Long-chain polyamine mediated biomimetic mineralization modified recycled coarse aggregate and preparation method thereof

Abstract

The invention discloses a long-chain polyamine mediated biomimetic mineralization modified recycled coarse aggregate and a preparation method thereof, and the preparation method comprises the following steps: 1, fully dissolving glacial acetic acid in water, adding the recycled coarse aggregate after impurity cleaning, stirring, and standing in a constant-temperature water bath to obtain the pretreated recycled coarse aggregate; 2, phosphoric acid is added, sodium polyacrylate and polyethylene glycol are sequentially added, and vacuum impregnation is performed after mixing; step 3, adding lauryl amine and lecithin into absolute ethyl alcohol, magnetically stirring and standing at normal temperature, filtering out the recycled coarse aggregate, soaking the recycled coarse aggregate into the solution after standing, stirring at normal temperature, adding tetraethoxysilane, stirring, and carrying out vacuum impregnation on the stirred turbid liquid to form a silicon-calcium mineralized polymer; and step 4, filtering out the recycled coarse aggregate, washing off surface impurities, and drying. According to the method, the reaction process for generating mineralized crystals can be accurately controlled, the reaction activity is improved, and the recycled coarse aggregate is effectively reinforced under the condition of low TEOS concentration.

Description

Technical Field

[0001] The invention relates to coarse aggregate and a preparation method thereof, in particular to a long-chain polyamine-mediated bionic mineralization-modified recycled coarse aggregate and a preparation method thereof. Background Art

[0002] In recent years, due to the rapid development of the construction industry, the demand for natural aggregates has also increased. In order to ease the pressure on resources, recycled aggregates have gradually become an important alternative material. However, some of the old mortars made of recycled aggregates are loose and fragile, with defects such as many pores, high water absorption, and poor mechanical properties, which greatly restricts their application. Silicon reagent strengthening treatment of recycled aggregates can use nano-silica polymers to fill the pores and cracks on the surface of the mortar, strengthen the surface pore structure of the old mortar of recycled aggregates, so as to achieve the purpose of improving the performance of recycled aggregates, which is conducive to the further promotion and application of recycled aggregates and the green disposal of construction solid waste, and has been widely used in the field of recycled aggregate strengthening.

[0003] Biomineralization is the process of inorganic minerals formed by organisms under the mediation of biomacromolecules. This process can form a more sophisticated structure under mild conditions and show excellent performance. Therefore, by simulating the biomineralization process, long-chain polyamines mediate the mineralization of silica with calcium phosphate as the crystal nucleus under the synergistic effect of lecithin, and high-strength silicon-calcium polymers with controllable generation position, reaction process, and nano-morphology can be formed to reinforce the pore structure and surface of recycled aggregate mortar, effectively improving the performance of recycled aggregate.

[0004] The existing recycled aggregate silicon reagent modification method still has the following problems:

[0005] Through chemical synthesis, the silicon-containing reagent and the Ca(OH) in the old mortar on the surface of the recycled aggregate 2 The reaction generates nano-silica, whose fine structure is difficult to effectively control, which can easily cause uneven coating of nano-silica polymer on the surface of the old mortar, forming ineffective accumulation, or agglomeration effect to prematurely close the surface pores of the old mortar, resulting in poor internal strengthening of the mortar and other problems, seriously affecting the modification effect. At the same time, the reaction conditions are relatively harsh, often needing to be carried out under high temperature and high pressure, and the reaction requires the introduction of chemical reagents such as strong acids and strong bases, resulting in the production of toxic byproducts, causing serious environmental pollution.

[0006] Therefore, in order to solve the above technical problems, it is necessary to study a modification method that is efficient, low-toxic, has mild reaction conditions, and can control the generation location, reaction process and nanomorphology of strength substances to improve the defects of traditional silicon reagent modified recycled aggregates and further improve the performance of recycled aggregates and modification efficiency. Summary of the invention

[0007] Purpose of the invention: In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a method for preparing a long-chain polyamine-mediated biomimetic mineralization-modified recycled coarse aggregate with high activity and mild reaction conditions. Another purpose of the present invention is to provide a long-chain polyamine-mediated biomimetic mineralization-modified recycled coarse aggregate with controllable nano-morphology.

[0008] Technical solution: The method for preparing the biomimetic mineralization modified recycled coarse aggregate mediated by long-chain polyamines of the present invention comprises the following steps:

[0009] Step 1, fully dissolving glacial acetic acid in water, adding the recycled coarse aggregate after cleaning the impurities, mixing, and then standing in a constant temperature water bath to obtain pretreated recycled coarse aggregate;

[0010] Step 2, adding phosphoric acid to the product obtained in step 1, and then sequentially adding sodium polyacrylate and polyethylene glycol, mixing and vacuum impregnating, so as to introduce calcium phosphate mineralization nuclei on the surface and pores of the recycled coarse aggregate old mortar;

[0011] Step 3, adding dodecylamine and lecithin to anhydrous ethanol, stirring under magnetic force and standing at room temperature, filtering out the recycled coarse aggregate obtained in step 2, immersing the recycled coarse aggregate in the standing solution and stirring at room temperature, adding ethyl orthosilicate and stirring, vacuum impregnating the stirred suspension to form a silicon-calcium mineralized polymer coating on the surface of the recycled coarse aggregate old mortar;

[0012] Step 4: filter out the recycled coarse aggregate in the product obtained in step 3, wash off the surface impurities, and dry to obtain the long-chain polyamine-mediated bionic mineralized modified recycled coarse aggregate.

[0013] Furthermore, the mass ratio of recycled coarse aggregate, water, tetraethyl orthosilicate, anhydrous ethanol, glacial acetic acid, phosphoric acid, dodecylamine, polyethylene glycol, lecithin, and sodium polyacrylate is 800-1100:300-600:110-160:100-200:60-120:70-100:9-13:7-10:6-10:2-5.

[0014] Furthermore, in step 1, the mixing time is 80 to 160 seconds, and the temperature of the constant temperature water bath is 40 to 80° C. for 2 to 4 hours.

