In-situ composite seed type early strength agent, preparation method and application thereof

Abstract

The present invention relates to the technical field of early strength agents, and more particularly to a kind of in-situ composite crystal seed type early strength agent and its preparation method and application. The present invention is carried out ball milling reaction by mixing calcareous raw material, siliceous raw material, quicklime and dispersant and water, and then spray drying to obtain an in-situ composite crystal seed type early strength agent. The constituent components of the in-situ composite crystal seed type early strength agent include sodium sulfate and C-S-H seed crystals. The in-situ composite crystal seed type early strength agent of the present invention is reasonable in composition, can play the synergistic effect (1+1>2) of C-S-H seed crystals and traditional early strength agents, is applied to large-volume slag cement, and early strength effect is remarkable, and late-stage strength does not shrink. The preparation process of the present invention is simple, raw materials are cheap and easy to obtain, and cost is low, seed particle size is small and particle size distribution is uniform, performance is relatively stable, and it is easy to store, transport and use, and is very suitable for industrialized mass production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of early strength agent, in particular to an in-situ composite seed type early strength agent and a preparation method and application thereof. BACKGROUND

[0002] The cement industry is a high carbon dioxide emission industry, and reducing carbon dioxide emissions of the cement industry is an important measure to achieve the goal of human sustainable development. In order to reduce the negative impact of carbon dioxide emissions of the cement industry on the environment, using common bulk solid waste as an auxiliary cementitious material (granulated blast furnace slag, fly ash, steel slag, silica fume, etc.) is currently the most extensive and most practical way to reduce carbon dioxide emissions of the cement industry and meet the increasing demand for building materials. Granulated blast furnace slag (slag, GGBFS) is a by-product of steelmaking, with a huge annual output and a much lower price than cement. Compared with other auxiliary cementitious materials, slag has a higher potential for hydraulic activity, and increasing the replacement amount of GGBFS in cement not only improves the utilization rate of slag, but also has a huge potential for carbon dioxide emission reduction in the cement industry. In addition to environmental benefits, high-sludge cement also has significant cost advantages. However, compared with cement, the early activity of slag is significantly reduced. Therefore, when a large amount of slag replaces cement, the early strength of high-sludge low-carbon cement is greatly reduced. In order to achieve high early strength of high-sludge low-carbon cement-based materials, early strength agents or activators can be used to achieve low-dosage high-early-strength. However, traditional inorganic salt early strength agents such as sodium sulfate and organic salt early strength agents such as triethanolamine can increase the early strength of cement, but they often cause the problem of late strength reduction. Therefore, how to develop new practical and efficient early strength means to improve the early compressive strength of high-sludge cement-based materials while not losing the late mechanical properties of cement-based materials and having good workability is an important measure to ensure large-scale engineering construction of building materials, and is also a key problem that needs to be solved in the field of building materials resource utilization of solid waste. SUMMARY

[0003] Based on the above, the present application provides an in-situ composite seed type early strength agent suitable for high-sludge cement, a preparation method and application thereof.

[0004] To achieve the above object, the present application provides the following solutions:

[0005] One of the technical solutions of the present application is an in-situ composite seed type early strength agent, which comprises, by mass percentage, 15-30% sodium sulfate, 0-15% calcium sulfate and 70-75% C-S-H seed.

[0006] The second technical solution of the present application is a preparation method of the in-situ composite seed type early strength agent, comprising the following steps:

[0007] Mixing 1-2 parts of calcium raw material, 0.8-1 parts of siliceous raw material, 0-0.5 parts of quicklime and dispersant and water by mass fraction to carry out ball milling reaction, to obtain in-situ composite seed type early strength agent suspension slurry;

[0008] Spray drying the in-situ composite seed type early strength agent suspension slurry to obtain the in-situ composite seed type early strength agent;

[0009] The adding amount of the dispersant is 10-20% of the total mass of the calcium raw material, the siliceous raw material and the quicklime;

[0010] The adding amount of water is added according to a solid-liquid ratio of 0.06-0.12 (g / mL), wherein the solid is the calcium raw material, the siliceous raw material and the quicklime.

