Fibrous inorganic toughened composite and method for making same

Abstract

The present application belongs to the technical field of building material additive, and discloses a fibrous inorganic toughening composite material for enhancing the toughness of cement-based material and a preparation method thereof. The fibrous inorganic toughening composite material is a polycrystalline material composed of calcium silicate fibers and calcium oxide, silicon dioxide and metal oxide attached to the surface of the calcium silicate fibers. The fibrous inorganic toughening composite material mainly contains calcium silicate substances, which not only exhibits an internal toughening mechanism by inducing hydration products through chemical components, but also exhibits an external toughening mechanism by existing in the form of a "rivet" in the cement hydration products, thereby achieving the crack resistance of cement-based materials. The fibrous inorganic toughening composite material has good compatibility with the components in the cement-based material, and all the components are inorganic components without organic substances, so that the application of the fibrous inorganic toughening composite material will not adversely affect the cement hydration.

Description

Technical Field

[0001] This invention belongs to the field of building material additives technology, specifically, it relates to a fibrous inorganic toughening composite material for enhancing the toughness of cement-based materials, and its preparation method. Background Technology

[0002] Brittleness and poor toughness are among the most prominent mechanical characteristics of concrete. Due to concrete's extremely low ultimate tensile strength, the tensile stress that steel bars can withstand when concrete cracks is less than 50 MPa, an order of magnitude lower than the tensile strength of high-strength steel bars. This falls far short of their intended performance and is incompatible with the rapid development of my country's steel industry. Furthermore, major engineering projects in my country span east to west and north to south, often facing harsher environments with high salt content, high humidity, and high UV exposure. Once concrete structures crack, their durability is significantly reduced, maintenance costs increase, and a heavy burden is placed on the national economy. Therefore, from both a structural and durability perspective, higher requirements are placed on the toughness of concrete itself.

[0003] To address the shortcomings of poor toughness and high brittleness in concrete, scholars both domestically and internationally have conducted research focusing on fiber toughening, organic modification, and nanomaterial regulation. Incorporating a certain amount of fiber can effectively improve the brittleness of concrete. In recent years, scholars have conducted extensive research on the development of concrete toughness, focusing on fiber type, thickness, dosage, cross-sectional shape, aspect ratio, distribution, and surface modification. Currently, steel fibers, polypropylene fibers, and polyvinyl alcohol fibers are widely used. Fiber toughening acts before and after concrete cracking. Before cracking, fibers can transfer stress in the concrete matrix, increasing the strength and toughness of fiber-reinforced concrete; after cracking, fibers absorb a large amount of energy used for crack propagation through bonding force with the concrete matrix, frictional force generated by relative displacement, and fiber deformation, increasing the fracture energy of fiber-reinforced concrete, inhibiting crack development, and thus improving crack resistance and toughness. High-toughness cement-based materials designed based on micromechanics and fracture mechanics can increase tensile strength by 9%–50% (depending on fiber type and dosage), flexural strength by 196%, reduce brittle fracture characteristics, and enhance ductility and toughness during fracture compared to ordinary concrete.

[0004] Polymers are used to improve the brittleness of concrete materials due to their excellent toughness. Commonly used polymers include ethylene-vinyl acetate copolymer emulsions, styrene-butadiene copolymer emulsions, water-soluble methylcellulose, polyvinyl alcohol, polyacrylamide, epoxy resins, and unsaturated polyester resins. However, polymer toughening materials have disadvantages such as high price, large dosage, poor weather resistance, and easy decomposition at high temperatures, which limits their application.

[0005] The regulation of toughness in cement-based materials using nanomaterials has been a research hotspot in recent years. Nanomaterials that most significantly enhance the toughness of cement-based materials include nano-silica, graphene oxide, and carbon nanotubes. Studies have shown that nanomaterials can improve the interfacial transition zone and increase the adhesion between aggregates and the cement mortar matrix. Nanoparticles hinder the propagation of microcracks and form a spatial interlocking effect between slip surfaces, thereby improving the toughness of cement-based materials. However, due to their extremely high specific surface area and surface energy, nanoparticles are prone to agglomeration when directly applied to cement-based materials, greatly limiting the full potential of their functions. Furthermore, their high economic cost also hinders their widespread engineering applications.

