Solid waste-based green nano-composite seed early strength agent and preparation method thereof

Abstract

The application discloses a solid waste-based green nano composite crystal seed early strength agent and a preparation method thereof, and relates to a green and environment-friendly crystal seed early strength agent.The solid waste-based green nano composite crystal seed early strength agent comprises the following raw materials in parts by weight: 200-300 parts of deionized water, 100-150 parts of a dispersing agent, 200-300 parts of a Ca(NO3)2 solution, 100-200 parts of a Na2CO3 solution, 50-100 parts of steel slag powder and 50-140 parts of waste concrete recycled micro powder.The solid waste-based green nano composite crystal seed early strength agent disclosed by the application uses the steel slag powder and the waste concrete recycled micro powder as raw materials, is low in cost, reduces the environmental pollution caused by solid waste, is green and environment-friendly, and is simple in process.

Description

Technical Field

[0001] This invention relates to an early strength agent, and more particularly to a seed early strength agent, specifically to a solid waste-based green nanocomposite seed early strength agent and its preparation method. Background Technology

[0002] In cement-based materials, nano-CSH nucleation early-strength agents and nano-calcium carbonate early-strength agents enhance the early strength of cement-based materials through a dual mechanism: firstly, nanoparticles act as heterogeneous nucleation sites, reducing the nucleation barrier of CSH gel and accelerating the hydration reaction rate of cement clinker minerals; secondly, calcium carbonate particles with high specific surface area can be adsorbed onto the surface of cement particles, promoting ion migration and precipitation crystallization, rapidly constructing a dense microstructure, and achieving a significant improvement in early strength. This is particularly suitable for engineering scenarios requiring rapid demolding, such as low-temperature construction and precast components, aligning with the development direction of green building materials. However, the preparation of traditional nano-CSH nucleation early-strength agents and nano-calcium carbonate early-strength agents typically relies on high-purity chemical raw materials (such as sodium silicate and calcium nitrate), resulting in high raw material costs and complex processes. Chemical synthesis requires the purchase of expensive calcium and silicon sources, making it uneconomical; furthermore, the synthesis process easily generates saline wastewater or waste residue, posing a risk of secondary pollution.

[0003] Steel slag and waste concrete powder possess significant resource utilization potential. Chemical composition analysis shows that both generally contain over 60% CaO+SiO2 (waste concrete powder contains a large amount of CSH gel and calcium hydroxide). Mineral composition analysis indicates that calcium silicate minerals such as C3S (specifically 3CaO·SiO2) and C2S (specifically 2CaO·SiO2) account for 40-60% of steel slag, while waste concrete powder retains the characteristics of cement hydration products (calcium hydroxide, CSH gel). This unique chemical and mineral composition provides a good material basis for preparing nano-calcium carbonate-nano-CSH crystal nucleus composite seed-type early-strength agents. Existing technologies have reported the use of recycled waste concrete powder as a raw material for early-strength agents, but there is no record of it being used simultaneously with steel slag as a raw material for early-strength agents. Summary of the Invention

[0004] The first technical problem solved by this invention is to provide a solid waste-based green nanocomposite seed early strength agent.

[0005] The second technical problem solved by this invention is to provide a method for preparing a solid waste-based green nanocomposite seed early strength agent.

[0006] The technical solution of this invention to solve the first technical problem is a solid waste-based green nanocomposite seed early strength agent, comprising the following raw materials in parts by weight: 200-300 parts deionized water, 100-150 parts dispersant, 200-300 parts Ca(NO3)2 solution, 100-200 parts Na2CO3 solution, 50-100 parts steel slag powder and 50-140 parts recycled waste concrete micro powder.

[0007] In this invention, the solid waste-based green nanocomposite seed early strength agent can also be composed of the above-mentioned raw materials.

[0008] Preferably, the dispersant is composed of a polycarboxylate superplasticizer and a silane coupling agent KH 550, wherein the solid content of the polycarboxylate superplasticizer is 25-30%, the solid content of the silane coupling agent is 25-30%, and the mass ratio of the polycarboxylate superplasticizer to the silane coupling agent is 5:6 to 6:5.

