A micro-expanding cement and a method for preparing the same

Abstract

The present application relates to a kind of micro-expansion cement and its preparation method, belong to cement material preparation technical field.The micro-expansion cement disclosed in the present application includes the following raw materials: cement clinker, low calcium fly ash, expanding agent, modified carbon fiber, polyether ester elastic fiber, gypsum.Silicon dioxide is uniformly wrapped in the surface of carbon fiber by gas phase precipitation method, forms stable core-shell structure, can be uniformly and stably dispersed in cement slurry, the addition of modified carbon fiber limits the expansion rate of mortar, reduces porosity, improves the compactness and strength of cement board, and is matched with the polyether ester elastic fiber of larger elongation, obtains the micro-expansion cement with strong crack resistance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of cement materials, and relates to a micro-expansion cement and a preparation method thereof. BACKGROUND

[0002] Cement is widely used in road construction due to its high strength, good water stability, good frost resistance and other advantages. When ordinary cement is made into concrete, the shrinkage stress inside often exceeds the tensile strength of the concrete, which often causes cracks in the concrete, thereby affecting the stability and durability of the structure. The micro-expansion cement effectively improves the problem of cracks in concrete due to volume shrinkage through its shrinkage compensation mechanism.

[0003] There are many literatures on the study of the anti-cracking performance of cement. Chinese patent CN113024141A provides a modified carbon fiber, a preparation method thereof and a modified carbon fiber reinforced cement-based material. The patent incorporates carbon fibers, grows nano-silicon dioxide and carbon nanotubes on the surface of the carbon fibers in situ by oxidizing the surface of the carbon fibers, and incorporates the carbon fibers into the cement-based material, which effectively improves the early shrinkage performance of the cement-based material. The steps of preparing the modified carbon fiber are relatively complicated, and the growth of silicon dioxide is not easy to control; Chinese patent CN116789424A discloses a preparation method of a carbon fiber cement composite material. The invention uses cement, carbon fiber, silicon powder and dispersant as raw materials, wherein the dispersant is polyvinylpyrrolidone, hydroxyethyl cellulose, sodium hexametaphosphate or methyl cellulose. The addition of the dispersant solves the problem of agglomeration of carbon fibers in cement, but the dispersant also has a thickening effect, which has different degrees of influence on the expansion rate and strength of the cement mortar. There are also studies on the addition of polypropylene fibers, which are high ductility fibers. After adding polypropylene fibers, the compressive strength has little effect in the early stage but increases in the long term, and the flexural strength is significantly improved. However, with the increase of the fiber content, the flexural and compressive strengths first increase and then decrease, and the strength of the smaller strength is even lower than that of the block without fiber. This is mainly because when the content is large, the dispersibility of the fiber in the matrix is poor, and the entangled fiber is the weak point of damage, which causes the strength to decrease. SUMMARY

[0004] The present application relates to a micro-expansion cement and a preparation method thereof, and belongs to the technical field of cement material preparation. The micro-expansion cement disclosed by the present application comprises the following raw materials: cement clinker, low-calcium fly ash, expanding agent, modified carbon fiber, polyether ester elastic fiber and gypsum. The silicon dioxide is uniformly wrapped on the surface of the carbon fiber by the gas phase precipitation method to form a stable core-shell structure, which can be uniformly and stably dispersed in the cement slurry. The addition of the modified carbon fiber limits the expansion rate of the mortar, reduces the porosity, and improves the tightness and strength of the cement board. The combination of the polyether ester elastic fiber with a larger elongation rate obtains a micro-expansion cement with strong anti-cracking performance.

[0005] The object of the present application can be achieved by the following technical solutions:

[0006] A micro-expansion cement, comprising the following raw materials in parts by weight: cement clinker 50-80 parts, low-calcium fly ash 15-20 parts, expanding agent 8-12 parts, modified carbon fiber 10-12 parts, polyether ester elastic fiber 5-7 parts, and gypsum 8-10 parts.