[0006] In summary, while methods such as fiber, polymer, and nanomaterial modification can improve the toughness of cement concrete to some extent, these methods are still external toughening methods and do not fundamentally change the random distribution of hydration products in cement-based materials. This fundamentally determines the limitations of these modification methods in improving the toughness of cement concrete.

[0007] Although there are studies on improving toughening mechanisms, they rely on polymer dispersants for preparation, which can lead to problems where these organic solvents have an adverse effect on the hydration of cement-based materials during application.

[0008] Therefore, there is an urgent need to study a toughening material that has excellent toughening effect and will not have an adverse effect on the hydration of cement-based materials when applied. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of the prior art by providing an inorganic composite material for enhancing the toughness of cement-based materials. When applied to cement-based materials, this material not only imparts better toughness, durability, and mechanical properties to the cement-based materials, but its components also do not adversely affect the hydration of the cement-based materials.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A fibrous inorganic toughened composite material is a polycrystalline material composed of calcium silicate fibers and calcium oxide, silicon dioxide, and metal oxides attached to the surface of the calcium silicate fibers; wherein the content of calcium silicate fibers is 35wt% to 55wt%, the content of calcium oxide is 15wt% to 22wt%, the content of silicon dioxide is 23wt% to 45wt%, and the content of metal oxides is less than 5wt%.

[0012] The inorganic toughened composite material is fibrous in shape, with a length of 5μm to 10μm and a diameter of 300nm to 600nm.

[0013] Another objective of this invention is to provide a method for preparing the above-mentioned fibrous inorganic toughened composite material, which includes the following steps:

[0014] S1. The mixture of calcium silicate, nano-silica and metal oxide is calcined at 1200℃~1400℃ to obtain the calcined product;

[0015] S2. Mix the calcined material with silicon dioxide and alkaline solution, and then introduce acidic gas into it until saturation to obtain a saturated gas solution;

[0016] S3. The saturated gas solution is subjected to a hydrothermal reaction at 120℃~180℃ to obtain a fibrous inorganic toughened composite material.

[0017] The metal oxide in step S1 can be selected from at least one of calcium oxide, aluminum oxide, and iron oxide, and its addition amount accounts for no more than 5% of the total mass of the mixture. Using metal oxides as raw materials can play a morphology-defining role. During the reaction, these metal oxides can adsorb onto the surface of calcium silicate, thereby affecting the morphology of calcium silicate during nucleation and promoting the formation of a fibrous morphology. These metal oxides also make the product polycrystalline. Furthermore, the presence of these metal oxides ensures that the fibrous inorganic toughened composite material, when applied to cement-based materials, can improve the surface roughness of cement.

[0018] The high-temperature calcination operation in step S1 allows the elements to migrate in the solid phase between the metal oxide and other inorganic components.

[0019] In the above mixture, the particle size of calcium silicate is 50 nm to 10 μm, and the particle size of nano-silica is 20 nm to 100 nm; in the metal oxides, the particle size of calcium oxide is 5 μm to 50 μm, and the particle size of aluminum oxide and iron oxide is 10 μm to 50 μm.

[0020] The calcium silicate mentioned above can be commercially available calcium silicate powder or nano-calcium silicate prepared by reacting calcium chloride with sodium silicate.

[0021] The high-temperature calcination in step S1 can be achieved using a muffle furnace with programmed temperature control, i.e., a gradient temperature increase starting from room temperature. This gradient temperature increase can have 2-3 steps, with a total time of 5-8 hours. The final reaction temperature should be controlled between 1200℃ and 1400℃, preferably calcined at this temperature for 1-3 hours. After calcination, allow it to cool naturally to obtain the calcined product.

[0022] In step S2, the alkaline solution ensures more complete deposition of calcium silicate. The choice of alkaline solution is not particularly limited; it can be a sodium hydroxide solution, a calcium hydroxide solution, or a mixture of both. The concentration of the sodium hydroxide solution can be 0.1 mol / L to 0.5 mol / L, and the calcium hydroxide solution can be a saturated calcium hydroxide solution.

[0023] By introducing an acidic gas until saturation, substances in the solid phase can be slowly dissolved. The acidic gas can be CO2, and the saturation time is generally controlled to be about 5 to 10 minutes.

[0024] Preferably, in step S2, before mixing the calcined material with silica and alkali solution, it is first ground to a particle size of 1 μm to 50 μm. Smaller particle size of the calcined material allows for more complete subsequent reactions.

