A low-alkali, high-strength, crack-resistant, frost-resistant and cold-resistant concrete applicable to plateau areas and its preparation method

Abstract

The present invention relates to the field of building materials, and in particular to a low-alkali, high-strength, crack-resistant, frost-resistant and cold-resistant concrete suitable for plateau areas and a preparation method thereof. The concrete is calculated by weight and includes: 140-180 parts of low-alkali reinforced silicate cement, 275-360 parts of coarse aggregate, 450-580 parts of fine aggregate, 40-60 parts of silicon micropowder, 15-35 parts of lignin fiber, 1.8-3.6 parts of high-efficiency water reducer and 100 parts of water. The present invention prepares a concrete suitable for plateau areas, which is prepared by using low-alkali reinforced silicate cement as a main ingredient. Compared with traditional low-alkali cement, the low-alkali reinforced silicate cement prepared by the present invention is applied to concrete, which is not only higher in strength, but also more resistant to cracking, and has better cold and frost resistance.

Description

Technical Field

[0001] The invention relates to the field of building materials, and in particular to a low-alkali, high-strength, crack-resistant, frost-resistant and cold-resistant concrete suitable for plateau areas and a preparation method thereof. Background Art

[0002] Concrete is a composite material made of cement, aggregate and water in appropriate proportions and hardened after a certain period of time. It is the world's most widely used artificial civil construction material. Concrete has a wide range of raw materials, low cost and good use effect. It is widely used in structures such as houses, roads, military projects, and nuclear power plants. Concrete has the characteristics of abundant raw materials, low price and simple production process, which makes it widely used. At the same time, concrete also has the characteristics of high compressive strength, good durability and a wide range of strength grades. These characteristics make it widely used. It is not only used in various civil engineering projects, but also in the fields of machinery industry, marine development, geothermal engineering, etc., where concrete is also an important material.

[0003] In the plateau areas of western my country, the climate conditions are very harsh, the terrain, landform and hydrogeological conditions are complex, and the fragile ecological environment has brought great challenges to highway construction. The high-quality raw materials that can be used to build asphalt pavements are relatively scarce, which has brought great constraints to local highway construction. In the plateau areas, concrete is mostly in an extremely low temperature environment in the early stage. In this low temperature environment, concrete will solidify and harden slowly. During the hardening process, the internal temperature will be lower than the freezing point, and the liquid water will easily form ice crystals to expand, increase the volume, increase the porosity, and reduce the mechanical properties; the hydration rate is reduced, and the heat released by hydration is reduced, resulting in incomplete hydration of concrete, slow growth of various properties, and failure of concrete to reach the critical strength of antifreeze in the early stage; and the dry environment will aggravate the loss of water inside the concrete, causing concrete shrinkage and crack expansion, resulting in the deterioration of the internal structure of the concrete, reducing the mechanical and durability properties of the concrete, and seriously affecting the quality and service life of the concrete structure. Summary of the invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a low-alkali, high-strength, crack-resistant, frost-resistant and cold-resistant concrete suitable for plateau areas and a preparation method thereof.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] In a first aspect, the present invention provides a low-alkali, high-strength, crack-resistant, frost-resistant and cold-resistant concrete suitable for plateau areas, which comprises, calculated by weight:

[0007] 140 - 180 parts of low - alkali enhanced portland cement, 275 - 360 parts of coarse aggregate, 450 - 580 parts of fine aggregate, 40 - 60 parts of silica fume, 15 - 35 parts of lignin fiber, 1.8 - 3.6 parts of high - efficiency water - reducing agent and 100 parts of water.

[0008] Preferably, the coarse aggregate is crushed stone or pebble with a particle size between 5 - 10 mm, and the fine aggregate is river sand or sea sand with a particle size between 0.16 - 4.5 mm.

[0009] Preferably, the density of the silica fume is 2.65 g / cm 3 , and the particle size is 100 ± 10 μm.

[0010] Preferably, the density of the lignin fiber is 1.3 g / cm 3 , the length is 6 ± 1 mm, and the diameter is 10 ± 2 μm.

[0011] Preferably, the high - efficiency water - reducing agent is type I PCA - DS1 or type II PCA - DS2 of Chongqing Sansheng Industry Co., Ltd.

