An anti-erosion expansive anti-cracking agent for concrete and a preparation method thereof

Abstract

The application discloses an anti-erosion expansion anti-cracking agent for concrete and a preparation method thereof, and belongs to the field of admixtures for building materials. The anti-erosion expansion anti-cracking agent comprises the following raw materials: modified expansion clinker, low-activity magnesium oxide expansion agent, semi-dense silica fume, alumina ceramic micro powder, modified hydration heat regulating material, water reducing agent, shrinkage reducing agent and perlite. The preparation method of the modified expansion clinker is as follows: under the stirring state, a surface modifier with a mass fraction of 2% to 4% of the expansion clinker is sprayed into the expansion clinker, the surface modifier comprises a polymer solution and polyvinyl alcohol, and the polymer solution comprises at least one of styrene-acrylate emulsion or butadiene-styrene emulsion. The preparation method of the modified hydration heat regulating material is as follows: an acid catalyst is added to dry starch in a spraying mode. The anti-erosion expansion anti-cracking agent has the characteristics of reducing the hydration temperature rise of concrete, slowing down the autogenous shrinkage and drying shrinkage, continuously expanding slightly, improving the anti-erosion effect of concrete and the like, and can significantly improve the anti-erosion strength of the concrete.

Description

Technical Field

[0001] This invention belongs to the field of building material admixtures, specifically relating to an anti-erosion, expansion and crack-resistant agent for concrete and its preparation method. Background Technology

[0002] High-speed, sediment-laden water flow causes prolonged erosion damage to the overflow surfaces, spillways, stilling basins, and aprons of hydraulic concrete structures. This results in pitting and scarring on the surface, and in severe cases, large areas of wall spalling and exposed rebar. This significantly shortens the lifespan of the structures and can even compromise project safety. The root cause of this erosion damage is the presence of various defects and weak abrasion-resistant areas at the interface between cement and aggregate. By incorporating anti-erosion admixtures, the erosion resistance of concrete can be improved, effectively enhancing the anti-erosion performance of hydraulic concrete.

[0003] The current main approach to improving the impact and abrasion resistance of concrete is to increase its density and strength. The main components of impact and abrasion agents are ultrafine active silica fume, fly ash, mineral powder and other ultrafine materials with pozzolanic activity or hydration activity. While pursuing high early strength, the addition of these materials generally leads to an increase in the internal temperature of the concrete in the early stage, which increases the thermal shrinkage and autogenous shrinkage of the concrete, and increases the risk of concrete cracking. The side effects are obvious and difficult to solve, which has always been a problem that needs to be solved in the process of engineering construction.

[0004] Chinese Patent No. CN108298859B discloses a concrete impact abrasion resistant agent and its preparation method. Its composition, by mass percentage, includes the following components: nano-oxide particles: 2%–10%; silicon carbide: 5%–15%; shrinkage-reducing component: 5%–40%; dispersing component: 5%–10%; stabilizing component: 0.05%–0.2%; defoamer and stabilizer: 0–0.5%; the balance being water. This agent can increase the impact abrasion resistance of concrete by 40%–60% or more, significantly improving its impact abrasion resistance. Simultaneously, it effectively improves the workability of concrete. Adding this impact abrasion resistant agent to concrete provides reinforcement and abrasion resistance; however, the addition of nano-oxide particles leads to significant concrete shrinkage. Simply using polyether or polyol shrinkage-reducing agents to physically reduce the surface tension between cement particles cannot effectively compensate for concrete shrinkage, easily causing cracking in the impact abrasion resistant concrete.

[0005] Chinese Patent No. CN107298539 B discloses a high-efficiency impact-resistant and wear-resistant agent for concrete and its preparation method. The mass percentages of each component are as follows: modified calcium oxide: 14.5~29.0 wt%, modified magnesium oxide: 10.5~21.0 wt%, corundum: 30.0~69.0 wt%, mullite: 1.0~5.0 wt%, and ultrafine silica: 5.0~15.0 wt%. The preparation method involves adding calcium stearate to a calcium-magnesium composite expansion material obtained by low-temperature calcination of dolomite and bauxite, along with corundum and mullite, and then reacting it with ultrafine silica. The calcium and magnesium composite expansion material is prepared by surface treatment to inhibit the hydration of calcium and magnesium expansion materials in the plastic stage and improve the compensation shrinkage efficiency in the hardening stage. However, the surface treatment method of calcium and magnesium composite expansion material is to coat the surface with stearic acid, which is only coated by mixing and grinding. The coating effect is not good and fails to achieve the purpose of surface treatment. This affects the reaction process of calcium and magnesium composite expansion material, makes it difficult to guarantee effective compensation in the hardening stage of concrete, and fails to achieve the purpose of crack resistance.

