A low-alkali frost-resistant portland cement for plateau regions and its preparation method

Abstract

The present invention relates to a low-alkali frost-resistant portland cement for plateau areas and a preparation method thereof. The preparation method comprises the following steps: Step 1, weigh allyl glycidyl ether, add it into absolute ethanol, add 2,3-dimercaptopropanol, add a photoinitiator, and react under the action of ultraviolet light to obtain thioetherified glycidyl ether; Step 2, mix thioetherified glycidyl ether and amino-polyethylene glycol-maleimide in absolute ethanol, heat up and stir to react to obtain a modified grinding aid; Step 3, add low-alkali cement clinker, fly ash, gypsum and the modified grinding aid into a ball mill for grinding treatment. After the grinding is completed, sieve to obtain the low-alkali frost-resistant portland cement. The portland cement prepared by the present invention is prepared by mixing and grinding low-alkali cement clinker, fly ash and gypsum with a modified grinding aid. Through experimental application, it is found that the low-alkali cement prepared by the present invention has high strength, crack resistance and frost resistance.

Description

Technical Field

[0001] The present invention relates to the field of building materials, and particularly to a low-alkali frost-resistant portland cement for plateau regions and a preparation method thereof. Background Art

[0002] Ordinary portland cement is a hydraulic cementitious material made from portland cement clinker, appropriate amount of gypsum and specified admixtures; the admixtures include granulated blast furnace slag, granulated blast furnace slag powder, fly ash, and pozzolan. Ordinary portland cement is divided into portland cement, ordinary portland cement, slag portland cement, pozzolanic portland cement, fly ash portland cement and composite portland cement according to the variety and dosage of the admixtures. These different types of cement have different chemical and physical properties. In various projects, suitable cement should be selected according to the project characteristics, usage requirements and the properties of various cements.

[0003] In the western plateau regions of our country, the climatic conditions are very harsh, the terrain, landform and hydrogeological conditions are complex, and the fragile ecological environment has brought huge challenges to highway construction. The relatively scarce high-quality raw materials available for building asphalt pavements have greatly restricted local highway construction. Ordinary portland cement has a relatively high alkali content. After construction, the alkali in the cement will react with certain components in the aggregates of the concrete to form silicate gel, which is likely to cause an increase in the volume of the concrete and generate expansion stress. In severe cases, it will even cause cracks in the concrete, posing potential safety hazards to the project. In order to avoid such potential safety hazards, the prior art often uses a large amount of low-alkali cement to reduce the cracks in the concrete. Although the low-alkali portland cement on the market can improve the early strength and corrosion resistance of the concrete, the addition of alkali activators has significantly increased the alkalinity of the cement, making it no longer have good crack resistance and frost resistance, and the later strength has also decreased significantly. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a low-alkali frost-resistant portland cement for plateau regions and a preparation method thereof.

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

[0006] In the first aspect, the present invention provides a preparation method for a low-alkali frost-resistant portland cement for plateau regions, comprising the following steps:

[0007] Step 1, weigh allyl glycidyl ether and add it to absolute ethanol. After fully dissolving, add 2,3-dimercaptopropanol, stir evenly again, add a photoinitiator under the condition of using nitrogen as a protective gas, and stir and react for 1-2 h under the action of ultraviolet light. After the reaction is completed, remove the solvent under reduced pressure to obtain thioetherified glycidyl ether;

[0008] Step 2, mix thioetherified glycidyl ether and amino-polyethylene glycol-maleimide (NH 2 -PEG-MAL) in absolute ethanol. After stirring well, heat to reflux and stir for reaction for 2 - 5 h. After the reaction ends, remove the solvent by vacuum distillation to obtain the modified grinding aid;

[0009] Step 3, add low-alkali cement clinker, fly ash, gypsum and the modified grinding aid into a ball mill for grinding. After the grinding ends, sieve to obtain the low-alkali frost-resistant portland cement.

[0010] Preferably, in the said Step 1, the mass ratio of allyl glycidyl ether, 2,3-dimercaptopropanol and absolute ethanol is 1.4 - 2.8:0.6 - 1.2:40 - 60.

[0011] Preferably, in the said Step 1, the photoinitiator is one of dimethoxybenzil, ethoxybenzil, butoxybenzil, and the addition amount of the photoinitiator is 1.5% - 5.5% of the mass of allyl glycidyl ether.

[0012] Preferably, in the said Step 1, the power of the ultraviolet light is 50 - 100 W and the wavelength is 365 nm.

