Cement-based repair material and repair method for freeze-thaw damaged concrete

Abstract

The application provides a cement-based repairing material and a repairing method for freeze-thaw damaged concrete, and relates to the technical field of building materials. Specifically, the cement-based repairing material comprises a bonding layer material, a ceramsite layer material and a protective layer material; the bonding layer material comprises cement, silica fume, metakaolin, quartz sand, nano-SiO2, nano-Fe2O3, a water reducing agent and water; the ceramsite layer material comprises ceramsite; and the protective layer material comprises cement, silica fume, metakaolin, quartz sand, polypropylene plastic steel fiber, a water reducing agent and water. The damaged part is treated, and then the bonding layer, the ceramsite layer and the protective layer are sequentially arranged to repair. After being repaired by the repairing material and the repairing method, the new-old interface bonding strength is high, the frost resistance is good, and the tensile strength of the protective layer is high, so that the further freeze-thaw damage of the old structure can be effectively prevented, and the service life is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a cement-based repairing material for freeze-thaw damaged concrete and a repairing method. BACKGROUND

[0002] A large part of the damage of the bridge in the use process is caused by extreme environment, including earthquake, strong wind, low temperature, etc. The temperature in the alpine region is low, and the climate characteristics of large diurnal temperature range cause the bridge structure to face serious freeze-thaw cycle effect. The freeze-thaw cycle effect brings many negative effects to the bridge, including damage, crack, spalling of concrete, corrosion of steel bars, etc. The damage has certain influence on the normal use performance of the bridge, and therefore, a high-performance material is needed to repair the freeze-thaw damaged parts.

[0003] In the existing repairing technology, there are always pores between the repairing material and the old structure surface, and the water in the pores is easy to form freeze-thaw load at low temperature, which reduces the repairing effect; meanwhile, the existing repairing material has poor frost resistance, and needs continuous maintenance in the later period.

[0004] Therefore, the present application is proposed. SUMMARY

[0005] The first object of the present application is to provide a cement-based repairing material for freeze-thaw damaged concrete, which has high interfacial bonding strength with the old structure, good frost resistance, and good toughness, and can avoid the deformation caused by thermal expansion and cold shrinkage of different materials.

[0006] The second object of the present application is to provide a repairing method for freeze-thaw damaged concrete, which uses the cement-based repairing material for repairing, and has the advantages of simple operation, high interfacial bonding strength of the repaired concrete, high freeze-thaw cycle times, and high tensile strength of the protective layer.

[0007] In order to achieve the above objects of the present application, the following technical solutions are adopted:

[0008] The first aspect of the present application provides a cement-based repairing material for freeze-thaw damaged concrete, which comprises a bonding layer material, a ceramsite layer material, and a protective layer material.

[0009] The bonding layer material comprises cement, silica fume, metakaolin, quartz sand, nano-SiO2, nano-Fe2O3, water reducing agent, and water.

[0010] The ceramsite layer material comprises ceramsite.

[0011] The protective layer material comprises cement, silica fume, metakaolin, quartz sand, polypropylene plastic steel fiber, water reducing agent, and water.

[0012] The cement-based repairing material has high bonding strength of the bonding layer, the ceramsite layer can improve the frost resistance, the toughness of the protection layer is good, the bonding strength of the old interface is above 2MPa, can withstand more than 250 freeze-thaw cycles, the tensile strength of the protection layer is above 10MPa, and the deformation caused by thermal expansion and cold shrinkage of different materials can be avoided.

[0013] The second aspect of the present application provides a repairing method of freeze-thaw damaged concrete, which uses the cement-based repairing material to repair, and comprises the following steps:

[0014] (1) damaged part treatment: the damaged part is completely chiseled, loose stones and loose cement stones are cleaned, and the stones of the undamaged layer are exposed;

[0015] (2) setting the bonding layer: the bonding layer material is mixed to form a slurry, and the slurry is sprayed to the surface of the treated damaged concrete member by using a concrete spraying machine, and the thickness is 20-50mm;

[0016] (3) setting the ceramsite layer: the ceramsite is pre-wetted to make the water content of the ceramsite be 1-3%, and the pre-wetted ceramsite is sprayed to the bonding layer by using a sand blasting machine before the final setting of the bonding layer, so that the ceramsite is embedded on the bonding layer;

[0017] (4) setting the protection layer: the protection layer material is mixed to form a slurry, and is layered and applied on the surface of the ceramsite layer, and the thickness is 35-50mm.

