Concrete super-fine powder admixture early strength additive and preparation method thereof

Abstract

The application discloses a concrete superfine powder admixture early strength type additive and a preparation method thereof. The application adopts the modified silicon dioxide filter sludge prepared from silicon dioxide filter sludge, dilute hydrochloric acid and nano alpha-Fe2O3 precursor, and then mixes the modified silicon dioxide filter sludge with triethanolamine, calcium nitrate, calcium hydroxide and a polycarboxylic acid high-performance water reducing agent to prepare the concrete admixture early strength type additive. After the modification of the nano alpha-Fe2O3 precursor, the surface activity of the silicon oxide compound in the filter sludge is improved, so that the silicon oxide compound can participate in the cement hydration reaction and the early strength is improved. Further, the synthesis of the early strength type calcium silicate increases the diversity of the early strength improvement of the cement, and the early strength agent effect of sodium sulfate existing in the filter sludge is fully utilized. The three early strength effects are combined with each other, and the potential functionality of the filter sludge in producing the early strength effect is fully tapped.

Description

Technical Field

[0001] This invention relates to the fields of silica production, filter press sludge treatment, and concrete admixture additive preparation. Specifically, it relates to an early-strength additive for ultrafine concrete admixtures and its preparation method. Background Technology

[0002] With increasing emphasis on environmental protection and increasingly stringent environmental policies in my country, the treatment of industrial wastewater and solid waste is receiving greater attention. In the silica production sector, water consumption is high. To address wastewater issues, reduce production costs, and recycle water resources, numerous purification processes have been implemented. During purification, a large amount of solids in the wastewater is filtered out, forming filter press sludge. Filter press sludge is characterized by high silica and salt content, and its large production volume makes its harmless treatment and large-scale comprehensive utilization a persistent technical challenge for domestic and international manufacturers. Currently, the high salt content in filter press sludge is primarily addressed through washing, but this involves large water consumption and mainly employs evaporation and crystallization processes, indirectly resulting in high production costs and low cost-effectiveness for nano-silica, as well as high investment costs, thus reducing the competitiveness of the main product, silica. Therefore, how to achieve low-cost resource utilization and large-scale utilization of silica filter press sludge is a key research and application challenge. Currently, there is no research in this area. Summary of the Invention

[0003] In view of the problems existing in the above background technology, in order to reduce the treatment cost of filter press sludge generated in the silica production process and realize the resource utilization and large-scale application of filter press sludge, this invention proposes an early-strength additive for concrete ultrafine powder admixture and its preparation method based on the composition and characteristics of filter press sludge produced from silica.

[0004] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0005] A modified silica filter press sludge is obtained by stirring and mixing silica filter press sludge, dilute hydrochloric acid, and nano-α-Fe2O3 precursor evenly, calcining at high temperature, cooling and grinding.

[0006] The mass fractions of each raw material component are as follows:

[0007] 100 parts of silica filter press sludge

[0008] 5-10 parts dilute hydrochloric acid

[0009] 1 to 3 parts of nano-α-Fe2O3 precursor.

[0010] The specific preparation method of the modified silica filter press sludge includes: mixing the silica filter press sludge with dilute hydrochloric acid and nano-α-Fe2O3 precursor evenly, calcining at 200-400℃ for 4-6 hours, cooling to room temperature, and then grinding to a specific surface area of ​​not less than 300 m². 2 / kg;

[0011] The mass fraction of the dilute hydrochloric acid is 9-15%.

[0012] The present invention also provides an early-strength additive for ultrafine powder admixtures of concrete based on the above-mentioned modified silica filter press sludge, comprising the following components by mass parts:

[0013]

[0014] The specific preparation method of the early-strength additive for ultrafine powder admixtures of concrete according to the present invention includes the following steps:

[0015] (1) Mix the modified silica filter press sludge with calcium nitrate and calcium hydroxide in a certain proportion to obtain mixture I;

[0016] (2) Add triethanolamine and polycarboxylate superplasticizer to water and dissolve them completely to obtain mixed solution II;

[0017] (3) Stir the mixture I from step (1) and the mixed solution II from step (2) until they are evenly mixed. After further ultrasonic dispersion, heat the mixture in a water bath at 60-100°C for 24 hours under nitrogen conditions. The resulting mixed suspension is the liquid additive of the admixture. Further freeze-dry the mixed suspension to obtain the powder additive of the admixture.

[0018] The water in step (2) is 80-100 parts by mass, and its mass part basis is consistent with the mass part basis of each component in the early strength additive of concrete admixture.

[0019] The present invention has the following beneficial effects:

[0020] (1) The resource utilization and large-scale application of filter press sludge produced from nano-silica have been realized. The filter press sludge has been applied to the field of concrete admixtures, thereby improving the early strength of concrete.

