Cement-based material with high mechanical property and chlorine fixation property and preparation method of cement-based material

Abstract

The invention discloses a cement-based material with high mechanical properties and chlorine fixation performance and a preparation method thereof.The cement-based material is composed of polyethylene glycol grafted carbon dots, mixing water and Portland cement, and the preparation method comprises the following steps that polyethylene glycol, citric acid and ethidene diamine serve as raw materials and are mixed with water according to the mass ratio, and a solid-liquid mixture is obtained; heating the solid-liquid mixture at 140-200 DEG C for 4-10 hours by adopting a hydrothermal method to obtain an initial product, and purifying and drying the initial product to obtain polyethylene glycol grafted carbon dots; dissolving the polyethylene glycol grafted carbon dots in mixing water according to a mass ratio to obtain a polyethylene glycol grafted carbon dot solution; and mixing the polyethylene glycol grafted carbon dot solution with Portland cement according to a mass ratio, and stirring to obtain the cement-based material with high mechanical property and chlorine fixing property. The cement-based material with high mechanical property and chlorine fixing property is simple to prepare, low in cost and environment-friendly, and the mechanical property and chloride ion curing property of the cement-based material can be remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, in particular to a cement-based material with high mechanical properties and chlorine-fixing properties and a preparation method thereof. Background Art

[0002] In the field of construction engineering, cement-based materials are widely used due to their excellent mechanical properties and durability. However, as the engineering use environment becomes increasingly complex, cement-based materials face increasingly severe challenges such as chloride ion corrosion and mechanical property degradation. These problems will reduce the durability of cement-based materials, thus affecting the overall safety and service life of the building.

[0003] Chloride ion corrosion is one of the main causes of steel corrosion in concrete structures. As chloride ions gradually penetrate into the concrete, when their concentration exceeds the critical value, the passivation film on the surface of the steel bar will be destroyed, thereby initiating a corrosion reaction. This not only weakens the bond between the steel bar and the concrete, but also causes the steel bar to expand, causing cracking and spalling of the concrete, seriously affecting the bearing capacity and durability of the structure. In addition, the mechanical properties of cement-based materials determine their performance in engineering applications to a certain extent. Although traditional reinforcement methods such as adding admixtures and fibers can improve the mechanical properties of cement-based materials to a certain extent, it is difficult to effectively improve the chloride ion curing performance at the same time. Therefore, effective measures should be taken to enhance the ability of cement-based materials to resist chloride ion corrosion while maintaining or improving the mechanical properties.

[0004] In recent years, functionalized nanomaterials have provided new ideas for solving the above problems. Among them, modifying cement-based materials through nanotechnology to improve their mechanical properties and chloride ion curing properties has become an effective strategy. However, nanomaterials often face problems such as poor dispersibility and easy agglomeration in cement systems with high alkalinity and high metal ion concentrations, which affects their full function. Carbon dots, as a new type of nanomaterial, are easy to synthesize, low-cost and highly fractionable, and are expected to be used in the nanotechnology of cement-based materials. In order to further improve the dispersibility of carbon dots in cement-based materials, polymers can be grafted on their surface to further disperse the carbon dots through the steric hindrance effect brought by the polymers. Summary of the invention

[0005] The purpose of the present invention is to provide a cement-based material with high mechanical properties and chlorine-fixing properties and a preparation method thereof, which can enhance the ability of the cement-based material to resist chloride ion corrosion while maintaining or improving the mechanical properties of the cement-based material, and solve the problems of poor dispersibility and high preparation cost of conventional nanomaterials used to modify cement-based materials.

[0006] To achieve the above object, the present invention provides the following technical solution: a cement-based material with high mechanical properties and chlorine-fixing properties and a preparation method thereof, which consists of three parts: polyethylene glycol grafted carbon dots, mixing water, and silicate cement. The specific preparation steps are as follows:

[0007] Step 1: Using polyethylene glycol, citric acid and ethylenediamine as raw materials, the raw materials are mixed with water according to a mass ratio to obtain a solid-liquid mixture.

[0008] Step 2: Using a hydrothermal method, the solid-liquid mixture described in step 1 is heated at 140-200° C. for 4-10 hours to obtain an initial product, and the initial product is purified and dried to obtain polyethylene glycol-grafted carbon dots.

[0009] Step 3: dissolving the polyethylene glycol grafted carbon dots described in step 2 in mixing water according to the mass ratio to obtain a polyethylene glycol grafted carbon dots solution.

