CN112521076B - Iron tailing high-slump high-strength conductive concrete and preparation method thereof - Google Patents
Iron tailing high-slump high-strength conductive concrete and preparation method thereof Download PDFInfo
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Abstract
The invention discloses iron tailing high-slump high-strength conductive concrete and a preparation method thereof, and belongs to the technical field of building material concrete. The conductive concrete comprises the following components in percentage by mass: 250 to 450 portions of cement, 1050 to 1180 portions of coarse aggregate, 720 to 960 portions of fine aggregate, 70 to 150 portions of admixture, 25.6 to 60.0 portions of expanding agent, 1.6 to 6.0 portions of water dispersant, 4.8 to 10.8 portions of polycarboxylic acid water reducing agent and 170 to 175 portions of water, wherein the unit is kg/m < 3 >. By adopting the technical scheme of the invention, the requirements of the conductive concrete on mechanical property, working performance and conductive performance can be effectively met.
Description
Technical Field
The invention belongs to the technical field of building material concrete, and particularly relates to iron tailing high-slump high-strength conductive concrete and a preparation method thereof.
Background
The concrete is widely applied to the field of civil engineering due to the excellent physical and mechanical properties thereof, and is a building material with the largest consumption at present. The resistivity of the common concrete is high, and the resistivity is generally 10 6 ～10 9 In the range of omega cm, belongs to poor electric conductors. For alternating current, dry concrete is a good insulator with a resistivity of about 10 13 Omega cm. However, as the moisture in the concrete increases, the resistivity of the concrete decreases. When the concrete is fully saturated with water, the resistivity of the concrete can be reduced to 10 2 ～10 3 Omega cm. So ordinary concrete is a material interposed between the insulator and the conductor. If a certain amount of conductive component material is added into the common concrete, the conductivity of the concrete can be greatly improved, thereby forming the concrete with better conductivityAn electrical conductor. The conductive concrete is a novel special functional concrete, has the characteristics of structural materials and conductivity, the resistivity of the conductive concrete depends on the type, performance and doping amount of the conductive material, and the conductive concrete has heat and electricity sensing and converting capabilities and is an intelligent material. The conductive concrete has the characteristics of wide material source, simple preparation, economy and the like, and the resistivity is different according to the application and can be generally changed to 10 -1 ～10 4 Omega cm, which not only makes the conductive concrete used as a structural material, but also plays an important role in electricians, electromagnetic interference shielding, industrial anti-static electricity, power equipment grounding engineering, electric heaters, reinforcing steel bar cathode protection, building ground heating, pavement deicing and snow melting, and the like, with the development of scientific technology, the heat-insulation material can be widely applied to the fields of structural engineering, electrical engineering, family heating and the like in future.
The conductive concrete can be used as structural concrete or mixed with conventional concrete. The conductive concrete is lighter than the conventional concrete, and the mass of the conductive concrete is 70% of that of the conventional concrete, but the thermal stability of the conductive concrete is not inferior to that of the conventional concrete at all; the conductive concrete is manufactured by a process which only requires conventional mixing and pouring equipment and is used in a manner substantially similar to conventional concrete. The conductive concrete is mainly conductive by means of mutual contact of conductive materials, the materials which can be used as the aggregate of the conductive concrete at present are mainly carbon materials, and the aggregate of the carbon materials mainly comprises graphite aggregate, carbon black, carbon lightweight aggregate, carbon fiber and the like. It is generally necessary to process a conductive phase material such as a carbonaceous aggregate to prepare a fine aggregate having a predetermined shape, particle size and gradation in place of the fine aggregate in concrete. The ideal gradation of the fine aggregate must be determined by testing, and the amount of incorporation is determined by the desired conductivity. The resistivity of the conductive concrete depends on the electrical properties of the conductive phase, the physical properties, the interaction of the conductive phase with the cementitious material, its distribution characteristics in the concrete, etc. As for the conductive materials such as granular and powdery graphite powder, carbon powder, coke, steel scraps and the like, the conductive materials are poor in conductivity because the length-diameter ratio is small, and when the doping amount is small, the conductive materials are difficult to contact with each other and cannot form a good conductive network; when the mixing amount is large, on one hand, the strength of carbon black, coke and the like is low, and on the other hand, the water requirement for mixing concrete is increased due to the large water absorption of the conductive material, so that the strength of the concrete is greatly reduced, the slump of the concrete is small, the fluidity of the concrete is poor, and the requirement of civil engineering on the mechanical property is difficult to meet. In the conductive concrete, other carbonaceous materials than the carbon fiber conductive concrete have an adverse effect on the strength of the concrete. The carbon fiber conductive concrete has the problems that on one hand, the price is high, on the other hand, when the carbon fiber content is high, the carbon fiber is easy to agglomerate due to uneven stirring, and a large amount of bubbles are easy to introduce during forming, so that the strength of the concrete is reduced; and it usually requires the use of dispersants and defoamers during the manufacturing process. And for the steel fiber conductive phase, the particle size is thick, when the fiber yield is low, a conductive network which is mutually overlapped is difficult to form, and the conductivity is poor. However, when the fiber content is too high, the workability of concrete is poor, and the construction is difficult by adopting conventional large-slump pumping. Therefore, the currently studied conductive concrete is difficult to satisfy the requirements of mechanical property, working property and conductivity.