[0013] Preferably, in the said Step 2, the mass ratio of thioetherified glycidyl ether, amino-polyethylene glycol-maleimide (NH 2 -PEG-MAL) and absolute ethanol is 0.21 - 0.42:0.8 - 1.6:10 - 20.

[0014] Preferably, in the said Step 2, the weight-average molecular weight (Mw) of amino-polyethylene glycol-maleimide is 500 - 2000.

[0015] Preferably, in the said Step 2, the temperature of heating to reflux is 65 - 75 °C.

[0016] Preferably, in the said Step 3, the rotation speed of the ball mill is 40 - 80 r / min and the grinding time is 20 - 40 min.

[0017] Preferably, in the said Step 3, the residue rate of the low-alkali frost-resistant portland cement on a 45-μm square-hole sieve is less than 5%.

[0018] Preferably, in the said Step 3, the mass ratio of low-alkali cement clinker, fly ash, gypsum and the modified grinding aid is 100:6 - 10:6 - 12:0.1 - 0.5.

[0019] Preferably, in the said Step 3, the composition of the low-alkali cement clinker, calculated by weight percentage, includes: SiO 2: 22.67%, CaO: 64.56%, Al 2 O 3 : 5.25%, Fe 2 O 3 : 3.65%, MgO: 1.59%, K 2 O: 0.32%, Na 2 O: 0.22%, SO 3 : 0.33% and other impurities.

[0020] Preferably, in the said step 3, the composition of the gypsum is calculated by weight percentage, including: CaO: 32.32%, SiO 2 : 0.86%, Al 2 O 3 : 0.32%, MgO: 2.07%, SO 3 : 42.34%, H 2 O: 18.24% and other impurities.

[0021] Preferably, in the said step 3, the fly ash is Class I fly ash or Class II fly ash.

[0022] In the second aspect, the present invention provides a low-alkali frost-resistant portland cement for plateau regions, which is prepared by using the above-mentioned preparation method.

[0023] In the third aspect, the present invention provides an application of the low-alkali frost-resistant portland cement for plateau regions in concrete. The concrete includes, calculated by weight parts:

[0024] 100 parts of low-alkali frost-resistant portland cement, 313 - 354 parts of coarse aggregate, 472 - 526 parts of fine aggregate, 55 - 75 parts of fly ash, 28 - 56 parts of polyester fiber, 1.3 - 2.6 parts of high-range water reducer, and 78 - 96 parts of water.

[0025] 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.

[0026] Preferably, the fly ash is Class I fly ash.

[0027] Preferably, the length of the polyester fiber is 5 - 8 mm, and the diameter is 20 ± 2 μm.

[0028] Preferably, the polyester fiber is at least one of polybutylene terephthalate fiber (PBT fiber), polyethylene terephthalate fiber (PET fiber), and polytrimethylene terephthalate fiber (PTT fiber).

[0029] Preferably, the high-range water reducer is TH-928 polycarboxylate-based superplasticizer.

[0030] The beneficial effects of the present invention are as follows:

[0031] 1. The present invention prepares a low-alkali frost-resistant portland cement for plateau areas. This portland cement is a low-alkali cement, which is prepared by mixing and grinding low-alkali cement clinker, fly ash, and gypsum with a modified grinding aid. Through experimental applications, it is found that the low-alkali cement prepared by the present invention has high strength, crack resistance, and frost resistance.

[0032] 2. In the preparation of the low-alkali cement of the present invention, the grinding aid used is prepared by cross-linking and combining thioetherified glycidyl ether and amino-polyethylene glycol-maleimide (NH 2 -PEG-MAL) through epoxy-amino cross-linking. Thioetherified glycidyl ether is prepared by using allyl glycidyl ether and 2,3-dimercaptopropanol as reactants through a thiol-ene click chemical reaction. Compared with traditional alkanolamine grinding aids, the grinding aid prepared by the present invention can not only ensure grinding, but also has good improvement on the strength, crack resistance, and frost resistance of concrete. Specific Embodiments

[0033] The following specifically describes 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 embodiments 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.

[0034] 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.

[0035] In the embodiments of the present invention, the components of the low-alkali cement clinker are calculated by weight percentage and include: SiO 2 : 22.67%, CaO: 64.56%, Al 2 O 3 : 5.25%, Fe 2 O 3: 3.65%, MgO: 1.59%, K 2 O: 0.32%, Na 2 O: 0.22%, SO 3 : 0.33% and other impurities.

