CN114685140B - Ecological protection layer for improving concrete durability, preparation method and application thereof - Google Patents
Ecological protection layer for improving concrete durability, preparation method and application thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/30—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing magnesium cements or similar cements
- C04B28/32—Magnesium oxychloride cements, e.g. Sorel cement
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B18/04—Waste materials; Refuse
- C04B18/06—Combustion residues, e.g. purification products of smoke, fumes or exhaust gases
- C04B18/10—Burned or pyrolised refuse
- C04B18/101—Burned rice husks or other burned vegetable material
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B22/00—Use of inorganic materials as active ingredients for mortars, concrete or artificial stone, e.g. accelerators, shrinkage compensating agents
- C04B22/08—Acids or salts thereof
- C04B22/16—Acids or salts thereof containing phosphorus in the anion, e.g. phosphates
- C04B22/165—Acids
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
- C04B41/50—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials
- C04B41/5076—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials with masses bonded by inorganic cements
- C04B41/509—Magnesium cements, e.g. Sorel cement
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/60—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only artificial stone
- C04B41/61—Coating or impregnation
- C04B41/65—Coating or impregnation with inorganic materials
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- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00017—Aspects relating to the protection of the environment
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00034—Physico-chemical characteristics of the mixtures
- C04B2111/00146—Sprayable or pumpable mixtures
- C04B2111/00155—Sprayable, i.e. concrete-like, materials able to be shaped by spraying instead of by casting, e.g. gunite
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- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
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Abstract
The invention discloses an ecological protective layer for improving the durability of concrete, a preparation method and application thereof, and relates to the technical field of anticorrosive materials. The raw materials comprise the following components in parts by weight: 500-600 parts of magnesium oxide, 200-300 parts of magnesium chloride, 900-1000 parts of fine aggregate, 200-260 parts of water, 10-20 parts of water reducing agent, 3-8 parts of water-resistant agent and 25-150 parts of admixture. According to the invention, the highland barley straw ash is added on the basis that the water-resistant agent is added into the magnesium oxychloride cement mortar to serve as phosphoric acid, so that the mechanical and water-resistant properties of the magnesium oxychloride cement mortar are further improved, the problem that the water-resistant property of the magnesium oxychloride cement mortar is insufficient in a water-soaked environment is effectively solved, the interface bonding property of the magnesium oxychloride cement mortar and common concrete is improved, and the reliability of the cooperative work of the magnesium oxychloride cement mortar and the common concrete in salt lakes and saline land areas is ensured.
Description
Technical Field
The invention relates to the technical field of anticorrosive materials, in particular to an ecological protective layer for improving the durability of concrete, a preparation method and application thereof.
Background
Salt lake and saline soil area contain a large amount of corrosive salt, the chloride ion concentration in some areas is as high as 300g/L, the service life of common concrete under the condition is less than 10 years, and some structures are seriously damaged for 2-3 years. At present, high-performance concrete and an external protection technology are mainly adopted for improving the durability of concrete in salt lakes and salinized soil areas. However, high performance concrete requires good curing conditions, and it is difficult to achieve the desired performance in a severe salt lake environment. Secondly, the application of the high-performance concrete greatly increases the construction cost, and causes additional expenditure of resources such as manpower and financial resources. The external protection technology mainly adopts functional coating or organic materials such as glass fiber reinforced plastics and the like for protection. However, the protective effect of the paint is not obvious, and the paint gradually cracks, falls off and the like in a severe salt lake environment as the exposure time increases, and frequent repeated painting is required. By adopting the protection technologies such as glass fiber reinforced plastics and the like, the construction difficulty is greatly increased, the construction cost is improved, and the engineering construction period is prolonged. At present, the technology for improving the durability of concrete in the severe weather environment of salt lakes and saline soil areas has obvious defects, breakthrough achievements are not obtained all the time, and no widely accepted or accepted technical means exist.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and provides an ecological protective layer for improving the durability of concrete, a preparation method and application thereof. The protective layer further improves the mechanical and water-resistant performances of the magnesium oxychloride cement mortar by adding the highland barley straw ash on the basis that the water-resistant agent is added into the magnesium oxychloride cement mortar to be phosphoric acid, effectively solves the problem that the water-resistant performance of the magnesium oxychloride cement mortar is insufficient in a water-soaked environment, improves the interface bonding performance with common concrete, and ensures the reliability of the cooperative work of the magnesium oxychloride cement mortar and the common concrete in salt lakes and saline land areas.