[0025] Generally, in step S3, the hydrothermal reaction product can be cleaned, dried, and ground to obtain the above-mentioned fibrous inorganic toughened composite material.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) The fibrous inorganic toughening composite material provided by this invention is mainly composed of calcium silicate. When applied to cement-based materials, the presence of elements such as silicon and calcium can induce the formation of cement hydration products, and these elements can serve as nucleation sites, allowing the Ca dissolved in the cement to be absorbed. 2+ SiO4 2- It tends to deposit on its surface, allowing the fibrous morphology to grow further, altering the hydration path of cement-based materials, thereby changing the overall internal structure of cement-based materials (changing the morphology of cement hydration products), exhibiting an internal toughening mechanism; on the other hand, its fibrous morphology can exist in the cement hydration products in the form of "rivets". Combined with its high strength characteristics, it can not only effectively prevent the generation of cracks in the matrix, but also effectively release stress when cracks are generated and develop to that point, slowing down crack extension, thus exhibiting an external toughening mechanism.

[0028] 2) The above-mentioned fibrous inorganic toughened composite material provided by the present invention has good compatibility with cement-based materials when it is applied to cement-based materials, based on its components being similar to those in cement-based materials; and since it is composed entirely of inorganic components and contains no organic matter, its application will not have an adverse effect on cement hydration.

[0029] 3) The above-mentioned fibrous inorganic toughened composite material provided by the present invention adds nano-silica into the system in the form of calcination during the preparation process, which serves as a nucleation site for the growth of fibrous products. This not only utilizes the advantage that nanoparticles can enhance the mechanical properties of cement-based materials, but also solves the agglomeration problem caused by the direct addition and application to cement-based materials in the prior art.

[0030] 4) The preparation method of the above-mentioned fibrous inorganic toughened composite material provided by the present invention has a wide range of raw material sources, all of which are inorganic components, making it safe and environmentally friendly, and the preparation process is simple and easy to control. Attached Figure Description

[0031] Figure 1 This is a microscopic morphology diagram of the fibrous inorganic toughened composite material according to Example 8 of the present invention;

[0032] Figure 2 and Figure 3 These are nanostructure diagrams of the fibrous component in the fibrous inorganic toughened composite material according to Example 8 of the present invention at different multiples after electron beam irradiation;

[0033] Figure 4 This is a SEM image of the surface of a cement specimen obtained by applying the fibrous inorganic toughened composite material according to Example 8 of the present invention;

[0034] Figure 5 This is a SEM image of the surface of the reference cement test block. Detailed Implementation

[0035] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. However, these embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0036] Example 1

[0037] The fibrous inorganic toughened composite material provided in this embodiment is prepared using the following method:

[0038] (1) The premixed mixture A (55wt% calcium silicate, 15wt% calcium oxide, 25wt% nano-silica, and 5wt% alumina) was placed in a crucible and calcined in a muffle furnace. The calcination was carried out using a programmed temperature control method: 50℃-30min-100℃-30min-100℃-90min-700℃-110min-1200℃-30min-1200℃-60min-1300℃. After reaching 1300℃, the mixture was calcined for 1 hour, and then allowed to cool naturally to obtain the calcined product.

[0039] The particle sizes of each component in the above mixture A are as follows: calcium silicate has a particle size of 50 nm to 10 μm, nano silica has a particle size of 20 nm to 100 nm, calcium oxide has a particle size of 5 μm to 50 μm, and aluminum oxide has a particle size of 10 μm to 50 μm.

[0040] (2) The calcined material was ground in a ball mill for 1 hour. The powder was then manually ground in an agate mortar for 0.5 hours and then sieved through a 400-mesh sieve to obtain a small-particle mixture B (particle size of 1μm to 50μm).

[0041] (3) The refined mixture B (3.6 parts) was mixed with silicon dioxide (1 part) and 100 parts of 0.1 mol / L sodium hydroxide. At the same time, CO2 gas was introduced into the solution for 10 min to obtain saturated gas solution C.

[0042] (4) The saturated gas solution C was placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 120°C for 12 hours. After cooling, product D was obtained.

[0043] (5) The product D is cleaned, dried and ground to obtain the fibrous inorganic toughened composite material S01.

