Conductive mortar as well as preparation method and application thereof

Abstract

The invention discloses conductive mortar and a preparation method and application thereof, and relates to the technical field of reinforced concrete. The conductive mortar is prepared from the following components in parts by mass: 650 to 700 parts of cement, 1000 to 1050 parts of gravel, 12 to 15 parts of carbon fiber, 12 to 14 parts of dispersible latex powder, 250 to 280 parts of water, 7 to 21 parts of nano aluminum oxide and 2 to 3 parts of a water reducing agent. Wherein the cement comprises Portland cement and sulphoaluminate cement in a mass ratio of (3-5): (5-7). The sulphoaluminate and the ordinary silicate are co-doped, so that the macropores are increased, the chloride ion diffusion efficiency is enhanced, and the nano aluminum oxide can be combined to realize mechanical property adjustment, adsorb and convert more free chloride ions and degrade secondary corrosion. The cementing material is combined with the dispersible latex powder and the carbon fibers to achieve a synergistic effect, so that a good conductive network is constructed, and the conductivity of the cement is improved; similarly, the network structure formed by interweaving the carbon fibers is also beneficial to improving the mechanical property.

Description

Technical Field

[0001] The present invention relates to the technical field of reinforced concrete, and in particular to a conductive mortar and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] During the long-term use of reinforced concrete structures in coastal environments, the passive film of the steel bars inside the concrete is easily damaged by chloride ion erosion, which causes pitting corrosion, electrochemical corrosion and other corrosion phenomena in the steel bars inside the concrete. The corrosion products generated will expand from the inside and destroy the concrete, thus affecting the safety of the concrete structure. Electrochemical desalination is one of the important means to avoid steel corrosion. The principle is to use electrochemical methods to reduce the chloride ion concentration near the steel bars to prevent chloride ions from contacting the internal steel bars.

[0004] Conductive mortar anode is one of the important anodes in the electrochemical desalination method of reinforced concrete, but its overall electrochemical desalination effect is poorer than that of traditional desalination, especially the electrochemical extraction efficiency of chloride ions is poor. The prior art believes that: high-porosity anodes will enhance ion migration and improve electrochemical dechlorination efficiency, but this high porosity will make the anode fail to meet the basic mechanical performance requirements; and there are too many free chloride ions inside the conductive mortar anode, resulting in the effect of reducing the chloride ion concentration near the steel bars after the electrochemical dechlorination is completed, but the chloride ions will diffuse back to the vicinity of the steel bars along the path of "conductive mortar anode-concrete-near the steel bars" due to the concentration difference, causing secondary corrosion of the steel bars in the concrete. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a conductive mortar and a preparation method and application thereof, which can improve the electrochemical dechlorination efficiency by compounding silicate cement and sulphoaluminate cement and adding carbon fiber and nano-alumina sol, while also achieving mechanical properties.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] The first aspect of the present invention provides a conductive mortar, comprising the following components in parts by mass: 650-700 parts of cement, 1000-1050 parts of sand and gravel, 12-15 parts of carbon fiber, 12-14 parts of dispersible latex powder, 250-280 parts of water, 0-21 parts of nano-alumina and 2-3 parts of water reducer; wherein the cement comprises silicate cement and sulphoaluminate cement in a mass ratio of (3-5):(5-7).

[0008] In a second aspect, the method for preparing the conductive mortar comprises the steps of:

[0009] S1, mixing cement, sand and carbon fiber evenly to obtain a first mixture;

[0010] S2, adding the dispersible latex powder into water and dispersing it evenly to obtain mixing water;

[0011] S3. Add mixing water and nano-alumina sol to the first mixture, and stir evenly to obtain conductive mortar.

[0012] In a third aspect, the application of the conductive mortar includes: preparing a conductive mortar anode for application in an electrochemical dechlorination method for reinforced concrete, comprising the steps of:

[0013] S4, applying the conductive mortar directly on the surface of reinforced concrete to obtain a conductive mortar anode;

[0014] S5, connect the positive electrode with conductive mortar anode, and connect the steel bars in reinforced concrete to the negative electrode, at 0.5~5A / m 2 power ups.

