CN117430354A - Novel cement grinding aid and preparation method thereof - Google Patents

Abstract

The invention provides a new type of cement grinding aid and its preparation method, which relates to the technical field of cement processing. It contains 30-45 parts of ethyl orthosilicate, 30-40 parts of silane coupling agent, 10-20 parts of ethylene glycol, and deionized Mix 20-25 parts of water, 5-8 parts of catalyst, 8-10 parts of graphene oxide, 20-25 parts of sodium thiosulfate and 15-20 parts of organic acid to form the grinding aid. A large number of hydroxyl groups on the surface of silanol are related to the cement. Very good adsorption, organic acid is used as the main chromium reduction agent, and sodium thiosulfate is used as the chromium reduction assistant. The addition of organic acid effectively improves the high temperature sensitivity of sodium thiosulfate when used alone. The two work together to achieve the best results. Chromium reduction effect, reducing hexavalent chromium into non-toxic and harmless trivalent chromium, which not only has the excellent grinding aid effect of conventional grinding aids, but also the organic acid improves the high temperature resistance and oxidation resistance of grinding aids, and can be used for a long time. Long-term storage avoids oxidation by oxygen during storage and affects the chromium reduction effect.

Description

A new cement grinding aid and its preparation method

Technical field

The invention relates to the technical field of cement processing, specifically a new cement grinding aid and a preparation method thereof.

Background technique

Cement grinding aid is an additive added during the cement grinding process that can effectively prevent cement particles from agglomerating and improve grinding efficiency. Cement grinding aid mainly achieves physical and chemical changes on the particle surface through its surface activity and charge dispersion. Modification can bring into play the interface effect and mechanical performance, which can improve the grinding efficiency of cement, reduce energy consumption, increase the specific surface area of cement, optimize the cement particle gradation, thereby improving the strength and quality of cement. It is generally believed that cement grinding aids pass through adsorption On the surface of cement particles, on the one hand, it increases the distance between particles and reduces van der Waals forces; on the other hand, it neutralizes or shields the electrostatic charge on the cross-section of cement particles, reduces the tendency of agglomeration between fine cement particles, improves the dispersion of cement, and improves grinding. efficiency.

At present, most commonly used cement grinding aids are mainly composed of hydroxyalcohols, alkanolamines and their compound products, which have good grinding aid effects. Among them, triethanolamine is the most widely researched and used.

There are the following technical problems when using the existing technology:

1. Most of the grinding aids using triethanolamine are small molecule composite grinding aids, which are effective, but have poor performance stability and are sensitive to changes in dosage. They have grinding aid limits and the maximum grinding aid efficiency is 10-15%. It is impossible to continue to increase the amount of grinding aid to improve the grinding effect. At the same time, due to the compatibility with the concrete water-reducing agent, the fluidity of the concrete is poor and the collapse loss is large, which affects the performance of the concrete. Moreover, the main component of grinding aid, triethanolamine, is relatively expensive, resulting in higher cost of grinding aid;

2. The oxidized hexavalent chromium in the cement cannot be removed. The addition of existing grinding aids has no effect on the removal of hexavalent chromium in the cement, so that the hexavalent chromium in the cement can flow into the ground with rainwater, causing pollution.

Contents of the invention

technical issues solved

In view of the shortcomings of the existing technology, the present invention provides a new type of cement grinding aid and its preparation method, which solves the following problems: high cost of grinding aid, poor grinding aid efficiency, large loss and hexavalent chromium in cement High content cannot be reduced.

Technical solutions

In order to achieve the above objects, the present invention is realized through the following technical solutions: a new cement grinding aid and its preparation method, including the preparation method of the grinding aid as follows:

Sp1: Preparation of raw materials. The raw material preparation is to prepare in order 30-45 parts of ethyl orthosilicate, 30-40 parts of silane coupling agent, 10-20 parts of ethylene glycol, 20-25 parts of deionized water, and 5-5 parts of catalyst. Mix 8 parts, 8-10 parts of graphene oxide, 20-25 parts of sodium thiosulfate and 15-20 parts of organic acid;

Sp2: Preparation of solution A. The preparation of solution A is to slowly drop ethyl orthosilicate into the mixed solution of ethylene glycol and deionization, stir and mix to obtain nano-SiO ₂ sol solution A;

Sp3: Preparation of solution B. The preparation of solution B is to slowly drop the silane coupling agent into solution A in step Sp2, add 5 parts of catalyst, stir and mix to obtain silanol solution B of nano- _SiO2 sol;

Sp4: Forming of the grinding aid. The forming of the grinding aid is to add the graphene oxide solution to the solution B in step Sp3, add sodium thiosulfate, and stir evenly for 15 minutes. After the sodium thiosulfate is completely dissolved, Add organic acid and stir evenly for 5 minutes. After stirring and mixing, cool to room temperature to obtain a new cement grinding aid.