[0006] Chinese Patent No. CN119898985 A discloses a concrete crack-resistant agent suitable for high-temperature environments and its preparation method, comprising the following components by mass percentage: 45%~65% calcium oxide expanding material, 30%~45% magnesium oxide expanding material, 1.5%~5% hydration heat regulating material, with the balance being gypsum and fly ash in any proportion. This agent can effectively suppress the hydration heat release rate of cement concrete at various temperatures, effectively reducing the temperature rise of concrete under various working conditions, including high-temperature environments, and the risk of temperature shrinkage and cracking caused by temperature rise. However, the calcium oxide expanding reaction is too fast, and a large amount of expansion is consumed during the plastic stage of concrete, failing to compensate for shrinkage. The hydration heat regulating material contains a large amount of water during preparation, and starch easily precipitates and clumps, easily causing localized gelatinization, which is detrimental to the reaction. Some wastewater is generated, and subsequent drying or grinding requires specialized equipment, making the operation complex and energy-intensive.

[0007] In the aforementioned technologies, the concrete impact and abrasion resistance agents primarily aim to increase the strength of the matrix, thereby achieving impact and abrasion resistance. However, this method results in significant concrete shrinkage, easily leading to cracking. Although polyether shrinkage reducers, polyol shrinkage reducers, or surface-treated calcium-magnesium composite expansion agents are added to offset concrete shrinkage, economic and technological limitations make it difficult to guarantee crack resistance. Furthermore, the preparation of hydration heat-regulating materials generates wastewater, and subsequent drying or grinding requires specialized equipment, making the operation complex and energy-intensive. Therefore, it is urgent to address these issues and optimize the impact and abrasion resistance and crack resistance of concrete to ensure effective application. Summary of the Invention

[0008] To address the shortcomings of the existing technology, one of the objectives of this invention is to provide an anti-erosion expansion and crack-resistant agent for concrete. This anti-erosion expansion and crack-resistant agent has the characteristics of reducing the internal hydration temperature rise of concrete structures, slowing down the autogenous shrinkage and drying shrinkage of concrete, continuous micro-expansion, and improving the anti-erosion effect of concrete. It also has good compatibility with cement, improves the workability and density of concrete, and can significantly improve the erosion and abrasion resistance of hydraulic concrete.

[0009] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0010] An anti-erosion and anti-cracking agent for concrete comprises the following raw materials in the following weight percentages: 30%~50% modified expansive clinker, 20%~40% low-activity magnesium oxide expansive agent, 10%~30% semi-dense silica fume, 10%~20% alumina ceramic powder, 1%~5% modified hydration heat regulating material, 1%~5% water-reducing agent, 0.2%~1% shrinkage reducing agent, and 1%~5% perlite;

[0011] The modified expanded clinker is prepared by the following method: 2% to 4% of the clinker mass of surface modifier is sprayed into the calcium oxide-calcium sulfoaluminate dual expansion source expanded clinker under stirring. After stirring evenly, it is allowed to stand for 1 to 2 days and then sieved to obtain the modified expanded clinker. The surface modifier includes a polymer solution and polyvinyl alcohol. The polymer solution includes at least one of styrene-acrylate emulsion or styrene-butadiene emulsion.

[0012] The modified hydration heat regulating material is prepared by the following method:

[0013] P1. Under stirring, add 3% to 8% of the starch mass of acid catalyst to the dry starch by spraying, stir at 40 to 60°C for 0.5 to 2 hours, then raise the temperature to 120 to 150°C and continue stirring for 1 to 3 hours. Finally, add alkaline solution by spraying to neutralize until the starch pH value is 5 to 6.

[0014] P2. Continue stirring the neutralized starch until the temperature drops to room temperature, then sieve to obtain starch with a particle size of 30~100μm, thus obtaining the modified hydration heat control material.

[0015] The anti-erosion expansion and crack-resistant agent of the present invention compensates for concrete shrinkage through an expansion component, reduces concrete temperature shrinkage through a hydration heat regulating component, reduces concrete autogenous shrinkage through a shrinkage-reducing component, enhances the density of the concrete matrix through semi-dense silica fume and perlite via micro-aggregate and pozzolanic effects, and enhances the wear resistance of the concrete matrix through alumina ceramic micropowder. In addition, the components of the present invention have a synergistic effect; the hydration heat regulating component can promote the expansion effect of the expansion component, and at the same time, can synergistically improve the erosion resistance of concrete. Under the synergistic effect of the above components, the crack resistance and erosion resistance of concrete are comprehensively improved.

