Predecessor for ready mixed concrete pumping and ready mixed concrete pumping method

Abstract

To provide means capable of easily, inexpensively and effectively suppressing the clogging of a piping upon ready mixed concrete pumping by a concrete pump vehicle or the like.SOLUTION: A predecessor for ready mixed concrete pumping comprises sodium polyacrylate and the salt(s) thereof as active ingredients, in which the salt(s) is one or more selected from sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium hydrogen carbonate and trisodium citrate. Also provided are ready mixed concrete pumping method or the like using the same. Prior to ready mixed concrete pumping by a concrete pump vehicle or the like, by circulating the solution through the inside of a piping, previously, the inner wall of the piping is covered with the solution having viscosity to form a covered layer, and, even after the start of the pumping of ready mixed concrete, the viscosity of the solution is maintained to hold the covered layer till the ready mixed concrete is filled into the whole inside of the piping. So that, the clogging of the piping or the like can be easily, inexpensively and effectively suppressed.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a pre-pumping agent for pumping ready-mixed concrete, which contains sodium polyacrylate and a salt as active ingredients, and the salt is one or more of sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium hydrogen carbonate, and trisodium citrate, and a method for pumping ready-mixed concrete, which includes a step of pumping a solution containing the pre-pumping agent prior to the ready-mixed concrete. [Background technology]

[0002] Concrete is a material made by solidifying gravel, sand, water, etc. with cement, and because of its strength and ease of construction, it is widely used as a structural material in architectural and civil engineering works such as buildings, dams, bridges, and port facilities.

[0003] In most cases, the construction of concrete structures is carried out at a batcher plant (ready-mixed concrete factory) by mixing and kneading cement, aggregate, water, etc. to produce ready-mix concrete, which is then transported to the construction site while being mixed in an agitator truck (mixer truck), and the ready-mix concrete is poured (placed) into forms using a concrete pump truck. After being left to cure for a certain period of time to harden, the forms are then removed.

[0004] A concrete pump truck is a vehicle used to pour ready mixed concrete into a formwork at a construction site, and is mainly equipped with a hopper, a pressure pump, and piping to pump the ready mixed concrete. Ready mixed concrete supplied to the hopper of a concrete pump truck or the like from an agitator truck is pumped through a long pipe and poured into the formwork.

[0005] When pumping ready-mixed concrete using a concrete pump truck or the like, if pumping of ready-mixed concrete is started without any pretreatment, before the entire inside of the pipe is filled with ready-mixed concrete, only the cement and other materials will adhere to the inner wall surface from the front side of the pipe first, and only the gravel and other concrete components will reach the outlet side of the pipe, which will result in accidents that the pipe becomes clogged with gravel and the ready-mixed concrete cannot be pumped. Therefore, as a pretreatment, generally, before pumping ready-mixed concrete, cement paste or mortar is sent into the pipe in advance to cover the inner wall surface of the pipe with cement paste or mortar, and then ready-mixed concrete is pumped continuously to prevent clogging of the pipe (see Patent Document 1, for example).

[0006] However, when pretreatment is performed using cement paste or mortar, a relatively large amount of cement paste must be used to cover the inner wall surface of the pipe, which is costly and cumbersome. In addition, since cement paste or mortar are also components of ready-mixed concrete, pretreatment with them causes a hardening reaction to proceed during the period from pretreatment to pumping the ready-mixed concrete, making it difficult to precisely predict and control the quality of the concrete after it is poured.

[0007] Therefore, various means that can be used as an alternative to pretreatment with cement paste or mortar have been proposed. For example, Patent Document 2 describes a concrete pump pumping initiator containing a water-absorbent resin, Patent Document 3 describes a composition containing fine fibrous modified cellulose and the like that is used to manufacture a concrete pump pumping initiator by mixing with calcium carbonate powder, and Patent Document 4 describes a concrete pumping agent composed of sodium carbonate, melamine, citric acid, polyacrylamide, and methylcellulose. [Patent Document 1] Japanese Patent Application Publication No. 8-1643 [Patent Document 2] JP 2000-34461 A [Patent Document 3] JP 2020-1586931 A [Patent Document 4] JP 2008-74086 A DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0008] In pretreatment before pumping ready-mixed concrete using a concrete pump truck or the like, when a thickener or the like is used as a precursor agent as an alternative to cement paste or mortar, it is possible to simplify the work and reduce costs compared to using cement paste or mortar, but it cannot be said that this sufficiently prevents blockages in pipes, etc.

