Grounding resistance reducing agent

Abstract

To provide a grounding resistance reducing agent capable of maintaining low electrical resistance even in a place where water such as groundwater flows.SOLUTION: A grounding resistance reducing agent according to the present invention contains CaO, Al2O3, SiO2, and an alkali metal as chemical components. The composition preferably contains CaO in a ratio of 10 to 35 mass%, Al2O3 in a ratio of 10 to 30 mass%, and SiO2 in a ratio of 15 mass% or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a ground resistance reducing agent for use in grounding work such as electrical work. [Background technology]

[0002] Conventionally, a ground electrode is laid when installing communication equipment or power equipment. When laying this ground electrode, the lower the ground resistance, the smoother the large current can be discharged into the ground, so various ground resistance reduction treatments have been implemented. For example, attempts have been made to reduce ground resistance by filling and treating the soil around the ground electrode with a ground resistance reducing agent.

[0003] As an example of the ground resistance reducing agent that can be used, the following Patent Document 1 describes a ground resistance reducing agent that contains silica sol, and a carbon substance and / or a gelling substance. Also, Patent Document 2 describes a ground resistance reducing agent that contains hydraulic fine particles with an average particle size of 15 μm or less. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-208840 [Patent Document 2] Japanese Patent Application Publication No. 10-203853 Summary of the Invention [Problem to be solved by the invention]

[0005] Ground resistance reducers are used in various places, and are also expected to be used in places where water such as groundwater flows, but no consideration has been given to ground resistance reducers intended for use in such places. The ground resistance reducers described in Patent Documents 1 and 2 were also not intended for use in places where water flows.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to provide a ground resistance reducer that can maintain low electrical resistance even in places where water such as groundwater flows. [Means for solving the problem]

[0007] As a result of intensive research into solving the above problems, the present inventors have found that the problems can be solved by including a specific chemical component, and have arrived at the present invention. [1] A ground resistance reducer whose chemical components include CaO, Al2O3, SiO2, and alkali metals. [2] The ground resistance reducing agent according to [1], containing, as chemical components, 10 to 35 mass % of the CaO, 10 to 30 mass % of the Al2O3, and 15 mass % or less of the SiO2. [3] The ground resistance reducing agent according to [1] or [2], wherein a molar ratio of the CaO to the Al2O3 (CaO / Al2O3) is 0.3 to 3.5. [4] Blaine specific surface area is 3,000 to 8,000 cm 2 / g. [5] The ground resistance reducing agent according to any one of [1] to [4], further comprising an oxycarboxylic acid. [6] The ground resistance reducing agent according to any one of [1] to [5], having a dissolution pH of 5 to 9. [7] The ground resistance reducing agent according to any one of [1] to [6], containing sand in an amount of 15 mass% or less. [8] The ground resistance reducer according to any one of [1] to [7], further comprising slaked lime. Effect of the Invention

[0008] According to the present invention, low electrical resistance can be maintained even in a place where water such as groundwater flows. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The ground resistance reducing agent of the present invention will be described in detail below, but the present invention is not limited to this embodiment. In this specification, "%" is based on mass unless otherwise specified. In addition, a numerical range specified using the symbol "~" includes the numerical values ​​at both ends (upper and lower limits) of "~".

[0010] [Ground resistance reducing agent] The ground resistance reducing agent of the present invention contains, as chemical components, CaO, Al2O3, SiO2, and an alkali metal.

[0011] The ground resistance reducer of the present invention contains CaO as a chemical component. The content of CaO in the ground resistance reducer, excluding the CaO derived from gypsum, is preferably 5 to 45 mass%, more preferably 10 to 35 mass%, and even more preferably 15 to 30 mass%. By setting the CaO content within the above range, it is possible to impart an appropriate rapid hardening property to the ground resistance reducer. The ground resistance reducer of the present invention also contains Al2O3 as a chemical component. The content of Al2O3 in the ground resistance reducer is preferably 10 to 37 mass%, more preferably 10 to 30 mass%, and even more preferably 15 to 25 mass%. By setting the content of Al2O3 within the above range, it is possible to impart an appropriate rapid hardening property to the ground resistance reducer. Furthermore, the ground resistance reducing agent of the present invention contains SiO2 as a chemical component. The content of SiO2 is preferably 15 mass% or less, more preferably 10 mass% or less, and even more preferably 5 mass% or less. The content of SiO2 is preferably 0.5 mass% or more, more preferably 1.0 mass% or more, and even more preferably 1.5 mass% or more. By setting the content of SiO2 within the above range, it is possible to impart appropriate hardening properties.