[0012] Preferably, the preparation method of the low - alkali enhanced portland cement includes:

[0013] S1. Prepare the grinding aid and strength enhancer:

[0014] Weigh p - aminobenzyl alcohol and add it into absolute ethanol. After fully stirring and dissolving, add epoxy - polyethylene glycol - acrylamide (EPO - PEG - ACA), heat up to reflux, stir and react for 2 - 5 h. After the reaction is completed, remove the solvent by vacuum distillation to obtain the grinding aid and strength enhancer;

[0015] S2. Grinding preparation:

[0016] Weigh low - alkali cement clinker, fly ash, and gypsum, mix them into a ball mill. After mixing evenly, add the grinding aid and strength enhancer, and carry out grinding treatment at a rotation speed of 40 - 80 r / min for 20 - 40 min. After ball - milling is completed, sieve to obtain the low - alkali enhanced portland cement.

[0017] Preferably, in the step S1, the weight - average molecular weight (Mw) of the epoxy - polyethylene glycol - acrylamide (EPO - PEG - ACA) is 500 - 2000.

[0018] Preferably, in the step S1, the mass ratio of p - aminobenzyl alcohol, epoxy - polyethylene glycol - acrylamide, and absolute ethanol is 0.12 - 0.36:0.9 - 2.7:10 - 20.

[0019] Preferably, in the step S2, the mass ratio of low-alkali cement clinker, fly ash, gypsum and grinding aid is 100:8-12:5-10:0.1-0.5.

[0020] Preferably, in the step S2, the components of the low-alkali cement clinker, calculated by weight percentage, include: SiO2: 22.67%, CaO: 64.56%, Al2O3: 5.25%, Fe2O3: 3.65%, MgO: 1.59%, K2O: 0.32%, Na2O: 0.22%, SO3: 0.33% and other impurities.

[0021] Preferably, in the step S2, the components of the gypsum, calculated by weight percentage, include: CaO: 32.32%, SiO2: 0.86%, Al2O3: 0.32%, MgO: 2.07%, SO3: 42.34%, H2O: 18.24% and other impurities.

[0022] Preferably, in the step S2, the fly ash is Class I fly ash or Class II fly ash.

[0023] Preferably, in the step S2, the sieving is through a 45μm square-hole sieve, and the sieve residue rate is less than 5%.

[0024] In a second aspect, the present invention provides a method for preparing a low-alkali high-strength crack-resistant, frost-resistant and cold-resistant concrete applicable to plateau areas, comprising the following steps:

[0025] (1) Weigh low-alkali enhanced portland cement, coarse aggregate, fine aggregate and silica fume by weight parts and mix them in a mixer. After mixing evenly, a mixed dry material is obtained;

[0026] (2) Add water to the mixed dry material, stir evenly, then add lignin fiber and high-range water reducer, and stir evenly again to obtain a mixed wet material;

[0027] (3) After the mixed wet material passes through a mold or is directly laid, sprinkle water for curing for at least 7 days to obtain the concrete.

[0028] The beneficial effects of the present invention are as follows:

[0029] 1. The present invention prepares a concrete applicable to plateau areas, which is prepared by using low-alkali enhanced portland cement as the main material. Compared with traditional low-alkali cement, the low-alkali enhanced portland cement prepared by the present invention is applied to the concrete, not only has higher strength, but also has stronger crack resistance and better cold and frost resistance performance.

[0030] 2. During the preparation of low-alkali cement, an appropriate amount of alkanolamine used as a cement additive can improve the fluidity of cement, reduce the heat release of cement, extend the setting time of concrete, etc. However, small-molecule alkanolamines have poor stability, and when the dosage is not well controlled, it will greatly affect the hydration process of cement, resulting in a significant decrease in the strength of concrete and a decline in performance such as crack resistance and cold resistance. The present invention prepares a low-alkali enhanced portland cement, which uses low-alkali cement clinker, fly ash, and calcium sulfate hydrate as raw materials, adds a grinding aid enhancer as a grinding aid material, and is prepared by grinding. Compared with traditional technologies, the present invention has improved the grinding aid material, replacing the traditional alkanolamine grinding aid with the reaction product of p-aminobenzyl alcohol and EPO-PEG-ACA, and found that it not only enhances the strength of concrete, but also significantly improves crack resistance and cold resistance. Detailed implementation mode

[0031] The following specifically illustrates the technical solutions of the present invention through specific examples. It should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before and after the combined steps or the insertion of other method steps between these clearly mentioned steps; it should also be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. Moreover, unless otherwise stated, the numbers of each method step are only convenient tools for identifying each method step, rather than limiting the arrangement order of each method step or the scope in which the present invention can be implemented. The change or adjustment of their relative relationship, without substantial change in technical content, should also be regarded as the scope in which the present invention can be implemented.