The types of iron ores in China are various, and the most important iron ores comprise magnetite, hematite, limonite, siderite and the like. Iron ore is usually divided into rich ore (the iron content is higher than 50%) and lean ore (the iron content is lower than 45% -50%) according to the iron content, and magnetite has the chemical formula of Fe3O4, has compact structure, high hardness, good wear resistance and good electric conductivity and heat conductivity, and can be used for preparing concrete. Related patents on the preparation of concrete using iron ore have been disclosed. For example, the invention patent with Chinese patent application number 200910021287.5 discloses a conductive concrete doped with a conductive material, which comprises the following components in percentage by weight: 15-30% of cement, 15-30% of iron ore, 15-25% of graphite, 15-30% of pebbles and 10-20% of water. For another example, an invention patent with chinese patent application No. 201510907994.X discloses a conductive concrete, which comprises the following components in parts by weight: 150-180 parts of aluminate cement clinker, 35-45 parts of iron ore, 40-55 parts of steel slag aggregate, 50-60 parts of hot gypsum, 40-60 parts of silica fume, 30-40 parts of carbon fiber, 25-45 parts of carbon nano material, 15-25 parts of nano zinc oxide, 15-20 parts of concrete water reducer, 15-20 parts of filler, 5-10 parts of nano carbon black dispersing agent, 8-12 parts of defoaming agent, 40-60 parts of cementing material, 25-45 parts of desulfurized gypsum and 100-150 parts of water. For another example, the invention patent with the chinese patent application number of 201610558911.5 discloses a concrete produced by using talar tailing, which is prepared from the following raw materials in parts by weight: 278-328 parts of talar mountain tail ore sand, 1124-1354 parts of talar mountain tail ore material, 298-384 parts of carbon fiber-containing cement, 121-186 parts of fly ash, 214-261 parts of high-alumina cement, 91-154 parts of graphite, 10-12 parts of an additive, 124-184 parts of water, 50-95 parts of ferrite powder and 25-61 parts of conductive flakes. Although iron ore is adopted in the preparation of concrete in the above patents, the iron ore is generally raw ore, not tailings, and the tailings are solid wastes of the raw ore after the procedures of crushing, grinding, magnetic separation, flotation, gravity separation and the like; in addition, the patent inevitably needs to add carbonaceous conductive materials such as graphite in the concrete preparation process to ensure the conductivity of the obtained concrete, thereby influencing the strength and slump of the concrete.
Disclosure of Invention
1. Problems to be solved
The invention aims to overcome the defect that the conventional prepared conductive concrete is difficult to better meet the requirements of mechanical property, working property and conductive property of the conductive concrete, and provides the iron tailing high-slump high-strength conductive concrete and the preparation method thereof. By adopting the technical scheme of the invention, the problems can be effectively solved, and the requirements of the conductive concrete on mechanical property, working performance and conductive performance are met.
2. Technical scheme
In order to solve the problems, the technical scheme adopted by the invention is as follows:
the invention relates to iron tailing large-slump high-strength conductive concrete which comprises the following components in parts by mass:
wherein the unit is kg/m3.
Furthermore, the single-component mass of the iron tailing sand and the iron concentrate powder in the fine aggregate is
570-740 iron tailing sand
150 to 220 percent of fine iron powder,
wherein the unit is kg/m3.
Furthermore, the iron content of the iron ore waste stone is 15-25%, and the particle size of the iron ore waste stone is 5-25 mm; the iron content of the iron tailing sand is 10-20%, and the fineness modulus is 1.2-2.0; the iron content of the fine iron powder is 50-68%, and the fineness particle is 60-200 meshes.
Furthermore, the admixture comprises silica fume and fly ash, and the single mass of the silica fume and the fly ash is
30 to 60 portions of silica fume
40 to 90 portions of fly ash,
wherein the unit is kg/m3.