[0012] In addition, the molar ratio of CaO to Al2O3 (CaO / Al2O3) is preferably 0.3 to 3.5, and more preferably 0.6 to 2.0. By setting CaO / Al2O3 in the above range, it is possible to reduce acute deterioration. In other words, it is possible to maintain low electrical resistance in running water.

[0013] Furthermore, the ground resistance reducing agent of the present invention contains an alkali metal as a chemical component. The alkali metal is preferably contained as an alkali metal inorganic salt. The alkali metal inorganic salt is a substance that is conductive or has a reduced electrical resistance, and reduces the ground resistance of the hardened body obtained by the hydration reaction of the ground resistance reducing material. Specific examples include alkali metal inorganic salts such as sodium chloride, potassium chloride, and lithium chloride. By using an alkali metal inorganic salt as a conductive substance, the effect of reducing the ground resistance can be imparted even in running water.

[0014] The content of the alkali metal inorganic salt in the ground resistance reducing agent is preferably 4.0 to 6.0 mass %, and more preferably 4.5 to 5.5 mass %. By setting the content of the inorganic salt within the above range, the ground resistance can be effectively reduced when the ground resistance reducing agent is hardened.

[0015] The ground resistance reducing agent of the present invention may contain components other than the above CaO, Al2O3, SiO2, and alkali metals. Examples of the components other than the above include CaSO4. When the ground resistance reduction agent contains CaSO4, this can be achieved by adding gypsum, as described below.

[0016] The content of chemical components can be determined, for example, by measurement using an X-ray fluorescence (XRF) analyzer (Rigaku Corporation, product name: Primus II) and calculation from the measured values. For example, gypsum (CaSO4) is measured as sulfur oxide (SO3), so the proportion of gypsum can be determined from the analysis value of SO3. In addition, the proportion of CaO is the proportion excluding CaO derived from gypsum, so it can be determined by subtracting CaO derived from gypsum from the analysis value of CaO. Specifically, it can be determined by the following formula. CaSO4(%) = [SO3 analysis value(%)] x 1.7004 CaO (%) = [CaO analysis value (%)] - [CaSO4 content (%) × 0.4119] In addition, since the alkali metal inorganic salt is measured as the alkali metal oxide, the amount of the alkali metal inorganic salt can be calculated from the analytical value. For example, if potassium chloride (KCl) is contained as the alkali metal inorganic salt, the amount of potassium oxide (KO) can be calculated from the following formula. KCl(%) = [K2O analysis value(%)] × 1.5829

[0017] The CaO and Al2O3 in the ground resistance reducing agent of the present invention can be contained as clinker made of calcium aluminate containing CaO and Al2O3, or as ground clinker obtained by pulverizing the clinker. The clinker can be obtained by appropriately mixing the CaO raw material and the Al2O3 raw material and subjecting them to heat treatment using an electric furnace or a kiln. SiO2 can be contained in small amounts in the CaO raw material and the Al2O3 raw material when producing the clinker. Examples of CaO raw materials include quicklime, limestone, and hydrated lime. Examples of Al2O3 raw materials include bauxite and aluminum ash.

[0018] The calcium aluminate is contained in the ground resistance reducing agent in an amount of preferably 30 to 65 mass %, more preferably 35 to 60 mass %, and even more preferably 40 to 55 mass %.

[0019] (Gypsum) The ground resistance reducing agent of the present invention preferably contains gypsum. By containing gypsum, the gypsum reacts with calcium aluminate to generate hydraulic ettringite. By generating hydraulic ettringite in the ground resistance reducing agent, it is possible to effectively reduce the ground resistance when the ground resistance reducing agent is hardened.