[0010] Step 4: Mix the polyethylene glycol grafted carbon dot solution described in step 3 with silicate cement in a mass ratio, and stir to obtain a cement-based material with high mechanical properties and chlorine-fixing properties.

[0011] The mass ratio of the above-mentioned polyethylene glycol grafted carbon dots, mixing water, and silicate cement is (0.01-0.1):(0.3-0.5):1.

[0012] Preferably, in step 1, the mass ratio of polyethylene glycol, citric acid and ethylenediamine is 1:2-5:5-10.

[0013] Preferably, the molecular weight of the polyethylene glycol is 200-2000.

[0014] Preferably, the purification step in step 2 includes centrifugation, suction filtration, dialysis, and rotary evaporation.

[0015] Preferably, the stirring time in step 4 is 4 to 8 minutes.

[0016] Therefore, the present invention adopts a cement-based material with high mechanical properties and chlorine-fixing properties and a preparation method thereof, which has the following beneficial effects:

[0017] (1) Compared with the traditional method of improving the mechanical properties and chloride ion curing performance of cement-based materials, the cement-based material with high mechanical properties and chlorine-fixing performance and the preparation method thereof provided by the present invention have the characteristics of simple preparation, low cost, and environmental protection, and can significantly improve the mechanical properties and chloride ion curing performance of cement-based materials.

[0018] (2) Compared with carbon dots without polyethylene glycol grafting, carbon dots grafted with polyethylene glycol can not only exert the molecular characteristics of polyethylene glycol, but also give full play to the nanomaterial properties of carbon dots. Grafting polyethylene glycol on the surface of carbon dots can significantly improve the dispersibility of carbon dots and their stability in cement-based materials. The polyethylene glycol molecular chain enables it to exert a steric hindrance effect in a high-alkali and high-metal ion environment. The polyethylene glycol molecular chain grafted to the surface of carbon dots forms a "protective shell" that can effectively prevent the agglomeration caused by van der Waals forces and electrostatic effects between carbon dots in the high-alkali environment of cement-based materials, thereby giving full play to the nucleation effect of carbon dots.

[0019] (3) The polyethylene glycol grafted carbon dots added in the present invention can give full play to their nucleation effect in the cement matrix, provide more nucleation sites, promote the nucleation, precipitation and growth of cement hydration products, and thus promote the formation of cement hydration products calcium silicate hydrate (CSH) and calcium aluminate hydrate (AFm) phases. CSH can physically adsorb chloride ions through electrostatic force and van der Waals force, and the AFm phase can chemically combine with chloride ions to form Friedel salts. Therefore, the cement-based material after adding polyethylene glycol grafted carbon dots can form more CSH and Friedel salts, thereby significantly improving its chloride ion curing performance. In addition, the hydration products generated by the cement-based material after adding polyethylene glycol grafted carbon dots are intertwined and evenly distributed, making the internal structure of the hardened cement paste more compact and the internal pore structure more refined, thereby improving the mechanical properties of the cement-based material. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a preparation flow chart of Example 1 of the present invention.

[0021] Figure 2 This is a transmission electron microscope (TEM) image of the polyethylene glycol grafted carbon dots prepared in Example 1 of the present invention.

[0022] Figure 3 These are the mechanical property test results of Examples 1, 2, 3, 4 of the present invention and Comparative Examples 1 and 2.

[0023] Figure 4 These are the chloride ion curing performance test results of Examples 1, 2, 3, 4 of the present invention and Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0024] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and a specific operation process, but the present invention is not limited to this embodiment.

[0025] Example 1

[0026] A cement-based material with high mechanical properties and chlorine-fixing properties and a preparation method thereof, comprising polyethylene glycol grafted carbon dots, mixing water, and silicate cement. The specific preparation steps are as follows: Figure 1 As shown:

[0027] Step 1: Using polyethylene glycol with a molecular weight of 200, citric acid and ethylenediamine as raw materials, the above raw materials are mixed with water in a mass ratio of 1:5:10 to obtain a solid-liquid mixture.

[0028] Step 2: Using a hydrothermal method, the solid-liquid mixture described in step 1 is heated at 160° C. for 6 hours to obtain an initial product, and the initial product is purified and dried to obtain polyethylene glycol-grafted carbon dots.

[0029] Step 3: dissolving the polyethylene glycol grafted carbon dots described in step 2 in mixing water according to the mass ratio to obtain a polyethylene glycol grafted carbon dots solution.

[0030] Step 4: Mix the polyethylene glycol grafted carbon dot solution described in step 3 with silicate cement in a certain mass ratio, and stir for 5 minutes to obtain a cement-based material with high mechanical properties and chlorine-fixing properties.