[0015] Furthermore, in step 2, phosphoric acid is added in 2 to 5 times and stirred continuously, and the stirring time is 80 to 160 seconds. The vacuum impregnation time is 90 to 150 minutes, the negative pressure of the vacuum impregnation is 0.05 to 0.15 MPa, and the temperature of the vacuum impregnation is 30° C. to 60° C. The mass fraction of the phosphoric acid solution is 10 to 20 wt%.

[0016] Furthermore, in step 3, the magnetic stirring time is 5 to 10 minutes, the rotor stirring speed is 800 to 1200 r / min, and the standing time is 3 to 5 days. The stirring time at room temperature is 80 to 160 seconds, and the stirring time of adding ethyl orthosilicate is 5 to 10 minutes. The vacuum impregnation time is 6 to 10 hours, the negative pressure is 0.4 to 0.6 MPa, and the temperature is 20°C to 40°C.

[0017] Furthermore, in step 4, the drying temperature is 40-70° C. and the drying time is 36-60 hours.

[0018] The method for preparing the biomimetic mineralized modified recycled coarse aggregate mediated by long-chain polyamine of the present invention obtains the biomimetic mineralized modified recycled coarse aggregate mediated by long-chain polyamine, and the particle size of the recycled coarse aggregate is 9.5mm-26.5mm.

[0019] Preparation principle: Current cell biology and molecular biology research have shown that the mineral cell wall structure of diatoms is an organic-inorganic composite structure. The organic matter in several diatom organisms participates in the mineralization process of its formation. These natural organic molecules have unique physical and chemical characteristics. Among them, organic amines are widely present in diatom cell walls and can induce the precipitation of spherical silica particles, providing basic conditions for the deposition activity of silica under physiological conditions. On the other hand, in diatoms, the entire polymerization process of silica occurs in vesicles called SDVs. This vesicle is composed of a phospholipid bilayer. The lipid membrane is closely attached to the biological silica structure in diatoms and eventually becomes part of the silica cell wall structure. Therefore, long-chain organic amines and phospholipid molecules will have an important impact on the biomineralization process in diatoms. By utilizing the synergistic effect of long-chain organic amines and lecithin molecules to imitate the formation process of mineral cell walls in diatom organisms, the nanomorphology of mineralization products can be effectively controlled to generate long-grained silica polymers. Compared with the spherical silica polymers generated by traditional silicon reagent-modified recycled coarse aggregate, they have certain micropores, allowing the small molecular effective ingredients in the modified reagent to continue to penetrate the deep structure of the recycled coarse aggregate old mortar, filling the pores and cracks therein, thereby making the old mortar more compact as a whole, better improving the strength and density of the recycled coarse aggregate old mortar part, and further improving its macroscopic performance.

[0020] Mollusk shells are usually composed of calcium carbonate surrounded by an organic matrix. Before mineralization, a crystal nucleation site must be provided, and organic matter can construct liposome-mediated mineralization with the crystal nucleus as the center. Therefore, by providing mineralized crystal nuclei, the spatial expansion of the crystal can be effectively limited, and the distribution position of the mineralized crystals can be controlled, so that the distribution of the strength material is more uniform and the pore structure can be more fully regulated. The present invention uses phosphoric acid and acetic acid solutions to vacuum impregnate the recycled coarse aggregate, so that it is combined with the Ca(OH) 2Reaction to generate CaHPO 4 The particles are initially filled with the pores and cracks of the old mortar of the recycled coarse aggregate, and used as mineralized crystal nuclei. Under the action of lecithin surfactant, they are coated with dodecylamine to simulate the liposomes and long-chain polyamines in the cell wall structure of diatoms. Lecithin can be coated on CaHPO through the dipole-dipole interaction between the hydrophilic head groups and the van der Waals interaction between the alkyl tails. 4 Bilayer liposomes are formed on the surface of the microparticles. The dodecylamine molecules form a positively charged hydrophilic head group by combining with hydrogen ions. The molecules themselves also have a hydrophobic alkyl tail, which can also interact with the lecithin molecules. The electrostatic attraction of the lecithin molecules attracts the negatively charged SiO 2 The particles aggregate onto the hydrophilic head groups of lecithin and dodecylamine and assemble into columnar particles, forming a high-strength silicon-calcium mineralized polymer that coats the surface of the recycled aggregate mortar layer and regulates its internal structure, thereby achieving the purpose of further improving the performance of the recycled coarse aggregate.

[0021] Among them, tetraethyl orthosilicate is used as the silicon source, and water and ethanol are used as solvents respectively. Polyethylene glycol is used as a dispersant. After being adsorbed on the surface of solid particles, the steric hindrance effect between the dispersant molecules can be used to prevent the particles from agglomerating, thereby reducing the viscosity of the slurry, producing a steric hindrance effect, and forming a stable dispersion system. Sodium polyacrylate is used as a stabilizer to increase the suspension stability of the slurry system, reduce the sedimentation rate of the particles therein, and make the effective ingredients in the slurry react more fully with the old mortar on the surface of the recycled coarse aggregate. Dodecylamine simulates the long-chain polyamine in the cell wall structure of diatoms as an organic molecular assembly; lecithin simulates the liposome in the cell wall structure of diatoms as a surfactant. Phosphoric acid, glacial acetic acid and Ca(OH) in the recycled coarse aggregate old mortar 2 The reaction produces CaHPO 4 The microparticles serve as mineralization nuclei. Phosphating treatment provides nucleation sites, and long-chain polyamine mediates the formation of silicon-calcium mineralized polymers, thereby controlling the formation location, reaction process and nano-morphology of strength materials to improve the defects of traditional silicon reagent modified recycled aggregates.

[0022] The equations involved in the core reaction are as follows:

[0023] Ca(OH) 2 +2CH 3 COOH=(CH 3 COO 2 Ca + 2H 2 O

[0024] (CH 3 COO 2 Ca+H 3 PO 4 =2CH3 COOH+CaHPO 4

[0025] (C 2 H 5 O) 4 Si+2H 2 O=4C 2 H 5 OH+SiO 2

[0026] SiO 2 =(SiO 2 ) n .