[0036] In the embodiments of the present invention, the components of the gypsum used are calculated by weight percentage and include: CaO: 32.32%, SiO 2 : 0.86%, Al 2 O 3 : 0.32%, MgO: 2.07%, SO 3 : 42.34%, H 2 O: 18.24% and other impurities.

[0037] The present invention will be further described in conjunction with the following embodiments. Example 1

[0038] A preparation method for low-alkali frost-resistant portland cement used in plateau areas, comprising the following steps:

[0039] Step 1, weigh allyl glycidyl ether and add it to absolute ethanol. After fully dissolving, add 2,3-dimercaptopropanol. The mass ratio of allyl glycidyl ether, 2,3-dimercaptopropanol and absolute ethanol is 2.1:0.9:50. Stir evenly again. Under the condition that nitrogen is used as the protective gas, add dimethyl benzoyl peroxide. The addition amount is 3.5% of the mass of allyl glycidyl ether. Stir and react for 1.5 h under the action of ultraviolet light. The power of the ultraviolet light is 80 W and the wavelength is 365 nm. After the reaction is completed, remove the solvent under reduced pressure to obtain thioetherified glycidyl ether;

[0040] Step 2, mix thioetherified glycidyl ether and amino-polyethylene glycol-maleimide (NH 2 -PEG-MAL, Mw = 1000) in absolute ethanol. The mass ratio of thioetherified glycidyl ether, amino-polyethylene glycol-maleimide (NH 2 -PEG-MAL) and absolute ethanol is 0.31:1.2:15. After fully stirring evenly, heat to reflux at 70 °C and stir and react for 2 - 5 h. After the reaction is completed, remove the solvent by vacuum distillation to obtain a modified grinding aid;

[0041] Step 3, add low-alkali cement clinker, Class I fly ash, gypsum and the modified grinding aid to a ball mill. The mass ratio of low-alkali cement clinker, fly ash, gypsum and the modified grinding aid is 100:9:8:0.3. The rotation speed of the ball mill is 60 r / min and the grinding time is 30 min. Carry out grinding treatment. After the grinding is completed, sieve. The residue rate on a 45 μm square hole sieve is less than 5%, and low-alkali frost-resistant portland cement is obtained.

[0042] For the application of the above-mentioned low-alkali and frost-resistant portland cement in concrete in plateau areas, the concrete is calculated by weight parts and includes:

[0043] 100 parts of low-alkali and frost-resistant portland cement, 327 parts of coarse aggregate, 508 parts of fine aggregate, 65 parts of fly ash, 42 parts of polyester fiber, 2.1 parts of high-range water reducer and 87 parts of water.

[0044] 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 fly ash is Class I fly ash; the polyester fiber is PBT fiber with a length of 5-8 mm and a diameter of 20±2 μm; the high-range water reducer is TH-928 polycarboxylate-based superplasticizer. Example 2

[0045] A preparation method of low-alkali and frost-resistant portland cement for plateau areas includes the following steps:

[0046] Step 1: Weigh allyl glycidyl ether and add it into absolute ethanol. After fully dissolving, add 2,3-dimercaptopropanol. The mass ratio of allyl glycidyl ether, 2,3-dimercaptopropanol and absolute ethanol is 1.4:0.6:40. Stir evenly again. Under the condition that nitrogen is used as the protective gas, add ethyl benzoin ether, and the added amount is 1.5% of the mass of allyl glycidyl ether. Stir and react for 1 h under the action of ultraviolet light. The power of the ultraviolet light is 50 W and the wavelength is 365 nm. After the reaction is completed, remove the solvent under reduced pressure to obtain thioetherified glycidyl ether;

[0047] Step 2: Mix thioetherified glycidyl ether and amino-polyethylene glycol-maleimide (NH 2 -PEG-MAL, Mw = 500) in absolute ethanol. The mass ratio of thioetherified glycidyl ether, amino-polyethylene glycol-maleimide (NH 2 -PEG-MAL) and absolute ethanol is 0.21:0.8:10. After fully stirring evenly, heat to reflux at 65°C and stir and react for 2 h. After the reaction is completed, remove the solvent by vacuum distillation to obtain a modified grinding aid;

[0048] Step 3: Add low-alkali cement clinker, Class II fly ash, gypsum and the modified grinding aid into a ball mill. The mass ratio of low-alkali cement clinker, fly ash, gypsum and the modified grinding aid is 100:6:6:0.1. The rotation speed of the ball mill is 40 r / min and the grinding time is 20 min for grinding treatment. After the grinding is completed, sieve. The residue rate on a 45-μm square-hole sieve is less than 5%, and then the low-alkali and frost-resistant portland cement is obtained.