[0018] The repairing method is simple in operation, and the bonding strength of the new and old interface of the repaired concrete is high, the freeze-thaw cycle times are high, the tensile strength of the protection layer is high, the further freeze-thaw damage of the old structure can be effectively prevented, and the service life can be prolonged, and the maintenance in the later period is free.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] (1) the cement-based repairing material provided by the present application adds nano-SiO2 and nano-Fe2O3 in the bonding layer material, can make the Ca(OH)2 which is not completely hydrated in a certain depth range on the surface of the old structure secondary hydrate, make the bonding surface strength rise, improve the bonding strength of the repairing material and the old concrete bonding surface, the ceramsite is used as coarse aggregate, and the rough surface and the internal porous characteristics can better combine with the repairing material, and the internal pores can improve the frost resistance of the material, and the polypropylene plastic steel fiber is added in the protection layer material, so that the toughness of the protection layer can be enhanced, and the cracking caused by thermal expansion and cold shrinkage of different materials can be prevented.

[0021] (2) The repair method provided by the application first cleans up the loose stones and cement stones of the damaged part, applies a bonding layer containing nano-SiO2 and nano-Fe2O3 on the surface of the treated damaged concrete member, and improves the bonding strength of the new and old interfaces; before the final setting of the bonding layer, the pre-wetted ceramsite is sprayed on the bonding layer alone, and compared with directly mixing the ceramsite into the bonding layer slurry, the uniformity of the distribution of the separately sprayed ceramsite is higher, and the frost resistance is better; the protective layer containing polypropylene plastic steel fiber is arranged on the surface of the ceramsite layer, which can improve the toughness of the protective layer and avoid the deformation and cracking caused by the thermal expansion and cold contraction of different materials. The method provided by the application can make the bonding strength of the new and old interfaces reach 2.86 MPa, can withstand 300 times of freeze-thaw cycles, and the tensile strength of the protective layer can reach 11.3 MPa. After the method is used for repair, the further freeze-thaw damage of the old structure can be effectively prevented, and the service life can be prolonged, and maintenance is not required in the later period. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0023] Figure 1 The cross-sectional view of the bonding surface between the old concrete and the repair material provided by the embodiment of the present application is shown in the figure.

[0024] Figure 2 The schematic diagram of the ceramsite pre-wetting process provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be described clearly and completely in combination with the specific embodiments below, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the present application, not all the embodiments, and should not be regarded as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The specific conditions are not indicated in the embodiments, and the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments used are not indicated by the manufacturer, and are conventional products that can be purchased on the market.

[0026] The first aspect of the present application provides a cement-based repair material for freeze-thaw damaged concrete, which comprises a bonding layer material, a ceramsite layer material and a protective layer material.

[0027] The binding layer material comprises cement, silica fume, metakaolin, quartz sand, nano-SiO2, nano-Fe2O3, water reducing agent and water.

[0028] The ceramsite layer material comprises ceramsite.

[0029] The protective layer material comprises cement, silica fume, metakaolin, quartz sand, polypropylene plastic steel fiber, water reducing agent and water.

[0030] The present application divides the repair material into binding layer material, ceramsite layer material and protective layer material, and designs the formula components of each layer according to the different roles of each layer material, improves the overall performance of the repair material, and makes the repair material achieve the technical effects of high bonding strength of new and old interfaces, good frost resistance, not easy to crack and long service life.

[0031] As shown in Figure 1 The binding layer material directly contacts the surface of the old concrete member, and the addition of nano-SiO2 and nano-Fe2O3 as the binding layer components can improve the bonding strength of the repair material and the old concrete interface. Nano-SiO2 and nano-Fe2O3 can make the Ca(OH)2 in a certain depth range on the surface of the old structure secondary hydrate, so as to increase the bonding surface strength. The ceramsite layer is uniformly embedded in the binding layer. The ceramsite, as a coarse aggregate, has the characteristics of rough surface and internal pores, which can better combine with the repair material. In addition, the internal pores can improve the frost resistance of the material. In addition, the ceramsite is embedded in the binding layer, which can enhance the effect of nano-materials compared with stones, thereby increasing the strength of the binding layer. The protective layer is located at the outermost side of the repaired structure, and the addition of polypropylene plastic steel fiber in the formula components of the protective layer can improve the toughness of the protective layer, increase the tensile strength, avoid deformation and cracking caused by thermal expansion and cold shrinkage of different materials, and effectively prevent further freeze-thaw damage to the old structure. The cement-based repair material for freeze-thaw damaged concrete provided by the present application has high bonding strength between the old interface, good frost resistance, good toughness and is not easy to crack, which can effectively prevent further freeze-thaw damage to the old structure, prolong the service life and be maintenance-free in the later period.

[0032] In some specific embodiments of the present application, the binding layer material comprises cement 680-750 parts by mass, silica fume 180-200 parts, metakaolin 50-80 parts, quartz sand 600-700 parts, nano-SiO2 5-10 parts, nano-Fe2O3 5-10 parts, water reducing agent 10-15 parts and the balance of water, and the water-binder ratio is 0.20-0.23.

