A rapid curing process for geopolymer-based materials

Abstract

The application discloses a rapid curing process of a geopolymer-based material. The process comprises the following steps: (1) stirring and dissolving sodium hydroxide and sodium silicate in water, (2) mixing and stirring silico-aluminate material and quartz sand, mixing and stirring the final stirring product (1) and the final stirring product (2) with a special curing agent of the application, and finally pouring the above-mentioned mixed stirring product into a mold. The application adopts silico-aluminate raw material compounding and activator optimization technology, and solves the problem of poor stability of the geopolymer material. By optimizing the ratio of raw materials such as fly ash and slag, improving the content of active silicon aluminum components in the raw materials, and improving the reaction characteristics of the silico-aluminate raw material and the alkali activator, a fast-hardening material with an initial setting time less than 30 min and a 1h compressive strength of 5-70 MPa can be prepared. The geopolymer-based material prepared by the application has good compressive strength, bending strength, rapid curing and good durability, and can play an important role in fast repair and construction engineering, marine engineering and protection engineering.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of geopolymer-based materials, and particularly relates to a rapid curing process of a geopolymer-based material. BACKGROUND

[0002] Geopolymer is a new type of inorganic non-metallic material, which refers to a three-dimensional network structure polymer formed by silicate and aluminate materials (such as fly ash, slag, metakaolin, etc.) as raw materials under the action of an alkaline activator. Geopolymer-based materials have chemical composition and structural characteristics similar to natural rocks, and exhibit excellent mechanical properties, durability and environmental performance, and are considered one of the most promising green cementitious materials.

[0003] Since the concept of geopolymer was first proposed by French scientist Davidovits in the 1970s, geopolymer-based materials have been widely used in the fields of construction, municipal administration, transportation, etc. and gradually expanded to special engineering fields after half a century of development. In recent years, the application value of geopolymer-based materials in extreme service environments such as marine engineering and military engineering has attracted more and more attention and research.

[0004] Compared with traditional cement-based materials, geopolymer-based materials mainly have the following advantages: (1) excellent mechanical properties: geopolymer-based materials have high strength and high toughness, and the compressive strength of conventional formulations can reach 60-80 MPa, and through optimization design, the ultra-high strength requirement of 100-150 MPa can be met; at the same time, the tensile and bending strength of geopolymer-based materials is significantly higher than that of ordinary concrete, and the fracture toughness can be increased by 3-5 times; (2) good durability: the microstructure of geopolymer-based materials is more compact and has low porosity, so it has excellent impermeability, frost resistance and corrosion resistance. In harsh environments such as seawater, acid, alkali and salt, geopolymer-based materials can maintain stable performance for decades to hundreds of years; (3) significant environmental benefits: the production of geopolymer-based materials using industrial waste as raw materials can consume 0.65-0.98 tons of fly ash, slag and other waste per ton of product. At the same time, compared with cement production, the carbon dioxide emissions of geopolymer production process can be reduced by 60-80%. The development of geopolymer-based materials helps to achieve the goals of waste resource utilization and low-carbon emission reduction. (4) outstanding economic benefits: geopolymer-based materials use low-cost industrial by-products as main raw materials, and have simple production process and low energy consumption, so they have obvious cost advantage. Taking fly ash-based geopolymer as an example, the raw material cost is only 50-60% of that of ordinary Portland cement. Considering the high-strength and lightweight characteristics of the material, transportation costs, mechanical equipment investment and labor costs can be significantly reduced in engineering applications, and the comprehensive economic benefits are more prominent.

[0005] However, the existing geopolymer material is difficult to simultaneously consider the rapid curing performance and excellent compression resistance, bending resistance and other performances, therefore, the present application provides a rapid curing process of geopolymer base material. SUMMARY

[0006] In order to overcome the above-mentioned defects of the prior art, the embodiment of the present application provides a rapid curing process of geopolymer base material, which solves the technical challenges faced by the existing geopolymer base material in the application of special fields such as marine engineering and military engineering. The present application innovates in the aspects of material, process and equipment, and overcomes a series of key technical problems, and the main innovations include the following three aspects:

[0007] 1. Material design aspect: (1) The problem of poor stability of the geopolymer base material is solved by using silicate and aluminate raw material compounding and activator optimization technology. By optimizing the composition and ratio of fly ash, slag and other raw materials, the content of active silicon aluminum components in the raw materials is increased, and the reaction characteristics of silicate and aluminate raw materials and alkali activator are improved, so that the strength, durability and other performances of the geopolymer are stable and controllable; (2) The present application provides a new type of composite alkali activator, which breaks through the bottleneck of insufficient activation capacity of conventional single alkali activator. Sodium hydroxide, water glass and sodium carbonate are compounded to strengthen the dissolution and hydrolysis of silicate and aluminate raw materials, accelerate the formation of silicate and aluminate gel, and increase the strength of the geopolymer matrix by 30-50%; (3) The present application innovatively proposes a new method for modifying mineral admixtures of geopolymer base material, which solves the problem of cracking of geopolymer base material. By adding fine aggregate and composite expansion agent, the particle size distribution of geopolymer mixture is optimized, the chemical shrinkage in the hardening process is compensated, the dry shrinkage and self-shrinkage deformation is controlled, and the cracking tendency is reduced by more than 80%.