Preferably, the temperature during mixing in the preparation of solution A and solution B is both 70°C, the mixing speed is 100 r/min, and the stirring time is 2 h.

Preferably, the temperature during mixing during the molding of the grinding aid is 40°C, the mixing speed is 800r/min, and the stirring time is 2 h. During the preparation of solution A, the preparation of solution B and the molding of the grinding aid. All are heated using a constant temperature water bath.

Preferably, the silane coupling agent in the raw material preparation is 3-aminopropyltriethoxysilane, and the chemical formula of the organic acid is C ₂ H ₄ O ₂ S.

Preferably, the graphene oxide in the raw material preparation is an industrial grade graphene oxide aqueous dispersion with a solubility of 1%.

Preferably, the catalyst in the preparation of the raw material is acetic acid, and the pH of the mixed solution in the preparation of solution A and solution B is both 4-6.

A new cement grinding aid, the grinding aid consists of 30-45 parts of ethyl orthosilicate, 30-40 parts of silane coupling agent, 10-20 parts of ethylene glycol, 20-25 parts of deionized water, and a catalyst Mix 5-8 parts, 8-10 parts graphene oxide, 20-25 parts sodium thiosulfate and 15-20 parts organic acid.

Preferably, the raw material preparation stage in the Sp1 step also includes 5-10 parts of nanoscale carbon nanotubes.

Preferably, the grinding aid forming stage in the Sp4 step uses ultrasonic-assisted stirring technology to achieve more uniform mixing and finer particle size distribution at the microscopic level.

Preferably, in the preparation stage of solution B in the Sp3 step, microcapsules are built in. The repair agent is encapsulated in the microcapsules and evenly dispersed in the grinding aid. When microcracks occur in the cement during the grinding process, the microcapsules will crack, releasing the repair agent.

beneficial effects

The invention provides a new cement grinding aid and a preparation method thereof. It has the following beneficial effects:

The present invention uses 30-45 parts of ethyl orthosilicate, 30-40 parts of silane coupling agent, 10-20 parts of ethylene glycol, 20-25 parts of deionized water, 5-8 parts of catalyst, and 8-8 parts of graphene oxide. 10 parts, 20-25 parts of sodium thiosulfate and 15-20 parts of organic acid constitute a grinding aid, using silane and silane coupling agent as raw materials, low price, avoiding the shortcomings and defects of triethanolamine, and a large number of silanol surfaces Hydroxyl groups have a good adsorption effect on cement. Nano-SiO ₂ sol can further improve the adsorption capacity of grinding aids on the cement surface. Graphene oxide improves the film-forming ability of grinding aids on the cement surface, enhances the dispersion of cement particles, and improves Grinding efficiency, in addition, the silanol adsorption layer formed on the surface of cement particles has a large number of hydroxyl groups, and also has good adsorption capacity for water-reducing agents, has good compatibility with water-reducing agents, improves the working performance of concrete, and has Broad application prospects.

In the present invention, organic acid and sodium thiosulfate are added to the proportion of the cement grinding aid to reduce the oxidation of internal hexavalent chromium when mixed with cement. The organic acid is used as the main chromium reducing agent, and sodium thiosulfate is used as the main agent. As a chromium reducing agent, the two synergistically reduce chromium. The addition of organic acid effectively improves the high temperature sensitivity of sodium thiosulfate as a chromium reducing agent alone. The two synergistically achieve the best chromium reducing effect and reduce hexavalent chromium to inorganic chromium. The toxic and harmless trivalent chromium not only has the excellent grinding aid effect of conventional grinding aids, but also due to the addition of organic acids, the organic acids improve the high temperature resistance and oxidation resistance of the grinding aids, and can be stored for a long time to avoid The chromium reduction effect is affected due to oxidation by oxygen during storage.

