A polyacrylamide-modified enhanced geopolymer gel material, and methods of making and using the same

Abstract

The present application relates to a kind of polyacrylamide modified reinforced geopolymer gel materials and its preparation method and use method, the gel material is mixed by geopolymer base material and polyacrylamide, and the polyacrylamide additive amount is 3.5% to 5% of the mass of geopolymer base material.The advantage of the present application is that geopolymer base material is fully mixed with the appropriate proportion of polyacrylamide, without arraying treatment, the flowability of the suitable adhesion capacity can be obtained, which can be immediately mixed and stirred with sedimentary rock aggregate, which can not only uniformly cover aggregate, but also adhere to the surface of aggregate without sinking, and then directly coated and maintained for more than 144h to obtain reinforced aggregate, compared with the aggregate obtained by mixing aggregate with geopolymer base material without adding polyacrylamide and increasing adhesion capacity by arraying, the compressive strength can be increased by 3.1% to 8.2%, and the bending tensile strength can be increased by 44.4% to 61.1%.

Description

Technical Field

[0001] This invention belongs to the field of engineering materials and relates to a polyacrylamide-modified and reinforced geopolymer gel material, its preparation method, and its application method. Background Technology

[0002] According to the load-bearing water-storage road structure proposed by Cao Rongchuan, the road base is constructed using a geopolymer-based cohesive. This cohesive is obtained by coating and aging a geopolymer gel with a silicon-to-aluminum molar ratio (Si / Al MR) of 2, an aluminum-to-sodium molar ratio (Al / Na MR) of 0.85–1.00, and a water-to-sodium molar ratio (H₂O / Na₂O MR) of 14–16 for 24 hours, then mixing and curing it with sedimentary rock coarse aggregate with a particle size of 16.5–20.00 mm for over 60 hours. This cohesive exhibits an unconfined compressive strength exceeding 9.0 MPa, a flexural tensile strength exceeding 1.5 MPa, a porosity exceeding 30%, and good water stability. Therefore, a load-bearing water-storage road with a geopolymer-based cohesive base can withstand more than 10 hours of continuous heavy rainfall (50 mm / d) even when the municipal drainage system is completely paralyzed, bearing heavy loads while also acting as a "super reservoir."

[0003] However, the aging time for geopolymer gels is not entirely fixed. Although Davidovits, sharing the same view as Cao Rongchuan, suggests aging for 24 hours (20°C, 50% relative humidity) in his book *Geopolymer Chemistry and Application*, this aging time is actually derived from laboratory data. In engineering sites, it is difficult to maintain a constant environment of 20°C and 50% relative humidity, making it difficult to precisely control the viscosity of geopolymers. Therefore, significantly increasing the viscosity of geopolymers in a short period of time and reducing or even avoiding aging has become an urgent problem to be solved in engineering applications. To address the aforementioned issues, a common method is to modify geopolymer gels by adding admixtures. For example, Lateef N. Assi et al. added sucrose as an admixture to geopolymer gels and found that the hardening time of the geopolymer gels increased by more than 100%. Teerasak Yaowarat et al. studied the use of natural latex (NRL) as a cement additive, which improved the flexural strength of concrete pavements. C. Celauro and F. G. Praticò studied the addition of basalt fibers to asphalt mixtures, which improved the friction between tires and pavements, pavement stability, and road weather resistance. However, to date, no technology has been reported that can significantly increase the viscosity of geopolymers in a short time, reduce or even avoid aging, and effectively enhance the performance of geopolymer aggregates after bonding with aggregates, after modification with admixtures. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a polyacrylamide-modified and reinforced geopolymer gel material, its preparation method and application method, in order to overcome the above-mentioned deficiencies in the prior art.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a geopolymer gel material modified and reinforced by polyacrylamide, which is composed of geopolymer base material and polyacrylamide, wherein the amount of polyacrylamide added is 3.5% to 5% of the mass of geopolymer base material.

[0006] Based on the above technical solutions, the present invention may have the following further specific or better options.

