阅读说明：本技术 一种用于采暖的电热混凝土板材及其制备方法 (Electric heating concrete plate for heating and preparation method thereof ) 是由 王瑞 于 2020-12-09 设计创作，主要内容包括：本发明公开了一种用于采暖的电热混凝土板材,由以下重量份的原料制备而成：水泥100份；导热骨料100-300份；普通骨料-150份；导电材料5-15份；水25-55份；消泡剂0-4份；减水剂0.5-1份；早强剂0.5-1份；其中,所述早强剂为乙酸钙或甲酸钙中的至少一种。电热混凝土板材中添加导热骨料,提高其导热性能,并且能够改善板材受热不均的情况；乙酸钙和甲酸钙作为一种早强剂,不仅可以提高浇筑的电热板材的早期强度,并且可以一定程度降低板材的电阻率,从而降低导电材料的用量,降低生产成本。(The invention discloses an electric heating concrete plate for heating, which is prepared from the following raw materials in parts by weight: 100 parts of cement; 100 portions and 300 portions of heat-conducting aggregate; 150 parts of common aggregate; 5-15 parts of a conductive material; 25-55 parts of water; 0-4 parts of a defoaming agent; 0.5-1 part of water reducing agent; 0.5-1 part of early strength agent; wherein the early strength agent is at least one of calcium acetate or calcium formate. The heat-conducting aggregate is added into the electric heating concrete plate, so that the heat-conducting property of the electric heating concrete plate is improved, and the condition that the plate is heated unevenly can be improved; the calcium acetate and the calcium formate are used as early strength agents, so that the early strength of the poured electric heating plate can be improved, and the resistivity of the plate can be reduced to a certain extent, so that the using amount of the conductive material is reduced, and the production cost is reduced.)

1. The electric heating concrete plate for heating is characterized by being prepared from the following raw materials in parts by weight:

wherein the early strength agent is at least one of calcium acetate or calcium formate.

2. The electric heating concrete panel for heating according to claim 1, wherein the heat conductive aggregate includes at least one of corundum, silicon carbide, silicon oxide and iron oxide.

3. The electrically heated concrete panel for heating according to claim 1, wherein the electrically conductive material includes at least one of graphene, carbon black, carbon fiber, carbon nanotube and graphite.

4. The electric heating concrete plate for heating according to claim 1, wherein the heat conducting aggregate is formed by mixing corundum and carborundum according to the mass ratio of 1: 0.5-1.5; the content of alumina in the corundum is more than 85 percent; the content of silicon carbide in the carborundum is more than 85 percent.

5. An electrically heated concrete panel for heating as claimed in claim 1 wherein said cement includes one of portland cement, aluminate cement, sulphoaluminate cement, ferro-aluminate cement, fluoroaluminate cement, phosphate cement and sulphate cement.

6. An electric heating concrete panel for heating according to claim 1 or 5, wherein the cement has a sand-lime ratio of 1: 1.5-1: 3.5.

7. the electric heating concrete panel for heating according to claim 1, wherein the thermal conductive aggregate has a particle size of 0.1-10 mm.

8. The electric heating concrete panel for heating according to claim 1, wherein the general aggregate comprises sand and crushed stone, and the particle size of the sand is 0.15-1.5 mm; the particle size of the crushed stone is 1-10 mm.

9. The method for preparing an electric heating concrete panel for heating according to any one of claims 1 to 8, comprising the steps of:

s1: adding a conductive material and water into a stirring tank, starting stirring, and uniformly dispersing the conductive material in the water to obtain conductive slurry;

s2: uniformly mixing cement, heat-conducting aggregate, common aggregate, an early strength agent, a water reducing agent and a defoaming agent in proportion to obtain mixed powder;

s3: adding the mixed powder obtained in the step S2 into a stirring tank in the step S1, and uniformly stirring to obtain conductive concrete mortar;

s4: and (4) pouring the conductive concrete mortar obtained in the step (S3) into a mold with electrodes at two ends, and maintaining for 28 days in a humid environment at room temperature to obtain the electric heating concrete plate with the electrodes at two ends and the thickness of not more than 10 mm.

