydration shrinkage and cracking which influence the service life of the cement-based material. The purpose of fiber reinforcement is to utilize the characteristics of high tensile strength and high toughness of fiber materials to prevent the generation and the propagation of cracks after the matrix is deformed under stress or not to break under the condition that the matrix is cracked. The doped metal fiber is easy to corrode, and the production energy consumption is high. The chemical fiber reinforced anti-crack such as polypropylene fiber has the problems that the performance of the fiber is reduced after being soaked in fresh water or seawater, and the fiber becomes nondegradable building rubbish after being discarded. It is increasingly important to improve the quality of cement products by using green admixtures with wide resources and low price to enhance the non-cracking performance of cementThe subject of (1) is to be solved. The gypsum whisker is also called calcium sulfate whisker, is a fibrous crystal and has wide application prospect in the fields of building materials, chemical industry, environmental protection and the like. The composite material has the effects of high tensile strength, high toughness, fire resistance, flame retardance, wear resistance and chemical corrosion resistance, and the diameter is generally 0.1-8 mu m and the length is 0-300 mu m. Therefore, the gypsum whisker is suitable for being used as an ideal additive of cement-based materials as an environment-friendly, nontoxic and low-cost fiber reinforced material. Inhibiting the crack from expanding and enhancing the crack resistance. The quantity of industrial by-product gypsum in China is very large, and when titanium dioxide is produced by adopting a sulfuric acid method, lime (or carbide slag) is added to treat acid wastewater so as to neutralize a large amount of acid wastewater, so that C is produced_aSO₄·2H₂O is industrial waste residue as main component. With the increasing demand of coatings and plastics, the titanium dioxide industry has a steadily increasing trend. 6-10 tons of titanium gypsum can be produced when 1 ton of titanium dioxide is produced, the comprehensive utilization rate is about 10 percent, and the titanium gypsum is a byproduct gypsum with the lowest utilization rate. The large amount of emission not only occupies land, pollutes environment and destroys ecological balance, but also brings huge economic burden to titanium white enterprises and influences on expanded reproduction. The main methods for preparing the gypsum whisker by using the titanium gypsum comprise a normal-pressure salt method, a hydrothermal method, an organic solvent method and the like, and have excessive equipment and technical problems. The gypsum whisker has small yield, high price and little market demand. The industrialization of the gypsum whisker needs to solve the key preparation technology, reduce the cost and develop the market application. One of the technical difficulties in preparing white gypsum whiskers from titanium gypsum is poor whisker quality and low whiteness; secondly, the decoloring and purifying treatment leads the process to be complicated and the cost to be increased; thirdly, the traditional hydrothermal reaction preparation process needs corrosion-resistant equipment, and has long production period, unsafety and high cost; fourthly, the secondary pollution is caused by improper disposal of the waste water and the waste residue. Because no ideal comprehensive utilization technology causes a large amount of accumulation, the method has practical significance for scientific and efficient technical treatment.

Disclosure of Invention

The invention aims to provide a green process for preparing a gypsum whisker reinforced cement-based material by using titanium gypsum, innovate a material technology and design a material preparation process flow according to an ecological cycle concept. The process flow from the downstream resource utilization of the wastewater and the waste residue to the upstream design of the titanium gypsum for preparing the gypsum whisker solves the key preparation technology, leads to industrialization and expands the application field of whisker materials. The glass material is used as a hydrothermal reaction container, and the method has the advantages of mild reaction, simple and convenient process, light weight, corrosion resistance and low cost. The water requirement is reduced and the whiteness of the whiskers is improved through pretreatment and decoloration processes. The sodium sulfate crystal-transformation agent is adopted to replace concentrated sulfuric acid in the traditional process, so that the growth of crystal whiskers is good, the quality is improved, and the corrosion of working procedures and equipment is reduced. The grinding-aid performance of the filtrate can be used for creating a sustainable development gypsum whisker application industrial chain which is green, environment-friendly, low in cost and high in added value.