The invention aims to provide an ecological protective layer for improving the durability of concrete, which comprises the following raw materials in parts by weight: 500-600 parts of magnesium oxide, 200-300 parts of magnesium chloride, 900-1000 parts of fine aggregate, 200-260 parts of water, 10-20 parts of water reducing agent, 3-8 parts of water-resistant agent and 25-150 parts of admixture; wherein the admixture is Highland Barley Straw Ash (HBSA).
Preferably, the raw materials comprise the following components in parts by weight: 583.44 parts of magnesium oxide, 221.72 parts of magnesium chloride, 937.5 parts of fine aggregate, 220.04 parts of water, 16.02 parts of water reducing agent, 6.87 parts of water resistant agent and 29.17-145.86 parts of admixture.
More preferably, the highland barley straw ash is prepared according to the following steps:
naturally burning the highland barley straws into ash powder, calcining the burned ash powder at 600 ℃ for 2 hours, and then mechanically grinding the calcined ash powder for 2-4 hours to obtain the highland barley straw ash.
More preferably, the particle size of the highland barley straw ash is 6-10 mu m, and the specific surface area is 2050-2100 kg/m 2 。
Preferably, the fine aggregate is river sand with fineness modulus of 2.5-2.7; the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent; the water-resistant agent is phosphoric acid.
The second purpose of the invention is to provide a preparation method of an ecological protection layer for improving the durability of concrete, which comprises the following steps:
mixing and stirring the raw materials to form mortar, then smearing or spraying the obtained mortar on the surface of concrete, and naturally curing, namely obtaining the ecological protection layer on the surface of the concrete.
Preferably, when the smearing mode is adopted, smearing is carried out according to the bottom layer, the middle layer and the surface layer in sequence, the smearing thickness of each layer is 5-7mm, and the total smearing thickness is 15-20 mm.
Preferably, in the case of spraying, the mixed mortar is sprayed onto the surface of the concrete at one time, and the thickness of the mortar is 15 to 20mm.
Preferably, the concrete surface is further coated with an interface agent before being coated or sprayed with mortar.
The third purpose of the invention is to provide the application of the ecological protection layer in improving the durability of concrete.
Compared with the prior art, the invention has the beneficial effects that:
the ecological protective layer for improving the durability of the concrete is prepared by adding highland barley straw ash into magnesium oxychloride cement mortar to improve the mechanical and water-resistant properties of the magnesium oxychloride cement on the basis of adding a water-resistant agent which is phosphoric acid into the magnesium oxychloride cement mortar; the active admixture of the highland barley straw ash is compounded with the phosphoric acid for use, so that the water resistance of the magnesium oxychloride cement mortar can be improved to 87.68 percent, the problem of insufficient water resistance of the magnesium oxychloride cement mortar in a water immersion environment is effectively solved, and the long-term cooperative work of the magnesium oxychloride cement mortar and the common concrete is ensured. The magnesium oxychloride cement can have higher strength under natural conditions without being cured under standard conditions, which cannot be possessed by other functional cement mortars, coatings and the like, and ensures the suitability of the cooperative work of the magnesium oxychloride cement mortar and the common concrete.
