Basic magnesium sulfate cement and preparation method thereof
阅读说明：本技术 一种碱式硫酸镁水泥及其制备方法 (Basic magnesium sulfate cement and preparation method thereof ) 是由 余红发 吴成友 宗京平 罗轲嘉 巩旭 寇西湖 麻海燕 于 2020-12-24 设计创作，主要内容包括：本发明公开了一种碱式硫酸镁水泥,包括以下组份：100质量份的活性氧化镁粉、30～100质量份的硫酸镁溶液、0.01～0.05质量份的外加剂和0.1～5质量份的硫氧化镁晶体成核剂,其中硫酸镁溶液为结晶硫酸镁的水溶液,其质量分数为15-20％；所述硫氧化镁晶体成核剂采用以下方法制备：步骤一、将50～100质量份活性MgO质量分数为55％～85％的轻烧菱镁粉、70～300质量份质量分数为10％～25％的硫酸镁溶液、0.01～0.05质量份磷酸混合；步骤二、步骤一所得糊状物,放入密封袋中,并在20±3℃下固化28天,以促进硬化,最后通过球磨将硬化后的样品研磨成粉得到事实硫氧化镁晶体成核剂。本发明具有凝结时间短、早强高强等优点。(The invention discloses basic magnesium sulfate cement, which comprises the following components: 100 parts by mass of active magnesium oxide powder, 30-100 parts by mass of magnesium sulfate solution, 0.01-0.05 part by mass of admixture and 0.1-5 parts by mass of magnesium oxysulfide crystal nucleating agent, wherein the magnesium sulfate solution is an aqueous solution of crystallized magnesium sulfate, and the mass fraction of the magnesium sulfate solution is 15-20%; the magnesium oxysulfide crystal nucleating agent is prepared by the following method: mixing 50-100 parts by mass of light-burned magnesite powder with active MgO mass fraction of 55-85%, 70-300 parts by mass of magnesium sulfate solution with mass fraction of 10-25% and 0.01-0.05 part by mass of phosphoric acid; and step two, putting the paste obtained in the step one into a sealed bag, curing for 28 days at the temperature of 20 +/-3 ℃ to promote hardening, and finally grinding the hardened sample into powder by ball milling to obtain the actual magnesium oxysulfide crystal nucleating agent. The invention has the advantages of short coagulation time, early strength, high strength and the like.)
1. The basic magnesium sulfate cement is characterized in that:
comprises the following components: 100 parts by mass of active magnesium oxide powder, 30-100 parts by mass of magnesium sulfate solution, 0.01-0.05 part by mass of admixture and 0.1-5 parts by mass of magnesium oxysulfide crystal nucleating agent, wherein the magnesium sulfate solution is an aqueous solution of crystallized magnesium sulfate, and the mass fraction of the magnesium sulfate solution is 15-20%;
the magnesium oxysulfide crystal nucleating agent is prepared by the following method:
mixing 50-100 parts by mass of light-burned magnesite powder with active MgO mass fraction of 55-85%, 70-300 parts by mass of magnesium sulfate solution with mass fraction of 10-25% and 0.01-0.05 part by mass of phosphoric acid;
and step two, putting the paste obtained in the step one into a sealed bag, curing for 28 days at the temperature of 20 +/-3 ℃ to promote hardening, and finally grinding into powder to obtain the actual magnesium oxysulfide crystal nucleating agent.
2. The basic magnesium sulfate cement of claim 1, wherein:
wherein the main component of the magnesium oxysulfide crystal nucleating agent is mMg (OH)2·MgSO4·nH2O, wherein m represents Mg (OH)2And MgSO4In a molar ratio of (A), n represents H2O and MgSO4M is in the range of 1 to 5, and n is in the range of 2 to 8.
3. The basic magnesium sulfate cement of claim 2, wherein:
wherein m ranges from 3 to 5, and n ranges from 3 to 7.
4. The basic magnesium sulfate cement of claim 1, wherein:
wherein the active magnesium oxide powder is active magnesium oxide powder with active MgO mass fraction of 55-75%.
5. The basic magnesium sulfate cement of claim 1, wherein:
wherein the crystalline magnesium sulfate is one or a mixture of more of magnesium sulfate heptahydrate, magnesium sulfate pentahydrate, magnesium sulfate trihydrate and magnesium sulfate monohydrate.
6. The basic magnesium sulfate cement of claim 1, wherein:
wherein the additive is phosphoric acid or phosphate.