[0032] In order to better understand the above technical solutions, the exemplary embodiments of the present invention will be described in more detail below. Although the exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0033] The composition of the low-alkali cement clinker used in the embodiments of the present invention is calculated by weight percentage and includes: SiO2: 22.67%, CaO: 64.56%, Al2O3: 5.25%, Fe2O3: 3.65%, MgO: 1.59%, K2O: 0.32%, Na2O: 0.22%, SO3: 0.33% and other impurities.

[0034] The composition of the gypsum used in the embodiments of the present invention is calculated by weight percentage and includes: CaO: 32.32%, SiO2: 0.86%, Al2O3: 0.32%, MgO: 2.07%, SO3: 42.34%, H2O: 18.24% and other impurities.

[0035] The present invention will be further described below in conjunction with the following examples.

[0036] Example 1

[0037] A low-alkali, high-strength, crack-resistant, frost-resistant and cold-resistant concrete suitable for plateau areas, calculated by weight, comprising:

[0038] 160 parts of low-alkali reinforced silicate cement, 325 parts of coarse aggregate, 510 parts of fine aggregate, 50 parts of silica powder, 25 parts of lignin fiber, 2.5 parts of high-efficiency water reducer and 100 parts of water.

[0039] Among them, coarse aggregate is crushed stone or pebbles with a particle size between 5-10mm; fine aggregate is river sand or sea sand with a particle size between 0.16-4.5mm; the density of silica powder is 2.65g / cm 3 , particle size is 100±10μm; density of lignin fiber is 1.3g / cm 3 , length is 6±1mm, diameter is 10±2μm; the high-efficiency water reducer is Type I PCA-DS1 of Chongqing Sansheng Industrial Co., Ltd.

[0040] The preparation method of low-alkali reinforced silicate cement comprises:

[0041] S1. Preparation of grinding aid enhancer:

[0042] Weigh p-aminobenzyl alcohol and add it to anhydrous ethanol. After fully stirring and dissolving, add epoxy-polyethylene glycol-acrylamide (EPO-PEG-ACA, Mw is 1000), the mass ratio of p-aminobenzyl alcohol, epoxy-polyethylene glycol-acrylamide and anhydrous ethanol is 0.24:1.8:15, heat to reflux, stir and react for 3 hours, and after the reaction is completed, remove the solvent by reduced pressure distillation to obtain a grinding enhancer;

[0043] S2. Grinding preparation:

[0044] Weigh low-alkali cement clinker, grade I fly ash and gypsum, mix them into a ball mill, mix them evenly, then add a grinding enhancer, the mass ratio of low-alkali cement clinker, fly ash, gypsum and grinding enhancer is 100:10:8:0.3, grind them, the speed is 60r / min, the grinding time is 30min, after the ball milling is completed, pass through a 45μm square hole sieve with a sieve residue rate of less than 5%, and obtain low-alkali enhanced silicate cement.

[0045] The method for preparing the low-alkali, high-strength, crack-resistant, frost-resistant and cold-resistant concrete suitable for plateau areas comprises the following steps:

[0046] (1) Weigh low-alkali enhanced portland cement, coarse aggregate, fine aggregate, and silica fume according to parts by weight and mix them in a mixer. After mixing evenly, obtain the mixed dry material;

[0047] (2) Add water to the mixed dry material, stir evenly, then add lignin fiber and high-range water reducer, and stir evenly again to obtain the mixed wet material;

[0048] (3) After laying the mixed wet material on the ground, sprinkle water for curing for at least 7 days to obtain the required concrete.

[0049] Example 2

[0050] A low-alkali, high-strength, crack-resistant, frost-resistant, and cold-resistant concrete applicable to plateau areas, calculated according to parts by weight, includes:

[0051] 140 parts of low-alkali enhanced portland cement, 275 parts of coarse aggregate, 450 parts of fine aggregate, 40 parts of silica fume, 15 parts of lignin fiber, 1.8 parts of high-range water reducer, and 100 parts of water.