[0033] As in different embodiments, the amount of cement in the binding layer material includes but is not limited to any one of 680 parts, 690 parts, 700 parts, 710 parts, 720 parts, 730 parts, 740 parts, 750 parts or a range consisting of any two of them; the amount of silica fume includes but is not limited to any one of 180 parts, 185 parts, 190 parts, 195 parts, 200 parts or a range consisting of any two of them; the amount of metakaolin includes but is not limited to any one of 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts or a range consisting of any two of them; the amount of quartz sand includes but is not limited to any one of 600 parts, 620 parts, 640 parts, 650 parts, 660 parts, 680 parts, 700 parts or a range consisting of any two of them; the amount of nano-SiO2 includes but is not limited to any one of 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts or a range consisting of any two of them; the amount of nano-Fe2O3 includes but is not limited to any one of 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts or a range consisting of any two of them; the amount of water reducing agent includes but is not limited to any one of 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts or a range consisting of any two of them; the water-binder ratio includes but is not limited to any one of 0.20, 0.21, 0.22, 0.23 or a range consisting of any two of them.

[0034] In some embodiments of the application, the ceramic layer material includes, in parts by mass, ceramic 200-300.

[0035] As in different embodiments, the amount of ceramic in the ceramic layer includes but is not limited to any one of 200 parts, 220 parts, 240 parts, 250 parts, 260 parts, 280 parts, 300 parts or a range consisting of any two of them.

[0036] In some embodiments of the application, the protective layer material includes, in parts by mass, cement 650-700, silica fume 140-160, metakaolin 80-100, quartz sand 900-1000, polypropylene plastic steel fiber 15-25, water reducing agent 10-15 and the balance water, with a water-binder ratio of 0.19-0.21.

[0037] The amount of cement in the protective layer material includes, but is not limited to, any one of 650 parts, 660 parts, 670 parts, 680 parts, 690 parts, 700 parts or a range consisting of any two of them; the amount of silica fume includes, but is not limited to, any one of 140 parts, 145 parts, 150 parts, 155 parts, 160 parts or a range consisting of any two of them; the amount of metakaolin includes, but is not limited to, any one of 80 parts, 85 parts, 90 parts, 95 parts, 100 parts or a range consisting of any two of them; the amount of quartz sand includes, but is not limited to, any one of 900 parts, 920 parts, 940 parts, 950 parts, 960 parts, 980 parts, 1000 parts or a range consisting of any two of them; the amount of polypropylene plastic steel fiber includes, but is not limited to, any one of 15 parts, 18 parts, 20 parts, 22 parts, 25 parts or a range consisting of any two of them; the amount of water reducing agent includes, but is not limited to, any one of 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts or a range consisting of any two of them; the water-binder ratio includes, but is not limited to, any one of 0.19, 0.20, 0.21 or a range consisting of any two of them.

[0038] In some embodiments of the present application, the cement includes ordinary Portland cement, and the strength grade is P·O42.5 or P·O52.5.

[0039] In some embodiments of the present application, the silica fume has a silicon content of more than 95% by mass fraction.

[0040] In some embodiments of the present application, the metakaolin has an activity of S105 grade or above, such as S105 grade, S115 grade, etc.

[0041] In some embodiments of the present application, the ceramsite has a particle size of 5-15 mm, such as any one of 5 mm, 7 mm, 9 mm, 10 mm, 11 mm, 13 mm and 15 mm or a range consisting of any two of them; a saturated water absorption rate of 5-6%, such as any one of 5%, 5.2%, 5.5%, 5.8%, 6% or a range consisting of any two of them; an apparent density of 1000-1200 kg / m 3 , such as any one of 1000 kg / m 3 , 1100 kg / m 3 , 1200 kg / m 3 or a range consisting of any two of them; and a cylinder compressive strength of more than 8 MPa, such as 8.5 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, etc.

[0042] In some embodiments of the present application, the quartz sand has a particle size of 150-50 μm, for example, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, or a range between any two of these values.

[0043] In some embodiments of the present application, the nano-SiO2 has an average particle size of 10-30 nm, for example, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, or a range between any two of these values, white powder, a specific surface area of 200-240 m 2 / g, for example, 200 m 2 / g, 210 m 2 / g, 220 m 2 / g, 230 m 2 / g, 240 m 2 / g, or a range between any two of these values, a density of 2.2-2.6 g / cm 3 , for example, 2.2 g / cm 3 , 2.3 g / cm 3 , 2.4 g / cm 3 , 2.5 g / cm 3 , 2.6 g / cm 3 , or a range between any two of these values, a spherical crystal phase.