[0009] Preferably, the mass fraction of the Ca(NO3)2 solution is 30-50%.

[0010] Preferably, the Na2CO3 solution has a mass fraction of 20-30%.

[0011] Preferably, the solid waste powder contains 20-25% SiO2 and 40-60% CaO.

[0012] Preferably, the specific surface area of ​​the solid waste powder is 400-450 cm². 2 / g.

[0013] The technical solution of this invention to solve the second technical problem is a method for preparing the above-mentioned solid waste-based green nanocomposite seed early strength agent, comprising the following steps:

[0014] S1, calcium source precipitation and silicon source dissolution:

[0015] Waste concrete recycled powder and / or steel slag powder are reacted with sodium carbonate solution under high-speed stirring.

[0016] S2. Solid-liquid separation to obtain the first reaction solution:

[0017] After solid-liquid separation, the suspension after step S1 was subjected to solid-liquid separation to obtain high-content calcium carbonate powder and the first reaction solution, respectively.

[0018] S3. Concentrate the solution to obtain the second reaction solution:

[0019] The first reaction solution obtained in step S2 is heated and concentrated to obtain the second reaction solution;

[0020] S4. Co-precipitation of the second reaction solution with Ca(NO3)2 solution:

[0021] Water and dispersant were added sequentially to a reaction vessel and stirred until a mixed solution was obtained. Ca(NO3)2 solution and a second reaction solution were then added dropwise to the mixed solution to obtain a solid waste-based green nanocomposite seed early strength agent.

[0022] Preferably, in step S1, the solid-liquid ratio of waste concrete recycled powder and steel slag powder to sodium carbonate solution is 0.8-1g / 10ml, the reaction temperature is 60-80℃, the reaction time is 6-10h, and the stirring is carried out at high speed throughout the process with the speed controlled at 1000-1200rpm.

[0023] Preferably, in step S3, the heating state controls the reaction liquid to remain in a boiling state, and the stirring is carried out at high speed throughout the process with the speed controlled at 200-300 rpm, so that the mass fraction of sodium silicate in the concentrated solution is 30-40%.

[0024] Preferably, in step S4, the reaction temperature is controlled at 30-40℃, the high-speed stirring state is maintained and the speed is controlled at 600-800 rpm, and the reaction time is 3-4 hours.

[0025] In the preparation method of a solid waste-based green nanocomposite seed early strength agent of the present invention, steps S1-S4 are specifically used in combination. In step S1, the calcium source in the solid waste is reacted to generate calcium carbonate precipitate, while the silicon source is dissolved to generate sodium silicate solution. The present invention strictly controls the reaction temperature, specimen and stirring rate in S2 to ensure that the calcium source is fully precipitated and the silicon source is fully dissolved. After solid-liquid separation in step S2, the obtained first reaction solution is a mixed solution of sodium silicate, sodium hydroxide and sodium carbonate. In step S3, the first reaction solution is heated and concentrated to obtain a second reaction solution containing a high concentration of sodium silicate. In step S4, the second reaction solution and Ca(NO3)2 solution are simultaneously and gradually added dropwise to an aqueous solution containing a dispersant to react and generate nano-CSH crystal nuclei and nano-calcium carbonate crystal nuclei, thereby obtaining the solid waste-based green nanocomposite seed early strength agent.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) The solid waste-based green nanocomposite seed early strength agent provided by the present invention can utilize steel slag powder and waste concrete recycled micro powder to reduce the pollution of solid waste to the environment and promote the green development of the construction industry.