The gypsum whisker is used as an inorganic fiber reinforced material with environmental protection, no toxicity and low cost, and is suitable for being used as an ideal additive of a cement-based material. Microscopically, the whiskers and the cement hydration products are interwoven, so that the expansion of cracks is inhibited, the cracking resistance is enhanced, the high temperature resistance is realized, the fire resistance and the flame retardance are realized, the minimum energy consumption and the maximum resource utilization are realized, and the high-performance green quality requirement of engineering on cement-based materials is met.

The scheme of the invention is as follows: a green process for preparing gypsum whisker reinforced cement-based materials by titanium gypsum comprises the following steps: drying the blocky titanium gypsum at 105 ℃ for 24h, grinding for 30min, covering the ground titanium gypsum with a preservative film, and aging for more than 7 d. Otherwise, efflorescence phenomenon and water demand increase easily occur, and the whiteness of the whisker and the production period are influenced.

And (3) a decoloring treatment process: adding ionized water into the pretreated titanium gypsum powder, and magnetically stirring and dispersing. Adding concentrated hydrochloric acid for dissolving, neutralizing with shell slaked lime, and filtering to obtain clear liquid and filter residue. And putting the filter residue product into a vacuum drying oven, and drying at the temperature of 200 ℃ until the weight is constant. The preparation of the shell slaked lime selects oyster shell with low iron content and high whiteness to calcine at 900 ℃, and keeps the temperature for 2 h. Cooling, taking out, placing in air, and automatically pulverizing to obtain white powder. Oyster shell need not to grind, and low price, the waste of utilizing is environmental protection.

The preparation process of the whisker comprises the following steps: adding sodium sulfate, triethanolamine and glycerol as crystal modifier into the clear liquid, stirring and dissolving completely. The resulting solution was poured into a 500ml glass bottle, the lid was sealed and tightened and placed in a vacuum oven, the temperature was set at 160 ℃ and heated for 4 h. And opening the reactor after the reaction is completely cooled, performing suction filtration on an SHB-IIIA circulating water type multipurpose vacuum pump, and finally drying the reactor in a vacuum drying oven at 45 ℃ for 24 hours. The prepared gypsum whisker has large length-diameter ratio, good dispersibility and 98 percent of whiteness. The mixing amount is 0.2 percent of the mixing mass of the cement, and the cement has the functions of strengthening, cracking resistance, self-cleaning, chlorine ion resistance and the like. The conventional concentrated sulfuric acid crystal transfer agent is adopted, the crystal whisker is short and small, the agglomeration effect is obvious, a plurality of dendritic crystals are arranged, the disorder dispersibility is poor, and the length is uneven. The order of adding concentrated sulfuric acid is to add a crystal transformation procedure after the hydrothermal synthesis reaction is finished. Sodium sulfate is used as a crystal transformation agent instead of concentrated sulfuric acid, and the hydrothermal synthesis reaction and the crystal transformation are carried out integrally. Good growing of crystal whisker, easy dispersion, reduced acid pollution, simple process and low cost, and is beneficial to the subsequent application of waste liquid.

Preparing a reinforced cement-based material: the mixing amount is 0.1-0.2% of the cement mixing mass, and the functions of strengthening, cracking resistance, self-cleaning, chlorine ion resistance and the like are achieved.

The cement grinding process comprises the following steps: the suction filtration liquid contains triethanolamine and glycerol and is a liquid alcohol grinding aid for the cement grinding process. The mixing amount is 0.3-0.5% of the cement mass, and the effects of reducing grinding energy consumption, increasing fineness and improving cement performance are achieved. The sodium sulfate in the filtrate is an early strength additive of cement, and the filtrate contains trace titanium, so that the self-cleaning function of purifying air by using the cement-based material is improved.