[0007] Further, the expanding agent is calcium sulphoaluminate, and the content of calcium oxide in the low-calcium fly ash is 2.5-3.5%.

[0008] Further, the preparation method of the modified carbon fiber comprises the following steps:

[0009] (1) Pour concentrated nitric acid into carbon fiber so that the carbon fiber is completely immersed, then heat and stir, then filter, wash the solid with anhydrous ethanol, and dry to form pretreated carbon fiber for standby;

[0010] (2) Put the pretreated carbon fiber into a reaction chamber, heat after argon is introduced to exclude oxygen, then mix silane with argon as a carrier gas, close the silane gas channel, then introduce oxygen, and then cool to room temperature to obtain modified carbon fiber.

[0011] Further, the mass ratio of concentrated nitric acid to carbon fiber in step (1) is 5-8:3, wherein the mass fraction of concentrated nitric acid is 65-68%, the heating temperature is 100-120℃, the stirring time is 2-3h, and the drying temperature and time are 60-80℃ and 2-3h respectively.

[0012] Further, in step (2), the heating temperature is 600-700℃, the gas flow rate and time of mixing silane are 10-30sccm and 20-30min respectively, wherein the silane is composed of equal volumes of monosilane and disilane, and the gas flow rate and time of introducing oxygen are 8-10sccm and 40-60min respectively.

[0013] Further, the preparation method of the polyether ester elastic fiber is:

[0014] Put terephthalate, 1,4-butanediol, a catalyst and an antioxidant into an esterification kettle, heat and stir, condense and reflux, and then the obtained material at the bottom of the kettle is extruded by an extruder, wound, crushed, and then the polyether ester elastic fiber is obtained.

[0015] Further, the mass ratio among the terephthalate, 1,4 butanediol, catalyst and antioxidant is 3-5:1-2:0.05:0.01-0.02, wherein the catalyst is composed of cobalt acetate and butyl titanate with a mass ratio of 1:1, the temperature and time of the temperature-raising stirring are 210-220 DEG C and 1-2h respectively, the temperature and pressure of the extruder are 210-230 DEG C and 7-10 MPa respectively, the speed of the winding is 200-400 m / min, and the fineness and length of the polyether ester elastic fiber are 1-1.5D and 1-3 mm respectively.

[0016] Further, the preparation method of the micro-expansion cement is that all raw materials are mixed according to weight parts, wherein the clinker cement and low-calcium fly ash are dried at 110-120 DEG C for 2h, and the gypsum is ground into powder with a mesh number of 200-300.

[0017] The beneficial effects of the present application are:

[0018] 1. The present application uniformly coats the carbon fiber surface with silicon dioxide by the gas phase precipitation method, controls the growth of silicon dioxide through the oxygen gas flow, forms a stable and compact core-shell structure, and can be uniformly and stably dispersed in the cement slurry; at the same time, the addition of the modified carbon fiber improves the fluidity of the mortar, limits the expansion rate of the mortar, reduces the porosity, improves the compactness and strength of the cement board, and thus effectively improves the crack resistance of the cement;

[0019] 2. The hard segment polyester and soft segment polyether in the polyether ester elastic fiber make the material have excellent tensile strength at high and low temperatures, and the negative charge on the fiber surface increases under alkaline conditions, the mutual repulsion enhances the dispersibility of the fiber in water, and compared with the polypropylene fiber, the fiber has excellent mechanical properties and dispersibility. DETAILED DESCRIPTION

[0020] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined object, the specific embodiments, structures, features and effects according to the present application are described in detail as follows.