[0044] In some embodiments of the present application, the nano-Fe2O3 has an average particle size of 10-30 nm, for example, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, or a range between any two of these values, red powder, a specific surface area of 100-120 m 2 / g, for example, 100 m 2 / g, 105 m 2 / g, 110 m 2 / gm 2 / g, 115 m 2 / g, 120 m 2 / g, or a range between any two of these values, a density of 5.1-5.3 g / cm 3 , for example, 5.1 g / cm 3 , 5.2 g / cm 3 , 5.3 g / cm 3 , or a range between any two of these values, an α crystal phase.

[0045] In some embodiments of the present application, the polypropylene plastic steel fiber has a length of 5-8 mm, such as any one of 5 mm, 6 mm, 7 mm, 8 mm or a range between any two of them, and a tensile strength greater than 500 MPa, such as 510 MPa, 520 MPa, 530 MPa, 540 MPa, 550 MPa, etc.

[0046] In some embodiments of the present application, the water reducing agent is a polycarboxylic acid water reducing agent, and the water reducing rate is greater than or equal to 30%, such as 30%, 35%, 40%, 45%, etc.

[0047] The second aspect of the present application provides a method for repairing freeze-thaw damaged concrete, which uses the cement-based repair material as described above, and comprises the following steps:

[0048] (1) damaged part treatment: the damaged part is completely chiseled, loose stones and loose cement stones are cleaned, and the stones of the undamaged layer are exposed;

[0049] (2) setting a bonding layer: the bonding layer material is mixed to form a slurry, and the slurry is sprayed onto the surface of the treated damaged concrete member using a concrete sprayer, with a thickness of 20-50 mm, such as any one of 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm or a range between any two of them;

[0050] (3) setting a ceramsite layer: the ceramsite is pre-wetted to have a water content of 1-3%, such as any one of 1%, 2%, 3% or a range between any two of them, and before the final setting of the bonding layer, the pre-wetted ceramsite is sprayed onto the bonding layer using a sandblasting machine, so that the ceramsite is embedded in the bonding layer;

[0051] (4) setting a protective layer: the protective layer material is mixed to form a slurry, which is layered and applied on the surface of the ceramsite layer, with a thickness of 35-50 mm, such as any one of 35 mm, 40 mm, 45 mm, 50 mm or a range between any two of them.

[0052] The repair method provided by the present application first cleans the loose stones and cement stones of the damaged part, and applies a bonding layer containing nano-SiO2 and nano-Fe2O3 on the surface of the treated damaged concrete member, thereby improving the bonding strength of the new and old interfaces.

[0053] The pre-wetted ceramsite is sprayed on the bonding layer alone before the final setting after the initial setting of the bonding layer, and the uniformity of the distribution of the ceramsite is high, and the frost resistance is better. If the ceramsite is directly mixed with the bonding layer and used together, due to the small density of the ceramsite, the ceramsite and the mixture cannot be uniformly sprayed during the spraying process, and the ceramsite is not uniformly distributed in the bonding layer, which will lead to a decrease in the overall performance of the bonding layer.

[0054] By pre-wetting treatment of the ceramsite, the water absorption rate of the ceramsite is controlled in a proper range, the water absorption capacity and water release capacity of the ceramsite are balanced, the internal curing effect is achieved, and excessive free water is not generated. If the water content of the ceramsite is too high, water is released after embedding in the bonding layer, resulting in excessive free water in the material, which reduces the bonding strength and the frost resistance. If the water content of the ceramsite is too low, the dry ceramsite has strong water absorption capacity and poor water release capacity, the internal curing effect is not achieved, and the dry ceramsite has a rough surface and a small embedding depth of the bonding layer, which also reduces the performance after repair.

[0055] The protective layer containing polypropylene plastic steel fibers is arranged on the surface of the ceramsite layer, the toughness of the protective layer is improved, and the deformation and cracking caused by thermal expansion and cold contraction of different materials are avoided.

[0056] After the repair by the method, further freeze-thaw damage of the old structure is prevented, and the service life is prolonged.

[0057] In some embodiments of the present application, between step (1) and step (2), the following step is further included: driving a steel nail into the chiseled finished surface to enhance the adhesion, and the exposed length of the steel nail is 20-60mm, for example, 20mm, 30mm, 40mm, 50mm, 60mm, or a range composed of any two point values.

[0058] In some embodiments of the present application, in step (2), the mixing method of the bonding layer material is as follows: first, dissolving nano-SiO2 and nano-Fe2O3 in the water reducing agent to prepare a mixed solution for standby, then adding the remaining powders into a stirrer to stir uniformly, and then adding water and the mixed solution into the stirrer to stir and mix uniformly to obtain a thick slurry.