The invention discloses a green process for preparing a gypsum whisker reinforced cement-based material by titanium gypsum, which comprises a powder preparation process by titanium gypsum pretreatment, a decoloration process, a whisker preparation process and a cement powder grinding process applied to filtrate. Firstly, drying blocky titanium gypsum for 24 hours at 105 ℃, cooling and then grinding for 30min to prepare powder, and covering a plastic film in the air for aging for more than 7 d. Secondly, adding a proper amount of pretreated titanium gypsum powder into concentrated hydrochloric acid for dissolving, adding shell hydrated lime for adjusting the pH value to 7, and filtering to form clear liquid and filter residue. Thirdly, adding sodium sulfate, triethanolamine and glycerol as crystal-transforming agents into the clear liquid, fully dissolving and pouring into a glass bottle, wherein the content of the glass bottle is not more than 80 percent of the volume, and sealing the glass bottle with a cover. Heating at 160 ℃ for 4h, cooling, filtering the product, and drying in a vacuum drying oven at 45 ℃ for 24h to obtain white gypsum whisker with the whiteness of 98%. Fourthly, preparing the reinforced cement-based material: and doping the obtained gypsum whiskers into the cement material according to the addition amount of 0.1-0.2% of the mass of the cement, thus obtaining the reinforced cement-based material. Fifthly, using the filtrate as a grinding aid. The process for preparing the red gypsum whisker does not comprise a decoloring process. The process for preparing the red gypsum whisker does not comprise a decoloring process. The invention has the advantages that:

1. the green and clean production process design for preparing the gypsum whisker from the titanium gypsum realizes an industrial chain of green environmental protection, low cost and high added value and sustainable development.

2. The gypsum whisker reinforced cement-based material prepared from the titanium gypsum meets the high-performance green quality requirement of engineering on the cement-based material.

Drawings

FIG. 1 shows the influence of the amount of whisker on the flexural strength of cement;

FIG. 2 is the influence of the amount of whisker on the compressive strength of cement;

FIG. 3 is a line drawing of the test of the electric flux of chloride ion in cement;

figure 4 is a 28 day hydration SEM photograph of cement doped with 0.2% whiskers versus no whiskers.

Detailed Description

The following examples are provided to illustrate the present invention.

Example 1 a green process for preparing a gypsum whisker reinforced cement-based material from titanium gypsum, consisting of the following processes: a process for preparing powder by titanium gypsum pretreatment, a decoloring process, a process for preparing whiskers and a grinding process. The feed is prepared from the following raw materials in parts by weight: 5 parts of pretreated titanium gypsum powder; 8 parts of hydrochloric acid; 3 parts of sodium sulfate; 5 parts of triethanolamine; 5 parts of glycerol.

The green process for preparing the gypsum whisker reinforced cement-based material by using the titanium gypsum comprises the following steps:

step 1: 1kg of blocky titanium gypsum is taken and dried for 24h at 95 ℃, is cooled and then is ground in a ball mill for 30min, the fineness is controlled to be less than 3.2 percent of the screen residue of a square-hole sieve with the fineness of 80 mu m, and the powder is covered with a preservative film and is aged for 7 d;

step 2: 5g of the pretreated titanium gypsum powder was weighed and dissolved in a 250ml beaker by adding 100ml of deionized water and magnetically stirring. Adding 7ml of concentrated hydrochloric acid, stirring for 2min to fully dissolve the agglomerated titanium gypsum, and standing for 5min after stirring;

and step 3: 500g of oyster shell is taken, cleaned and desanded, calcined at high temperature of 900 ℃ and kept at the constant temperature for 2 hours. Naturally cooling, taking out, stacking at room temperature, and automatically pulverizing into white powder.

And 4, step 4: adding shell slaked lime to adjust the pH value to 7, standing for 5min to allow undissolved titanium gypsum to naturally precipitate, and obviously observing solid-liquid delamination at the moment. Filtering the layered clear liquid on a funnel, putting filter residues into a vacuum drying oven, and setting the temperature to be 200 ℃ to constant weight;

and 5: sodium sulfate (3 g), triethanolamine (4 ml) and glycerol (4 ml) were added to the filtered clear solution, and sufficiently dissolved by stirring. The resulting solution was poured into a 500ml glass bottle with a volume of not more than 80%, and sealed with a cap. The glass bottle was placed in a vacuum drying oven, set to 140 ℃ and heated for 4 h. After heating, opening after the reaction is completely cooled, performing suction filtration on an SHB-IIIA circulating water type multipurpose vacuum pump, and finally drying in a vacuum drying oven at 45 ℃ for 24h to obtain white gypsum whiskers;

step 6: preparing a reinforced cement-based material: and doping the obtained gypsum whiskers into the cement material according to the addition amount of 0.1 percent of the mass of the cement, thus obtaining the reinforced cement-based material.