[0009] Therefore, an object of the present invention is to provide a simple, inexpensive and effective means for preventing blockage of pipes etc. when pumping ready-mixed concrete using a concrete pump truck etc. [Means for solving the problem]

[0010] The present inventors have newly discovered that the reason why the use of a thickening agent or the like as a precursor agent for pumping fresh concrete in a concrete pump truck or the like cannot sufficiently prevent clogging of pipes, etc. is because when the pumping of fresh concrete begins, the viscosity of the thickening agent is lost upon contact with the fresh concrete, and the coating layer that had once formed on the inner wall of the pipe disappears due to the flow of the precursor agent. The present inventors have also newly discovered that by mixing a specified salt with sodium polyacrylate, the viscosity of the solution can be maintained after the pumping of fresh concrete begins until the entire inside of the pipe is filled with fresh concrete, in other words, the coating layer formed on the inner wall of the pipe can be maintained after the pumping of the fresh concrete begins until the entire inside of the pipe is filled with fresh concrete, and the effect of preventing pipe clogging as a pretreatment when pumping fresh concrete can be improved.

[0011] Therefore, the present invention provides a pre-mixing agent for pumping ready-mixed concrete, which contains sodium polyacrylate and a salt as active ingredients, and the salt is one or more of sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium hydrogen carbonate, and trisodium citrate, and a method for pumping ready-mixed concrete using the same.

[0012] Prior to pumping fresh concrete with a concrete pump truck or the like, a solution containing sodium polyacrylate and a specified salt as active ingredients as a precursor agent is circulated through the pipe, so that the inner wall of the pipe is coated with the viscous solution in advance to form a coating layer, and even after pumping of the fresh concrete begins, the viscosity of the solution is maintained and the coating layer is maintained until the entire inside of the pipe is filled with fresh concrete. Therefore, by employing this technology as a pretreatment when pumping fresh concrete, clogging of pipes etc. can be easily, inexpensively and effectively suppressed. Effect of the Invention

[0013] By using the pretreatment method of the present invention, clogging of pipes etc. during pumping of ready-mix concrete by a concrete pump truck etc. can be easily, inexpensively and effectively prevented. BEST MODE FOR CARRYING OUT THEINVENTION

[0014] <Regarding the pre-mixing agent for pumping ready-mixed concrete according to the present invention> The present invention broadly includes a premix for pumping ready-mixed concrete, which contains at least sodium polyacrylate and a specified salt as active ingredients.

[0015] Here, sodium polyacrylate is a sodium salt of polyacrylic acid, which is a polymer of acrylic acid, and a wide variety of known sodium polyacrylates can be used.

[0016] The salt according to the present invention is any one or more of sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium hydrogen carbonate, and trisodium citrate (a mixture of two or more of them), and any known salts can be used. The present invention broadly includes salts containing at least one of them.

[0017] The prior agent according to the present invention may be in the form of a mixed powder obtained by mixing sodium polyacrylate powder and salt powder until the mixture is substantially uniform, or may be in the form of an aqueous solution obtained by dissolving the powders in water.

[0018] Furthermore, those obtained by dissolving these powders in a water-soluble organic solvent, or those obtained by further diluting the same with water, are also broadly included in the prior agent of the present invention.

[0019] The water-soluble organic solvent is not narrowly limited and may be any of a wide variety of known organic solvents.

