Preparation of a modified glutinous rice mortar with high bonding strength

Abstract

The present invention discloses a preparation method for a modified glutinous rice mortar with high bonding strength, and relates to the technical field of glutinous rice mortar. The preparation method of the modified glutinous rice mortar of the present invention comprises the following steps: nano-silica is attached to a flaky graphene oxide by a sol-gel method to obtain a GO / NS hybrid, and then the GO / NS hybrid is configured into a dispersion liquid to obtain a GO / NS hybrid dispersion liquid; slaked lime is mixed with the glutinous rice slurry, the GO / NS hybrid dispersion liquid is added, and the modified glutinous rice mortar is obtained after stirring. The present invention utilizes the advantage that flaky GO and nanomaterials have good compatibility, and NS is attached to the surface using flaky GO as a carrier, and then the graphene oxide-nano-silica (GO / NS) hybrid is introduced into the glutinous rice mortar matrix, which greatly improves the modification effect of the glutinous rice mortar, thereby ensuring a good ancient building restoration effect.

Description

Technical Field

[0001] The invention relates to the technical field of glutinous rice mortar, in particular to the preparation of modified glutinous rice mortar with high bonding strength. Background Art

[0002] Lime-based glutinous rice mortar is an effective material for the restoration of ancient buildings, but it suffers from common shortcomings such as low early strength and susceptibility to cracking. Masonry structures using glutinous rice mortar can experience weathering, brittleness, surface peeling, crack development, and tilting over time due to environmental factors. This is primarily due to the fact that the strength of the glutinous rice mortar used as a bonding material is far weaker than that of masonry blocks. This significant difference in strength makes it prone to cracking and through-cracks during use, as well as pulverization and mortar shedding. As a result, glutinous rice mortar fails to fully realize its advantages in the restoration of ancient buildings, limiting its application.

[0003] Therefore, some researchers have conducted research on the modification of sticky rice mortar. On the one hand, the use of nanosilica (NS) to modify lime-based materials has certain research significance. Its modification mechanism manifests as a pozzolanic effect and a nanofilling effect: the incorporation of NS accelerates the hydration process of lime, increases its hardening rate, reacts with calcium hydroxide to form hydrated calcium silicate, promotes the formation of a gel phase, and significantly improves the strength of the lime-based material. Simultaneously, unreacted nanoscale NS can fill internal pores, and NS particles embed in the gel pores, acting as a filler, enhancing the strength and density of the matrix, thereby effectively improving the lime-based material's low early strength and susceptibility to cracking. On the other hand, graphene oxide (GO) has shown promise in the modification of sticky rice mortar. Due to its excellent tensile strength, GO can effectively delay the formation of cracks in the mortar and inhibit their propagation. Furthermore, the oxygen-containing functional groups of GO form strong interfacial bonds with the hydration products, allowing them to withstand external stress and effectively inhibit crack propagation, thereby significantly improving the material's mechanical properties. At the same time, as the hydration reaction proceeds, the oxidized functional groups on the surface of the GO sheets and their edges can provide more nucleation sites for the formation of hydration products, thereby affecting the hydration process, regulating the growth process of the hydration products, refining the crystallite size of calcium hydroxide, refining and closing the pore structure, making the distribution of hydration products more uniform, and significantly enhancing the structural integrity of the material.

[0004] However, both modified materials have their shortcomings. On the one hand, NS particles are fine and have high reactivity. When the dosage is high, NS is prone to agglomeration during the hydration process, affecting the modification effect. On the other hand, GO is easily affected by Ca in an alkaline environment. 2+The ion effect produces serious agglomeration, and this agglomeration is irreversible, which leads to uneven distribution of the modified material inside the mortar and affects the internal structure of the mortar, resulting in a decrease in its mechanical properties and integrity. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a modified glutinous rice mortar with high bonding strength, so as to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the purposes of the present invention is to provide a method for preparing a modified glutinous rice mortar, comprising the following steps:

[0008] Nano-silica was attached to graphene oxide flakes using a sol-gel method to obtain GO / NS hybrids;

[0009] preparing the GO / NS hybrid into a dispersion to obtain a GO / NS hybrid dispersion;

[0010] The slaked lime and glutinous rice slurry are mixed, and the GO / NS hybrid dispersion is added and stirred to obtain the modified glutinous rice slurry.