[0020] As the gypsum, any of gypsum dihydrate, gypsum hemihydrate, and anhydrous gypsum can be used, but in terms of rapid hardening and strength development, it is preferable to use gypsum hemihydrate. As described above, the content of gypsum can be determined from the analysis value of SO3 measured by a fluorescent X-ray (XRF) analyzer, and it is preferable that the content of CaSO4 in the ground resistance reducing agent is 30 to 60 mass%, and more preferably 35 to 50 mass%. By setting the content of gypsum within the above range, it is possible to increase the long-term strength and reduce deterioration in flowing water. In other words, it is possible to maintain low electrical resistance in flowing water.

[0021] (oxycarboxylic acid) The ground resistance reducing agent of the present invention preferably contains an oxycarboxylic acid. By containing an oxycarboxylic acid, the setting time when the ground resistance reducing agent is made into a slurry can be adjusted. In addition, the dispersibility of particles can be improved, so that the material separation can be improved. Specifically, citric acid, gluconic acid, tartaric acid, malic acid, etc., or their sodium salts or potassium salts, etc., can be used as the oxycarboxylic acid. Among these, malic acid is preferable in terms of adjusting the setting time. The oxycarboxylic acid is preferably contained in the ground resistance reducing agent in an amount of 0.01 to 5 mass %, more preferably 0.1 to 2 mass %. By setting the content of the oxycarboxylic acid in the above range, the setting time can be adjusted, and both the working time and the appropriate rapid hardening can be achieved.

[0022] (Slaked lime) The ground resistance reducer of the present invention preferably contains slaked lime. By containing slaked lime, the hardening time of the ground resistance reducer can be adjusted. The content of slaked lime in the ground resistance reducer is preferably 0.05 to 5 mass %, and more preferably 0.1 to 2 mass %. By setting the content of slaked lime within the above range, the hardening time can be accelerated.

[0023] (sand) The ground resistance reducer of the present invention preferably does not contain sand, but may contain sand for the purpose of improving the mixability of the ground resistance reducer. When sand is contained, the amount of sand in the ground resistance reducer is preferably 15% by mass or less, and more preferably 5% by mass or less. By containing sand, the mixability of each material can be improved, but since sand is prone to sinking and material separation of the sand itself is likely to occur, it is preferable that the sand content is small, and it is preferable that it is within the above range.

[0024] (Other Ingredients) In the present invention, coal ash, fly ash, granulated blast furnace slag, etc. can be used as long as the performance of the present invention is not adversely affected.

[0025] The specific surface area of ​​the earth resistance reducing agent is 3,000 to 8,000 cm 2 / g, and 3,500 to 7,000 cm 2 By setting the Blaine specific surface area in the above range, it is possible to improve the strength development of the hardened body obtained by hardening the ground resistance reducing agent, and to suppress deformation in running water. The Blaine specific surface area can be measured based on JIS R5201 (physical testing method for cement). The Blaine specific surface area can be adjusted by a pulverizing and / or classification process.

[0026] The ground resistance reducer of the present invention has an elution pH of preferably 5 to 9, more preferably 5.5 to 8.7, and even more preferably 6 to 8.5. By setting the elution pH within the above range, even when the agent is used in a place where water such as groundwater flows, it is possible to prevent the surrounding area from being corroded by groundwater near the agent. The elution pH can be adjusted to 5 to 9, for example, by adjusting the contents of Al2O3 and CaSO4. The elution pH can be measured by crushing the hardened body of the ground resistance reducing agent, adding water to the crushed sample, shaking it, and measuring the pH of the supernatant. Specifically, it can be measured by the measurement method described in the examples below. EXAMPLES

[0027] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0028] <Preparation of ground resistance reducing agent> (Raw materials used) CaO: Special grade reagent, commercially available ·Al2O3: Special grade reagent, commercially available SiO2: Silica sand, commercially available Gypsum: Hemihydrate gypsum, commercially available Potassium chloride: Reagent, commercial product - Slaked lime: commercially available Malic acid: commercially available ·Sand: JIS standard sand

