Ferroaluminate cement fine stone fiber concrete repair material and paving process thereof

Abstract

The invention belongs to the technical field of civil engineering materials and road repair, and discloses an aluminoferrite cement fine stone fiber concrete repair material and a paving process thereof. According to the concrete repairing material, aluminoferrite cement is used as a cementing material, continuous grading fine stone is used as aggregate, a material with the maximum stacking dry density is prepared, and a fiber material and a polymer are doped; based on the total mass of the repairing material, the doping amount of the fiber material is 0.5-2.0 kg / m < 3 >; the weight percentage of the solid content in the polymer is 3-10%; the water-binder ratio is less than or equal to 0.40; the paving process comprises the steps of base surface treatment, interface strengthening, repairing layer paving and maintenance. According to the invention, aggregate grading optimization, fiber reinforcement and polymer modification technologies are combined, so that a high-weather-resistance early-strength repair material and a low-interference construction process are realized; the maximum particle size of the material is less than or equal to 8mm, the elastic modulus is matched with the existing pavement, the compressive strength is greater than or equal to C50, the material is suitable for thin layer repair (greater than or equal to 5cm) of dynamic load scenes such as airfield runways, highways and underground passages, and unification of durability and construction efficiency is realized.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering materials and road repair technology, specifically, it relates to concrete repair materials and their paving process. Background Technology

[0002] In the frigid northern regions, the annual freeze-thaw cycle can reach 50-150 times, and the amount of de-icing salt (mainly NaCl and CaCl2) used can be as high as 200-400 g / m³. 2 Chloride ions penetrate into the concrete, causing triple damage: (1) reacting with the hydration products of silicate cement to generate expansive Friedel salt (3CaO·Al2O3·CaCl2·10H2O), increasing in volume by 120%, leading to cracking of the protective layer; (2) the expansion pressure of steel corrosion exceeds 30MPa, accelerating crack propagation; (3) water expands by 9% when it freezes at low temperatures, and the salt solution can still form sub-freezing at -20℃, generating a crystallization pressure of 17MPa. The synergistic effect of these three factors causes the concrete surface to peel off at a rate of 1-3mm / year. Traditional silicate cement repair layers have high porosity (>15%), high Ca(OH)2 content (about 20%), and a chloride ion diffusion coefficient of 8.0×10. -12 m 2 / s, the recurrence rate within 2 years after repair exceeds 75%, and the annual repair cost accounts for 5%-8% of the total infrastructure investment.

[0003] The current mainstream repair scheme has four technical bottlenecks: (1) Insufficient weather resistance of materials: Sulfoaluminate cement has early strength but unstable phase transformation in the later stage. After 50 freeze-thaw cycles, the compressive strength is reduced by 40%; the elastic modulus of epoxy materials is only 3-5 GPa, which is seriously mismatched with the concrete matrix (30-35 GPa). When the interface shear stress exceeds 1.5 MPa under dynamic load, the bond is broken; (2) Poor structural adaptability: When the aggregate particle size of ordinary fiber concrete is >15mm, the stress concentration at the contact point of coarse aggregate in thin layer paving is less than 100,000 times; (3) Interface strengthening defects: Mechanical chiseling method destroys the integrity of the base layer, and the anchor bolt implantation produces a 2-3cm stress relaxation zone; silane interface agents fail due to hydrolysis in salt environment, and the bond strength decreases by 60% within half a year; (4) Low construction controllability: 3%-5% chloride salt is added to early strength silicate cement to accelerate setting and introduce Cl - The content exceeds the weight of the adhesive material by 0.1%; when polymer-modified mortar is applied at low temperature (<5℃), the film formation is discontinuous, and the bonding strength is only 0.8-1.2MPa. Summary of the Invention

[0004] This invention addresses the technical problems of concrete structural layer spalling and cracking caused by de-icing agent corrosion and freeze-thaw cycles in northern winters. It provides a ferroaluminate cement fine stone fiber concrete repair material and its paving process. Through a ferroaluminate cement-based composite material system, combined with aggregate gradation optimization, fiber reinforcement, and polymer modification technology, a highly weather-resistant, early-strength repair material and a low-interference construction process are achieved. The material has a maximum particle size ≤8mm, an elastic modulus that matches the existing pavement, and a compressive strength ≥C50. It is suitable for thin-layer repair (≥5cm) in dynamic load scenarios such as airport runways, highways, and underground passages, achieving a balance between durability and construction efficiency.