[0015] Optionally, in S4, the thickness of the conductive mortar anode is 10 mm to 20 mm, and it is cured for one day at a standard temperature of 20° C. and a humidity of ±90%.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1. The present invention provides a conductive mortar, wherein the cement is obtained by mixing sulphoaluminate and ordinary silicate, and while increasing the macropores and enhancing the diffusion efficiency of chloride ions, it can also be combined with nano-alumina to achieve mechanical property adjustment, wherein the hydration reaction of nano-alumina with cement converts part of the CSH gel (hydrated calcium silicate) into CASH gel (hydrated calcium aluminosilicate gel), thereby absorbing and converting more free chloride ions, turning them into combined chloride ions, thereby reducing the content of free chloride ions and degrading secondary corrosion; that is, it has high strength, fast hardening, and high dechlorination effects. The cementitious material (including cement and nano-alumina) combines with dispersible latex powder and carbon fiber to play a synergistic role, and the larger macropores can construct a good conductive network and improve the conductivity of cement; similarly, the network structure interwoven by carbon fibers is also conducive to maintaining mechanical properties or reducing the reduction in mechanical properties.

[0018] 2. The electrochemical dechlorination method of the present invention is simple to operate and can be used to reinforce damaged materials. After the conductive mortar is cured on the surface of reinforced concrete, it can serve as a part of the concrete component for a long time under stress conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0020] In order to show the positions of various parts, the distances or sizes between them are exaggerated in the figure, and the schematic diagram is for illustration only.

[0021] Figure 1 This is a graph of the electrochemical extraction detection results in Example 1.

[0022] Figure 2 This is a graph of the electrochemical extraction detection results in Example 2.

[0023] Figure 3 This is a graph of the electrochemical extraction detection results in Example 3.

[0024] Figure 4 This is a graph of the electrochemical extraction detection results in Example 4.

[0025] Figure 5 1 and 1 are graphs showing the mechanical properties test results of the embodiments and comparative examples, wherein (a) is the compressive strength test result, and (b) is the flexural strength test result.

[0026] Figure 6 It is a graph showing the coagulation time test results of various embodiments and comparative examples.

[0027] Figure 7 It is a graph of the cumulative porosity detection results of each embodiment and comparative example.

[0028] Figure 8 1 is a graph showing the chloride ion binding rate test results of each embodiment and comparative example.

[0029] Fig. 9 This is the electrochemical extraction test result of Comparative Example 1. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0031] A conductive mortar comprises the following components in parts by mass: 690-700 parts of cement, 1035-1050 parts of sand and gravel, 4.1-4.2 parts of carbon fiber, 13.8-14 parts of dispersible latex powder, 250-280 parts of water, 0-21 parts of nano-alumina, and 7-21 parts of water reducing agent; wherein the cement comprises silicate cement and sulphoaluminate cement in a mass ratio of (3-5):(5-7).

[0032] Among the above ingredients, the composite cement provides higher calcium ions for sulfoaluminate while generating hydration products that can combine with chloride salts, and provides relatively high porosity, which can form larger pore sizes and has early hardness. It has high strength and fast hardening properties in synergy with nano-alumina, and can more effectively adsorb and convert free chloride ions to reduce secondary corrosion problems. The three synergistic effects of cementitious materials, dispersible latex powder and carbon fiber can construct a good conductive network, improve the conductivity of cement, and thus improve the dechlorination effect.

[0033] Optionally, the cement is silicate cement and sulphoaluminate cement of grade 42.5 or above, so that it has mechanical properties comparable to those of reinforced concrete structures in coastal environments.

[0034] Optionally, the sand and gravel particle size is less than 2 mm, specifically 0.063 mm to 2 mm, which can provide higher mechanical strength for the conductive mortar.

[0035] Optionally, the carbon fiber is glue-free chopped carbon fiber with a length of 5 to 7 mm, a diameter of 6 to 7 μm, a tensile strength of 4500 to 4800 MPa, an elastic modulus of 230 to 240 GPa, good electrical conductivity and mechanical properties, and is used to construct a conductive network and enhance mechanical properties.