[0027] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0028] 1. By using organic molecular assemblies to induce silica deposition with mineralized crystal nuclei as nucleation points, the reaction process of generating mineralized crystals can be precisely controlled, the reaction activity can be improved, and the effective strengthening of recycled coarse aggregate at low TEOS concentration can be achieved, which is beneficial to resource conservation and cost control in industrial production;

[0029] 2. CaHPO 4 The microparticles, as nucleation points, can control the growth position of mineralized crystals, so that the strength material can evenly cover the surface of the recycled aggregate old mortar and fully fill its internal pores; the morphology of the silicon-calcium polymer is controlled by the organic molecular assembly, so that the silica polymer structure formed by the interweaving of columnar particles has certain micropores, allowing the effective ingredients in the modification agent to continue to penetrate the deep structure of the recycled coarse aggregate old mortar, filling the pores and cracks therein, thereby making the old mortar more compact overall. Compared with the traditional silicon reagent modification method, it can better improve the macroscopic performance of the recycled coarse aggregate;

[0030] 3. The method of modifying recycled aggregate silicon reagent can be realized under low toxicity and mild reaction conditions, which is beneficial to environmental protection and energy conservation and emission reduction;

[0031] 4. By using vacuum impregnation to allow the modification reagent to fully penetrate the pores and cracks of the surface mortar of the recycled coarse aggregate, and by rationally blending various auxiliary materials such as dispersants and stabilizers, the modification effect, rate and reaction stability are further improved, which is helpful to improve the modification efficiency and its practical application in industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a scanning electron microscope image of the surface of the old mortar of the recycled coarse aggregate before strengthening of the present invention;

[0033] Figure 2 It is a scanning electron microscope image of the surface of the old mortar of the recycled coarse aggregate after strengthening according to the present invention. DETAILED DESCRIPTION

[0034] The experimental methods described in the examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified. In the following examples, the purity of tetraethyl orthosilicate is analytically pure. The average molecular weight of sodium polyacrylate is 4 million to 5 million, and the average molecular weight of polyethylene glycol is 200. The long-chain polyamine refers to dodecylamine, with a molecular formula of CH 3 (CH 2 ) 11 NH 2 .

[0035] Example 1

[0036] A method for preparing a biomimetic mineralized modified recycled coarse aggregate mediated by a long-chain polyamine comprises the following steps:

[0037] (1) Pretreatment of recycled coarse aggregate: Wash away 950 parts of impurities such as mud and sand on the surface of recycled coarse aggregate with an average particle size of 16 mm, fully dissolve 90 parts of glacial acetic acid in 450 parts of water, add the recycled coarse aggregate after the impurities are washed, stir for 120 seconds, and let it stand in a constant temperature water bath at 60°C for 3 hours to obtain the pretreated recycled coarse aggregate.

[0038] (2) Phosphate treatment of recycled coarse aggregate surface: Keep the temperature of the constant temperature water bath at 60°C, slowly add 85 parts of phosphoric acid to the result of step (1) in three portions and stir continuously, then add 4 parts of sodium polyacrylate and 9 parts of polyethylene glycol in sequence, and stir for 120 seconds. Move the mixed suspension and the recycled coarse aggregate soaked therein to a vacuum high-pressure impregnation tank for vacuum impregnation for 120 minutes, with a negative pressure of 0.1 MPa and a temperature of 45°C, to introduce phosphate mineralization nuclei on the surface and pores of the old mortar of the recycled coarse aggregate.

[0039] (3) Long-chain polyamine-mediated modification: 11 parts of dodecylamine and 8 parts of lecithin were added to 150 parts of anhydrous ethanol, and magnetically stirred for 7 minutes at room temperature, with a rotor stirring speed of 1000 r / min, and then left to stand at room temperature for 4 days. The recycled coarse aggregate after negative pressure impregnation was filtered out, immersed in the solution after standing and stirred at room temperature for 120 seconds, and 135 parts of ethyl orthosilicate were added and stirred for 7 minutes. The mixed suspension and the recycled coarse aggregate soaked therein were moved to a vacuum high-pressure impregnation tank for vacuum impregnation for 8 hours, with a negative pressure of 0.5 MPa and a temperature of 30°C, to form a silicon-calcium mineralized polymer to regulate the recycled coarse aggregate old mortar.

[0040] (4) Cleaning and drying: Filter out the recycled coarse aggregate obtained in step (3), wash off the surface impurities, and dry it in a drying oven for 48 hours at a temperature of 55° C. to obtain the long-chain polyamine-mediated bionic mineralized modified recycled coarse aggregate.

[0041] In order to determine the specific composition of the surface strength material of the recycled coarse aggregate after strengthening, the present invention uses an X-ray fluorescence spectrometer (XRF) to test the main element components and their contents of the recycled coarse aggregate before and after strengthening, and the results are shown in Table 1.

[0042] Table 1 Comparison of the content of main elements in recycled coarse aggregate before and after modification

[0043] Aggregate Type Ca / % Si / % Fe / % Al / ％ K / ％ P / ％ After modification 41.63 14.26 4.65 1.97 1.02 0.63 Before modification 41.34 11.87 6.2 2.29 1.37 0

[0044] As shown in Table 1, after the long-chain polyamine-mediated bionic modification, 0.63% phosphorus was added to the main element components of the recycled coarse aggregate, indicating that a large number of CaHPO2+ / -2HPO4 ... 4 Particle generation. The silicon content increased by 20.13%, indicating that after the long-chain polyamine-mediated modification, a large amount of high-strength silicon-calcium modified polymers were formed to coat the surface of the recycled aggregate old mortar and regulate its internal structure. The calcium content remained basically unchanged, and the contents of iron, aluminum, and potassium decreased, indicating that no excess substances were generated on the surface of the recycled coarse aggregate, which means that the modification process and the strength substances produced are generally controllable. According to the relative molecular mass, the effective component CaHPO in the silicon-calcium modified polymer, a strength substance generated by the long-chain polyamine-mediated bionic modification, is 4 With SiO 2 The molar ratio is 1:8.54.

