A kind of salt-resistant and frost-resistant high-durability concrete and its preparation method and application

Abstract

The present invention belongs to the technical field of improving the durability of concrete, and discloses a salt-resistant and frost-resistant high-durable concrete, and a preparation method and application thereof. The present invention uses versatate / vinyl acetate copolymer emulsion and polyvinyl alcohol emulsion to modify basalt flakes to prepare modified basalt flakes, and uses the prepared modified basalt flakes as the main component to prepare salt-resistant and freeze-thaw-resistant concrete. The modified basalt flakes prepared by the present invention can provide a layered "maze" structure for concrete, and at the same time, versatate / vinyl acetate copolymer emulsion and polyvinyl alcohol emulsion are used to modify the surface of basalt flakes, delaying the migration of harmful substances inside the concrete, improving the water resistance and durability of the concrete, and fundamentally hindering the erosion of the concrete by the deicing agent in the freeze-thaw environment, thereby improving the salt resistance and freeze-thaw resistance of the concrete. The operation is simple and has high industrial application value.

Description

Technical Field

[0001] The invention belongs to the field of improving the durability of concrete, and specifically relates to a salt-resistant and frost-resistant high-durability concrete and a preparation method and application thereof. Background Art

[0002] In northern my country, ice easily forms on rainy and snowy days. For the safety of vehicles and pedestrians, deicing agents are needed to remove ice and snow. Magnesium chloride, calcium chloride, sodium chloride, etc., which are commonly used in deicing agents, can quickly melt ice and snow. However, the chloride ions in deicing agents entering concrete will cause the concrete to deteriorate, causing serious damage to concrete structures such as concrete pavements and bridge guardrails, and reducing the service life of concrete. The main reasons are as follows: First, these salts enter the concrete through the capillary water absorption of concrete, and after freeze-thaw cycles, they will crystallize and expand in volume, causing damage to the concrete; second, chloride ions erode into the concrete, causing rust on the steel bars, causing concrete to crack. Under the dual effects of freeze-thaw cycles and chloride salt erosion, the peeling of the concrete surface is accelerated.

[0003] Patent 202110128308.4 discloses a green water-based coating for bridge concrete in a de-icing agent environment and a preparation method. The prepared coating has good resistance to chloride ions and other properties; Patent 201510549319 discloses a permeable cross-linked concrete anti-corrosion coating and a preparation method, which improves the concrete's resistance to chloride ions. Patents 202110128308.4 and 201510549319 are both concrete external protection. In a salt freeze-thaw environment, as the coating ages, the durability will decrease and the long-term protection effect will not be achieved. Patent CN202211003669.7 discloses an environmentally friendly concrete that resists chloride ion penetration. It uses sodium alginate to expand when it encounters water, plugs cracks, and prevents chloride ion penetration. However, since sodium alginate encounters calcium and magnesium ions in an alkaline environment to produce complexation and form irreversible colloids, it still cannot effectively prevent the movement of ions in a salt freeze-thaw environment. Therefore, there is still a need for a technology that can resist salt and frost for a long time to improve the durability of concrete. Summary of the invention

[0004] In view of the problems and shortcomings in the prior art, the object of the present invention is to provide a salt-resistant and frost-resistant high-durability concrete and a preparation method and application thereof.

[0005] Based on the above purpose, the present invention adopts the following technical solution:

[0006] The first aspect of the present invention provides a salt-resistant and frost-resistant high-durability concrete, comprising the following material components by weight: 360-410 parts of cement, 40-60 parts of microspheres, 680-750 parts of fine aggregate, 1100-1150 parts of coarse aggregate, 30-80 parts of modified basalt flakes, 50-150 parts of water, 3-5 parts of water reducer, and 3-5 parts of thickener;

[0007] The modified basalt flakes are mainly prepared by modifying the basalt flakes with versatate / vinyl acetate copolymer emulsion and polyvinyl alcohol emulsion.

[0008] Preferably, the preparation method of the modified basalt flakes is: firstly, polyvinyl alcohol emulsion and basalt flakes are evenly mixed to make the surface of the basalt flakes fully wetted, and then versatate / vinyl acetate copolymer emulsion is added, and after fully stirring, the modified basalt flakes are obtained.