[0028] (2) The powder obtained by solid-liquid separation in step S2 contains a large amount of calcium carbonate and can be directly used as a mineral admixture for concrete. The first reaction liquid obtained in step S2 is directly concentrated and then used for co-precipitation to synthesize nano-CSH crystal nuclei and nano-calcium carbonate crystal nuclei without generating wastewater and waste residue. It can effectively shorten the cement setting time and significantly improve the compressive strength of concrete within one day, with the most significant improvement at 6 hours, reaching 260% to 400%. By reusing the calcium sources in the mineral phases such as calcium hydroxide, calcium-containing admixtures, calcium silicate and calcium ferrite in the recycled micro powder and steel slag, the use of calcium nitrate, calcium chloride and calcium acetate as calcium sources can be indirectly reduced. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a flowchart of a method for preparing a solid waste-based green nanocomposite seed early strength agent provided in this invention. Detailed Implementation

[0031] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0032] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0033] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0034] The formulation components of Examples 1-4 and Comparative Examples 1-5 are shown in Table 1.

[0035] Table 1 Formulation components of Examples 1-4 and Comparative Examples 1-5

[0036]

[0037]

[0038] The preparation method of the above-mentioned solid waste-based green nanocomposite seed early strength agent is as follows: Figure 1As shown, the steps are as follows:

[0039] S1, Calcium source precipitation and silicon source dissolution of recycled waste concrete powder

[0040] The waste concrete recycled powder and steel slag powder with the required solid-liquid ratio are reacted with sodium carbonate solution under high-speed stirring.

[0041] S2. Solid-liquid separation to obtain the first reaction solution.

[0042] After solid-liquid separation, the suspension after step S1 was subjected to solid-liquid separation to obtain high-content calcium carbonate powder and the first reaction solution, respectively.

[0043] S3. Concentrate the solution to obtain the second reaction solution.

[0044] The first reaction solution obtained in step S2 is heated and concentrated to obtain the second reaction solution;

[0045] S4, co-precipitation of the second reaction solution:

[0046] Water and dispersant were added sequentially to a reaction vessel and stirred until a mixed solution was obtained. Ca(NO3)2 solution and a second reaction solution were then added dropwise to the mixed solution to obtain a solid waste-based green nanocomposite seed early strength agent.

[0047] In step S1, the specific surface area of ​​the recycled waste concrete powder is 400-450 cm². 2 / g

[0048] In step S1, the sodium carbonate solution has a mass fraction of 20-30%, a solid-liquid ratio of 0.8-1 g / 10 ml, a reaction temperature of 60-80℃, a reaction time of 6-10 h, and is stirred at high speed throughout with the speed controlled at 1000-1200 rpm.

[0049] In step S2, the powder obtained after solid-liquid separation is washed with water and then dried at 105°C, and can be used as a mineral admixture for concrete.

[0050] In step S3, the heating and concentration conditions are to control the reaction liquid to remain boiling, and to stir at high speed throughout the process with the speed controlled at 200 rpm, so that the mass fraction of sodium silicate in the concentrated solution is 30-40%.

[0051] Before co-precipitation in step S4, the pH value of the second reaction solution is not lower than 13.

[0052] In step S4, the mass fraction of the Ca(NO3)2 solution is 30-50%.

[0053] In step S4, the reaction parameters are controlled as follows: temperature 30-40℃, high-speed stirring is maintained and the speed is controlled at 600-800 rpm, and the reaction time is 3-4 hours.

[0054] The preparation process of the recycled micro powder and steel slag described in the embodiments of the present invention is as follows:

[0055] (2) The preparation process of recycled micro powder mainly includes crushing and screening waste concrete blocks to remove impurities and adjust particle size, followed by grinding to refine the particles (specific surface area 400-450 cm²). 2 / g) and is activated to enhance its activity. Finally, it is dried to remove moisture and stored to ensure its performance in subsequent applications.

[0056] (2) The preparation process of steel slag powder mainly includes pretreatment of steel slag to remove impurities and adjust particle size, followed by grinding to refine the particles (specific surface area 400-450 cm²). 2 The steel slag is processed using a classifying process to separate highly active mineral micro-powders, which are then chemically modified to enhance their properties. The classifying process mainly includes pretreatment (such as slag-iron separation, crushing, and magnetic separation), grinding (using equipment such as ball mills, roller presses, or vertical mills), grading (using a classifier to separate fine and coarse powders), iron removal (installing multiple iron removal devices to remove metallic iron), and drying and conveying. Chemical modification methods include using chemical activators (such as phosphoric acid and formic acid) to improve the hydration activity of the steel slag. Finally, it is stored in a finished product silo for subsequent use.