Furthermore, the high-strength conductive concrete further comprises a conductive accelerator, an expanding agent, a water-based dispersant, a polycarboxylic acid water reducing agent and water, and the single components are as follows by mass:
wherein the unit is kg/m3.
Furthermore, the mixing amount of the polycarboxylate superplasticizer solution is 1.5-1.8% of the using amount of the cementing material.
Furthermore, the conductive accelerant is sodium nitrite solid, and the doping amount of the conductive accelerant is 1-2% of the using amount of the cementing material.
Furthermore, the water-based dispersant is polynaphthalenesulfonate PNS solution, and the mixing amount of the water-based dispersant is 0.5-1.0% of the using amount of the cementing material.
Furthermore, the mixing amount of the solid expanding agent is 7.7-10% of the using amount of the cementing material.
The preparation method of the iron tailing high-slump high-strength conductive concrete comprises the following steps:
step one, weighing the raw material components according to the following single formula by mass: 250 to 450 portions of cement, 30 to 60 portions of silica fume, 40 to 90 portions of fly ash, 1050 to 1180 portions of iron ore waste stone, 570 to 740 portions of iron tailing sand, 150 to 220 portions of fine iron powder, 3.2 to 12.0 portions of conductive accelerant, 25.6 to 60.0 portions of expanding agent, 1.6 to 6.0 portions of aqueous dispersant, 4.8 to 10.8 portions of polycarboxylic acid water reducing agent and 170 to 175 portions of water, wherein the unit is kg/m < 3 >;
step two, adding the weighed conductive promoter, the weighed water-based dispersant and the weighed polycarboxylic acid water reducer into water and uniformly stirring;
step three, sequentially adding the weighed iron ore waste stone, iron tailing sand, iron concentrate powder, cement, silica fume, fly ash and expanding agent into a stirrer and stirring for 1min;
and step four, adding the solution obtained by stirring in the step two into a stirrer, and stirring for 2min to obtain the required working performance, thereby finally obtaining the high-strength conductive concrete.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) According to the iron tailing high-slump high-strength conductive concrete, magnetic iron ore is adopted to replace carbonaceous aggregates such as graphite, so that the conductivity of the concrete can be effectively improved, the carbonaceous aggregates such as graphite do not need to be added, and the influence of the addition of the carbonaceous aggregates on the strength of the concrete is avoided. Meanwhile, the iron tailing aggregate has low water absorption, the concrete has high fluidity and high slump, the performance of pumping construction can be met, and the requirements of the conductive concrete on mechanical property, working performance and conductivity are met.
(2) According to the iron tailing high-slump high-strength conductive concrete, the special aggregate is adopted to prepare the conductive concrete, the aggregate is preferably selected, iron ore waste stones are used as coarse aggregate, iron tailing sand and fine iron powder are used as fine aggregate, and the particle size grading is optimally designed, so that the particle grading is excellent, the conductivity of the concrete is effectively guaranteed, the mechanical property and the working performance of the concrete are considered, and the high strength and high slump performance of the concrete are guaranteed.
(3) According to the iron tailing high-slump high-strength conductive concrete, the mass ratio of each component in the conductive concrete is optimally designed, so that on one hand, the iron tailing aggregate in the concrete accounts for a large proportion, and the conductive materials are closely contacted with each other, so that a good conductive network can be formed, the resistivity is stable, and the conductivity of the concrete is good; on the other hand, under the condition of not reducing the conductivity of the concrete, the slump of the concrete can be further increased, the working performance of the concrete can be improved, the high-strength and large-slump pumping performance can be better met, and the requirements of mechanical property, working performance and conductivity can be further met.
(4) According to the iron tailing high-slump high-strength conductive concrete, the iron tailings are adopted to replace natural sandstone aggregates, so that solid waste is utilized, the production cost is reduced, and the economic benefit is remarkable; meanwhile, the iron tailing waste material is combined with large-scale concrete production, so that large-scale consumption of the iron tailings is realized, waste is changed into valuable, and the social benefit is remarkable.
(5) The high-slump high-strength conductive concrete of the iron tailings has the resistivity of 1-10 3 Omega cm, the compression strength can reach C30-C60, the slump constant is 180-240 mm, the volume weight of the high-strength conductive concrete is 2600-2750 kg/m < 3 >, the high-strength conductive concrete not only can be used as a structural material, but also can play an important role in electricians, electromagnetic interference shielding, industrial anti-static electricity, power equipment grounding engineering, electric heaters, reinforcing steel bar cathode protection, building ground heating, pavement deicing and snow melting and the like.