[0021] The cement clinker involved in the present application is purchased from Guangzhou Qiangsheng Cement Grinding Co., Ltd.; the low-calcium fly ash is purchased from Hebei Hukang Mineral Products Co., Ltd.; the carbon fiber is purchased from Jiangxi Suobang New Material Technology Co., Ltd.; the gypsum is purchased from Hebei Hui Baijia Building Material Co., Ltd., the model number is p130 / p160; and the antioxidant is purchased from Shenzhen Longdi Chemical Co., Ltd., the model number is Irganox1076.

[0022] Example 1

[0023] A micro-expansion cement, comprising the following raw materials by weight: cement clinker 50 parts, low calcium fly ash 15 parts, expansion agent 8 parts, modified carbon fiber 10 parts, polyether ester elastic fiber 5 parts, gypsum 8 parts.

[0024] The cement clinker has a mesh number of 180 meshes, the low calcium fly ash has a mesh number of 300 meshes, the expansion agent has a mesh number of 500 meshes, the carbon fiber has a length of 3 mm and an aspect ratio of 1:3, and the component analysis of the cement clinker is specifically as follows:

[0025]

[0026] The expansion agent is calcium sulphoaluminate expansion agent, and the content of calcium oxide in the low calcium fly ash is 2.5%.

[0027] The preparation method of the modified carbon fiber comprises the following steps:

[0028] (1) Pour concentrated nitric acid into the carbon fiber so that the carbon fiber is completely immersed, then heat and stir, filter, wash the solid with anhydrous ethanol, and dry to form pretreated carbon fiber for standby;

[0029] (2) Put the pretreated carbon fiber into a reaction chamber, heat after argon is introduced to exclude oxygen, then mix silane with argon as a carrier gas, close the silane gas channel, then introduce oxygen, and then cool to room temperature to obtain modified carbon fiber.

[0030] In step (1), the mass ratio of concentrated nitric acid to carbon fiber is 5:3, the mass fraction of concentrated nitric acid is 65%, the heating temperature is 100°C, the stirring time is 2 h, and the drying temperature and time are 60°C and 2 h respectively.

[0031] In step (2), the heating temperature is 600°C, the gas flow rate and time of mixing silane are 10 sccm and 20 min respectively, the silane is composed of equal volumes of monosilane and disilane, and the gas flow rate and time of introducing oxygen are 8 sccm and 40 min respectively.

[0032] The preparation method of the polyether ester elastic fiber is as follows:

[0033] Put terephthalate, 1,4-butanediol, a catalyst and an antioxidant into an esterification kettle, heat and stir, condense and reflux, and then the obtained material at the bottom of the kettle is extruded by an extruder, wound, crushed, and then the polyether ester elastic fiber is obtained.

[0034] The mass ratio among the terephthalate, 1, 4 butanediol, catalyst and antioxidant is 3:1:0.05:0.01, wherein the catalyst is composed of cobalt acetate and butyl titanate with a mass ratio of 1:1, the temperature and time of the temperature-rising stirring are 210℃ and 1h respectively, the temperature and pressure of the extruder are 210℃ and 7MPa respectively, the speed of the winding is 200m / min, and the fineness and length of the polyether ester elastic fiber are 1D and 1mm respectively.

[0035] The preparation method of the micro-expansion cement is that all raw materials are mixed according to weight parts, wherein the clinker cement and low-calcium fly ash are dried at 110℃ for 2h, and the gypsum is ground into powder with a mesh number of 200.

[0036] Example 2

[0037] A micro-expansion cement, which comprises the following raw materials in weight parts: cement clinker 65 parts, low-calcium fly ash 17 parts, expansion agent 10 parts, modified carbon fiber 11 parts, polyether ester elastic fiber 6 parts, and gypsum 9 parts.

[0038] The mesh number of the cement clinker is 180 meshes, the mesh number of the low-calcium fly ash is 300 meshes, the mesh number of the expansion agent is 500 meshes, the length of the carbon fiber is 3mm, and the aspect ratio is 1:3, and the component analysis of the cement clinker is specifically as follows:

[0039]

[0040] The expansion agent is calcium sulphoaluminate expansion agent, and the content of calcium oxide in the low-calcium fly ash is 2.5%.