[0008] 2. Preparation process aspect: (1) The present application develops a thickening modification technology of active mineral admixture for geopolymer slurry material, which breaks through the bottleneck of large viscosity, poor fluidity and difficult pumping of geopolymer base material. By adding nano-silica, ultra-fine fly ash and other active mineral admixures, the rheological properties of geopolymer mixture are optimized, the stability and pumpability of the slurry are improved, and the conveying distance is more than 200m under the conventional pumping equipment; (2) The present application provides a special additive for rapid curing geopolymer shotcrete, which solves the problem of rapid flow of material after shotcrete. A rapid setting and thickening composite additive is used to strengthen the bonding and initial setting of geopolymer slurry, control the slump and rebound rate of shotcrete, and increase the forming thickness and strength of shotcrete by more than 50%; (3) The present application innovatively proposes a new process of steam curing and electric heating curing for geopolymer components, which breaks through the bottleneck of slow condensation and hardening of geopolymer base material at room temperature. By optimizing the curing temperature and humidity parameters, the hydration of silicate and aluminate and the formation process of geopolymer gel are promoted, and the demolding strength and early strength of geopolymer components are increased by 1-2 times.

[0009] 3. Equipment R&D: (1) The application provides a full-automatic polymer concrete production equipment, which realizes integrated intelligent control from raw material metering to finished product discharge. Modular design is adopted, and units such as powder storage, metering and weighing, mixing and mixing, conveying and pumping are integrated, the production efficiency is improved by 50%, and the product quality stability is improved by 30%; (2) The application provides a lightweight and high-precision geopolymer spraying device, which breaks through the bottleneck of low efficiency and unstable quality of manual spraying. The spraying efficiency is 3-5 times that of manual operation; (3) The application innovatively develops a complete set of equipment for 3D printing of geopolymer-based materials, filling the gap of large-scale geopolymer 3D printing equipment in China. Modular design is adopted, including a mixing and feeding unit, a printing execution unit and a motion control unit, and the maximum printing size can reach 10m*10m*6m, and the printing accuracy can reach ±2mm.

[0010] 4. The application develops a new type of curing agent. A polyether amine (Cu-S-ATPE) containing a dynamic Cu-S bond is designed. The synthesis path is as follows: thiol groups (-SH) are introduced into the polyether amine segment, and a dynamic Cu-S coordination bond is formed with copper salt. During the curing process, the dynamic bond reversibly breaks and recombines at high temperature, realizing self-repairing ability. Performance advantages: self-repairing efficiency is improved, tensile strength retention rate is improved, and curing time is greatly shortened by several orders of magnitude.

[0011] The breakthrough of the above key core technology significantly improves the performance level and preparation efficiency of geopolymer-based materials, expands their application range in special fields such as marine engineering and military engineering, and provides new material and technical reserves for the construction of related engineering fields in China.

[0012] The application discloses a rapid curing process of geopolymer-based materials, which comprises the following steps: (1) stirring and dissolving sodium hydroxide and sodium silicate in water, (2) mixing and stirring silica-alumina material and quartz sand, mixing and stirring the final stirring material of (1) and the final stirring material of (2) with a special curing agent of the application, and finally pouring the above-mentioned mixed stirring material into a mold.

[0013] The specific process of step (1) stirring and dissolving sodium hydroxide and sodium silicate in water is as follows: the weighed NaOH and Na2SiO3 are slowly added into a small-mouth plastic container with a total water amount of 70%, and stirred until completely dissolved, and the stirring speed is 100-200 rpm.

[0014] The specific process of step (2) mixing and stirring silica-alumina material and quartz sand is as follows: the weighed total graded quartz sand is poured into a 20-30L stirring machine in sequence and stirred for 1-3min, and then the silica-alumina material is continuously added and stirred for 1-3min until the powder and quartz sand are uniformly mixed, and the stirring speed is 100-200 rpm.

[0015] The mixing and stirring of the final mixture (1) and the final mixture (2) with the special curing agent of the application is carried out as follows: the final mixture (1) and the final mixture (2) with the special curing agent of the application are added to a mixer, and covered and started to stir for 1-3 min; then the remaining 20% of the water used to clean the mixing vessel is added to the mixer, and covered and fully stirred for 5 min; and the stirring is stopped; the stirring speed is 100-200 rpm.

[0016] The mixing and stirring of the final mixture (1) and the final mixture (2) with the special curing agent of the application is carried out as follows: the final mixture (1) and the final mixture (2) with the special curing agent of the application are added to a mixer, and covered and started to stir for 1-3 min; then the remaining 20% of the water used to clean the mixing vessel is added to the mixer, and covered and fully stirred for 5 min; and the stirring is stopped; the stirring speed is 100-200 rpm.

[0017] The silico-alumina material is slag powder, metakaolin and silica fume; the ratio of the amount of metakaolin to the amount of slag powder is (0.5-1.5) : 1; the average particle size of the silica fume is 0.1-0.15 µm; and the specific surface area of the silica fume is 23 m 2 / g.

[0018] The amount of sodium hydroxide added is 15-20% of the amount of the silico-alumina material; the amount of sodium silicate with a modulus of 1.2 added is 10-30% of the amount of the silico-alumina material; and the total amount of the two, i.e. the total amount of the activator in the application and the total amount of the gel material in the application, is 0.3-0.5.

[0019] The graded quartz sand has a mass ratio of medium sand to fine sand of (6-8) : (2-4), and the total amount of the graded quartz sand is 20-30% of the amount of the silico-alumina material; the particle size distribution of the graded quartz sand is 0.15-0.6 mm; and the bulk density of the graded quartz sand is ≥ 1.6 g / cm 3 ;

[0020] The amount of the special curing agent of the application added is 1-5% of the amount of the silico-alumina material; and the water-binder ratio of the application is 0.34-0.42.