[0011] Furthermore, the mass of the GO / NS hybrid is 1-0.08% of the mass of calcium hydroxide in the slaked lime.

[0012] Furthermore, the mass concentration of the glutinous rice paste is 5%.

[0013] Furthermore, GO / NS hybrid dispersion was added to control the water-cement ratio of the slurry to 0.8.

[0014] The modified glutinous rice mortar of the present invention has high bonding strength and can meet the performance requirements for repairing ancient buildings.

[0015] Furthermore, the preparation process of the modified glutinous rice ash mortar of the present invention includes the preparation of glutinous rice slurry, the preparation of graphene oxide-nanosilica (GO / NS) hybrid, the dispersion of GO / NS hybrid, and the preparation of modified glutinous rice ash mortar. More specifically, the steps are as follows:

[0016] Preparation of glutinous rice slurry: The type of rice slurry is white glutinous rice, and the concentration of the rice slurry is 5%. First, weigh a certain mass of glutinous rice flour and distilled water (that is, the mass ratio of glutinous rice flour to distilled water is 1:19), mix the two in a pot, and record the liquid level at this time. Then boil it over high heat for 1 hour. During this process, it is necessary to stir constantly to avoid lumps in the glutinous rice slurry. Then adjust the heat to a low heat and continue to boil for 3 hours. During this period, the slurry still needs to be stirred constantly, and an appropriate amount of distilled water needs to be continuously added according to the recorded liquid level to ensure that the liquid level remains unchanged, so as to ensure that the concentration of the glutinous rice slurry remains unchanged. After the boiled glutinous rice slurry cools, it can be used to prepare mortar specimens.

[0017] Preparation of GO / NS hybrid: In the present invention, the GO / NS hybrid dosage is 0.06% of the mass of calcium hydroxide. Nano-silica is attached to flaky graphene oxide using a sol-gel method. After GO and NS are hybridized, NS is uniformly attached to the GO surface by chemical precipitation, so that the NS coating acts as a spacer between the GO sheets, forming a GO / NS hybrid with better dispersion and greater stability. NS not only separates GO in the slurry through physical separation, but also enhances the interfacial bonding between GO and the hydration products. This preserves the volcanic ash activity and large specific surface area of NS, allowing it to react with lime to form a honeycomb CSH, thereby enhancing the mechanical properties of the sticky rice ash mortar. It also preserves the filling and template effects of GO, promoting the hydration reaction and improving the early strength of the hardened lime. At the same time, it can also improve the problem of easy agglomeration of GO and NS.

[0018] Dispersion of the GO / NS hybrid: Prepare a uniformly dispersed GO / NS solution. To prepare the dispersion, first mix the GO / NS with a polycarboxylate-ether plasticizer (PCE) and water in appropriate proportions. Then, ultrasonicate at 150W for 15 minutes to create a uniform aqueous solution of the nanomaterial. The PCE superplasticizer dosage is 1%. Once the uniformly dispersed dispersion is cooled to room temperature, it can be used to prepare the modified glutinous rice ash mortar.

[0019] Preparation of modified sticky rice mortar: Glutinous rice slurry cooled to room temperature was mixed with an appropriate amount of slaked lime. The ultrasonically treated GO / NS dispersion was added, and the slurry was stirred at a water-cement ratio of 0.8 using a mortar mixer. The mortar, stirred for 2-4 minutes, was then placed into the corresponding mold. After preparation, the modified sticky rice mortar material was cured for 5 days before reaching the demolding condition. After demolding, the specimens were cured under natural conditions at a temperature of (20±2)°C and a relative humidity of (60±5)% until they reached the appropriate curing age.