[0021] (2) The surface of silica compound particles in filter press sludge is activated by hydrochloric acid. Then, the nano-α-Fe2O3 precursor is calcined at 200-400℃ and reacts with the filter press sludge to catalyze the activation effect. Through the gradual formation of nano-α-Fe2O3, the surface activity of silica compounds in filter press sludge is catalyzed on the basis of hydrochloric acid activation. Then, the pH of the reactants is adjusted by calcium hydroxide and the calcium source is provided by calcium nitrate. Under the dispersion and chelation of triethanolamine and polycarboxylic acid high-performance water-reducing agent, some early-strength calcium silicate with nanostructure can be generated.

[0022] (3) The main components of filter press sludge are silicon dioxide and sodium sulfate. The sulfate ions in the filter press sludge can play an early strength role.

[0023] (4) This invention creatively utilizes the acid treatment of filter press sludge, and further modifies it with nano-α-Fe2O3 precursor to improve the surface activity of silicon oxides in the filter press sludge, promoting its participation in cement hydration reaction and improving early strength. Furthermore, the synthesis of early-strength calcium silicate increases the diversity of early strength enhancement of cement. At the same time, it makes full use of the early-strength agent effect of sodium sulfate present in the filter press sludge itself. The three early-strength effects are combined with each other, fully exploring the potential functionality of filter press sludge to produce early-strength effects, which has obvious creativity. Specific Implementation

[0024] The present invention will be further described in detail below with reference to embodiments:

[0025] Example 1:

[0026] An early-strength additive for ultrafine powder concrete admixtures based on modified silica filter press sludge, with the following component mass percentages:

[0027]

[0028] The modified silica filter press sludge is prepared by mixing 100 parts of filter press sludge with 5 parts of dilute hydrochloric acid and 3 parts of nano-α-Fe2O3 precursor, calcining at 200°C for 6 hours, and then cooling to room temperature and grinding.

[0029] The preparation method of the early-strength additive for ultrafine powder admixtures in concrete includes the following steps:

[0030] (1) Mix the modified silica filter press sludge with calcium nitrate and calcium hydroxide in a certain proportion;

[0031] (2) Add triethanolamine and polycarboxylate superplasticizer to 80 parts of water and dissolve them completely;

[0032] (3) Stir (1) and (2) evenly, further disperse evenly by ultrasonication, heat in a water bath at 100°C for 24 hours under nitrogen conditions, and take out the mixture to obtain the liquid additive of the admixture; further freeze dry the mixture to obtain the powder additive of the admixture.

[0033] Example 2:

[0034] An early-strength additive for ultrafine powder concrete admixtures based on modified silica filter press sludge, with the following component mass percentages:

[0035]

[0036] The modified silica filter press sludge is prepared by mixing 100 parts of filter press sludge with 10 parts of dilute hydrochloric acid and 1 part of nano-α-Fe2O3 precursor, calcining at 400℃ for 4 hours, and then cooling to room temperature and grinding.

[0037] The preparation method of the early-strength additive for ultrafine powder admixtures in concrete includes the following steps:

[0038] (1) Mix the modified silica filter press sludge with calcium nitrate and calcium hydroxide in a certain proportion;

[0039] (2) Dissolve triethanolamine and polycarboxylate superplasticizer completely in 100 parts of water;

[0040] (3) Stir (1) and (2) evenly, further disperse evenly by ultrasonication, heat in a water bath at 60°C for 24 hours under nitrogen conditions, and then take out to obtain a mixed suspension. Further freeze-dry the mixed suspension to obtain the admixture powder additive.

[0041] Example 3:

[0042] An early-strength additive for ultrafine powder concrete admixtures based on modified silica filter press sludge, with the following component mass percentages:

[0043]

[0044] The modified silica filter press sludge is prepared by mixing 100 parts of filter press sludge with 8 parts of dilute hydrochloric acid and 2 parts of nano-α-Fe2O3 precursor, calcining at 300°C for 5 hours, and then cooling to room temperature and grinding.

[0045] The preparation method of the early-strength additive for ultrafine powder admixtures in concrete includes the following steps:

[0046] (1) Mix the modified silica filter press sludge with calcium nitrate and calcium hydroxide in a certain proportion;

[0047] (2) Add triethanolamine and polycarboxylate high-performance water-reducing agent to 90 parts of water and dissolve them completely;

[0048] (3) Stir (1) and (2) evenly, further disperse evenly by ultrasonication, heat in a water bath at 80°C for 24 hours under nitrogen conditions, and take out the mixture to obtain the liquid additive of the admixture; further freeze dry the mixture to obtain the powder additive of the admixture.