[0021] The application also provides a preparation method of the special curing agent of the application.

[0022] Step 1. Synthesis of a polyether amine matrix: polyoxyethylene glycol with a molar ratio of (1-2) : (1-3) is mixed with diethylenetriamine and added to a suitable amount of DMF; under the action of a suitable amount of catalyst p-toluenesulfonic acid, the mixture is reacted at a temperature of 110-120 ℃ and under a negative pressure of 0.1 MPa for 7-8 hours to obtain the polyether amine matrix, which is referred to as ATPE;

[0023] Step 2. Thiolation modification, that is, introducing -SH group: a certain amount of thiolation agent mercaptoethanol and the ATPE obtained in step 1 above are added to a certain amount of anhydrous tetrahydrofuran, and then under the action of a catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) at 50-60°C, under the protection of a noble gas, the reaction is carried out for 22-24 hours to obtain S-ATPE;

[0024] Step 3. Dynamic Cu-S network construction: a certain amount of S-ATPE obtained in step 2 above is mixed with a certain amount of cuprous chloride and added to a certain amount of solvent acetonitrile, under the dispersion of the dispersion medium nanosilica aerogel, stirring at 75-80°C for 10-12 hours, and the stirring speed is 600-800 rpm, and finally the special curing agent Cu-S-ATPE of the application is obtained.

[0025] Preferably, the ratio of the amount of metakaolin to the amount of ground granulated blast furnace slag (MK / GGBS) is 0.30-0.40, and further preferably 0.4.

[0026] Preferably, the addition amount of the graded quartz sand is 20-30% of the addition amount of the silico-alumina material, and further preferably 20%;

[0027] Preferably, the addition amount of the special curing agent of the application is 1-5% of the addition amount of the silico-alumina material, and further preferably 3%;

[0028] Preferably, the particle size distribution of the graded quartz sand is 0.15-0.6mm, and the bulk density

[0029] ≥1.6g / cm 3 , and further preferably 0.5mm, and the bulk density ≥1.6g / cm 3 ;

[0030] Preferably, the molar ratio of the polyoxyethylene glycol to diethylenetriamine is (1-2):

[0031] (1-3), and further preferably 1:1;

[0032] Preferably, the reaction temperature in step 1 is 110°C, and the reaction time is 8 hours;

[0033] Preferably, the molar ratio of the polyether amine matrix to the thiolation agent mercaptoethanol in step 2 above is 1:1;

[0034] Preferably, the molar ratio of the catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to the thiolation agent mercaptoethanol in step 2 above is 1:5;

[0035] Preferably, in the above step 2, the reaction temperature is 60 DEG C, the rare gas is nitrogen, and the reaction time is 24 hours.

[0036] Preferably, in the above step 3, the molar ratio of S-ATPE to cuprous chloride is 1:1, the reaction is carried out at 80 DEG C for 12 hours, the stirring speed is 800 rpm, and the particle size of the dispersion medium nano-silica is 50 nm.

[0037] The technical effect and advantages of the fast curing process of the geopolymer-based material are as follows:

[0038] The fast hardening material prepared by the method has an initial setting time less than 30 minutes and a 1h compressive strength of 5-70 MPa.

[0039] The specific functions of the raw materials used in the application are as follows:

[0040] The slag powder, also known as GGBS, is obtained by drying and grinding blast furnace slag to a certain degree in industrial production.

[0041] The slag powder has a volcanic ash effect, filling and lubricating effect, and plays an important role in changing the brittleness, early strength, improving fluidity and durability of the geopolymer.

[0042] Metakaolin (MK) is a kind of material which is made of kaolin (chemical composition: Al2O3·2SiO2·2H2O) as raw material, and is obtained by high temperature calcination. At present, it is mainly used in rubber, paint, paint and other production. China is the earliest country to study and apply kaolin, which has been used for building materials as early as the Tang Dynasty, and metakaolin is an important raw material for the production of geopolymer. The activity of metakaolin is directly related to the internal chemical composition and the calcination temperature of kaolin. In this paper, the metakaolin is calcined, and after high temperature calcination, the powder is fine, the molecular arrangement is irregular, and it has good fire resistance, sintering, adsorption, plasticity. Its main component is silicon aluminum oxide, which is an ideal material for preparing geopolymer. Under the action of alkaline activator, it can quickly solidify and form a certain strength in a short time, which is convenient for construction.

[0043] Silica fume (SF) is a kind of powder-like silicon oxide compound collected by special dust collector device from the exhaust flue during the production of ferrosilicon and metal silicon. Under the action of additive, the application of silica fume in engineering field has been greatly popularized, especially the emergence of water reducing agent, which makes the comprehensive performance of cementing material with silica fume significantly better than ordinary cementing material. As an admixture, silica fume has extremely fine particle size, which can effectively increase the density of geopolymer and improve the bonding strength between cementing material and sand aggregate, thereby positively affecting the early and late strength and durability of geopolymer.

[0044] The silica fume used in the application is produced by Bond Industries Co., Ltd., and the average particle size is 0.1-0.15 μm, the specific surface area is 23 m 2 / g, and the surface activity is extremely strong. By comparing slag powder and cement, it is found that the fineness and specific surface area of silica fume are about 50 times that of the former and 80-100 times that of the latter. If the dosage of silica fume is too small, the performance improvement effect of the material is not significant, on the contrary, if the dosage is too large, the material bonding property is improved, the workability is poor, and dry shrinkage deformation is easy to occur. Research shows that when the dosage of silica fume is between 5% and 10%, the compressive strength can be increased by 10%-30%, the flexural strength can be increased by about 10%, and the impermeability can be increased by 5-18 times.

