Steel slag-based magnesium phosphate cement rapid repair concrete at negative temperature and preparation method thereof

Abstract

The invention provides steel slag-based magnesium phosphate cement rapid repair concrete at negative temperature and a preparation method thereof, and the steel slag-based magnesium phosphate cement rapid repair concrete at negative temperature is prepared from the following raw materials in percentage by mass: 6.6%-11% of magnesium phosphate cement, 11%-15.4% of steel slag-based solid waste, 3.5%-3.8% of water, 0.9%-1.4% of borax, less than or equal to 1.2% of a composite antifreeze agent, 0.44%-0.48% of a polycarboxylate superplasticizer, 0.11%-0.12% of a polyether defoaming agent and 35%-40% of fine aggregate, and 31.8%-34.5% of limestone gravel coarse aggregate. Compared with an existing material, the working adaptability and the working performance of the magnesium phosphate cement concrete rapid repairing material can be remarkably improved, various construction working conditions are met, and the preparation cost is reduced; meanwhile, the magnesium phosphate cement is replaced by the solid waste cementing material, so that the environmental pollution can be reduced, and the sustainable development requirement is met; the river sand and the steel slag powder can jointly improve the stability and durability of the magnesium phosphate cement; the economic benefit and the social benefit of the material are obvious.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of repairing concrete, and particularly relates to a steel slag-based magnesium phosphate cement for repairing concrete at negative temperature and a preparation method. BACKGROUND

[0002] Steel slag is a by-product produced in the process of steel smelting, and its chemical composition shows that the steel slag has the potential to be used as a raw material for concrete production and road construction.

[0003] Fast repairing materials are widely used in various repairing projects due to their fast solidification and high early strength. There are various fast repairing materials for roads at home and abroad. According to the performance of the cementing materials, these materials can be divided into inorganic cement repairing materials, organic polymer repairing materials and inorganic-organic composite repairing materials. Among these materials, the inorganic cement repairing materials are favored due to their good compatibility with old concrete, high economy and environmental friendliness. Fast repairing materials mainly use fast-hardening and early-strength special cement, and common types include fast-hardening Portland cement, magnesium phosphate cement and high-alumina cement. These special cements are different in composition, hydration mechanism and application range. In particular, magnesium phosphate cement is widely used in emergency maintenance, construction and hazardous material handling due to its fast solidification speed, high early strength and wide applicability.

[0004] However, the traditional magnesium phosphate cement concrete fast repairing material has the disadvantages of large pollution, high cost and poor environmental adaptability. Therefore, developing a magnesium phosphate cement fast repairing concrete based on steel slag solid waste cementing material can not only effectively utilize industrial solid waste but also overcome the defects of existing materials, which has important practical significance and broad market prospects. SUMMARY

[0005] The technical problem to be solved by the present application is that the existing magnesium phosphate cement concrete fast repairing material has the disadvantages of large pollution, high cost and poor environmental adaptability, which leads to poor product performance under negative temperature conditions and cannot meet the relevant technical requirements.

[0006] In order to solve the above problems, the present application provides a steel slag-based magnesium phosphate cement for repairing concrete at negative temperature. The raw materials for preparing the steel slag-based magnesium phosphate cement for repairing concrete at negative temperature include, in terms of mass ratio, 6.6% to 11% of magnesium phosphate cement, 11% to 15.4% of steel slag-based solid waste, 3.5% to 3.8% of water, 0.9% to 1.4% of borax, ≤1.2% of composite anti-freezing agent, 0.44% to 0.48% of polycarboxylic acid water reducing agent, 0.11% to 0.12% of polyether defoaming agent, 35% to 40% of fine aggregate, and 31.8% to 34.5% of limestone crushed stone coarse aggregate.

[0007] The steel slag-based magnesium phosphate cement rapid concrete repair material provided by the application is based on acid-base neutralization reaction to generate phosphate complexes, and finally hardens to form MPC, and uses solid waste materials such as steel slag powder, slag, raw lime, desulfurization gypsum, etc., and the active ingredients in the steel slag powder and the slag react with MgO in the magnesium phosphate cement to form silicate and aluminate products. By optimizing the mixing ratio, a high-durability road rapid repair material capable of being constructed under negative temperature conditions, achieving traffic in 2h, 2h compressive strength > 35MPa, 28d compressive strength > 55Mpa, and no later strength reduction is prepared.