[0011] In a preferred embodiment of the present application, the calcium raw material is industrial by-product gypsum.

[0012] In a preferred embodiment of the present application, the calcium raw material is at least one of anhydrous gypsum, desulfurization gypsum, phosphogypsum and titanium gypsum.

[0013] In a preferred embodiment of the present application, the siliceous raw material is industrial water glass.

[0014] In a preferred embodiment of the present application, the dispersant is a mixture of PCE monomer and water in a mass ratio of 1:1.

[0015] In a preferred embodiment of the present application, the rotation speed of the ball milling reaction is 400-500 r / min, and the time is 60-120 min.

[0016] In the preparation method of the present application, the following key parameters are very important, and the setting of the key parameters beyond the range described in the present application will result in a decrease in effect. The following is a specific explanation and description of these parameters:

[0017] (1) Rotation speed of ball milling reaction

[0018] Recommended range: 400-500 r / min

[0019] Too high rotation speed will cause excessive wear of grinding media and raw materials, generating too much fine powder, affecting the particle distribution and performance of the final product. In addition, too high rotation speed will cause overheating of the equipment.

[0020] Too low rotation speed will reduce the ball milling efficiency, resulting in insufficient reaction of the raw materials, and the activity of the generated in-situ composite seed type early strength agent will be reduced, thereby affecting the early strength performance, and the composition and performance of the final product are difficult to meet the application requirements.

[0021] (2) Time of ball milling reaction

[0022] Recommended range: 60-120 min

[0023] Too long reaction time, the nano-particles formed by the reaction will grow up and aggregate, affecting the dispersibility of the particles, resulting in the decrease of the effectiveness of the early strength agent. In addition, too long reaction time will lead to thermal denaturation of the material, thereby affecting its chemical activity.

[0024] Too short reaction time, the reaction is not sufficient, the in-situ composite seed type early strength agent generated has low activity and poor early strength performance, which does not meet the actual application requirements.

[0025] (3) The amount of water added (according to the solid-liquid ratio)

[0026] Recommended range: 0.06-0.12

[0027] Too much water will cause the slurry to be diluted, affecting the concentration of solid particles, resulting in too strong fluidity of the finished product, which cannot form a stable micelle structure, ultimately affecting the spraying effect and early strength performance of the in-situ composite seed type early strength agent.

[0028] Too little water will cause the viscosity of the mixture to be too high, affecting the effect of ball milling, resulting in that the raw materials cannot be uniformly mixed and reacted, and the spraying effect and early strength performance of the final product will be significantly reduced.

[0029] (4) The amount of dispersant added

[0030] Recommended range: 10-20% (relative to the total mass of calcium raw materials, siliceous raw materials and quicklime)

[0031] Too high amount of addition will lead to the increase of the cost of the dispersant, and the excessive dispersant will have a negative impact on the cohesiveness of the particles, affecting the stability and cost of the final product.

[0032] Too low amount of addition will cause the aggregation between the particles, affecting the fluidity and uniformity of the mixture, which is not conducive to spray drying, and also leads to that the early strength improvement effect of the cement is not obvious.

[0033] The third technical solution of the present application, the in-situ composite seed type early strength agent is applied in large-dosage slag cement, and the amount of the in-situ composite seed type early strength agent added in the large-dosage slag cement is 0.2-1.0% of the total mass of the cement.

[0034] The present application discloses the following technical effects:

[0035] The in-situ composite seed type early strength agent has a reasonable composition, can play a synergistic effect (1+1>2) of C-S-H seed and traditional early strength agent, and has a significant early strength effect and non-reduced later strength when applied in large-dosage slag cement.

[0036] The application has simple preparation process, cheap raw materials, low cost, small crystal seed particle size, uniform particle size distribution, stable performance, and is easy to store, transport and use, and is very suitable for industrial mass production. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0038] Figure 1 XRD pattern of the in-situ composite seed type early strength agent prepared in Example 1.

[0039] Figure 2 FT-IR pattern of the in-situ composite seed type early strength agent prepared in Example 1.

[0040] Figure 3 Particle size distribution graph of the in-situ composite seed type early strength agent prepared in Example 1.