Technical Field

The invention relates to the technical field of conductive concrete, in particular to an electric heating concrete plate for heating and a preparation method thereof.

Background

The conductive concrete slab is a research hotspot of indoor heating as a novel building material with good electric heating performance. Ordinary ground ceramic tile or wear-resisting waterproof plastics plastic of self-adhesion are laid on electrically conductive concrete slab, make it as an organic whole, and then spread it on the ground, and supreme transmission is from down followed to the heat, builds more comfortable environment, and the tiling on surface can play waterproof effect, can play the effect of protection against electric shock again. The heating mode has the advantages of convenient construction, low cost and convenient maintenance, and only needs to maintain or replace the plate at the fault position if the fault occurs. Moreover, the temperature control switch is connected with accessories such as a temperature control switch and the like, so that the indoor temperature and the ground temperature can be controlled simultaneously.

The electric heating concrete plate is a functional plate formed by mixing a conductive medium into concrete mortar, stirring and dispersing the mixture to form the concrete mortar with a conductive function, pouring the conductive concrete mortar into a specific mould and curing the concrete mortar, and can efficiently convert electric energy into heat energy and release the heat energy into an external space in the electrifying process.

At present, the following problems of the electric heating concrete plate still need to be solved: the existing conductive concrete slab is mostly a thick plate of about 50mm, and when the thick plate is used for indoor heating, the indoor clear height can be reduced, and the floor load is increased; after the thickness of the conductive concrete plate is thinned, the phenomenon of uneven heating can occur in the electrifying process.

Disclosure of Invention

The invention aims to provide an electric heating concrete plate for heating and a preparation method thereof, which are used for solving the problems in the background technology and ensuring that the plate is uniformly heated while the thickness of the plate is reduced.

In order to achieve the purpose, the invention provides the following technical scheme:

an electric heating concrete plate for heating is prepared from the following raw materials in parts by weight:

wherein the early strength agent is at least one of calcium acetate or calcium formate.

As a further scheme of the invention: the heat conducting aggregate comprises at least one of corundum, carborundum, silicon oxide and ferric oxide.

As a further scheme of the invention: the conductive material includes at least one of graphene, carbon black, carbon fiber, carbon nanotube, and graphite.

As a further scheme of the invention: the heat-conducting aggregate is formed by mixing corundum and carborundum according to the mass ratio of 1: 0.5-1.5; the content of alumina in the corundum is more than 85 percent; the content of silicon carbide in the carborundum is more than 85 percent.

As a further scheme of the invention: the cement comprises one of portland cement, aluminate cement, sulphoaluminate cement, ferro-aluminate cement, fluoroaluminate cement, phosphate cement and sulfate cement.

As a further scheme of the invention: the cement has a sand-lime ratio of 1: 1.5-1: 3.5.

as a further scheme of the invention: the particle size of the heat-conducting aggregate is 0.1-10 mm.

As a further scheme of the invention: the common aggregate comprises sand and broken stone, and the particle size of the sand is 0.15-1.5 mm; the particle size of the crushed stone is 1-10 mm.

As a further scheme of the invention: a preparation method of an electric heating concrete plate for heating comprises the following steps:

s1: adding a conductive material and water into a stirring tank, starting stirring, and uniformly dispersing the conductive material in the water to obtain conductive slurry;

s2: uniformly mixing cement, heat-conducting aggregate, common aggregate, an early strength agent, a water reducing agent and a defoaming agent in proportion to obtain mixed powder;

s3: adding the mixed powder obtained in the step S2 into a stirring tank in the step S1, and uniformly stirring to obtain conductive concrete mortar;

s4: and (4) pouring the conductive concrete mortar obtained in the step (S3) into a mold with electrodes at two ends, and maintaining for 28 days in a humid environment at room temperature to obtain the electric heating concrete plate with the electrodes at two ends and the thickness of not more than 10 mm.