[0059] Pre-dissolving nano-SiO2 and nano-Fe2O3 in the water reducing agent to prepare a mixed solution, and then adding the mixed solution into the uniformly mixed powders, can make the nano-SiO2 and nano-Fe2O3 well dispersed and better play a role. If the nano-SiO2 and nano-Fe2O3 are not pre-mixed and directly added into the stirrer, the nano materials cannot be uniformly dispersed under the stirring action of the stirrer, a "clumping" phenomenon occurs, the role of the nano materials cannot be played, and the nano materials, if not dispersed, will form defects by agglomeration in the concrete, which also leads to a decrease in the frost resistance.

[0060] In some embodiments of the present application, the stirrer includes a planetary stirrer.

[0061] In some embodiments of the present application, the stirring speed during the mixing process of the binding layer material is 60-80 r / min, for example, any one value or a range between any two values selected from 60 r / min, 65 r / min, 70 r / min, 75 r / min, and 80 r / min; the stirring time of the powder is 1-4 min, for example, any one value or a range between any two values selected from 1 min, 2 min, 3 min, and 4 min; and the stirring and mixing time after adding water and the mixed solution is 8-15 min, for example, any one value or a range between any two values selected from 8 min, 10 min, 12 min, 14 min, and 15 min.

[0062] In some embodiments of the present application, in step (3), the pre-wetting method of the ceramsite is as shown in Figure 2 The ceramsite is placed in a container, and the container is opened at the top. The ceramsite is pre-wetted by spraying water into the container. The pre-wetting temperature is 20±2℃, for example, any one value or a range between any two values selected from 18℃, 19℃, 20℃, 21℃, and 22℃.

[0063] In some embodiments of the present application, in step (4), the mixing method of the protective layer material is as follows: the cement, silica fume, metakaolin, and quartz sand in the protective layer material are first added to a stirrer and stirred uniformly, then water and a water reducing agent are added, and stirring is performed until a thick paste is obtained, and finally polypropylene plastic steel fibers are added, and stirring is performed until the fibers are uniformly dispersed.

[0064] In some embodiments of the present application, the stirrer includes a planetary stirrer.

[0065] In some embodiments of the present application, during the mixing process of the protective layer material, the stirring speed is 60-80 rpm, for example, any one value or a range between any two values selected from 60 r / min, 65 r / min, 70 r / min, 75 r / min, and 80 r / min; the stirring time of the powder is 1-4 min, for example, any one value or a range between any two values selected from 1 min, 2 min, 3 min, and 4 min; the stirring time after pouring water and the water reducing agent is 8-15 min, for example, any one value or a range between any two values selected from 8 min, 10 min, 12 min, 14 min, and 15 min; and the stirring time after adding the polypropylene plastic steel fibers is 3-6 min, for example, any one value or a range between any two values selected from 3 min, 4 min, 5 min, and 6 min.

[0066] In some embodiments of the present application, a curing step is further included after step (4), the curing is steam curing, the curing temperature is 90±2℃, for example, any one value or a range consisting of any two values selected from 88℃, 89℃, 90℃, 91℃, 92℃, and the curing time is 36-60h, for example, any one value or a range consisting of any two values selected from 36h, 42h, 48h, 54h, 60h.

[0067] Some embodiments of the present application are described in detail below with reference to specific examples. The raw materials used in the examples and comparative examples, unless otherwise specified, can be commercially purchased.

[0068] The cement used in the examples and comparative examples of the present application is ordinary Portland cement; the silica fume has a silicon content of more than 95% (mass fraction); the activity of the metakaolin is S105 grade; the particle size of the ceramsite is 10mm, the saturated water absorption is 5%, and the apparent density is 1100kg / m 3 ; the cylinder compressive strength is 10MPa; the particle size of the quartz sand is 60-80μm; the average particle size of the nano-SiO2 and Fe2O3 is 20nm, wherein the nano-SiO2 is white powder, the specific surface area is 220m 2 / g, and the density is 2.4g / cm 3 ; the spherical crystal phase; the nano-Fe2O3 is red powder, the specific surface area is 110m 2 / g, and the density is 5.2g / cm 3 ; the ɑ crystal phase; the length of the polypropylene plastic steel fiber is 6mm, the tensile strength is 550MPa, and the water reducing agent is a polycarboxylic acid water reducing agent, and the water reducing rate is 30%.

[0069] Example 1

[0070] The present embodiment provides a cement-based repair material and a repair method for repairing a freeze-thaw damaged concrete member, the grade of the ordinary Portland cement used is P·O52.5, and the steps are as follows:

[0071] (1) Damaged part treatment: use a chisel to chisel all the damaged parts, clean up loose stones and loose cement stones, and expose the stones of the undamaged layer. Steel nails are driven into the chiseled surface to enhance the adhesion, and the steel nails are exposed by 20-30mm.