[0041] Figure 4 XRD pattern of the in-situ composite seed type early strength agent prepared in Example 2. DETAILED DESCRIPTION

[0042] The various exemplary embodiments of the present application will now be described in detail, which should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0043] It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also included in the present application. The upper limit and the lower limit of these smaller ranges can be included or excluded independently from the range.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are concerned. In the event of any conflict between the content of this specification and the documents incorporated by reference, the content of this specification will control.

[0045] Many modifications and variations of the specific embodiments of the application can be made without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application. The specification and examples are illustrative only.

[0046] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean inclusion, but not limited to, the listed material or list of materials.

[0047] The "%", as described in the present application, unless otherwise specified, means mass percentage.

[0048] The "parts", as described in the present application, unless otherwise specified, means mass parts.

[0049] Compared with traditional early strength agent or accelerator, the C-S-H crystal seed type early strength agent is more suitable for Portland cement or ordinary Portland cement, but the C-S-H crystal seed type early strength agent has the defects of complex synthesis process, large particle size, poor early strength effect, high cost, and difficult storage, and the early strength effect of the C-S-H crystal seed type early strength agent used alone in high-amount-of-mineral-slag cement is limited. The present application utilizes the synergistic effect (1+1>2) of C-S-H crystal seeds and traditional early strength agent, and uses inexpensive raw materials to synthesize in-situ composite crystal seed type early strength agent which is suitable for the early strength and late strength development of high-amount-of-mineral-slag cement.

[0050] The present application utilizes the in-situ generation of C-S-H crystal seeds and traditional early strength agent sulfate (sodium sulfate, no or small amount of calcium sulfate) for combined use, so as to realize the synergistic effect (1+1>2) of high-amount-of-mineral-slag cement strength development. The present application uses inexpensive and readily available calcium source and silicon source as raw materials, adds appropriate dispersing agent, and adopts ball milling assisted chemical method to prepare in-situ composite crystal seed type early strength agent which is suitable for the strength improvement of high-amount-of-mineral-slag cement. The in-situ composite crystal seed type early strength agent is composed of a certain proportion of sulfate (sodium sulfate, no or small amount of calcium sulfate) and C-S-H crystal seeds, and the components of the in-situ composite crystal seed type early strength agent are generated in-situ uniformly, and the component ratio is adjustable. The in-situ composite crystal seed type early strength agent of the present application fully plays the role of crystal seeds, promotes the hydration and hardening of cement clinker, the reaction of calcium hydroxide generated by the hydration of sodium sulfate and clinker generates sodium hydroxide to improve the alkalinity of the system, so as to accelerate the dissolution and hydration reaction of slag, and the synergistic effect of sulfate and crystal seeds promotes the hydration and hardening speed of high-amount-of-mineral-slag cement, refines the pore structure, and thus improves the strength.

[0051] The technical solutions described in the present application are conventional solutions in the art, and the reagents or raw materials used are purchased from commercial channels or are already disclosed, unless otherwise specified.

[0052] The calcium raw material used in the embodiment of the present invention is industrial by-product desulfurization gypsum, of which the CaO content is 44.45% and the SiO2 content is 5.72%; the siliceous raw material used is industrial (solid) water glass, the main parameters of which are 27.24% Na2O, 54.75% SiO2, solid content 81.99%, and modulus 2.07; the dispersant used is a mixture of PCE monomer (Chinese name: polycarboxylate water reducer) and deionized water in a mass ratio of 1:1; the grinding body used is 1 mm zirconium oxide microspheres.

[0053] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0054] Example 1

[0055] A total mass of 2 parts of solid raw materials (1.1 parts of calcium raw materials + 0.9 parts of silicon raw materials) were added to a planetary ball mill, and then water was added thereto at a solid-liquid ratio of 0.12 (g / mL). At the same time, a dispersant of 12% of the mass of the solid raw materials and 16 parts of 1mm zirconium oxide microspheres were added. The mixture was sealed and ball milled in a planetary ball mill at a speed of 400 r / min for 60 minutes to assist the reaction, thereby obtaining an in-situ composite crystal seed type early strength agent suspension slurry. The in-situ composite crystal seed type early strength agent was obtained after spray drying at 200°C.