Drawings
FIG. 1 is a schematic block diagram of the four-electrode resistivity measurement of conductive concrete of the present invention;
FIG. 2 is a schematic view showing the mixing ratios of the components of the conductive concretes of examples 1 to 4 and comparative examples 1 to 4;
FIG. 3 is a graph showing basic performance test results of the conductive concretes of examples 1 to 4 and comparative examples 1 to 4;
FIG. 4 is a graph showing a comparison of the 28-day compressive strengths of the conductive concretes of examples 1 to 4 and comparative examples 1 to 4;
FIG. 5 is a comparison of 28-day flexural strengths of the conductive concretes of examples 1 to 4 and comparative examples 1 to 4;
FIG. 6 is a graph showing a comparison of the resistivity of the electrically conductive concrete of examples 1 to 4 and comparative examples 1 to 4.
Detailed Description
At present, the traditional conductive concrete is usually prepared by adopting main conductive materials such as graphite, carbon and the like, and as the length-diameter ratio of the conductive materials such as granular and powdery graphite powder, carbon powder, coke, steel scraps and the like is small, when the mixing amount is small, the conductive materials are difficult to contact with each other and cannot form a good conductive network, so the conductivity is poor; when the mixing amount is large, on one hand, the strength of carbon black, coke and the like is low, and on the other hand, the water requirement for concrete mixing is increased due to the large water absorption of the conductive material, so that the strength of the concrete is greatly reduced, the slump of the concrete is small, the fluidity of the concrete is poor, and the requirements on the mechanical property, the working property and the conductive property of the conductive concrete are difficult to meet.
Aiming at the problems, the invention provides iron tailing high-slump high-strength conductive concrete, which is prepared by adopting magnetic iron ore to replace natural sandstone aggregate, magnetite coarse aggregate and magnetite fine aggregate are added, the iron tailing aggregate has small water absorption, the prepared concrete has good fluidity and high slump, can meet the performance of pumping construction, and effectively solves the problems that the prior conductive materials such as graphite, carbon and the like have large water absorption, the concrete needs more water for mixing, is agglomerated during stirring, has poor working performance and cannot meet the conventional high-slump pumping construction; in addition, the adopted iron ore aggregate has compact structure, high hardness, good wear resistance, good electric conductivity and heat conductivity, and good concrete strength, effectively overcomes the problems that the prior graphite and carbon conductive materials have poor adhesive force with cement paste, a large amount of air bubbles are easily introduced during molding, and the strength of the concrete is reduced to different degrees, and meets the requirements of the mechanical property, the working property and the electric conductivity of the conductive concrete.
The invention optimizes the used aggregate, uses the iron ore waste stone as the coarse aggregate, uses the iron ore waste stone as the stripped surrounding rock in the mining process, uses the iron tailing sand and the iron concentrate as the fine aggregate, uses the waste slag generated after the iron ore is ground and magnetically separated, uses the concentrate powder after the iron ore is ground and magnetically separated, and has better concrete conductivity compared with the traditional method of directly using the raw ore. Meanwhile, substances such as a water-based dispersant and a polycarboxylic acid water reducing agent are added into the conductive concrete, and the water-based dispersant is doped into the formula, so that the materials can be uniformly dispersed during stirring, and the agglomeration phenomenon is further avoided; in addition, soluble substances of sulfate and sulfide in the aggregate can react with hydration products of cement, so that the cement has an erosion effect, and the concrete volume expansion can cause internal stress and influence the concrete strength, so that the sulfur content is strictly controlled, and the iron tailing aggregate has low sulfur content, so that the adverse effect can be effectively avoided. The mass ratio of all the components added is optimized, and by controlling the adding proportion of cement, aggregate and other substances, on one hand, most of the concrete is iron tailing aggregate, the proportion of the iron tailing aggregate is large, and the conductive materials are closely contacted with each other, so that a good conductive network can be formed, the resistivity is stable, and the conductivity of the concrete is effectively ensured; on the other hand, through the comprehensive action of the iron tailing aggregate and the polycarboxylic acid water reducing agent, the slump of the concrete can be further increased under the condition of not reducing the conductivity of the concrete, the working performance of the concrete is improved, the high-strength and high-slump pumping performance is better met, and the requirements of considering the mechanical property, the working performance and the conductivity are further met.
