In-situ composite seed crystal type early strength agent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of early strength agents, in particular to an in-situ composite seed crystal type early strength agent and a preparation method and application thereof. The in-situ composite seed crystal type early strength agent is obtained by mixing a calcareous raw material, a siliceous raw material, quick lime, a dispersing agent and water, carrying out a ball-milling reaction and then carrying out spray drying. The in-situ composite seed crystal type early strength agent comprises the following components: sodium sulfate and C-S-H seed crystal. The in-situ composite seed crystal type early strength agent is reasonable in composition, and the synergistic effect (1 + 1gt; and 2) the early strength agent is applied to high-volume slag cement, the early strength effect is remarkable, and the later strength is not reduced. The invention has the advantages of simple preparation process, cheap and easily available raw materials, low cost, small seed particle size, uniform particle size distribution, stable performance, easy storage, transportation and use, and is very suitable for industrial mass production.

Description

Technical Field

[0001] The invention relates to the technical field of early strength agents, in particular to an in-situ composite seed crystal early strength agent and a preparation method and application thereof. Background Art

[0002] The cement industry is a high carbon dioxide emission industry. Reducing carbon emissions from the cement industry is an important measure to achieve the goal of sustainable development for mankind. In order to reduce the negative impact of carbon emissions from the cement industry on the environment, the use of common bulk solid waste as auxiliary cementitious materials (granulated blast furnace slag, fly ash, steel slag, silica fume, etc.) is currently the most extensive and practical way to reduce the carbon emission problem of the cement industry and meet the growing demand for building materials. Granulated blast furnace slag (slag, GGBFS) is a by-product of steelmaking, with a huge annual output and a price far lower than cement. Compared with other auxiliary cementitious materials, slag has a higher potential hydraulic activity. Increasing the replacement amount of GGBFS in cement can not only improve the utilization rate of slag, but also has great potential for reducing carbon dioxide emissions in the cement industry. In addition to environmental benefits, high-volume slag 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-volume slag low-carbon cement is greatly reduced. In order to achieve high early strength of low-carbon cement-based materials with large amounts of slag, early strength agents or activators can be used to achieve the effect of low dosage and high early strength. However, traditional inorganic salt early strength agents such as sodium sulfate and organic salt early strength agents such as triethanolamine, while improving the early strength of cement, will mostly lead to the problem of later strength reduction. Therefore, how to develop new practical and efficient early strength means to improve the early compressive strength of cement-based materials with large amounts of slag while maintaining the later mechanical properties of cement-based materials and ensuring good workability is an important measure to ensure the necessary building materials for large-scale engineering construction, and it is also a key issue that needs to be urgently solved to realize the resource utilization of solid waste in the field of building materials. Summary of the invention

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

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

[0005] One of the technical solutions of the present invention 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% CSH seeds.

[0006] The second technical solution of the present invention is a method for preparing the in-situ composite seed crystal early strength agent, comprising the following steps:

[0007] 1-2 parts of calcium raw material, 0.8-1 parts of silicon raw material, 0-0.5 parts of quicklime and dispersant and water are mixed by mass to perform ball milling reaction to obtain an in-situ composite seed crystal early strength agent suspension slurry;

[0008] The in-situ composite crystal seed type early strength agent suspension slurry is spray-dried to obtain the in-situ composite crystal seed type early strength agent;

[0009] 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;

[0010] The amount of water added is based on a solid-liquid ratio of 0.06 to 0.12 (g / mL), wherein the solids are calcium raw materials, silicon raw materials and quicklime.

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

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

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

[0014] In a preferred embodiment of the present invention, 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 invention, 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 invention, the settings of the following key parameters are very important. Setting the key parameters beyond the range described in the present invention will lead to reduced effects. The following is a specific explanation and description of these parameters:

[0017] (1) Ball milling reaction speed

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

[0019] Too high a speed will cause excessive wear of the grinding media and raw materials, produce too much fine powder, and affect the particle distribution and performance of the final product. In addition, too high a speed will cause the equipment to overheat.

[0020] If the rotation speed is too low, the ball milling efficiency will be reduced, resulting in the failure of the raw materials to fully react and the activity of the generated in-situ composite seed-type early strength agent will be reduced, thereby affecting the early strength performance. The final product composition and performance are difficult to meet the application requirements.

[0021] (2) Ball milling reaction time

[0022] Recommended range: 60 to 120 minutes

[0023] If the reaction time is too long, the nano-scale particles formed by the reaction will grow and aggregate, affecting the dispersion of the particles and reducing the effectiveness of the early strength agent. In addition, too long a reaction time will cause thermal denaturation of the material, thereby affecting its chemical activity.

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

[0025] (3) Amount of water added (according to solid-liquid ratio)

[0026] Recommended range: 0.06~0.12

[0027] Too much water will lead to slurry dilution, affect the concentration of solid particles, cause the finished product to be too fluid, and fail to form a stable floc structure, ultimately affecting the spray effect and early strength performance of the in-situ composite crystal 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 the inability to mix and react the raw materials evenly, and the spray effect and early strength performance of the final product will be significantly reduced.