[0056] Figure 1 The XRD pattern of the in-situ composite seed-type early strength agent prepared in Example 1. Figure 1 It can be seen that the sample contains diffraction peaks of CSH and Na2SO4, indicating that the in-situ composite seed-type accelerator prepared in Example 1 does contain CSH and Na2SO4.

[0057] Figure 2 This is the FT-IR spectrum of the in-situ composite seed crystal early strength agent prepared in Example 1. Figure 2 It can be seen that at 619cm -1 、1105cm -1 The absorption peaks are attributed to SO4 2- Asymmetric and symmetric stretching vibration modes, 671 cm -1 The absorption peak at 864 cm is the Si-O bending vibration mode. -1 (Q1), 968cm -1 The absorption peak at (Q2) is attributed to the Si-O stretching vibration peak in CSH.

[0058] Figure 3 This is the particle size distribution diagram of the in-situ composite seed crystal early strength agent prepared in Example 1. Figure 3 It can be seen that the average particle size of the in-situ composite seed crystal type early strength agent seed prepared in Example 1 is 37.14 nm, and the particle size is small and evenly distributed.

[0059] Example 2

[0060] The total mass of 2.5 parts of solid raw materials (1.64 parts of calcareous raw materials + 0.82 parts of siliceous raw materials + 0.04 parts of quicklime) was added to a planetary ball mill tank, and water was added at a solid-liquid ratio of 0.12 (g / mL), while 16 parts of 1mm zirconia microspheres and 12% of the mass of the solid raw materials were added as dispersants, sealed, and ball-milled in a planetary ball mill at a ball milling speed of 500r / min for 120min to obtain a suspension slurry of in-situ composite seed type early strength agent, which was then spray dried at 200°C to obtain the in-situ composite seed type early strength agent.

[0061] The in-situ composite seed type early strength agent prepared in Example 2 was tested and characterized by XRD, FT-IR, and particle size distribution, etc. The tests and characterization proved that the in-situ composite seed type early strength agent contained seed C-S-H, Na2SO4, and a small amount of CaSO4, and the seed particle size was small and the particle size distribution was uniform.

[0062] Figure 4 The XRD pattern of the in-situ composite seed type early strength agent prepared in Example 2 is shown in Figure 2. Figure 4 As can be seen, the in-situ composite seed type early strength agent prepared in Example 2 contains diffraction peaks of C-S-H, Na2SO4, and CaSO4.

[0063] Example 3

[0064] The total mass of 3 parts of solid raw materials (1.78 parts of calcareous raw materials + 0.89 parts of siliceous raw materials + 0.33 parts of quicklime) was added to a planetary ball mill tank, and water was added at a solid-liquid ratio of 0.12 (g / mL), while 16 parts of 1mm zirconia microspheres and 12% of the mass of the solid raw materials were added as dispersants, sealed, and ball-milled in a planetary ball mill at a ball milling speed of 500r / min for 60min to obtain a suspension slurry of in-situ composite seed type early strength agent, which was then spray dried at 200°C to obtain the in-situ composite seed type early strength agent.

[0065] The in-situ composite seed type early strength agent prepared in Example 3 was tested and characterized by XRD, FT-IR, and particle size distribution, etc. The tests and characterization proved that the in-situ composite seed type early strength agent prepared in Example 3 indeed contained seed C-S-H, Na2SO4, and a small amount of CaSO4, and the seed particle size was small and the particle size distribution was uniform.

[0066] The in-situ composite seed type early strength agent prepared in the above examples was added to a large amount of slag cement (60% slag + 40% P·O42.5, wherein the 28d activity index of the slag is 102%, and the early strength agent is added in an amount of 0.8% of the mass of the cement). A large amount of slag cement without any early strength agent was used as Comparative Example 1, a large amount of slag cement with only sodium sulfate and C-S-H seed was used as Comparative Examples 2 and 3 (the addition amount of sodium sulfate and C-S-H seed was 0.8% of the mass of the cement, respectively), the water-cement ratio during molding was 0.3, the size of the molded paste strength test block was 40mmx40mmx40mm, the 1d compressive strength of the paste test block of the large amount of slag cement with different early strength agents was tested (the test standard refers to the cement mortar strength test method (ISO method) GB / T17671-2021), and the strength results are shown in Table 1.

