Marine environment mass concrete construction and crack repairing method

Abstract

The invention relates to a marine environment mass concrete construction and crack repairing method, which comprises the following steps: in a mass concrete construction stage, carrying out aggregate precooling, carrying out layered intermittent pouring by using the precooled aggregate, and carrying out cooling treatment at the same time, so that the internal and external temperature difference is controlled within 20 DEG C; if cracks appear on the mass concrete, a polymer modified cement-based composite material is prepared for repairing, the polymer modified cement-based composite material comprises composite gel, a macromolecular tackifier and aggregate, the composite gel is based on 60%-70% of Portland cement, and 5%-8% of nano silicon powder and 10%-15% of fly ash are doped; the macromolecular adhesive comprises 0.5%-1.2% of polyacrylamide or 2%-3% of epoxy resin emulsion. When the scheme is used for repairing marine mass buildings, the overall viscosity of concrete can be improved, the internal and external temperature difference of the concrete is reduced, and the overall impermeability of the concrete repairing material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ocean engineering construction, and particularly relates to a method for constructing mass concrete in a marine environment and repairing cracks. Background Art

[0002] In a marine environment, mass concrete structures (such as offshore platforms, port terminals, cross-sea bridge foundations, etc.) are affected by complex factors such as long-term seawater erosion, wet-dry cycles, temperature changes, and wave impacts, and are extremely prone to cracking; these cracks will not only weaken the strength and durability of the concrete structure, but may also cause steel corrosion, seriously threatening the structural safety and service life.

[0003] Concrete cracks are physical structure changes caused by the action of internal and external factors of the concrete structure, and cracks are the main reasons for the reduction of the bearing capacity, durability, and waterproofness of concrete structures; concrete in a marine environment is more likely to be corroded and cracked and peeled due to long-term intrusion of seawater and sea breeze. Concrete cracks provide channels for erosion media such as chloride ions, carbon dioxide, and sulfate radicals, which will accelerate the corrosion of materials and the failure of concrete structures, and even bring huge economic losses and serious safety problems.

[0004] In a marine environment, mass concrete structures are prone to cracking due to long-term influence of factors such as chloride ion erosion, wet-dry cycles, freeze-thaw damage, and wave impacts, so repair is required. The traditional repair methods have the following problems:

[0005] 1. Insufficient viscosity: The adhesion between the conventional repair concrete and the old matrix is weak, and secondary cracks are easily formed at the interface;

[0006] 2. Out-of-control temperature stress: The heat of hydration of mass concrete accumulates, resulting in a large temperature difference between the inside and outside, causing temperature cracks;

[0007] 3. Poor durability: The impermeability of the repair material in a marine environment is insufficient, accelerating the corrosion of internal steel bars. Summary of the Invention

[0008] In order to solve the above problems, the purpose of the present invention is to provide a method for constructing mass concrete in a marine environment and repairing cracks, which can improve the overall viscosity of concrete, reduce the temperature difference between the inside and outside of concrete, and improve the overall impermeability of the concrete repair material when repairing large marine buildings.

[0009] A method for constructing mass concrete in a marine environment and repairing cracks includes the following steps:

[0010] Stage 1, construction of mass concrete, including,

[0011] Preparing aggregates: Using low-heat Portland cement and compounding 30%-40% mineral powder;

[0012] Pre-cooled aggregate: Before construction, cool the aggregate to below 10°C and control the initial pouring temperature ≤ 25°C;

[0013] Layered intermittent pouring: Use the pre-cooled aggregate, pour in layers with a thickness of less than 50 cm for each layer and an interval time of more than 4 h, and conduct layered intermittent pouring while performing temperature reduction treatment to control the internal and external temperature difference within 20°C;

[0014] In the second stage, if cracks appear on the mass concrete, repair the cracks according to the following steps, including,

[0015] Preparation of grouting repair materials: Prepare polymer-modified cement-based composites, including composite gels, polymer thickeners, and aggregates. The composite gel is based on 60%-70% portland cement, and is compounded with 5%-8% nano-silica powder and 10%-15% fly ash; the polymer binder includes 0.5%-1.2% polyacrylamide or 2%-3% epoxy resin emulsion; the aggregate uses manufactured sand with a fineness modulus of 2.6-2.8 and continuously graded gravel of 5-20 mm, and control the sand ratio at 38%-42%;

[0016] Use the grouting repair materials to perform grouting repair on the cracks after pretreatment.