[0029] (4) Amount of dispersant added

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

[0031] Too much addition will increase the cost of the dispersant. At the same time, excessive dispersant will have a negative impact on the binding properties of the particles, affecting the stability and cost of the final product.

[0032] If the addition amount is too low, it will cause agglomeration between particles, affect the fluidity and uniformity of the mixture, be unfavorable for spray drying, and also result in the effect of improving the early strength of cement is not obvious.

[0033] The third technical solution of the present invention is that the in-situ composite seed type early strength agent is used in high-volume slag cement, and the addition amount of the in-situ composite seed type early strength agent in the high-volume slag cement is 0.2-1.0% of the total mass of the cement.

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

[0035] The in-situ composite seed early strength agent of the present invention has a reasonable composition, can give play to the synergistic effect (1+1>2) of CSH seed and traditional early strength agent, and is applied to large-volume slag cement, has significant early strength effect, and does not shrink in later strength.

[0036] The invention has simple preparation process, cheap and readily available raw materials, low cost, small seed crystal particle size and uniform particle size distribution, relatively stable performance, easy storage, transportation and use, and is very suitable for industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

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

[0040] Figure 3 This is the particle size distribution diagram of the in-situ composite seed-type early strength agent prepared in Example 1.

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

[0042] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0043] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0044] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0045] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0046] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0047] The "%" described in the present invention, unless otherwise specified, refers to mass percentage.

[0048] The "parts" described in the present invention, unless otherwise specified, all represent parts by mass.

[0049] Compared with traditional early strength agents or activators, CSH seed early strength agents are more suitable for silicate cement or ordinary silicate cement, but CSH seed early strength agents have the disadvantages of complex synthesis process, large particle size, poor early strength effect, high cost, and difficult storage, and the early strength effect of large-volume slag cement used alone is limited. The present invention is based on the synergistic effect of CSH seed crystals and traditional early strength agents (1+1>2), and uses cheap raw materials to synthesize an in-situ composite seed early strength agent with adjustable ratio, uniform component distribution, and suitable for the early strength and late strength development of large-volume slag cement.

[0050] This technical invention utilizes CSH seeds and traditional early strength agent sulfate (sodium sulfate, no or a small amount of calcium sulfate) in situ generation and use in combination, so as to achieve a synergistic effect of "1+1>2" on the strength development of large-volume slag cement. The present invention uses cheap and readily available calcium source and silicon source as raw materials, adds appropriate dispersants, and adopts ball milling assisted chemical method to prepare an in-situ composite seed early strength agent suitable for improving the strength of large-volume slag cement. The in-situ composite seed early strength agent is composed of a certain proportion of sulfate (sodium sulfate, no or a small amount of calcium sulfate) and CSH seeds, and each component of the in-situ composite seed early strength agent is uniformly generated in situ, and the component ratio is adjustable. The in-situ composite seed early strength agent of the present invention gives full play to the role of seeds, promotes the hydration and hardening of cement clinker, and sodium sulfate reacts with calcium hydroxide generated by clinker hydration to generate sodium hydroxide to increase the alkalinity of the system, thereby accelerating the dissolution and hydration reaction of slag. The synergistic effect of sulfate and seeds promotes the hydration and hardening speed of large-volume slag cement, refines the pore structure, and thus improves the strength.

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

[0052] The calcium raw material used in the embodiment of the present invention is industrial by-product desulfurization gypsum, wherein the CaO content is 44.45%, SiO 2 The content is 5.72%; the siliceous raw material used is industrial (solid) water glass, and the main parameters are 27.24% Na 2 O, 54.75% SiO 2 , solid content 81.99%, 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 1mm zirconium oxide microspheres.

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

[0054] Example 1

[0055] Add 2 parts of solid raw materials (1.1 parts of calcium raw materials + 0.9 parts of silicon raw materials) with a total mass into a planetary ball mill, then add water at a solid-liquid ratio of 0.12 (g / mL), and at the same time add 12% of the mass of the solid raw materials and 16 parts of 1mm zirconium oxide microspheres. Seal the mixture, and perform ball milling in a planetary ball mill at a speed of 400r / min for 60 minutes to assist the reaction, so as to obtain an in-situ composite crystal seed type early strength agent suspension slurry, which is spray-dried at 200°C to obtain the in-situ composite crystal seed type early strength agent.

[0056] Figure 1 This is 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 CSH and Na 2 SO 4 The diffraction peaks indicate that the in-situ composite seed-type early strength agent prepared in Example 1 does contain CSH and Na 2 SO 4 .

[0057] Figure 2 This is the FT-IR spectrum of the in-situ composite seed-type early strength agent prepared in Example 1. Figure 2 It can be seen that at 619cm -1 、1105cm -1 The absorption peaks at 4 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 type early strength agent prepared in Example 1. Figure 3 It can be seen that the average particle size of the in-situ composite seed-type early strength agent seed crystals prepared in Example 1 is 37.14 nm, and the particle size is small and evenly distributed.