Description of the drawings

Figure 1 is a diagram of the preparation method of the grinding aid of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

As shown in Figure 1, a new cement grinding aid and its preparation method, including the preparation method of the grinding aid, are as follows:

Sp1: Preparation of raw materials. The raw material preparation is to prepare in order 30-45 parts of ethyl orthosilicate, 30-40 parts of silane coupling agent, 10-20 parts of ethylene glycol, 20-25 parts of deionized water, and 5-5 parts of catalyst. Mix 8 parts, 8-10 parts of graphene oxide, 20-25 parts of sodium thiosulfate and 15-20 parts of organic acid;

Sp2: Preparation of solution A. The preparation of solution A is to slowly drop ethyl orthosilicate into the mixed solution of ethylene glycol and deionization, stir and mix to obtain nano-SiO ₂ sol solution A;

Sp3: Preparation of solution B. The preparation of solution B is to slowly drop the silane coupling agent into solution A in step Sp2, add 5 parts of catalyst, stir and mix to obtain silanol solution B of nano- _SiO2 sol;

Sp4: Forming of the grinding aid. The forming of the grinding aid is to add the graphene oxide solution to the solution B in step Sp3, add sodium thiosulfate, and stir evenly for 15 minutes. After the sodium thiosulfate is completely dissolved, Add organic acid and stir evenly for 5 minutes. After stirring and mixing, cool to room temperature to obtain a new cement grinding aid.

The raw material preparation stage in the Sp1 step also includes 5-10 parts of nanoscale carbon nanotubes. The grinding aid forming stage in the Sp4 step uses ultrasonic-assisted stirring technology to achieve more uniform grinding at the microscopic level. Mixing and finer particle size distribution, the solution B preparation stage in the Sp3 step has built-in microcapsules, the repair agent is encapsulated in the microcapsules, and evenly dispersed in the grinding aid, when the cement produces micro-capsules during the grinding process When cracked, the microcapsules will rupture, releasing the repair agent.

Repair agent recipe:

Epoxy: 40% - Used as a base adhesive to cure quickly and provide structural repair when cracks develop.

Hardener: 15% - used to promote the curing process of epoxy resin.

Filler: 10% - Micron sized silica sand for extra volume and strength.

Nanosilicate particles: 15% - used to improve the compressive strength and durability of the repair agent.

Nanocarbon Nanotubes: 10% - Used to enhance the tensile strength and electrical conductivity of the repair agent.

Catalyst: 5% - Used to accelerate the chemical reaction between epoxy resin and hardener.

Antioxidant: 5% - Used to prevent oxidation of the repair agent during storage and use.

Microcapsule preparation:

Housing Material: Polyurethane or polymethylmethacrylate.

Internal Repair Agent: The repair agent formula described above.

The preparation process includes:

Shell preparation: Polyurethane microcapsules are prepared by emulsion polymerization. Polyurethane monomers and repair agents are dispersed in an aqueous phase, and then a catalyst is added to initiate the polymerization reaction to form microcapsules containing the repair agent.

Restorative Preparation: Combine all of the above ingredients together, stirring well to ensure even distribution.

The mixing temperature in the preparation of solution A and solution B is both 70°C, the mixing speed is 100r/min, and the stirring time is 2 hours. The mixing temperature in the molding of the grinding aid is 40°C, and the mixing speed is 800r/min, the stirring time is 2h. The preparation of solution A, the preparation of solution B and the molding of grinding aids are all heated by a constant temperature water bath. The silane coupling agent in the raw material preparation is 3-aminopropyltriethoxy. silane, and the chemical formula of the organic acid is C ₂ H ₄ O ₂ S. The graphene oxide in the raw material preparation is an industrial-grade graphene oxide aqueous dispersion with a solubility of 1%. The catalyst in the raw material preparation is acetic acid, solution A. The pH of the mixed solution in the preparation of and solution B is both 4-6.