[0057] Mortar specimens prepared according to the proportions in Table 1 were prepared in accordance with the "Test Method for Strength of Cement Mortar (ISO Method)". The 1-day strength of the mortar without nanocrystal nuclei was 7.9 MPa. The strength improvement rate of the examples and comparative examples was calculated based on this strength. The results are shown in Table 2.

[0058] Table 2

[0059]

[0060] The above examples and comparative results show that CSH nuclei prepared using steel slag alone as a silicon source are significantly more effective than recycled waste concrete powder in improving mortar strength, but still not as effective as the combination of steel slag and recycled powder. The main reason is that the recycled waste concrete powder contains low levels of reactive calcium silicate minerals and hydrated calcium silicate, resulting in a limited effective silicon source for extraction. Combining steel slag with recycled powder not only improves the strength-enhancing efficiency of CSH nuclei but also increases the resource utilization rate of the recycled powder. This synergistic enhancement effect is attributed to the reduction in silicon concentration in the second reaction solution due to the introduction of recycled powder, which helps to reduce the nucleus particle size and further improves its early activity and dispersibility.

[0061] The above-described embodiments are merely two examples illustrating the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A solid waste-based green nanocomposite seed early strength agent, characterized in that, The components, by weight, include: 200-300 parts deionized water, 100-150 parts dispersant, 200-300 parts Ca(NO3)2 solution, 100-200 parts Na2CO3 solution, 50-100 parts steel slag powder, and 50-140 parts recycled waste concrete powder; the dispersant is composed of polycarboxylate superplasticizer and silane coupling agent, the solid content of polycarboxylate superplasticizer is 25-30%, the solid content of silane coupling agent is 25-30%, and the mass ratio of polycarboxylate superplasticizer to silane coupling agent is 5:6 to 6:5; Its preparation method includes the following steps: S1. Waste concrete recycled powder and steel slag powder are reacted with Na2CO3 solution under high-speed stirring. S2. After solid-liquid separation, the suspension after the reaction in step S1 is used to obtain calcium carbonate powder and the first reaction solution, respectively. S3. Heat and concentrate the first reaction solution obtained in step S2 to make the mass fraction of sodium silicate in the concentrated solution 30-40% to obtain the second reaction solution. S4. Deionized water and dispersant are added sequentially to the reaction vessel and stirred until a mixed solution is obtained. Ca(NO3)2 solution and the second reaction solution are added dropwise to the mixed solution at the same time, and co-precipitation is carried out to obtain solid waste-based green nanocomposite seed early strength agent.

2. The solid waste-based green nanocomposite seed early strength agent according to claim 1, characterized in that, The mass fraction of the Ca(NO3)2 solution is 30-50%.

3. The solid waste-based green nanocomposite seed early strength agent according to claim 1, characterized in that, The Na2CO3 solution has a mass fraction of 20-30%.

4. The solid waste-based green nanocomposite seed early strength agent according to claim 1, characterized in that, The specific surface area of ​​the steel slag powder or recycled waste concrete powder is 400-450 cm². 2 / g.

5. The solid waste-based green nanocomposite seed early strength agent according to claim 1, characterized in that, In step S1, the solid-liquid ratio of waste concrete recycled powder and steel slag powder to Na2CO3 solution is 0.8-1g / 10ml, the reaction temperature is 60-80℃, the reaction time is 6-10h, and the entire process is carried out with high-speed stirring and the speed is controlled at 1000-1200rpm.

6. The solid waste-based green nanocomposite seed early strength agent according to claim 1, characterized in that, In step S3, the heating state is controlled to keep the reaction liquid at a boiling state, and the stirring speed is controlled at 200-300 rpm.

7. The solid waste-based green nanocomposite seed early strength agent according to claim 1, characterized in that, In step S4, the reaction temperature is controlled at 30-40℃, the stirring speed is controlled at 600-800 rpm, and the reaction time is 3-4 hours.

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