[0020] Examples of the water-soluble organic solvent include aprotic organic solvents such as 1,4-dioxane, anisole, diethylene glycol dimethyl ether, cyclohexanone, N,N-dimethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, hexamethylphosphonic acid triamide, triethyl phosphate, succinonitrile, benzonitrile, pyridine, nitromethane, morpholine, ethylenediamine, dimethyl sulfoxide, sulfolane, propylene carbonate, diethylene glycol ethyl methyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, and triethylene glycol dimethyl ether. Also usable are protic organic solvents such as ethanol, methanol, butanol, isobutyl alcohol, isopentyl alcohol, cyclohexanol, ethylene glycol, propylene glycol, 2-methoxyethanol, 2-ethoxyethanol, phenol, benzyl alcohol, diethylene glycol, triethylene glycol, glycerin, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, and polyethylene glycol monomethyl ether.

[0021] In addition, the prior art agent according to the present invention broadly includes those to which other known compounds, etc. are appropriately added depending on the purpose and application, such as improving the solubility of powders, maintaining and stabilizing the quality of a solution, etc.

[0022] The mixing ratio of sodium polyacrylate and salt is not narrowly limited within the range effective as a pre-mixing agent for pumping fresh concrete. For example, if the weight ratio is 1 part sodium polyacrylate to at least 0.6 parts salt, clogging of pipes during pumping of fresh concrete by a concrete pump truck or the like can be effectively suppressed. The upper limit of the mixing ratio of salt can be appropriately determined in consideration of the raw material price of salt, and is not particularly limited. For example, the weight ratio may be 1 part sodium polyacrylate to 10 parts salt or less, preferably 7.0 parts or less, and more preferably 5.0 parts or less. However, when the salt is sodium dihydrogen phosphate, the range of 1 part sodium polyacrylate to 3.0 parts sodium dihydrogen phosphate or less is preferable.

[0023] <Method of pumping ready-mixed concrete according to the present invention> The present invention includes all methods for pumping ready-mixed concrete that include at least a step of pumping a solution containing sodium polyacrylate and a salt as active ingredients, the salt being any one or more of sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium bicarbonate, and trisodium citrate, prior to the ready-mixed concrete, and is not narrowly limited by, for example, including other steps. Note that the "solution containing sodium polyacrylate and a salt" here broadly includes, for example, those mentioned above.

[0024] Pumping ready-mixed concrete includes, for example, (1) a process of feeding a precursor agent into a concrete pump truck, etc., and pumping the precursor agent into the pump and piping, etc., (2) a process of pumping the ready-mixed concrete after pretreatment with the precursor agent, and filling the ready-mixed concrete into the piping, (3) a process of recovering the ready-mixed concrete that was pumped initially so as not to change the exact composition of the concrete to be poured by mixing in the precursor agent, and (4) a process of actually pouring the ready-mixed concrete into the formwork.

[0025] Among these, in the step of introducing and delivering the precursor agent, it is sufficient that a solution containing at least sodium polyacrylate and a specified salt as active ingredients can be circulated in the pump and piping of a concrete pump truck, and any known means can be widely adopted and is not narrowly limited.

[0026] For example, a solution containing sodium polyacrylate and a specified salt as active ingredients can be poured into the hopper of a concrete pump truck, and the solution can be circulated through the pump and piping by starting the pressure pump.

[0027] The concentration of sodium polyacrylate and salt in this solution is not narrowly limited as long as the pretreatment can effectively prevent clogging of pipes, etc. For example, when the above-mentioned mixing ratio is used and the concentration of sodium polyacrylate and salt in the solution is 0.5 to 50 g / L, more preferably 0.8 to 20 g / L, and most preferably 1.0 to 10 g / L, clogging of pipes, etc. during pumping of ready-mixed concrete by a concrete pump truck, etc. can be effectively prevented.

[0028] The amount of this solution to be fed may be appropriately set depending on the diameter, total length, etc. of the piping of the concrete pump truck, and is not narrowly limited as long as the pretreatment can effectively prevent clogging of the piping, etc. When the piping of a concrete pump truck has an outer diameter of 5 inches (about 12.7 cm) and a total length of about 11 m to 40 m, for example, clogging of the piping of the concrete pump truck can be effectively prevented by feeding 1 to 500 L, more preferably 5 to 100 L, and most preferably 8 to 50 L of the solution having the above-mentioned concentration as pretreatment with the precursor agent. Example 1

[0029] In Example 1, it was examined whether the viscosity of an aqueous solution was maintained when cement was added to the aqueous solution in which sodium polyacrylate and sodium dihydrogen phosphate were dissolved.