[0045] In order to determine the microscopic morphology changes of the reinforced product and the recycled coarse aggregate old mortar surface after reinforcement, the present invention uses S-4800Ⅱ field emission scanning electron microscope to observe the surface of the recycled coarse aggregate old mortar before and after reinforcement. The obtained images are as follows: Figure 1 , Figure 2 Shown, magnification is 500x.

[0046] from Figure 1 It can be seen that the surface of the old mortar with recycled coarse aggregate before modification is rough, with many pores and cracks and uneven texture. Figure 2 It can be seen that after long-chain polyamine-mediated bionic modification, a coating layer of silicon-calcium modified polymer is formed on the surface of the recycled coarse aggregate old mortar, which greatly improves its surface flatness, effectively fills the pores and cracks, and greatly improves the texture uniformity. This shows that the long-chain polyamine-mediated bionic modification method proposed in the present invention can effectively improve the performance of recycled coarse aggregate by generating silicon-calcium modified polymer to fill the pores on the surface of recycled coarse aggregate old mortar and improve its surface properties. Referring to the "Highway Engineering Aggregate Test Code" (JTG E42-2005), the apparent density of the recycled coarse aggregate before strengthening (referred to as Comparative Example 1) is 2453kg / m 3The water absorption rate was 6.67% and the crushing value was 28.35%. The apparent density of the recycled coarse aggregate after strengthening increased by 6.81%, the water absorption rate decreased by 42.28% and the crushing value decreased by 33.47% compared with before strengthening.

[0047] Example 2

[0048] A method for preparing a biomimetic mineralized modified recycled coarse aggregate mediated by a long-chain polyamine comprises the following steps:

[0049] (1) Pretreatment of recycled coarse aggregate: Wash away 800 parts of impurities such as mud and sand on the surface of recycled coarse aggregate with an average particle size of 9.5 mm, fully dissolve 60 parts of glacial acetic acid in 300 parts of water, add the recycled coarse aggregate after the impurities are washed, stir for 80 seconds, and let it stand in a constant temperature water bath at 40°C for 4 hours to obtain the pretreated recycled coarse aggregate.

[0050] (2) Phosphate treatment of recycled coarse aggregate surface: Keep the temperature of the constant temperature water bath at 40°C, slowly add 70 parts of phosphoric acid to the result of step (1) twice and stir continuously, then add 2 parts of sodium polyacrylate and 7 parts of polyethylene glycol in sequence, and stir for 80 seconds. Move the mixed suspension and the recycled coarse aggregate soaked therein to a vacuum high-pressure impregnation tank for vacuum impregnation for 90 minutes, with a negative pressure of 0.05 MPa and a temperature of 30°C, to introduce phosphate mineralization nuclei on the surface and pores of the old mortar of the recycled coarse aggregate.

[0051] (3) Long-chain polyamine-mediated modification: 9 parts of dodecylamine and 6 parts of lecithin were added to 100 parts of anhydrous ethanol, and magnetically stirred for 5 minutes at room temperature, with a rotor stirring speed of 800 r / min, and then allowed to stand at room temperature for 3 days. The recycled coarse aggregate after negative pressure impregnation was filtered out, immersed in the solution after standing and stirred at room temperature for 80 seconds, and 110 parts of ethyl orthosilicate were added and stirred for 5 minutes. The mixed suspension and the recycled coarse aggregate soaked therein were moved to a vacuum high-pressure impregnation tank for vacuum impregnation for 6 hours, with a negative pressure of 0.4 MPa and a temperature of 20°C, to form a silicon-calcium mineralized polymer to regulate the recycled coarse aggregate old mortar.

[0052] (4) Cleaning and drying: Filter out the recycled coarse aggregate obtained in step (3), wash off the surface impurities, and dry it in a drying oven for 36 hours at a temperature of 40° C. to obtain the long-chain polyamine-mediated bionic mineralized modified recycled coarse aggregate.

[0053] According to the "Highway Engineering Aggregate Test Code" (JTG E42-2005), the apparent density of recycled coarse aggregate before strengthening is 2453kg / m 3, water absorption rate is 6.67%, crushing value is 28.35%. The apparent density of the recycled aggregate after strengthening increased by 5.42%, the water absorption rate decreased by 36.58%, and the crushing value decreased by 28.82% compared with before strengthening.

[0054] Example 3

[0055] A method for preparing a biomimetic mineralized modified recycled coarse aggregate mediated by a long-chain polyamine comprises the following steps:

[0056] (1) Pretreatment of recycled coarse aggregate: Wash away impurities such as mud on the surface of 1100 parts of recycled coarse aggregate with an average particle size of 26.5 mm, fully dissolve 120 parts of glacial acetic acid in 600 parts of water, add the recycled coarse aggregate after the impurities are washed away, stir for 160 seconds, and let it stand in a constant temperature water bath at 80°C for 4 hours to obtain the pretreated recycled coarse aggregate.

[0057] (2) Phosphate treatment of recycled coarse aggregate surface: Keep the temperature of the constant temperature water bath at 80°C, slowly add 100 parts of phosphoric acid to the result of step (1) in 5 times and stir continuously, then add 5 parts of sodium polyacrylate and 10 parts of polyethylene glycol in sequence, and stir for 160 seconds. Move the mixed suspension and the recycled coarse aggregate soaked therein to a vacuum high-pressure impregnation tank for vacuum impregnation for 150 minutes, with a negative pressure of 0.15 MPa and a temperature of 60°C, to introduce phosphate mineralization nuclei on the surface and pores of the old mortar of the recycled coarse aggregate.