[0009] Preferably, in the raw materials for preparing the modified basalt flakes, the mass ratio of basalt flakes, tert-carbonate / vinyl acetate copolymer emulsion and polyvinyl alcohol emulsion is (1-3): (1-4): (0.5-1). In order to better wet the basalt flakes, more tert-carbonate / vinyl acetate copolymer emulsion is required than its mass fraction, but since the emulsion has a significant hydrophobic effect, it is easy to cause the surface of some basalt flakes to not be fully wetted during the dispersion process. Therefore, hydrophilic polyvinyl alcohol emulsion is selected as a dispersant, first the surface of the basalt flakes is fully wetted by the hydrophilic polymer, and then the hydrophobic tert-carbonate / vinyl acetate copolymer emulsion is evenly dispersed on the surface of the basalt flakes / polyvinyl alcohol.

[0010] Preferably, the basalt flakes have a diameter of 10 μm-3 mm and a thickness of 1-3 μm.

[0011] Preferably, in the versatate / vinyl acetate copolymer emulsion, the mass ratio of versatate to vinyl acetate is (1-2): (1-5), because at this ratio, the ratio of hydrophobic and hydrophilic functional groups in the versatate / vinyl acetate copolymer emulsion can achieve the optimal effect between sufficient wetting and the final hydrophobic effect.

[0012] More preferably, the solid contents of the versatate / vinyl acetate copolymer emulsion and the polyvinyl alcohol emulsion are both 40%-60%.

[0013] More preferably, the micro-beads are solid glass beads in fly ash and hollow glass beads that sink in water; the water reducer is an early-strength polycarboxylate water reducer; the cement is composed of ordinary Portland cement and high-belite sulphoaluminate cement; and the thickener is low-viscosity cellulose ether with a relative molecular mass of 400-10000.

[0014] The second aspect of the present invention provides a method for preparing the salt-resistant and frost-resistant high-durability concrete described in the first aspect, comprising the following steps: mixing cement, water reducer, thickener, microspheres, fine aggregate, and coarse aggregate in a dry state; then adding modified basalt flakes and water in sequence and continuing to stir to obtain high-durability concrete.

[0015] More preferably, the dry state mixing time is 3-5 minutes; the stirring process is specifically: adding modified basalt flakes and stirring for 1-2 minutes, then adding water, and stirring for another 2-4 minutes after adding water.

[0016] The third aspect of the present invention provides the use of the salt-resistant and frost-resistant high-durability concrete described in any one of the first aspects in salt-resistant and frost-resistant materials.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The modified basalt flakes prepared by the present invention using basalt flakes, versatate / vinyl acetate copolymer emulsion and polyvinyl alcohol emulsion are added to the concrete, so that the basalt flakes can be evenly arranged in the concrete, producing a "maze effect". When the corrosive medium enters the concrete, the basalt flakes change the medium transmission path, forcing the transmission path to be circuitous and preventing the medium transmission, which is equivalent to increasing the thickness of the concrete, that is, dividing the concrete into many spaces, separating the pores and microcracks of the concrete, and delaying the transmission of the medium; versatate The vinyl ester / vinyl acetate copolymer emulsion and the polyvinyl alcohol emulsion react with the CSH gel to form a three-dimensional network structure covering the surface of the cement particles; in addition, after the versatate / vinyl acetate copolymer emulsion reacts with the cement through physical adsorption and chemical adsorption, its hydrophobic end extends to the pores. When the hydrophobic layer formed on the surface of the cement concrete contacts the deicing salt solution, a wetting angle greater than 90° is formed at the interface, which prevents chloride ions, calcium and magnesium ions and water from diffusing into the concrete, hinders the movement of medium water, and further hinders the movement of ions. Therefore, in the modified basalt flakes prepared by the present invention, the basalt flakes, versatate / vinyl acetate copolymer emulsion and polyvinyl alcohol emulsion produce a synergistic effect, effectively preventing the transmission of medium water and ions such as chloride ions, calcium and magnesium ions, improving the alkali and salt resistance of the concrete, and also improving the service life of the concrete in a freeze-thaw environment, fundamentally hindering the erosion of the concrete by the deicing agent in a freeze-thaw environment.

[0019] (2) The present invention utilizes the colloidal properties of versatate / vinyl acetate copolymer emulsion and polyvinyl alcohol emulsion to fully disperse basalt flakes. Among them, versatate is a saturated fatty acid vinyl ester with highly branched α-carbon. The high degree of branching has a large steric hindrance effect and hydrophobic effect, which makes it have excellent hydrophobicity and long-term water resistance.