[0030] 1g of sodium polyacrylate powder and 1g of sodium dihydrogen phosphate powder were placed in a beaker and mixed until uniform, then 100g of water was added and stirred well to dissolve the powder. As a control, 1g of sodium polyacrylate powder was added to 100g of water and dissolved. As a result, both aqueous solutions showed almost the same strong viscosity.

[0031] Next, 40 g of cement (powder) was added to each aqueous solution and thoroughly stirred. Whether the viscosity was maintained after adding the cement was then evaluated by visual inspection.

[0032] The results are shown in Table 1. In the table, "No. 1" indicates the result of evaluating whether the viscosity was maintained for a sample in which only sodium polyacrylate was dissolved in water (control), and "No. 2" indicates the result of evaluating whether the viscosity was maintained for a sample in which sodium polyacrylate and sodium dihydrogen phosphate were dissolved in water. The viscosity was evaluated on a four-point scale, with "x" indicating that the viscosity was lost and the sample returned to an almost water-like state due to the addition of cement, "△" indicating that the sample retained some viscosity but returned to an almost water-like state, "◯" indicating that a certain level of viscosity was maintained, and "◎" indicating that the viscosity was almost the same as before the addition of cement. [Table 1]

[0033] As shown in Table 1, in the case of an aqueous solution containing only sodium polyacrylate, the viscosity was lost and the solution returned to an almost water-like state upon addition of cement, whereas in the case of an aqueous solution containing sodium polyacrylate and sodium dihydrogen phosphate, the viscosity remained almost the same as before the addition of cement, even after the addition of cement.

[0034] This result suggests that the reason why the use of a sodium polyacrylate solution as a precursor agent for pumping fresh concrete was unable to sufficiently prevent pipe clogging is because the viscosity of the sodium polyacrylate solution is lost when the fresh concrete is pumped, causing the coating that had formed on the inner wall of the pipe to disappear.It also suggests that by mixing sodium dihydrogen phosphate with sodium polyacrylate, the viscosity of the solution can be maintained even after the fresh concrete is pumped, in other words, the coating that had formed on the inner wall of the pipe can be maintained after the fresh concrete is pumped until the entire inside of the pipe is filled with fresh concrete, thereby improving the effect of preventing pipe clogging as a pretreatment when pumping fresh concrete. Example 2

[0035] In Example 2, it was examined whether the viscosity of the aqueous solution was maintained when cement was poured into the aqueous solution in which salts other than sodium polyacrylate and sodium dihydrogen phosphate were dissolved.

[0036] As salts other than sodium dihydrogen phosphate, disodium citrate, disodium succinate, and potassium dihydrogen phosphate were prepared, and 1 g of sodium polyacrylate powder and 1 g of each salt powder were placed in each beaker and mixed uniformly in the same manner as in Example 1. Then, 100 g of water was added and thoroughly stirred to dissolve the powder. As a result, all of the aqueous solutions showed strong viscosity.

[0037] Next, 40 g of cement (powder) was added to each aqueous solution and thoroughly stirred. Whether the viscosity was maintained after the addition of cement was then evaluated by visual inspection.

[0038] The results are shown in Table 2. In the table, "No. 3" shows the result of evaluating whether the viscosity was maintained for a sample in which sodium polyacrylate and disodium citrate were dissolved in water, "No. 4" shows the result of evaluating whether the viscosity was maintained for a sample in which sodium polyacrylate and disodium succinate were dissolved in water, and "No. 5" shows the result of evaluating whether the viscosity was maintained for a sample in which sodium polyacrylate and potassium dihydrogen phosphate were dissolved in water. The standards for viscosity evaluation were the same as in Example 1. [Table 2]

[0039] As shown in Table 2, in the aqueous solutions containing sodium polyacrylate and disodium citrate or disodium succinate, the viscosity was almost completely lost upon addition of cement, and the aqueous solution and cement either separated or returned to a water-like state, whereas the aqueous solutions containing sodium polyacrylate and potassium dihydrogen phosphate maintained almost the same viscosity as before the addition of cement, even after the addition of cement. Example 3

[0040] In Example 3, the blending ratio of sodium polyacrylate and sodium dihydrogen phosphate that maintains viscosity even after the addition of cement was investigated.