[0007] Specifically, the geopolymer base material is compounded from metakaolin, water glass, water, and sodium hydroxide in a ratio of silicon to aluminum of 2, aluminum to sodium of 0.85 to 1.00, and water to sodium of 14 to 16.

[0008] Specifically, the polyacrylamide is anionic, and its molecular weight is preferably high, ranging from 15 million to 22 million. Common molecular weights of anionic polyacrylamides on the market range from 6 million to 22 million, and it has been verified that their performance enhancement effect on geopolymers is positively correlated with molecular weight. Therefore, this invention selects a polyacrylamide with a larger molecular weight.

[0009] Based on the above technical solution, the present invention also provides a method for preparing the above-mentioned polyacrylamide-modified and reinforced geopolymer gel material, which includes the following steps: 1) preparing geopolymer base material; 2) adding a specified proportion of polyacrylamide to the geopolymer base material, mixing and stirring for 25-35 min, and letting it stand for 8-12 min to obtain the product.

[0010] In step 2), the mixing is carried out in a mixer, and the mixing speed is preferably 80-120 r / min.

[0011] Based on the above technical solution, the present invention also provides a method for using the above-mentioned polyacrylamide-modified and reinforced geopolymer gel material: after the geopolymer gel material is prepared, it is immediately and thoroughly mixed with sedimentary rock coarse aggregate of 16.5-20.0 mm, and then covered with a black film for water-proof curing for more than 144 hours to obtain the reinforced geopolymer aggregate. The mass ratio of sedimentary rock coarse aggregate to geopolymer gel material is 2-6:1.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] The polyacrylamide-modified geopolymer gel material provided by this invention, after being fully mixed with a geopolymer base and an appropriate proportion of polyacrylamide, can achieve suitable adhesion and fluidity without fractionation treatment. It can be immediately mixed and stirred with sedimentary rock aggregates, which can uniformly cover the aggregates and adhere to the aggregate surface without settling. After direct coating and curing for more than 144 hours, a reinforced aggregate can be obtained. Compared with the aggregate obtained by adding polyacrylamide and increasing adhesion through fractionation before mixing with aggregates, the reinforced aggregate can increase the compressive strength by 3.1% to 8.2% and the flexural strength by 44.4% to 61.1%.

[0014] In this invention, the addition of polyacrylamide to the geopolymer gel material increases both the compressive strength and flexural strength of the resulting aggregate. The reason for this is speculated as follows:

[0015] 1. Due to the inherent structure of polyacrylamide, a type of organic polymer, its main chain has a certain degree of internal rotational freedom. When stress is applied, the structure is stretched, and when the stress is removed, it returns to its original state. For inorganic polymers, the three-dimensional network structure is constructed by silicon-oxygen bonds and aluminum-oxygen bonds. These covalent bonds prevent each Si, O, and Al atom from moving freely within the crystal. The addition of polyacrylamide improves the flexibility and elasticity of the original system.

[0016] 2. This is caused by polyacrylamide altering the original structure of the geopolymer, such as... Figure 1 As shown, when polyacrylamide powder is added to the geopolymer matrix, it undergoes a cross-linking reaction while dissolving, transforming from a chain structure into a flexible network structure, and is connected to the rigid network structure of the geopolymer through van der Waals forces; simultaneously, the amide groups in the polyacrylamide react chemically with the hydroxyl groups in the geopolymer, such as... Figure 2 As shown, the original functional groups are destroyed, and the two network structures are connected by sharing oxygen atoms and forming chemical bonds. As the geopolymer hardens, this inorganic and organic interwoven polymer network structure effectively improves the toughness of the aggregate; while the chain-like polyacrylamide also forms a three-dimensional network structure due to the cross-linking reaction and is connected to the geopolymer by chemical bonds, thus becoming insoluble in water. Polyacrylamide improves the adhesion of the gel and the strength of the aggregate to a certain extent; its addition not only avoids aging time and accelerates the condensation reaction of the geopolymer, but also enhances the integrity of the gel, allowing its flexible structure to fuse with the rigid structure of the geopolymer through chemical bonds and van der Waals forces. Attached Figure Description