Specific embodiment one:

As shown in Figure 1, the grinding aid is formulated according to the above content, and is mainly made of the following raw materials by weight:

35 parts of ethyl orthosilicate, 30 parts of silane coupling agent, 12 parts of ethylene glycol, 20 parts of deionized water, 5 parts of catalyst, 8 parts of graphene oxide, 20 parts of sodium thiosulfate and 15 parts of organic acid, Slowly add ethyl orthosilicate dropwise to the mixed solution of ethylene glycol and deionized water, keep stirring at 70°C and 1000r/min for 2 hours to obtain nano-SiO2 sol solution A, and slowly add silane coupling agent to solution A. , add 5 parts of the catalyst, continue stirring at 70°C and a rotating speed of 1000r/min for 2 hours, and obtain the silanol solution B of the nano-SiO2 sol. Add the graphene oxide solution to solution B, and keep stirring at 40°C and a rotating speed of 800r/min. 2h, and add sodium thiosulfate, stir evenly for 15 minutes, after the sodium thiosulfate is completely dissolved, add organic acid, stir evenly for 5 minutes, cool to room temperature to obtain a new cement grinding aid, the graphene oxide solution is 8 parts oxidized A mixed solution of graphene aqueous dispersion and 8 parts of deionized water.

According to the content of the proportions, two sets of comparative proportions were set up to conduct comparative experiments. They are as follows: Comparative Example 1, 35 parts of silane coupling agent, 20 parts of ethylene glycol, 22 parts of deionized water, 5 parts of catalyst, and 20 parts of sodium thiosulfate. Mix 15 parts of organic acid and 10 parts of graphene oxide. Slowly add silane coupling agent dropwise to the mixed solution of ethylene glycol and deionized water. Add 5 parts of catalyst. Keep stirring at 70°C and 1000r/min for 1 hour. Obtain silanol solution A, add graphene oxide solution to solution A, stir at 40°C and 800r/min for 1 hour, add sodium thiosulfate, and stir evenly for 15 minutes. After sodium thiosulfate is completely dissolved, add Organic acid, stir evenly for 5 minutes, and cool to room temperature to obtain a new cement grinding aid. The graphene oxide solution is a mixed solution of 10 parts graphene oxide aqueous dispersion and 8 parts deionized water;

Comparative Example 2, 40 parts of ethyl orthosilicate, 35 parts of silane coupling agent, 20 parts of ethylene glycol, 22 parts of deionized water, 7 parts of catalyst, 20 parts of sodium thiosulfate and 15 parts of organic acid were mixed into ethyl Slowly add ethyl orthosilicate dropwise into the mixed solution of diol and deionized water, keep stirring at 70°C and 1000r/min for 1 hour to obtain silanol solution A, slowly add silane coupling agent to solution A, and add the catalyst 7 parts, stir for 2 hours at 70°C and 1000 r/min, add sodium thiosulfate, and stir evenly for 15 minutes. After sodium thiosulfate is completely dissolved, add organic acid, stir evenly for 5 minutes, and cool to room temperature to obtain the new product. Cement grinding aid.

The grinding aids prepared in Example 1 and Comparative Examples 1-2 were used in cement production. Cement was used as the control group. In the control group experiment, the grinding materials clinker, limestone, mineral powder and gypsum were used for mixing. The ratio is 80:10:5:5, the grinding aid dosage is 0.1%, and the grinding time is 30 minutes. The specific surface area, activity and fluidity of the cement after grinding are compared to analyze the effect of the cement grinding aid prepared in the present invention. For the effect, the specific surface area is tested using the Breton method according to GB/T8074-2008 cement specific surface area determination method; the cement mortar strength is tested according to GB/T17671-1999; the fluidity of cement slurry is tested according to JC/T1083-2008.

Table 1 shows the mix ratio of mortar and concrete raw materials for all application examples in this application:

Table 1 Mixing ratio of mortar and sand

Material cement sand water Dosage (g) 450 1350 225

The cement performance index obtained by combining Example 1, Comparative Examples 1-2 and the control group is shown in Table 2 below. Table 2 shows the specific surface area, compressive strength and fluidity of the cement after grinding, where Fin, F60 and FL are respectively Initial fluidity, 60min fluidity and flow loss of cement slurry:

Table 2 Cement performance index

As can be seen from Tables 1 and 2 above, compared with the control group, the specific surface area of Example 1 has increased, indicating that the grinding aid of the present invention can increase the grinding efficiency of cement, increase the specific surface area of cement particles, and is larger than that on the market. The grinding effect of common grinding aids in Comparative Example 1 and Comparative Example 2 is due to the lack of ethyl orthosilicate silane and graphene oxide respectively. The grinding effect of the obtained grinding aids is not ideal, even lower than that of the control group. Analysis of cement activity shows that Example 1 slightly improved the early activity of cement, but significantly increased the 28d strength of cement. This shows that the grinding aid prepared by the present invention improves the grinding efficiency and increases the density of cement particles between 3-30 μm. proportion, thus increasing the cement activity and improving the 28d strength of the cement. The water-cement ratio adopted in the cement slurry test was 0.29, and the water-reducing agent content was 0.8%. Comparing the fluidity of the slurry, it was found that Example 1 significantly improved the net slurry. The fluidity of the slurry was improved, and the compatibility with the water-reducing agent was improved. However, Comparative Examples 1 and 2, which lacked tetraethyl orthosilicate silane and graphene oxide, had obvious bleeding and were not well compatible with the water-reducing agent.

Specific embodiment two:

Mix 40 parts of ethyl orthosilicate, 26 parts of silane coupling agent, 20 parts of ethylene glycol, 25 parts of deionized water, 7 parts of catalyst, 10 parts of graphene oxide, 20 parts of sodium thiosulfate and 15 parts of organic acid. Slowly add ethyl orthosilicate dropwise into the mixed solution of ethylene glycol and deionized water, keep stirring at 70°C and 1000r/min for 1 hour, to obtain nano-SiO2 sol solution A, slowly add silane coupling agent to solution A, Add 5 parts of catalyst and stir for 2 hours at 60°C and 1100r/min to obtain silanol solution B of nano-SiO2 sol. Add graphene oxide solution to solution B and stir for 1 hour at 40°C and 900r/min. Add sodium thiosulfate and stir evenly for 15 minutes. After the sodium thiosulfate is completely dissolved, add organic acid and stir evenly for 5 minutes. Cool to room temperature to obtain a new cement grinding aid. The graphene oxide solution is 10 parts of graphene oxide. A mixed solution of aqueous dispersion and 8 parts of deionized water.

The grinding aids prepared in Example 2 and Comparative Examples 1-2 were used in cement production. Cement was used as the control group. In the control group experiment, the grinding materials clinker, limestone, mineral powder and gypsum were used for mixing. The ratio is 80:10:5:5, the grinding aid dosage is 0.1%, and the grinding time is 30 minutes. The specific surface area, activity and fluidity of the cement after grinding are compared to analyze the effect of the cement grinding aid prepared in the present invention. For the effect, the specific surface area is tested using the Breton method according to GB/T8074-2008 cement specific surface area determination method; the cement mortar strength is tested according to GB/T17671-1999; the fluidity of cement slurry is tested according to JC/T1083-2008.

The cement performance index obtained by combining Example 2, Comparative Examples 1-2 and the control group is shown in Table 3 below. Table 3 shows the specific surface area, compressive strength and fluidity of the cement after grinding, where Fin, F60 and FL are respectively Initial fluidity, 60min fluidity and flow loss of cement slurry:

Table 3 Cement performance index

As can be seen from Tables 1 and 3 above, compared with the control group, the specific surface area of Example 2 has increased, indicating that the grinding aid of the present invention can increase the grinding efficiency of cement, increase the specific surface area of cement particles, and is larger than that on the market. The grinding effect of common grinding aids in Comparative Example 1 and Comparative Example 2 is due to the lack of ethyl orthosilicate silane and graphene oxide respectively. The grinding effect of the obtained grinding aids is not ideal, even lower than that of the control group. Analysis of cement activity shows that Example 2 slightly improved the early activity of cement, but significantly increased the 28d strength of cement. This shows that the grinding aid prepared by the present invention improves the grinding efficiency and increases the density of cement particles between 3-30 μm. proportion, thus increasing the cement activity and improving the 28d strength of the cement. The water-cement ratio adopted in the cement slurry test was 0.29, and the water-reducing agent content was 0.8%. Comparing the fluidity of the slurry, it was found that Example 2 significantly improved the net slurry. The fluidity of the slurry was improved, and the compatibility with the water-reducing agent was improved. However, Comparative Examples 1 and 2, which lacked tetraethyl orthosilicate silane and graphene oxide, had obvious bleeding and were not well compatible with the water-reducing agent.

