Preparation of modified glutinous rice mortar with high bonding strength

Abstract

The invention discloses preparation of high-bonding-strength modified glutinous rice mortar, and relates to the technical field of glutinous rice mortar. The preparation method of the modified glutinous rice mortar comprises the following steps: attaching nano silicon dioxide to flaky graphene oxide by adopting a sol-gel method to obtain a GO / NS hybrid, and then preparing the GO / NS hybrid into a dispersion liquid to obtain a GO / NS hybrid dispersion liquid; and mixing slaked lime with the glutinous rice slurry, adding the GO / NS hybrid dispersion liquid, and stirring to obtain the modified glutinous rice mortar. The advantage that flaky GO and a nano material have good compatibility is utilized, the flaky GO is used as a carrier to attach NS to the surface, then a graphene oxide-nano silicon dioxide (GO / NS) hybrid is introduced into a glutinous rice mortar matrix, the modification effect of the glutinous rice mortar is greatly improved, and then a good historic building repairing effect is guaranteed.

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 this material generally has shortcomings such as low early strength and easy cracking. Masonry structures using glutinous rice mortar will experience weathering, brittleness, surface peeling, crack development and main body tilting after long-term environmental influences. The main reason is that the strength of glutinous rice mortar used as a bonding material is much lower than that of masonry blocks. The difference between the two is large. During use, it is very easy to crack and produce through cracks. At the same time, powdering and mortar shedding occur, resulting in glutinous rice mortar not playing its greatest advantage in the restoration of ancient buildings, and its application is subject to certain restrictions.

[0003] Therefore, some researchers have conducted modification research on sticky rice mortar. On the one hand, the selection of nano-silica (NS) to modify lime-based materials has certain research significance. Its modification mechanism is manifested as volcanic ash effect and nano-filling effect: the addition of NS can accelerate the hydration process of lime, increase its hardening speed, react with calcium hydroxide to form hydrated calcium silicate, promote the generation of gel phase, and significantly improve the strength of lime-based materials; at the same time, unreacted nano-scale NS can fill the internal pores, and NS particles are embedded in the gel pores, acting as fillers, enhancing the strength and density of the matrix, thereby effectively improving the problems of low early strength and easy cracking of lime-based materials. On the other hand, graphene oxide (GO) is expected to be applied to the modification research of sticky rice mortar. Due to its excellent tensile strength, GO can effectively delay the formation of cracks in the slurry and inhibit the expansion of cracks; in addition, the oxygen-containing functional groups of GO can form a stable interface bond with the hydration product, can withstand external stress, and effectively inhibit the expansion of cracks, thereby significantly improving the mechanical properties of the material. At the same time, as the hydration reaction proceeds, the oxidized functional groups on the surface of 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 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 has fine particles and high reactivity. When the dosage is high, NS tends to agglomerate during the hydration process, affecting the modification effect. On the other hand, GO is easily affected by Ca in an alkaline environment. 2+The influence of ions causes serious agglomeration, and this agglomeration is irreversible, resulting in uneven distribution of the modified material inside the mortar. The internal structure of the mortar is affected, which is manifested 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 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 flake graphene oxide using a sol-gel method to obtain GO / NS hybrids;

[0009] The GO / NS hybrid is configured into a dispersion to obtain a GO / NS hybrid dispersion;

[0010] The slaked lime is mixed with the sticky rice slurry, and the GO / NS hybrid dispersion is added thereto and stirred to obtain the modified sticky 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 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 the pot evenly, and record the liquid level at this time, and then boil it on 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 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 boiled glutinous rice slurry is cooled, it can be used to prepare mortar specimens.

[0017] Preparation of GO / NS hybrid: The amount of GO / NS hybrid in the present invention is 0.06% of the mass of calcium hydroxide. Nano-silicon dioxide is attached to flaky graphene oxide by a sol-gel method. After GO and NS are hybridized, NS is uniformly attached to the surface of GO by chemical precipitation, so that the NS coating acts as a spacer between GO sheets, forming a GO / NS hybrid with better dispersion and more stability. NS can not only separate GO in the slurry by physical separation, but also enhance the interface bonding between GO and hydration products, so that the volcanic ash activity and its large specific surface area of ​​NS can be retained, so that it reacts with lime to form honeycomb CSH, enhancing the mechanical properties of sticky rice mortar; and the filling and template effects of GO are retained, promoting hydration reaction, improving the early strength of lime after hardening, and at the same time, the problem of easy agglomeration of GO and NS can be improved.