[0017] Figure 1 This is the chemical reaction formula for the self-crosslinking of polyacrylamide;

[0018] Figure 2This is the chemical reaction formula for the reaction between polyacrylamide and the hydroxyl functional groups in the geopolymer base material;

[0019] Figure 3 Images show the good adhesion of the modified and reinforced geopolymer gel material provided by this invention after preparation (a) shows the polyacrylamide-modified and reinforced geopolymer gel adhering to the aggregate immediately after production and then being pulled apart, exhibiting a stringy appearance; b) shows the polyacrylamide-modified and reinforced geopolymer gel adhering to the putty knife immediately after production without dripping downwards; c) shows the geopolymer gel without added polyacrylamide continuously dripping downwards from the putty knife without aging and thickening. Detailed Implementation

[0020] The principles and features of the present invention are described below with reference to specific embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0021] Unless otherwise specified, all pharmaceuticals used in the following examples are commercially available products, and all methods used are conventional methods in the art.

[0022] To avoid repetition, the polyacrylamide-modified and reinforced geopolymer gel materials in the following examples were all prepared by the following methods, and the method for mixing the gel material with aggregate and curing it to form a reinforced aggregate is also described below:

[0023] First, the geopolymer gel was prepared. Metakaolin, water glass, water, and sodium hydroxide were prepared according to the following formula: a silicon-aluminum molar ratio (Si / Al MR) of 2, an aluminum-sodium molar ratio (Al / Na MR) of 0.85–1.00, and a water-sodium molar ratio (H2O / Na2O MR) of 14–16.

[0024] The formulas for converting the amount of substance to the mass of the corresponding material are as follows:

[0025]

[0026]

[0027]

[0028]

[0029]

[0030] Where n Na n Al n H , These represent the amounts of sodium, aluminum, hydrogen, and water in the reaction system, respectively, in moles; m NaOH m水玻璃 m 偏高岭土 m 去离子水 These are the masses of the raw materials: sodium hydroxide granules, water glass solution, metakaolin, and deionized water, in grams; M NaOH , These are the relative molecular masses of the corresponding compounds or elements, expressed in g / mol, with values ​​of 40, 62, 102, and 18 respectively.

[0031] Then, weigh the geopolymer gel matrix (hereinafter referred to as gel), and add 3.5% to 5% of the gel mass of 22 million molecular weight anionic polyacrylamide (anionic polyacrylamide with a molecular weight of 15 million to 22 million has been verified to have a good effect on the reinforcement and modification of geopolymer gel; for ease of comparison between various examples and comparative examples, only 22 million molecular weight is selected here). Mix and stir for 30 minutes at a stirring speed of 100 r / min. After standing for 10 minutes, it can be directly mixed and stirred with sedimentary rock coarse aggregate of 16.5 to 20.0 mm. The mass ratio of sedimentary rock coarse aggregate to geopolymer gel material is 4:1. At this time, the gel achieves a balance between adhesion and fluidity, having both the fluidity to uniformly cover the aggregate and the adhesion to the aggregate surface without sinking. Figure 3 As shown in (a) and (b), the gel with the same formulation, without the addition of polyacrylamide and without aging, exhibits the same adhesion ability. Figure 3 As shown in (c). After mixing, directly cover and cure for more than 144 hours to obtain the enhanced aggregate.

[0032] Table 1 below lists the gels in various examples where different proportions of polyacrylamide were added, and the gels did not age after the addition:

[0033] Table 1. Effects of polyacrylamide on geopolymer gels (non-aged) and aggregates

[0034]

[0035] Note: The control samples in Table 1 are gel samples without added polyacrylamide, but the resulting gels need to be aged for 24 hours; "W" indicates that the gel has too much fluidity (insufficient adhesion) and cannot be used; "G" indicates that the gel has both good adhesion and fluidity; "-" indicates that the sample cannot be prepared due to excessive gel fluidity. As shown in Table 1, when the amount of polyacrylamide added is 3.5% to 5% (Examples 8 to 11), the compressive strength of the resulting reinforced aggregate can be increased by 3.1% to 8.2% and the flexural strength can be increased by 44.4% to 61.1% compared with the aggregate obtained by adding no polyacrylamide and increasing adhesion through arraying before mixing with aggregate.