[0049] Application Examples

[0050] The admixture additives prepared in the above embodiments are incorporated into the admixture raw materials. If a liquid is chosen, the dosage is 5%; if a powder is chosen, the dosage is 2%. The mixture is ground for 30 minutes to obtain an ultrafine powder admixture. The admixture raw materials selected in each embodiment include three types: iron tailings slime, gold tailings slime, and tungsten tailings slime, all with a particle size of 350 μm. 2 Approximately / kg.

[0051] Comparative Example 1

[0052] No additives were added to the iron tailings mud, gold tailings mud, and tungsten tailings mud, and they were ground for 30 minutes.

[0053] Comparative Example 2

[0054] The silica filter press sludge was not modified, and all other aspects remained the same as in Example 1. The selected admixture raw material was tungsten tailings sludge.

[0055] Comparative Example 3

[0056] The difference from Example 1 is that 100 parts of filter press sludge were mixed evenly with 5 parts of dilute hydrochloric acid, calcined at 200°C for 6 hours, cooled to room temperature, and then ground to obtain the final product. No nano-α-Fe₂O₃ precursor was used. After preparing the additive, tungsten tailings sludge was selected as the admixture.

[0057] Comparative Example 4

[0058] The difference from Example 1 is that 100 parts of filter press sludge, 5 parts of dilute hydrochloric acid, and 4 parts of nano-α-Fe2O3 precursor were stirred and mixed evenly, then calcined at 200°C for 6 hours, cooled to room temperature, and ground to obtain the final product. Tungsten tailings sludge was selected as the admixture.

[0059] Comparative Example 5

[0060] The difference from Example 1 is that the incorporated nano-α-Fe2O3 precursor is replaced with α-Fe2O3, while the other conditions remain the same.

[0061] Comparative Example 6

[0062] The difference from Example 1 is that: no baking is performed, but the powder is stored at room temperature for 6 hours and then ground.

[0063] Comparative Example 7

[0064] The difference from Example 1 is that the powder was calcined at 500°C for 6 hours and then ground.

[0065] Comparative Example 8

[0066] The difference from Example 1 is that the powder was calcined at 500°C for 2 hours and then ground.

[0067] Comparative Example 9

[0068] The difference from Example 1 is that when modifying silica filter press sludge, acidification treatment is not performed in advance, and dilute hydrochloric acid is not used in the preparation of modified silica filter press sludge.

[0069] Comparative Example 10

[0070] The additive components and dosages used in Example 1 are the same, except that the grinding time after mixing with the tungsten tailings mud, the raw material for the admixture, is 20 minutes.

[0071] The activity of tailings sludge in each embodiment and comparative example was compared according to the method of the 28-day compressive strength ratio test of cement mortar in GB / T12957-2005. The admixture amount was in accordance with the provisions of standard GB / T12957-2005, and the tailings sludge and dihydrate gypsum were mixed evenly at a mass ratio of 90:10, with the total admixture amount being 30% of the cement mass.

[0072] The experiment used Shanshui 42.5 ordinary Portland cement, produced by Shandong Cement Plant. Its chemical composition is shown in Table 1.

[0073] Table 1. Main chemical composition of P.O42.5 cement (%)

[0074] W％ 20.87 6.7 3.86 58.32 4.23 0.07 0.61 2.42

[0075] According to the relevant provisions of GB / T12957-2005, the 28-day compressive strength and PAI value of each group of samples were tested, as shown in Table 2:

[0076] Table 2. Test results for each embodiment and comparative example.

[0077]

[0078]

[0079] In Table 2, comparing Examples 1-3 with Control Group 1 and Comparative Example (blank sample), it can be seen that the 1-day and 28-day compressive strength and activity index of the admixtures prepared by incorporating different tailings mud with the additives of the present invention are significantly better than those prepared without the additives of the present invention. Moreover, the 1-day and 28-day compressive strength of the admixtures is better than that of the cement mortar of the comparative example. This indicates that the additives of the present invention have a significant effect on improving the early strength and activity index of various types of tailings mud.

[0080] Let's take tungsten tailings slime as an example for further comparison:

[0081] Comparing Example 1 and Comparative Example 10, it can be seen that extending the grinding time is beneficial to increasing the specific surface area of ​​the admixture, and is beneficial to improving the early compressive strength and activity index. Further comparison of Comparative Example 1 and Comparative Example 10 shows that adding the early strength additive of the admixture prepared in this invention is beneficial to increasing the grindability of the admixture, so that its specific surface area can exceed that of the admixture without the additive within a grinding time of 20 minutes. At the same time, comparing its strength activity index shows that after adding the admixture, its early compressive strength and activity index are significantly improved.