[0020] According to the above preparation steps, a high bonding strength glutinous rice lime mortar material can be obtained, which has a tensile bonding strength of 190 kPa at the age of 28 days, which is a significant improvement of more than 1000% compared with ordinary glutinous rice lime mortar materials.

[0021] The second object of the present invention is to provide modified glutinous rice ash slurry prepared by the above preparation method.

[0022] The third object of the present invention is to provide a modified glutinous rice lime mortar material obtained by curing the above-mentioned modified glutinous rice lime mortar.

[0023] The fourth object of the present invention is to provide the application of the modified glutinous rice mortar material as a material for repairing ancient buildings.

[0024] In view of the shortcomings of nano-silica and graphene oxide, the present invention takes advantage of the good compatibility of flaky GO with nanomaterials, attaches NS to the surface using flaky GO as a carrier, and then introduces graphene oxide-nano-silica (GO / NS) hybrid into the glutinous rice mortar matrix, greatly improving the modification effect of the glutinous rice mortar, thereby ensuring a good ancient building restoration effect.

[0025] The present invention discloses the following technical effects:

[0026] (1) The GO / NS hybrid prepared by the sol-gel method in the present invention solves the problem of easy agglomeration of GO and NS in glutinous rice ash mortar. The flaky structure of GO is used to provide nucleation sites, fully exerting the filling and template effects, retaining the volcanic ash activity and large specific surface area of NS, and thus better exerting its effect in the glutinous rice ash mortar matrix.

[0027] (2) The present invention adds GO / NS hybrid to glutinous rice mortar for modification, and obtains a modified glutinous rice mortar material with a greatly improved tensile bonding strength. The glutinous rice mortar material has excellent performance and is of great significance for the restoration of ancient buildings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 This is a flow chart for preparing GO / NS hybrids in Example 1 of the present invention.

[0030] Figure 2 This is a diagram of the dispersion process of GO / NS hybrid in Example 1 of the present invention.

[0031] Figure 3 This is a microscopic morphology of the unmodified glutinous rice mortar material in Example 1 of the present invention.

[0032] Figure 4 This is a microscopic morphology of the glutinous rice mortar material with a GO content of 0.06% in Comparative Example 1 of the present invention.

[0033] Figure 5 This is the microscopic morphology of the glutinous rice mortar material with a GO / NS dosage of 0.06% in Example 1 of the present invention. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0036] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0037] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0039] Example 1

[0040] 1. Experimental materials: slaked lime, glutinous rice flour, polycarboxylic acid high-efficiency water reducer, single-layer graphene oxide, 95% ethanol, ammonia solution (GR, 25%-28%), tetraethyl orthosilicate solution (AR, 98%), and distilled water.

[0041] The specific chemical composition of slaked lime (calcium hydroxide content of more than 95%) is shown in Table 1, the main performance indicators of polycarboxylic acid high-efficiency water reducer are shown in Table 2, and the specific technical parameters of single-layer graphene oxide are shown in Table 3.

[0042] Table 1

[0043]

[0044] Table 2

[0045]

[0046] Table 3

[0047]

[0048] 2. Preparation of high bonding strength modified glutinous rice mortar:

[0049] (1) Preparation of glutinous rice paste:

[0050] Prepare glutinous rice slurry with a rice slurry concentration of 5%: Weigh glutinous rice flour and distilled water in a ratio of 1:19 by mass, mix the two in a pot, and record the liquid level at this time. Then simmer on high heat for 1 hour. During this process, it is necessary to stir continuously to prevent lumps from forming in the glutinous rice slurry. Then adjust the heat to a low heat and continue to simmer for 3 hours. During this period, the slurry still needs to be stirred continuously, and an appropriate amount of distilled water needs to be continuously added according to the recorded liquid level to ensure that the liquid level remains unchanged, so as to ensure that the concentration of the glutinous rice slurry remains unchanged. After the slurry is cooled, it can be used to prepare mortar specimens and must be used up on the same day.