[0044] Example 2

[0045] (1) The premixed mixture A (50wt% calcium silicate, 22wt% calcium oxide, 24wt% nano-silica, 2wt% alumina, and 2wt% iron oxide) was placed in a crucible and calcined in a muffle furnace. The temperature was controlled by a program: 50℃-30min-100℃-30min-100℃-90min-700℃-110min-1200℃-30min-1200℃-60min-1300℃. After reaching 1300℃, the mixture was calcined for 2 hours, followed by natural cooling to obtain the calcined product.

[0046] The particle sizes of each component in the above mixture A are as follows: calcium silicate has a particle size of 50 nm to 10 μm, nano silica has a particle size of 20 nm to 100 nm, calcium oxide has a particle size of 5 μm to 50 μm, and aluminum oxide and iron oxide both have a particle size of 10 μm to 50 μm.

[0047] (2) The calcined material was ground in a ball mill for 1 hour. The powder was then manually ground in an agate mortar for 0.5 hours and then sieved through a 400-mesh sieve to obtain a small-particle mixture B (particle size of 1μm to 50μm).

[0048] (3) The refined mixture B (3.6 parts) was mixed with silicon dioxide (1 part) and 100 parts of 0.3 mol / L sodium hydroxide. At the same time, CO2 gas was introduced into the solution for 10 min to obtain saturated gas solution C.

[0049] (4) The saturated gas solution C was placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 120°C for 12 hours. After cooling, product D was obtained.

[0050] (5) The product D is cleaned, dried and ground to obtain the fibrous inorganic toughened nanomaterial SO2.

[0051] Example 3

[0052] (1) The premixed mixture A (50wt% calcium silicate, 24wt% calcium oxide, 24wt% nano-silica, and 2wt% alumina) was placed in a crucible and calcined in a muffle furnace. The temperature was controlled by a program: 50℃-30min-100℃-30min-100℃-90min-700℃-110min-1200℃-30min-1200℃. After reaching 1200℃, the mixture was calcined for 3 hours, followed by natural cooling to obtain the calcined product.

[0053] The particle sizes of each component in the above mixture A are as follows: calcium silicate has a particle size of 50 nm to 10 μm, nano silica has a particle size of 20 nm to 100 nm, calcium oxide has a particle size of 5 μm to 50 μm, and aluminum oxide has a particle size of 10 μm to 50 μm.

[0054] (2) The calcined material was ground in a ball mill for 1 hour. The powder was then manually ground in an agate mortar for 0.5 hours and then sieved through a 400-mesh sieve to obtain a small-particle mixture B (particle size of 1μm to 50μm).

[0055] (3) The refined mixture B (3.6 parts) was mixed with silicon dioxide (1 part) and 100 parts of 0.5 mol / L sodium hydroxide. At the same time, CO2 gas was introduced into the solution for 10 min to obtain saturated gas solution C.

[0056] (4) The saturated gas solution C was placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 120°C for 12 hours. After cooling, product D was obtained.

[0057] (5) The product D is cleaned, dried and ground to obtain the fibrous inorganic toughened nanomaterial SO3.

[0058] Example 4

[0059] (1) The premixed mixture A (50wt% calcium silicate, 24wt% calcium oxide, 24wt% nano-silica, and 2wt% alumina) was placed in a crucible and calcined in a muffle furnace. The calcination was carried out using a programmed temperature control method: 50℃-30min-100℃-30min-100℃-90min-700℃-110min-1200℃-30min-1200℃-60min-1400℃. After calcining at 1400℃ for 2 hours, the mixture was allowed to cool naturally to obtain the calcined product.

[0060] The particle sizes of each component in the above mixture A are as follows: calcium silicate has a particle size of 50 nm to 10 μm, nano silica has a particle size of 20 nm to 100 nm, calcium oxide has a particle size of 5 μm to 50 μm, and aluminum oxide has a particle size of 10 μm to 50 μm.

[0061] (2) The calcined material was ground in a ball mill for 1 hour. The powder was then manually ground in an agate mortar for 0.5 hours and then sieved through a 400-mesh sieve to obtain a small-particle mixture B (particle size of 1μm to 50μm).

[0062] (3) The refined mixture B (3.6 parts) was mixed with silicon dioxide (1 part) and 100 parts of 0.1 mol / L sodium hydroxide. At the same time, CO2 gas was introduced into the solution for 10 min to obtain saturated gas solution C.

[0063] (4) The saturated gas solution C was placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 150°C for 12 hours. After cooling, product D was obtained.