[0041] The expansion agent is calcium sulphoaluminate expansion agent, and the content of calcium oxide in the low-calcium fly ash is 3%.

[0042] The preparation method of the modified carbon fiber comprises the following steps:

[0043] (1) Pour concentrated nitric acid into carbon fiber so that the carbon fiber is completely immersed, then heat and stir, and then filter, wash the solid with anhydrous ethanol, and dry to form pretreated carbon fiber for standby use;

[0044] (2) Put the pretreated carbon fiber into a reaction chamber, heat after argon is introduced to exclude oxygen, then mix silane with argon as carrier gas, close the silane gas channel, then introduce oxygen, and then cool to room temperature to obtain modified carbon fiber.

[0045] The mass ratio of concentrated nitric acid to carbon fiber in step (1) is 6.5:3, wherein the mass fraction of concentrated nitric acid is 67%, the heating temperature is 110℃, the stirring time is 2.5h, and the drying temperature and time are 70℃ and 2.5h respectively.

[0046] The temperature of the heating in the step (2) is 650℃, the gas flow and time of the mixing of the silane are 20sccm and 25min respectively, the gas flow and time of the oxygen are 9sccm and 50min respectively, and the silane is composed of equal volume of monosilane and disilane.

[0047] The preparation method of the polyether ester elastic fiber is as follows:

[0048] Put terephthalate, 1, 4 butanediol, catalyst and antioxidant into the esterification kettle, and then heat and stir, condense and reflux, and extrude the material obtained at the bottom of the kettle through an extruder, wind, and crush to obtain the polyether ester elastic fiber.

[0049] The mass ratio among the terephthalate, 1, 4 butanediol, catalyst and antioxidant is 4:1.5:0.05:0.015, the catalyst is composed of cobalt acetate and butyl titanate with a mass ratio of 1:1, the temperature and time of the heating and stirring are 215℃ and 1.5h respectively, the temperature and pressure of the extruder are 220℃ and 8MPa respectively, the winding speed is 300m / min, and the fineness and length of the polyether ester elastic fiber are 1.2D and 2mm respectively.

[0050] The preparation method of the micro-expansion cement is as follows: mix all raw materials according to weight parts, wherein the clinker cement and low-calcium fly ash are dried at 115℃ for 2h, and the gypsum is ground into powder with a mesh number of 250.

[0051] Example 3

[0052] A micro-expansion cement, which comprises the following raw materials in weight parts: cement clinker 80 parts, low-calcium fly ash 20 parts, expansion agent 12 parts, modified carbon fiber 12 parts, polyether ester elastic fiber 7 parts, and gypsum 10 parts.

[0053] The mesh number of the cement clinker is 180, the mesh number of the low-calcium fly ash is 300, the mesh number of the expansion agent is 500, the length of the carbon fiber is 3mm, and the length-diameter ratio is 1:3, and the component analysis of the cement clinker is as follows:

[0054]

[0055] The expansion agent is calcium sulphoaluminate expansion agent, and the content of calcium oxide in the low-calcium fly ash is 3.5%.

[0056] The preparation method of the modified carbon fiber comprises the following steps:

[0057] (1) pour concentrated nitric acid into carbon fiber, make carbon fiber completely immersed, then heat and stir, then filter, solid is washed with anhydrous ethanol, after drying, form pretreated carbon fiber, ready for use;

[0058] (2) pretreated carbon fiber is placed in a reaction chamber, after argon is introduced to remove oxygen, heat, then mix silane with argon as carrier gas, close the silane gas channel, then introduce oxygen, then cool to room temperature, obtain modified carbon fiber.

[0059] The mass ratio of concentrated nitric acid to carbon fiber in step (1) is 8:3, wherein the mass fraction of concentrated nitric acid is 68%, the heating temperature is 120℃, the stirring time is 3h, and the drying temperature and time are 80℃ and 3h respectively.