[0017] Preferably, in the first stage, it further includes: embedding wireless temperature sensors during the pouring process to monitor the internal temperature in real time.

[0018] Preferably, in the first stage, it further includes: After the layered intermittent pouring is completed, use an inner water retention film and an outer reflective heat insulation film to cure the concrete pouring body.

[0019] Preferably, in the second stage, before grouting repair, perform surface pretreatment on the cracks, including,

[0020] Use a high-pressure water gun or air compressor to remove the surface and inside of the cracks at a pressure of ≥ 200 MPa;

[0021] For cracks with a width > 0.5 mm, use mechanical grinding or manual chiseling to groove along the crack direction;

[0022] For micro-cracks with a width < 0.3 mm, use chemical corrosion or laser treatment to expand the crack opening.

[0023] Preferably, the grooving along the crack direction is specifically to chisel a "V"-shaped or "U"-shaped groove with a width of 3000 mm and a depth of 4500 mm along the crack direction.

[0024] Preferably, the cooling water pipe uses a pre-embedded S-shaped pipe.

[0025] Preferably, the spacing between the cooling water pipes is 1.2 m × 1.2 m.

[0026] Compared with the prior art, the present invention provides a construction method for repairing large-volume concrete cracks in a marine environment, having the following beneficial effects:

[0027] 1. In the above solution, for the construction method for repairing large-volume concrete cracks in a marine environment, by using low-heat Portland cement and compounding 30%-40% mineral powder, the peak value of hydration heat is reduced by 35%-40% (compared with ordinary Portland cement). Combining pre-cooled aggregate (≤10 °C) and the layered intermittent pouring process, the maximum internal temperature of the concrete is controlled below 55 °C, and the internal and external temperature difference is ≤20 °C, effectively inhibiting temperature stress cracks; by burying wireless temperature sensors and an intelligent control system, the change of the internal temperature field of the concrete is monitored in real time, and the flow rate of the cooling water pipes is dynamically adjusted (circulating seawater at 15 °C - 20 °C is passed through), avoiding the problem of excessive temperature difference caused by the lag of manual monitoring; using a double-layer curing film (inner water-retaining film + outer reflective heat-insulating film) to block the surface temperature rise caused by direct sunlight, while keeping the humidity constant, avoiding shrinkage cracks, and ensuring the volume stability of the repair layer in the marine tidal wet-dry cycling environment.

[0028] 2. By adopting a composite cementitious system (Portland cement + nano-silica powder + fly ash) and a polymer thickening agent (polyacrylamide or epoxy resin emulsion), the bonding strength between the newly poured concrete and the old substrate is increased to ≥3.5 MPa (≤2.5 MPa in the traditional method), avoiding secondary cracks generated at the interface between the repair layer and the substrate due to stress concentration, and significantly improving the interfacial bonding strength; the micro-filling effect of nano-silica powder (5%-8%) and the pozzolanic reaction of fly ash (10%-15%) act synergistically to refine the pore structure of the concrete and reduce the chloride ion permeability (chloride ion diffusion coefficient ≤ 2.0×10- 12 m 2 / s), significantly improving the anti-marine corrosion ability.

[0029] 3. Through optimizing the aggregate gradation (manufactured sand with fineness modulus of 2.6 - 2.8 + continuously graded gravel of 5 - 20 mm) and controlling the sand ratio (38%-42%), the bleeding phenomenon of the concrete is reduced, the cohesiveness is improved, and the uniform and dense filling of the repair material on the complex base surface is ensured. Detailed Embodiment

[0030] The embodiments of the present invention will be described in detail below.

[0031] The present invention relates to a construction and crack repair method for large-volume concrete in a marine environment, and improvements are made in both the concrete construction stage and the crack repair stage.

[0032] The first stage is the construction method for large-volume concrete in a marine environment, including:

[0033] Prepare the aggregate: Use low-heat Portland cement and compound admixture of 30%-40% mineral powder;

[0034] Pre-cool the aggregate: Cool the aggregate to below 10°C before construction, and control the initial pouring temperature ≤ 25°C;

[0035] Lay in layers with intermittent pouring: Use the pre-cooled aggregate, pour in layers with each layer thickness less than 50 cm and the interval time greater than 4 h, and carry out temperature reduction treatment at the same time to control the temperature difference between inside and outside within 20°C.