[0031] The mass ratio of the polyethylene glycol grafted carbon dots, mixing water and silicate cement is 0.1:0.5:1.

[0032] Example 2

[0033] The difference from Example 1 is that the molecular weight of the polyethylene glycol used is 600.

[0034] Example 3

[0035] The difference from Example 1 is that the molecular weight of the polyethylene glycol used is 1000.

[0036] Example 4

[0037] The difference from Example 1 is that the molecular weight of the polyethylene glycol used is 1500.

[0038] Comparative Example 1

[0039] The difference from Examples 1, 2, 3 and 4 is that no polyethylene glycol grafted carbon dots are added, and the cement-based material is obtained by directly mixing silicate cement with mixing water.

[0040] Comparative Example 2

[0041] The difference from Examples 1, 2, 3 and 4 is that the added carbon dots are obtained by mixing citric acid and ethylenediamine and heating the mixture at 160° C. for 6 h.

[0042] Test example

[0043] After the cement-based materials of Examples 1, 2, 3, 4 and the comparative example were cured for 28 days, the compressive strength of the cement-based materials after curing was determined according to the method specified in GB / T17671-2021 "Test Method for Cement Mortar Strength (ISO Method)". The chloride ion curing performance of the cement-based materials after curing for 28 days was determined according to the method specified in JGJ / T322-2013 "Technical Specification for Chloride Ion Content in Concrete". The test results are shown in Figure 3 and Figure 4 .

[0044] from Figure 3 It can be seen that compared with Comparative Example 1, the compressive strength of the cement-based materials with high mechanical properties and chlorine-fixing properties in Examples 1, 2, 3 and 4 after curing for 28 days increased by 14.2%, 18.4%, 25.1% and 40.3% respectively. Figure 4 It can be seen that the chloride ion curing rates of cement-based materials with high mechanical properties and chlorine-fixing properties in Examples 1, 2, 3 and 4 are increased by 26.7%, 29.4%, 32.3% and 35.4% respectively compared with Comparative Example 1. Compared with Comparative Example 2, the carbon dots in Examples 1, 2, 3 and 4 are grafted with polyethylene glycol, which has a more obvious dispersion effect on the carbon dots and a more obvious improvement in the performance of the cement-based materials.

[0045] Therefore, the cement-based material with high mechanical properties and chlorine-fixing properties provided by the present invention has the characteristics of simple operation and low preparation cost, and can significantly improve the mechanical properties and chloride ion curing properties of the cement-based material.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A cement-based material with high mechanical properties and chlorine-fixing properties and a preparation method thereof, characterized in that: It consists of three parts: polyethylene glycol grafted carbon dots, mixing water, and silicate cement. The specific preparation steps are as follows: Step 1: Using polyethylene glycol, citric acid and ethylenediamine as raw materials, mixing the raw materials with water according to a mass ratio to obtain a solid-liquid mixture; Step 2: using a hydrothermal method, heating the solid-liquid mixture described in step 1 at 140-200° C. for 4-10 hours to obtain an initial product, and purifying and drying the initial product to obtain polyethylene glycol-grafted carbon dots; Step 3: dissolving the polyethylene glycol grafted carbon dots described in step 2 in mixing water according to the mass ratio to obtain a polyethylene glycol grafted carbon dots solution; Step 4: mixing the polyethylene glycol grafted carbon dot solution described in step 3 with silicate cement according to a mass ratio, and stirring to obtain a cement-based material with high mechanical properties and chlorine-fixing properties; The mass ratio of the polyethylene glycol grafted carbon dots, mixing water and silicate cement is (0.01-0.1):(0.3-0.5):

1.

2. The cement-based material with high mechanical properties and chlorine-fixing properties and the preparation method thereof according to claim 1, characterized in that: In step 1, the mass ratio of polyethylene glycol, citric acid and ethylenediamine is 1:2-5:5-10.

3. The cement-based material with high mechanical properties and chlorine-fixing properties and the preparation method thereof according to claim 1, characterized in that: The molecular weight of the polyethylene glycol is 200-2000.

4. The cement-based material with high mechanical properties and chlorine-fixing properties and the preparation method thereof according to claim 1, characterized in that: The purification step described in step 2 includes centrifugation, suction filtration, dialysis and rotary evaporation.

5. The high chloride ion corrosion resistance cement-based material and preparation method thereof according to claim 1, characterized in that: The stirring time in step 3 is 4 to 8 minutes.

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