[0008] According to the above scheme of the application, the components of the steel slag-based solid waste include, in terms of mass ratio, 31%-43% of steel slag powder, 19%-27% of slag, 14%-20% of raw lime, 12.5%-17.5% of desulfurization gypsum, and 6.5%-9.5% of silica fume.

[0009] According to the above scheme of the application, the components of the steel slag-based solid waste include, in terms of mass ratio, 31%-43% of steel slag powder, 19%-27% of slag, 14%-20% of raw lime, 12.5%-17.5% of desulfurization gypsum, and 6.5%-9.5% of silica fume.

[0010] According to the above scheme of the application, the components of the fine aggregate include, in terms of mass ratio, 20%-60% of river sand and 40%-80% of steel slag aggregate.

[0011] According to the above scheme of the application, the components of the fine aggregate include, in terms of mass ratio, 40%-60% of river sand and 40%-60% of steel slag aggregate.

[0012] According to the above scheme of the application, the raw materials for preparing the steel slag-based magnesium phosphate cement rapid concrete repair material under negative temperature conditions include, in terms of mass ratio, 3.3%-6.1% of steel slag powder, 2.5%-3.5% of slag, 1.8%-2.6% of raw lime, 1.3%-2.5% of desulfurization gypsum, 0.9%-1% of silica fume, 6.6%-11% of magnesium phosphate cement, 3.5%-3.8% of water, 0.9%-1.4% of borax, ≤1.2% of composite anti-freezing agent, 0.44%-0.48% of polycarboxylic acid water reducing agent, 0.11%-0.12% of polyether defoaming agent, 35%-40% of fine aggregate, and 31.8%-34.5% of limestone coarse aggregate.

[0013] According to the above scheme of the application, the mass ratio of sodium nitrite, urea and sodium sulfate in the composite anti-freezing agent is sodium nitrite: urea: sodium sulfate = 60: (28-32): (8-12).

[0014] According to the above scheme of the application, the mass ratio of sodium nitrite, urea and sodium sulfate in the composite anti-freezing agent is sodium nitrite: urea: sodium sulfate = 60:30:10.

[0015] The mass percentage of the magnesium phosphate cement body: heavy-burning MgO: K2HPO4=3:1.

[0016] Based on the steel slag-based magnesium phosphate cement rapid repair concrete at negative temperature, the application further provides a method for preparing the steel slag-based magnesium phosphate cement rapid repair concrete at negative temperature, comprising the following steps: According to mass parts, 30.8-43.2 parts of steel slag powder, 19.1-26.9 parts of slag, 14.2-19.8 parts of raw lime, 12.5-17.5 parts of desulfurization gypsum and 6.7-9.4 parts of silica fume are fully mixed to prepare 100 parts of steel slag solid waste cementitious material; According to mass parts, 20-60 parts of river sand and 40-80 parts of steel slag aggregate are fully mixed to prepare fine aggregate; According to mass parts, 6.6-11 parts of magnesium phosphate cement, 11-15.4 parts of steel slag-based solid waste, 3.5-3.8 parts of water, 0.9-1.4 parts of borax, 0-1.2 parts of composite anti-freezing agent, 0.11-0.12 parts of polyether defoaming agent, 35-40 parts of fine aggregate and 31.8-34.5 parts of limestone coarse aggregate are added into a mixer, and fully hydrated until the freshly mixed concrete has good workability, so that the steel slag solid waste cementitious material-based magnesium phosphate cement rapid repair material is obtained.

[0017] The application has the following beneficial effects: 1. Environment-friendly and low cost: The rapid repair concrete material prepared by the application contains industrial solid waste materials such as steel slag sand, slag, raw lime, desulfurization gypsum and silica fume, which can reduce the use amount of magnesium phosphate cement, reduce the overall cost of the material, reduce carbon emissions, realize the high value-added utilization of industrial solid waste, and at the same time, due to the presence of steel slag sand in the material, the mechanical properties can still be maintained at a high level in the later period, and the durability of the material is improved. The method not only realizes the low-cost preparation of magnesium phosphate cement rapid repair concrete and the high-value utilization of industrial solid waste, but also solves the problem of strength reduction of the rapid repair concrete in the later period.