The performance indexes of the gypsum whisker reinforced cement are as follows: compared with the blank, the 3d flexural strength is improved by 0.3MPa, the 3d compressive strength is improved by 0.41MPa, the 3d expansion rate is 0.211 percent, the 28d flexural strength is improved by 1.0MPa, the 28d compressive strength is improved by 3.2MPa, the expansion rate is 0.15 percent, the electric flux passing through the test piece for 6h is 1000 ℃ plus one year, and the chloride ion permeability is very low.

Application of the filtrate: and 7: according to the proportion, 96 percent of clinker, 4 percent of desulfurized gypsum and 0.3 percent of filtrate grinding aid are ground and milled for 30min in a small mill with a standard test of 500mm multiplied by 500mm in diameter by 4.0kg of materials for single use, so as to prepare the Portland cement.

Embodiment 2 a green process for preparing a gypsum whisker reinforced cement-based material from titanium gypsum, which comprises the following steps: a titanium gypsum pretreatment process; decolorizing process, whisker preparation process and grinding process. The feed is prepared from the following raw materials in parts by weight: 6 parts of pretreated titanium gypsum powder; 9 parts of hydrochloric acid; 3 parts of sodium sulfate; 4 parts of triethanolamine; and 6 parts of glycerol.

step 1: drying 1kg of blocky titanium gypsum at 105 ℃ for 24h, cooling, and grinding in a ball mill for 30min, wherein the fineness is controlled to be less than 3.2% of the residue of a square-hole sieve with the fineness of 80 mu m, covering the powder with a preservative film, and aging for 8 d;

step 2: 6g of the pretreated titanium gypsum powder was weighed and dissolved in a 250ml beaker by adding 100ml of deionized water and magnetically stirring. Adding 8ml of concentrated hydrochloric acid, stirring for 2min to fully dissolve the agglomerated titanium gypsum, and standing for 5min after stirring;

and step 3: 500g of oyster shell is taken, cleaned and desanded, calcined at high temperature of 900 ℃ and kept at the constant temperature for 2 hours. Naturally cooling, taking out and stacking at room temperature. After absorbing water, the mixture becomes white powder;

and 4, step 4: adding shell slaked lime to adjust the pH value to 7, standing for 5 minutes to allow undissolved titanium gypsum to naturally precipitate, and obviously observing solid-liquid separation. Filtering the layered clear liquid on a funnel, putting filter residues into a vacuum drying oven, and setting the temperature to be 200 ℃ to constant weight;

and 5: sodium sulfate (3 g), triethanolamine (3 ml) and glycerol (5 ml) were added to the filtered clear solution, and sufficiently dissolved by stirring. The resulting solution was poured into a 500ml glass bottle with a volume of not more than 80%, and sealed with a cap. The glass bottle was placed in a vacuum drying oven, the temperature was set to 160 ℃ and heated for 4 h. After heating, opening after the reaction is completely cooled, performing suction filtration on an SHB-IIIA circulating water type multipurpose vacuum pump, and finally drying in a vacuum drying oven at 45 ℃ for 24h to obtain white gypsum whiskers;

step 6: preparing a reinforced cement-based material: and doping the obtained gypsum whiskers into the cement material according to the addition amount of 0.2 percent of the mass of the cement, thus obtaining the reinforced cement-based material.

The performance indexes of the gypsum whisker reinforced cement are as follows: compared with the blank, the 3d flexural strength is improved by 0.4MPa, the 3d compressive strength is improved by 4.3MPa, the 3d expansion rate is 0.222 percent, the 28d flexural strength is improved by 1.1MPa, the 28d compressive strength is improved by 5.8MPa, the expansion rate is 0.16 percent, the electric flux passing through the test piece for 6h is 1000 ℃ and the chloride ion permeability is very low.