The magnesium oxychloride cement adopted by the invention has higher salt and brine corrosion resistance, and can effectively resist the corrosion of the common concrete in salt lake and saline soil environment as an outer protective layer of the common concrete, so that the durability of the common concrete is improved by 30%, and the effectiveness of cooperative work of the protective layer and the common concrete is ensured;
the magnesium oxychloride cement mortar adopted by the invention has better bonding performance, can be well bonded with the interface of common concrete, has the bonding strength of the 14d interface of the magnesium oxychloride cement mortar and the common concrete up to 1.46Mpa, and ensures the reliability of the cooperative work of the protective layer and the common concrete.
Drawings
FIG. 1 is a process flow for the preparation of HBSA;
FIG. 2 is an XRD pattern of HBSA;
FIG. 3 is a bar graph of the bonding strength of the ecological protective layer provided in example 1 with common concrete in different thicknesses;
FIG. 4 is a bar graph of the compressive strength of the ecological protective layer provided in examples 1 to 5 and comparative example 1 in a dry and water-saturated state;
FIG. 5 is a graph of the softening coefficient of the ecological protective layer provided in examples 1 to 5 and comparative example 1;
fig. 6 is an SEM image of the ecological protection layer provided in example 1 and comparative example 1, wherein fig. 6a is an SEM image of the ecological protection layer provided in example 1, and fig. 6b is an SEM image of the ecological protection layer provided in comparative example 1;
FIG. 7 is a bar graph of the compressive strength of concrete protected by the ecological protective layer provided in example 1 and the concrete protected by the protective layer provided in comparative example 1;
FIG. 8 is a histogram of ultrasonic velocities of concrete protected by an ecological protective layer provided in example 1 and concrete protected by a protective layer provided in comparative example 1;
FIG. 9 is a bar graph of compressive strength of concrete and general concrete protected by the ecological protection layer provided in example 1;
FIG. 10 is a histogram of ultrasonic velocities of concrete and normal concrete protected by an ecological shield as provided in example 1;
fig. 11 is a bar graph of the corrosion current density of steel reinforcement in the reinforced concrete and the ordinary reinforced concrete protected by the ecological protection layer provided in example 1.
Detailed Description
In order to make the technical solutions of the present invention better understood and enable those skilled in the art to practice the present invention, the following embodiments are further described, but the present invention is not limited to the following embodiments.
The invention is applicable to ordinary concrete structures below C50 in salt lakes and salinized soil areas, C40 concrete is adopted in the basic test of the following examples, and the design of the mixing ratio is shown in Table 1.
TABLE 1C40 design of mix proportion of concrete (kg/m) 3 )
| Cement | Sand | Stone (stone) | Water (I) | Water reducing agent |
| 432 | 558 | 1242 | 168 | 6.48 |
The admixture adopted in the following examples is Highland Barley Straw Ash (HBSA), and HBSA is an autonomously prepared active admixture suitable for magnesium oxychloride cement mortar. The preparation method comprises the following steps: naturally burning the highland barley straws outdoors until the ash powder is completely cooled, and carrying out secondary calcination on the burned ash powder in a muffle furnace, wherein the calcination temperature is 600 ℃, and the calcination time is 2 hours. After calcination, the completely cooled ash powder is sieved in an automatic sieve shaker with the sieve pore size of 0.6mm to remove solid impurities such as soil, sandstone and the like. The sieved soot was subsequently ground in a roller mill for 2h. The ash powder obtained after grinding is HBSA doped in the magnesium oxychloride cement mortar, and the process flow of the HBSA is shown in figure 1.
The main components of the prepared HBSA are shown in Table 2, and the XRD test results are shown in FIG. 2. Among them, siO in HBSA 2 In an amount of 61.75%, SO 3 The content of (D) is 1.75%, and the Loss On Ignition (LOI) is 4.55%. SO 3 The content of the additive meets the standard that the national standard GB/T2847-2005 'volcanic ash mixed material used in cement' requires no more than 3.5%, and the ignition loss meets the standard requirement of no more than 10%. By testing the XRD pattern of HBSA and calculating the crystallinity of HBSA, the active SiO in HBSA can be obtained 2 Is 48.45%, thereby allowing the HBSA to have a high activity effect. Further, HBSA after 2 hours of milling had an average particle diameter of 8.6. Mu.m, and a specific surface area of 2088kg/m 2 The smaller particle size and larger specific surface area promote the active effect of the HBSA.