7. The basic magnesium sulfate cement of claim 6, wherein:
wherein the phosphate is one of potassium dihydrogen phosphate, sodium dihydrogen phosphate or ammonium dihydrogen phosphate.
8. A method of preparing basic magnesium sulphate cement according to any one of claims 1 to 7 wherein:
weighing active magnesium oxide powder, an additive and a magnesium oxysulfide crystal nucleating agent according to a ratio, mixing and grinding the components, sieving the mixture with a 100-200-mesh sieve, and mixing and hardening the mixture with a magnesium sulfate solution calculated according to a ratio to obtain the basic magnesium sulfate cement.
Technical Field
The invention belongs to the field of building materials, relates to cement, and particularly relates to basic magnesium sulfate cement and a preparation method thereof.
Background
MgO-MgSO4-H2The O-cement is an inorganic gelled material produced by mixing magnesium oxide and magnesium sulfate solution and adding a certain additive, belongs to an air-hardening magnesium material, and the main hydration product of the material is 3Mg (OH)2·MgSO4·8H2O (abbreviation 3.1.8). Currently aimed at MgO-MgSO4-H2The modification technology of O ternary gelation system mainly adopts retarders of organic carboxylic acid and the like to obtain basic magnesium sulfate cement with excellent performance, and its main hydration product is 5Mg (OH)2·MgSO4·7H2O (abbreviated as 5.1.7). The addition of these additives improves the strength and volume stability of the basic magnesium sulfate cement by changing the composition of its hydrated phase. Although the later strength of basic magnesium sulfate cement is high, the delayed coagulation effect based on the additive causes the product to be slowly hardened, the final coagulation time at room temperature is generally more than 6h, and the 1-day strength is also much lower than that of magnesium oxychloride cement, which brings very troublesome problems to the production efficiency and scale production of basic magnesium sulfate cement products.
The traditional inorganic electrolytes (such as sodium chloride, sodium sulfate, aluminum sulfate and the like), triethanolamine, formate and other early strength agents used in portland cement-based materials cannot accelerate the setting rate of basic magnesium sulfate cement systems, and can continuously prolong the setting time. In order to fundamentally solve the problem of slow coagulation of basic magnesium sulfate cement and not to cause adverse effects on later strength, durability and workability of construction, a new modification method must be found. The addition of nucleating agents is an effective way to improve the early strength of the cement. With respect to the application of nucleating agents to various cementitious materials, the current reports mainly include the use of portland cement-based materials, phosphate cements, and magnesium oxychloride cements.
Disclosure of Invention
The present application adopts a method of adding a magnesium oxysulfide crystal nucleating agent to further reduce the activation energy (or potential barrier) of 5.1.7 phase nucleation crystal and provide a place for epitaxial growth thereof to accelerate the 5.1.7 phase formation rate, improve the coagulation time or early strength thereof, and further improve the production efficiency thereof. The basic magnesium sulfate cement provided by the invention has the advantages that the early and later strength and the setting and hardening speed of the cement are obviously improved, and the production efficiency of basic magnesium sulfate cement preparation can be improved.
In order to achieve the above object, the present invention provides a basic magnesium sulfate cement having the following features:
comprises the following components: 100 parts by mass of active magnesium oxide powder, 30-100 parts by mass of magnesium sulfate solution, 0.01-0.05 part by mass of admixture and 0.1-5 parts by mass of magnesium oxysulfide crystal nucleating agent, wherein the magnesium sulfate solution is an aqueous solution of crystallized magnesium sulfate, and the mass fraction of the magnesium sulfate solution is 15-20%;
the magnesium oxysulfide crystal nucleating agent is prepared by the following method:
mixing 50-100 parts by mass of light-burned magnesite powder with active MgO mass fraction of 55-85%, 70-300 parts by mass of magnesium sulfate solution with mass fraction of 10-25% and 0.01-0.05 part by mass of phosphoric acid;
and step two, putting the paste obtained in the step one into a sealed bag, curing for 28 days at the temperature of 20 +/-3 ℃ to promote hardening, and finally grinding the hardened sample into powder by ball milling to obtain the actual magnesium oxysulfide crystal nucleating agent.
Further, the present invention provides a basic magnesium sulfate cement, which may further have the following characteristics: wherein the main component of the magnesium oxysulfide crystal nucleating agent is mMg (OH)2·MgSO4·nH2O, wherein m represents Mg (OH)2And MgSO4In a molar ratio of (A), n represents H2O and MgSO4M is in the range of 1 to 5, and n is in the range of 2 to 8.