Specific embodiment three:

32 parts of ethyl orthosilicate, 35 parts of silane coupling agent, 15 parts of ethylene glycol, 22 parts of deionized water, 7 parts of catalyst, 8 parts of graphene oxide, 20 parts of sodium thiosulfate and 15 parts of organic acid. Slowly add ethyl orthosilicate dropwise into the mixed solution of ethylene glycol and deionized water, keep stirring at 60°C and 900r/min for 3 hours, and obtain nano-SiO2 sol solution A. Add the silane coupling agent slowly and dropwise into solution A. Add 5 parts of catalyst and stir for 2 hours at 70°C and 1000r/min to obtain silanol solution B of nano-SiO2 sol. Add graphene oxide solution to solution B and stir for 1 hour at 50°C and 800r/min. Add sodium thiosulfate and stir evenly for 15 minutes. After the sodium thiosulfate is completely dissolved, add organic acid and stir evenly for 5 minutes. Cool to room temperature to obtain a new cement grinding aid. The graphene oxide solution is 8 parts of graphene oxide. A mixed solution of aqueous dispersion and 10 parts of deionized water.

The grinding aids prepared in Example 3 and Comparative Examples 1-2 were used in cement production. Cement was used as the control group. In the control group experiment, the grinding materials clinker, limestone, mineral powder and gypsum were used for mixing. The ratio is 80:10:5:5, the grinding aid dosage is 0.1%, and the grinding time is 30 minutes. The specific surface area, activity and fluidity of the cement after grinding are compared to analyze the effect of the cement grinding aid prepared in the present invention. For the effect, the specific surface area is tested using the Breton method according to GB/T8074-2008 cement specific surface area determination method; the cement mortar strength is tested according to GB/T17671-1999; the fluidity of cement slurry is tested according to JC/T1083-2008.

The cement performance index obtained by combining Example 3, Comparative Examples 1-2 and the control group is shown in Table 4 below. Table 4 shows the specific surface area, compressive strength and fluidity of the cement after grinding, where Fin, F60 and FL are respectively Initial fluidity, 60min fluidity and flow loss of cement slurry:

Table 4 Cement performance index

As can be seen from Tables 1 and 4 above, compared with the control group, the specific surface area of Example 4 has increased, indicating that the grinding aid of the present invention can increase the grinding efficiency of cement, increase the specific surface area of cement particles, and is larger than that on the market. The grinding effect of common grinding aids in Comparative Example 1 and Comparative Example 2 is due to the lack of ethyl orthosilicate silane and graphene oxide respectively. The grinding effect of the obtained grinding aids is not ideal, even lower than that of the control group. Analysis of cement activity shows that Example 4 slightly improved the early activity of cement, but significantly increased the 28d strength of cement. This shows that the grinding aid prepared by the present invention improves the grinding efficiency and increases the density of cement particles between 3-30 μm. proportion, thus increasing cement activity and improving cement 28d strength. The water-cement ratio adopted in the cement slurry test was 0.29, and the water-reducing agent content was 0.8%. Comparing the fluidity of the slurry, it was found that Example 3 significantly improved the net slurry fluidity. The fluidity of the slurry was improved, and the compatibility with the water-reducing agent was improved. However, Comparative Examples 1 and 2, which lacked tetraethyl orthosilicate silane and graphene oxide, had obvious bleeding and were not well compatible with the water-reducing agent.

In summary, combined with Examples 1, 2 and 3, it can be seen that the cement grinding aid made of silane coupling agent, ethyl orthosilicate silane and graphene oxide as main raw materials in the present invention significantly improves the grinding efficiency. , improves the activity of cement, and its fluidity is significantly improved, has good compatibility with water-reducing agents, avoids the defect of triethanolamine being incompatible with water-reducing agents, and has good adaptability with water-reducing agents, preparation The method is simple, the raw materials are easy to obtain, the price is low, and it has broad development prospects.

Specific embodiment four

As shown in Figure 1, thioglycolic acid or mercaptopropionic acid is generally used as the organic acid in the grinding aid. First, in the solution state, the organic acid in the chromium reducing agent can interact with the soluble six The oxidation-reduction reaction of valent chromium causes hexavalent chromium to be reduced to non-toxic trivalent chromium. The chemical reaction formula is:

6HSR+2Cr ⁶⁺ =3RS-SR+6H ⁺ +2Cr ³⁺

Secondly, sodium thiosulfate is used as a chromium reduction additive to synergize with the main agent to reduce chromium. The chemical reaction formula is:

In the solution state, sodium thiosulfate undergoes a redox reaction with soluble hexavalent chromium in cement, thiosulfate ions are oxidized to sulfate ions, and hexavalent chromium is reduced to non-toxic trivalent chromium.