The invention adopts the iron tailings to replace natural sandstone aggregates, so that the solid waste is utilized, the production cost is reduced, the defect that the conventional main conductive materials such as conductive concrete graphite, carbon fiber and the like are expensive is overcome, and the economic benefit is remarkable; meanwhile, the waste iron tailing materials are combined with large-scale concrete production, so that large-scale consumption of the iron tailings is realized, waste is turned into wealth, and the method has important significance for protecting limited mineral resources, promoting economic development and protecting human environment and has remarkable social benefit. The resistivity of the prepared high-strength conductive concrete is 1 to 10 3 Omega cm, the compression strength grade can reach C30-C60, the slump is 180-240 mm, the volume weight of the high-strength conductive concrete is 2600-2750 kg/m < 3 >, the high-strength conductive concrete not only can be used as a structural material, but also can play an important role in the aspects of electricians, electromagnetic interference shielding, industrial anti-static electricity, power equipment grounding engineering, electric heaters, reinforcing steel bar cathode protection, building ground heating, pavement deicing and snow melting, and the like.
Specifically, the iron tailing high-slump high-strength conductive concrete comprises the components of cement, an admixture, aggregate, a conductive accelerator, an expanding agent, a water-based dispersing agent, a polycarboxylic acid water reducing agent and water. The cement and the admixture are cementing materials, the aggregate is iron tailings, the iron tailings mainly adopt magnetite ore, the aggregate is magnetite coarse aggregate and magnetite fine aggregate, the coarse aggregate is iron ore waste stone, and the fine aggregate is iron tailing sand and fine iron powder after levigating and magnetic separation. The admixture comprises silica fume and fly ash. The unilateral mass ratio (unit is kg/m < 3 >) of each component in the high-strength conductive concrete is as follows:
the magnetite coarse aggregate adopts iron ore waste rock, namely surrounding rock stripped in the mining process, the iron content of the magnetite coarse aggregate is 15-25%, the particle size of the magnetite coarse aggregate is 5-25 mm, the crushing value is less than or equal to 12%, the needle flake content is less than or equal to 15%, and the sulfide and sulfate content is less than or equal to 1.0%. The iron tailing fine aggregate comprises two types, one type is iron tailing sand, namely waste residue generated after iron ore is ground and magnetically separated, the iron content is 10-20%, the fineness modulus is 1.2-2.0, the content of stone powder is less than or equal to 10%, and sulfide and sulfate are less than or equal to 0.5%; the other is iron concentrate powder, namely concentrate powder obtained by finely grinding and magnetically separating iron ore, wherein the iron content is 50-68%, the fineness particles are 60-200 meshes, and the S% is less than 0.050%.
The cement is conch cement with the strength grade of 42.5. SiO in the silica fume 2 Content (wt.)>90 percent and the specific surface area is 18000m 2 In terms of/kg. The fly ash is I-grade ash, the fineness of the fly ash is less than or equal to 12 percent, and the loss on ignition of the fly ash is less than or equal to 5 percent. The conductive accelerant adopts white powdery sodium nitrite, and the doping amount of the white powdery sodium nitrite is 1-2%, preferably 2% of the using amount of the cementing material. The water-based dispersant is polynaphthalene sulfonate PNS solution, is a condensation product of beta-sulfonate and formaldehyde, and the dosage of the water-based dispersant is 0.5-1.0% of the dosage of the cementing material. The mixing amount of the solid expanding agent is 7.7-10% of the using amount of the cementing material, the expansion rate is limited, 7d in water is more than or equal to 0.025%, and 21d in air is more than or equal to-0.020%. The mixing amount of the polycarboxylic acid water reducing agent solution is 1.5 to 1.8 percent of the using amount of the cementing material, and the water reducing rate reaches 22 percent.
The preparation method of the iron tailing high-slump high-strength conductive concrete comprises the following steps:
step one, weighing the raw material components according to the following single formula by mass: 250 to 450 parts of cement, 30 to 60 parts of silica fume, 40 to 90 parts of fly ash, 1050 to 1180 parts of iron ore waste stone, 570 to 740 parts of iron tailing sand, 150 to 220 parts of fine iron powder, 3.2 to 12.0 parts of conductive promoter, 25.6 to 60.0 parts of expanding agent, 1.6 to 6.0 parts of aqueous dispersant, 4.8 to 10.8 parts of polycarboxylic acid water reducing agent and 170 to 175 parts of water, wherein the unit is kg/m < 3 >.
Step two, adding the weighed conductive promoter, the weighed water-based dispersant and the weighed polycarboxylic acid water reducer into water and uniformly stirring;
step three, sequentially adding the weighed iron ore waste stone, iron tailing sand, iron concentrate powder, cement, silica fume, fly ash and expanding agent into a stirrer and stirring for 1min;
and step four, adding the solution containing the conductive accelerator, the water-based dispersant and the polycarboxylic acid water reducer obtained by stirring in the step two into a stirrer, and stirring for 2min to obtain the required working performance, thereby finally obtaining the high-strength conductive concrete.