[0041] In each beaker, 1g of sodium polyacrylate powder and 0.5, 0.8, 1.0, 1.13, 2.0, and 3.3g of sodium dihydrogen phosphate powder were placed and mixed uniformly, then 100g of water was added and stirred well to dissolve the powder. For samples containing 0.5, 0.8, or 1.0g of sodium dihydrogen phosphate powder, sodium polyacrylate was dissolved in 10g of ethanol, potassium dihydrogen phosphate was added and stirred, and water was added and stirred to dissolve.

[0042] Next, 40 g of cement (powder) was added to both aqueous solutions and thoroughly stirred in the same manner as in Example 1. Then, whether the viscosity was maintained even after the addition of the cement was visually evaluated.

[0043] The results are shown in Table 3. In the table, "No. 6" indicates the result of evaluating whether the viscosity was maintained for a sample in which 0.5 g of sodium dihydrogen phosphate was dissolved, "No. 7" indicates the result for a sample in which 0.8 g of sodium dihydrogen phosphate was dissolved in water, "No. 8" indicates the result for a sample in which 1.0 g of sodium dihydrogen phosphate was dissolved in water, "No. 9" indicates the result for a sample in which 1.13 g of sodium dihydrogen phosphate was dissolved in water, "No. 10" indicates the result for a sample in which 2.0 g of sodium dihydrogen phosphate was dissolved in water, and "No. 11" indicates the result for a sample in which 3.3 g of sodium dihydrogen phosphate was dissolved in water. The standards for viscosity evaluation were the same as those in Example 1. [Table 3]

[0044] As shown in Table 3, in samples in which 0.8-2.0g of sodium dihydrogen phosphate was added to 1g of sodium polyacrylate, the viscosity was maintained after the addition of cement at approximately the same level as before the addition of cement. This result suggests that the suitable mixing ratio of sodium polyacrylate and sodium dihydrogen phosphate, which maintains viscosity even after the addition of cement, is, by weight, 1 part sodium polyacrylate to 0.6 parts sodium dihydrogen phosphate or more, and the upper limit, in the case of sodium dihydrogen phosphate, is preferably 1 part sodium polyacrylate to 3.0 parts sodium dihydrogen phosphate or less. Example 4

[0045] In Example 4, it was verified whether a solution in which sodium polyacrylate and sodium dihydrogen phosphate were dissolved could actually suppress blockage of the pipes of a concrete pump truck.

[0046] 50g of sodium polyacrylate powder and 50g of sodium dihydrogen phosphate powder were mixed uniformly, and then the mixed powder was added to 100g of ethanol and thoroughly stirred to obtain a uniform dispersion. This dispersion was added to 15L of water and thoroughly stirred to obtain a uniform solution.

[0047] 15 L of this solution was poured into the hopper of a concrete pump truck (piping outer diameter 5 inches (approximately 12.7 cm), total length 26 m), and the pressure pump was started to pump the solution into the pump and piping. This liquid transfer was performed smoothly without any unstable liquid transfer.

[0048] Next, 5m of ready-mix concrete is poured into the hopper. 3 The concrete was continuously pumped through the pipe by starting the pump, and the concrete was circulated in the pipe. As a result, the entire pipe was filled with the concrete.

[0049] In this example, the pumping of the ready-mixed concrete was performed smoothly without unstable liquid conditions because a solution of sodium polyacrylate and sodium dihydrogen phosphate was pumped into the pipes beforehand. Furthermore, no blockages occurred in the pipes during the pumping of the ready-mixed concrete, and no signs of blockages were found. The same was true when the inside of the pipes was checked during disassembly and cleaning of the pipes after pumping the ready-mixed concrete.