[0018] 2. Excellent mechanical properties: The rapid repair concrete prepared by the application has high mechanical strength, and the 2h compressive strength is not less than 35MPa, and the bending strength is not less than 5MPa; the 28d compressive strength can be not less than 55MPa, the bending strength can be more than 7MPa, and the bonding strength is greater than 2.5MPa. At the same time, the active components in the steel slag powder and the slag react with MgO in the magnesium phosphate cement to form silicates and aluminates, etc., to enhance the strength of the cement. The silicon dioxide and aluminum oxide in the raw lime can also react with the components in the cement to generate beneficial hydrates, thereby improving the cementing ability and impermeability of the cement. The addition of desulfurization gypsum can adjust the setting time of the cement, prevent premature setting, and ensure the stable growth of the cement in the hardening process.

[0019] 3. Good construction performance: the rapid repair material prepared by the application has a setting time controlled within 30 minutes, fast setting speed, high early strength, and can open traffic in 2 hours; the flow degree can reach more than 190 mm, the repaired surface is smooth and flat, and there are no defects such as cracks and pitted surface, and the incorporation of fly ash and steel slag powder helps to improve the fluidity of the fast repair cement concrete.

[0020] 4. In the application, the incorporation of the composite anti-freezing agent composed of Na2NO2, CO(NH2)2 and Na2SO4 can reduce the setting point of water in the cementitious material, so that the hydration reaction and acid-base neutralization reaction can still be carried out under negative temperature conditions, the strength under negative temperature conditions is realized, and the early performance of the concrete is improved; the incorporation of borax can delay the setting time of magnesium phosphate cement and improve the workability; the incorporation of polyether defoaming agent can eliminate harmful large bubbles generated during mixing, reduce the internal voids of the matrix, and improve the compactness and stability of the concrete.

[0021] 5. The material of the application effectively solves the problems of high cost, serious pollution, late strength reduction and many construction condition restrictions of the rapid repair concrete prepared mainly by magnesium phosphate cement.

[0022] 6. Compared with the existing materials, the application can significantly improve the work adaptability and work performance of the magnesium phosphate cement concrete rapid repair material, meet various construction conditions, reduce the preparation cost; at the same time, replacing magnesium phosphate cement with solid waste cementitious material can reduce environmental pollution and meet the requirements of sustainable development; river sand and steel slag powder together can improve the stability and durability of magnesium phosphate cement; the economic and social benefits of the material are remarkable. DETAILED DESCRIPTION

[0023] The embodiments of the technical scheme of the application will be described in detail below. The following embodiments are only used to more clearly illustrate the technical scheme of the application, and therefore only serve as examples, but cannot limit the protection scope of the application.

[0024] The rapid repair concrete on the current market generally has some challenges, such as high cost, late strength reduction and poor compatibility between materials, which limit their application range. In addition, industrial solid waste such as steel slag has not been effectively utilized, which not only occupies valuable land resources, but also causes damage to the ecological environment. On the other hand, the existing magnesium phosphate cement concrete rapid repair material has the disadvantages of serious pollution, high cost, and especially poor environmental adaptability, resulting in poor product performance under negative temperature conditions, which cannot meet the relevant technical requirements.

[0025] To solve these problems, the inventors of the present application have conducted in-depth research, explored the synergistic effect of industrial solid wastes such as steel slag and magnesium phosphate cement, and successfully developed a new type of rapid repair concrete. This concrete has excellent fluidity, can exhibit high strength in the later stage, has good durability, and can be constructed in low temperature environment. Through this innovative method, not only the cost of the repair concrete can be reduced, the later strength can be ensured, the durability can be improved, but also the industrial solid wastes such as steel slag can be converted into valuable resources, achieving efficient use of resources, thereby reducing the impact on the environment.

[0026] The implementation of the present application not only solves the existing problems of rapid repair concrete, but also provides a new solution for the treatment of industrial solid wastes, achieving higher economic and environmental benefits. This invention not only improves the added value of industrial solid wastes, but also contributes to resource conservation and environmental protection.