[0016] This invention modifies the surface of calcium oxide-calcium sulfoaluminate dual-expansion-source expanded clinker using a surface modifier. The modifier has excellent adhesion and can be rapidly adsorbed onto the clinker surface and solidified in a short time after contact with the expanded clinker, thus encapsulating the clinker and making the clinker surface somewhat hydrophobic. This reduces the contact area between the clinker and water, slows down the reaction time of the expanded clinker, reduces ineffective expansion of the expanded clinker in the plastic stage of concrete, improves the effective expansion energy of the expanded clinker, and enhances the compensating shrinkage effect of concrete during the hardening process. At the same time, the introduced low-activity magnesium oxide expanding agent has the characteristic of delayed micro-expansion, and the expansion rate matches the rate of concrete shrinkage, offsetting the volume shrinkage during the cooling process. It can continuously generate expansion energy throughout the entire life cycle of concrete, effectively compensating for concrete shrinkage.

[0017] This invention employs a dry process to acidify and modify starch to prepare a modified hydration heat-regulating material. By spraying, the acid catalyst and starch are thoroughly mixed, reducing starch agglomeration and ensuring more uniform mixing. First, the starch and acid catalyst undergo a preliminary reaction at 40-60°C, allowing the acid catalyst to act on the loosely arranged amorphous and crystalline surface defects of the starch particles. Then, the temperature is raised to 120-150°C, where the acid catalyst fully attacks the α-1,6-glycosidic bonds of the starch, separating the starch branches from the starch macromolecules, reducing the degree of polymerization, and decomposing long-chain macromolecules into short-chain small molecules. This reduces the retarding effect of long-chain macromolecules on cement-based material systems. Simultaneously, trace amounts of moisture introduced by the acid catalyst are removed. Through neutralization, the stability of the modified starch is further improved, extending its shelf life. During cooling, stirring and residual heat evaporate any trace amounts of moisture introduced by the neutralization solution, achieving the desired drying effect. The modified hydration heat regulating material prepared can continuously dissolve and adsorb onto the surface of cement particles in an alkaline cement solution. After the C3A reaction in the cement is completed, it can significantly inhibit the hydration rate of C3S in the cement particles for 1-2 days, effectively regulate the hydration process of cement during the accelerated period, avoid concentrated heat release, thereby reducing the internal temperature rise and internal-external temperature difference of concrete, and preventing the generation of early temperature cracks in concrete. The shrinkage reducing agent further reduces the internal surface tension between cement particles through physical means, compensates for concrete shrinkage, and prevents cracking.

[0018] Preferably, the concentration of the polymer solution is 4wt% to 8wt%, and the mass ratio of the polymer solution to polyvinyl alcohol is 100:(0.3 to 0.5).

[0019] Preferably, the acid catalyst includes at least one of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, malic acid, citric acid, tartaric acid, acetic acid, succinic acid, or tannic acid.

[0020] Preferably, the starch includes at least one of pea starch, corn starch, potato starch, and wheat starch.

[0021] Preferably, the calcium oxide-calcium sulfoaluminate dual-expansion-source expanded clinker is prepared by the following method:

[0022] Q1. Weigh limestone, fluorite, bauxite, and iron slag, mix them thoroughly, add water, shake until they form balls, and dry them to obtain raw material;

[0023] Q2. Place the raw material in an electric furnace, heat it to 1200~1400℃, hold it at that temperature for 0.5~1 hour, allow it to cool naturally to room temperature, and then grind it to a specific surface area of ​​200~300 m². 2 / kg, thus obtaining the calcium oxide-calcium sulfoaluminate dual expansion source expanded clinker.

[0024] Preferably, the raw materials for preparing the raw meal, by mass percentage, include: 70%~80% limestone, 15%~20% fluorogypsum, 1%~5% bauxite, and 1%~5% iron slag.

[0025] The low-activity magnesium oxide expanding agent has an active reaction time of 350~400s, a magnesium oxide content of ≥90%, and a fineness of ≤5% on an 80um sieve.

[0026] The specific surface area of ​​the semi-densified silica fume is 300~350 kg / m². 3 The silica content is greater than 92%.

[0027] The shrinkage reducing agent is a compound of polyalkylene glycol and propylene glycol in a mass ratio of 1:(1~2).

[0028] Another object of the present invention is to provide a method for preparing the erosion-resistant, expansion-resistant, and crack-resistant agent for concrete, comprising the following steps: after obtaining modified expansive clinker and modified hydration heat regulating material, the modified expansive clinker, low-activity magnesium oxide expansive agent, semi-densified silica fume, alumina ceramic micro powder, modified hydration heat regulating material, water-reducing agent, shrinkage-reducing agent and perlite are mixed evenly according to mass percentage to obtain the erosion-resistant, expansion-resistant, and crack-resistant agent.