[0058] (3) Long-chain polyamine-mediated modification: 13 parts of dodecylamine and 10 parts of lecithin were added to 200 parts of anhydrous ethanol, and magnetically stirred for 10 minutes at room temperature, with a rotor stirring speed of 1200 r / min, and then left to stand at room temperature for 5 days. The recycled coarse aggregate after negative pressure impregnation was filtered out, immersed in the solution after standing and stirred at room temperature for 160 seconds, and 160 parts of ethyl orthosilicate were added and stirred for 10 minutes. The mixed suspension and the recycled coarse aggregate soaked therein were moved to a vacuum high-pressure impregnation tank for vacuum impregnation for 10 hours, with a negative pressure of 0.6 MPa and a temperature of 40°C, to form a silicon-calcium mineralized polymer to regulate the recycled coarse aggregate old mortar.

[0059] (4) Cleaning and drying: Filter out the recycled coarse aggregate obtained in step (3), wash off the surface impurities, and dry it in a drying oven for 60 hours at a temperature of 70° C. to obtain the long-chain polyamine-mediated bionic mineralized modified recycled coarse aggregate.

[0060] According to the "Highway Engineering Aggregate Test Code" (JTG E42-2005), the apparent density of recycled coarse aggregate before strengthening is 2453kg / m 3, water absorption rate is 6.67%, crushing value is 28.35%. The apparent density of the reinforced recycled aggregate is 8.97% higher than that before reinforcement. The water absorption rate of the reinforced recycled aggregate is tested, which is 37.48% lower than that before reinforcement. The crushing value of the reinforced recycled aggregate is tested, which is 31.32% lower than that before reinforcement.

[0061] Example 4

[0062] A method for preparing a biomimetic mineralized modified recycled coarse aggregate mediated by a long-chain polyamine comprises the following steps:

[0063] (1) Pretreatment of recycled coarse aggregate: Wash away 850 parts of impurities such as mud and sand on the surface of recycled coarse aggregate with an average particle size of 13.2 mm, fully dissolve 80 parts of glacial acetic acid in 400 parts of water, add the recycled coarse aggregate after the impurities are washed, stir for 100 seconds, and let it stand in a constant temperature water bath at 50°C for 2 hours to obtain the pretreated recycled coarse aggregate.

[0064] (2) Phosphate treatment of recycled coarse aggregate surface: Keep the temperature of the constant temperature water bath at 50°C, slowly add 80 parts of phosphoric acid to the result of step (1) in 4 times and stir continuously, then add 3 parts of sodium polyacrylate and 8 parts of polyethylene glycol in sequence, and stir for 100 seconds. Move the mixed suspension and the recycled coarse aggregate soaked therein to a vacuum high-pressure impregnation tank for vacuum impregnation for 100 minutes, with a negative pressure of 0.08 MPa and a temperature of 40°C, to introduce phosphate mineralization nuclei on the surface and pores of the old mortar of the recycled coarse aggregate.

[0065] (3) Long-chain polyamine-mediated modification: 10 parts of dodecylamine and 7 parts of lecithin were added to 120 parts of anhydrous ethanol, and magnetically stirred for 6 minutes at room temperature, with a rotor stirring speed of 900 r / min, and then left to stand at room temperature for 4 days. The recycled coarse aggregate after negative pressure impregnation was filtered out, immersed in the solution after standing and stirred at room temperature for 90 seconds, and 150 parts of ethyl orthosilicate were added and stirred for 6 minutes. The mixed suspension and the recycled coarse aggregate soaked therein were moved to a vacuum high-pressure impregnation tank for vacuum impregnation for 7 hours, with a negative pressure of 0.5 MPa and a temperature of 25°C, to form a silicon-calcium mineralized polymer to regulate the recycled coarse aggregate old mortar.

[0066] (4) Cleaning and drying: Filter out the recycled coarse aggregate obtained in step (3), wash off the surface impurities, and dry it in a drying oven for 50 hours at a temperature of 60° C. to obtain the long-chain polyamine-mediated bionic mineralized modified recycled coarse aggregate.

[0067] According to the "Highway Engineering Aggregate Test Code" (JTG E42-2005), the apparent density of recycled coarse aggregate before strengthening is 2453kg / m 3, water absorption rate is 6.67%, crushing value is 28.35%. The apparent density of the recycled aggregate after strengthening increased by 5.63%, the water absorption rate decreased by 41.08%, and the crushing value decreased by 31.99% compared with before strengthening.

[0068] Example 5

[0069] A method for preparing a biomimetic mineralized modified recycled coarse aggregate mediated by a long-chain polyamine comprises the following steps:

[0070] (1) Pretreatment of recycled coarse aggregate: Wash away impurities such as mud and sand on the surface of 1000 parts of recycled coarse aggregate with an average particle size of 19 mm, fully dissolve 100 parts of glacial acetic acid in 500 parts of water, add the recycled coarse aggregate after the impurities are washed, stir for 140 seconds, and let it stand in a constant temperature water bath at 70°C for 2 hours to obtain the pretreated recycled coarse aggregate.

[0071] (2) Phosphate treatment of recycled coarse aggregate surface: Keep the temperature of the constant temperature water bath at 70°C, slowly add 70 parts of phosphoric acid to the result of step (1) twice and stir continuously, then add 4 parts of sodium polyacrylate and 8 parts of polyethylene glycol in sequence, and stir for 140 seconds. Move the mixed suspension and the recycled coarse aggregate soaked therein to a vacuum high-pressure impregnation tank for vacuum impregnation for 140 minutes, with a negative pressure of 0.12 MPa and a temperature of 50°C, to introduce phosphate mineralization nuclei on the surface and pores of the old mortar of the recycled coarse aggregate.

[0072] (3) Long-chain polyamine-mediated modification: 12 parts of dodecylamine and 9 parts of lecithin were added to 180 parts of anhydrous ethanol, and magnetically stirred for 9 minutes at room temperature, with a rotor stirring speed of 1100 r / min, and then left to stand at room temperature for 4 days. The recycled coarse aggregate after negative pressure impregnation was filtered out, immersed in the solution after standing and stirred at room temperature for 140 seconds, and 120 parts of ethyl orthosilicate were added and stirred for 8 minutes. The mixed suspension and the recycled coarse aggregate soaked therein were moved to a vacuum high-pressure impregnation tank for vacuum impregnation for 9 hours, with a negative pressure of 0.5 MPa and a temperature of 35°C, to form a silicon-calcium mineralized polymer to regulate the recycled coarse aggregate old mortar.