Embodiment 3 a green process for preparing a gypsum whisker reinforced cement-based material from titanium gypsum, consisting of the following processes: titanium gypsum pretreatment process, whisker preparation process and cement grinding process. The feed is prepared from the following raw materials in parts by weight: 4 parts of pretreated titanium gypsum powder; 10 parts of glycerol.

step 1: drying 1kg of blocky titanium gypsum at 105 ℃ for 2h, cooling, and grinding in a ball mill for 30min, wherein the fineness is controlled to be less than 3.2% of the residue of a square-hole sieve with the fineness of 80 mu m, covering the powder with a preservative film, and aging for 8 d;

step 2: weighing 4g of pretreated gypsum powder, adding 100ml of deionized water and 8ml of glycerol, and magnetically stirring and dispersing. Pouring into 500ml glass bottle with the volume not exceeding 80%, and sealing with cap. The glass bottle was placed in a vacuum drying oven, the temperature was set at 150 ℃ and heated for 4 h. After heating, opening the glass bottle after the glass bottle is completely cooled, performing suction filtration on an SHB-IIIA circulating water type multipurpose vacuum pump, and finally drying in a vacuum drying oven at 45 ℃ for 24 hours to obtain a mixture of impurities and gypsum whiskers;

and step 3: preparing a reinforced cement-based material: and doping the obtained gypsum whiskers into the cement material according to the addition amount of 0.2 percent of the mass of the cement, thus obtaining the reinforced cement-based material.

The performance indexes of the gypsum whisker reinforced cement are as follows: compared with the blank, the 3d flexural strength is improved by 0.2MPa, the 3d compressive strength is improved by 1.3MPa, the 3d expansion rate is 0.142 percent, the 28d flexural strength is improved by 0.6MPa, the 28d compressive strength is improved by 2.4MPa, the expansion rate is 0.103 percent, the electric flux passing through the test piece for 6h is 1000 ℃ plus one, and the chloride ion permeability is very low.

Application of the filtrate: and 4, step 4: grinding for 30min in a small test standard test with the diameter of 500mm multiplied by 500mm for 96 percent of clinker, 4 percent of desulfurized gypsum, 0.3 percent of filtrate grinding aid based on the mass of cement and 4.0kg of material used in a single time according to the proportion to prepare the portland cement.

Test examples

1. Raw materials:

shell: the shell is obtained from seafood processing shop in vegetable market, is oyster shell, and has high calcium content and good whiteness.

Shell slaked lime: cleaning oyster shell, calcining at 900 deg.C in high temperature furnace, and maintaining the temperature for 2 hr. Naturally cooling, taking out and stacking at room temperature. After absorbing water, the mixture became white powder.

Glycerol: analytically pure, Tianjin Bodi chemical Co., Ltd.

Triethanolamine: analytically pure, Tianjin Bodi chemical Co., Ltd.

Sodium sulfate: analytical purity, Henjin chemical reagents manufacturing Co., Ltd.

Concentrated hydrochloric acid: analytically pure, Tianjin Bodi chemical Co., Ltd.

Cement: 32.5 composite Portland cement, available from Qingquan powder milling stations.

Cement clinker: the grain diameter is 2-5cm and is provided by a Qingquan flour milling station. Crushing with jaw crusher to below 5 mm.

Desulfurized gypsum: the chemical composition is shown in table 1.

Titanium gypsum: the chemical compositions are shown in Table 1.

Standard sand: xiamen Esse Standard Sand, Inc.

TABLE 1 chemical composition of raw materials%

2. The test method comprises the following steps:

2.1 the preparation method of the gypsum whisker comprises the following steps:

crushing 1kg of titanium gypsum by using a hammer, drying in a drying oven at 105 ℃ and preserving heat for 24h, cooling and then grinding in a ball mill for 30min, covering the ground powder with a preservative film and aging for more than 7 d.

The white gypsum whisker preparation process flow comprises the following steps:

2.2 grinding aid test methods:

3.5kg of materials used in a single time, the ratio of the portland cement to the clinker, namely the desulfurized gypsum is 96: 4. The clinker is firstly crushed by a jaw crusher, and then is put into a small mill with the diameter of 500mm multiplied by 500mm for grinding for 30min to be discharged, and the physical properties of the cement are tested. The grinding aid test method is measured according to GB/T26748-2011; the water consumption and the setting time of the standard consistency of the cement are measured according to GB 1346-2001; the strength of the cement mortar is determined according to GB/T17671-1999 test method for the strength of the cement mortar (ISO method).