[0029] The erosion-resistant, expansion-resistant, and crack-resistant agent for concrete described in this invention is incorporated into C30-C60 concrete at a dosage of 6wt% to 10wt% of the total adhesive material.

[0030] Compared with the prior art, the advantages of the present invention are:

[0031] (1) This invention reduces the exothermic temperature peak of concrete by modifying the heat of hydration control material, thereby reducing the temperature shrinkage of concrete during the cooling process. It effectively inhibits shrinkage cracking of concrete by regulating the hydration rate and delaying micro-expansion by modifying the expansive clinker. It reduces the auto-shrinkage of concrete by reducing the shrinkage component. It enhances the density of the concrete matrix by using semi-dense silica fume and perlite. It enhances the wear resistance of the concrete matrix by using alumina ceramic micro powder. At the same time, the components of this invention have a mutually promoting effect. The heat of hydration control component can promote the expansion effect of the expansive component and can also synergistically improve the impact and wear resistance of concrete. Under the synergistic effect of the components, the crack resistance and erosion resistance of concrete are significantly improved.

[0032] (2) The present invention uses polymer solution and polyvinyl alcohol to coat clinker, so that the clinker surface has a certain hydrophobicity, reducing the contact area between clinker and water, delaying the reaction time of clinker expansion, and improving the compensating shrinkage effect of concrete during the hardening process.

[0033] (3) The present invention uses a dry process to modify starch acidification, which can avoid starch agglomeration and clumping during the mixing process, effectively reduce the internal temperature rise and internal and external temperature difference of concrete, prevent the generation of early temperature cracks in concrete, and at the same time improve the impact and abrasion resistance of concrete. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the following examples and comparative examples, the low-activity magnesium oxide expanding agent used in this invention has an activity reaction time of 350~400s, a magnesium oxide content ≥90%, and a fineness of ≤5% residue on an 80µm sieve; the specific surface area of ​​the semi-densified silica fume is 300~350kg / m². 3 The silica content is greater than 92%; the polycarboxylate superplasticizer is in powder form with a water reduction rate of ≥25%; the polymer solution is an aqueous polymer solution; the starch can be any combination of pea starch, corn starch, potato starch, and wheat starch; the acid catalyst can be at least one of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, malic acid, citric acid, tartaric acid, acetic acid, succinic acid, or tannic acid.

[0036] Example 1

[0037] This embodiment provides an anti-erosion and anti-cracking agent for concrete, which is made from the following raw materials in the following mass percentages: 40% modified expansive clinker; 25% low-activity magnesium oxide expansive agent; 13% semi-densified silica fume; 13% alumina ceramic micro powder; 2% modified hydration heat regulating material; 3.5% polycarboxylate superplasticizer; 0.5% shrinkage reducer; and 3% perlite. The above raw materials in the above mass percentages are stirred in a horizontal twin-shaft mixer for more than 10 minutes. After being mixed evenly, the anti-erosion and anti-cracking agent for concrete is obtained.

[0038] The modified expanded clinker mentioned above is prepared according to the following steps:

[0039] Step 1: Weigh out 76% limestone, 18% fluorogypsum, 4% bauxite, and 2% iron slag by mass percentage, mix them thoroughly, add water equal to 16% of the total powder, shake until the mixture forms balls, and then place it in a 105℃ oven for 2 hours to obtain raw material.

[0040] Step 2: Place the raw materials in an electric furnace, heat to 1300℃ for 2 hours, hold for 1 hour, and allow to cool naturally to room temperature. Grind the raw materials using a disc mill until the specific surface area is 250 m². 2 / kg, to obtain calcium oxide-calcium sulfoaluminate dual expansion source expanded clinker;

[0041] Step 3: Spray 3% of the surface modifier by mass of the clinker into the clinker under stirring. After stirring thoroughly and evenly, let stand for 2 days. The surface modifier is obtained by stirring a polymer solution with a mass ratio of 100:0.4 and polyvinyl alcohol at 45°C for 1 hour. The polymer solution is a 5wt% styrene-acrylate emulsion.

[0042] Step 4: The modified expanded clinker is sieved to obtain a particle size distribution of 30~200um, which is the modified expanded clinker. The free calcium oxide content in the modified expanded clinker is 40wt% and the sulfur trioxide content is 9wt%.

[0043] The above-mentioned modified hydration heat control material is prepared according to the following steps:

[0044] Step 1: While stirring the dry starch at a speed of 150 r / min, add 5% of the starch mass of acid catalyst by spraying, and ensure that the acid catalyst is evenly distributed on the surface of the starch particles. The acid catalyst is 2wt% hydrochloric acid.