When the high-strength conductive concrete is prepared, the design of the conductivity needs to be developed on the premise of fixing the design strength as other concrete. The concrete preparation strength calculation method is clearly specified by industrial standards or specifications such as JGJ 55-2011 'design rule for general concrete mix proportion' and DL/T5330-2005 'design rule for hydraulic concrete mix proportion' in China.
1.1 calculation method of preparation strength of conductive concrete
When the design strength of the conductive concrete is less than C60, the formulation strength of the conductive concrete is calculated according to the formula (1):
f cu,o ≥f cu,k +1.645σ (1)
in the formula (f) cu,o Preparing strength for the conductive concrete, wherein the unit is MPa; f. of cu,k The unit is the design strength of the conductive concrete, and is MPa; and sigma is the standard difference of the strength of the conductive concrete.
1.2 determination of standard difference sigma of strength of conductive concrete
Counting the compressive strength data of more than or equal to 30 groups of the same conductive concrete for 1-3 months, and calculating sigma according to the formula (2):
in the formula, sigma is the standard difference of the strength of the conductive concrete; f. of cu,i The strength of the i group of conductive concrete test pieces is in MPa; m is a unit of fcu The average value of the compressive strength of n groups of conductive concrete test pieces is expressed in MPa; n is the number of specimen sets.
In addition, when the design strength is less than or equal to C30, if the standard deviation is less than 3.OMPa calculated by formula (2), 3.0MPa should be taken; when the design strength is C30-C60, if the calculated value of the standard deviation through the formula (2) is less than 4.0MPa, 4.OMPa is adopted.
In addition, after the high-strength conductive concrete is prepared, the resistivity of the conductive concrete can be measured, and the four-electrode method can be adopted as the measuring method in comprehensive consideration. The four-electrode method is shown in figure 1, and comprises embedding four parallel electrodes with equal spacing in a test block, injecting current between two outer electrodes via DC voltage source, measuring accurate current value I, measuring voltage value U between two inner electrodes, and measuring resistance value of the test block between the two inner electrodes according to ohm's law
R＝U/I (3)
According to the measured R, the distance L between the two inner electrodes and the cross-sectional area S of the test block are measured and calculated, and the resistivity value is
ρ＝RS/L (4)
Wherein S is the sectional area of the conductive concrete slab, and L is the distance between the two middle electrodes. For comparison purposes, the present invention prepares 8 conductive concrete slabs, specifically 70cm x 10cm x 5cm in length, width and height. Firstly, a mould with specific corresponding specification is manufactured, and 8 conductive concrete plates are respectively marked. Because the resistivity is measured by adopting a four-electrode method, 4 copper electrodes are arranged at the positions shown in figure 1 during pouring. And watering the template regularly after pouring is finished, so as to prevent excessive evaporation of water from influencing the mechanical property and the conductivity of the conductive concrete until the template is completely shaped. After the template is completely shaped, the resistance and resistivity of the template can be tested. After several attempts, the resistance of each plate is measured by adopting a classical voltammetry method, each plate is connected to obtain the corresponding values of voltage U and current I, the resistance value of each plate is calculated according to a formula (3), and then the resistivity is calculated according to a formula (4).
The invention is further described with reference to specific examples.
Example 1
The composition ratios of the conductive concrete of this example are shown in fig. 2. In fig. 2, (1) is iron ore waste; (2) limestone with particle size of 5-25 mm; (3) is iron tailing sand; (4) is fine iron powder; (5) is natural sand with fineness modulus of 1.8; (6) is carbon fiber, namely 6mm chopped carbon fiber filaments; (7) is graphite, namely natural crystalline flake graphite powder of 200 meshes; (8) is a swelling agent, namely UEA (U-shaped swelling agent); (9) is an antifoaming agent, namely tributyl phosphate. In the embodiment, the iron content of the iron ore waste rock is 20%, and the particle size of the iron ore waste rock is 20mm; the iron content of the iron tailing sand is 15 percent, and the fineness modulus is 2.0; the iron content of the fine iron powder is 60 percent, and the fineness particles are 100 meshes.
The basic properties of the electrically conductive concrete prepared in this example are shown in FIG. 3.
Example 2
The composition ratios of the conductive concrete of this example are shown in fig. 2. In the embodiment, the iron content of the iron ore waste stone is 15%, and the particle size of the iron ore waste stone is 25mm; the iron content of the iron tailing sand is 10 percent, and the fineness modulus is 1.8; the iron content of the fine iron powder is 50 percent, and the fineness particles are 200 meshes.
The basic properties of the electrically conductive concrete prepared in this example are shown in FIG. 3.