[0072] (2) Setting the binding layer: take cement 680 parts, silica fume 180 parts, metakaolin 50 parts, quartz sand 700 parts, nano-SiO2 5 parts, nano-Fe2O3 5 parts, water reducing agent 12 parts, pre-dissolve nano-SiO2 and nano-Fe2O3 in water reducing agent to make a mixed solution for standby, then put cement, silica fume, metakaolin and quartz sand into a planetary mixer, stir at 70 r / min for 2 min, then add water and the mixed solution, continue to stir for 10 min to get a viscous slurry, the water-binder ratio is 0.22, use a concrete spraying machine to spray the binding layer slurry to the treated damaged part, the thickness is 20-50 mm.

[0073] (3) Set the ceramsite layer, take ceramsite 200 parts, put it in a heat preservation container, spray pre-wetting at 20℃ to make the water absorption rate of ceramsite 2%, use a sand blasting machine to spray the pre-wetted ceramsite to the binding layer after initial setting and before final setting of the binding layer, so that the ceramsite is embedded in the surface of the binding layer.

[0074] (4) Set the protective layer: take cement 650 parts, silica fume 140 parts, metakaolin 80 parts, quartz sand 1000 parts, polypropylene plastic steel fiber 20 parts, water reducing agent 10 parts, first put cement, silica fume, metakaolin and quartz sand into a planetary mixer, stir at 70 r / min for 2 min, then add water and water reducing agent, stir for 10 min to viscous, finally add polypropylene plastic steel fiber, stir for 5 min to make the fiber evenly distributed to get the protective layer slurry, the water-binder ratio is 0.21, layer by layer apply the protective layer slurry on the surface of the ceramsite layer, the thickness is 40 mm.

[0075] (5) After the construction of the protective layer, install a steam curing shed for steam heat curing, the curing temperature is 90℃, the curing time is 48 h.

[0076] Example 2

[0077] The difference between Example 2 and Example 1 is only in the amount of each raw material in the binding layer material and the protective layer material, and the rest of the conditions are the same as those in Example 1.

[0078] The component content of the binding layer and the protective layer in Example 2 is as follows:

[0079] Binding layer material: cement 710 parts, silica fume 180 parts, metakaolin 80 parts, quartz sand 650 parts, nano-SiO2 8 parts, nano-Fe2O3 8 parts, water reducing agent 13 parts, the water-binder ratio is 0.20;

[0080] Protective layer material: cement 680 parts, silica fume 160 parts, metakaolin 100 parts, quartz sand 900 parts, polypropylene plastic steel fiber 25 parts, water reducing agent 15 parts, the water-binder ratio is 0.19.

[0081] Example 3

[0082] The difference between Example 3 and Example 1 is only that:

[0083] The binding layer material includes cement 750 parts, silica fume 200 parts, metakaolin 70 parts, quartz sand 600 parts, nano-SiO2 10 parts, nano-Fe2O3 10 parts, water reducing agent 15 parts, and the water-binder ratio is 0.21; the stirring speed is 60 r / min, the powder stirring time is 4 min, and the stirring time after adding water and the mixed solution is 15 min;

[0084] The ceramsite layer material includes ceramsite 300 parts, and the water absorption rate after pre-wetting is 3%;

[0085] The protective layer material includes cement 700 parts, silica fume 150 parts, metakaolin 90 parts, quartz sand 950 parts, polypropylene plastic steel fiber 15 parts, water reducing agent 13 parts, and the water-binder ratio is 0.2; the stirring speed is 60 r / min, the powder stirring time is 4 min, the stirring time after adding water and the water reducing agent is 15 min, and the stirring time after adding the polypropylene plastic steel fiber is 6 min; the protective layer is applied to a thickness of 50 mm.

[0086] Example 4

[0087] The difference between Example 4 and Example 1 is that:

[0088] The cement in the binding layer material is 720 parts, the silica fume is 190 parts, the metakaolin is 60 parts, the quartz sand is 650 parts, the nano-SiO2 is 5 parts, the nano-Fe2O3 is 5 parts, the water reducing agent is 10 parts, and the water-binder ratio is 0.23; the stirring speed is 80 r / min, the powder stirring time is 1 min, and the stirring time after adding water and the mixed solution is 8 min;

[0089] The ceramsite layer material includes ceramsite 250 parts, and the water absorption rate after pre-wetting is 1%;

[0090] The protective layer material stirring speed is 80 r / min, the powder stirring time is 1 min, the stirring time after adding water and the water reducing agent is 8 min, and the stirring time after adding the polypropylene plastic steel fiber is 3 min; the protective layer is applied to a thickness of 35 mm.