In order to ensure the consistency of the comparison during the test, the cement grinding aid formula used in this application adopts the grinding aid formula in Specific Embodiment 2. The cement used is P.O42.5 conch cement. The various performance indicators are shown in the table. 5:

Table 5 Cement performance indicators

The test methods adopted are shown in Table 6 below:

Table 6 Cement performance test methods

A comparative experiment was conducted between the grinding aid of the present application and the existing ferrous sulfate grinding aid and suspension grinding aid to test the performance and chromium reduction effect of cement. Among them, the organic acid grinding aid prepared by the present application was used It is marked as S _A , the conventional grinding aid is marked as SB _, the ferrous sulfate grinding aid is marked as _SC , and the suspension grinding aid is marked as _SD ;

The prepared S _A and S _B were respectively mixed into the P.O42.5 cement raw material at a dosage of 0.1% to detect the specific surface area, fineness and compressive strength. The results are shown in Table 9;

The prepared S _A and S _B were mixed into the P.O42.5 cement raw material at a dosage of 1.5% to detect the mortar expansion. The results are shown in Table 7.

The prepared S _A , _SC , and _SD were added into the P.O42.5 cement raw material at a dosage of 0.1% respectively, and a control test was conducted with blank cement to compare the chromium reduction of the samples in different periods at a temperature of 25°C. Effect, and then set different temperature gradients of 80°C, 100°C, 120°C, and 140°C to observe the chromium reduction effect of the sample under different temperature conditions. The results are shown in Table 8.

Table 7 Performance test results of cement mixed with different abrasives

It can be seen from Table 7 that compared with the chromium-reducing grinding aids commonly used in the cement industry, after the organic acid composite chromium-reducing cement grinding aid prepared in this article is added to the blank cement, the cement performance, compressive strength and cement The adaptability is significantly improved.

Table 8 Test of chromium reduction effect of different grinding aids

Through experiments, it can be seen that when the prepared organic acid composite chromium-reducing cement grinding aid, ferrous sulfate grinding aid, and suspension grinding aid are 0.1%, the newly prepared organic acid composite type Chromium-reducing cement grinding aids, ferrous sulfate grinding aids, and suspension grinding aids have similar initial chromium reduction effects, all reaching more than 40%. After being left for 30d, 60d, and 90d, the organic acid compound chromium-reducing cement grinding aids There is no major change in the chromium reducing effect of the grinding aid, but the chromium reducing effect of the ferrous sulfate grinding aid and suspension grinding aid is significantly reduced. When the temperature is 25°C, the initial chromium reducing effect of each grinding aid is equivalent. When the temperature When the conditions change to 80°C, 100°C, 120°C, and 140°C, the chromium reducing effect of the organic acid composite chromium-reducing cement grinding aid does not change significantly, indicating that it is less affected by temperature, while the ferrous sulfate grinding aid, The chromium-reducing effect of the suspension grinding aid becomes significantly worse due to the influence of temperature, indicating that the organic acid compound chromium-reducing cement grinding aid has strong oxidation resistance, is suitable for long-term storage, has excellent high-temperature resistance, and can be well adapted to the cement industry. advantages of temperature changes.

To sum up, in this application, organic acid and sodium thiosulfate are added to the proportion of cement grinding aid to reduce the oxidation of internal hexavalent chromium when mixed with cement, and organic acid is used as the main chromium reducing agent. Sodium thiosulfate is used as a chromium reducing agent. The two work together to reduce chromium. The addition of organic acid effectively improves the high temperature sensitivity of sodium thiosulfate as a chromium reducing agent alone. The two work together to achieve the best chromium reducing effect. The six The valent chromium is reduced to non-toxic and harmless trivalent chromium, which not only has the excellent grinding aid effect of conventional grinding aids, but also has the added organic acid, which improves the high temperature resistance and oxidation resistance of the grinding aid, and can be used for a long time. Long-term storage avoids oxidation by oxygen during storage and affects the chromium reduction effect.