Example 3
The composition ratios of the conductive concrete of the present example are shown in fig. 2. In the embodiment, the iron content of the iron ore waste rock is 25%, and the particle size of the iron ore waste rock is 5mm; the iron content of the iron tailing sand is 20 percent, and the fineness modulus is 1.2; the iron content of the fine iron powder is 68 percent, and the fineness particles are 60 meshes.
The basic properties of the conductive concrete prepared in this example are shown in fig. 3.
Example 4
The composition ratios of the conductive concrete of this example are shown in FIG. 2 (unit kg/m 3). In the embodiment, the iron content of the iron ore waste rock is 20%, and the particle size of the iron ore waste rock is 16mm; the iron content of the iron tailing sand is 16 percent, and the fineness modulus is 1.5; the iron content of the fine iron powder is 60 percent, and the fineness particles are 100 meshes.
The basic properties of the electrically conductive concrete prepared in this example are shown in FIG. 3.
Example 5
The mixing ratio (unit is kg/m 3) of each component of the conductive concrete in the embodiment is as follows: 450 parts of cement, 60 parts of silica fume, 90 parts of fly ash, 1180 parts of iron ore waste stone, 570 parts of iron tailing sand, 150 parts of fine iron powder, 12.0 parts of a conductive promoter, 60.0 parts of an expanding agent, 6.0 parts of an aqueous dispersant, 10.8 parts of a polycarboxylic acid water reducing agent and 170 parts of water. Wherein the iron content of the iron ore waste stone is 20%, and the particle size of the iron ore waste stone is 20mm; the iron content of the iron tailing sand is 15 percent, and the fineness modulus is 2.0; the iron content of the fine iron powder is 60 percent, and the fineness particle is 100 meshes. The conductive concrete is prepared according to the components.
Example 6
The mix ratio (unit is kg/m 3) of each component of the conductive concrete in the embodiment is as follows: 250 parts of cement, 30 parts of silica fume, 40 parts of fly ash, 1050 parts of iron ore waste stone, 740 parts of iron tailing sand, 220 parts of fine iron powder, 3.2 parts of a conduction promoter, 25.6 parts of an expanding agent, 1.6 parts of an aqueous dispersant, 4.8 parts of a polycarboxylic acid water reducing agent and 175 parts of water. Wherein the iron content of the iron ore waste stone is 15%, and the particle size of the iron ore waste stone is 25mm; the iron content of the iron tailing sand is 10 percent, and the fineness modulus is 1.8; the iron content of the fine iron powder is 50 percent, and the fineness particles are 200 meshes. The conductive concrete is prepared according to the components.
The invention also carries out 4-group comparison proportion, the concrete prepared by the comparative example has the components in the formula shown in figure 2, and the basic performance of the prepared conductive concrete is shown in figure 3. A comparison of 28-day compressive strengths of the conductive concretes prepared in examples 1 to 4 and comparative examples 1 to 4 is shown in FIG. 4, and a comparison of 28-day flexural strengths thereof is shown in FIG. 5. Compared with comparative examples 1 to 4, examples 1 to 4 are the same as concrete gelled materials of the comparative examples in fig. 2, and comparative examples 1 to 4 are obtained by adding graphite and carbon fiber conductive materials on the basis of conventional concrete, so that on one hand, carbon black has low strength, on the other hand, water requirement for concrete mixing is increased due to water absorption of the conductive materials, carbon fibers are agglomerated and bundled during stirring and are difficult to disperse, a large amount of bubbles are easily introduced during molding, and the concrete strength is reduced, as shown in fig. 3, concrete mixtures in the comparative examples have poor dryness, cohesiveness and fluidity and slump of only 20-30 mm, and are difficult to meet the requirements of civil engineering on mechanical properties. In the embodiments 1 to 4, the iron tailings are adopted to completely replace natural sandstone aggregates, the adopted iron tailings have small water absorption, compact structure, high hardness, good wear resistance and excellent particle grading, as shown in fig. 3, the concrete in the embodiment has good fluidity and slump of 180-240 mm, and meets the performance of pumping construction. As can be seen from the figures 4 and 5, the compressive strength and the flexural strength of the iron tailing conductive concrete are far higher than those of graphite and carbonaceous conductive concrete which are made of the same cementing material, and the requirements of the strength grade of C30-C60 can be met.