Further, the present invention provides a basic magnesium sulfate cement, which may further have the following characteristics: wherein m ranges from 3 to 5, and n ranges from 3 to 7.
Further, the present invention provides a basic magnesium sulfate cement, which may further have the following characteristics: wherein the active magnesium oxide powder is active magnesium oxide powder with active MgO mass fraction of 55-75%.
Further, the present invention provides a basic magnesium sulfate cement, which may further have the following characteristics: wherein the crystalline magnesium sulfate is one or a mixture of more of magnesium sulfate heptahydrate, magnesium sulfate pentahydrate, magnesium sulfate trihydrate and magnesium sulfate monohydrate.
Further, the present invention provides a basic magnesium sulfate cement, which may further have the following characteristics: wherein the additive is phosphoric acid or phosphate.
Further, the present invention provides a basic magnesium sulfate cement, which may further have the following characteristics: wherein the phosphate is one of potassium dihydrogen phosphate, sodium dihydrogen phosphate or ammonium dihydrogen phosphate.
The invention also provides a preparation method of the basic magnesium sulfate cement, which is characterized in that: weighing active magnesium oxide powder, an additive and a magnesium oxysulfide crystal nucleating agent according to a ratio, mixing and grinding the components, sieving the mixture with a 100-200-mesh sieve, and mixing and hardening the mixture with a magnesium sulfate solution calculated according to a ratio to obtain the basic magnesium sulfate cement.
The invention has the beneficial effects that:
firstly, the traditional preparation of basic magnesium sulfate cement has the characteristic of slow setting, and the invention obviously improves the setting and hardening speed of the basic magnesium sulfate cement by introducing the magnesium oxysulfide crystal nucleating agent and a proper additive to mutually promote, and can improve the production efficiency of the basic magnesium sulfate cement.
The volume shrinkage of the basic magnesium sulfate cement can be effectively controlled by introducing the magnesium oxysulfide crystal nucleating agent, the cracking risk is reduced by over 90 percent, and the cracking is effectively prevented.
The magnesium oxysulfide crystal nucleating agent is added to provide an in-situ growth point for the main hydration product of the basic magnesium sulfate cement, and the basic magnesium sulfate cement has the characteristics of quick condensation and high strength, such as high early strength and no reverse shrinkage of later strength.
Drawings
FIGS. 1a and b are XRD test charts of hydration products of basic magnesium sulfate cement hardened bodies of the present invention using a magnesium oxysulfide crystal nucleating agent.
Detailed Description
The present invention is further illustrated by the following specific examples.
Example 1
This example provides the preparation of basic magnesium sulfate cement:
preparation of a magnesium oxysulfide crystal nucleating agent:
mixing 100 parts of light-burned magnesite powder with the active MgO mass fraction of 55%, 0.05 part of phosphoric acid and 143 parts of magnesium sulfate solution with the mass fraction of 20%; the resulting paste was placed in a sealed bag and cured at 20 + -3 deg.C for 28 days to promote hardening. Finally, grinding the hardened sample into powder by ball milling to obtain the magnesium oxysulfide crystal nucleating agent, mainly comprising Mg (OH)2·MgSO4·5H2O(1·1·5)。
Preparation of basic magnesium sulfate cement:
100 parts of active magnesium oxide powder with the active MgO mass fraction of 55%, 0.01 part of monopotassium phosphate and 1 part of 1, 1 and 5 sulfur magnesium oxide crystal nucleating agent are mixed and ground, then the mixture is sieved by a 100-mesh sieve, and the mixture is mixed with 100 parts of 20 wt% magnesium sulfate heptahydrate solution and hardened to obtain the high-alkali magnesium sulfate cement. XRD test patterns of hydration products of cement hardened bodies are shown in figures 1a and b.
Example 2
This example provides the preparation of basic magnesium sulfate cement:
preparation of a magnesium oxysulfide crystal nucleating agent:
mixing 100 parts of light-burned magnesite powder with the active MgO mass fraction of 62%, 0.05 part of phosphoric acid and 106.2 parts of magnesium sulfate solution with the mass fraction of 20%; the resulting paste was placed in a sealed bag and cured at 20 + -3 deg.C for 28 days to promote hardening. Finally, grinding the hardened sample into powder by ball milling to obtain the magnesium oxysulfide crystal nucleating agent, which mainly comprises 2Mg (OH)2·MgSO4·3H2O(2·1·3)。
Preparation of basic magnesium sulfate cement:
100 parts of active magnesium oxide powder with the active MgO mass fraction of 75%, 0.03 part of sodium dihydrogen phosphate and 3 parts of 2, 1 and 3 parts of magnesium oxysulfide crystal nucleating agent are mixed and ground, then the mixture is sieved by a 100-mesh sieve, and the mixture is mixed with 94 parts of 20 wt% magnesium sulfate pentahydrate solution and hardened to obtain the high-alkali magnesium sulfate cement.
