Conductive mortar, method for its preparation and use

Abstract

The application relates to a conductive mortar and a preparation method and application thereof, and relates to the technical field of reinforced concrete. The conductive mortar comprises the following components in mass parts: cement 650-700 parts, sand and gravel 1000-1050 parts, carbon fiber 12-15 parts, dispersible latex powder 12-14 parts, water 250-280 parts, nano-alumina 7-21 parts, and water reducing agent 2-3 parts; wherein the cement comprises silicate cement and sulphoaluminate cement in a mass ratio of (3-5):(5-7). The sulphoaluminate and the ordinary silicate are complexly doped, can improve large pore porosity and enhance the diffusion efficiency of chloride ions, can combine with nano-alumina to realize mechanical property adjustment, can absorb and convert more free chloride ions, and can degrade secondary corrosion. The cementing material combines the dispersible latex powder and the carbon fiber to play a synergistic effect, to build a good conductive network, and to improve the conductive performance of the cement; similarly, the network structure formed by the interwoven carbon fibers is also beneficial to improving the mechanical property.

Description

TECHNICAL FIELD

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

[0002] The information disclosed in this Background section is only for the purpose of increasing an understanding of the general background of the application and does not necessarily constitute an admission by the patent applicant or the patent owner that this information forms prior art.

[0003] In the long-term use of reinforced concrete structures in coastal environments, the internal steel reinforcement passivation film of concrete is easily damaged by long-term chloride ion corrosion, which further causes internal steel reinforcement of concrete to be subjected to pitting corrosion, electrochemical corrosion and other corrosion phenomena. The expansion of the corrosion products produced from the inside will damage the concrete, thereby affecting the safety of the concrete structure. Electrochemical desalination is one of the important means to avoid steel corrosion, and the principle is to reduce the chloride ion concentration near the steel by using electrochemical methods to avoid the contact of chloride ions with the internal steel.

[0004] The conductive mortar anode is one of the important anodes of the electrochemical desalination method of reinforced concrete, but its overall electrochemical desalination effect is poorer than that of the traditional desalination effect, especially the electrochemical extraction of chloride ions. The prior art believes that: the anode with high porosity will enhance the migration of ions and improve the electrochemical chlorine removal efficiency, but such high porosity will make the anode not meet the basic mechanical performance requirements; and there are too many free chloride ions in the conductive mortar anode, which causes the chloride ions to diffuse to the vicinity of the steel along the path of "conductive mortar anode-concrete-steel vicinity" due to the concentration difference after the electrochemical chlorine removal, thereby causing secondary corrosion of the steel in the concrete. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a conductive mortar and a preparation method and application thereof, which realizes the improvement of the electrochemical chlorine removal efficiency by the compounding of Portland cement and sulphoaluminate cement and the addition of carbon fibers and nano-alumina sol, and simultaneously has mechanical properties.

[0006] In order to achieve the above-mentioned purpose, the present application is realized by the following technical scheme:

[0007] The first aspect of the present application provides a conductive mortar, which comprises the following components in mass fraction: cement 650-700 parts, sandstone 1000-1050 parts, carbon fibers 12-15 parts, dispersible latex powder 12-14 parts, water 250-280 parts, nano-alumina 0-21 parts and water reducing agent 2-3 parts; wherein the cement comprises Portland 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 following steps:

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

[0010] S2, uniformly dispersing dispersible latex powder in water to obtain mixing water;

[0011] S3, adding the mixing water and nano-alumina sol to the first mixture and uniformly stirring to obtain the conductive mortar.

[0012] In a third aspect, the application of the conductive mortar comprises the following steps for the electrochemical dechlorination method of the conductive mortar anode applied to reinforced concrete:

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

[0014] S5, connecting the conductive mortar anode to the positive electrode and connecting the steel bars in the reinforced concrete to the negative electrode, and applying a current of 0.5-5 A / m 2

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

[0016] The present application has the following advantages:

[0017] 1. The present application provides a conductive mortar, wherein the cement is obtained by mixing sulphoaluminate and ordinary Portland cement, which can improve the large pore and enhance the diffusion efficiency of chloride ions, and can also combine with nano-alumina to adjust the mechanical properties, wherein the hydration reaction of nano-alumina and cement can convert part of C-S-H gel (calcium silicate hydrate) into C-A-S-H gel (calcium aluminate hydrate gel), thereby adsorbing and converting more free chloride ions into bound 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 effect. The cementitious material (including cement and nano-alumina) can play a synergistic effect with dispersible latex powder and carbon fibers, and the large pore space can construct a good conductive network to improve the conductive performance of the cement; similarly, the network structure formed by the interweaving of carbon fibers is also conducive to maintaining the mechanical properties or reducing the decrease in the mechanical properties.