[0045] The activator is an important component for preparing geopolymer, and at present, the main types are sodium hydroxide, potassium hydroxide, calcium hydroxide, alkali metal hydroxides, alkaline earth metal hydroxides, halides and other salts, and composite activators such as sodium hydroxide and sodium silicate, potassium hydroxide and sodium silicate. The sodium hydroxide and sodium silicate composite activator is selected in the application. Both are white powder particles.

[0046] The sodium hydroxide (English name: Sodium hydroxide) used in the present application is of analytical purity type, the chemical formula is NaOH, the content is more than 99%, it is white powder particle, can be used alone as a stimulant for preparing geopolymer, has strong corrosive property, and is easy to deliquesce with carbon dioxide and moisture in the air. Protective measures should be taken when using to avoid injury and timely sealing to prevent deliquescence and failure.

[0047] The sodium silicate (English name: Sodium silicate) has the chemical formula Na2SiO3, and is commonly known as water glass. It is often used as a chemical analysis reagent, an adhesive and a fire retardant. The modulus n of sodium silicate determines its performance. The greater the modulus, the more difficult it is for solid sodium silicate to dissolve in water. When n = 1, it can be dissolved at room temperature. When 1.2 < n < 3, it needs to be heated to dissolve in water. When n > 3, it needs to be dissolved in steam under pressure. In this paper, sodium silicate powder with a modulus of 1.2 is selected.

[0048] The excitation principle is that the main components of slag powder, metakaolin and silica fume are silicon oxide and aluminum oxide. After sodium silicate and sodium hydroxide are made into a stimulant mixed solution and added to the powder, the silicon-oxygen bond and the aluminum-oxygen bond are broken and recombined to form an inorganic three-dimensional network structure composed of silicon-oxygen tetrahedrons and aluminum-oxygen tetrahedrons.

[0049] Currently, the modification of cement-based concrete is mainly through the addition of various fibers, steel mesh, and 3D inorganic woven net high-strength steel bars to achieve the purpose of toughening. Commonly used types of fibers include carbon fiber, steel fiber, polypropylene fiber, glass fiber, polyethylene fiber, and silicon carbide fiber. The modification of geopolymer is similar to that of ordinary concrete, except for differences in preparation process. Compared with various fibers and 3D inorganic woven nets, steel mesh has unique properties in improving the tensile strength of geopolymer and enhancing toughness. The distribution of fibers in the matrix is random and uneven, and the improvement is not significant when the fiber content is low. When the fiber content is high, the distribution of fibers in the matrix becomes more uniform as the concrete grade and fiber aspect ratio increase, and the improvement of basic mechanical properties, penetration resistance, shock resistance, and impact resistance of the material is more obvious. However, this method often has high production costs, is difficult to operate, and has other disadvantages. Since the inorganic fiber has limited improvement on the toughness of the matrix, current research mainly focuses on the use of metal fibers to improve the tensile strength, shock resistance, and impact resistance of the matrix, and the use of steel mesh to enhance the toughness, blast resistance, and tensile strength of structures and components. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0051] It should be noted that, in this document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. The terms "includes", "including", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0052] Geopolymer has become a research hotspot due to its high strength and high performance, etc. It is found that the current methods for enhancing the performance of geopolymer mainly include three aspects: adjusting the proportion of raw materials, adjusting the process maintenance and post maintenance system, and adding auxiliary admixture materials. In the adjustment of the proportion of raw materials, the amount of activator and water also plays an important role in the performance of geopolymer. This test mainly studies the influence of the proportion of slag powder and metakaolin, the amount of activator, and the water-binder ratio on the basic mechanical properties of geopolymer, so as to prepare high-performance geopolymer and provide a method for industrial production of geopolymer.

[0053] Embodiment 1

[0054] The embodiment provides a rapid curing process of a geopolymer-based material, and the specific steps include: (1) stirring and dissolving sodium hydroxide and sodium silicate in water, (2) mixing and stirring silico-aluminum material and quartz sand, mixing and stirring the final stirring material of (1) and the final stirring material of (2) with a special curing agent of the present application, and finally pouring the above-mentioned mixed stirring material into a mold.

[0055] The specific process of step (1) stirring and dissolving sodium hydroxide and sodium silicate in water is as follows: the weighed NaOH and Na2SiO3 are slowly added into a small plastic container with 70% of the total water amount, and stirred until completely dissolved, and the stirring speed is 100 rpm.

[0056] The step (2) of mixing and stirring the siliceous and aluminous material with quartz sand is specifically as follows: the weighed all graded quartz sand is sequentially poured into a 30L stirrer and stirred for 3 minutes, the siliceous and aluminous material is continuously added, and the powder and quartz sand are mixed uniformly after stirring for 3 minutes, and the stirring speed is 100-200 rpm;

[0057] The step of mixing and stirring (1) the final stirring material and (2) the final stirring material with the special curing agent of the application is specifically as follows: (1) the final stirring material and (2) the final stirring material with the special curing agent of the application are added into a stirrer, covered and started to stir for 3 minutes, the remaining 20% water cleaning mixed liquid container is continuously added into the stirrer, and the stirring is stopped after fully stirring for 5 minutes, and the stirring speed is 100 rpm;

[0058] The step of pouring the mixed and stirred material into a mold is specifically as follows: the slurry is poured and cured at room temperature, and the pouring is layered and poured into the mold, and the pouring is vibrated and compacted when the pouring reaches one third of the height of the mold.