TABLE 2 chemical composition of HBSA (%)
The magnesium oxide adopted in the following examples is light-burned magnesium oxide, and the magnesium chloride is industrial magnesium chloride; the fine aggregate is river sand with fineness modulus of 2.6 and particle size of less than 4.75 mm; the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent with water reducing efficiency of 21 percent, and the water-resistant agent is phosphoric acid.
Example 1
An ecological protective layer for improving the durability of concrete comprises the following raw materials: 583.44kg/m magnesium oxide 3 221.72kg/m magnesium chloride 3 Fine aggregate 937.5kg/m 3 220.04kg/m of water 3 16.02kg/m of water reducing agent 3 6.87kg/m of water-resistant agent 3 58.34kg/m of admixture 3 . Wherein the dosage of the admixture is 10 percent of the dosage of the magnesium oxide.
The preparation method of the ecological protection layer for improving the durability of the concrete comprises the following steps:
the raw materials are mixed on site according to the proportion and the requirements, the mixed mortar is used up within 2 hours, and is mixed again after 2 hours, and before an ecological protection layer is applied to the outer surface of the concrete, the surface of the concrete is simply cleaned, impurities such as soil on the surface are washed away, and roughening treatment is not needed; then coating an interface agent on the surface of the concrete, wherein the interface agent can adopt YJ-302 concrete interface treating agent used for new and old concrete construction, and is organic polymer emulsion; the coating of the interface agent is completed in two times, the interface agent is uniformly coated on the outer surface of the concrete for the first time, and the second coating is performed after the interface agent is basically solidified; after the interface agent is coated for the second time, an ecological protective layer needs to be applied before solidification, and natural maintenance is carried out to obtain the ecological protective layer on the surface of the concrete;
the ecological protective layer is manually coated, namely construction can be carried out according to a construction method of plastering mortar, plastering is carried out in three layers, namely a bottom layer, a middle layer and a surface layer, the plastering thickness of each layer is 5-7mm, and the total plastering thickness is 18mm; the bonding strength between the ecological protective layer and the common concrete can reach 1.46Mpa in 14 days and 1.56Mpa in 28 days, and the requirement of the interface bonding strength of plastering mortar is completely met.
Example 2
The same as in example 1, except that,
the raw materials comprise the following components: 583.44kg/m magnesium oxide 3 221.72kg/m magnesium chloride 3 Fine aggregate 937.5kg/m 3 220.04kg/m of water 3 16.02kg/m of water reducing agent 3 6.87kg/m of water-resistant agent 3 29.17kg/m admixture 3 。
Wherein the dosage of the admixture is 5 percent of the dosage of the magnesium oxide.
Example 3
The same as in example 1, except that,
the raw materials comprise the following components: 583.44kg/m magnesium oxide 3 221.72kg/m magnesium chloride 3 Fine aggregate 937.5kg/m 3 220.04kg/m of water 3 16.02kg/m of water reducing agent 3 6.87kg/m of water proofing agent 3 87.52kg/m of admixture 3 。
Wherein the dosage of the admixture is 15 percent of the dosage of the magnesium oxide.
Example 4
The same as in example 1, except that,
the raw materials comprise the following components: 583.44kg/m magnesium oxide 3 221.72kg/m magnesium chloride 3 Fine aggregate 937.5kg/m 3 220.04kg/m of water 3 16.02kg/m of water reducing agent 3 6.87kg/m of water-resistant agent 3 116.69kg/m admixture 3 。
Wherein the dosage of the admixture is 20 percent of the dosage of the magnesium oxide.