Compared with the prior art, the invention has the beneficial effects that: the heat conducting aggregate is added into the electric heating concrete plate, so that the heat conducting performance of the electric heating concrete plate can be improved, and the condition that the plate is heated unevenly can be improved; the heat-conducting aggregate has stable physical properties and good durability, greatly improves the heat conduction rate of the electric heating concrete plate, further accelerates the heat conduction and the heat dissipation, and improves the use effect of the electric heating concrete plate in the heating process; calcium acetate and calcium formate are used as an early strength agent, so that the early strength of the poured electric heating plate can be improved, and the resistivity of the plate can be reduced to a certain extent, so that the using amount of conductive materials such as graphene and graphite is reduced, and the production cost is reduced; the thickness of the electric heating concrete plate is not more than 10mm, the floor load is reduced, and the indoor occupancy net height is reduced; the electric heating concrete plate prepared by the invention has the resistivity of 100-1800 omega-cm, large adjustable range of the resistivity and wide application range, and can meet different requirements of the heating industry.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to specific embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without any creative effort, shall fall within the protection scope of the present invention.

The invention discloses an electric heating concrete plate for heating in a first aspect, which comprises the following raw materials in parts by weight:

wherein the early strength agent is at least one of calcium acetate or calcium formate. The calcium acetate and the calcium formate as the early strength agents can improve the early strength of the poured electric heating concrete plate and reduce the resistivity of the plate to a certain degree, so that the using amount of conductive materials such as graphene and graphite is reduced, and the production cost is reduced.

The water reducing agent is a wide-spread type on the market, a polycarboxylic acid type water reducing agent or a naphthalene type water reducing agent can be selected, the water reducing agent has the functions of improving the fluidity of the slurry and adjusting the water-cement ratio of the concrete, and the defoaming agent has the function of eliminating bubbles generated in the stirring process of the conductive slurry, so that the strength of a concrete product can be improved, and the resistivity of the concrete product can also be improved.

The heat conducting aggregate comprises at least one of corundum, carborundum, silicon oxide and ferric oxide.

The heat-conducting aggregate is preferably formed by mixing corundum and carborundum in a mass ratio of 1: 0.5-1.5. The corundum mainly comprises alumina, the carborundum mainly comprises silicon carbide, the thermal conductivity of the alumina is 28W/(m.K), and the thermal conductivity of the silicon carbide is 83.6W/(m.K). The alumina and the silicon carbide have wide sources and relatively low prices, and are the better heat-conducting aggregate combination. The corundum is white corundum, brown corundum or black corundum particles with the alumina content of more than 85 percent, and the particle size is preferably 0.15-3 mm; the carborundum content of the carborundum is more than 85 percent, and the grain diameter is preferably 0.15-3 mm.

Further, the conductive material includes at least one of graphene, carbon black, carbon fiber, and graphite. The conductive material is preferably a composite material of graphene and conductive carbon black, wherein the mass ratio of the graphene to the conductive carbon black is 1:1-10, and the more preferable ratio is 1: 8.

The cement comprises one of portland cement, aluminate cement, sulphoaluminate cement, ferro-aluminate cement, fluoroaluminate cement, phosphate cement and sulfate cement, the cement hardness can be 32.5, 42.5, 52.5 or 62.5, and the cement is preferably 42.5 portland cement.

Further, the common aggregate comprises sand and broken stone, and the particle size of the sand is 0.15-1.5 mm; the particle size of the crushed stone is 1-10 mm.

Further, the cement has a sand-lime ratio of 1: 1.5-1: 3.5. the cement with the mortar-sand ratio can exert better physical and mechanical properties and strengthen the compressive strength of the plate.