[0059] The quality of each material in Example 1 is added as follows:

[0060] 1. Siliceous and aluminous material: 60 parts of slag powder (GGBS), 60 parts of metakaolin (MK), and 10 parts of silica fume (SF);

[0061] 2. Activator: 36 parts of sodium hydroxide (NaOH) and 22 parts of sodium silicate (Na2SiO3) with a modulus of 1.2;

[0062] 3. Graded quartz sand: the mass ratio of medium sand to fine sand is 6:3, and the total amount is 26 parts;

[0063] 4. Water-binder ratio (W / B): 0.34;

[0064] 5. The special curing agent of the application: 4 parts.

[0065] The dosage ratio (MK / GGBS) of the metakaolin and the slag powder is 1.0;

[0066] The preparation method of the special curing agent of the application is as follows:

[0067] Step 1. Synthesis of polyether amine matrix: a proper amount of polyoxyethylene glycol with a molar ratio of 1:1 is mixed with diethylenetriamine and added into 50ml of DMF, under the action of a proper amount of catalyst p-toluenesulfonic acid, at a negative pressure of 0.1 MPa and a temperature of 120℃, and reacted for 8 hours to obtain the polyether amine matrix, which is abbreviated as ATPE;

[0068] Step 2. Thiolation modification, that is, introducing -SH group: an appropriate amount of thiolating agent mercaptoethanol and ATPE obtained in step 1 above are added to 30 ml of anhydrous tetrahydrofuran, and then, under the action of 0.32 g of catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), at 60°C, under the protection of nitrogen, the reaction is carried out for 24 hours to obtain S-ATPE;

[0069] Step 3. Dynamic Cu-S network construction: an appropriate amount of S-ATPE obtained in step 2 above and an appropriate amount of cuprous chloride are mixed and added to 40 ml of solvent acetonitrile, under the dispersion of dispersion medium nanosilica aerogel, stirring at 80°C for 12 hours at a stirring speed of 600 rpm, and finally, the special curing agent Cu-S-ATPE of the application is obtained.

[0070] The alkali-binder ratio is 0.45;

[0071] Example 2

[0072] The only difference between example 2 and example 1 is that in example 2, the dosage ratio of metakaolin to slag powder (MK / GGBS) is 0.5.

[0073] Example 3

[0074] The only difference between example 3 and example 1 is that in example 3, the dosage ratio of metakaolin to slag powder (MK / GGBS) is 1.5.

[0075] Example 4

[0076] The only difference between example 4 and example 1 is that in example 4, the alkali-binder ratio is 0.4.

[0077] Example 5

[0078] The only difference between example 5 and example 1 is that in example 5, the alkali-binder ratio is 0.35.

[0079] Example 6

[0080] The difference between example 6 and example 1 is that in example 6, the water-binder ratio is 0.38.

[0081] Example 7

[0082] The difference between example 7 and example 1 is that in example 7, the water-binder ratio is 0.42.

[0083] Comparative example 1

[0084] The difference between comparative example 1 and example 1 is that in comparative example 1, the special modified curing agent of the application is not added.

[0085] Comparative Example 2

[0086] Prior art, CN106946513B, a room temperature curable polymer material and its application.

[0087] Test Example

[0088] Test Example 1: Uniaxial Compression Test

[0089] The geopolymer-based materials prepared in the above examples and comparative examples were cured for 24 hours at room temperature after coating the test blocks, and then demoulded after 24 hours. The test blocks without obvious defects (corner breakage, cracks, holes) were selected for natural curing at room temperature for 28 days, and the strength was tested.

[0090] The compression test pieces in this test were cubic test pieces with a size of 100mm x 100mm x 100mm. According to the relevant provisions of the Standard for Testing Methods of Mechanical Properties of Ordinary Concrete (GB / T 50081-2002), a YAW-3000 type microcomputer controlled electro-hydraulic servo pressure testing machine of Tianjin City Construction University Structure Test Room was used to test the compressive strength of the cubic test blocks. The two relatively smooth sides of the test block were selected as the loading end and the base contact surface, and were placed in the center of the loading end. Two displacement meters were placed along the longitudinal position of the test piece to test the deformation data of the test piece along the force direction during the experiment. The loading method used was first force control to reach a certain force value, maintaining for a period of time to make the upper and lower surfaces of the test piece and the loading end and the bottom surface platform fully contact, then force control loading to a certain value, and finally displacement control loading until the test piece was destroyed and the test was completed.

[0091] The specific loading system was as follows: 1. First, force control loading was used to load to 50 kn at a loading rate of 4 kn / s, and maintained for 20 s; 2. Then, force control loading was used to load to 400 kn at a loading rate of 5 kn / s; 3. Finally, loading was carried out at a loading rate of 0.5 mm / min until the test piece was destroyed and the test was completed.

[0092] The compressive strength of the geopolymer was calculated according to the following formula:

[0093]

[0094] In the above formula, fcc is the compressive strength of the geopolymer cubic test piece (MPa); F is the failure load of the test piece (N); and A is the pressure bearing of the test piece.

[0095] Area (mm2); the compressive strength was calculated to 0.1 MPa.