[0020] (3) The composite cement composed of ordinary Portland cement and high-belite sulphoaluminate cement used in the present invention has the characteristics of high viscosity and low water seepage. Among them, the main mineral of high-belite sulphoaluminate cement clinker is dicalcium silicate, and it does not contain tricalcium silicate, so the hydration exotherm is low. After adding ordinary Portland cement, the calcium sulphoaluminate phase provides early strength, and the highly active dicalcium silicate phase ensures the later strength of concrete. The 62.5-grade high-belite sulphoaluminate cement is used as the early strength agent seed of ordinary Portland cement, which greatly improves the early strength and crack resistance of concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The actual picture of the concrete samples prepared in Example 3 and Comparative Example 3 of the present invention after 120 cycles of salt freeze-thaw resistance test; in the figure, a is the concrete sample prepared in Example 3, and b is the concrete sample prepared in Comparative Example 3;

[0022] Figure 2 This is a physical picture of the concrete samples prepared in Example 3 of the present invention and Comparative Example 3 after 390 cycles of salt freeze-thaw resistance test; in the figure, a is the concrete sample prepared in Example 3, and b is the concrete sample prepared in Comparative Example 3. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below through embodiments in combination with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] 1. Discussion on the composition of modified basalt flakes in the preparation method of salt-resistant and frost-resistant high-durability concrete

[0026] In order to explore the effect of the composition of modified basalt flakes on the salt freeze-thaw resistance of salt-resistant and frost-resistant high-durability concrete, the inventors conducted the following experiments, namely Example 1 and Comparative Examples 1-4, and the corresponding compositions of the modified basalt flakes are shown in Table 1.

[0027] The present invention characterizes the effect of modified basalt flakes on the salt freeze-thaw resistance of concrete by testing the salt freeze-thaw resistance of concrete specimens. Furthermore, the present invention uses mass loss rate and relative elastic modulus loss rate to represent the salt freeze-thaw resistance of concrete. Among them, when the mass loss rate exceeds 5% and the relative elastic modulus drops to 60% of the initial value, it is considered that the specimen has been destroyed, and because salt freeze-thaw damages concrete very quickly, the observation period is 7 days. According to the "quick freezing method" of GBT50082-2009 "Test method for long-term performance and durability of ordinary concrete", the freeze-thaw solution is a saturated sodium chloride solution, and the freeze-thaw resistance results are shown in Table 1.

[0028] Example 1

[0029] A salt-resistant and frost-resistant high-durable concrete, comprising the following components in parts by mass: 323 parts of ordinary Portland cement, 57 parts of 62.5-grade high-belite sulphoaluminate cement, 50 parts of microspheres, 700 parts of fine aggregate (fine sand), 1,100 parts of coarse aggregate (stone), 50 parts of modified basalt flakes, 80 parts of water, 3 parts of water reducer (early-strength polycarboxylate water reducer), and 3 parts of thickener (low-viscosity cellulose ether); wherein the modified basalt flakes are prepared from basalt flakes, versatate / vinyl acetate copolymer emulsion, and polyvinyl alcohol emulsion in a mass ratio of 1:1:0.5; the solid contents of versatate / vinyl acetate copolymer emulsion and polyvinyl alcohol emulsion are both 50%; and the mass ratio of versatate to vinyl acetate in the versatate / vinyl acetate copolymer emulsion is 1:1.

[0030] The method for preparing the above-mentioned salt-resistant and frost-resistant high-durability concrete comprises the following steps:

[0031] (1) Weigh each component according to the above formula.

[0032] (2) First, the polyvinyl alcohol emulsion and basalt flakes are mixed evenly to make the surface of the basalt flakes fully wetted, and then versatate / vinyl acetate copolymer emulsion is added, and after fully stirring, it is dried to obtain modified basalt flakes.

[0033] (3) Pour cement, water reducing agent, thickener, micro beads, fine aggregate and coarse aggregate into a mixer and mix them in a dry state for 3-5 minutes; then pour the modified basalt flakes into the mixer and mix for 1-2 minutes; then add water and mix for 2-4 minutes to obtain high-durability concrete.

[0034] Comparative Example 1

[0035] The content of a salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that in the component formula, the modified basalt flakes are prepared from basalt flakes and polyvinyl alcohol emulsion in a mass ratio of 1:0.5, and do not contain versatate / vinyl acetate copolymer emulsion.

[0036] The method for preparing the salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that: in step (1), the components are weighed according to the formula provided in this example; and in step (2), versatate / vinyl acetate copolymer emulsion is no longer added.

[0037] Comparative Example 2

[0038] The content of a salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that in the component formula, the modified basalt flakes are prepared from basalt flakes and versatate / vinyl acetate copolymer emulsion in a mass ratio of 1:1, and do not contain polyvinyl alcohol emulsion.

[0039] The method for preparing the salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that: in step (1), the components are weighed according to the formula provided in this example; and in step (2), polyvinyl alcohol emulsion is no longer added.