[0045] Step 2: Stir the starch obtained in Step 1 at 50°C for 1 hour, then raise the temperature to 130°C and continue stirring for 2 hours. Finally, add a 5wt% sodium carbonate or sodium hydroxide solution by spraying to neutralize until the starch pH value is 6.

[0046] Step 3: Continue stirring the starch obtained in step 2 at 150 r / min for 3 hours. After the temperature drops to room temperature, sieve it and take particles with a size distribution of 30~100 μm to obtain the modified hydration heat control material.

[0047] The low-activity magnesium oxide expanding agent has an activation reaction time of 400s, a magnesium oxide content of 91.7%, and a fineness of 3% residue on an 80µm sieve; the semi-densified silica fume has a specific surface area of ​​350kg / m². 3 The silica content is 96%; the alumina ceramic powder has a fineness of 200 mesh; the polycarboxylate superplasticizer is in powder form with a water reduction rate of 27%; the shrinkage reducer is a mixture of polyalkylene glycol and propylene glycol in a mass ratio of 1:1; and the perlite has a fineness of 100 mesh.

[0048] Example 2

[0049] This embodiment is basically the same as Embodiment 1, except that: the mass percentage of modified expanded clinker is 30%; the mass percentage of low-activity magnesium oxide expander is 20%; the mass percentage of semi-densified silica fume is 25%; and the mass percentage of alumina ceramic micro powder is 16%.

[0050] Example 3

[0051] This embodiment is basically the same as Embodiment 1, except that: the mass percentage of the low-activity magnesium oxide expanding agent is 24%; and the mass percentage of the modified hydration heat regulating material is 3%.

[0052] Example 4

[0053] This embodiment is basically the same as Embodiment 1, except that: the mass percentage of semi-densified silica fume is 17%; the mass percentage of polycarboxylate superplasticizer is 1.5%; and the mass percentage of perlite is 1%.

[0054] Example 5

[0055] This embodiment is basically the same as Example 1, except that the shrinkage reducing agent is a mixture of polyalkylene glycol and propylene glycol in a mass ratio of 1:2.

[0056] Example 6

[0057] This embodiment is basically the same as Embodiment 1, except that: in the preparation method of expanded clinker, the mass of the surface modifier is 2% of the mass of the clinker, and the surface modifier is made by mixing 4wt% styrene-butadiene emulsion and polyvinyl alcohol at a mass ratio of 100:0.4.

[0058] Example 7

[0059] This embodiment is basically the same as embodiment 1, except that:

[0060] The modified hydration heat control material is prepared according to the following steps:

[0061] Step 1: While stirring the dry starch at a speed of 100 r / min, add 3% of the starch mass of acid catalyst by spraying, and ensure that the acid catalyst is evenly distributed on the surface of the starch particles. The acid catalyst is 2wt% hydrochloric acid.

[0062] Step 2: Stir the starch obtained in Step 1 at 40°C for 1 hour, then raise the temperature to 120°C and continue stirring for 2 hours. Finally, add a 5wt% sodium carbonate or sodium hydroxide solution by spraying to neutralize until the starch pH value is 6.

[0063] Step 3: Continue stirring the starch obtained in step 2 for 3 hours. After the temperature drops to room temperature, sieve it and take particles with a size distribution of 30~100um to obtain the modified hydration heat control material.

[0064] Comparative Example 1

[0065] This comparative example is basically the same as Example 1, except that in the preparation method of modified expanded clinker, the surface modifier is a 5 wt% polyvinyl alcohol dimethyl sulfoxide solution, and the dosage is 3% of the clinker mass.

[0066] Comparative Example 2

[0067] This comparative example is basically the same as Example 1, except that in the preparation method of the modified expanded clinker, the surface modifier is a styrene-acrylate emulsion with a concentration of 5wt%, that is, compared with Example 1, this comparative example omits polyvinyl alcohol.

[0068] Comparative Example 3

[0069] The difference between this comparative example and Example 1 is that an equal amount of high-activity magnesium oxide expanding agent with an active reaction time of 80s is used to replace the low-activity magnesium oxide expanding agent.

[0070] Comparative Example 4

[0071] This comparative example is basically the same as Example 1, except that:

[0072] The modified hydration heat control material is prepared according to the following steps:

[0073] Step 1: Disperse 1 part by weight of starch in 50 parts by weight of 0.5 mol / L hydrochloric acid solution, stir at 75℃ for 2 hours at a stirring speed of 100 r / min, cool naturally to room temperature and let stand for 3 hours to allow the starch particles in the solution to fully precipitate.

[0074] Step 2: Filter off the supernatant, take the lower precipitate solid, wash it, spread it evenly in an oven at 45℃, and dry it to constant weight to obtain solid particles.