[0005] According to one aspect of the present invention, a ferroaluminate cement fine stone fiber concrete repair material is provided.

[0006] include:

[0007] Ferroaluminate cement;

[0008] The material with the highest bulk dry density configured using continuously graded fine stone as aggregate;

[0009] Fiber materials;

[0010] polymer;

[0011] water;

[0012] Water-reducing agent;

[0013] Of this, the amount of fiber material incorporated, based on the total mass of the repair materials, is 0.5-2.0 kg / m³. 3 ;

[0014] Of which, based on the total mass of the repair materials, the weight percentage of solids in the polymer is 3-10%;

[0015] The water-to-binder ratio is ≤0.40.

[0016] Preferably, the diameter of the aggregate is no greater than 8 mm; the gradation of the aggregate satisfies: ≥85% passing rate on a 4.75 mm sieve and 40-60% passing rate on a 0.6 mm sieve.

[0017] Preferably, the fiber material is at least one of basalt fiber and end-hooked steel fiber, or a mixture of at least one of basalt fiber and end-hooked steel fiber with polypropylene fiber.

[0018] Preferably, the fiber material has a length of 12-18 mm and a diameter of 15-25 μm.

[0019] Preferably, the polymer is a redispersible acrylate powder or styrene-butadiene latex.

[0020] Furthermore, the 28-day compressive strength is ≥50MPa, and the elastic modulus is 28-35GPa.

[0021] According to another aspect of the present invention, a method for preparing the above-mentioned aluminoferrite cement fine stone fiber concrete repair material is provided, wherein the material with the highest bulk dry density and the fiber material are first dry mixed for 1-2 minutes, then aluminoferrite cement and polymer are added and mixed for 1-2 minutes, and finally water and water-reducing agent are added and stirred for 2-3 minutes until the fluidity is ≥180mm.

[0022] According to another aspect of the present invention, a composite structure is provided, comprising, from bottom to top, an existing concrete layer, an interface agent layer, and a repair layer composed of the aforementioned aluminoferrite cement fine stone fiber concrete repair material, wherein the elastic modulus deviation of the concrete layer, the interface agent layer, and the repair layer is ≤10%.

[0023] According to another aspect of the present invention, a process for paving the above-mentioned composite structure is provided, comprising the following steps:

[0024] S1. Base surface treatment: Mechanically mill the damaged concrete down to a solid base layer, and cut vertical seams along the edge of the repair area; use high-pressure water jets to wash the base surface to remove dust, oil, and loose particles; allow it to air dry until it is surface dry.

[0025] S2, Interface Strengthening: Apply an interface agent to form a continuous film layer, and proceed to the next process immediately after surface drying;

[0026] S3. Repair layer paving: Prepare the iron aluminate cement fine stone fiber concrete repair material and form a repair layer by spraying or manual paving;

[0027] S4. Curing: After the repair layer has initially set, cover it with a film and spray water for curing for ≥7 days. During winter construction, erect a shed for insulation.

[0028] Preferably, in S1, the vertical seam depth is ≥20mm; the pressure of the high-pressure water jet is ≥20MPa; the moisture content in the surface-dried state is ≤10%; and natural air drying is assisted by a blower for drying.

[0029] Preferably, the interface agent is a two-component epoxy interface agent or polymer cement slurry; the application rate of the interface agent is 0.4-0.6 kg / m². 2 The coating thickness is 1-2mm.

[0030] Preferably, the spraying paving is carried out in layers using a wet spraying machine, with the spray gun vertically 0.8-1.2m from the substrate, the air pressure 0.4-0.6MPa, and the layer thickness ≤5cm; the manual paving is carried out by pouring into the mold, with a scraper to assist in leveling, and the use of vibratory rods for tamping is prohibited.