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

[0019] ​The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application and are incorporated herein by reference. The embodiments depicted within the drawings are in some instances simplified for the sake of discussion and therefore are intended as illustrative only.

[0020] The distances or sizes between the parts are exaggerated in the drawings for showing the positions of the parts, and the schematic diagrams are only used for illustration.

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

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

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

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

[0025] Figure 5 is a graph of the mechanical property detection result of each example and comparative example, wherein (a) is the compressive strength detection result, and (b) is the flexural strength detection result.

[0026] Figure 6 is a graph of the setting time detection result of each example and comparative example.

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

[0028] Figure 8 is a graph of the chloride ion binding rate detection result of each example and comparative example.

[0029] Figure 9 is the electrochemical extraction detection result of Comparative Example 1. DETAILED DESCRIPTION

[0030] The application will be further described below in conjunction with the drawings and examples.

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

[0032] In the above ingredients, the complexed cement provides higher calcium ions for the sulphoaluminate, generates hydration products that can combine with chloride salts, and provides higher porosity, enabling the formation of larger pore sizes, and has early hardness, and cooperates with nano-aluminum oxide to have high strength and fast hardening characteristics, and can more effectively adsorb and convert free chloride ions, reducing the problem of secondary corrosion; the synergy of cementitious materials, dispersible latex powder and carbon fibers can build a good conductive network, improve the electrical conductivity of cement, and thus improve the dechlorination effect.

[0033] Optionally, the cement is a Portland cement and a sulphoaluminate cement of grade 42.5 or above, so as to have mechanical properties comparable to reinforced concrete structures in a coastal environment.

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

[0035] Optionally, the carbon fiber is a glue-free chopped carbon fiber with a length of 5-7mm and a diameter of 6-7μm, and a tensile strength of 4500-4800MPa; an elastic modulus of 230-240GPa, having good electrical conductivity and mechanical properties, for building a conductive network and strengthening 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, with a particle size of 150-210 mesh; which can improve the interfacial bond strength between the reinforced concrete.

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

[0038] Optionally, the water reducing agent is a high-efficiency polycarboxylic acid water reducing agent, which has a high water-reducing effect when used with Portland cement and sulphoaluminate cement.

[0039] Optionally, the components include cement 690-700 parts, sand and gravel 1035-1050 parts, carbon fiber 12-15 parts, dispersible latex powder 13.8-14 parts, water 276-280 parts, nano-aluminum oxide 7-21 parts and water reducing agent 2.1-2.8 parts.

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

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

[0042] S2, dispersing the dispersible latex powder in water to obtain a mixing water;

[0043] S3, adding mixing water and nano-alumina sol to the first mixture, and stirring to obtain the 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 stirrer.

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

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

[0047] S5, connecting the positive electrode with the conductive mortar anode, and connecting the negative electrode with the steel bars in the reinforced concrete, and applying a current of 0.5-5 A / m 2

[0048] Optionally, in S4, the surface of the reinforced concrete is pretreated: the steel bars are first subjected to rust removal treatment, and then soaked in a saturated calcium hydroxide solution.

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

[0050] Embodiment 1

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

[0052] The sandstone has a particle size of 0.063 mm-2 mm.

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

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

[0055] The nano-alumina sol contains nano-alumina with a particle size of 20 nm.

[0056] The water reducing agent is a high-efficiency polycarboxylic acid water reducing agent.

[0057] The preparation method of the conductive mortar of the embodiment includes the steps of:​

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

[0059] S2, dispersible latex powder is added to water and uniformly dispersed to obtain mixing water;

[0060] S3, the mixing water and nano-alumina sol are added to the first mixture and uniformly stirred to obtain conductive mortar.

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

[0062] S4, the conductive mortar is directly applied to the surface of the dry reinforced concrete test block and cured (cured for one day under standard temperature of 20℃ and humidity of ±90%) to obtain reinforced concrete with an external coating of 10mm-thick conductive mortar anode; wherein the size of the reinforced concrete (C35) is 100mm×100mm×300mm, the thickness of the outer protective layer of the steel bar is 30mm; the internal chloride ion environment of the actual reinforced concrete is simulated by internal doping of sodium chloride, and the chloride ion concentration in the reinforced concrete test block is measured by concrete protective layer powdering and titration to be about 0.45%.

[0063] S5, the conductive mortar anode is connected to the positive electrode of a direct current power supply, and the steel bar in the reinforced concrete is connected to the negative electrode of the direct current power supply, and the electric current parameter is 1A / m 2 , and the electrochemical extraction of chloride is performed for 7 days.

[0064] Test content:

[0065] After the step S5 of power supply for 7 days, the chloride ion concentration of the cross section of the reinforced concrete with the conductive mortar anode is detected, and the results are shown in Figure 1 , the chloride ion concentration in the range of the conductive mortar anode is below 0.1%, the chloride ion concentration in the range of the concrete is below 3.5%, and the chloride ion concentration in the range of 10mm near the steel bar is stably about 3.0%, and the electrochemical extraction efficiency of chloride is 41.7%.