[0027] In the following examples, the specific surface area of the steel slag powder is 620-670 m 2 / kg, the specific surface area of the slag is 570-630 m 2 / kg, the specific surface area of the desulfurization gypsum is 360-450 m 2 / kg, the specific surface area of the silica fume is 370-490 m 2 / kg, and the specific surface area of the raw lime is 480-560 m 2 / kg.

[0028] In the following examples, the chemical composition of the steel slag powder is as follows: SiO2: 13%-19%, CaO: 31%-35%, Fe2O3: 22%-36%, MgO: 6%-8%, and the rest is impurities. The chemical composition of the slag is as follows: Al2O3: 12%-16%, SiO2: 24%-31%, CaO: 40%-44%, MgO: 7%-8%, and the rest is impurities. The chemical composition of the desulfurization gypsum is as follows: SO3: 39%-46%, CaO: 42%-47%, and the rest is impurities. The chemical composition of the raw lime is as follows: Al2O3: 30%-35%, SiO2: 40%-48%, CaO: 4%-13%, Fe2O3: 6%-7%, and the rest is impurities. The chemical composition of the silica fume is as follows: SiO2: 80%-90%, and the rest is ash powder. Since the composition of each particle of solid waste is not uniform, and the above-mentioned composition value range is already a small range value, the composition of each solid waste used is a small range of reasonable fluctuation value, which does not affect the product performance obtained by the person skilled in the art when implementing the present application.

[0029] In the following, the present application will be described by specific examples and comparative examples as follows: Example 1 S1, 126.5 kg of steel slag powder, 78.7 kg of slag, 58.1 kg of raw lime, 51.3 kg of desulfurization gypsum, 27.4 kg of silica fume were slowly stirred for 2 min and fully mixed to prepare 342 kg of steel slag solid waste cementitious material; S2, 520 kg of river sand and 520 kg of steel slag aggregate were fully mixed to prepare 1040 kg of fine aggregate; S3, 228 kg of magnesium phosphate cement, 29.6 kg of borax, 1040 kg of fine aggregate, 830 kg of limestone crushed stone coarse aggregate and 91.2 kg of water were put into a mixer and slowly stirred for 1 min; S4, a composite anti-freezing agent composed of 16.92 kg of sodium nitrite, 8.46 kg of urea, 2.82 kg of sodium sulfate, 2.9 kg of polyether defoaming agent and 11.4 kg of polycarboxylic acid water reducing agent were again incorporated and then fast stirred for 2 min to fully hydrate until the freshly prepared concrete had good workability to quickly repair the concrete.

[0030] Examples 2-7 differ from Example 1 in that the component proportions of each step are different, and the specific proportioning parameters of step S1 are shown in Table 1, and the specific proportioning parameters of steps S2-S4 are shown in Table 2.

[0031] Comparative Example 1 differs from Example 1 in that Comparative Example 1 does not contain borax, and the other components are the same as in Example 1, and the specific proportioning parameters are shown in Tables 1 and 2.

[0032] Comparative Example 2 differs from Example 1 in that Comparative Example 2 has less river sand, and the other components are the same as in Example 1, and the specific proportioning parameters are shown in Tables 1 and 2.

[0033] Comparative Example 3 differs from Example 1 in that Comparative Example 3 does not contain a composite anti-freezing agent, and the other components are the same as in Example 1, and the specific proportioning parameters are shown in Tables 1 and 2.

[0034] Comparative Example 4 differs from Example 1 in that Comparative Example 4 does not contain sodium nitrite in the composite anti-freezing agent, and the specific proportioning parameters are shown in Tables 1 and 2.

[0035] Comparative Example 5 differs from Example 1 in that Comparative Example 5 does not contain urea in the composite anti-freezing agent, and the specific proportioning parameters are shown in Tables 1 and 2.

[0036] Comparative Example 6 differs from Example 1 in that Comparative Example 6 does not contain sodium sulfate in the composite anti-freezing agent, and the specific proportioning parameters are shown in Tables 1 and 2.

[0037] Comparative Example 7 differs from Example 1 in that Comparative Example 7 has less steel slag powder and slag content in the steel slag-based solid waste, and the specific proportioning parameters are shown in Tables 1 and 2.