[0049] The above application of low-alkali frost-resistant portland cement in concrete in plateau areas, the concrete is calculated by weight parts and includes:

[0050] 100 parts of low-alkali frost-resistant portland cement, 313 parts of coarse aggregate, 472 parts of fine aggregate, 55 parts of fly ash, 28 parts of polyester fiber, 1.3 parts of high-range water reducer and 78 parts of water.

[0051] Among them, the coarse aggregate is crushed stone or pebble with a particle size between 5-10mm; the fine aggregate is river sand or sea sand with a particle size between 0.16-4.5mm; the fly ash is Class I fly ash; the polyester fiber is PET fiber with a length of 5-8mm and a diameter of 20±2μm; the high-range water reducer is TH-928 polycarboxylate-based superplasticizer. Example 3

[0052] A preparation method of low-alkali frost-resistant portland cement for plateau areas includes the following steps:

[0053] Step 1, weigh allyl glycidyl ether and add it into absolute ethanol. After fully dissolving, add 2,3-dimercaptopropanol. The mass ratio of allyl glycidyl ether, 2,3-dimercaptopropanol and absolute ethanol is 2.8:1.2:60. Stir evenly again. Under the condition of using nitrogen as the protective gas, add benzoin ethyl ether, and the addition amount is 5.5% of the mass of allyl glycidyl ether. Stir and react for 2h under the action of ultraviolet light. The power of the ultraviolet light is 100W and the wavelength is 365nm. After the reaction is completed, remove the solvent under reduced pressure to obtain thioetherified glycidyl ether;

[0054] Step 2, mix thioetherified glycidyl ether and amino-polyethylene glycol-maleimide (NH 2 -PEG-MAL, Mw = 2000) in absolute ethanol. The mass ratio of thioetherified glycidyl ether, amino-polyethylene glycol-maleimide (NH 2 -PEG-MAL) and absolute ethanol is 0.42:1.6:20. After fully stirring evenly, heat to reflux at 75°C and stir and react for 5h. After the reaction is completed, remove the solvent by vacuum distillation to obtain a modified grinding aid;

[0055] Step 3, add low-alkali cement clinker, Class I fly ash, gypsum and the modified grinding aid into a ball mill. The mass ratio of low-alkali cement clinker, fly ash, gypsum and the modified grinding aid is 100:10:12:0.5. The rotation speed of the ball mill is 80r / min and the grinding time is 40min for grinding treatment. After the grinding is completed, sieve. The residue rate on a 45μm square hole sieve is less than 5%, and the low-alkali frost-resistant portland cement is obtained.

[0056] The above application of the low-alkali frost-resistant portland cement in concrete for plateau regions, the concrete is calculated by weight parts and includes:

[0057] 100 parts of low-alkali frost-resistant portland cement, 354 parts of coarse aggregate, 526 parts of fine aggregate, 75 parts of fly ash, 56 parts of polyester fiber, 2.6 parts of high-range water reducer and 96 parts of water.

[0058] 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 fly ash is Class I fly ash; the polyester fiber is PTT fiber with a length of 5-8 mm and a diameter of 20±2 μm; the high-range water reducer is TH-928 polycarboxylate-based high-performance water reducer.

[0059] Comparative Example 1

[0060] A low-alkali portland cement, different from the preparation method of Example 1 in that the modified grinding aid is replaced with triethanolamine (traditional small molecule alcohol amine), and the rest is the same as Example 1.

[0061] Comparative Example 2

[0062] A low-alkali portland cement, different from the preparation method of Example 1 in that the modified grinding aid is replaced with allyl alcohol glycidyl ether, and the rest is the same as Example 1.

[0063] Comparative Example 3

[0064] A low-alkali portland cement, different from the preparation method of Example 1 in that the modified grinding aid is replaced with amino-polyethylene glycol-maleimide (NH 2 -PEG-MAL, Mw = 1000), and the rest is the same as Example 1.

[0065] Experimental detection

[0066] The low-alkali cements prepared in Example 1 of the present invention and Comparative Examples 1-3 are respectively used in concrete according to the method of Example 1, mixed and formed in a mold, and then after curing for 28 days, the performance of the concrete is detected.

[0067] Among them, the detection standards refer to:

[0068] (1) Compressive strength: GB / T 50081-2016, the detection includes the strength at 7d and 28d;

[0069] (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;

[0070] (3)Freezing resistance (rapid freezing method, freezing resistance grade): GB / T 50164-2009. The freezing resistance grades are divided into nine grades: F50, F100, F150, F200, F250, F300, F350, F400, and >F400. The larger the grade, the better the freezing resistance.