[0073] (4) Cleaning and drying: Filter out the recycled coarse aggregate obtained in step (3), wash off the surface impurities, and dry it in a drying oven for 40 hours at a temperature of 65° C. to obtain the long-chain polyamine-mediated bionic mineralized modified recycled coarse aggregate.

[0074] According to the "Highway Engineering Aggregate Test Code" (JTG E42-2005), the apparent density of recycled coarse aggregate before strengthening is 2453kg / m 3, water absorption rate is 6.67%, crushing value is 28.35%. The apparent density of the recycled aggregate after strengthening increased by 7.42%, the water absorption rate decreased by 45.13%, and the crushing value decreased by 33.72% compared with before strengthening.

[0075] Comparative Example 1

[0076] The apparent density of the unreinforced recycled coarse aggregate in Example 1 is 2453 kg / m 3 , the water absorption is 6.67% and the crushing value is 28.35%.

[0077] Comparative Example 2

[0078] A method for modifying recycled coarse aggregate using a conventional silicon reagent comprises the following steps:

[0079] (1) 135 parts of tetraethyl orthosilicate, 150 parts of anhydrous ethanol, 450 parts of water, and 0.7 parts of hydrochloric acid were uniformly mixed to obtain a tetraethyl orthosilicate (TEOS) modifier.

[0080] (2) 950 parts of recycled coarse aggregate with a particle size of 16 mm were washed to remove impurities such as sand on the surface, added to the above-mentioned TEOS modifier and mixed for 120 seconds, and then placed in a constant temperature water bath at 30°C for 8 hours.

[0081] (3) The soaked recycled coarse aggregate is filtered out to remove surface impurities, and then placed in a drying oven for drying at a temperature of 55° C. for 48 hours to obtain the conventional silicon reagent modified recycled coarse aggregate.

[0082] The apparent density of the reinforced recycled aggregate obtained in this embodiment was tested with reference to the "Highway Engineering Aggregate Test Code" (JTG E42-2005), which was 1.51% higher than that before reinforcement. The water absorption rate of the reinforced recycled aggregate was tested, which was 39.73% lower than that before reinforcement. The crushing value of the reinforced recycled aggregate was tested, which was 18.73% lower than that before reinforcement.

[0083] Comparative Example 3

[0084] The raw materials and other steps of this comparative example are the same as those of Example 1, with the only difference being that in step (1), impurities such as mud and sand on the surface of the recycled coarse aggregate are washed away, glacial acetic acid is fully dissolved in water, the washed recycled coarse aggregate is added and stirred for 70 seconds, and the mixture is allowed to stand in a constant temperature water bath at 35°C for 2 hours.

[0085] According to the "Highway Engineering Aggregate Test Code" (JTG E42-2005), the apparent density of the reinforced recycled aggregate obtained in this comparative example increased by 0.9% compared with that before reinforcement, the water absorption rate decreased by 11.24% compared with that before reinforcement, and the crushing value decreased by 7.65% compared with that before reinforcement.

[0086] Comparative Example 4

[0087] The raw materials and other steps of this comparative example are the same as those of Example 2, with the only difference being that in step (1), impurities such as mud and sand on the surface of the recycled coarse aggregate are washed away, glacial acetic acid is fully dissolved in water, the washed recycled coarse aggregate is added and stirred for 170 seconds, and the mixture is allowed to stand in a constant temperature water bath at 90° C. for 4 hours.

[0088] The apparent density of the reinforced recycled aggregate obtained in this comparative example was tested with reference to the "Test Code for Highway Engineering Aggregates" (JTG E42-2005), which was 6.85% higher than that before reinforcement, the water absorption rate was 37.18% lower than that before reinforcement, and the crushing value was 29.28% lower than that before reinforcement.

[0089] Comparative Example 5

[0090] The raw materials and the remaining steps of this comparative example are the same as those of Example 3, with the only difference being that: in step (2), the mixed suspension and the recycled coarse aggregate soaked therein are moved to a vacuum high-pressure impregnation tank for vacuum impregnation for 160 min, with a negative pressure of 0.2 MPa and a temperature of 70°C; in step (3), dodecylamine and lecithin are added to anhydrous ethanol, and magnetic stirring is carried out for 3 min at room temperature, with a rotor stirring speed of 700 r / min; and the recycled coarse aggregate is moved to a vacuum high-pressure impregnation tank for vacuum impregnation for 12 h, with a negative pressure of 0.7 MPa and a temperature of 50°C.

[0091] The apparent density of the reinforced recycled aggregate obtained in this comparative example was tested with reference to the "Test Code for Highway Engineering Aggregates" (JTG E42-2005). It was increased by 2.61% compared with before reinforcement, the water absorption rate was reduced by 28.64% compared with before reinforcement, and the crushing value was reduced by 18.31% compared with before reinforcement.

[0092] Comparative Example 6

[0093] The steps of this comparative example are the same as those of Example 2, except that the raw materials are different. In terms of weight, the raw materials in Comparative Example 6 include: 800 parts of recycled coarse aggregate, 700 parts of water, 170 parts of tetraethyl orthosilicate, 220 parts of anhydrous ethanol, 50 parts of glacial acetic acid, 60 parts of phosphoric acid, 8 parts of dodecylamine, 6 parts of polyethylene glycol, 5 parts of lecithin, and 1 part of sodium polyacrylate.

[0094] The apparent density of the reinforced recycled aggregate obtained in this comparative example was tested with reference to the "Test Code for Highway Engineering Aggregates" (JTG E42-2005), which was 0.57% higher than that before reinforcement, the water absorption rate was 20.24% lower than that before reinforcement, and the crushing value was 5.22% lower than that before reinforcement.