It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that these entities or operations are mutually exclusive. any such actual relationship or sequence exists between them. Furthermore, the terms "comprises," "comprises," or any other variations thereof are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but also those not expressly listed other elements, or elements inherent to the process, method, article or equipment. Without further limitation, an element defined by the statement "includes a reference structure" does not exclude the presence of additional identical elements in the process, method, article, or device that includes the element.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art will understand that various changes, modifications, and substitutions can be made to these embodiments without departing from the principles and spirit of the invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (10)

1. A preparation method of a novel cement grinding aid is characterized by comprising the following steps of: the preparation method of the grinding aid comprises the following steps:

sp1: raw material preparation, namely sequentially preparing 30-45 parts of tetraethoxysilane, 30-40 parts of silane coupling agent, 10-20 parts of ethylene glycol, 20-25 parts of deionized water, 5-8 parts of catalyst, 8-10 parts of graphene oxide, 20-25 parts of sodium thiosulfate and 15-20 parts of organic acid;

sp2: preparing a solution A, namely slowly dropwise adding tetraethoxysilane into a mixed solution of glycol and deionized water, and stirring and mixing to obtain nano SiO ₂ Sol solution A;

Sp3：preparing a solution B, namely slowly dripping a silane coupling agent into the solution A in the step Sp2, adding 5 parts of a catalyst, and stirring and mixing to obtain nano SiO ₂ A silanol solution B of the sol;

sp4: and (3) forming a grinding aid, wherein the forming of the grinding aid is to add graphene oxide solution into the solution B in the step Sp3, add sodium thiosulfate, uniformly stir for 15min, add organic acid after the sodium thiosulfate is completely dissolved, uniformly stir for 5min, stir and mix, and cool to room temperature to obtain the novel cement grinding aid.

2. The method for preparing the novel cement grinding aid according to claim 1, which is characterized by comprising the following steps: the temperature during mixing in the preparation of the solution A and the preparation of the solution B is 70 ℃, the mixing rotating speed is 100r/min, and the stirring time is 2h.

3. The method for preparing the novel cement grinding aid according to claim 1, which is characterized by comprising the following steps: the temperature of the grinding aid during mixing in the molding process is 40 ℃, the mixing rotating speed is 800r/min, the stirring time is 2h, and the preparation of the solution A, the preparation of the solution B and the molding process of the grinding aid are heated by adopting a constant-temperature water bath kettle.

4. The method for preparing the novel cement grinding aid according to claim 1, which is characterized by comprising the following steps: the silane coupling agent in the preparation of the raw materials is 3-aminopropyl triethoxysilane, and the chemical formula of the organic acid is C ₂ H ₄ O ₂ S。

5. The method for preparing the novel cement grinding aid according to claim 1, which is characterized by comprising the following steps: the graphene oxide in the preparation of the raw material is industrial graphene oxide aqueous dispersion liquid, and the solubility is 1%.

6. The method for preparing the novel cement grinding aid according to claim 1, which is characterized by comprising the following steps: the catalyst in the preparation of the raw materials is acetic acid, and the PH of the mixed solution in the preparation of the solution A and the preparation of the solution B is 4-6.

7. The novel cement grinding aid according to any one of claims 1-6, characterized in that: the grinding aid consists of 30-45 parts of tetraethoxysilane, 30-40 parts of silane coupling agent, 10-20 parts of glycol, 20-25 parts of deionized water, 5-8 parts of catalyst, 8-10 parts of graphene oxide, 20-25 parts of sodium thiosulfate and 15-20 parts of organic acid.

8. The method for preparing the novel cement grinding aid according to claim 1, which is characterized by comprising the following steps: the Sp1 step also comprises 5-10 parts of nano-scale carbon nanotubes in the raw material preparation stage.

9. The method for preparing the novel cement grinding aid according to claim 1, which is characterized by comprising the following steps: in the grinding aid forming stage in the Sp4 step, ultrasonic auxiliary stirring is adopted.

10. The method for preparing the novel cement grinding aid according to claim 1, which is characterized by comprising the following steps: and in the preparation stage of the solution B in the Sp3 step, microcapsules are built in, and the compound agent is encapsulated in the microcapsules and uniformly dispersed in the grinding aid.