Example 3
This example provides the preparation of basic magnesium sulfate cement:
preparation of a magnesium oxysulfide crystal nucleating agent:
mixing 100 parts of light-burned magnesite powder with active MgO mass fraction of 68%, 0.05 part of phosphoric acid and 300 parts of magnesium sulfate solution with mass fraction of 20%; the resulting paste was placed in a sealed bag and cured at 20 + -3 deg.C for 28 days to promote hardening. Finally, grinding the hardened sample into powder by ball milling to obtain the magnesium oxysulfide crystal nucleating agent, which mainly comprises 3Mg (OH)2·MgSO4·8H2O(3·1·8)。
Preparation of basic magnesium sulfate cement:
100 parts of active magnesium oxide powder with the active MgO mass fraction of 64 percent, 0.05 part of ammonium dihydrogen phosphate and 5 parts of 3.1.8 sulfur magnesium oxide crystal nucleating agent are mixed and ground, then the mixture is sieved by a 100-mesh sieve, and the mixture is mixed and hardened with 73 parts of 20wt percent trihydrate magnesium sulfate solution to obtain the high-alkali magnesium sulfate cement.
Example 4
This example provides the preparation of basic magnesium sulfate cement:
preparation of a magnesium oxysulfide crystal nucleating agent:
mixing 100 parts of light-burned magnesite powder with active MgO mass fraction of 74%, 0.05 part of phosphoric acid and 102.1 parts of magnesium sulfate solution with mass fraction of 20%; the resulting paste was placed in a sealed bag and cured at 20 + -3 deg.C for 28 days to promote hardening. Finally, grinding the hardened sample into powder by ball milling to obtain the magnesium oxysulfide crystal nucleating agent, which mainly comprises 5Mg (OH)2·MgSO4·7H2O(5·1·7)。
Preparation of basic magnesium sulfate cement:
100 parts of active magnesium oxide powder with the active MgO mass fraction of 69%, 0.05 part of phosphoric acid and 5 parts of 5.1.7 sulfur magnesium oxide crystal nucleating agent are mixed and ground, then the mixture is sieved by a 100-mesh sieve, and the mixture is mixed and hardened with 64 parts of 20 wt% magnesium sulfate monohydrate solution to obtain the high-alkali magnesium sulfate cement.
Example 5
This example provides the preparation of basic magnesium sulfate cement:
preparation of a magnesium oxysulfide crystal nucleating agent:
mixing 100 parts of light-burned magnesite powder with active MgO mass fraction of 85%, 0.05 part of phosphoric acid and 300 parts of magnesium sulfate solution with mass fraction of 20%; the resulting paste was placed in a sealed bag and cured at 20 + -3 deg.C for 28 days to promote hardening. Finally, grinding the hardened sample into powder by ball milling to obtain the magnesium oxysulfide crystal nucleating agent, which mainly comprises 5Mg (OH)2·1MgSO4·5H2O(5·1·5)。
Preparation of basic magnesium sulfate cement:
100 parts of active magnesium oxide powder with the active MgO mass fraction of 59 percent, 0.05 part of phosphoric acid and 5 parts of 5.1.5 sulfur magnesium oxide crystal nucleating agent are mixed and ground, then the mixture is sieved by a 100-mesh sieve, and the mixture is mixed and hardened with 85 parts of 20 wt% magnesium sulfate trihydrate and magnesium sulfate pentahydrate solution (the mass ratio of the magnesium sulfate trihydrate to the magnesium sulfate pentahydrate is 1:2) to obtain the high-alkali magnesium sulfate cement.