[0095] Comparative Example 7

[0096] The steps of this comparative example are the same as those of Example 3, except that the raw materials are different. In terms of weight, the raw materials in Comparative Example 7 include: 1100 parts of recycled coarse aggregate, 250 parts of water, 100 parts of tetraethyl orthosilicate, 90 parts of anhydrous ethanol, 130 parts of glacial acetic acid, 110 parts of phosphoric acid, 14 parts of dodecylamine, 12 parts of polyethylene glycol, 12 parts of lecithin, and 7 parts of sodium polyacrylate.

[0097] The apparent density of the reinforced recycled aggregate obtained in this comparative example was tested with reference to the "Test Code for Highway Engineering Aggregates" (JTG E42-2005), which was 1.35% higher than that before reinforcement, the water absorption rate was 26.69% lower than that before reinforcement, and the crushing value was 9.03% lower than that before reinforcement.

[0098] The apparent density, water absorption rate and crushing value of the recycled coarse aggregate samples of Examples 1 to 3 and Comparative Examples 1 to 7 before and after modification are shown in Table 2.

[0099] Table 2 Comparison of recycled coarse aggregate properties before and after strengthening

[0100]

[0101] It can be seen from Examples 1-3 and Comparative Example 1 in Table 2 that the apparent density of the reinforced recycled aggregate prepared by the present invention is improved compared with that before reinforcement, and the crushing value is significantly reduced. This is because the glacial acetic acid and the Ca(OH) 2 The calcium acetate generated by the reaction is evenly distributed in the surface, pores and cracks of the recycled aggregate, and then reacts with phosphoric acid, sodium polyacrylate and polyethylene glycol to generate micro-apatite to fill the pores and micro-cracks of the old mortar on the surface as a crystal nucleus. Under the action of lecithin surfactant, dodecylamine is used for coating to simulate the liposomes and long-chain polyamines in the cell wall structure of diatoms. Lecithin is coated on the surface of micro-apatite to form bimolecular membrane liposomes through the dipole-dipole interaction between the hydrophilic head groups and the van der Waals force between the alkyl tails. The dodecylamine molecule forms a positively charged hydrophilic head group by combining with hydrogen ions. The molecule itself also has a hydrophobic alkyl tail, which can also interact with the lecithin molecule. Under the electrostatic attraction of lecithin molecules, negatively charged silica particles are attracted to gather on the hydrophilic head groups of lecithin and dodecylamine and deposited and assembled into columnar particles, forming a high-strength silicon-calcium modified polymer coating on the surface of the recycled aggregate mortar layer and regulating its internal structure, thereby achieving the purpose of further improving the performance of the recycled coarse aggregate.

[0102] It can be seen from Example 1 and Comparative Example 2 in Table 2 that compared with the method of modifying recycled aggregate with traditional silicon reagents, the recycled aggregate of the present invention has a significant effect on improving the regeneration apparent density, and the crushing value and water absorption rate are significantly reduced. This is because the traditional silicon reagent modification method is often difficult to control the fine structure of nano-silicon dioxide generated on the surface of the recycled aggregate, which can easily cause uneven coating of nano-silicon dioxide polymers on the surface of the old mortar, forming invalid accumulation, or producing agglomeration effects and prematurely closing the pores on the surface of the old mortar, resulting in poor internal strengthening of the mortar and other problems, which seriously affect the modification effect. The present invention is based on the principle of bionics, and the formation of silicon-calcium polymers with controllable generation position, reaction process, and nano-morphology is mediated by organic molecular assemblies, which can effectively improve the above-mentioned defects of traditional silicon reagent modified recycled aggregates and further improve the performance of recycled aggregates.

[0103] It can be seen from Example 1 and Comparative Example 3 in Table 2 that in the pretreatment step of recycled coarse aggregate of the present invention, if the mixing time of glacial acetic acid and the washed recycled coarse aggregate is less than the range provided by the present invention, or the temperature of the constant temperature water bath in the pretreatment step is less than the range provided by the present invention, the strengthening effect is poor. This is because the reaction rate is slow due to the short mixing time and low temperature, and the glacial acetic acid solution is difficult to fully react with the calcium hydroxide in the recycled aggregate old mortar, and the modifier fails to penetrate the internal pore structure of the recycled aggregate old mortar, affecting the modification effect of the subsequent steps.

[0104] As shown in Example 2 and Comparative Example 4 in Table 2, in the pretreatment step of the recycled coarse aggregate of the present invention, if the mixing time of glacial acetic acid and the washed recycled coarse aggregate exceeds the range provided by the present invention, or the temperature of the constant temperature water bath in the pretreatment step exceeds the range provided by the present invention, the strengthening effect is not significantly improved. This is because within the temperature and mixing time range provided by the present invention, acetic acid has fully reacted with the calcium hydroxide in the old mortar of the recycled aggregate, and even if the temperature is increased and the mixing time is increased, it is difficult to further improve the modification effect. In addition, the excessively high temperature also causes the reaction of the glacial acetic acid solution with the aggregate surface to be too violent, causing certain corrosion or microscopic damage to the aggregate surface, and the long mixing time will also cause certain mechanical damage to the recycled aggregate surface.

[0105] It can be seen from Examples 1, 3 and Comparative Example 5 in Table 2 that in the long-chain polyamine-mediated modification treatment step of the present invention, the stirring time and rotor speed are lower than the range provided by the present invention. Even if the vacuum high-pressure impregnation time, pressure and temperature are increased, the strengthening effect is still limited. This is because the addition of dodecylamine and lecithin is not sufficiently stirred, so that it fails to fully cover the surface of the recycled aggregate and penetrate the pore structure of the old mortar. Even under the action of the lecithin surfactant, dodecylamine cannot remove the CaHPO in the pores and cracks of the recycled coarse aggregate mortar. 4The particles form a uniform coating layer, resulting in poor mediation effect on the deposition and assembly of nano-silica. The surfactant effect of lecithin molecules is also difficult to fully exert, and the purpose of making silicon-calcium polymer fully fill the pores and cracks of the mortar on the surface of the recycled coarse aggregate cannot be achieved, resulting in poor modification effect of the recycled aggregate.