The second aspect of the present invention discloses a method for preparing an electric heating concrete plate for heating according to the first aspect of the present invention, comprising the steps of:

s1, adding the conductive material and water into a stirring tank, starting stirring, and uniformly dispersing the conductive material in the water;

s2, uniformly mixing cement, heat-conducting aggregate, common aggregate, an early strength agent, a water reducing agent and a defoaming agent in proportion to obtain mixed powder;

s3, adding the mixed powder obtained in the step S2 into a stirring tank in the step S1, and uniformly stirring to obtain conductive concrete mortar;

and S4, pouring the conductive concrete mortar obtained in the step S3 into a mould with the height of 10mm and electrodes at two ends, and curing for 28 days in a room-temperature humid environment to obtain the electric heating concrete plate with the thickness of not more than 10mm, the length of 800mm and the width of 400 mm.

Calculating the formula Q ═ CM ^ T according to heat

Wherein C is the specific heat capacity of the material, in units [ J/(kg.K) ]

M is the mass of the material in kg

T is the temperature difference of the material, in K

In the unit time, the two electric heating concrete plates with the same power have the same energy converted from electric energy to heat energy in the process of electric heating, but according to a heat calculation formula, the larger the mass of the electric heating concrete plates is, the more heat is stored by the electric heating concrete plates, the heat conducted to the external environment is relatively reduced, and the electric heating concrete plates are unfavorable for heating. Therefore, the thickness of the electric heating concrete plate prepared by the invention is not more than 10mm, and the heat conduction and the heat dissipation of the electric heating concrete plate reach the optimal state under the condition that the strength of the plate is not influenced by actual assembly and use.

Testing the heat conductivity coefficient, the resistivity and the board surface temperature difference of the electric heating concrete board; wherein the content of the first and second substances,

the detection method of the heat conductivity coefficient comprises the following steps: cutting the well-maintained electric heating concrete plates into cylindrical sample blocks with the diameter not more than 30mm and the thickness not more than 10mm, putting the cylindrical sample blocks into a Fisher-Beren thermal conductivity coefficient measuring instrument for measurement, cutting 5 groups of sample blocks into each group of plates, and taking an average value.

The resistivity detection method comprises the following steps: and measuring the resistivity of the electric heating concrete plate by using a voltammetry method, wherein two electrodes are pre-embedded at two ends of the electric heating concrete plate, the two electrodes are connected with a power supply, and the current and the voltage of the two electrodes are respectively measured as I and V. Measuring the distance L between two electrodes of the electric heating concrete plate by using a ruler, calculating the cross section area W of one side parallel to the electrodes, and calculating the resistivity of the electric heating plate according to the following formula:

ρ＝VW/IL

wherein rho is the resistivity of the electric heating concrete plate and the unit is omega cm;

v is voltage applied to two ends of the electric heating concrete plate, and the unit is V;

w-the cross-sectional area of the side of the electrothermal concrete plate parallel to the electrode, in cm²

L is the distance between two electrodes in the electric heating concrete plate, and the unit is cm.

The detection method of the temperature difference of the board surface comprises the following steps: in an environment with the room temperature of 20 ℃, 220v alternating current is conducted on the electric heating concrete plate, the power is regulated by a frequency converter to be maintained at 95w, the temperatures of 5 point positions at four corners and the center of the upper surface of the electric heating concrete plate are measured after the electric heating concrete plate is stabilized, and the difference value between the highest temperature and the lowest temperature of the 5 point positions is calculated and used for evaluating the uniformity of the electric heating concrete plate in the heating process. The results are shown in Table 1.

Example 1

The electric heating concrete for heating comprises the following raw materials in parts by weight:

42.5 Portland cement: 100 portions of

Graphene: 1.5 parts of

Conductive carbon black: 9.5 parts of

1-3mm white corundum: 67 portions of

0.15-1mm carborundum: 33 portions of

0.15-1.5 river sand: 40 portions of

1-4mm crushed stone: 60 portions of

Calcium acetate: 0.5 portion

Calcium formate: 0.25 part

Water reducing agent: 0.5 portion

Defoaming agent: 0.3 part

Water: 45 parts of the raw materials.