[0060] The heating temperature in step (2) is 700℃, the gas flow and time of mixing silane are 30sccm and 30min respectively, wherein silane is composed of equal volume of methylsilane and ethylsilane, the gas flow and time of introducing oxygen are 10sccm and 60min respectively.

[0061] The preparation method of the polyether ester elastic fiber is:

[0062] Put terephthalate, 1,4-butanediol, catalyst and antioxidant into the esterification kettle, heat and stir, condense reflux, the material obtained at the bottom of the kettle is extruded by an extruder, wound, crushed, and then the polyether ester elastic fiber is obtained.

[0063] The mass ratio among terephthalate, 1,4-butanediol, catalyst and antioxidant is 5:2:0.05:0.02, wherein the catalyst is composed of cobalt acetate and butyl titanate with a mass ratio of 1:1, the temperature and time of heating and stirring are 220℃ and 2h respectively, the temperature and pressure of the extruder are 230℃ and 10MPa respectively, the winding speed is 400m / min, and the fineness and length of the polyether ester elastic fiber are 1.5D and 3mm respectively.

[0064] The preparation method of the micro-expanding cement is: all raw materials are mixed according to weight parts, wherein the clinker cement and low-calcium fly ash are dried at 120℃ for 2h, and the gypsum is ground into powder with a mesh number of 300.

[0065] Comparative Example 1

[0066] The difference between Comparative Example 1 and Example 2 is only that the modified carbon fiber of Comparative Example 1 is obtained by the preparation method in Example 1 of patent CN113024141A, and the specific steps are as follows:

[0067] (1) Removal of the epoxy coating on the surface of the carbon fiber, 1 g of carbon fiber was placed in a Soxhlet extractor containing acetone, and the carbon fiber surface was cleaned with acetone at a temperature of 75°C to remove impurities, the cleaning time was 24 h, after the reaction was completed, it was cooled to room temperature, the carbon fiber was taken out, and then dried at 70°C for 2 h to obtain carbon fiber with the surface epoxy coating removed;

[0068] (2) Oxidation of the carbon fiber, the carbon fiber obtained in step (1) was immersed in concentrated nitric acid, the mass of the carbon fiber to the volume of the concentrated nitric acid was 1 g: 100 ml, heated to 80°C, reacted for 3 h, then the carbon fiber in the concentrated nitric acid was taken out, the obtained carbon fiber was placed in distilled water for 5 min, taken out and washed with ethanol for 3 times, dried at a temperature of 70°C for 3 h to obtain dried oxidized carbon fiber;

[0069] (3) In-situ growth of nano-silicon dioxide on the surface of the carbon fiber, the oxidized carbon fiber was immersed in a KH550 solution (mass fraction of 3%, the mass of the carbon fiber to the volume of the KH550 solution was 1 g: 200 ml), and soaked at 70°C for 3 h; then the carbon fiber was taken out, washed with ethanol for 3 times, dried at 70°C for 2 h, and then placed in an analytical pure ethanol solvent (the mass of the carbon fiber to the volume of the ethanol was 1 g: 500 ml), then, an ionic surfactant CTAB with a mass fraction of 1% (the mass fraction of CTAB in the ethanol solution) was added to the mixture and stirred uniformly, and ammonia water (the volume ratio of ammonia water to ethanol was 1:25) was added as a catalyst to provide an alkaline reaction environment and subjected to ultrasonic treatment for 30 min;

[0070] (4) Then, tetraethyl orthosilicate (volume ratio of tetraethyl orthosilicate to ethanol was 1:12.5) was added dropwise, and slowly stirred at a constant temperature of 45°C for 10 h, filtered, washed with methanol for 3 times, and dried at 70°C for 3 h to obtain dried carbon fiber with nano-silicon dioxide in-situ grown on the surface, which was the modified carbon fiber.