Example 5
The same as in example 1, except that,
the raw materials comprise the following components: 583.44kg/m magnesium oxide 3 221.72kg/m magnesium chloride 3 Fine aggregate 937.5kg/m 3 220.04kg/m of water 3 16.02kg/m of water reducing agent 3 6.87kg/m of water proofing agent 3 145.86kg/m of admixture 3 。
Wherein the dosage of the admixture is 25 percent of the dosage of the magnesium oxide.
Example 6
The same as example 1, except that the ecological protection layer is constructed by spraying during the preparation of the ecological protection layer for improving the durability of concrete, the mixed mortar can be constructed by spraying at one time, and the optimal ecological protection thickness is about 18mm through the test of the early stage.
Example 7
The same as in example 1, except that,
the raw materials comprise the following components: magnesium oxide 500kg/m 3 Magnesium chloride 200kg/m 3 900kg/m of fine aggregate 3 200kg/m of water 3 10kg/m of water reducing agent 3 3kg/m of water-resistant agent 3 25kg/m of admixture 3 。
Example 8
The same as in example 1, except that,
the raw materials comprise the followingThe components are as follows: magnesium oxide 600kg/m 3 300kg/m of magnesium chloride 3 1000kg/m of fine aggregate 3 260kg/m of water 3 20kg/m of water reducing agent 3 8kg/m of water-resistant agent 3 150kg/m of admixture 3 。
Comparative example 1
The same as example 1, except that no admixture was added to the raw materials.
In order to illustrate the relevant performance of the ecological protection layer provided by the present invention, examples 1 to 5 and comparative example 1 were tested.
In order to illustrate the bonding strength between the ecological protection layer and the ordinary concrete, the ecological protection layer provided by example 1 is constructed on the surface of the ordinary concrete according to the thicknesses of 6mm, 12mm, 18mm and 24mm, and the bonding strength is tested for 7d, 14d and 28d respectively, as shown in fig. 3, the bonding strength between the ecological protection layer with different thicknesses and the ordinary concrete is shown in a bar chart; as can be seen from FIG. 3, the ecological protection layer with the thickness of 18mm is adhered to the surface of the common concrete, the 14d of the ecological protection layer can reach 1.46MPa, the 28d of the ecological protection layer can reach 1.56MPa, and the requirement of the interface bonding strength of the plastering mortar is completely met.
(1) The mechanical and water-resistant properties of the protective layer can be obviously improved by doping HBSA.
The compressive strength of magnesium oxychloride cement mortar with different HBSA doping amounts in a dry and water-saturated state is tested, as shown in figure 4;
FIG. 4 is a bar graph of compressive strength of the ecological protection layers provided in examples 1 to 5 and comparative example 1 in dry and water-saturated states;
from fig. 4, it can be seen that when the amount of the HBSA is 5%, the compressive strength of the ecological protection layer in the dry and water-saturated states reaches the maximum value, and the mechanical property is the highest.
FIG. 5 is a graph showing the softening coefficient of the ecological protective layer provided in examples 1 to 5 and comparative example 1, and the softening coefficient of the ecological protective layer is the greatest when the blending amount of HBSA is 10%, which shows that the compressive strength loss of the ecological protective layer under the water immersion condition is the least under the blending amount. When the mixing amount of the HBSA is 10 percent, the softening coefficient of the ecological protective layer reaches 87.68 percent, which is increased by 6.79 percent compared with the condition without mixing the HBSA. Thus, the incorporation of 10% of HBSA enables a significant improvement in the water resistance and mechanical properties of the ecological protection layer, effectively solving the problem of poor water resistance of the ecological protection layer.