[0038] The difference between Comparative Example 8 and Example 1 is that the steel slag-based solid waste in Comparative Example 8 does not contain raw ash. The specific proportioning parameters are shown in Tables 1 and 2.

[0039] The difference between Comparative Example 9 and Example 1 is that the steel slag-based solid waste in Comparative Example 9 does not contain desulfurization gypsum. The specific proportioning parameters are shown in Tables 1 and 2.

[0040] The difference between Comparative Example 10 and Example 1 is that the steel slag-based solid waste in Comparative Example 10 is replaced by magnesium phosphate cement. The specific proportioning parameters are shown in Tables 1 and 2.

[0041] Table 1 shows the composition of the steel slag-based solid waste in each example and comparative example. Table 2 shows the composition of each step in each example and comparative example. The performance of the repair concrete prepared in the above examples and comparative examples was tested.

[0042] The initial setting time, final setting time, fluidity and stability were tested according to GB / T 1346-2011 Cement Standard Consistency Water Content, Setting Time, Stability Test Method.

[0043] The mechanical properties were tested according to GB / T 17671-1999 Cement Mortar Strength Test Method (ISO Method).

[0044] The repair concrete prepared in the above examples and comparative examples was poured into a fluidity test mold, molded in a 100mmx100mmx100mm concrete test mold, and placed in an environment of -5±2℃, RH=50±5% for curing to the required age. The performance was tested, and the test results are shown in Table 3.

[0045] The mechanical properties were tested using a testing machine, the compressive strength was tested at a loading rate of 2400N / s±200N / s, and the flexural strength was tested using a three-point bending method with a span of 100mm and a loading rate of 50N / s±5N / s.

[0046] Table 3 shows the normal temperature test index data of the repair concrete prepared in each example and comparative example. As can be seen from each example, comparative example, Table 3 and Table 4, the coagulation time of the rapid repair concrete obtained in Examples 1-7 under negative temperature conditions is appropriate, and the mechanical properties are good.

[0047] As can be seen from Comparative Example 1 and Example 1, in Comparative Example 1, due to the absence of borax, the setting is too fast under negative temperature conditions, the hydration is out of control, the internal porosity increases, the freezing damage intensifies, and finally the strength decreases.

[0048] It is seen from Comparative Example 2 and Example 1 that in Comparative Example 2, the river sand is insufficient, and the particle grading effect is poor. Under the condition of negative temperature, the insufficient river sand in Comparative Example 2 leads to poor aggregate grading, low density, weak frost resistance, and low mechanical strength.

[0049] It is seen from Comparative Example 3 and Example 1 that in Comparative Example 3, there is no frost-resistant agent, which causes water to freeze and expand under the condition of negative temperature, further destroys the microstructure, and causes slow early strength growth.

[0050] It is seen from Comparative Example 4 and Example 1 that in Comparative Example 4, sodium nitrite is lacking, which causes insufficient ice crystal inhibition under the condition of negative temperature, leads to reduced durability, and causes the mechanical properties of the product to decrease.

[0051] It is seen from Comparative Example 5 and Example 1 that in Comparative Example 5, there is no urea, which causes the hydration reaction rate to be too low under the condition of negative temperature, leads to slow early hydration and early strength growth.

[0052] It is seen from Comparative Example 6 and Example 1 that in Comparative Example 6, there is no sodium sulfate, which leads to insufficient alkali activation under the condition of negative temperature, and causes the late strength growth to be limited.

[0053] It is seen from Comparative Example 7 and Example 1 that in Comparative Example 7, there is no sodium sulfate, which leads to insufficient alkali activation under the condition of negative temperature, and causes the late strength growth to be slow.

[0054] It is seen from Comparative Example 8 and Example 1 that in Comparative Example 8, the steel slag and slag are insufficient, which causes poor structural density under the condition of negative temperature, significantly increases the porosity, and ultimately leads to a decrease in the mechanical properties of the product.

[0055] It is seen from Comparative Example 9 and Example 1 that in Comparative Example 9, there is no desulfurized gypsum, which leads to ineffective condensation regulation under the condition of negative temperature, causes the hydration products to be unevenly distributed, and ultimately leads to a decrease in the mechanical properties of the material.