[0071] Comparative Example 2

[0072] On the basis of Example 2, a micro-expanding cement, which comprises the following raw materials in parts by weight: cement clinker 65 parts, low-calcium fly ash 17 parts, expanding agent 10 parts, carbon fiber 11 parts, polyether ester elastic fiber 6 parts, gypsum 9 parts, methyl cellulose dispersing agent 0.5 parts.

[0073] The cement clinker has a mesh number of 180 meshes, the low-calcium fly ash has a mesh number of 300 meshes, the expanding agent has a mesh number of 500 meshes, the carbon fiber has a length of 3 mm and an aspect ratio of 1:3, and the component analysis of the cement clinker is specifically as follows:

[0074]

[0075] The expanding agent is calcium sulphoaluminate expanding agent, and the calcium oxide content in the low calcium fly ash is 2.5%.

[0076] The expanding agent is calcium sulphoaluminate expanding agent, and the calcium oxide content in the low calcium fly ash is 3%.

[0077] The preparation method of the polyether ester elastic fiber is as follows:

[0078] Put terephthalate, 1, 4 butanediol, catalyst and antioxidant into the esterification kettle, and then heat and stir, condense and reflux, and extrude the material obtained at the kettle bottom through an extruder, wind, and crush to obtain the polyether ester elastic fiber.

[0079] The mass ratio among the terephthalate, 1, 4 butanediol, catalyst and antioxidant is 4:1.5:0.05:0.015, wherein the catalyst is composed of cobalt acetate and butyl titanate with a mass ratio of 1:1, the temperature and time of the heat and stirring are 215℃ and 1.5h respectively, the temperature and pressure of the extruder are 220℃ and 8MPa respectively, the winding speed is 300m / min, and the fineness and length of the polyether ester elastic fiber are 1.2D and 2mm respectively.

[0080] The preparation method of the micro-expanding cement is as follows: all raw materials are mixed according to weight parts, wherein the clinker cement and low calcium fly ash are dried at 115℃ for 2h, and the gypsum is ground into powder with a mesh number of 250.

[0081] Comparative Example 3

[0082] On the basis of Example 2, the gas flow of oxygen in the preparation of modified carbon fiber is 12sccm, and other conditions are consistent with Example 2.

[0083] Comparative Example 4

[0084] On the basis of Example 2, the gas flow of oxygen in the preparation of modified carbon fiber is 6sccm, and other conditions are consistent with Example 2.

[0085] Comparative Example 5

[0086] On the basis of Example 2, the polyether ester elastic fiber in the raw material is removed, and an equal weight part of polypropylene fiber is used to replace it, and other conditions are consistent with Example 2 of the application.

[0087] Performance test

[0088] The modified carbon fibers prepared in Examples 1-3, Comparative Example 1, Comparative Examples 3-4 were used as samples, and an electron scanning microscope was used to observe whether the fiber surface was smooth and continuous; in addition, the micro-expanding cement obtained in Examples 1-3 and Comparative Examples 1-5 was tested for expansion rate, compressive strength and flexural strength according to the method of JC / T313-2009, and the test results are shown in Table 1.

[0089] Table 1 Test results

[0090]