[0064] (5) The product D is cleaned, dried and ground to obtain the fibrous inorganic toughened nanomaterial S04.

[0065] Example 5

[0066] (1) The premixed mixture A (50wt% calcium silicate, 24wt% calcium oxide, 24wt% nano-silica, and 2wt% alumina) was placed in a crucible and calcined in a muffle furnace. The calcination was carried out using a programmed temperature control method: 50℃-30min-100℃-30min-100℃-90min-700℃-110min-1200℃-30min-1200℃-60min-1300℃. After reaching 1300℃, the mixture was calcined for 2 hours, followed by natural cooling to obtain the calcined product.

[0067] The particle sizes of each component in the above mixture A are as follows: calcium silicate has a particle size of 50 nm to 10 μm, nano silica has a particle size of 20 nm to 100 nm, calcium oxide has a particle size of 5 μm to 50 μm, and aluminum oxide has a particle size of 10 μm to 50 μm.

[0068] (2) The calcined material was ground in a ball mill for 1 hour. The powder was then manually ground in an agate mortar for 0.5 hours and then sieved through a 400-mesh sieve to obtain a small-particle mixture B (particle size of 1μm to 50μm).

[0069] (3) The refined mixture B (3.6 parts) was mixed with silicon dioxide (1 part) and 100 parts of 0.3 mol / L sodium hydroxide. At the same time, CO2 gas was introduced into the solution for 10 min to obtain saturated gas solution C.

[0070] (4) The saturated gas solution C was placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 150°C for 12 hours. After cooling, product D was obtained.

[0071] (5) The product D is cleaned, dried and ground to obtain the fibrous inorganic toughened nanomaterial S05.

[0072] Example 6

[0073] (1) The premixed mixture A (50wt% calcium silicate, 24wt% calcium oxide, 24wt% nano-silica, and 2wt% alumina) was placed in a crucible and calcined in a muffle furnace. The calcination was carried out using a programmed temperature control method: 50℃-30min-100℃-30min-100℃-90min-700℃-110min-1200℃-30min-1200℃-60min-1300℃. After reaching 1300℃, the mixture was calcined for 2 hours, followed by natural cooling to obtain the calcined product.

[0074] The particle sizes of each component in the above mixture A are as follows: calcium silicate has a particle size of 50 nm to 10 μm, nano silica has a particle size of 20 nm to 100 nm, calcium oxide has a particle size of 5 μm to 50 μm, and aluminum oxide has a particle size of 10 μm to 50 μm.

[0075] (2) The calcined material was ground in a ball mill for 1 hour. The powder was then manually ground in an agate mortar for 0.5 hours and then sieved through a 400-mesh sieve to obtain a small-particle mixture B (particle size of 1μm to 50μm).

[0076] (3) The refined mixture B (3.6 parts) was mixed with silicon dioxide (1 part) and 100 parts of 0.5 mol / L sodium hydroxide. At the same time, CO2 gas was introduced into the solution for 10 min to obtain saturated gas solution C.

[0077] (4) The saturated gas solution C was placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 150°C for 12 hours. After cooling, product D was obtained.

[0078] (5) The product D is cleaned, dried and ground to obtain the fibrous inorganic toughened nanomaterial S06.

[0079] Example 7

[0080] (1) The premixed mixture A (35wt% calcium silicate, 24wt% calcium oxide, 24wt% nano-silica, and 2wt% alumina) was placed in a crucible and calcined in a muffle furnace. The calcination was carried out using a programmed temperature control method: 50℃-30min-100℃-30min-100℃-90min-700℃-110min-1200℃-30min-1200℃-60min-1300℃. After reaching 1300℃, the mixture was calcined for 2 hours, followed by natural cooling to obtain the calcined product.

[0081] The particle sizes of each component in the above mixture A are as follows: calcium silicate has a particle size of 50 nm to 10 μm, nano silica has a particle size of 20 nm to 100 nm, calcium oxide has a particle size of 5 μm to 50 μm, and aluminum oxide has a particle size of 10 μm to 50 μm.

[0082] (2) The calcined material was ground in a ball mill for 1 hour. The powder was then manually ground in an agate mortar for 0.5 hours and then sieved through a 400-mesh sieve to obtain a small-particle mixture B (particle size of 1μm to 50μm).