The preparation method of the electric heating concrete for heating comprises the following steps:

s1: adding graphene, conductive carbon black and water into a stirring tank according to the weight parts, starting stirring, and uniformly dispersing the graphene and the conductive carbon black in the water;

s2: uniformly mixing 42.5 parts of portland cement, white corundum, carborundum, river sand, broken stone, calcium acetate, calcium formate, a water reducing agent and a defoaming agent in parts by weight to obtain mixed powder;

s3: adding the mixed powder obtained in the step S2 into a stirring tank in the step S1, and uniformly stirring to obtain conductive concrete mortar;

s4: and (4) pouring the conductive concrete mortar obtained in the step (S3) into a mould with the height of 10mm and electrodes at two ends, and curing for 28 days in a humid environment at room temperature to obtain the electric heating concrete plate 1 with the thickness of 5mm, the length of 800mm and the width of 400 mm.

Testing the heat conductivity coefficient, the resistivity and the plate surface temperature of the electric heating concrete plate 1; the results are shown in Table 1.

Example 2

The electric heating concrete for heating comprises the following raw materials in parts by weight:

42.5 Portland cement: 100 portions of

Graphene: 2 portions of

Conductive carbon black: 8 portions of

1-3mm white corundum: 80 portions

0.15-1mm carborundum: 120 portions of

0.15-1.5 river sand: 60 portions of

1-4mm crushed stone: 90 portions of

Calcium acetate: 0.5 portion

Calcium formate: 0.5 portion

Water reducing agent: 0.5 portion

Defoaming agent: 0.3 part

Water: 40 parts of the components.

The preparation method of the electric heating concrete for heating comprises the following steps:

s1: adding graphene, conductive carbon black and water into a stirring tank according to the weight parts, starting stirring, and uniformly dispersing the graphene and the conductive carbon black in the water;

s2: uniformly mixing 42.5 parts of portland cement, white corundum, carborundum, river sand, broken stone, calcium acetate, calcium formate, a water reducing agent and a defoaming agent in parts by weight to obtain mixed powder;

s3: adding the mixed powder obtained in the step S2 into a stirring tank in the step S1, and uniformly stirring to obtain conductive concrete mortar;

s4: and (4) pouring the conductive concrete mortar obtained in the step (S3) into a mould with the height of 10mm and electrodes at two ends, and curing for 28 days in a humid environment at room temperature to obtain the electric heating concrete plate 2 with the thickness of 10mm, the length of 800mm and the width of 400 mm.

Testing the heat conductivity coefficient, the resistivity and the plate surface temperature of the electric heating concrete plate 2; the results are shown in Table 1.

Example 3

The electric heating concrete for heating comprises the following raw materials in parts by weight:

42.5 Portland cement: 100 portions of

Carbon nanotube: 1 part of

Conductive carbon black: 4 portions of

1-3mm white corundum: 45 portions of

0.15-1mm carborundum: 55 portions of

0.15-1.5 river sand: 40 portions of

1-4mm crushed stone: 60 portions of

Calcium acetate: 0.5 portion

Water reducing agent: 0.5 portion

Defoaming agent: 0.3 part

Water: 45 parts of the raw materials.

The preparation method of the electric heating concrete for heating comprises the following steps:

s1: adding the carbon nano tube, the conductive carbon black and the water into a stirring tank according to the weight parts, starting stirring, and uniformly dispersing the graphene and the conductive carbon black in the water;

s2: uniformly mixing 42.5 parts of portland cement, white corundum, carborundum, river sand, broken stone, calcium acetate, a water reducing agent and a defoaming agent in parts by weight to obtain mixed powder;

s3: adding the mixed powder obtained in the step S2 into a stirring tank in the step S1, and uniformly stirring to obtain conductive concrete mortar;

s4: and (4) pouring the conductive concrete mortar obtained in the step (S3) into a mould with the height of 10mm and electrodes at two ends, and curing for 28 days in a humid environment at room temperature to obtain the electric heating concrete plate 3 with the thickness of 10mm, the length of 800mm and the width of 400 mm.