[0036] Optionally, the dispersible latex powder is one or more of vinyl acetate / ethylene copolymer powder, vinyl acetate copolymer powder and ethylene copolymer powder, and has a particle size of 150 to 210 meshes; and can improve the interface bonding strength between the latex powder and reinforced concrete.

[0037] Optionally, the nano-alumina particle size is 20 to 30 nm, and is added in the form of a nano-alumina sol with a solid content of 20 to 30 wt%.

[0038] Optionally, the water reducer is a high-efficiency polycarboxylate water reducer, which has a higher water-reducing effect when used in combination with silicate cement and sulphoaluminate cement.

[0039] Optionally, the composition includes the following components in parts by weight: 690-700 parts of cement, 1035-1050 parts of sand and gravel, 12-15 parts of carbon fiber, 13.8-14 parts of dispersible latex powder, 276-280 parts of water, 7-21 parts of nano-alumina and 2.1-2.8 parts of water reducing agent.

[0040] The method for preparing the conductive mortar comprises the following steps:

[0041] S1, mixing cement, sand and carbon fiber evenly to obtain a first mixture;

[0042] S2, adding the dispersible latex powder into water and dispersing it evenly to obtain mixing water;

[0043] S3. Add mixing water and nano-alumina sol to the first mixture, and stir evenly to obtain conductive mortar.

[0044] In the preparation method, the mixing method in S1 is low-speed dry mixing, the dispersion method in S2 is mechanical stirring, and the stirring method in S3 is low-speed stirring using a mortar mixer.

[0045] The application of the conductive mortar includes: preparing a conductive mortar anode for electrochemical chlorine removal, including the steps of:

[0046] S4, applying the conductive mortar directly on the surface of reinforced concrete to obtain a conductive mortar anode;

[0047] S5, connect the positive electrode with conductive mortar anode, and connect the steel bars in reinforced concrete to the negative electrode, at 0.5~5A / m 2 power ups.

[0048] Optionally, in S4, the surface of the reinforced concrete is pretreated: the steel bars are first derusted and then immersed in a saturated calcium hydroxide solution.

[0049] Optionally, in S4, the thickness of the conductive mortar anode is 10 to 20 mm and is cured for one day at a standard temperature of 20° C. and a humidity of ±90%.

[0050] Example 1

[0051] A conductive mortar comprises the following components in parts by mass: 700 parts of cement, 1050 parts of sand and gravel, 12 parts of carbon fiber, 14 parts of dispersible latex powder, 252 parts of water, 35 parts of nano-alumina sol with a solid content of 20% (including 28 parts of water) and 2.1 parts of a water reducing agent; wherein the cement comprises 210 parts of 42.5-grade ordinary silicate and 490 parts of 42.5-grade sulphoaluminate cement; and if the water in the nano-alumina sol is calculated separately, the total water content is 280 parts.

[0052] The particle size of sand and gravel is 0.063mm~2mm.

[0053] The carbon fiber is glue-free chopped carbon fiber with a length of 5 to 7 mm, a diameter of 6 to 7 μm, a tensile strength of 4500 to 4800 MPa, and an elastic modulus of 230 to 240 GPa.

[0054] The dispersible latex powder is vinyl acetate / ethylene copolymer powder.

[0055] The nano-alumina particles contained in the nano-alumina sol have a particle size of 20 nm.

[0056] The water reducer is a high-efficiency polycarboxylate water reducer.

[0057] The method for preparing the conductive mortar of this embodiment comprises the following steps:

[0058] S1, mixing cement, sand and carbon fiber, and dry-mixing at a low speed to obtain a first mixture;

[0059] S2, adding the dispersible latex powder into water and dispersing it evenly to obtain mixing water;

[0060] S3. Add mixing water and nano-alumina sol to the first mixture, and stir evenly to obtain conductive mortar.