[0083] (3) The refined mixture B (3.6 parts) was mixed with silicon dioxide (1 part) and 100 parts of 0.1 mol / L sodium hydroxide. At the same time, CO2 gas was introduced into the solution for 10 min to obtain saturated gas solution C.

[0084] (4) The saturated gas solution C was placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 180°C for 12 hours. After cooling, product D was obtained.

[0085] (5) The product D is cleaned, dried and ground to obtain the fibrous inorganic toughened nanomaterial S07.

[0086] Example 8

[0087] (1) The premixed mixture A (50wt% calcium silicate, 24wt% calcium oxide, 24wt% nano-silica, and 2wt% alumina) was placed in a crucible and calcined in a muffle furnace. The calcination was carried out using a programmed temperature control method: 50℃-30min-100℃-30min-100℃-90min-700℃-110min-1200℃-30min-1200℃-60min-1300℃. After reaching 1300℃, the mixture was calcined for 2 hours, followed by natural cooling to obtain the calcined product.

[0088] The particle sizes of each component in the above mixture A are as follows: calcium silicate has a particle size of 50 nm to 10 μm, nano silica has a particle size of 20 nm to 100 nm, calcium oxide has a particle size of 5 μm to 50 μm, and aluminum oxide has a particle size of 10 μm to 50 μm.

[0089] (2) The calcined material was ground in a ball mill for 1 hour. The powder was then manually ground in an agate mortar for 0.5 hours and then sieved through a 400-mesh sieve to obtain a small-particle mixture B (particle size of 1μm to 50μm).

[0090] (3) The refined mixture B (3.6 parts) was mixed with silicon dioxide (1 part) and 100 parts of 0.3 mol / L sodium hydroxide. At the same time, CO2 gas was introduced into the solution for 10 min to obtain saturated gas solution C.

[0091] (4) The saturated gas solution C was placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 180°C for 12 hours. After cooling, product D was obtained.

[0092] (5) The product D is cleaned, dried and ground to obtain the fibrous inorganic toughened nanomaterial S08.

[0093] Example 9

[0094] (1) The premixed mixture A (35wt% calcium silicate, 19wt% calcium oxide, 45wt% nano-silica, and 1wt% alumina) was placed in a crucible and calcined in a muffle furnace. The calcination was carried out using a programmed temperature control method: 50℃-30min-100℃-30min-100℃-90min-700℃-110min-1200℃-30min-1200℃-60min-1300℃. After reaching 1300℃, the mixture was calcined for 2 hours, followed by natural cooling to obtain the calcined product.

[0095] The particle sizes of each component in the above mixture A are as follows: calcium silicate has a particle size of 50 nm to 10 μm, nano silica has a particle size of 20 nm to 100 nm, calcium oxide has a particle size of 5 μm to 50 μm, and aluminum oxide has a particle size of 10 μm to 50 μm.

[0096] (2) The calcined material was ground in a ball mill for 1 hour. The powder was then manually ground in an agate mortar for 0.5 hours and then sieved through a 400-mesh sieve to obtain a small-particle mixture B (particle size of 1μm to 50μm).

[0097] (3) The refined mixture B (3.6 parts) was mixed with silicon dioxide (1 part) and 100 parts of 0.5 mol / L sodium hydroxide. At the same time, CO2 gas was introduced into the solution for 10 min to obtain saturated gas solution C.

[0098] (4) The saturated gas solution C was placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 180°C for 12 hours. After cooling, product D was obtained.

[0099] (5) The product D is cleaned, dried and ground to obtain the fibrous inorganic toughened nanomaterial S09.

[0100] The material obtained in Example 8 above was characterized by electron microscopy, and its microstructure is shown in the figure below. Figure 1 As shown. From Figure 1 As can be seen, the product is fibrous in its overall microstructure, with a length of about 5μm to 10μm and a diameter of about 300nm to 600nm.

[0101] Simultaneously, the fibrous component of the material was subjected to electron beam irradiation, followed by the formation of nanostructures at different multiples, such as... Figure 2 and Figure 3 As shown in the attached diagram. It can be seen that... Figure 2 As shown, the electron beam decomposes the fiber, revealing many small particles, each with a polycrystalline structure, indicating that the material exhibits a distinct polycrystalline morphology.

[0102] To more intuitively observe the effect of the fibrous inorganic toughened composite material provided by this invention on the hydration of cement-based materials, the following tests were conducted.