Fig. 6 is an SEM image of the ecological protection layer provided in example 1 and comparative example 1, wherein fig. 6a is an SEM image of the ecological protection layer provided in example 1, and fig. 6b is an SEM image of the ecological protection layer provided in comparative example 1;
as can be seen from FIG. 6, more hydrated magnesium silicate (M-S-H) is generated in the micro-morphology of the ecological protective layer doped with HBSA, so that the pore structure is optimized, the compactness of the structure is enhanced, and the mechanical and water-resistant properties are improved.
(2) The corrosion resistance of the protective layer can be obviously improved by doping HBSA
The concrete protected by the ecological protection layer provided in example 1 and the concrete protected by the protection layer provided in comparative example 1 were subjected to an anti-corrosion test. The concrete sample protected by the ecological protection layer provided by the embodiment 1 is recorded as HBSA-MOCM, and the concrete sample protected by the protection layer provided by the comparative example 1 is recorded as N-MOCM.
Taking the Theaca salt lake brine as a corrosion medium, soaking HBSA-MOCM and N-MOCM test pieces in the salt lake brine for 60 days, and then respectively testing the durability indexes such as strength, ultrasonic speed and the like, wherein the test results are shown in figures 7-8. FIG. 7 is a bar graph of compressive strength of concrete protected by ecological protection layer provided in example 1 and concrete protected by protection layer provided in comparative example 1; FIG. 8 is a histogram of ultrasonic velocities of concrete protected by an ecological protective layer provided in example 1 and concrete protected by a protective layer provided in comparative example 1;
as can be seen from FIGS. 7 to 8, the compressive strength and the ultrasonic velocity of the HBSA-MOCM test piece before and after the erosion were both greater than those of the N-MOCM test piece. After being corroded by salt lake brine, the strength retention rate of the HBSA-MOCM test piece is 77.76%, and the strength retention rate of the N-MOCM test piece is 74.65%. The ultrasonic velocity retention rate of the HBSA-MOCM test piece is 90.54%, and the ultrasonic velocity loss rate of the N-MOCM test piece is 87.24%. The strength of the HBSA-MOCM test piece is increased by 14.01% compared with that of the N-MOCM test piece after the HBSA-MOCM test piece is corroded by salt lake brine, and the ultrasonic velocity is increased by 4.86%.
(3) Compared with common concrete, the concrete protected by the ecological protective layer has obviously improved durability
The concrete (MOCM-OPC) and the ordinary concrete (OPC) test pieces protected by the ecological protection layer provided in example 1 were subjected to a long-term soaking test in salt lake brine, and the compressive strength and ultrasonic velocity of the concrete test pieces before and after 360d salt lake brine erosion were changed as shown in fig. 8.
FIG. 9 is a bar graph of the compressive strength of concrete (MOCM-OPC) protected by ecological protection layer and ordinary concrete (N-OPC) provided in example 1; FIG. 10 is a histogram of ultrasonic velocity of concrete versus ordinary concrete protected by the ecological protective layer provided in example 1;
as can be seen from fig. 9 to 10, the MOCM-OPC test piece has a compressive strength loss rate of 6.01% and an ultrasonic velocity loss rate of 13% lower than those of the N-OPC test piece. After the salt lake brine is corroded, the compression strength of MOCM-OPC is 29.36% higher than that of N-OPC, and the ultrasonic wave speed of the MOCM-OPC is 17.59% higher than that of the N-OPC.
The reinforced concrete (MOCM-OPC) and the ordinary reinforced concrete (N-OPC) test pieces protected by the ecological protection layer provided in the embodiment 1 are subjected to constant-current electrifying accelerated corrosion tests in salt lake brine, and when the theoretical mass loss rate of the steel bars reaches 6%, the corrosion current density test results of the steel bars are obtained after 1236h of accelerated tests, as shown in FIG. 11.