[0031] Preferably, after initial setting, a water-retaining membrane is covered, and water is sprayed for curing at a temperature of 5-30℃ for ≥7 days; during winter construction, an insulated shed is erected, and a hot air blower is used to maintain the ambient temperature at ≥10℃; light traffic is allowed when the strength is ≥30MPa after 24 hours, and heavy traffic is allowed when the strength is ≥45MPa after 7 days.

[0032] The beneficial effects of this invention are:

[0033] This invention generates an iron-rich gel through the hydration of aluminoferrite cement (mainly minerals C4AF and C2S), which has high density and low porosity. - With a permeability coefficient only 1 / 5 that of silicate cement and no Ca(OH)2 leaching, it fundamentally resists de-icing salt corrosion and freeze-thaw damage. Furthermore, by incorporating fiber materials, it achieves a three-dimensional random distribution to block crack propagation and improve toughness. At the same time, the optimized continuous gradation of aggregates in the material with the highest bulk dry density achieves self-compactment, reducing vibration disturbance to the base layer. In addition, by incorporating polymers, a network is formed on the surface of the cement hydration film, enhancing the chemical bonding and mechanical interlocking between the old and new concrete, with a bond strength ≥2.5MPa. Furthermore, by controlling the water-cement ratio, the elastic modulus of the repair layer is matched to the existing pavement (deviation ±10%), avoiding stress concentration that could lead to delamination. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating the paving process of the aluminate cement fine stone fiber concrete repair material provided by the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0036] Example 1:

[0037] Ferroaluminate cement as a cementing material: 400 kg / m³ 3 ;

[0038] The maximum bulk dry density material (including aggregate and powder) configured with continuously graded fine stone as aggregate: wherein the maximum particle size of the aggregate is ≤8mm, the gradation is optimized (continuous gradation, fineness modulus 2.8), and the dosage is 1000 kg / m³. 3 ;

[0039] Basalt fiber (0.5 kg / m³ based on total mass of repair material) 3 ); fiber length 12mm, fiber diameter 15μm;

[0040] Solid content in polymer: 3% by weight (based on the total mass of the repair material, i.e., 12 kg / m³). 3 ), the type is redispersible latex powder (EVA);

[0041] Water-cement ratio (mass ratio of water to cementitious material): 0.40;

[0042] Additives: Use a water-reducing agent (polycarboxylate-based, at a dosage of 0.5% of the total mass of the repair material) to ensure workability.

[0043] Preparation of concrete repair materials:

[0044] Forced mixer dry mix basalt fiber + maximum bulk dry density material for 1 minute, add aluminoferrate cement + polymer and mix for 1 minute, finally add water + water-reducing agent and mix for 2 minutes until the fluidity is ≥180mm.

[0045] like Figure 1 As shown, the construction method for composite structures is as follows:

[0046] Base surface treatment: Mechanically mill the damaged concrete until the solid base layer is exposed; cut vertical seams (depth ≥ 20 mm) along the edge of the repair area; rinse the base surface with high-pressure water jet (pressure ≥ 20 MPa) to remove floating dust, oil stains and loose particles; air dry naturally until surface dry (moisture content ≤ 10%), and use a blower to assist drying if necessary.

[0047] Interface strengthening: Apply a two-component epoxy interface agent or polymer cement slurry, using 300g; apply to a thickness of 1-2mm to form a continuous film layer. Once surface dry (not sticky to the touch), proceed to the next step immediately.

[0048] Concrete repair material preparation and spreading: Apply in layers with a wet spraying machine (single layer ≤ 5cm), with the spray gun 0.8m vertically from the base surface and the air pressure 0.4MPa.

[0049] (4) Curing and protection: After initial setting, cover with a water-retaining membrane (PE material) and spray water for curing for ≥7 days (temperature 5-30℃); during winter construction, set up an insulation shed and use a hot air blower to maintain the ambient temperature ≥10℃; light traffic can be opened when the strength is ≥30MPa after 24 hours, and heavy load can be opened when the strength is ≥45MPa after 7 days.

[0050] Performance test results:

[0051] 24-hour compressive strength: 22.5 MPa

[0052] 28-day compressive strength: 55.3 MPa (meets ≥C50 requirements)

[0053] Elastic modulus: 32.5 GPa (matching the elastic modulus of existing pavement concrete, which is 30-35 GPa)

[0054] Resistance to de-icing salt corrosion: After 300 freeze-thaw cycles (-20°C to 20°C, using 4% NaCl solution to simulate de-icing salt), the mass loss rate is 0.8% (far lower than the standard requirement of 5%), and there is no peeling on the surface.