2.3 Gypsum whisker reinforced cement test method

Gypsum whiskers accounting for 0.2 percent, 0.3 percent and 0.4 percent of the mass of the cement are added into 32.5 composite portland cement to prepare a cement mortar test block, and the cement mortar test block is demoulded and cured for 3d, 7d and 28d to test the flexural strength and the compressive strength.

A net paste test piece was molded with a mold of 25X 280mm, the test piece was removed from the mold, cured in water at 20 ℃ until a set age, and taken out, and the linear expansion rate was measured with reference to JC/T313-2009(2015) expansion cement expansion rate test method.

The cylindrical cement paste test block with the diameter of 100 multiplied by 50mm is manufactured, and the mixing amount of the crystal whiskers is 0 percent and 0.2 percent. And (5) placing the test piece into water for curing for 28 days after the test piece is molded and demoulded. And taking out the test block, loading the test block into a test tank, screwing screws, respectively injecting a sodium hydroxide solution and a sodium chloride solution into the two tanks, connecting electric wires of the instrument and the test tank, starting the chlorine ion electric flux testing instrument, wherein the testing time is six hours, and the instrument automatically prints one part of data every 120 min. Resistance to chloride ion penetration was performed according to ASTM C1202-12.

3. Test and result analysis

3.1 Effect of Gypsum whiskers on the Properties of 32.5 composite Portland Cement

The influence of the whiskers on the fracture and compression resistance of the cement is shown in the figures 1-2, and the shrinkage performance test results are shown in the table 2. The results of the cement chloride ion flux test are shown in FIG. 3.

TABLE 2 expansion and contraction ratios according to age

The data of the table 1, the figure 2 and the figure 3 show that the strength of the cement is improved by 0.1 to 0.2 percent of the weight of the whisker-doped cement, and the strength is reduced by 0.4 percent of the weight of the whisker-doped cement. When the mixing amount is 0.2 percent, the 3d flexural strength of the cement is improved by 0.4MPa, the 3d compressive strength is improved by 4.3MPa, the 3d expansion rate is 0.222 percent, the 28d flexural strength is improved by 1.1MPa, the 28d compressive strength is improved by 5.8MPa, and the expansion rate is 0.16 percent. Compared with the blank, the current is reduced for 6h through the chlorine ion electric flux test analysis, and the electric flux is 100-1000C, which shows that the permeability of the chlorine ion is very low. The cement can generate a shrinkage reaction in the early stage of hydration, the calcium sulfate whisker can play a certain expansion effect when being added, and the expansion effect is more obvious when the addition amount is increased. Partial dissolution of calcium sulfate whiskers to produce SO4^2-Continuously reacting with aluminate and calcium hydroxide in cement to generate high-sulfur hydrated calcium sulphoaluminate, and expanding in volume.

From the graph of FIG. 4, which shows the crack-arresting effect of the whiskers, it can be seen that the layered Ca (OH) in the cement matrix₂The crystal and a large amount of C-H-S gel, the crystal whisker in the cement matrix is prismatic fiber, and is distributed in three-dimensional disorderly in the set cement to form a net structure, and the set cement is bonded on the surface of the set cement to form a unified whole with the set cement.

When the whiskers are randomly and uniformly distributed in the cement mortar test block, the average central distance of the whiskers is reduced along with the increase of the doping amount of the whiskers, cracks are limited in a smaller range, and the size of the cracks when the cracks extend to the interface of the whiskers and the cement mortar is relatively small. Along with the increase of the mixing amount of the whiskers, when the dispersion in cement mortar is good, the pore distribution is improved, and pores are refined to enhance the strength of a microstructure, so that the macroscopic mechanical property is improved. After the whisker is mixed excessively, the interaction among the whiskers is increased, so that the resistance received by the whiskers in the dispersing process is increased, the dispersibility of the whiskers is poor, and the agglomerated whiskers have no gelation property to form defects, so that the strength of a cement mortar test piece is reduced.

3.2 Effect of filtrate on Portland Cement Properties

The results of the tests on the fineness of the sieved portland cement and the physical properties are shown in tables 3 and 4.

TABLE 3 comparison of fineness of portland cement screens

As shown in Table 3, the grinding aid effect is: triethanolamine, glycerol, filtrate and blank.