Examples 1-4 comparative examples 1-4, and comparative examples 1-4 generally replace the fine aggregate in concrete by processing the conductive phase material as necessary to produce a fine aggregate of a certain shape, size and gradation. The ideal gradation of fine aggregate must be determined by experiment, and its content is determined by the desired conductivity. For the granular and powdery graphite powder conductive material, the length-diameter ratio is small, and when the doping amount is small, the conductive materials are difficult to contact with each other and cannot form a good conductive network, so the conductivity is poor; for carbon fiber, although a conductive network can be formed when the doping amount is low, the conductive performance is low because the lapping surface of the fiber is small. While the iron ores of the embodiments 1 to 4 have good electrical conductivity and heat conductivity, the coarse aggregate adopts iron tailing, the fine aggregate adopts iron tailing sand and fine iron powder, most of the concrete is made of conductive materials, the aggregate structure is compact, the conductive materials are tightly contacted with each other, a good conductive network can be formed, the resistivity is stable, and the conductivity is good. The schematic diagram of the comparison of the resistivity of the conductive concrete prepared in the examples 1 to 4 and the comparative examples 1 to 4 is shown in fig. 6, and it can be seen from fig. 6 that the resistivity of the iron tailing conductive concrete is smaller than that of the graphite and the carbonaceous conductive concrete, and the resistivity is 1 to 10 3 The requirement of the conductive performance of the conductive concrete can be met within the range of omega cm.
Claims (6)
1. The iron tailing high-slump high-strength conductive concrete is characterized in that: the conductive concrete is in a single mass kg/m 3 The composition consists of the following components: 250 to 450 portions of cement, 30 to 60 portions of silica fume, 40 to 90 portions of fly ash and 10 portions of iron ore waste stone50 to 1180 percent of iron tailing sand, 570 to 740 percent of iron tailing sand, 150 to 220 percent of fine iron powder, 3.2 to 12.0 percent of conductive accelerator, 25.6 to 60.0 percent of expanding agent, 1.6 to 6.0 percent of water dispersant, 4.8 to 10.8 percent of polycarboxylic acid water reducing agent and 170 to 175 percent of water; the particle size of the iron ore waste stone is 5-25 mm, the fineness modulus of the iron tailing sand is 1.2-2.0, and the particle fineness of the fine iron powder is 60-200 meshes; the iron tailing sand adopts waste residues generated after iron ore is levigated and magnetically separated, and the iron concentrate powder adopts concentrate powder obtained after the iron ore is levigated and magnetically separated; the iron content of the iron ore waste stone is 15-25%, the iron content of the iron tailing sand is 10-20%, and the iron content of the fine iron powder is 50-68%; the conductive accelerant is a sodium nitrite solid.
2. The iron tailing high-slump high-strength conductive concrete according to claim 1, which is characterized in that: the mixing amount of the polycarboxylate superplasticizer is 1.5-1.8% of the using amount of a cementing material, and the cementing material consists of cement, silica fume and fly ash.
3. The iron tailing high-slump high-strength conductive concrete according to claim 2, characterized in that: the mixing amount of the conductive accelerant is 1-2% of the using amount of the cementing material.
4. The iron tailing high-slump high-strength conductive concrete according to claim 3, which is characterized in that: the water-based dispersant is polynaphthalene sulfonate PNS solution, and the mixing amount of the water-based dispersant is 0.5-1.0% of the using amount of the cementing material.
5. The iron tailing high-slump high-strength conductive concrete according to claim 4, which is characterized in that: the mixing amount of the solid expanding agent is 7.7-10% of the using amount of the cementing material.
6. The preparation method of the iron tailings high-slump high-strength conductive concrete as claimed in any one of claims 1 to 5, which comprises the following steps:
step one, weighing the raw material components according to the following single formula by mass:250 to 450 portions of cement, 30 to 60 portions of silica fume, 40 to 90 portions of fly ash, 1050 to 1180 portions of iron ore waste stone, 570 to 740 portions of iron tailing sand, 150 to 220 portions of fine iron powder, 3.2 to 12.0 portions of conductive accelerant, 25.6 to 60.0 portions of expanding agent, 1.6 to 6.0 portions of aqueous dispersant, 4.8 to 10.8 portions of polycarboxylic acid water reducing agent and 170 to 175 portions of water, wherein the unit is kg/m 3 ；
Step two, adding the weighed conductive promoter, the weighed water-based dispersant and the weighed polycarboxylic acid water reducer into water and uniformly stirring;
step three, adding the weighed iron ore waste stone, iron tailing sand, iron concentrate powder, cement, silica fume, fly ash and expanding agent into a stirrer in sequence and stirring;
and step four, adding the solution obtained by stirring in the step two into the stirrer, and stirring to obtain the required working performance, thereby finally obtaining the high-strength conductive concrete.
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| US20200176977A1 (en) * | 2017-06-16 | 2020-06-04 | The Board Of Regents Of The University Of Nebraska | Systems and methods for electrical filter including a conductive concrete structure |
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