Example 6
This example provides the preparation of basic magnesium sulfate cement:
preparation of a magnesium oxysulfide crystal nucleating agent:
mixing 100 parts of light-burned magnesite powder with active MgO mass fraction of 85%, 0.01 part of phosphoric acid and 300 parts of magnesium sulfate solution with mass fraction of 10%; the resulting paste was placed in a sealed bag and cured at 20 + -3 deg.C for 28 days to promote hardening. Finally, grinding the hardened sample into powder by ball milling to obtain the magnesium oxysulfide crystal nucleating agent, which mainly comprises 5Mg (OH)2·MgSO4·6H2O(5·1·6)。
Preparation of basic magnesium sulfate cement:
100 parts of active magnesium oxide powder with the active MgO mass fraction of 59 percent, 0.05 part of sodium dihydrogen phosphate and 0.1 part of 5.1.6 sulfur magnesium oxide crystal nucleating agent are mixed and ground, then the mixture is sieved by a 200-mesh sieve, and the mixture is mixed with 8515 wt percent of trihydrate magnesium sulfate solution to be hardened to obtain the high-alkali magnesium sulfate cement.
Example 7
This example provides the preparation of basic magnesium sulfate cement:
preparation of a magnesium oxysulfide crystal nucleating agent:
mixing 75 parts of light-burned magnesite powder with active MgO of which the mass fraction is 70 percent, 0.03 part of phosphoric acid and 70 parts of magnesium sulfate solution with the mass fraction being 25 percent; the resulting paste was placed in a sealed bag and cured at 20 + -3 deg.C for 28 days to promote hardening. Finally, grinding the hardened sample into powder by ball milling to obtain the magnesium oxysulfide crystal nucleating agent, which mainly comprises 5Mg (OH)2·MgSO4·3H2O(5·1·3)。
Preparation of basic magnesium sulfate cement:
100 parts of active magnesium oxide powder with the active MgO mass fraction of 59 percent, 0.03 part of phosphoric acid and 2.5 parts of 5.1.3 sulfur magnesium oxide crystal nucleating agent are mixed and ground, then the mixture is sieved by a 200-mesh sieve, and the mixture is mixed with 95 parts of 15wt percent magnesium sulfate heptahydrate solution to be hardened to obtain the high-alkali magnesium sulfate cement.
Example 8
This example provides the preparation of basic magnesium sulfate cement:
preparation of a magnesium oxysulfide crystal nucleating agent:
mixing 50 parts of light-burned magnesite powder with active MgO mass fraction of 85%, 0.02 part of phosphoric acid and 70 parts of magnesium sulfate solution with mass fraction of 25%; the resulting paste was placed in a sealed bag and cured at 20 + -3 deg.C for 28 days to promote hardening. Finally, grinding the hardened sample into powder by ball milling to obtain the magnesium oxysulfide crystal nucleating agent, which mainly comprises 5Mg (OH)2·MgSO4·2H2O(5·1·2)。
Preparation of basic magnesium sulfate cement:
100 parts of active magnesium oxide powder with the active MgO mass fraction of 59 percent, 0.05 part of phosphoric acid and 1.5 parts of 5.1.2 sulfur magnesium oxide crystal nucleating agent are mixed and ground, then the mixture is sieved by a 200-mesh sieve, and the mixture is mixed with 71 parts of 15wt percent magnesium sulfate heptahydrate solution to be hardened to obtain the high-alkali magnesium sulfate cement.
Comparative example
100 parts of active magnesium oxide powder with the active MgO mass fraction of 65%, 0.5 part of phosphoric acid and 102 parts of magnesium sulfate aqueous solution with the mass fraction of 20% are mixed to obtain the basic magnesium sulfate cement.
Basic performance tests of the cement were carried out for each of the examples and comparative examples, and the results are shown in the following table:
the table shows that the final setting time of the basic magnesium sulfate cement prepared by the method is greatly shortened, the strength of 1 day is greatly improved compared with that of the basic magnesium sulfate cement prepared in a comparative proportion, and the strength of 28 days is correspondingly improved. After the magnesium oxysulfide crystal nucleating agent is added, the initial setting time of the cement can be obviously shortened, which shows that the addition of the magnesium oxysulfide crystal nucleating agent can accelerate the formation speed of early hydration products. Meanwhile, considering the influence of the magnesium oxysulfide crystal nucleating agent on the early strength of the basic magnesium sulfate cement, the addition of the magnesium oxysulfide crystal nucleating agent under the condition of low additive content (such as 0.05 percent) can obviously improve the production efficiency of cement products. Therefore, the basic magnesium sulfate cement prepared by the invention has the characteristics of short setting time, early strength and high strength, and can improve the production efficiency of basic magnesium sulfate cement products, improve the quality of the products and reduce the generation cost of the products.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
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