Testing the heat conductivity coefficient, the resistivity and the plate surface temperature of the electric heating concrete plate 3; the results are shown in Table 1.

Example 4

The electric heating concrete for heating comprises the following raw materials in parts by weight:

42.5 Portland cement: 100 portions of

Graphene: 3 portions of

Graphite: 12 portions of

1-3mm white corundum: 180 portions of

Silicon oxide: 120 portions of

0.15-1.5 river sand: 10 portions of

1-4mm crushed stone: 40 portions of

Calcium formate: 0.5 portion

Water reducing agent: 0.5 portion

Defoaming agent: 0.3 part

Water: 40 parts of the components.

The preparation method of the electric heating concrete for heating comprises the following steps:

s1: adding graphene, graphite and water into a stirring tank according to the weight parts, starting stirring, and uniformly dispersing the graphene and the conductive carbon black in the water;

s2: uniformly mixing 42.5 parts of portland cement, white corundum, silicon oxide, river sand, broken stone, calcium formate, a water reducing agent and a defoaming agent in parts by weight to obtain mixed powder;

s3: adding the mixed powder obtained in the step S2 into a stirring tank in the step S1, and uniformly stirring to obtain conductive concrete mortar;

s4: and (4) pouring the conductive concrete mortar obtained in the step (S3) into a mould with the height of 10mm and electrodes at two ends, and curing for 28 days in a humid environment at room temperature to obtain the electric heating concrete plate 4 with the thickness of 5mm, the length of 800mm and the width of 400 mm.

Testing the heat conductivity coefficient, the resistivity and the plate surface temperature of the electric heating concrete plate 4; the results are shown in Table 1.

Example 5

The electric heating concrete for heating comprises the following raw materials in parts by weight:

42.5 Portland cement: 100 portions of

Graphene: 1.5 parts of

Conductive carbon black: 9.5 parts of

Silicon oxide: 45 portions of

Iron oxide: 55 portions of

0.15-1.5 river sand: 25 portions of

1-4mm crushed stone: 25 portions of

Calcium acetate: 0.5 portion

Water reducing agent: 0.5 portion

Defoaming agent: 0.3 part

Water: 40 parts of the components.

The preparation method of the electric heating concrete for heating comprises the following steps:

s1: adding graphene, conductive carbon black and water into a stirring tank according to the weight parts, starting stirring, and uniformly dispersing the graphene and the conductive carbon black in the water;

s2: uniformly mixing 42.5 parts of portland cement, silicon oxide, ferric oxide, river sand, broken stone, calcium acetate, a water reducing agent and a defoaming agent in parts by weight to obtain mixed powder;

s3: adding the mixed powder obtained in the step S2 into a stirring tank in the step S1, and uniformly stirring to obtain conductive concrete mortar;

s4: and (4) pouring the conductive concrete mortar obtained in the step (S3) into a mould with the height of 10mm and electrodes at two ends, and curing for 28 days in a humid environment at room temperature to obtain the electric heating concrete plate 5 with the thickness of 10mm, the length of 800mm and the width of 400 mm.

Testing the heat conductivity coefficient, the resistivity and the plate surface temperature of the electric heating concrete plate 5; the results are shown in Table 1.

Example 6

The electric heating concrete for heating comprises the following raw materials in parts by weight:

42.5 Portland cement: 100 portions of

Graphene: 1.5 parts of

Conductive carbon black: 9.5 parts of

1-3mm white corundum: 150 portions of

0.15-1mm carborundum: 150 portions of

Calcium formate: 0.5 portion

Water reducing agent: 0.5 portion

Defoaming agent: 0.3 part

Water: 45 parts of the raw materials.