[0067] The results of the compressive strength (3d and 28d) of the large amount of slag cement prepared under the condition of different amounts (accounting for the total mass of the cement) of the in-situ composite seed type early strength agent prepared in Example 1 are shown in Table 2.

[0068] Table 1

[0069] Sample Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 1 d Compressive Strength / MPa 7.5 13.1 17.0 21.4 18.3 19.3

[0070] The addition amount of the in-situ composite seed type early strength agent in Comparative Examples 1-3 and Examples 1-3 in Table 1 is the same; as can be seen from Table 1, the 1d strength of the slag cement with the in-situ composite seed type early strength agent is better than that of Comparative Examples 1-3, indicating that the in-situ composite seed type early strength agent has the effect of “1+1>2”.

[0071] Table 2

[0072]

[0073] Table 2 is the 3d and 28d compressive strength results of the large amount of slag cement with different amounts (accounting for the mass percentage of the cement) of the in-situ composite seed type early strength agent prepared in Example 1, which proves that the in-situ composite seed type early strength agent can improve the early strength and also can improve the later strength within the appropriate addition amount range.

[0074] The above examples only describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. An in-situ composite seed crystal early strength agent, characterized in that: Calculated by mass percentage, the composition of the in-situ composite seed crystal early strength agent includes 15-30% sodium sulfate, 0-15% calcium sulfate and 70-75% CSH seed crystals; The preparation method of the in-situ composite seed crystal early strength agent comprises the following steps: Calculated by weight, 1 to 2 parts of calcium raw material, 0.8 to 1 part of silicon raw material, 0 to 0.5 parts of quicklime and dispersant and water are mixed and ball-milled to obtain an in-situ composite seed crystal early strength agent suspension slurry; spray drying the in-situ composite crystal seed type early strength agent suspension slurry to obtain the in-situ composite crystal seed type early strength agent; The amount of the dispersant added is 10-20% of the total mass of the calcium raw material, the silicon raw material and the quicklime; The amount of water added is based on a solid-liquid ratio of 0.06 to 0.12, wherein the solids are calcareous raw materials, siliceous raw materials and quicklime.

2. The method for preparing the in-situ composite seed crystal early strength agent according to claim 1, wherein The following steps are involved: Calculated by weight, 1 to 2 parts of calcium raw material, 0.8 to 1 part of silicon raw material, 0 to 0.5 parts of quicklime and dispersant and water are mixed and ball-milled to obtain an in-situ composite seed crystal early strength agent suspension slurry; spray drying the in-situ composite crystal seed type early strength agent suspension slurry to obtain the in-situ composite crystal seed type early strength agent; The amount of the dispersant added is 10-20% of the total mass of the calcium raw material, the silicon raw material and the quicklime; The amount of water added is based on a solid-liquid ratio of 0.06 to 0.12, wherein the solids are calcareous raw materials, siliceous raw materials and quicklime.

3. The preparation method of the in-situ composite seed crystal early strength agent according to claim 2, characterized in that: The calcium raw material is industrial by-product gypsum.

4. The method for preparing the in-situ composite seed crystal early strength agent according to claim 3, characterized in that: The calcium raw material is at least one of anhydrous gypsum, desulfurized gypsum, phosphogypsum and titanium gypsum.

5. The method for preparing the in-situ composite seed crystal early strength agent according to claim 2, characterized in that: The siliceous raw material is industrial water glass.

6. The method for preparing the in-situ composite seed crystal early strength agent according to claim 2, characterized in that: The dispersant is a mixture of PCE monomer and water in a mass ratio of 1:

1.

7. The method for preparing the in-situ composite seed crystal early strength agent according to claim 2, characterized in that: The ball milling reaction has a rotation speed of 400 to 500 r / min and a time of 60 to 120 min.

8. The use of the in-situ composite seed-type early strength agent in high-volume slag cement according to claim 1, characterized in that: The addition amount of the in-situ composite seed crystal early strength agent in the high-content slag cement is 0.2-1.0% of the total mass of the cement.

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