[0096] Table 1: Uniaxial Compression Test Results

[0097]

[0098] From the above Table 1, it can be seen that Example 4 is the best embodiment. From Comparative Examples 1-3, it can be seen that when the alkali-binder ratio is 0.45, the uniaxial compressive strength of the geopolymer-based material prepared is best when the ratio of metakaolin to ground granulated blast furnace slag (MK / GGBS) is 1.0, and the uniaxial compressive strength is affected by the ratio of metakaolin to ground granulated blast furnace slag (MK / GGBS) being too high or too low. In comparison, Example 1 and Examples 4 and 5, when the ratio of metakaolin to ground granulated blast furnace slag (MK / GGBS) is fixed at 1.0, changing the alkali-binder ratio also affects the uniaxial compressive strength, and when the alkali-binder ratio is 4.0, the uniaxial compressive strength can reach 89 MPa, and the uniaxial compressive strength is reduced when the alkali-binder ratio is too high or too low around 4.0. In comparison, Example 1, Example 6, and Example 7, when the water-binder ratio is 0.38, the uniaxial compressive strength of the geopolymer-based material prepared is better;

[0099] In comparison, Example 1, Example 4, and Comparative Example 1, it can be seen that the curing agent specially prepared in the present application can enhance the uniaxial compressive strength of the geopolymer-based material. The uniaxial compressive strength of Comparative Example 1 even exceeds the best uniaxial compressive strength of Example 4, indicating that the curing agent prepared in the present application not only allows the geopolymer to be rapidly cured, but also can even improve the uniaxial compressive strength. The possible reasons are as follows: 1. Raw material ratio and silicon-aluminum ratio control: MK / GGBS ratio optimization: when MK / GGBS = 1.0 (Example 1), the silicon-aluminum ratio (SiO2 / Al2O3) reaches a relatively optimal theoretical value, at which time the active components (amorphous SiO2 and Al(OH)4 - ) of metakaolin (SiO2 source) and ground granulated blast furnace slag (Al2O3 source) are synchronously released, forming a continuous [Si-O-Al-O] three-dimensional network structure. In Example 2 (MK / GGBS = 0.5), Al2O3 is excessive, causing unreacted Al(OH)4 - to crystallize and form microcrack defects; in Example 3 (MK / GGBS = 1.5), SiO2 is excessive, causing the gel network to have "Si-O-Si" over-connection, reducing the toughness of the material; 2. Alkali-binder ratio dynamic balance: when the alkali-binder ratio is 0.45 (Example 1), the acid-alkalinity value exactly meets the critical pH value of the polycondensation reaction of the geopolymer, at which time the dissolution-polymerization of the aluminosilicates reaches a dynamic balance. In Example 4 (alkali-binder ratio = 0.4), the acid-alkalinity value is slightly reduced, causing incomplete dissolution of amorphous SiO2, but the excessive activator promotes the pozzolanic reaction of the nano-silica ash, and the final strength is reversed. In Example 5 (alkali-binder ratio = 0.35), the acid-alkalinity value is too low, causing part of the Al(OH)4 -Incomplete polymerization, forming a loose structure; 3, dynamic chemical bond mechanism: Cu-S-ATPE network construction: the dynamic Cu-S bond in the specially prepared curing agent forms a reversible coordination network at room temperature, which enhances the material density through "molecular stitching" at the initial stage of curing, and the dynamic bond reversibly breaks and recombines at high temperature, giving the material self-repairing ability; 4, the mechanism of the specially prepared curing agent: 1) chemical bond competition mechanism: -SH group participates in the reaction: the -SH group in the curing agent competes with Si-O in the aluminosilicate, when the addition amount is 5 parts, a small amount of -SH participates in the formation of Si-O-S bond, and the remaining more -SH forms unreacted -S-S- bond, these intermediates still have flowability at 1 hour test, which reduces the test strength. In the comparative example 1, the pure geopolymer system optimizes the ratio of the excitation agent to make the Si-O-Si bond formation rate higher, and form a more stable chemical bond network; 2) nano confinement effect: nano silica aerogel dispersion: the nano silica aerogel added in the preparation of the curing agent forms a three-dimensional confined space, which promotes the directional formation of Cu-S bond and improves the uniformity of the material compared with traditional stirring mixing; 3) multi-scale synergistic reinforcement: micron-nanometer double-scale structure: the Cu-S nanoparticles in the curing agent form a "pearl chain" structure with the geopolymer gel network to inhibit crack propagation through Zener pinning effect, while the micron-sized quartz sand provides skeleton support. 2+ The concentration gradient is controlled within 5nm, which promotes the directional formation of Cu-S bond and improves the uniformity of the material compared with traditional stirring mixing; 3) multi-scale synergistic reinforcement: micron-nanometer double-scale structure: the Cu-S nanoparticles in the curing agent form a "pearl chain" structure with the geopolymer gel network to inhibit crack propagation through Zener pinning effect, while the micron-sized quartz sand provides skeleton support.

[0100] It can be known from comparative examples 1-5 and comparative examples 1-2 that the uniaxial compressive strength of the geopolymer-based material prepared by the present application is obviously better than that of the prior art.

[0101] Test item 2: mechanical property test (flexural and compressive strength test)

[0102] According to the related content of the specification, the geopolymer-based material prepared in each of the above examples and comparative examples is cured for 24 hours at room temperature after coating the test block, and the test block without obvious defects (break angle, crack, hole) is selected for natural curing for 28 days at room temperature, and the strength is tested.