[0051] (2) Preparation of GO / NS hybrids:

[0052] Tetraethyl Orthosilicate (TEOS) was in situ hydrolyzed and condensed by the sol-gel method to attach NS to GO. The specific preparation process is as follows:

[0053] A graphene oxide suspension was prepared by mixing 120 mg of graphene oxide with 12 ml of distilled water. 300 ml of ethanol was added to the graphene oxide suspension, and the solution was sonicated in a water bath for 1 hour. 5 ml of 28% ammonia was added dropwise to the mixture, and the pH was adjusted to approximately 9 before sonication for another 1 hour. 3 ml of tetraethyl orthosilicate was added, and sonication was performed for 3 hours to obtain a GO / NS dispersion. The resulting GO / NS dispersion was allowed to stand at room temperature for 2 days to ensure complete reaction. The GO / NS dispersion was then centrifuged at 10,000 rpm for 10 minutes to obtain a GO / NS dispersion. After centrifugation, the GO / NS dispersion was washed five times with ethanol and distilled water to remove free silica and uncoated graphene oxide. The resulting impurity-free GO / NS dispersion was vacuum-dried at 60°C to obtain a GO / NS hybrid (GO / NS composite).

[0054] The flow chart of GO / NS hybrid preparation is shown in Figure 1 .

[0055] (3) Dispersion of GO / NS hybrids:

[0056] By using polycarboxylate-ether plasticizer (PCE) as a dispersant and performing ultrasonic dispersion, the GO / NS hybrid was prepared into a uniformly dispersed solution.

[0057] The GO / NS hybrid was first mixed with the appropriate proportions of PCE superplasticizer and water. Ultrasonic treatment was then performed at 150W for 15 minutes to create a uniform dispersion of the nanomaterial. The PCE superplasticizer was added at a 1% concentration. After cooling to room temperature, the uniform dispersion was used to prepare the modified glutinous rice ash mortar.

[0058] The dispersion process of GO / NS hybrids is shown in Figure 2 .

[0059] (4) Preparation of modified glutinous rice mortar:

[0060] Cooled glutinous rice paste to room temperature was mixed with the appropriate amount of slaked lime. The ultrasonically treated GO / NS dispersion was then added, maintaining a water-cement ratio of 0.8. The mortar was stirred using a mortar mixer. After stirring for 2–4 minutes, the mortar was poured into the appropriate mold. The mix design is shown in Table 4.

[0061] Comparative Example 1

[0062] The only difference from Example 1 is that the glutinous rice mortar is modified by using an equal amount of graphene oxide (GO) instead of GO / NS.

[0063] Table 4

[0064]

[0065] The specific test parameters are shown in Table 5. Specifically, for every 500g of calcium hydroxide powder, 10.5g of glutinous rice flour and 199.5g of water were mixed in a ratio of 1:19 to create a 5% glutinous rice paste. 0.3g of the GO / NS hybrid was added, representing 0.06% of the mass of the calcium hydroxide. 5g of the PCE water reducer was added, representing 1% of the mass of the calcium hydroxide. To maintain a constant water-cement ratio of 0.8, 208.9g of water was added during the dispersion preparation.

[0066] Table 5

[0067]

[0068] Curing of modified glutinous rice mortar: After the preparation of the modified glutinous rice mortar material is completed, it needs to be cured for 5 days to reach the demoulding condition. The demoulded specimens are placed under natural conditions of temperature (20±2)℃ and relative humidity (60±5)% for curing and are used after reaching 28 days of age.

[0069] The GO / NS modified sticky rice ash mortar adhesive parts were subjected to a 28-day tensile bond strength test according to the mix ratio in Table 5. The test results are shown in Table 6.

[0070] Table 6

[0071]

[0072] Experimental results show that the average tensile force at failure of the unmodified sticky rice-lime mortar was only 24.08 N, and the average tensile bond strength was 15.05 kPa. However, the modified sticky rice-lime mortar with 0.06% GO / NS hybrid exhibited an average tensile bond strength increase of 1203.06% at failure compared to the unmodified mortar. The presence of NS in the GO / NS hybrid prevents the GO sheets from stacking, resulting in good dispersion. Furthermore, the presence of NS in the GO / NS hybrid induces hydration within the mortar, significantly increasing its strength. Furthermore, the synergistic effect of GO and NS within the mortar results in a denser internal structure and reduced porosity in the modified sticky rice-lime mortar, resulting in a significant improvement in tensile bond strength.