[0052] Among them, the coarse aggregate is crushed stone or pebbles with a particle size between 5 - 10 mm, the fine aggregate is river sand or sea sand with a particle size between 0.16 - 4.5 mm, the density of silica fume is 2.65 g / cm 3 , the particle size is 100 ± 10 μm, the density of lignin fiber is 1.3 g / cm 3 , the length is 6 ± 1 mm, the diameter is 10 ± 2 μm, and the high-range water reducer is Type II PCA-DS2 of Chongqing Sansheng Industry Co., Ltd.

[0053] Among them, the preparation method of the low-alkali enhanced portland cement includes:

[0054] S1. Prepare the grinding aid and strengthening agent:

[0055] Weigh p-aminobenzyl alcohol and add it to absolute ethanol. After fully stirring and dissolving, add epoxy-polyethylene glycol-acrylamide (EPO-PEG-ACA, Mw is 500). The mass ratio of p-aminobenzyl alcohol, epoxy-polyethylene glycol-acrylamide, and absolute ethanol is 0.12:0.9:10. Heat to reflux and stir for reaction for 2 h. After the reaction is completed, remove the solvent by vacuum distillation to obtain the grinding aid and strengthening agent;

[0056] S2. Grinding and preparation:

[0057] Weigh low-alkali cement clinker, Class II fly ash, and gypsum and mix them in a ball mill. After mixing evenly, add a grinding aid and strength enhancer. The mass ratio of low-alkali cement clinker, fly ash, gypsum, and grinding aid and strength enhancer is 100:8:5:0.1. Conduct grinding treatment at a rotational speed of 40 r / min for 20 min. After the ball milling is completed, pass through a 45-μm square-hole sieve with a residue rate of less than 5% to obtain low-alkali enhanced portland cement;

[0058] The preparation method of the above-mentioned low-alkali, high-strength, crack-resistant, frost-resistant, and cold-resistant concrete applicable to high-altitude areas includes the following steps:

[0059] (1) Weigh low-alkali enhanced portland cement, coarse aggregate, fine aggregate, and silica fume according to weight parts and mix them in a mixer. After mixing evenly, obtain a mixed dry material;

[0060] (2) Add water to the mixed dry material, stir evenly, then add lignin fiber and high-range water reducer, and stir evenly again to obtain a mixed wet material;

[0061] (3) After the mixed wet material passes through a mold or is directly laid, sprinkle water for curing for at least 7 days to obtain concrete.

[0062] Example 3

[0063] A low-alkali, high-strength, crack-resistant, frost-resistant, and cold-resistant concrete applicable to high-altitude areas, calculated according to weight parts, includes:

[0064] 180 parts of low-alkali enhanced portland cement, 360 parts of coarse aggregate, 580 parts of fine aggregate, 60 parts of silica fume, 35 parts of lignin fiber, 3.6 parts of high-range water reducer, and 100 parts of water.

[0065] Among them, the coarse aggregate is crushed stone or pebble with a particle size between 5-10 mm, the fine aggregate is river sand or sea sand with a particle size between 0.16-4.5 mm, the density of silica fume is 2.65 g / cm 3 , the particle size is 100 ± 10 μm, the density of lignin fiber is 1.3 g / cm 3 , the length is 6 ± 1 mm, the diameter is 10 ± 2 μm, and the high-range water reducer is Type I PCA-DS1 of Chongqing Sansheng Industry Co., Ltd.

[0066] Among them, the preparation method of the low-alkali enhanced portland cement includes:

[0067] S1. Prepare a grinding aid and strength enhancer:

[0068] Weigh p-aminobenzyl alcohol and add it to absolute ethanol. After fully stirring and dissolving, add epoxy-polyethylene glycol-acrylamide (EPO-PEG-ACA, Mw = 2000). The mass ratio of p-aminobenzyl alcohol, epoxy-polyethylene glycol-acrylamide, and absolute ethanol is 0.36:2.7:20. Heat up to reflux and stir for 5 h. After the reaction is completed, remove the solvent by vacuum distillation to obtain a grinding aid enhancer;

[0069] S2. Grinding preparation:

[0070] Weigh low-alkali cement clinker, Class I fly ash, and gypsum and mix them in a ball mill. After mixing evenly, add the grinding aid enhancer. The mass ratio of low-alkali cement clinker, fly ash, gypsum, and the grinding aid enhancer is 100:12:10:0.5. Conduct grinding treatment at a rotation speed of 80 r / min for 40 min. After the ball milling is completed, pass through a 45-μm square-hole sieve with a residue rate of less than 5% to obtain low-alkali enhanced Portland cement;

[0071] The preparation method of the above-mentioned low-alkali high-strength crack-resistant, freeze-resistant, and cold-resistant concrete applicable to high-altitude areas includes the following steps:

[0072] (1) Weigh low-alkali enhanced Portland cement, coarse aggregate, fine aggregate, and silica fume according to weight parts and mix them in a mixer. After mixing evenly, obtain a mixed dry material;

[0073] (2) Add water to the mixed dry material, stir evenly, then add lignin fiber and high-range water reducer, and stir evenly again to obtain a mixed wet material;

[0074] (3) After the mixed wet material passes through a mold or is directly laid, sprinkle water for curing for at least 7 days to obtain concrete.