[0040] Comparative Example 3

[0041] The content of a salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that in the component formula, an equal amount of unmodified basalt flakes is used instead of modified basalt flakes.

[0042] The method for preparing the salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that: in step (1), the components are weighed according to the formula provided in this example; the preparation in step (2) is no longer performed; and in step (3), unmodified basalt flakes are used instead of modified basalt flakes.

[0043] Comparative Example 4

[0044] The content of a salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that: in the component formula, neither modified basalt flakes nor unmodified basalt flakes are added.

[0045] The method for preparing the salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that: in step (1), the components are weighed according to the formula provided in this example; the preparation in step (2) is no longer performed; and in step (3), no modified basalt flakes are added.

[0046] Table 1 Effect of modified basalt flake composition on salt freeze-thaw resistance of high durability concrete

[0047]

[0048] As shown in Table 1, by comparing Comparative Examples 3 and 4, it can be seen that the addition of unmodified basalt flakes can improve the salt and frost resistance of concrete, but the effect is not obvious, mainly because basalt flakes can delay the migration rate of water and chloride ions carried by water, but because of its strong water absorption rate, it cannot prevent the migration of water and chloride ions, but can only delay. By comparing Comparative Examples 1 and 3, it can be seen that after the unmodified basalt flakes are only modified with hydrophilic polyvinyl alcohol, the basalt flakes have no obvious effect on improving the frost and salt resistance of concrete. By comparing Comparative Examples 2 and 3, it can be seen that after the unmodified basalt flakes are only modified with hydrophobic tert-butyl ester / vinyl acetate copolymer emulsion, the salt and frost resistance of concrete is significantly improved; compared with the blank concrete (Comparative Example 4), the concrete of basalt flakes modified with tert-butyl ester / vinyl acetate copolymer emulsion has a mass loss rate of 5%, and the number of cycles when the relative elastic modulus drops to 60% of the initial value is increased by 220% and 260%, respectively. Therefore, compared with polyvinyl alcohol emulsion, the salt and frost resistance of concrete modified by tert-butyl vinyl carbonate / vinyl acetate copolymer emulsion alone is better. However, by comparing Example 1 and Comparative Example 3, it can be seen that the salt and frost resistance of basalt flakes modified by tert-butyl vinyl carbonate / vinyl acetate copolymer emulsion and polyvinyl alcohol emulsion are significantly improved compared with the unmodified basalt flakes. Compared with the blank concrete (Comparative Example 4), the concrete modified by tert-butyl vinyl carbonate / vinyl acetate copolymer emulsion has a 310% and 370% increase in the number of cycles when the mass loss rate reaches 5% and the number of cycles when the elastic modulus drops to 60% of the initial value, respectively. . This result is due to the obvious hydrophobic effect of versatate / vinyl acetate copolymer emulsion, which can easily cause the surface of some basalt flakes to not be fully infiltrated during the dispersion process. Therefore, hydrophilic polyvinyl alcohol emulsion is selected as a dispersant to first make the surface of the basalt flakes fully infiltrated by the polymer, and then disperse the hydrophobic versatate / vinyl acetate copolymer emulsion evenly on the surface of the basalt flakes. The two work together to achieve better salt and frost resistance.

[0049] (II) Discussion on the amount of modified basalt flakes in the preparation method of salt-resistant and frost-resistant high-durability concrete

[0050] In order to explore the effect of the amount of modified basalt flakes on the salt freeze-thaw resistance of salt-resistant and frost-resistant high-durability concrete, the inventors conducted the following experiments, namely, Examples 1 to 5, and the corresponding compositions of the modified basalt flakes are shown in Table 2, and the corresponding salt freeze-thaw resistance results are shown in Table 2.

[0051] Example 2

[0052] The content of a salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that: in the component formula, the modified basalt flakes account for 40 parts.

[0053] The method for preparing the salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that the formula described in step (1) is the formula provided in this example.

[0054] Example 3

[0055] The content of a salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that: in the component formula, the modified basalt flakes account for 60 parts.

[0056] The method for preparing the salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that the formula described in step (1) is the formula provided in this example.

[0057] Example 4

[0058] The content of a salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that: in the component formula, the modified basalt flakes account for 70 parts.

[0059] The method for preparing the salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that the formula described in step (1) is the formula provided in this example.

[0060] Example 5

[0061] The content of a salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that: in the component formula, the modified basalt flakes account for 80 parts.

[0062] The method for preparing the salt-resistant and frost-resistant high-durability concrete is basically the same as that of Example 1, except that the formula described in step (1) is the formula provided in this example.