[0073] The micromorphology of the unmodified glutinous rice mortar material, the glutinous rice mortar material with 0.06% GO content and the glutinous rice mortar material with 0.06% GO / NS content in Example 1 was characterized by using a JSM-7800F thermal field emission scanning electron microscope. The results are shown in Figure 2. Figure 3-Figure 5 .

[0074] pass Figure 3It can be seen that the microstructure of the unmodified glutinous rice mortar material is very loose, with many pores and gaps; the degree of carbonization in its microstructure is low, there is a lot of unreacted calcium hydroxide, and the generated calcium carbonate particles are relatively coarse; due to the wrapping of glutinous rice slurry and its biological template effect and regulatory effect on calcium carbonate, the surface has a denser calcite.

[0075] Depend on Figure 4 It can be seen that the modified material with 0.06% GO added has a tighter microstructure than the unmodified glutinous rice ash mortar material due to the modification effect of GO; however, calcium carbonate with uneven distribution due to GO agglomeration can be observed in its microstructure. At the same time, the agglomeration of GO leads to the generation of more obvious interconnected pores inside, resulting in poor modification effect.

[0076] Depend on Figure 5 It can be found that the glutinous rice mortar material modified with 0.06% GO / NS has a significantly denser microstructure due to the nucleation sites provided by the two-dimensional wrinkled structure of GO; the calcium carbonate particles generated by carbonization in its microstructure are uniform in size, arranged evenly and tightly, without obvious grooves, and the microstructure is spherical, clustered and bonded, with good integrity; because GO / NS improves the disadvantage of GO's easy agglomeration, the two work together to make its carbonized structure denser, and the connected pores in the microstructure are significantly reduced, which is manifested in its significantly improved mechanical properties from a macroscopic perspective.

[0077] Based on Example 1, the present invention obtains different modified glutinous rice mortar materials by adjusting the addition amount of GO / NS hybrid, as shown in Table 7.

[0078] Table 7

[0079]

[0080] The tensile bond strength values of the above-mentioned glutinous rice mortar specimens with different numbers are shown in Table 8.

[0081] Table 8

[0082]

[0083] Comparing the above results, the addition of different GO / NS hybrid dosages significantly improved the tensile bond strength of sticky rice-lime mortar, demonstrating the good modification effect of GO / NS hybrid on sticky rice-lime mortar. The optimal GO / NS hybrid dosage of 0.06% significantly increased the tensile bond strength by 1203.06%.

[0084] Compared with the tensile bond strength of 15 kPa of ordinary sticky rice mortar, the tensile bond strength of the modified sticky rice mortar with 0.06% GO / NS hybrid in the present invention can reach 196.11 kPa, an increase of more than 1000%.

[0085] The glutinous rice mortar material prepared by the invention has high tensile bonding strength and good application prospect.

[0086] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing modified glutinous rice mortar, characterized in that: The following steps are involved: Nano-silica was attached to graphene oxide flakes using a sol-gel method to obtain GO / NS hybrids; preparing the GO / NS hybrid into a dispersion to obtain a GO / NS hybrid dispersion; Mixing slaked lime with glutinous rice slurry, adding the GO / NS hybrid dispersion, and stirring to obtain the modified glutinous rice slurry; The mass of the GO / NS hybrid is 1-0.08% of the mass of calcium hydroxide in the slaked lime, and is not 0%; The concentration of the glutinous rice paste is 5%; The GO / NS hybrid dispersion was added to control the water-cement ratio of the slurry to 0.

8.

2. The modified glutinous rice mortar prepared by the preparation method as claimed in claim 1.

3. A modified glutinous rice mortar material, characterized in that: The modified glutinous rice mortar according to claim 2 is obtained by curing.

4. Use of the modified glutinous rice mortar material as claimed in claim 3 as a material for repairing ancient buildings.

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