[0075] Comparative Example 1

[0076] A kind of concrete, different from Example 1 in that the cement used is low-alkali Portland cement, and the grinding aid enhancer used in the preparation of low-alkali Portland cement is triethanolamine (traditional small molecule alcohol amine), and the rest is the same as Example 1.

[0077] That is, the preparation method of low-alkali Portland cement includes:

[0078] Weigh low-alkali cement clinker, Class I fly ash, and gypsum and mix them in a ball mill. After mixing evenly, add triethanolamine. The mass ratio of low-alkali cement clinker, fly ash, gypsum, and triethanolamine is 100:10:8:0.3. Conduct grinding treatment at a rotation speed of 60 r / min for 30 min. After the ball milling is completed, pass through a 45-μm square-hole sieve with a residue rate of less than 5% to obtain low-alkali Portland cement.

[0079] Comparative Example 2

[0080] A kind of concrete, different from that in Example 1, the cement used is low-alkali portland cement, and the grinding aid and strength enhancer used in the preparation of the low-alkali portland cement is p-aminobenzyl alcohol, and the rest is the same as in Example 1.

[0081] That is, the preparation method of the low-alkali portland cement includes:

[0082] Weigh low-alkali cement clinker, Class I fly ash, and gypsum and mix them into a ball mill. After mixing evenly, add p-aminobenzyl alcohol. The mass ratio of low-alkali cement clinker, fly ash, gypsum, and p-aminobenzyl alcohol is 100:10:8:0.3, and carry out grinding treatment. The rotation speed is 60 r / min, and the grinding time is 30 min. After the ball milling is completed, pass through a 45-μm square-hole sieve and the residue rate is less than 5%, and low-alkali portland cement is obtained.

[0083] Comparative Example 3

[0084] A kind of concrete, different from that in Example 1, the cement used is low-alkali portland cement, and the grinding aid and strength enhancer used in the preparation of the low-alkali portland cement is epoxy-polyethylene glycol-acrylamide (EPO-PEG-ACA, Mw is 1000), and the rest is the same as in Example 1.

[0085] That is, the preparation method of the low-alkali portland cement includes:

[0086] Weigh low-alkali cement clinker, Class I fly ash, and gypsum and mix them into a ball mill. After mixing evenly, add epoxy-polyethylene glycol-acrylamide. The mass ratio of low-alkali cement clinker, fly ash, gypsum, and epoxy-polyethylene glycol-acrylamide is 100:10:8:0.3, and carry out grinding treatment. The rotation speed is 60 r / min, and the grinding time is 30 min. After the ball milling is completed, pass through a 45-μm square-hole sieve and the residue rate is less than 5%, and low-alkali portland cement is obtained.

[0087] Experimental detection

[0088] Perform performance detection on the concretes prepared in Example 1 and Comparative Examples 1-3, and the detection standards refer to:

[0089] (1) Compressive strength: GB / T 50081-2016, the detection includes the strength at 7 d and 28 d;

[0090] (2) Crack resistance (crack resistance grade): JGJ / T 193-2009, the grade is divided into L-I, L-II, L-III, L-IV, L-V, and the higher the grade, the better the crack resistance performance;

[0091] (3) Frost resistance (rapid freezing method, frost resistance grade): GB / T 50164-2009. The frost resistance grades are divided into nine grades: F50, F100, F150, F200, F250, F300, F350, F400, and >F400. The larger the grade, the better the frost resistance.

[0092] The experimental test results are shown in Table 1.