[0055] Maintenance cost assessment: Compared with traditional repair materials, maintenance costs are reduced by approximately 50% due to increased durability and reduced need for repeated repairs.

[0056] Example 2:

[0057] Ferroaluminate cement as a cementing material: 400 kg / m³ 3 ;

[0058] The maximum bulk dry density material (including aggregate and powder) configured using continuously graded fine stone as aggregate: wherein the maximum particle size of the aggregate is ≤8mm, the gradation is optimized (continuous gradation, fineness modulus 2.8), and the dosage is 1600 kg / m³. 3 ;

[0059] Basalt fiber: (1.0 kg / m³ based on the total mass of the restoration material) 3 ); fiber length 12mm, fiber diameter 15μm;

[0060] Polymer powder: Medium solids content: 5% by weight (based on the total mass of the repair material, i.e., 20 kg / m³). 3 ), the type is redispersible latex powder (EVA);

[0061] Water-cement ratio (mass ratio of water to cementitious material): 0.38;

[0062] Additives: Use a water-reducing agent (polycarboxylate-based, at a dosage of 0.5% of the total mass of the repair material) to ensure workability.

[0063] Preparation of concrete repair materials:

[0064] Forced mixer dry mix basalt fiber + maximum bulk dry density material for 1 minute, add aluminoferrate cement + polymer and mix for 1 minute, finally add water + water-reducing agent and mix for 2 minutes until the fluidity is ≥180mm.

[0065] Construction method:

[0066] Base surface treatment: Mechanically mill the damaged concrete until the solid base layer is exposed; cut vertical seams (depth ≥ 20 mm) along the edge of the repair area; rinse the base surface with high-pressure water jet (pressure ≥ 20 MPa) to remove floating dust, oil stains and loose particles; air dry naturally until surface dry (moisture content ≤ 10%), and use a blower to assist drying if necessary.

[0067] Interface strengthening: Apply a two-component epoxy interface agent or polymer cement slurry, using 300g; apply to a thickness of 1-2mm to form a continuous film layer. Once surface dry (not sticky to the touch), proceed to the next step immediately.

[0068] Concrete repair material preparation and spreading: Apply in layers with a wet spraying machine (single layer ≤ 5cm), with the spray gun 0.8m vertically from the base surface and the air pressure 0.4MPa.

[0069] (4) Curing and protection: After initial setting, cover with a water-retaining membrane (PE material) and spray water for curing for ≥7 days (temperature 5-30℃); during winter construction, set up an insulation shed and use a hot air blower to maintain the ambient temperature ≥10℃; light traffic can be opened when the strength is ≥30MPa after 24 hours, and heavy load can be opened when the strength is ≥45MPa after 7 days.

[0070] Performance test results:

[0071] 24-hour compressive strength: 25.1 MPa

[0072] 28-day compressive strength: 58.7 MPa (meets ≥C50 requirements)

[0073] Elastic modulus: 33.2 GPa (matching the elastic modulus of existing pavement concrete, which is 30-35 GPa)

[0074] Resistance to de-icing salt corrosion: After 300 freeze-thaw cycles, the mass loss rate is 0.5%, and there is no surface peeling.

[0075] Maintenance cost assessment: Maintenance costs are reduced by approximately 55% due to high early strength and excellent freeze-thaw resistance.

[0076] Table 1 Performance Comparison Analysis of Examples and Comparative Examples

[0077] Performance indicators Example 1 (Low Dosage) Example 2 (Medium Dosage) Comparative example (ordinary concrete) Test standards and conditions 24-hour compressive strength (MPa) 22.5 25.1 15.2 Standard maintenance, 20±2°C 28-day compressive strength (MPa) 55.3 58.7 48.5 GB / T 50081-2019 Elastic modulus (GPa) 32.5 33.2 28.5 GB / T 50081-2019 Mass loss rate (%) after 300 freeze-thaw cycles 0.8 0.5 5.2 (No longer acceptable) GB / T 50082-2024, Rapid freezing method, 4% NaCl solution Surface appearance after 300 freeze-thaw cycles Intact, no peeling Intact, no peeling Severe spalling and exposure of coarse aggregate visual observation Estimated maintenance cost reduction ~50% ~55% Baseline (no reduction) Based on durability and maintenance cycle estimation

[0078] By comparing the data in Table 1, the following conclusions can be clearly drawn:

[0079] (i) The core advantage of this invention is that it can achieve rapid repair in the early stages of strength.