[0036] In addition, to understand the effects of arraying and polyacrylamide addition on the geopolymer gel matrix and the final aggregates, the present invention also conducted the experiments shown in Table 2 below:

[0037] Table 2. Effects of polyacrylamide on geopolymer gels (aged) and aggregates

[0038]

[0039] Note: The control samples in Table 2 are gel samples without added polyacrylamide additives, but the resulting gels need to be aged for 24 hours. "S" indicates that the gel is too viscous; "G" indicates that the gel has both good adhesion and flowability; "-" indicates that the sample could not be prepared because the gel was too viscous.

[0040] A detailed analysis of Tables 1 and 2 above leads to the following conclusions:

[0041] As shown in Table 1, when polyacrylamide is added to 3.5% of the gel mass without aging, it exhibits strong adhesion, uniformly coating the graded crushed stone without settling. However, if 3.5% polyacrylamide is added after aging the gel for 24 hours, the gel becomes too viscous and unusable. Details are shown in Table 2. This phenomenon confirms the following two points: 1) Aging increases adhesion because, over time, the matrix undergoes condensation in the alkali activator to form polymer micelles; 2) Polyacrylamide can replace the aging process to increase adhesion because it accelerates the condensation reaction of the gel, and its polymer structure enhances the overall integrity of the gel. Figure 3 As shown in (a) and (b), the geopolymer gel with added polyacrylamide still exhibits a filamentous appearance after separation.

[0042] Furthermore, Tables 1 and 2 show that when the proportion of polyacrylamide is 2.5% and 3.0%, the gel is too fluid before aging and too viscous after aging, making it impossible to prepare aggregates. Therefore, when aging is performed, the amount added should not exceed 2.0%, and when no aging is performed (by using polyacrylamide instead of aging), the amount added should be selected between 3.5% and 5.0%. Polyacrylamide has a positive effect on the compressive strength and flexural strength of aggregates. Regarding compressive strength, when the gel is not aged, 5% polyacrylamide increases the compressive strength from the initial 9.7 MPa to 10.5 MPa. When the gel is aged, the compressive strength also increases with the amount of polyacrylamide added. Regarding flexural strength, when the aggregate is not aged, adding 3.5% polyacrylamide increases the flexural strength to 2.6 MPa, which is 44.4% higher than the control sample. When the gel is aged, adding 2.0% polyacrylamide also increases the flexural strength to 2.2 MPa.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a polyacrylamide-modified and reinforced geopolymer gel material, characterized in that, Includes the following steps: 1) The geopolymer base material is prepared by compounding metakaolin, water glass, water and sodium hydroxide in a ratio of silicon to aluminum of 2, aluminum to sodium of 0.85 to 1.00 and water to sodium of 14 to 16. 2) Add polyacrylamide to the geopolymer base material obtained in step 1), wherein the amount of polyacrylamide added is 3.5% to 5% of the mass of the geopolymer base material, and the polyacrylamide is anionic with a molecular weight of 15 million to 22 million. Mix and stir for 25 to 35 minutes, and let stand for 8 to 12 minutes to obtain the polyacrylamide-modified and reinforced geopolymer gel material.

2. The method for preparing a polyacrylamide-modified and reinforced geopolymer gel material according to claim 1, characterized in that, The mixing in step 2) is carried out in a mixer at a speed of 80-120 r / min.

3. A method for using a polyacrylamide-modified and reinforced geopolymer gel material prepared according to any one of claims 1 to 2, characterized in that, After the geopolymer gel material is prepared, it is directly mixed and stirred with sedimentary rock coarse aggregate of 16.5-20.0 mm, and then covered with a black film for water-proof curing for more than 144 hours to obtain the enhanced geopolymer aggregate. The mass ratio of sedimentary rock coarse aggregate to geopolymer gel material is 2-6:1.

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