The preparation method of the electric heating concrete for heating comprises the following steps:

s1: adding graphene, conductive carbon black and water into a stirring tank according to the weight parts, starting stirring, and uniformly dispersing the graphene and the conductive carbon black in the water;

s2: uniformly mixing 42.5 parts of portland cement, white corundum, carborundum, calcium formate, a water reducing agent and a defoaming agent in parts by weight to obtain mixed powder;

s3: adding the mixed powder obtained in the step S2 into a stirring tank in the step S1, and uniformly stirring to obtain conductive concrete mortar;

s4: and (4) pouring the conductive concrete mortar obtained in the step (S3) into a mould with the height of 10mm and electrodes at two ends, and curing for 28 days in a humid environment at room temperature to obtain the electric heating concrete plate 6 with the thickness of 10mm, the length of 800mm and the width of 400 mm.

Testing the heat conductivity coefficient, the resistivity and the plate surface temperature of the electric heating concrete plate 6; the results are shown in Table 1.

Comparative example 1

The raw material components and the preparation method were the same as in example 4 except that the early strength agent was 0.5 part of calcium nitrite.

Manufacturing an electrothermal concrete plate 7, and testing the heat conductivity coefficient, the resistivity and the plate surface temperature difference (5 points at four corners and the center) of the electrothermal concrete plate 7; the results are shown in Table 1.

Comparative example 2

The raw material components and the preparation method were the same as in example 1 except that the early strength agent was not added.

Manufacturing an electrothermal concrete plate 8, and testing the heat conductivity coefficient, the resistivity and the plate surface temperature difference (5 points at four corners and the center) of the electrothermal concrete plate 8; the results are shown in Table 1.

Comparative example 3

The raw material components and the preparation method were the same as in example 3, except that the thermally conductive aggregate was not added. Preparing an electrothermal concrete plate 9, and testing the heat conductivity coefficient, the resistivity and the plate surface temperature difference (5 points at four corners and the center) of the electrothermal concrete plate 9; the results are shown in Table 1.

Comparative example 4

The raw material components and the preparation method were the same as in example 4 except that the early strength agent was not added.

Manufacturing an electrothermal concrete plate 10, and testing the heat conductivity coefficient, the resistivity, the plate surface temperature difference and the highest temperature of the electrothermal concrete plate 10; the results are shown in Table 1.

TABLE 1

From table 1, it can be seen from comparison between example 1 and comparative example 2 that example 1 added calcium acetate and calcium formate as early strength agents also has the effect of reducing the resistivity of the electric heating concrete plate. From example 3 and comparative example 3, the addition of the thermal-conductive aggregate significantly improves the thermal conductivity of the electric heating concrete plate, and the thermal conductivity of the plate is increased; in addition, the board surface temperature difference of the example 3 is smaller than that of the comparative example 3, which shows that the adding of the heat-conducting aggregate improves the uniformity of heating of the electric heating concrete board. As can be seen from comparison between example 4 and comparative example 4, the addition of calcium formate as an early strength agent also has the effect of reducing the resistivity of the electric heating concrete plate. Although the calcium nitrite used as the early strength agent in comparative example 1 also has the effect of reducing the resistivity, the nitrite is unstable in nature and may volatilize toxic nitrogen oxides during the energization heating, which is disadvantageous for indoor heating. And the calcium acetate and the calcium formate have stable properties, do not volatilize harmful substances in the heating process of the electric heating concrete plate (the temperature is not more than 60 ℃), and are safe and reliable.

From the example 1 and the example 2, under the condition that the power is 95w, the highest temperature of the surface of the electric heating concrete plate 1 is 9 ℃ higher than that of the electric heating concrete plate 2, and the thinner the thickness of the electric heating concrete plate is, the more the heat dissipation is facilitated, and the heating efficiency is improved.

Although the description is given in terms of embodiments, not every embodiment includes only a single technical solution, and such description is given for clarity only, and those skilled in the art should make the description as a whole, and the technical solutions in the embodiments may be appropriately combined to form other embodiments understood by those skilled in the art.

Therefore, the above description is only a preferred embodiment of the present application, and is not intended to limit the scope of the present application; all changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.