[0050] These results suggest that by using a solution of sodium polyacrylate and sodium dihydrogen phosphate with a concentration of approximately 3.33 g / L (e.g., 0.5 to 50 g / L) as a pre-mixing agent for pumping ready-mixed concrete, clogging of pipes in concrete pump trucks can be effectively suppressed. Example 5

[0051] In Example 5, salts other than those used in Example 2 were examined in the same manner as in Example 2.

[0052] In addition to the salt-free sample (control), the following salts were prepared: (1) sodium dihydrogen phosphate powder (comparative example), (2) sodium bicarbonate powder, (3) trisodium citrate powder, (4) a mixture of sodium dihydrogen phosphate powder and trisodium citrate powder (weight ratio 1:1), (5) a mixture of sodium dihydrogen phosphate powder and trisodium citrate powder (weight ratio 3:2), and (6) a mixture of sodium dihydrogen phosphate powder and trisodium citrate powder (weight ratio 4:1). 2 g of sodium polyacrylate powder and 5 g of each salt powder were placed in a beaker and mixed uniformly, then 200 g of water was added and thoroughly stirred to dissolve the powder. As a result, all aqueous solutions showed strong viscosity.

[0053] Next, 80 g of cement (powder) was added to each aqueous solution and thoroughly stirred. Whether the viscosity was maintained after the addition of cement was then visually evaluated.

[0054] The results are shown in Table 4. In the table, "Control" indicates the result of evaluating whether the viscosity was maintained for a sample in which only sodium polyacrylate was dissolved in water, "No. 12" indicates the result of evaluating whether the viscosity was maintained for a sample in which sodium polyacrylate and sodium dihydrogen phosphate were dissolved in water, "No. 13" indicates the result of evaluating whether the viscosity was maintained for a sample in which sodium polyacrylate and sodium bicarbonate were dissolved in water, "No. 14" indicates the result of evaluating whether the viscosity was maintained for a sample in which sodium polyacrylate and trisodium citrate were dissolved in water, and "No. 15" indicates the result of evaluating whether the viscosity was maintained for a sample in which sodium polyacrylate and sodium dihydrogen phosphate were dissolved in water. "No. 16" shows the result of evaluating whether the viscosity was maintained for a sample prepared by dissolving in water a mixture of sodium polyacrylate, sodium dihydrogen phosphate, and trisodium citrate in a weight ratio of 3:2, and "No. 17" shows the result of evaluating whether the viscosity was maintained for a sample prepared by dissolving in water a mixture of sodium polyacrylate, sodium dihydrogen phosphate, and trisodium citrate in a weight ratio of 4:1. The viscosity evaluation criteria are the same as those in Example 1. [Table 4]

[0055] As shown in Table 4, the aqueous solution (No. 13) containing sodium polyacrylate and sodium bicarbonate maintained its viscosity particularly well even after the addition of cement, and the viscosity remained smooth without forming lumps even after time had passed. In addition, the aqueous solution (No. 14) containing sodium polyacrylate and trisodium citrate, and the aqueous solutions (Nos. 15-17) containing sodium polyacrylate, sodium dihydrogen phosphate, and trisodium citrate, maintained almost the same viscosity even after the addition of cement as before the addition of cement. In addition, in the aqueous solution (No. 12) containing sodium polyacrylate and sodium dihydrogen phosphate, sodium polyacrylate and sodium dihydrogen phosphate were mixed in a weight ratio of 1:2.5 in this embodiment, and the viscosity evaluation generally corresponds to that of Example 3 (Table 3).

Claims

1. Sodium polyacrylates and salts (excluding disodium succinate and disodium citrate. ) as an active ingredient in this pre-mix concrete pumping agent.

2. 2. The premixing agent for pumping ready-mixed concrete according to claim 1, wherein the sodium polyacrylate and the salt are in the form of a mixed powder or an aqueous solution thereof.

3. Sodium polyacrylates and salts (excluding disodium succinate and disodium citrate. A method for pumping ready-mixed concrete, comprising the step of pumping a solution containing the above-mentioned compound as an active ingredient prior to the ready-mixed concrete.

4. 4. The ready-mixed concrete pumping method according to claim 3, wherein the concentration of the sodium polyacrylate and the salt in the solution is 0.5 to 50 g / L, respectively.

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