[0103] The fibrous inorganic toughening composite material from Example 8 was added to cement, and the surface of the cement specimens obtained after 28 days of hydration was tested by scanning electron microscopy. The SEM images are shown below. Figure 4 As shown.

[0104] Meanwhile, a reference cement specimen was prepared under the same conditions, namely, a cement specimen obtained without the addition of this fibrous inorganic toughening composite material. Its SEM image is shown below. Figure 5 As shown.

[0105] contrast Figure 4 and Figure 5 It can be clearly seen that when the above-mentioned fibrous inorganic toughening composite material is added, the roughness of the cement block surface is significantly reduced, the surface is smoother, and the degree of order is significantly increased. The ordered structure can significantly enhance the toughness and strength of the material.

[0106] The performance of the materials obtained in the above embodiments was tested in consideration when applied. Specifically, the materials were added to cement-based materials and the relevant properties of the corresponding cement-based materials were measured.

[0107] Cement mortar flowability test method

[0108] The fluidity of cement mortar was tested in accordance with the national standard GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures". Naphthalene-based high-efficiency water-reducing agent was used. The comparison results are shown in Table 1.

[0109] Table 1 Comparison of Cement Mortar Flowability Tests

[0110]

[0111] As can be seen from the data in Table 1, when the above-mentioned fibrous inorganic toughening composite material of the present invention is added, the flowability of the corresponding cement-based material does not change significantly, proving that the inorganic toughening composite material has no effect on the workability of cement.

[0112] Methods for testing the mechanical properties of concrete

[0113] Concrete was prepared by adding the fibrous inorganic toughening composite materials provided in the above embodiments using the mix proportions shown in Table 2.

[0114] Table 2 Concrete Mix Proportions

[0115]

[0116] Note: The bulk density is 2350 kg / m³. 3 The sand content is 42.5%, and the water-cement ratio is 0.4.

[0117] The compressive and flexural strengths were tested according to GB / T50081 "Standard for Testing Physical and Mechanical Properties of Concrete" and are shown in Table 3.

[0118] Table 3 Mechanical properties of concrete (admixture dosage based on cement mass)

[0119]

[0120]

[0121] As shown in Table 3, by adding the fibrous inorganic toughening composite material provided by this invention, the flexural strength data of the obtained cement specimens at 7 days and 28 days are significantly improved, while the compressive strength is not reduced; and the best 28-day flexural strength is increased by 32%. Furthermore, compared with previous fibrous calcium silicate toughening methods, the highest flexural strength can be increased by 23% (from 12.88 MPa to 15.88 MPa), while this invention can increase it by 32% (from 4.3 MPa to 5.7 MPa).

[0122] These examples demonstrate that the fibrous inorganic toughened composite material provided by this invention can be used to prepare high-toughness cement-based materials.

Claims

1. A method for preparing a fibrous inorganic toughened composite material, characterized in that, Including the following steps: S1. A mixture consisting of calcium silicate, calcium oxide, nano-silica, and metal oxide is calcined at 1200℃~1400℃ to obtain a calcined product; wherein the metal oxide is selected from at least one of alumina and iron oxide, and its addition amount accounts for no more than 5% of the total mass of the mixture; S2. The calcined material is mixed with silicon dioxide and alkaline solution, and an acidic gas is introduced into it until saturation is achieved to obtain a saturated gas solution; the acidic gas is CO2. S3. The saturated gas solution is subjected to a hydrothermal reaction at 120℃~180℃ to obtain the fibrous inorganic toughened composite material.

2. The preparation method according to claim 1, characterized in that, In the mixture, the particle size of calcium silicate is 50 nm to 10 μm, the particle size of nano-silica is 20 nm to 100 nm, the particle size of calcium oxide is 5 μm to 50 μm, and the particle sizes of aluminum oxide and iron oxide are both 10 μm to 50 μm.

3. The preparation method according to claim 1 or 2, characterized in that, In step S1, a muffle furnace with programmed temperature control is used for calcination; the step heating process has 2 to 3 steps, with a total time of 5 to 8 hours, and calcination is carried out at a final reaction temperature of 1200℃ to 1400℃ for 1 to 3 hours.

4. The preparation method according to claim 1, characterized in that, In step S2, before mixing the calcined material with silicon dioxide and alkaline solution, it is first ground to a particle size of 1 μm to 50 μm.

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