[0018] Dispersion of GO / NS hybrid: GO / NS is prepared into a uniformly dispersed solution. The specific operation of the dispersion liquid requires that GO / NS be evenly mixed with a corresponding proportion of polycarboxylate-ether plasticizer (PCE) and water, and then ultrasonically treated at 150W for 15 minutes to prepare a uniform nanomaterial aqueous solution. The PCE water reducer dosage is 1%. After the uniformly dispersed dispersion liquid is cooled to room temperature, it can be used to prepare modified glutinous rice mortar.

[0019] Preparation of modified sticky rice mortar: Mix the sticky rice slurry cooled to room temperature with the corresponding mass of slaked lime, add the ultrasonically treated GO / NS dispersion, control the water-cement ratio of the slurry to 0.8, and use a mortar mixer to stir. Put the mortar stirred for 2 to 4 minutes into the corresponding mold. After the preparation of the modified sticky rice mortar material, it needs to be cured for 5 days to reach the demoulding condition. The demoulding specimen is placed under natural conditions of temperature (20±2)℃ and relative humidity (60±5)% for curing, and is used when it reaches the corresponding curing age.

[0020] According to the above preparation steps, a high bonding strength glutinous rice ash mortar material can be obtained, the tensile bonding strength of which reaches 190 kPa at the age of 28 days, which is significantly improved by more than 1000% compared with the ordinary glutinous rice ash mortar material.

[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 ash mortar material obtained by curing the above-mentioned modified glutinous rice ash mortar.

[0023] The fourth object of the present invention is to provide the application of the modified glutinous rice mortar material as an ancient building repair material.

[0024] In view of the shortcomings of nano-silica and graphene oxide, the present invention utilizes the advantage of good compatibility between flaky GO and 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, thereby 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 that GO and NS are easy to agglomerate in glutinous rice mortar. The flaky structure of GO is used to provide nucleation sites, which fully exerts the filling and template effects, retains the volcanic ash activity and large specific surface area of ​​NS, and thus better exerts its effect in the glutinous rice mortar matrix.

[0027] (2) The present invention adds GO / NS hybrids to glutinous rice mortar for modification, and obtains a modified glutinous rice mortar material with 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 drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[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 hybrids 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 should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

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

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

[0037] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary 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] Among them, the specific chemical composition content 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, mix the two in a pot, record the liquid level at this time, and then boil over high heat for 1 hour. During this process, stir continuously 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 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 boiled glutinous rice slurry is cooled, it can be used for the preparation of 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] 120 mg of graphene oxide and 12 ml of distilled water were used to prepare a graphene oxide suspension, 300 ml of ethanol was added to the graphene oxide suspension, and the solution was ultrasonically treated in a water bath for 1 hour; 5 ml of ammonia water (28%) was dropped into the mixed solution, and the pH value was adjusted to about 9 and then ultrasonically treated for 1 hour; 3 ml of tetraethyl orthosilicate was added, and the GO / NS dispersion was ultrasonically treated for 3 hours. The prepared GO / NS dispersion was allowed to stand at room temperature for 2 days to ensure complete reaction. The GO / NS dispersion was obtained by centrifugation at 10000 rpm for 10 minutes. After centrifugation, the GO / NS dispersion was washed 5 times with ethanol and distilled water to remove free silica and uncoated graphene oxide. The impurity-free GO / NS dispersion obtained by centrifugation and washing was vacuum dried at 60°C to obtain a GO / NS hybrid (GO / NS composite material).

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

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

[0056] The GO / NS hybrid was configured into a uniformly dispersed solution by using polycarboxylate-ether Plasticizer (PCE) as a dispersant and performing ultrasonic dispersion.