[0063] Table 2 Effect of modified basalt flake dosage on salt freeze-thaw resistance of high durability concrete

[0064]

[0065] It can be seen from Table 2 that when the mass loss reaches 5% and the relative elastic modulus reaches 60% of the initial value, the number of cycles of concrete increases first and then decreases with the increase of modified basalt flakes. This is because, after adding modified basalt flakes, the basalt flakes are evenly arranged in the concrete, and the basalt flakes can fill the cement pores, which can not only increase the density of the cement paste, but also produce a "maze effect", change the medium transmission path, force the transmission path to be tortuous, and prevent medium transmission, which is equivalent to increasing the thickness of the concrete; versatate / vinyl acetate copolymer emulsion and polyvinyl alcohol emulsion react with CSH gel to form a three-dimensional spatial network structure covering the surface of cement particles. After versatate / vinyl acetate copolymer emulsion reacts with cement through physical adsorption and chemical adsorption, its hydrophobic end extends to the pores. When the hydrophobic layer formed on the surface of cement concrete contacts with the deicing salt solution, a wetting angle greater than 90° is formed at the interface, which prevents chloride ions, calcium and magnesium ions and water from diffusing into the concrete, hinders the movement of medium water, and then hinders the movement of ions, thereby improving the alkali and salt resistance of concrete. However, when the dosage of modified basalt flakes is too large, versatate / vinyl acetate copolymer emulsion and polyvinyl alcohol emulsion will cover the surface of cement particles and affect the hydration of cement, thereby affecting the performance of concrete. Therefore, adding an appropriate amount of modified basalt flakes can significantly improve the salt freeze-thaw resistance of concrete.

[0066] The salt-resistance freeze-thaw cycle photos of the concrete samples prepared in Example 3 and Comparative Example 3 are as follows: Figure 1 and Figure 2 As shown. Figure 1 It can be seen that after the concrete sample was circulated 120 times, the mass loss of the sample of comparative example 3 reached 5%, but at this time the sample of embodiment 3 was still intact. Figure 2 It can be seen that after the concrete sample was cycled 390 times, when the mass loss of the sample in Example 3 reached 5%, the control group had already peeled off nearly half of its mass.

[0067] In summary, the present invention effectively overcomes the deficiencies in the prior art and has a high industrial utilization value. The above embodiments serve to illustrate the substantive content of the present invention, but do not limit the protection scope of the present invention. Those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and protection scope of the technical solution of the present invention.

Claims

1. A salt-resistant and frost-resistant high-durability concrete, characterized in that: The material composition includes the following parts by weight: 360-410 parts of cement, 40-60 parts of microspheres, 680-750 parts of fine aggregate, 1100-1150 parts of coarse aggregate, 30-80 parts of modified basalt flakes, 50-150 parts of water, 3-5 parts of water reducer, and 3-5 parts of thickener; The modified basalt flakes are mainly formed by modifying the basalt flakes with versatate / vinyl acetate copolymer emulsion and polyvinyl alcohol emulsion; The mass ratio of the basalt flakes, versatate / vinyl acetate copolymer emulsion and polyvinyl alcohol emulsion is (1-3): (1-4): (0.5-1).

2. The high-durability concrete according to claim 1, characterized in that: The basalt flakes have a diameter of 10 μm-3 mm and a thickness of 1-3 μm.

3. The high durability concrete according to claim 2, characterized in that: In the versatate vinyl carbonate / vinyl acetate copolymer emulsion, the mass ratio of versatate vinyl carbonate to vinyl acetate is (1-2): (1-5).

4. The high-durability concrete according to claim 3, characterized in that: The preparation method of the modified basalt flakes is as follows: firstly, polyvinyl alcohol emulsion and basalt flakes are uniformly mixed, then versatate vinyl carbonate / vinyl acetate copolymer emulsion is added and stirred uniformly, and the modified basalt flakes are obtained after drying.

5. The high-durability concrete according to claim 1, characterized in that: The thickener is low-viscosity cellulose ether with a relative molecular mass of 400-10000.

6. The high-durability concrete according to claim 1, characterized in that: The water reducer is an early strength polycarboxylate water reducer.

7. The high-durability concrete according to claim 1, characterized in that: The cement consists of ordinary Portland cement and high-belite sulphoaluminate cement.

8. The method for preparing high-durability concrete according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: mixing cement, water reducing agent, thickener, micro beads, fine aggregate and coarse aggregate in dry state uniformly; then adding modified basalt flakes and water in sequence and continuing to stir to obtain high-durability concrete.

9. Use of the high-durability concrete according to any one of claims 1 to 7 in salt-resistant and frost-resistant materials.

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