[0071] The experimental test results are shown in Table 1.

[0072]

[0073] It can be seen from the results in Table 1 that the 7-day and 28-day compressive strengths of the concrete prepared with the cement of Example 1 of the present invention are both higher than those of the comparative example, indicating better strength performance. In addition, the crack resistance grade and freezing resistance grade of Example 1 are also much better than those of the comparative example, indicating that the concrete prepared with the cement of Example 1 of the present invention has excellent crack resistance and freezing resistance on the basis of high strength, and is more suitable for plateau areas with high altitude and low temperature.

[0074] 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.

[0075] 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 method for preparing low-alkali antifreeze silicate cement for plateau areas, characterized in that: The following steps are involved: Step 1, weigh allyl alcohol glycidyl ether and add it into anhydrous ethanol, after fully dissolving, add 2,3-dimercaptopropanol, stir well again, add photoinitiator under the condition of nitrogen as protective gas, stir and react for 1-2h under the action of ultraviolet light, after the reaction is completed, remove the solvent under reduced pressure to obtain thioetherified glycidyl ether; Step 2, mixing thioetherified glycidyl ether and amino-polyethylene glycol-maleimide (NH2-PEG-MAL) in anhydrous ethanol, stirring well, heating to reflux, stirring to react for 2-5 hours, and after the reaction is completed, removing the solvent by distillation under reduced pressure to obtain a modified grinding aid; Step 3, adding low-alkali cement clinker, fly ash, gypsum and modified grinding aid into a ball mill for grinding. After the grinding is completed, the low-alkali antifreeze silicate cement is obtained by sieving.

2. The method for preparing low-alkali antifreeze silicate cement for plateau areas according to claim 1, characterized in that: In the step 1, the mass ratio of allyl alcohol glycidyl ether, 2,3-dimercaptopropanol and anhydrous ethanol is 1.4-2.8:0.6-1.2:40-60.

3. The method for preparing low-alkali antifreeze silicate cement for plateau areas according to claim 1, characterized in that: In the step 1, the photoinitiator is one of benzoin dimethyl ether, benzoin ethyl ether and benzoin butyl ether, and the amount of the photoinitiator added is 1.5%-5.5% of the mass of allyl alcohol glycidyl ether.

4. The method for preparing low-alkali antifreeze silicate cement for plateau areas according to claim 1, characterized in that: In the step 2, the mass ratio of thioetherified glycidyl ether, amino-polyethylene glycol-maleimide and anhydrous ethanol is 0.21-0.42:0.8-1.6:10-20; the weight average molecular weight of amino-polyethylene glycol-maleimide is 500-2000.

5. The method for preparing low-alkali antifreeze silicate cement for plateau areas according to claim 1, characterized in that: In the step 3, the rotation speed of the ball mill is 40-80 r / min, and the grinding time is 20-40 min; after sieving, the sieve residue rate of the low-alkali antifreeze silicate cement on the 45 μm square hole sieve is less than 5%.

6. The method for preparing low-alkali antifreeze silicate cement for plateau areas according to claim 1, characterized in that: In step 3, the mass ratio of low-alkali cement clinker, fly ash, gypsum and modified grinding aid is 100:6-10:6-12:0.1-0.

5.

7. A low-alkali antifreeze silicate cement for use in plateau areas, characterized in that: The preparation method according to claim 1 is used for preparation.

8. The use of low-alkali antifreeze silicate cement for plateau areas in concrete according to claim 7, characterized in that: Concrete is calculated by weight and includes: 100 parts of low-alkali frost-resistant silicate cement, 313-354 parts of coarse aggregate, 472-526 parts of fine aggregate, 55-75 parts of fly ash, 28-56 parts of polyester fiber, 1.3-2.6 parts of high-efficiency water reducer and 78-96 parts of water.

9. The use of low-alkali antifreeze silicate cement in concrete for plateau areas according to claim 8, characterized in that: The coarse aggregate is crushed stone or pebbles with a particle size of 5-10 mm, the fine aggregate is river sand or sea sand with a particle size of 0.16-4.5 mm; and the fly ash is Class I fly ash.

10. The use of low-alkali antifreeze silicate cement in concrete for plateau areas according to claim 8, wherein the high-efficiency water reducer is TH-928 polycarboxylic acid-based high-performance water reducer.

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