[0091] Example 5

[0092] The difference between Example 5 and Example 1 is that the ordinary Portland cement used is P·O42.5, and the other conditions are the same as in Example 1.

[0093] Comparative Example 1

[0094] The difference between Comparative Example 1 and Example 1 is only that no nano-SiO2 and nano-Fe2O3 are added in the binding layer material, and the other conditions are the same as in Example 1.

[0095] Comparative Example 2

[0096] Comparative Example 2 differs from Example 1 only in that the ceramic granules are replaced by stones, and the rest of the conditions are the same as in Example 1.

[0097] Comparative Example 3

[0098] Comparative Example 3 differs from Example 1 only in that the polypropylene plastic steel fiber is not added in the protective layer material, and the rest of the conditions are the same as in Example 1.

[0099] Comparative Example 4

[0100] Comparative Example 4 differs from Example 1 only in that the nano-SiO2 and nano-Fe2O3 are not mixed with the water reducing agent, but are directly put into the blender for stirring and mixing, and the rest of the conditions are the same as in Example 1.

[0101] Comparative Example 5

[0102] Comparative Example 5 differs from Example 2 only in that the ceramic granules are added into the blender together with the binding layer powder, and after stirring and mixing, they are directly sprayed onto the repaired surface, and the rest of the conditions are the same as in Example 2.

[0103] Comparative Example 6

[0104] Comparative Example 6 differs from Example 2 only in that the ceramic granules are treated by soaking in water for 2h instead of the pre-wetting treatment in Example 2, and the rest of the conditions are the same as in Example 2.

[0105] Comparative Example 7

[0106] Comparative Example 7 differs from Example 2 only in that the ceramic granules are not pre-wetted, and the rest of the conditions are the same as in Example 2.

[0107] The experimental results after repair of Examples 1-5 and Comparative Examples 1-7 are shown in Table 1.

[0108] Table 1 Experimental results after repair

[0109]

[0110] From the data in Table 1, it can be seen that if the material processing process or the technical category and index of the raw materials used do not meet the requirements of the present application, the bonding strength and frost resistance of the repaired material, and the tensile properties of the protective layer are obviously affected.

[0111] Without adding the nanomaterial, the bonding strength is reduced; replacing the ceramsite with the stone causes the bonding strength and the frost resistance to be reduced; without adding the polypropylene plastic steel fiber to the protective layer material, the tensile strength is greatly reduced; without mixing the nanomaterial with the additive in advance, the nanomaterial cannot be dispersed under the stirring action of the stirrer, the nanomaterial only produces the "clumping" phenomenon, the effect of the nanomaterial cannot be exerted, the bonding strength is reduced, in addition, the nanomaterial is aggregated in the concrete to form a defect, causing the frost resistance to be reduced; if the ceramsite is directly stirred with the binding layer material and used together, because the density of the ceramsite is small, the ceramsite and the mixture cannot be uniformly sprayed in the spraying process, the ceramsite is unevenly distributed in the binding layer, and the overall performance of the binding layer is reduced; if the pretreatment mode of the ceramsite is changed, such as being soaked in water for 2h, the water content is too high, the ceramsite is embedded in the binding layer, the water is released, the free water in the material is too much, the bonding strength and the frost resistance are reduced, and the dry ceramsite does not have the pre-wetting treatment, has strong water absorption capacity and poor water release capacity, cannot play the internal curing effect, and the surface of the dry ceramsite is rough, the embedding depth of the binding layer is small, and the performance of the repaired material is also reduced.

[0112] The repairing material and the repairing method can enhance the bonding strength of the new and old interfaces and improve the frost resistance, and have large tensile strength.

[0113] Although the present application has been illustrated and described with reference to specific embodiments, it is realized that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto; it should be understood by those skilled in the art that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced equivalently without departing from the spirit and scope of the present application; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application; therefore, it means that all the replacements and modifications within the scope of the present application are included in the appended claims.