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

[0067] Wherein, G is the weight of the concrete, C AgNO3 is the concentration of silver nitrate, V3 is the volume of deionized water taken by the sample immersion, V4 is the supernatant extracted during titration, and V5 is the volume of silver nitrate consumed.

[0068] The definition of the electric current parameter is the current intensity passing through the unit area.

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

[0070] P0 混凝土初始 P0 混凝土残余为 P0

[0071] Example 2

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

[0073] The preparation method of the conductive mortar and the method of electrochemical dechlorination of reinforced concrete using the conductive mortar of the present example are the same as those of Example 1, and the results are shown in Table 1. Figure 2 The electrochemical extraction of chloride efficiency is 41.7%.

[0074] Example 3

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

[0076] The preparation method of the conductive mortar and the method of electrochemical dechlorination of reinforced concrete using the conductive mortar of the present example are the same as those of Example 1, and the results are shown in Table 1. Figure 3 The electrochemical extraction of chloride efficiency is 45.8%.

[0077] Example 4

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

[0079] The preparation method of the conductive mortar and the method of electrochemical dechlorination of reinforced concrete using the conductive mortar of the present example are the same as those of Example 1, and the results are shown in Table 1. Figure 4 The electrochemical extraction of chloride efficiency is 46.3%.

[0080] Comparative Example 1

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

[0082] The preparation method of the conductive mortar and the method of electrochemical dechlorination of reinforced concrete using the conductive mortar of the embodiment are the same as those of embodiment 1, and the results are shown in Figure 9 .

[0083] Other performance tests

[0084] The mechanical performance tests are carried out on embodiment 1 (70% sulphoaluminate cement and 30% ordinary Portland cement plus 1% nano-alumina sol), embodiment 2 (70% sulphoaluminate cement and 30% ordinary Portland cement plus 2% nano-alumina sol), embodiment 3 (70% sulphoaluminate cement and 30% ordinary Portland cement plus 3% nano-alumina sol), embodiment 4 (70% sulphoaluminate cement and 30% ordinary Portland cement), and comparative example 1 (sulphoaluminate cement), and the results are shown in Figure 5 ; the setting time tests are carried out, and the results are shown in Figure 6 ; the cumulative porosity tests are carried out, and the results are shown in Figure 7 ; the chloride ion binding rate tests are carried out, and the results are shown in Figure 8 . It can be seen that although comparative example 4 has good electrochemical extraction efficiency and higher porosity, its mechanical strength is lower, especially the 28d strength has a downward trend, and although the early setting time is improved, the final setting time does not change.

[0085] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. 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 product comprises the following components in parts by weight: 690-700 parts cement, 1035-1050 parts sand and gravel, 12-15 parts carbon fiber, 13.8-14 parts dispersible latex powder, 276-280 parts water, 7-21 parts nano-alumina, and 2.1-2.8 parts water-reducing agent; wherein the cement comprises silicate cement and sulfoaluminate cement in a mass ratio of 3:7; the cement is silicate cement and sulfoaluminate cement of grade 42.5 or higher. The nano-alumina particles have a diameter of 20-30 nm and are added in the form of nano-alumina sol with a solid content of 20 wt%.

2. The conductive mortar according to claim 1, characterized in that, The sand and gravel particles have a diameter of less than 2 mm.

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

4. The conductive mortar according to claim 1, characterized in that, The dispersible latex powder is one or more of vinyl acetate / ethylene copolymer powder, vinyl acetate copolymer powder, and ethylene copolymer powder.

5. The conductive mortar according to claim 1, characterized in that, The water-reducing agent is a high-efficiency polycarboxylate water-reducing agent.

6. A method for preparing conductive mortar as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Mix cement, sand and gravel and carbon fiber evenly to obtain the first mixture; S2. Dispersible latex powder is added to water and dispersed evenly to obtain mixing water; S3. Add mixing water and nano alumina sol to the first mixture and stir evenly to obtain conductive mortar.

7. An application of the conductive mortar as described in any one of claims 1-5, characterized in that, This includes an electrochemical dechlorination method for preparing conductive mortar anodes and applying them to reinforced concrete, comprising the following steps: S4. Apply the conductive mortar directly to the surface of reinforced concrete to obtain a conductive mortar anode; S5. The positive electrode is connected to the conductive mortar anode, and the negative electrode is connected to the reinforcing steel bars in the reinforced concrete, with a current of 0.5~5 A / m. 2 power ups.

8. The application of the conductive mortar according to claim 7, characterized in that, In S4, the thickness of the conductive mortar anode is 10~20 mm.

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