[0029] CaO, Al2O3, and optionally SiO2 were mixed, heated and melted in a high-frequency furnace, quenched in water, and pulverized to produce a clinker pulverized material. Gypsum, potassium chloride, hydrated lime, malic acid, and sand were mixed with this clinker pulverized material to obtain a ground resistance reducer. The chemical composition was measured using an X-ray fluorescence (XRF) analyzer (Rigaku Corporation, product name: Primus II). The chemical components of CaO, CaSO4, and KCl were calculated using the following formula. The other components were measured using the X-ray fluorescence analyzer. CaSO4(%) = [SO3 analysis value(%)] x 1.7004 CaO (%) = [CaO analysis value (%)] - [CaSO4 content (%) × 0.4119] KCl(%) = [K2O analysis value(%)] × 1.5829 The pH of the elution test was performed by crushing and sieving the hardened product of the manufactured earth resistance reducing agent, collecting the particles with a particle size of 0.5 mm to 5 mm, and using them as samples for the elution test. The elution test was performed by putting 50 g of the sample and 500 g of pure water into a 1000 ml poly bottle, shaking it continuously for 6 hours with a shaker adjusted to a rotation speed of 200 rpm, and measuring the pH value of the supernatant liquid. The liquid temperature during the pH measurement was 20°C.

[0030] [Table 1]

[0031] Using the manufactured earth resistance reducing agent, the hardening time, specific resistance value, acute deterioration, compressive strength, and material separation were measured and evaluated as follows. The results are shown in Table 2. (Test Method) Curing time: 200 parts by mass of water (tap water) was added to 100 parts by mass of ground resistance reduction material, and mixed in an environment of 20°C. The time until the mixed ground resistance reduction material was pressed with a finger without being dented was measured. A curing time of 30 minutes or less was considered to be acceptable. Resistivity: A copper plate was placed 1 cm from each end in a 4 x 4 x 16 cm formwork. 200 parts by mass of water was added to 100 parts by mass of ground resistance reduction material, and the mixed ground resistance reduction material was poured into the formwork. After 24 hours, the formwork was removed and the copper plate was brought into contact with the ground rod of a ground resistance meter to measure the resistivity. A resistivity value of 100 Ω·cm or less was deemed to have passed the test. Acute Deterioration: A hardened earth resistance reduction material was prepared using the same method as used to measure the resistivity value. The demolded earth resistance reduction material was placed in a water tank with a water hose inserted, the tap was opened, and the water flow rate was adjusted to 150ml / min. After immersion in running water for 28 days, the resistivity value was measured, and this resistivity value was considered to be acute deterioration. A resistivity value of 1000 Ω·cm or less after 28 days was considered to have passed. Compressive strength: Using a ground resistance reduction material in which 200 parts by mass of water was added to 100 parts by mass of the ground resistance reduction material, the compressive strength was measured at 28 days in a 20°C environment in accordance with JIS R 5201. The compressive strength was 1.0 N / mm 2 The above is considered a pass. Material separation: 200 parts by mass of water were added to 100 parts by mass of ground resistance reduction material, and mixed in an environment of 20°C. The mixture was left to stand for one minute, and the presence or absence of separation between the water and materials was observed visually. Those that did not separate were rated "absent", and those that did separate were rated "present".

[0032] [Table 2] [Industrial Applicability]

[0033] The ground resistance reducing agent of the present invention can be suitably used in grounding work such as electrical work.

Claims

1. Chemical components include CaO and Al. ２ O ３ , SiO ２ and an alkali metal.

2. As chemical components, the CaO is 10 to 35 mass %, the Al ２ O ３ 10 to 30 mass % of the SiO ２ The ground resistance reducing agent according to claim 1, comprising:

3. The CaO and the Al ２ O ３ The molar ratio of CaO / Al ２ O ３ 3. The ground resistance reducing agent according to claim 1 or 2, wherein the value of the saturation coefficient is 0.3 to 3.

5.

4. Blaine specific surface area is 3,000 to 8,000 cm ２ The ground resistance reducing agent according to claim 1 or 2, wherein the average molecular weight of the ground resistance reducing agent is 1000 or more.

5. The ground resistance reducing agent according to claim 1 or 2, further comprising an oxycarboxylic acid.

6. The ground resistance reducing agent according to claim 1 or 2, wherein the elution pH is 5 to 9.

7. The ground resistance reducing agent according to claim 1 or 2, containing sand in an amount of 15 mass% or less.

8. The ground resistance reducing agent according to claim 1 or 2, further comprising slaked lime.

Images