Compared with the blank, the fineness of the 45 mu m sieve residue is reduced by 2.8 percent, and the fineness of the 80 mu m sieve residue is reduced by 3.4 percent. Has the effect of grinding aid.

TABLE 4 Portland cement physical Property index

As shown in Table 4, compared with blank Portland cement, the flexural strength of the filtrate grinding aid added in 28d is improved by 1.3MPa, the compressive strength is improved by 4.4MPa, and the filtrate is feasible to be used as a cement grinding aid.

The above experiments show that the material technology is innovative, and the material preparation process flow is designed according to the ecological cycle concept. And (4) recycling the filtrate and filter residue. The method realizes the industrialization requirement of preparing the gypsum whisker reinforced cement from the titanium gypsum, and has the advantages of environmental protection, simple and convenient process flow, safety, reliability and low investment.

Although specific embodiments of the invention have been described above, it will be understood by those skilled in the art that the specific embodiments of the invention described are illustrative only and are not limiting to the scope of the invention, and that equivalent modifications and variations can be made by those skilled in the art without departing from the spirit of the invention, which is to be covered by the appended claims.

Claims

1. A green process for preparing a gypsum whisker reinforced cement-based material by titanium gypsum is characterized by comprising the following steps: the method comprises the following steps:

1) pretreating titanium gypsum to prepare powder, drying blocky titanium gypsum for 24 hours at 105 ℃, cooling and then grinding for 30min to prepare powder, and covering a plastic film in the air for aging for more than 7 days;

2) a decoloring treatment process, namely adding a proper amount of pretreated titanium gypsum powder into concentrated hydrochloric acid for dissolving, adding shell slaked lime for adjusting the pH value to 7, and filtering to form clear liquid and filter residue; putting the filter residue product into a vacuum drying oven, and drying at 200 ℃ to constant weight;

3) adding sodium sulfate, triethanolamine and glycerol as crystal modifier into the clear liquid, stirring and dissolving; pouring the obtained solution into a glass bottle, sealing and screwing a cover, putting the glass bottle into a vacuum drying oven, setting the temperature to 160 ℃, and heating for 4 hours; opening after the reaction is completely cooled, performing suction filtration on a circulating water type multipurpose vacuum pump, and finally drying in a vacuum drying oven at 45 ℃ for 24 hours;

4) preparing a reinforced cement-based material: according to the addition amount of 0.2-0.4% of the mass of the cement, the obtained gypsum whiskers are blended into the cement material, and then the reinforced cement-based material can be obtained.

2. The green process for preparing a gypsum whisker reinforced cement-based material from titanium gypsum according to claim 1, which is characterized in that: in the step 2), oyster shells with low iron content and high whiteness are calcined at 900 ℃ and are kept warm for 2 hours; cooling, taking out, placing in air, and automatically pulverizing to obtain white powder.

3. The green process for preparing a gypsum whisker reinforced cement-based material from titanium gypsum according to claim 1, which is characterized in that: the weight parts of the raw materials are as follows: the weight parts of the raw materials are as follows: 6 parts of titanium gypsum pretreatment powder; 9 parts of concentrated hydrochloric acid; 3 parts of sodium sulfate; 4 parts of triethanolamine; and 6 parts of glycerol.

4. A green process for preparing gypsum whisker reinforced cement-based materials by titanium gypsum comprises the following steps: a titanium gypsum pretreatment process, a whisker preparation process and a cement grinding process; the feed is prepared from the following raw materials in parts by weight: 4 parts of titanium gypsum pretreatment powder; 10 parts of glycerol;

step 2: weighing 4g of titanium gypsum pretreatment powder, adding 100ml of deionized water and 8ml of glycerol, and magnetically stirring and dispersing;

pouring into 500ml glass bottle with volume not more than 80%, and sealing with cover; putting the glass bottle into a vacuum drying oven, setting the temperature to 150 ℃ and heating for 4 hours; after heating, opening the glass bottle after the glass bottle is completely cooled, performing suction filtration on an SHB-IIIA circulating water type multipurpose vacuum pump, and finally drying in a vacuum drying oven at 45 ℃ for 24 hours to obtain a mixture of impurities and gypsum whiskers;