[0075] Step 3: Grind the above solid particles to a density of 100-200 μm. 2 / kg, thus obtaining the modified hydration heat regulation material.

[0076] Comparative Example 5

[0077] The difference between this comparative example and Example 1 is that an equal amount of inert limestone powder is used to replace the modified hydration heat control material.

[0078] Comparative Example 6

[0079] The difference between this comparative example and Example 1 is that an equal amount of inert material limestone powder is used instead of semi-densified silica fume.

[0080] Comparative Example 7

[0081] The difference between this comparative example and Example 1 is that an equal amount of inert material limestone powder is used instead of alumina ceramic powder.

[0082] Comparative Example 8

[0083] The difference between this comparative example and Example 1 is that the shrinkage reducing agent is polyalkylene glycol.

[0084] Comparative Example 9

[0085] The difference between this comparative example and Example 1 is that an equal amount of inert material, limestone powder, is used instead of perlite.

[0086] Test case

[0087] 1) Referring to industry standard JC / T2608-2021 "Inhibitors of Concrete Hydration Temperature Rise", the hydration heat reduction rate of mortar was tested. The concrete erosion expansion and crack-resistant agent was added at 10% (internal admixture) of the total mass fraction of cementitious materials. The mortar mix ratio was as follows: 450 parts of reference cement, 200 parts of water, 50 parts of concrete erosion expansion and crack-resistant agent, and 1500 parts of medium sand. The test temperature was 20℃. The test results of the mortar hydration heat reduction rate for each example and comparative example are shown in Table 1.

[0088] Table 1. Test results of mortar hydration heat reduction rate

[0089]

[0090] As shown in Table 1, the hydration heat reduction rate of mortar after incorporating the anti-erosion expansion and crack-resistant agent for concrete of the present invention can exceed 50%, which is far higher than the technical indicator of ≥30% hydration heat reduction rate of mortar at a test temperature of 20±1℃ specified in standard JC / T2608-2021 "Inhibitors of Concrete Hydration Temperature Rise"? Comparison of Example 1 and Comparative Examples 1-2 shows that, compared with using styrene-acrylate emulsion or polyvinyl alcohol alone to coat and modify the expanded clinker, the present invention's use of styrene-acrylate emulsion and polyvinyl alcohol to coat the expanded clinker can significantly improve the 24-hour hydration heat reduction rate, while the 7-day hydration heat reduction rate remains basically the same, with no negative impact on the total heat release of hydration in the later stages. Comparison of Example 1 and Comparative Example 3 shows that, compared with high-activity magnesium oxide expansion agent, the present invention's use of low-activity magnesium oxide expansion agent can significantly improve the 24-hour hydration heat reduction rate.

[0091] By comparing Example 1 and Comparative Example 4, it can be seen that, compared with conventional acid soaking modification, the 24-hour hydration heat reduction rate of starch modified by dry process is comparable to or even better than that of starch modified by traditional wet process. The 7-day hydration heat reduction rate is basically the same. However, the dry process can significantly reduce the cost of starch acidification modification, with low energy consumption and no wastewater discharge.

[0092] Comparing Example 1 and Comparative Example 5, it can be seen that Comparative Example 5, without the addition of hydration heat regulating components, has virtually no temperature suppression effect. Comparing Example 1 and Comparative Examples 7-9, it can be seen that alumina ceramic powder, shrinkage reducer, and perlite have no effect on the heat of hydration.

[0093] 2) Referring to the current national standard GB23439-2017 "Concrete Expansion Agent", the mortar's limited expansion performance was tested. The concrete erosion-resistant expansion and crack-resistant agent was added at 10% (internal admixture) of the total mass fraction of the cementitious materials. The mortar mix ratio was as follows: 607.5 parts of reference cement, 270 parts of water, 67.5 parts of concrete erosion-resistant expansion and crack-resistant agent, and 1350 parts of standard sand. The test temperature was 20℃. The test results of the limited expansion performance of the mortar in each example and comparative example are shown in Table 2.

[0094] Table 2 Test results of mortar's restricted expansion performance

[0095]

[0096] Table 2 shows that, compared with the baseline group, the mortar specimens incorporating the anti-erosion expansion and crack-resistant agent for concrete of the present invention exhibited a significantly increased restricted expansion rate under water curing conditions at 20℃, and continued to expand even after 60 days and 120 days of curing. Comparison of Example 1 and Comparative Examples 1-2 shows that, compared with using styrene-acrylate emulsion or polyvinyl alcohol alone to encapsulate and modify the expanding clinker, the present invention, using styrene-acrylate emulsion and polyvinyl alcohol, increases the expansion energy after 3 days of curing, delays the reaction time of the expanding clinker, reduces ineffective expansion of the expanding clinker during the plastic stage of concrete, and improves the effective expansion energy of the expanding clinker. Comparison of Example 1 and Comparative Example 3 shows that, compared with a high-activity magnesium oxide expanding agent, the low-activity magnesium oxide expanding agent used in the present invention has the characteristic of delayed micro-expansion, with the expansion rate matching the rate of concrete shrinkage, continuously generating expansion energy, and improving the later-stage compensation shrinkage effect.