[0059] Example 2

[0060] A total mass of 2.5 parts of solid raw materials (1.64 parts of calcium raw materials + 0.82 parts of silicon raw materials + 0.04 parts of quicklime) are added into a planetary ball mill, and then water is added thereto at a solid-liquid ratio of 0.12 (g / mL). At the same time, 12% of the mass of the solid raw materials as a dispersant and 16 parts of 1 mm zirconium oxide microspheres are added. The mixture is sealed and ball milled in a planetary ball mill at a ball milling speed of 500 r / min for 120 minutes to assist the reaction, and an in-situ composite crystal seed type early strength agent suspension slurry is obtained. The in-situ composite crystal seed type early strength agent is obtained after spray drying at 200°C.

[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. The tests and characterizations proved that the in-situ composite seed-type early strength agent contained seed CSH, Na 2 SO 4 and a small amount of CaSO 4 , and the seed particle size is small and the particle size distribution is uniform.

[0062] Figure 4 This is the XRD pattern of the in-situ composite seed-type early strength agent prepared in Example 2. Figure 4 It can be seen that the in-situ composite seed-type early strength agent prepared in Example 2 contains CSH, Na 2 SO 4 and CaSO 4 diffraction peaks.

[0063] Example 3

[0064] A total of 3 parts of solid raw materials (1.78 parts of calcium raw materials + 0.89 parts of silicon raw materials + 0.33 parts of quicklime) are added into a planetary ball mill, and then water is added thereto at a solid-liquid ratio of 0.12 (g / mL). At the same time, 12% of the mass of the solid raw materials as a dispersant and 16 parts of 1 mm zirconium oxide microspheres are added. The mixture is sealed and ball milled in a planetary ball mill at a ball milling speed of 500 r / min for 60 minutes to assist the reaction, and an in-situ composite crystal seed type early strength agent suspension slurry is obtained. The in-situ composite crystal seed type early strength agent is obtained after spray drying at 200°C.

[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. The tests and characterizations proved that the in-situ composite seed-type early strength agent prepared in Example 3 did contain seed CSH and Na 2 SO 4 and a small amount of CaSO 4 , and the seed particle size is small and the particle size distribution is uniform.

[0066] The in-situ composite seed-type early strength agent prepared in the above embodiment is added to a large amount of slag cement (60% slag + 40% P·O42.5, wherein the slag 28d activity index is 102%, and the early strength agent is added in an amount of 0.8% of the mass of cement). The large amount of slag cement without any early strength agent is taken as Comparative Example 1, and the large amount of slag cements added with sodium sulfate and CSH seeds are respectively taken as Comparative Examples 2 and 3 (the addition amounts of sodium sulfate and CSH seeds are 0.8% of the mass of cement, respectively). The water-cement ratio during molding is 0.3, and the size of the molded net slurry strength test block is 40mm×40mm×40mm. The compressive strength of the net slurry test block of large amount of slag cement added with different early strength agents for 1d is 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 testing the compressive strength (3d and 28d) of high-content slag cement prepared under the conditions of the in-situ composite seed-type early strength agent prepared in Example 1 with different dosages (accounting for the total mass of cement) 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 1d compressive strength / MPa 7.5 13.1 17.0 21.4 18.3 19.3

[0070] The addition amounts of the in-situ composite crystal seed type early strength agent in Comparative Examples 1 to 3 and Examples 1 to 3 in Table 1 are all the same; it can be seen from Table 1 that the 1d strength of the slag cement added with the in-situ composite crystal seed type early strength agent is better than that of Comparative Examples 1 to 3, indicating that the in-situ composite crystal seed type early strength agent has the effect of "1+1>2".

[0071] Table 2

[0072]

[0073] Table 2 shows the 3d and 28d compressive strength results of slag cement with a large amount of in-situ composite crystal seed type early strength agent prepared in Example 1 with different dosages (mass percentage of cement), which proves that the in-situ composite crystal seed type early strength agent can improve both the early strength and the later strength within the appropriate dosage range.

[0074] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

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.

2. The method for preparing the in-situ composite seed crystal early strength agent according to claim 1, characterized in that: The following steps are involved: 1-2 parts of calcium raw material, 0.8-1 parts of silicon raw material, 0-0.5 parts of quicklime and dispersant and water are mixed by mass to perform ball milling reaction to obtain an in-situ composite seed crystal early strength agent suspension slurry; The in-situ composite crystal seed type early strength agent suspension slurry is spray-dried 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 calcium raw materials, silicon raw materials and quicklime.

3. The method for preparing 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 as claimed in claim 1, characterized in that: The addition amount of the in-situ composite seed crystal type early strength agent in the high-volume slag cement is 0.2-1.0% of the total mass of the cement.

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