[0091] From the analysis in Table 1, it can be concluded that the surface of the modified fiber of Examples 1-3 is wrapped with smooth and continuous silicon dioxide, as observed by electron microscopy. However, in Comparative Example 1, the growth of nano-silicon dioxide on the surface of carbon fiber cannot control the growth process and rate, and the nano-silicon dioxide on the surface of carbon fiber appears to be stacked. In Comparative Example 3, increasing the oxygen flow rate makes the speed of silicon dioxide adhesion too fast, and the carbon fiber surface is prone to have vacancies and cracks. In Comparative Example 4, reducing the oxygen flow rate reduces the surface adhesion of silicon dioxide on the surface of carbon fiber and forms a discontinuous structure. The linear expansion rate of Examples 1-3 is ≥0.1%, and the 28d linear expansion rate is ≤0.8%. Combined with the flexural strength and compressive strength, it can be judged that the addition of modified carbon fiber in Examples 1-3 limits the expansion rate of the mortar, reduces the porosity, improves the tightness and strength of the cement board, and effectively compensates for the cracking problem caused by the shrinkage of the base layer. The expansion rate of Comparative Examples 1-5 is greater than that of Examples 1-3, and the flexural strength and compressive strength are less than those of Examples 1-3. It can be judged that the expansion of Comparative Examples 1-5 will increase the porosity of the system, disperse the structure, and reduce the strength. Due to the defects of the surface structure of the modified carbon fiber and the hydrophobicity of the carbon fiber itself, it is easy to agglomerate in water. The polypropylene fiber used in Comparative Example 5 is also prone to agglomeration in water.

[0092] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any equivalent embodiments with equivalent changes and modifications made to the above embodiments based on the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A micro-expanding cement, characterized by, The micro-expansion cement comprises the following raw materials by weight: cement clinker 50-80 parts, low calcium fly ash 15-20 parts, expanding agent 8-12 parts, modified carbon fiber 10-12 parts, polyether ester elastic fiber 5-7 parts, and gypsum 8-10 parts. The preparation method of the modified carbon fiber comprises the following steps: (1) pour concentrated nitric acid into the carbon fiber so that the carbon fiber is completely immersed, then heat and stir, filter, wash the solid with anhydrous ethanol, and dry to obtain pretreated carbon fiber; (2) place the pretreated carbon fiber in a reaction chamber, heat after argon is introduced to remove oxygen, then mix silane with argon as a carrier gas, close the silane gas channel, then introduce oxygen, and cool to room temperature to obtain modified carbon fiber; In step (2), the heating temperature is 600-700 DEG C, the gas flow and time of mixing silane are 10-30 sccm and 20-30 min respectively, the silane is composed of equal volumes of monosilane and disilane, the gas flow and time of introducing oxygen are 8-10 sccm and 40-60 min respectively; The preparation method of the polyether ester elastic fiber is as follows: Put terephthalate, 1, 4 butanediol, a catalyst and an antioxidant into an esterification kettle, heat and stir, condense and reflux, extrude the material obtained at the bottom of the kettle through an extruder, wind, and crush to obtain the polyether ester elastic fiber.

2. A micro-expanding cement according to claim 1, characterized in that, The expanding agent is calcium sulphoaluminate expanding agent, and the content of calcium oxide in the low calcium fly ash is 2.5-3.5%.

3. A micro-expansive cement according to claim 1, characterized in that, In step (1), the mass ratio of concentrated nitric acid to carbon fiber is 5-8:3, the mass fraction of concentrated nitric acid is 65-68%, the heating temperature is 100-120 DEG C, the stirring time is 2-3 h, and the drying temperature and time are 60-80 DEG C and 2-3 h respectively.

4. A micro-expansive cement according to claim 1, characterized in that, The mass ratio among the terephthalate, 1, 4 butanediol, catalyst and antioxidant is 3-5:1-2:0.05:0.01-0.02, the catalyst is composed of cobalt acetate and butyl titanate in a mass ratio of 1:1, the heating and stirring temperature and time are 210-220 DEG C and 1-2 h respectively, the temperature and pressure of the extruder are 210-230 DEG C and 7-10 MPa respectively, the winding speed is 200-400 m / min, and the fineness and length of the polyether ester elastic fiber are 1-1.5 D and 1-3 mm respectively.

5. A method of producing the micro-expansive cement according to claim 1, characterized by, The preparation method of the micro-expansion cement is to mix all the raw materials according to weight, wherein the cement clinker and low calcium fly ash are dried at 110-120 DEG C for 2 h, and the gypsum is ground into powder with a mesh number of 200-300.

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