[0093] Table 1 Performance of different concretes

[0094] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 7-day compressive strength (MPa) 38.7 35.3 33.1 36.5 28-day compressive strength (MPa) 52.1 45.7 42.6 49.3 Anti-cracking grade L-IV L-III L-Ⅱ L-III Freeze-thaw resistance grade F350 F250 F200 F300

[0095] It can be seen from Table 1 that compared with Comparative Examples 1-3, the concrete prepared in Example 1 of the present invention not only has high early (7d) compressive strength, but also has better late (28d) compressive strength. In addition, the crack resistance and frost resistance of the concrete prepared in Example 1 are better, and it is more suitable for use in plateau areas.

[0096] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0097] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A low-alkali, high-strength, crack-resistant, frost-resistant and cold-resistant concrete suitable for plateau areas, characterized in that: Calculated by weight, including: 140-180 parts of low-alkali reinforced Portland cement, 275-360 parts of coarse aggregate, 450-580 parts of fine aggregate, 40-60 parts of silica powder, 15-35 parts of lignin fiber, 1.8-3.6 parts of high-efficiency water reducer and 100 parts of water; The preparation method of the low-alkali reinforced silicate cement comprises: S1. Preparation of grinding aid enhancer: Weigh p-aminobenzyl alcohol and add it to anhydrous ethanol. After fully stirring and dissolving, add epoxy-polyethylene glycol-acrylamide, raise the temperature to reflux, and stir to react for 2-5 hours. After the reaction is completed, remove the solvent by vacuum distillation to obtain a grinding enhancer; S2, grinding preparation: Weigh low-alkali cement clinker, fly ash and gypsum and mix them into a ball mill. After mixing evenly, add a grinding enhancer and grind them at a speed of 40-80 r / min for 20-40 min. After the ball milling is completed, sieve to obtain low-alkali enhanced silicate cement. In S1, the weight average molecular weight of epoxy-polyethylene glycol-acrylamide is 500-2000; the mass ratio of p-aminobenzyl alcohol, epoxy-polyethylene glycol-acrylamide and anhydrous ethanol is 0.12-0.36:0.9-2.7:10-20; In the S2, the mass ratio of low-alkali cement clinker, fly ash, gypsum and grinding aid enhancer is 100:8-12:5-10:0.1-0.

5.

2. The low-alkali, high-strength, crack-resistant, frost-resistant and cold-resistant concrete suitable for plateau areas according to claim 1, characterized in that: The coarse aggregate is crushed stone or pebble with a particle size between 5-10 mm, and the fine aggregate is river sand or sea sand with a particle size between 0.16-4.5 mm.

3. The low-alkali, high-strength, crack-resistant, frost-resistant and cold-resistant concrete suitable for plateau areas according to claim 1, characterized in that: The density of the silicon powder is 2.65 g / cm 3 , particle size is 100±10μm; the density of the lignin fiber is 1.3g / cm³, the length is 6±1mm, and the diameter is 10±2μm.

4. The low-alkali, high-strength, crack-resistant, frost-resistant and cold-resistant concrete suitable for plateau areas according to claim 1, characterized in that: The high-efficiency water reducing agent is type I PCA-DS1 or type II PCA-DS2.

5. The low-alkali, high-strength, crack-resistant, frost-resistant and cold-resistant concrete suitable for plateau areas according to claim 1, characterized in that: In the S2, the components of the low-alkali cement clinker, calculated by weight percentage, include: SiO2: 22.67%, CaO: 64.56%, Al2O3: 5.25%, Fe2O3: 3.65%, MgO: 1.59%, K2O: 0.32%, Na2O: 0.22%, SO3: 0.33% and other impurities.

6. The low-alkali, high-strength, crack-resistant, frost-resistant and cold-resistant concrete suitable for plateau areas according to claim 1, characterized in that: In the S2, the components of gypsum, calculated by weight percentage, include: CaO: 32.32%, SiO2: 0.86%, Al2O3: 0.32%, MgO: 2.07%, SO3: 42.34%, H2O: 18.24% and other impurities.

7. A method for preparing low-alkali, high-strength, crack-resistant, frost-resistant and cold-resistant concrete suitable for plateau areas as claimed in claim 1, characterized in that: The following steps are involved: (1) Weigh low-alkali reinforced silicate cement, coarse aggregate, fine aggregate and silica powder according to weight proportions and mix them into a mixer. After mixing evenly, a mixed dry material is obtained; (2) Add water to the mixed dry material, stir evenly, then add lignin fiber and high-efficiency water reducer, stir evenly again, and obtain mixed wet material; (3) After the mixed wet material is passed through a mold or directly laid and watered for at least 7 days, concrete is obtained.