[0080] The 24-hour strengths of Examples 1 and 2 reached 22.5 MPa and 25.1 MPa respectively, far exceeding the 15.2 MPa of ordinary concrete. This allows the repaired pavement to be open to light traffic or withstand subsequent construction loads within 24 hours, greatly shortening traffic interruption time, and is especially suitable for scenarios with extremely high requirements for traffic efficiency, such as airport runways and highways. The insufficient early strength of ordinary concrete is one of the fundamental reasons for the long repair cycle and traffic disruption.

[0081] (ii) In terms of mechanical compatibility, the present invention can effectively solve the problem of repeated damage.

[0082] The elastic moduli of Examples 1 and 2 (32.5 GPa and 33.2 GPa, respectively) are highly compatible with the typical modulus of existing pavements (30-35 GPa), while the modulus of ordinary concrete (28.5 GPa) is significantly lower. Under dynamic loads, the deformation of the repair layer and the old pavement is coordinated, avoiding stress concentration caused by stiffness differences, thus preventing repeated damage problems such as edge cracking and delamination of the repair layer from the root. Ordinary concrete, due to its mismatched modulus, is highly susceptible to fatigue failure at joints and interfaces.

[0083] (iii) In terms of durability, the present invention exhibits excellent weather resistance and overcomes the bottleneck of severe cold environment.

[0084] After 300 severe freeze-thaw cycles and de-icing salt corrosion, Examples 1 and 2 showed extremely low mass loss rates (0.8% and 0.5%, respectively) and intact appearance; while ordinary concrete showed a loss rate as high as 5.2%, far exceeding the specification limit, with severe surface spalling. This demonstrates the synergistic effect of the aluminoferrite cement system, basalt fiber, and polymer powder, which greatly enhances the material's resistance to freeze-thaw cycles and salt corrosion, specifically addressing the spalling and cracking problems caused by the application of de-icing agents in northern winters. Ordinary concrete's severely insufficient durability under these conditions is a direct cause of frequent road maintenance.

[0085] (iv) In terms of overall benefits, the present invention achieves the ultimate goal of reducing maintenance costs.

[0086] Based on its high early strength, high durability, and excellent mechanical properties, the repair structure of this invention has a longer service life and requires less frequent maintenance. Examples 1 and 2 can significantly reduce maintenance costs by more than 50%. This not only saves direct material and labor costs but also avoids the huge indirect economic losses caused by repeated road closures, resulting in significant socio-economic benefits.

[0087] In summary, the repair materials of the present invention represented by Examples 1 and 2 are superior to ordinary performance concrete in all three key properties: early strength, mechanical compatibility, and long-term durability.

[0088] Example 1, with minimal fiber and polymer usage, fully meets and far exceeds the technical requirements for rapid repair in frigid regions, making it a cost-effective and preferred solution.

[0089] Example 2: By optimizing the formula, it achieves better performance in all aspects, especially in early strength and corrosion resistance, making it suitable for key projects with higher requirements (such as airport runways).

[0090] Therefore, through the innovation of the material system, this invention has successfully solved the technical dilemma of "slow repair, poor repair, and repeated repair" in the road repair of ordinary concrete in cold regions, and achieved a unity of durability, construction efficiency and economy.

[0091] The technical solutions disclosed and proposed in this invention can be implemented by those skilled in the art by appropriately modifying the conditions and routes, etc. Although the methods and preparation techniques of this invention have been described through preferred embodiments, those skilled in the art can obviously modify or recombine the methods and technical routes described herein without departing from the content, spirit, and scope of this invention to achieve the final preparation technique. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the spirit, scope, and content of this invention.