[0106] In general, when the raw materials remain unchanged, within the range given in the present invention, the temperature of the constant temperature water bath in the pretreatment needs to be lowered, and the stirring time in the pretreatment can be appropriately reduced; the vacuum high-pressure impregnation time, pressure and temperature can also be reduced by appropriately increasing the stirring time and rotor speed in the long-chain polyamine-mediated modification treatment step.

[0107] It can be seen from Examples 1, 2, 3 and Comparative Examples 6 and 7 in Table 2 that if the raw materials used in the long-chain polyamine-mediated biomimetic modification of recycled coarse aggregate by the present invention are not within the scope provided by the present invention, the apparent density of the modified recycled coarse aggregate obtained will decrease and the crushing value will increase. This is because the change in the proportion of each raw material will cause the proportion of one or more components in the recycled coarse aggregate modified by long-chain polyamine-mediated biomimetic modification to be too small, resulting in insufficient number of crystal nuclei or uneven coating film formed. In severe cases, it will cause poor improvement in various performance indicators of recycled aggregate. For example, in Comparative Example 6, the proportion of glacial acetic acid in the raw material is seriously low, which makes it difficult to form a sufficient amount of CaHPO in the pores, cracks and surfaces inside the recycled aggregate. 4 The particles act as crystal nuclei, making it difficult to effectively control the formation position, reaction process and nano-morphology of high-strength silicon-calcium polymer deposition assembly, resulting in poor modified recycled aggregate effect. At the same time, changes in the proportion of each raw material will lead to too little or too much product in the silicification process, thus affecting the performance of the modified recycled aggregate.

[0108] Among the above embodiments, the best embodiment is Embodiment 5.

Claims

1. A method for preparing biomimetic mineralized modified recycled coarse aggregate mediated by long-chain polyamine, characterized in that: The following steps are involved: Step 1, fully dissolving glacial acetic acid in water, adding the recycled coarse aggregate after cleaning the impurities, mixing, and then standing in a constant temperature water bath to obtain pretreated recycled coarse aggregate; Step 2, adding phosphoric acid to the product obtained in step 1, and then sequentially adding sodium polyacrylate and polyethylene glycol, mixing and vacuum impregnating, so as to introduce calcium phosphate mineralization nuclei on the surface and pores of the recycled coarse aggregate old mortar; Step 3, adding dodecylamine and lecithin to anhydrous ethanol, stirring under magnetic force and standing at room temperature, filtering out the recycled coarse aggregate obtained in step 2, immersing the recycled coarse aggregate in the standing solution and stirring at room temperature, adding ethyl orthosilicate and stirring, vacuum impregnating the stirred suspension to form a silicon-calcium mineralized polymer coating on the surface of the recycled coarse aggregate old mortar; Step 4: filter out the recycled coarse aggregate in the product obtained in step 3, wash off the surface impurities, and dry to obtain the long-chain polyamine-mediated bionic mineralized modified recycled coarse aggregate.

2. The method for preparing a long-chain polyamine-mediated biomimetic mineralization-modified recycled coarse aggregate according to claim 1, characterized in that: The mass ratio of the recycled coarse aggregate, water, tetraethyl orthosilicate, anhydrous ethanol, glacial acetic acid, phosphoric acid, dodecylamine, polyethylene glycol, lecithin and sodium polyacrylate is 800-1100:300-600:110-160:100-200:60-120:70-100:9-13:7-10:6-10:2-5.

3. The method for preparing a long-chain polyamine-mediated biomimetic mineralization-modified recycled coarse aggregate according to claim 1, characterized in that: In the step 1, the mixing time is 80 to 160 seconds, and the temperature of the constant temperature water bath is 40 to 80° C. for 2 to 4 hours.

4. The method for preparing a long-chain polyamine-mediated biomimetic mineralization-modified recycled coarse aggregate according to claim 1, characterized in that: In the step 2, phosphoric acid is added in 2 to 5 times with continuous stirring, and the stirring time is 80 to 160 seconds.

5. The method for preparing a long-chain polyamine-mediated biomimetic mineralization-modified recycled coarse aggregate according to claim 1, characterized in that: In the step 2, the vacuum impregnation time is 90 to 150 minutes, the negative pressure of the vacuum impregnation is 0.05 to 0.15 MPa, and the temperature of the vacuum impregnation is 30° C. to 60° C.

6. The method for preparing a long-chain polyamine-mediated biomimetic mineralization-modified recycled coarse aggregate according to claim 1, characterized in that: In the step 3, the magnetic stirring time is 5 to 10 minutes, the rotor stirring speed is 800 to 1200 r / min, and the standing time is 3 to 5 days.

7. The method for preparing a long-chain polyamine-mediated biomimetic mineralization-modified recycled coarse aggregate according to claim 1, characterized in that: In the step 3, the mixing time at room temperature is 80 to 160 seconds, and the mixing time after adding ethyl orthosilicate is 5 to 10 minutes.

8. The method for preparing a long-chain polyamine-mediated biomimetic mineralization-modified recycled coarse aggregate according to claim 1, characterized in that: In the step three, the vacuum impregnation time is 6 to 10 hours, the negative pressure is 0.4 to 0.6 MPa, and the temperature is 20° C. to 40° C.

9. The method for preparing a long-chain polyamine-mediated biomimetic mineralization-modified recycled coarse aggregate according to claim 1, characterized in that: In the step 4, the drying temperature is 40-70° C. and the drying time is 36-60 hours.

10. The long-chain polyamine-mediated biomimetic mineralization-modified recycled coarse aggregate obtained by the preparation method of the long-chain polyamine-mediated biomimetic mineralization-modified recycled coarse aggregate according to any one of claims 1 to 9, characterized in that: The particle size of the recycled coarse aggregate is 9.5 mm to 26.5 mm.

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