Fig. 11 is a bar graph of the corrosion current density of the steel reinforcement in the reinforced concrete and the ordinary reinforced concrete protected by the ecological protection layer provided in example 1. As can be seen from fig. 9, the corrosion current density of the steel bar in the concrete protected by the ecological protection layer provided in example 1 is reduced by 32.5% compared with that of the general concrete through the accelerated corrosion test. Therefore, the ecological protection layer provided by the embodiment 1 is used as a protection layer of common concrete, so that the durability of the concrete can be effectively improved, and the improvement efficiency is over 30. The service life of the common concrete structure is calculated as 50 years, and the service life of the concrete structure in the salt lake region can be prolonged by at least more than 15 years.
In conclusion, the ecological protection layer for improving the durability of the concrete provided by the invention is formed by adding highland barley straw ash on the basis of magnesium oxychloride cement mortar to improve the corrosion resistance; the highland barley straw ash is an active admixture which is independently developed, can effectively improve the water resistance of magnesium oxychloride cement, can improve the water resistance of magnesium oxychloride cement mortar to 87.68% by being used in combination with phosphoric acid, effectively solves the problem that the water resistance of the magnesium oxychloride cement mortar is not enough in a water-soaking environment, and ensures the long-term performance of the cooperative work of the magnesium oxychloride cement mortar and common concrete. The magnesium oxychloride cement can have higher strength under natural conditions without being cured under standard conditions, which cannot be possessed by other functional cement mortars, coatings and the like, and ensures the suitability of the cooperative work of the magnesium oxychloride cement mortar and the common concrete.
The magnesium oxychloride cement adopted by the invention has higher salt brine corrosion resistance, and can effectively resist the corrosion of the common concrete in salt lake and saline soil environment as an outer protective layer of the common concrete, so that the durability of the common concrete is improved by 30%, and the effectiveness of the protective layer and the common concrete in cooperative work is ensured;
the magnesium oxychloride cement mortar adopted by the invention has better bonding performance, can be well bonded with the interface of common concrete, has the bonding strength of the 14d interface of the magnesium oxychloride cement mortar and the common concrete up to 1.46Mpa, and ensures the reliability of the cooperative work of the protective layer and the common concrete.
The present invention describes preferred embodiments and effects thereof. Additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (4)
1. The application of the ecological protective layer in improving the durability of concrete is characterized in that the raw materials of the ecological protective layer comprise the following components in parts by weight: 583.44 parts of magnesium oxide, 221.72 parts of magnesium chloride, 937.5 parts of fine aggregate, 220.04 parts of water, 16.02 parts of water reducing agent, 6.87 parts of water resisting agent and 58.34 parts of admixture;
wherein the admixture is highland barley straw ash;
the preparation method of the ecological protective layer comprises the following steps: mixing and stirring the raw materials to form mortar, then smearing or spraying the obtained mortar on the surface of concrete, and naturally curing, namely obtaining the ecological protective layer on the surface of the concrete; when the smearing mode is adopted, smearing is carried out according to the bottom layer, the middle layer and the surface layer in sequence, the smearing thickness of each layer is 5-7mm, and the total smearing thickness is less than or equal to 20mm; when the spraying mode is adopted, the mixed mortar is sprayed to the surface of the concrete at one time, and the thickness of the mixed mortar is 15-20 mm; and the surface of the concrete is also coated with an interface agent before being coated or sprayed with mortar.
2. The use of the ecological protective layer according to claim 1 for improving the durability of concrete, wherein the highland barley straw ash is prepared by the following steps:
naturally burning the highland barley straws into ash powder, calcining the burned ash powder at 600 ℃ for 2h, and then mechanically grinding the calcined ash powder for 2-4 h to obtain the highland barley straw ash.
3. The application of the ecological protective layer in improving the durability of concrete according to claim 1, wherein the particle size of the highland barley straw ash is 6-10 μm, and the specific surface area is 2050-2100 kg/m 2 。
4. The use of the ecological protective layer according to claim 1 for improving the durability of concrete, characterized in that the fine aggregate is river sand with a fineness modulus of 2.5-2.7; the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent; the water-resistant agent is phosphoric acid.
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