[0036] In this stage, by using low-heat Portland cement and compound admixture of 30%-40% mineral powder, the peak value of hydration heat is reduced by 35%-40% (compared with ordinary Portland cement). Combining with pre-cooled aggregate (≤ 10°C) and the process of laying in layers with intermittent pouring, the highest temperature inside the concrete is controlled below 55°C, and the temperature difference between inside and outside ≤ 20°C, effectively inhibiting temperature stress cracks. Thus, cracks can be prevented during the construction stage of mass concrete.

[0037] In a specific embodiment, seawater at 15°C - 20°C is circulated in the cooling water pipes, and the cooling water pipes are used for circulating cooling, which can effectively utilize the marine environment resources for temperature reduction treatment. In an alternative embodiment, the cooling water pipes are pre-buried in an S-shaped pipeline, which can fully contact with the concrete. In a preferred embodiment, the spacing between the cooling water pipes is 1.2 m × 1.2 m. Such a setting is also to arrange sufficient cooling water pipes in the mass concrete to ensure its cooling efficiency. As a preferred embodiment, the temperature reduction treatment also includes the combination of one or more of the following methods: blowing cooling, adding ice to reduce temperature. By combining the above temperature reduction methods with the method of circulating cooling of the cooling water pipes, rapid temperature reduction can be achieved.

[0038] Among them, in order to accurately know the internal temperature of the concrete during the pouring process, wireless temperature sensors are pre-buried during the pouring process in this embodiment to monitor the internal temperature in real time, avoiding the problem of excessive temperature difference caused by the lag of manual monitoring. Taking the cooling of the concrete by using the cooling water pipes as an example, according to the internal temperature of the concrete monitored in real time, the flow rate of the cooling water pipes can be dynamically adjusted, so as to accurately and timely adjust the internal temperature of the concrete by means of temperature reduction treatment.

[0039] After the pouring is completed, the concrete pouring body is cured with an inner water-retaining film and an outer reflective heat-insulating film to avoid cracks caused by the evaporation of surface moisture and the increase in temperature due to direct sunlight.

[0040] During the later use process, when cracks appear in the mass concrete, repair according to the steps of stage two.

[0041] Crack Detection and Evaluation: Adopt detection technologies related to ultrasonic testing and infrared thermal imaging, conduct inspections in combination with the specific conditions of the large-volume marine construction site, and determine the distribution of the position, length, width, and depth of the cracks; and based on the data of the position, length, width, and depth of the cracks, evaluate the cracks to determine the repair priority and repair plan;

[0042] Pre-treatment of the crack surface: Use a high-pressure water gun or air compressor to remove impurities such as seawater sediment, marine organism attachment, and loose concrete on the crack surface and inside at a pressure of ≥200 MPa;

[0043] For cracks with a width > 0.5 mm, use mechanical grinding or manual grooving to cut a "V"-shaped or "U"-shaped groove with a width of 3000 mm and a depth of 4500 mm along the crack direction; setting the grooving shape as above can enable the repair material to be evenly and densely filled on the complex base surface.

[0044] For micro-cracks with a width < 0.3 mm, use chemical corrosion or laser treatment to expand the crack opening and enhance the penetration effect of the repair material.

[0045] Preparation of grouting repair material: Prepare a polymer-modified cement-based composite material, including a composite gel, a polymer thickener, and aggregates. The composite gel is based on 60%-70% portland cement, and is compounded with 5%-8% nano-silica powder and 10%-15% fly ash; the polymer binder includes 0.5%-1.2% polyacrylamide or 2%-3% epoxy resin emulsion; the aggregates use manufactured sand with a fineness modulus of 2.6-2.8 and continuously graded gravel of 5-20 mm, and control the sand ratio at 38%-42%.

[0046] Use the above grouting repair material to carry out grouting repair on the pre-treated cracks.