Claims

1. A ferroaluminate cement fine stone fiber concrete repair material, characterized in that, include: Ferroaluminate cement; The material with the highest bulk dry density configured using continuously graded fine stone as aggregate; Fiber materials; polymer; water; Water-reducing agent; Of this, the amount of fiber material incorporated, based on the total mass of the repair materials, is 0.5-2.0 kg / m³. 3 ; Of which, based on the total mass of the repair materials, the weight percentage of solids in the polymer is 3-10%; The water-to-binder ratio is ≤0.

40.

2. The aluminoferrite cement fine stone fiber concrete repair material according to claim 1, characterized in that, The diameter of the aggregate is no greater than 8mm; the gradation of the aggregate meets the following requirements: ≥85% passing rate on a 4.75mm sieve and 40-60% passing rate on a 0.6mm sieve.

3. The aluminoferrite cement fine stone fiber concrete repair material according to claim 1, characterized in that, The fiber material is at least one of basalt fiber and end-hook steel fiber, or a mixture of at least one of basalt fiber and end-hook steel fiber and polypropylene fiber.

4. The aluminoferrite cement fine stone fiber concrete repair material according to claim 1, characterized in that, The fiber material has a length of 12-18 mm and a diameter of 15-25 μm.

5. The aluminoferrite cement fine stone fiber concrete repair material according to claim 1, characterized in that, The polymer is a redispersible acrylate powder or styrene-butadiene latex.

6. The aluminoferrite cement fine stone fiber concrete repair material according to claim 1, characterized in that, 28-day compressive strength ≥50MPa, elastic modulus 28-35GPa.

7. A method for preparing the aluminoferrite cement fine stone fiber concrete repair material as described in any one of claims 1-6, characterized in that, First, dry mix the material with the highest bulk dry density and the fiber material for 1-2 minutes, then add the aluminoferrite cement and polymer and mix for 1-2 minutes, and finally add water and water-reducing agent and stir for 2-3 minutes until the fluidity is ≥180mm.

8. A composite structure, characterized in that, From bottom to top, it includes an existing concrete layer, an interface agent layer, and a repair layer composed of the iron aluminate cement fine stone fiber concrete repair material as described in any one of claims 1-6, wherein the elastic modulus deviation of the concrete layer, the interface agent layer, and the repair layer is ≤10%.

9. A paving process for the composite structure as described in claim 8, characterized in that, Includes the following steps: S1. Base surface treatment: Mechanically mill the damaged concrete down to a solid base layer, and cut vertical seams along the edge of the repair area; use high-pressure water jets to wash the base surface to remove dust, oil, and loose particles; allow it to air dry until it is surface dry. S2, Interface Strengthening: Apply an interface agent to form a continuous film layer, and proceed to the next process immediately after surface drying; S3. Repair layer paving: Prepare the iron aluminate cement fine stone fiber concrete repair material and form a repair layer by spraying or manual paving; S4. Curing: After the repair layer has initially set, cover it with a film and spray water for curing for ≥7 days. During winter construction, erect a shed for insulation.

10. The paving process for a composite structure according to claim 9, characterized in that, In S1, the vertical seam depth is ≥20mm; the pressure of the high-pressure water jet is ≥20MPa; the moisture content in the surface-dried state is ≤10%; and natural air drying is assisted by a blower for drying. In S2, the interface agent is a two-component epoxy interface agent or polymer cement slurry; the application rate of the interface agent is 0.4-0.6 kg / m². 2 The coating thickness is 1-2mm; In S3, the spraying paving is carried out in layers using a wet spraying machine, with the spray gun vertically 0.8-1.2m from the spraying base surface, the air pressure 0.4-0.6MPa, and the layer thickness ≤5cm; the manual paving is carried out by pouring into the mold, with a scraper to assist in leveling, and the use of vibratory rods for tamping is prohibited. In S4, after initial setting, cover with a water-retaining membrane and spray water for curing at a temperature of 5-30℃ for ≥7 days; during winter construction, erect an insulated shed and use a hot air blower to maintain an ambient temperature of ≥10℃; light traffic is allowed when the strength is ≥30MPa after 24 hours, and heavy traffic is allowed when the strength is ≥45MPa after 7 days.

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