[0103] According to the requirements of GB2419-2002 "Cement mortar fluidity determination method", the influence of different water consumption on the compressive and flexural mechanical properties and workability (this test mainly tests the spread) of geopolymer is tested, and the optimal ratio of high-performance geopolymer is determined;

[0104] Due to the equipment problem and the particularity of the test block production, the tensile mechanical properties of the geopolymer-based material are analyzed from the perspective of the flexural test in this test. According to the relevant provisions of the Standard for Test Methods of Mechanical Properties of Ordinary Concrete (GB / T 50081-2002), the same testing machine as in the previous compressive test is used, the size of the flexural test specimen is 100mmx100mmx400mm, the four-point flexural test is adopted, two displacement gauges are arranged along the long axis of the specimen in the middle and on both sides of the pressure testing machine pressure head, the vertical displacement of the center of the upper surface of the specimen during the test is tested, and the real vertical displacement and stress are calculated through the collected experimental data in the later stage. The loading mode is to first control the force to reach a certain force value, keep it for a period of time to make the loading end fully contact with the specimen, and use this period of time to observe whether the specimen and the loading device are on the same straight line; then set the displacement control to continuously and uniformly load until the specimen is destroyed and the test is ended. The specific loading system is as follows: 1. First, load with force control, load at a rate of 0.5kn / s to 4kn, and keep for 15s; 2. Change to displacement control loading, load uniformly at a rate of 0.02mm / s until the specimen is destroyed, and the test is ended.

[0105] The formula for calculating the flexural strength of geopolymer is as follows:

[0106]

[0107] In the above formula, f t ---Flexural strength of geopolymer (MPa); F --- Load at failure (N); l --- Span between supports (mm); h --- Height of specimen (mm); b --- Width of specimen (mm); Flexural strength is calculated to 0.1MPa.

[0108] Table 2 Flexural and compressive strength test results

[0109] water binder ratio flexural strength / MPa compressive strength / MPa example 1 0.34 32 95.2 example 2 0.34 31 90.1 example 3 0.34 29 93.4 example 4 0.34 44 99.8 example 5 0.34 30 88.3 example 6 0.38 34 110.1 example 7 0.42 31 86.3 comparative example 1 0.34 35 78.3 comparative example 2 -- 30 43.5

[0110] From Table 2 above, it can be seen that, in Comparative Examples 1-7 and Comparative Examples 1-2, when the water-binder ratio is 0.38, the flexural strength is the maximum, which is 44 MPa, and the compressive strength can also reach 110.1 MPa; the addition of the curing agent of the present application is very great for the flexural and compressive strength improvement of the geopolymer-based material. The possible reasons are as follows: 1, the influence mechanism of the water-binder ratio on the mechanical properties: 1) the synergistic effect of the optimal water-binder ratio: microstructure optimization, when the water-binder ratio is the optimal ratio, the free water content of the system just meets the following dual requirements: a. reaction kinetics requirement: providing sufficient liquid phase to promote the dissolution-polymerization reaction of NaOH / Na2SiO3 on GGBS / MK; b. interface transition zone (ITZ) densification: after the evaporation of excess water, nano-scale pores are formed, and through the nano-SiO2 self-filling effect induced by capillary tension, the ITZ thickness is reduced; 2) strength attenuation mechanism: high water-binder ratio defect: excess free water leads to: delay of secondary hydration reaction of silica fume (SF), formation of micro-crack network at the quartz sand-cementitious material interface, and reduction of alkali activator concentration gradient; 3) low water-binder ratio limitation: insufficient powder flowability, and "dry spot" defect in local areas; 2, the enhancement mechanism of the specially prepared curing agent (Cu-S-ATPE): 1) dynamic crosslinking network construction: chemical bond synergistic effect: Cu-S coordination bond and Si-O-Al network form a three-dimensional interpenetrating structure, and thiol group (-SH) and ATPE chain segment form a dynamic reversible bond; 2) microstructure performance improvement: interface strengthening effect: nano-SiO2 aerogel fills the pores, Cu 2+ induced local electric field effect promotes siloxane bond rearrangement; 3, macroscopic performance breakthrough: 1) flexural strength improvement: crack propagation resistance is improved, and stress-induced phase transition (SIC) ability is enhanced, so that the compressive strength jumps.

[0111] In summary: by changing the material ratio, activator addition amount, and water amount, and adding the specially prepared curing agent of the present application, a high-performance geopolymer with high compressive strength and good toughness can be prepared.

[0112] Test item 3: geopolymer-based material rapid curing performance test

[0113] The penetration resistance method is used for measurement.

[0114] Principle: the curing process is judged by measuring the change of the penetration resistance of the slurry to the probe;

[0115] The geopolymer-based materials in the above examples and comparative examples are divided into multiple test molds, and placed in a constant temperature and humidity environment (such as 20℃, RH≥95%); every fixed time, the test mold is taken out, and the resistance is tested by using a penetration resistance instrument (probe diameter 3.5mm); the resistance-time curve is drawn, the initial setting corresponds to a resistance of 3.5 MPa, and the final setting corresponds to a resistance of 28 MPa.

[0116] Table 3: geopolymer-based material rapid curing performance test results

[0117] initial setting time / min example 1 20 example 2 23 example 3 22 example 4 8 example 5 17 example 6 22 example 7 26 comparative example 1 27 comparative example 2 60