[0061] The conductive mortar of this embodiment is used for electrochemical dechlorination of reinforced concrete, comprising the following steps:

[0062] S4. Apply the conductive mortar directly on the surface of the dry reinforced concrete test block and cure (at a standard temperature of 20°C and a humidity of ±90% for one day) to obtain reinforced concrete with an external coating of a 10mm thick conductive mortar anode; the size of the reinforced concrete (C35) is 100mm×100mm×300mm, and the thickness of the outer protective layer of the steel bar is 30mm; sodium chloride is added internally to simulate the chloride ion environment inside the actual reinforced concrete, and the chloride ion concentration inside the reinforced concrete test block is measured to be about 0.45% through grinding and titration of the concrete protective layer.

[0063] S5. Connect the conductive mortar anode to the positive pole of the DC power supply, and the steel bars in the reinforced concrete to the negative pole of the DC power supply. The power-on parameter is 1A / m 2 , electrochemical extraction of chloride, the power-on time is 7 days.

[0064] Test content:

[0065] After 7 days of power-on according to step S5, the chloride ion concentration of the cross section of the reinforced concrete with the conductive mortar anode was detected. The results are as follows: Figure 1 As shown, within the conductive mortar anode range, the chloride ion concentration is below 0.1%, within the concrete range is below 3.5%, and within 10 mm around the steel bars is stable at around 3.0%, and the electrochemical extraction efficiency of chloride is 41.7%.

[0066] The calculation method of chloride ion concentration is:

[0067] Where G is the weight of concrete, C AgNO3 is the concentration of silver nitrate, V3 is the volume of deionized water used for sample soaking, V4 is the supernatant extracted during titration, and V5 is the volume of silver nitrate consumed.

[0068] The current parameter is defined as the current intensity passing through a unit area.

[0069] The calculation method for the electrochemical extraction efficiency of chloride is:

[0070] Among them, P 混凝土初始 is the chloride ion concentration before electroextraction, P 混凝土残余为 Chloride ion concentration after electroextraction.

[0071] Example 2

[0072] A conductive mortar comprises the following components in parts by mass: 700 parts of cement, 1035 parts of sand and gravel, 13 parts of carbon fiber, 14 parts of dispersible latex powder, 224 parts of water, 70 parts of nano-alumina sol with a solid content of 20%, and 2.8 parts of a water reducing agent; wherein the cement comprises 210 parts of 42.5-grade ordinary silicate and 490 parts of 42.5-grade sulphoaluminate cement.

[0073] The preparation method of the conductive mortar and the method of electrochemically removing chlorine from reinforced concrete using the conductive mortar of this embodiment are the same as those in Example 1. Figure 2 As shown, the electrochemical extraction efficiency of chloride is 41.7%.

[0074] Example 3

[0075] A conductive mortar comprises the following components in parts by mass: 700 parts of cement, 1050 parts of sand and gravel, 14 parts of carbon fiber, 14 parts of dispersible latex powder, 196 parts of water, 105 parts of nano-alumina sol with a solid content of 20%, and 2.8 parts of a water reducing agent; wherein the cement comprises 210 parts of 42.5-grade ordinary silicate and 490 parts of 42.5-grade sulphoaluminate cement.

[0076] The preparation method of the conductive mortar and the method of electrochemically removing chlorine from reinforced concrete using the conductive mortar of this embodiment are the same as those in Example 1. Figure 3 As shown, the electrochemical extraction efficiency of chloride is 45.8%.

[0077] Example 4

[0078] A conductive mortar comprises the following components in parts by mass: 700 parts of cement, 1050 parts of sand and gravel, 15 parts of carbon fiber, 14 parts of dispersible latex powder, 252 parts of water, and 2.8 parts of water reducing agent; wherein the cement comprises 210 parts of 42.5-grade ordinary silicate and 490 parts of 42.5-grade sulphoaluminate cement.

[0079] The preparation method of the conductive mortar and the method of electrochemically removing chlorine from reinforced concrete using the conductive mortar of this embodiment are the same as those in Example 1. Figure 4 As shown, the electrochemical extraction efficiency of chloride is 46.3%.