[0056] It is seen from Comparative Example 10 and Example 1 that in Comparative Example 10, magnesium phosphate cement is used to replace the solid waste material, which causes the product interfacial transition zone to be weak under the condition of negative temperature, and ultimately leads to a decrease in the mechanical properties of the material.

[0057] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limiting. Although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for rapidly repairing concrete using steel slag-based magnesium phosphate cement at sub-zero temperatures, characterized in that... The raw materials for preparing the aforementioned steel slag-based magnesium phosphate cement rapid repair concrete at negative temperatures include, by mass proportion: Magnesium phosphate cement 6.6%~11%, steel slag-based solid waste 11%~15.4%, water 3.5%~3.8%, borax 0.9%~1.4%, composite antifreeze agent ≤1.2%, polycarboxylate superplasticizer 0.44%~0.48%, polyether defoamer 0.11%~0.12%, fine aggregate 35%~40%, limestone crushed stone coarse aggregate 31.8%~34.5%.

2. The rapid concrete repair method according to claim 1, characterized in that, The components of the steel slag-based solid waste, by mass percentage, include: steel slag powder 31%~43%, slag 19%~27%, raw ash 14%~20%, desulfurized gypsum 12.5%~17.5%, and silica fume 6.5%~9.5%.

3. The rapid concrete repair method according to claim 2, characterized in that, The steel slag-based solid waste comprises, by mass percentage: 37% steel slag powder, 23% slag, 17% raw ash, 15% desulfurized gypsum, and 8% silica fume.

4. The rapid concrete repair method according to claim 1, characterized in that, The fine aggregate composition, by mass percentage, includes: 20%~60% river sand and 40%~80% steel slag aggregate.

5. The rapid concrete repair method according to claim 1, characterized in that, The fine aggregate composition, by mass percentage, includes: 40%~60% river sand and 40%~60% steel slag aggregate.

6. The rapid concrete repair method according to claim 1, characterized in that, The raw materials for preparing the aforementioned steel slag-based magnesium phosphate cement rapid repair concrete at negative temperatures include, by mass proportion: Steel slag powder 3.3%~6.1%, blast furnace slag 2.5%~3.5%, raw ash 1.8%~2.6%, desulfurized gypsum 1.3%~2.5%, silica fume 0.9%~1%, magnesium phosphate cement 6.6%~11%, water 3.5%~3.8%, borax 0.9%~1.4%, composite antifreeze agent ≤1.2%, polycarboxylate superplasticizer 0.44%~0.48%, polyether defoamer 0.11%~0.12%, fine aggregate 35%~40%, limestone crushed stone coarse aggregate 31.8%~34.5%.

7. The rapid concrete repair method according to claim 1, characterized in that, The mass ratio of sodium nitrite, urea and sodium sulfate in the composite antifreeze is sodium nitrite: urea: sodium sulfate = 60: (28~32): (8~12).

8. The rapid concrete repair method according to claim 7, characterized in that, The mass ratio of sodium nitrite, urea, and sodium sulfate in the composite antifreeze is sodium nitrite:urea:sodium sulfate = 60:30:

10.

9. A method for preparing the rapid repair concrete according to any one of claims 1 to 8, characterized in that, include: 100 parts of steel slag solid waste cementitious material were prepared by thoroughly mixing 30.8-43.2 parts of steel slag powder, 19.1-26.9 parts of slag, 14.2-19.8 parts of raw ash, 12.5-17.5 parts of desulfurized gypsum, and 6.7-9.4 parts of silica fume according to the weight ratio. Fine aggregate is prepared by thoroughly mixing 20-60 parts river sand and 40-80 parts steel slag aggregate according to the weight ratio; According to the mass ratio, 6.6-11 parts of magnesium phosphate cement, 11-15.4 parts of steel slag-based solid waste, 3.5-3.8 parts of water, 0.9-1.4 parts of borax, 0-1.2 parts of composite antifreeze agent, 0.11-0.12 parts of polyether defoamer, 35-40 parts of fine aggregate, and 31.8-34.5 parts of limestone crushed stone coarse aggregate are added to a mixer and fully hydrated until the freshly mixed concrete has good workability, thus obtaining a rapid repair material based on magnesium phosphate cement and steel slag solid waste cementitious material.

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