[0057] The specific operation is to first mix the GO / NS hybrid with the corresponding proportion of PCE water reducer and water, and then use 150W ultrasonic treatment for 15 minutes to prepare a uniform nanomaterial dispersion, in which the PCE water reducer dosage is 1%. After the uniformly dispersed dispersion is cooled to room temperature, it can be used to prepare modified sticky 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] The glutinous rice paste cooled to room temperature was mixed with the corresponding mass of slaked lime, and the GO / NS dispersion after ultrasonic treatment was added. The water-cement ratio of the paste was controlled to be 0.8, and a mortar mixer was used for stirring. The mortar stirred for 2 to 4 minutes was loaded into the corresponding mold. The mix ratio 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 parameters of the test 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 selected in a ratio of 1:19 to prepare a 5% concentration of glutinous rice paste; 0.3g of GO / NS hybrid was added at 0.06% of the mass of calcium hydroxide; 5g of PCE water reducer was added at 1% of the mass of calcium hydroxide; in order to control the water-cement ratio to be 0.8, 208.9g of water was added when preparing the dispersion.

[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 demoulding specimens are placed under natural conditions of temperature (20±2)℃ and relative humidity (60±5)% for curing and are used when they reach 28 days old.

[0069] According to the mix ratio in Table 5, the GO / NS modified sticky rice mortar bonding parts were tested for 28d tensile bond strength. The test results are shown in Table 6.

[0070] Table 6

[0071]

[0072] The experimental results show that the average tensile force of the unmodified glutinous rice mortar at the time of failure is only 24.08N, and the average tensile bond strength is 15.05kPa; while the average tensile bond strength of the modified glutinous rice mortar after adding 0.06% GO / NS hybrid increased by 1203.06% compared with the unmodified mortar at the time of failure. Due to the presence of NS in the GO / NS hybrid, the GO sheets are not easy to accumulate and have good dispersibility; and the presence of NS in the GO / NS hybrid will cause hydration reaction inside the mortar, and the strength will be significantly improved; at the same time, the synergistic effect of GO and NS in the slurry makes the internal structure of the modified glutinous rice mortar bond more compact and the porosity smaller, so the tensile bond strength is significantly improved.

[0073] The microstructures 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 were characterized by using a JSM-7800F thermal field emission scanning electron microscope. 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 holes and gaps; the degree of carbonization in its microstructure is low, there are more unreacted calcium hydroxide, and the generated calcium carbonate particles are 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 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 more obvious interconnected pores inside, resulting in poor modification effect.

[0076] Depend on Figure 5 It can be seen that the glutinous rice mortar material modified with 0.06% GO / NS has a significantly tighter 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; since GO / NS improves the shortcoming of GO's easy agglomeration, the two work together to make its structure denser after carbonization, and the connected pores in the microstructure are significantly reduced, which is manifested in a significant improvement in its 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 amounts of GO / NS hybrids can significantly improve the tensile bond strength of sticky rice mortar, indicating that GO / NS hybrids have a good modification effect on sticky rice mortar. The optimal amount of GO / NS hybrids is 0.06%, and the tensile bond strength is increased by 1203.06%, which is a significant increase.

[0084] Compared with the tensile bonding strength of 15 kPa of ordinary glutinous rice mortar, in the present invention, the tensile bonding strength of the modified glutinous rice mortar with 0.06% GO / NS hybrid added 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 only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing modified glutinous rice mortar, characterized in that: The following steps are involved: Nano-silica was attached to flake graphene oxide using a sol-gel method to obtain GO / NS hybrids; The GO / NS hybrid is configured into a dispersion to obtain a GO / NS hybrid dispersion; The slaked lime is mixed with the sticky rice slurry, and the GO / NS hybrid dispersion is added thereto and stirred to obtain the modified sticky rice slurry.

2. The preparation method according to claim 1, characterized in that: 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%.

3. The preparation method according to claim 1, characterized in that: The concentration of the glutinous rice paste is 5%.

4. The preparation method according to claim 1, characterized in that: The GO / NS hybrid dispersion was added to control the water-cement ratio of the slurry to 0.

8.

5. The modified glutinous rice mortar prepared by the preparation method according to any one of claims 1 to 4.

6. A modified glutinous rice mortar material, characterized in that: The modified glutinous rice ash slurry according to claim 5 is obtained by curing.

7. Use of the modified glutinous rice mortar material as claimed in claim 6 as an ancient building repair material.

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