[0080] Comparative Example 1

[0081] A conductive mortar comprises the following components in parts by mass: 700 parts of cement, 1050 parts of sand and gravel, 12 parts of carbon fiber, 14 parts of dispersible latex powder, 252 parts of water, 35 parts of nano-alumina sol with a solid content of 20%, and 2.1 parts of a water reducing agent; wherein all the cement is 42.5-grade sulphoaluminate cement.

[0082] The preparation method of the conductive mortar and the method of electrochemically removing chlorine from reinforced concrete using the conductive mortar of this embodiment are the same as those in Example 1. Fig. 9 shown.

[0083] Other performance tests

[0084] Mechanical properties of Example 1 (70% sulphoaluminate cement and 30% ordinary silicate cement plus 1% nano alumina sol), Example 2 (70% sulphoaluminate cement and 30% ordinary silicate cement plus 2% nano alumina sol), Example 3 (70% sulphoaluminate cement and 30% ordinary silicate cement plus 3% nano alumina sol), Example 4 (70% sulphoaluminate cement and 30% ordinary silicate cement) and Comparative Example 1 (sulphoaluminate cement) were tested. The results are as follows: Figure 5 As shown; perform clotting time test, the result is as follows Figure 6 As shown; cumulative porosity test is performed, and the results are as follows Figure 7 As shown; the chloride ion binding rate test was performed, and the results were as follows Figure 8 It can be seen that although Comparative Example 4 has good electrochemical extraction efficiency and high porosity, its mechanical strength is low, especially the strength at 28 days has a downward trend, and although the early coagulation time is increased, its final coagulation time does not change.

[0085] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A conductive mortar, characterized in that: The invention comprises the following components in parts by weight: 650-700 parts of cement, 1000-1050 parts of sand and gravel, 12-15 parts of carbon fiber, 12-14 parts of dispersible latex powder, 250-280 parts of water, 0-21 parts of nano-alumina and 2-3 parts of water reducing agent; wherein the cement comprises silicate cement and sulphoaluminate cement in a mass ratio of (3-5):(5-7).

2. The conductive mortar according to claim 1, characterized in that: The cement is silicate cement and sulphoaluminate cement of grade 42.5 or above.

3. The conductive mortar according to claim 2, characterized in that: The sand and gravel particle size is less than 2 mm.

4. The conductive mortar according to claim 1, characterized in that: The carbon fiber is glue-free short-cut carbon fiber with a length of 5 to 7 mm and a diameter of 6 to 7 um.

5. The conductive mortar according to claim 1, characterized in that: The dispersible latex powder is one or more of vinyl acetate / ethylene copolymer rubber powder, vinyl acetate copolymer rubber powder and ethylene copolymer rubber powder; Optionally, the water reducer is a high-efficiency polycarboxylate water reducer.

6. The conductive mortar according to claim 1, characterized in that: The nano-alumina particle size is 20-30 nm, and is added in the form of nano-alumina sol with a solid content of 20-30 wt%.

7. The conductive mortar according to any one of claims 1 to 6, characterized in that: The invention comprises the following components in parts by weight: 690-700 parts of cement, 1035-1050 parts of sand and gravel, 12-15 parts of carbon fiber, 13.8-14 parts of dispersible latex powder, 276-280 parts of water, 7-21 parts of nano-alumina and 2.1-2.8 parts of water reducing agent.

8. A method for preparing a conductive mortar according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, mixing cement, sand and carbon fiber evenly to obtain a first mixture; S2, adding the dispersible latex powder into water and dispersing it evenly to obtain mixing water; S3. Add mixing water and nano-alumina sol to the first mixture, and stir evenly to obtain conductive mortar.

9. An application of the conductive mortar according to any one of claims 1 to 7, characterized in that: The invention relates to an electrochemical dechlorination method for preparing a conductive mortar anode and applying it to reinforced concrete, comprising the steps of: S4, applying the conductive mortar directly on the surface of reinforced concrete to obtain a conductive mortar anode; S5, connect the positive electrode with conductive mortar anode, and connect the steel bars in reinforced concrete to the negative electrode, at 0.5~5A / m 2 power ups.

10. The use of the conductive mortar according to claim 9, characterized in that: In S4, the thickness of the conductive mortar anode is 10 to 20 mm.

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