[0047] Adopt a composite cementitious system (portland cement + nano-silica powder + fly ash) and a polymer thickener (polyacrylamide or epoxy resin emulsion) to increase the bonding strength between the newly poured concrete and the old matrix to ≥3.5 MPa (the traditional method ≤2.5 MPa), avoid secondary cracks caused by stress concentration at the interface between the repair layer and the matrix, and can significantly improve the interface bonding strength; the micro-filling effect of nano-silica powder (5%-8%) and the pozzolanic reaction of fly ash (10%-15%) act synergistically to refine the pore structure of the concrete and reduce the chloride ion permeability (chloride ion diffusion coefficient ≤2.0×10- 12 m 2 / s), significantly improving the anti-marine corrosion ability.

[0048] Moreover, through aggregate gradation optimization (machine-made sand with fineness modulus of 2.6 - 2.8 + continuously graded gravel of 5 - 20 mm) and sand ratio control (38% - 42%), the bleeding phenomenon of concrete is reduced, the cohesiveness is improved, and the uniform and dense filling of the repair material on the complex base surface is ensured.

[0049] Thus, the above solution can improve the overall viscosity of concrete, reduce the temperature difference between the inside and outside of the concrete, and improve the overall impermeability of the concrete repair material during the construction and repair of large-volume marine buildings.

[0050] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising a..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0051] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for construction and crack repair of large-volume concrete in a marine environment, characterized in that: The following steps are involved: Phase 1, mass concrete construction, includes: Prepare aggregate: Use low-heat silicate cement and add 30%-40% mineral powder; Pre-cooling aggregate: cool the aggregate to below 10℃ before construction, and control the initial pouring temperature to ≤25℃; Layered intermittent pouring: using the pre-cooled aggregate, with each layer thickness less than 50 cm and an interval time greater than 4 hours, layered intermittent pouring, while cooling down, so that the maximum temperature inside the concrete is controlled at 55°C, and the temperature difference between the inside and outside is controlled within 20°C; In the second stage, if cracks appear on the mass concrete, the cracks are repaired according to the following steps, including: Preparation of grouting repair materials: Prepare polymer-modified cement-based composite materials, including composite gel, polymer viscosity enhancer and aggregate. The composite gel is based on 60%-70% silicate cement, mixed with 5%-8% nano silicon powder and 10%-15% fly ash; the polymer adhesive includes 0.5%-1.2% polyacrylamide or 2%-3% epoxy resin emulsion; the aggregate is made of machine-made sand with a fineness modulus of 2.6-2.8 and 5-20mm continuously graded crushed stone, and the sand ratio is controlled at 38%-42%; The grouting repair material is used to carry out grouting repair on the pre-treated cracks.

2. The method for construction and crack repair of large-volume concrete in a marine environment according to claim 1, characterized in that: Phase 1 also includes: Wireless temperature sensors are embedded during the pouring process to monitor the internal temperature in real time.

3. The method for construction and crack repair of large-volume concrete in a marine environment according to claim 1, characterized in that: Phase 1 also includes: After the intermittent pouring in layers is completed, the concrete casting body is maintained with an inner water-retaining film and an outer reflective heat-insulating film.

4. The method for construction and crack repair of large-volume concrete in a marine environment according to claim 1, characterized in that: In the second stage, the crack surface is prepared before grouting, including: Use a high-pressure water gun or air compressor to clean the surface and interior of the crack at a pressure of ≥200MPa; For cracks with a width of more than 0.5 mm, mechanical grinding or manual grooving is used to create grooves along the crack direction; For fine cracks with a width of less than 0.3mm, chemical dissolution or laser treatment is used to expand the crack opening.

5. The method for construction and crack repair of large-volume concrete in a marine environment according to claim 4, characterized in that: The grooving along the crack direction specifically involves digging a "V"-shaped or "U"-shaped groove with a width of 3000 mm and a depth of 4500 mm along the crack direction.

6. The method for construction and crack repair of large-volume concrete in a marine environment according to claim 1, characterized in that: The temperature reduction treatment includes: utilizing a cooling water pipe for circulating temperature reduction.

7. The method for construction and crack repair of large-volume concrete in a marine environment according to claim 6, characterized in that: The cooling water pipe adopts a pre-buried S-shaped pipe.

8. The method for construction and crack repair of large-volume concrete in a marine environment according to claim 6, characterized in that: The spacing between the cooling water pipes is 1.2 m×1.2 m.

9. The method for construction and crack repair of large-volume concrete in a marine environment according to claim 6, characterized in that: The cooling treatment also includes a combination of one or more of the following methods: air cooling, ice cooling.