[0097] By comparing Example 1 and Comparative Example 4, it can be seen that, compared with conventional acid soaking modification, the development law of the expansion rate of starch modified by dry process and starch modified by traditional wet process is basically the same. However, the dry process can significantly reduce the cost of starch acidification modification, with low energy consumption and no wastewater discharge.

[0098] By comparing Example 1 and Comparative Example 5, it can be seen that Comparative Example 5, without the addition of the heat of hydration regulating component, has a reduced expansion rate, indicating that the heat of hydration regulating component can improve the expansion efficiency of the expansion agent to a certain extent.

[0099] 3) The erosion-resistant expansion and crack-resistant agent of this invention was incorporated into C40 concrete. The fluidity of the mixture was tested according to the national standard GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". The compressive strength and splitting crack strength of the concrete were tested according to the national standard GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The erosion-resistant strength of the concrete was tested according to the underwater steel ball method in the industry standard DL / T5150-2017 "Test Procedure for Hydraulic Concrete". The concrete mix was as follows: 300 parts of P•O 42.5 ordinary Portland cement, 40 parts of Grade II fly ash, 695 parts of river sand, 617 parts of 5~20mm crushed stone, 617 parts of 20~40mm crushed stone, 8 parts of polycarboxylate superplasticizer, 146 parts of mixing water, and 30 parts of erosion-resistant expansion and crack-resistant agent for concrete. The test results are shown in Table 3.

[0100] Table 3. Test results of concrete performance

[0101]

[0102] As shown in Table 3, compared with the baseline group, the addition of the erosion-resistant and crack-resistant agent for concrete of the present invention has little effect on the slump of the concrete, but can significantly improve the compressive strength and splitting tensile strength of the concrete. Compared with the baseline group, the 28-day compressive strength ratio and splitting tensile strength ratio are both greater than 100%, indicating that the erosion-resistant and crack-resistant agent of the present invention has a promoting effect on the mechanical properties of concrete. By comparing the 28-day impact abrasion strength, it can be seen that compared with the blank group, the impact abrasion strength of Examples 1 to 7 can be increased by more than 30%, indicating that the erosion-resistant and crack-resistant agent of the present invention can significantly improve the impact abrasion strength of concrete.

[0103] Comparing Example 1 and Comparative Examples 1-2, it can be seen that compared with using styrene-acrylate emulsion or polyvinyl alcohol alone to coat and modify the expanded clinker, the present invention using styrene-acrylate emulsion and polyvinyl alcohol can significantly improve the impact and abrasion resistance of concrete. Comparing Example 1 and Comparative Example 3, it can be seen that compared with a high-activity magnesium oxide expanding agent, the present invention using a low-activity magnesium oxide expanding agent can significantly improve the impact and abrasion resistance of concrete.

[0104] By comparing Example 1 and Comparative Example 4, it can be seen that, compared with conventional acid soaking modification, the dry process for modifying starch and the traditional wet process for modifying starch have a similar impact on the development law of concrete mechanical properties. However, the dry process can significantly reduce the cost of starch acidification modification, with low energy consumption and no wastewater discharge.

[0105] By comparing Example 1 and Comparative Example 5, it can be seen that the concrete in Comparative Example 5 without the addition of the heat of hydration modifier is significantly less resistant to impact and abrasion, indicating that the modified heat of hydration modifier can synergistically improve the impact and abrasion resistance of concrete.

[0106] By comparing Example 1 and Comparative Examples 6-7, it can be seen that semi-densified silica fume can effectively improve the internal pore structure of hardened concrete and increase the concrete's impact and abrasion resistance through the dual effects of microcrystalline nuclei and volcanic ash activity. Alumina ceramic micro powder has excellent wear resistance and can significantly improve the concrete's impact and abrasion resistance when added to concrete.

[0107] By comparing Example 1 and Comparative Examples 8-9, it can be seen that the shrinkage reducing agent improves both the strength and impact resistance of concrete, while perlite has a significant impact on the workability of concrete.

[0108] Based on the above test results, it can be seen that the concrete anti-erosion expansion and crack-resistant agent of the present invention has little impact on the workability of concrete, can significantly reduce the heat of cement hydration, reduce the risk of cracking caused by temperature shrinkage of concrete, can play a role in compensating for shrinkage throughout the entire cycle, especially the early shrinkage compensation effect is obvious, and it has an effect on improving long-term mechanical properties and significantly improving the impact and abrasion resistance of concrete.