[0118] From the analysis of Table 3 above, it can be seen that by optimizing the raw material ratio, the rapid curing of the geopolymer-based material prepared by the present application can be accelerated, but from the comparison between Comparative Example 4 and Comparative Examples 1 and 2, it can be seen that on the basis of the optimized formula, the addition of the special curing agent of the present application can greatly reduce the curing time, and the curing time is significantly less than the curing time of the existing geopolymer-based material. The possible reason is that: 1. Dynamic Cu-S molecular crosslinking mechanism: the transient nucleation effect of dynamic coordination bond, the Cu 2+ -SH group in Cu-S-ATPE can trigger rapid crosslinking reaction at room temperature. Cu-S-ATPE can form a large number of dynamic crosslinking nodes in the system, so that the nucleation time of the geopolymer gel network is significantly shortened by several times; 2. Stress-induced recombination characteristics of dynamic bond: dynamic Cu-S bond can break and recombine, so that the internal defects of the slurry are quickly healed under mechanical energy input, forming a dense three-dimensional network structure. 3. Synergistic acceleration of silicate dissolution-polymerization: 1) Interfacial charge regulation: the quaternary ammonium salt groups in Cu-S-ATPE form a double electric layer by electrostatic adsorption on the surface of the slag powder, which greatly increases the absolute value of the Zeta potential of the silicate particles, promotes the electrostatic repulsion between the particles, and accelerates the dissolution process; 2) Hydroxyl bridging catalysis effect: the primary amine groups in the S-ATPE segment activate the Al-OH and Si-OH groups through hydrogen bonding, which greatly reduces the activation energy of the geopolymer gel. Computational chemistry (DFT) shows that Cu-S-ATPE significantly reduces the energy barrier of Al-O-Si bond formation.

[0119] Those skilled in the art can appreciate that the modules and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented in electronic hardware or a combination of computer software and electronic hardware, and the functions are implemented in hardware or software, depending on the specific application and design constraints of the technical solution. Professionals can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0120] In addition, each functional module in each embodiment of the present application can be integrated into one processing module, or each module can exist physically alone, or two or more modules can be integrated into one module.

[0121] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, and all of them should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0122] Finally, the above merely provides the preferred embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A process for the rapid curing of a geopolymer-based material, characterised in that, It comprises the following steps: (1) stirring and dissolving sodium hydroxide and sodium silicate with water, (2) mixing and stirring siliceous and aluminous material with quartz sand, mixing and stirring the final stirring material of (1) and the final stirring material of (2) with a special curing agent, and finally pouring the stirring material into a mold; The specific process of stirring and dissolving sodium hydroxide and sodium silicate with water in step (1) is as follows: slowly add weighed NaOH and Na2SiO3 into a small plastic container with 70% of the total water amount, and stir until completely dissolved, with a stirring speed of 100-200 rpm; The specific process of mixing and stirring siliceous and aluminous material with quartz sand in step (2) is as follows: pour all the graded quartz sand into a 20-30 L stirring machine, stir for 1-3 min, then add the siliceous and aluminous material, and stir for 1-3 min until the powder and quartz sand are evenly mixed, with a stirring speed of 100-200 rpm; The specific process of mixing and stirring the final stirring material of (1) and the final stirring material of (2) with a special curing agent is as follows: add the final stirring material of (1) and the final stirring material of (2) and the special curing agent into a stirring machine, cover and start stirring for 1-3 min, then add the remaining 20% of the water used to clean the mixing liquid container into the stirring machine, cover and fully stir for 5 min, and then stop stirring, with a stirring speed of 100-200 rpm; The specific process of pouring the mixed stirring material into a mold is as follows: pour the slurry and let it cure at room temperature, pour it into the mold in layers, and vibrate it while pouring after it reaches one-third of the height of the mold; the initial setting time is less than 30 min, and the 1h compressive strength reaches 5-70 MPa; The addition amount of the special curing agent is 1-5% of the addition amount of the siliceous and aluminous material, and the water-binder ratio is 0.34-0.42; The preparation method of the special curing agent is as follows: Step 1. Synthesis of polyether amine matrix: mix polyoxyethylene glycol and diethylene triamine with a molar ratio of (1-2):(1-3) into an appropriate amount of DMF, add an appropriate amount of catalyst p-toluenesulfonic acid, and react under the conditions of negative pressure 0.1 MPa and temperature 110-120℃ for 7-8 hours to obtain the polyether amine matrix, which is referred to as ATPE; Step 2. Thiol modification, that is, introducing -SH groups: add an appropriate amount of thiolating agent mercaptoethanol and the ATPE obtained in step 1 into an appropriate amount of anhydrous tetrahydrofuran, then add a catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and react under the protection of rare gas at 50-60℃ for 22-24 hours to obtain S-ATPE; Step 3. Dynamic Cu-S network construction: mix an appropriate amount of S-ATPE obtained in step 2 with an appropriate amount of cuprous chloride into an appropriate amount of solvent acetonitrile, disperse under the dispersion of nano-silica aerogel as a dispersion medium, and stir at 75-80℃ for 10-12 hours with a stirring speed of 600-800 rpm to finally obtain the special curing agent Cu-S-ATPE.

2. A process for rapid curing of a geopolymer-based material according to claim 1, characterised in that: The silico-aluminate material is slag powder, metakaolin, silica fume, the ratio of metakaolin and slag powder is (0.5-1.5):1, the average particle size of silica fume is 0.1-0.15 µm, and the specific surface area is 23 m 2 / g.

3. A process for rapid curing of a geopolymer-based material according to claim 1, characterized in that: The sodium hydroxide is added in an amount of 15-20% of the siliceous and aluminous material, and the sodium silicate with a modulus of 1.2 is added in an amount of 10-30% of the siliceous and aluminous material, and the total amount of the two, that is, the total amount of the activator and the total amount of the gel material, is in a ratio of 0.3-0.

5.

4. A process for rapid curing of a geopolymer-based material according to claim 1, characterized in that: The graded quartz sand: the mass ratio of medium sand to fine sand (6-8): (2-4), the total amount is 20-30% of the siliceous and aluminous material, the particle size distribution of the graded quartz sand is 0.15-0.6 mm, and the bulk density is ≥1.6 g / cm³.

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