Claims

1. A method for repairing freeze-thaw damaged concrete, characterized in that, Includes the following steps: (1) Treatment of damaged parts: Chisel away all damaged parts, clean up loose stones and loose cement stones, and expose the stones in the undamaged layer; (2) Setting a bonding layer: Mix the bonding layer materials to form a slurry, and spray the slurry onto the surface of the treated damaged concrete component with a thickness of 20-50 mm; (3) Setting up a ceramic aggregate layer: Place the ceramic aggregate in a container and pre-wet the ceramic aggregate by spraying it into the container to make the moisture content of the ceramic aggregate 1-3%. Before the final setting of the bonding layer, spray the pre-wetted ceramic aggregate onto the bonding layer so that the ceramic aggregate is embedded in the bonding layer. (4) Set up a protective layer: Mix the protective layer material into a slurry and apply it in layers to the surface of the ceramsite layer, with a thickness of 35-50mm; By weight, the bonding layer material comprises 680-750 parts cement, 180-200 parts silica fume, 50-80 parts metakaolin, 600-700 parts quartz sand, 5-10 parts nano-SiO2, 5-10 parts nano-Fe2O3, 10-15 parts water-reducing agent, and the balance water, with a water-cement ratio of 0.20-0.23; the ceramsite layer material comprises 200-300 parts ceramsite, the ceramsite having a particle size of 5-15 mm, a saturated water absorption rate of 5-6%, and an apparent density of 1000-1200 kg / m³. 3 The compressive strength of the cylinder is above 8MPa; the protective layer material includes 650-700 parts of cement, 140-160 parts of silica fume, 80-100 parts of metakaolin, 900-1000 parts of quartz sand, 15-25 parts of polypropylene plastic steel fiber, 10-15 parts of water-reducing agent and the balance of water, with a water-cement ratio of 0.19-0.

21.

2. The method for repairing freeze-thaw damaged concrete according to claim 1, characterized in that, The cement includes ordinary Portland cement with a strength grade of P·O42.5 or P·O52.

5.

3. The method for repairing freeze-thaw damaged concrete according to claim 1, characterized in that, The silica ash has a silicon content of over 95%.

4. The method for repairing freeze-thaw damaged concrete according to claim 1, characterized in that, The activity of the metakaolin is S105 or higher.

5. The method for repairing freeze-thaw damaged concrete according to claim 1, characterized in that, The particle size of the quartz sand is within 150~50μm.

6. The method for repairing freeze-thaw damaged concrete according to claim 1, characterized in that, The nano-SiO2 has an average particle size of 10-30 nm, is a white powder, and has a specific surface area of ​​200-240 m². 2 / g, density between 2.2-2.6g / cm³ 3 , spherical crystal phase.

7. The method for repairing freeze-thaw damaged concrete according to claim 1, characterized in that, The nano-Fe2O3 has an average particle size of 10-30 nm, is a red powder, and has a specific surface area of ​​100-120 m². 2 / g, density between 5.1-5.3g / cm³ 3 , ɑ crystal phase.

8. The method for repairing freeze-thaw damaged concrete according to claim 1, characterized in that, The polypropylene plastic steel fiber has a length of 5-8mm and a tensile strength greater than 500MPa.

9. The method for repairing freeze-thaw damaged concrete according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent with a water reduction rate of ≥30%.

10. The method for repairing freeze-thaw damaged concrete according to claim 1, characterized in that, Between steps (1) and (2), the following steps are also included: driving steel nails into the chiseled surface, wherein the exposed length of the steel nails is 20-60mm.

11. The method for repairing freeze-thaw damaged concrete according to claim 1, characterized in that, In step (2), the mixing method of the bonding layer material is as follows: first, the nano SiO2 and nano Fe2O3 in the bonding layer material are dissolved in the water-reducing agent to prepare a mixed liquid for later use. Then, the remaining powder is added to the mixer and stirred evenly. Then, water and the mixed liquid are added to the mixer and stirred evenly to obtain a viscous slurry.

12. The method for repairing freeze-thaw damaged concrete according to claim 11, characterized in that, The stirring speed during the mixing process of the bonding layer material is 60-80 r / min, the stirring time of the powder is 1-4 min, and the stirring and mixing time after adding the water and the mixture is 8-15 min.

13. The method for repairing freeze-thaw damaged concrete according to claim 1, characterized in that, In step (3), the pre-wetting temperature of the ceramsite is 20±2℃.

14. The method for repairing freeze-thaw damaged concrete according to claim 1, characterized in that, In step (4), the mixing method of the protective layer material is as follows: first, add the cement, silica fume, metakaolin and quartz sand in the protective layer material into the mixer and mix evenly, then add water and water-reducing agent and mix until viscous, and finally add polypropylene plastic steel fiber and mix until the fiber is evenly dispersed.

15. The method for repairing freeze-thaw damaged concrete according to claim 14, characterized in that, During the mixing process of the protective layer material, the stirring speed is 60-80 rpm, the stirring time of the powder is 1-4 min, the stirring time after adding the water and the water-reducing agent is 8-15 min, and the stirring time after adding the polypropylene plastic steel fiber is 3-6 min.

16. The method for repairing freeze-thaw damaged concrete according to claim 1, characterized in that, The step (4) is followed by a curing step, which is steam curing, with a curing temperature of 90±2℃ and a curing time of 36-60h.

Images