[0109] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An anti-erosion and anti-cracking agent for concrete, characterized in that, The raw materials include the following percentages by weight: modified expanded clinker 30%~50%, low-activity magnesium oxide expanding agent 20%~40%, semi-densified silica fume 10%~30%, alumina ceramic micro powder 10%~20%, modified hydration heat control material 1%~5%, water reducing agent 1%~5%, shrinkage reducing agent 0.2%~1%, and perlite 1%~5%; The modified expanded clinker is prepared by the following method: 2% to 4% of the clinker mass of surface modifier is sprayed into the calcium oxide-calcium sulfoaluminate dual expansion source expanded clinker under stirring. After stirring evenly, it is allowed to stand for 1 to 2 days to obtain the modified expanded clinker. The surface modifier includes a polymer solution and polyvinyl alcohol. The polymer solution includes at least one of styrene-acrylate emulsion or styrene-butadiene emulsion. The modified hydration heat regulating material is prepared by the following method: P1. Under stirring, add 3% to 8% of the starch mass of acid catalyst to the dry starch by spraying, stir at 40 to 60°C for 0.5 to 2 hours, then raise the temperature to 120 to 150°C and continue stirring for 1 to 3 hours. Finally, add alkaline solution by spraying to neutralize until the starch pH value is 5 to 6. P2. Continue stirring the neutralized starch until the temperature drops to room temperature, then sieve to obtain starch with a particle size of 30~100μm, thus obtaining the modified hydration heat control material.

2. The erosion-resistant, expansion-resistant, and crack-resistant agent for concrete according to claim 1, characterized in that, The concentration of the polymer solution is 4wt%~8wt%, and the mass ratio of the polymer solution to polyvinyl alcohol is 100:(0.3~0.5).

3. The erosion-resistant, expansion-resistant, and crack-resistant agent for concrete according to claim 1, characterized in that, The acid catalyst includes at least one of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, malic acid, citric acid, tartaric acid, acetic acid, succinic acid, or tannic acid.

4. The erosion-resistant, expansion-resistant, and crack-resistant agent for concrete according to claim 1, characterized in that, The starch includes at least one of pea starch, corn starch, potato starch, and wheat starch.

5. The erosion-resistant, expansion-resistant, and crack-resistant agent for concrete according to claim 1, characterized in that, The calcium oxide-calcium sulfoaluminate dual-expansion-source expanded clinker is prepared by the following method: Q1. Weigh limestone, fluorite, bauxite, and iron slag, mix them thoroughly, add water, shake until they form balls, and dry them to obtain raw material; Q2. Place the raw material in an electric furnace, heat it to 1200~1400℃, hold it at that temperature for 0.5~1 hour, allow it to cool naturally to room temperature, and then grind it to a specific surface area of ​​200~300 m². 2 / kg, thus obtaining the calcium oxide-calcium sulfoaluminate dual expansion source expanded clinker.

6. The erosion-resistant, expansion-resistant, and crack-resistant agent for concrete according to claim 5, characterized in that, The raw materials for preparing the raw meal, by mass percentage, include: limestone 70%~80%, fluorogypsum 15%~20%, bauxite 1%~5%, and iron slag 1%~5%.

7. The erosion-resistant, expansion-resistant, and crack-resistant agent for concrete according to claim 1, characterized in that, The low-activity magnesium oxide expanding agent has an active reaction time of 350~400s, a magnesium oxide content of ≥90%, and a fineness of ≤5% on an 80um sieve.

8. The erosion-resistant, expansion-resistant, and crack-resistant agent for concrete according to claim 1, characterized in that, The specific surface area of ​​the semi-densified silica fume is 300~350 kg / m². 3 The silica content is greater than 92%.

9. The erosion-resistant, expansion-resistant, and crack-resistant agent for concrete according to claim 1, characterized in that, The shrinkage reducing agent is a compound of polyalkylene glycol and propylene glycol in a mass ratio of 1:(1~2).

10. The method for preparing the concrete erosion-resistant, expansion-resistant, and crack-resistant agent according to any one of claims 1 to 9, characterized in that, Includes the following steps: After obtaining the modified expanded clinker and the modified hydration heat control material, the modified expanded clinker, low-activity magnesium oxide expansion agent, semi-densified silica fume, alumina ceramic micro powder, modified hydration heat control material, water-reducing agent, shrinkage-reducing agent and perlite are mixed evenly according to the mass percentage to obtain the erosion-resistant expansion and crack-resistant agent.

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