[0082] Comparing Example 1 and Comparative Example 2, it can be seen that although the silica filter press sludge is not modified, it has little effect on improving the grindability of the admixture with early-strength additives, only reducing it by 25m. 2 / kg, but the 1-day compressive strength decreased by 18.8 MPa, the 28-day compressive strength decreased by 23.1 MPa, and the 28-day activity index decreased from 119% to 77%. It can be seen that the modified filter press sludge has a very significant effect on enhancing the activity of the admixture.

[0083] Further comparison of Example 1 with Comparative Examples 3 and 4 shows that, regardless of whether the nano-α-Fe2O3 precursor is not incorporated or an excessive amount of 4 parts of nano-α-Fe2O3 precursor is incorporated, the compressive strength and activity index of the prepared admixtures both show a significant decline. This indicates that the nano-α-Fe2O3 precursor, within an appropriate range, helps to activate the activity of the admixture and improve its early strength, but an excessive amount will have adverse effects.

[0084] Further comparison of Example 1 with Comparative Examples 5 and 3 shows that the difference in the effects of replacing the nano-α-Fe2O3 precursor with α-Fe2O3 and not incorporating the nano-α-Fe2O3 precursor on the early strength and activity index of the admixture is not significant. However, incorporating the nano-α-Fe2O3 precursor can greatly improve the early strength and activity of the admixture.

[0085] Further comparison of Example 1 with Comparative Examples 6, 7, and 8 shows that the early strength and activity of the admixtures were significantly reduced compared to Example 1 after neither high-temperature treatment nor treatment at excessively high temperatures (500°C, regardless of duration). This indicates that appropriate temperature control is crucial for improving early strength and activating activity.

[0086] Further comparison of Example 1 and Comparative Example 9 shows that when silica filter press sludge is modified without prior acidification, its early strength effect and activity activation effect after mixing with the α-Fe2O3 precursor are significantly reduced. This indicates that acidification is crucial for improving the early strength performance of silica filter press sludge by the α-Fe2O3 precursor, and both have a synergistic effect on the activity activation of silica filter press sludge.

[0087] The above results indicate that the modification of silica filter press sludge is crucial for activating the activity of admixtures. However, even without modification, the filter press sludge can achieve a 28-day activity index of 95% when used directly as an admixture. This suggests that silica filter press sludge can be used as an admixture, albeit with slightly inferior performance. Modifying silica filter press sludge, especially through acid treatment to activate the α-Fe₂O₃ precursor, enhances the surface activity of silicon oxides in the sludge, promoting their participation in cement hydration reactions and improving early strength. This fully explores the potential functionality of filter press sludge in generating early strength, demonstrating significant innovation.

Claims

1. A modified silica filter press sludge, characterized in that, It is obtained by stirring and mixing silica filter sludge, dilute hydrochloric acid, and nano-α-Fe2O3 precursor evenly, calcining at high temperature, cooling and grinding. The mass fractions of each raw material component are as follows: 100 parts of silica filter press sludge 5-10 parts dilute hydrochloric acid 1-3 parts of nano-α-Fe2O3 precursor.

2. The modified silica filter press sludge according to claim 1, characterized in that, The mass fraction of the dilute hydrochloric acid is 9-15%.

3. The method for preparing modified silica filter press sludge according to claim 1 or 2, characterized in that, include: After uniformly mixing silica filter press sludge with dilute hydrochloric acid and nano-α-Fe2O3 precursor, the mixture was calcined at 200-400℃ for 4-6 hours, cooled to room temperature, and then ground to a specific surface area of ​​not less than 300 m². 2 / kg.

4. A concrete ultrafine powder admixture with early-strength properties comprising the modified silica filter press sludge as described in claim 1 or 2, characterized in that, Based on parts by mass, it includes the following components: 100 parts of modified silica filter press sludge, 2-5 parts of triethanolamine Calcium nitrate 2-6 parts, 10-15 parts calcium hydroxide, 0.1 to 0.3 parts of polycarboxylate-based high-performance water-reducing agent.

5. The preparation method of the early-strength additive for ultrafine powder admixtures in concrete according to claim 4, characterized in that, Includes the following steps: (1) Mix the modified silica filter press sludge with calcium nitrate and calcium hydroxide in a certain proportion to obtain mixture I; (2) Add triethanolamine and polycarboxylate superplasticizer to water and dissolve them completely to obtain mixed solution II; (3) Stir the mixture I from step (1) and the mixed solution II from step (2) until they are uniformly dispersed by ultrasonication. Then, heat them in a water bath at 60~100℃ for 24 hours under nitrogen conditions and remove them to obtain a mixed suspension, which is the liquid additive of the admixture. Freeze-dry the mixed suspension to obtain the powder additive of the admixture.

6. The preparation method according to claim 5, characterized in that, The water in step (2) is 80-100 parts by mass, and its mass part standard is consistent with the mass part standard of each component in the early strength additive of ultrafine powder admixture for concrete.

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