JP7570035B2 - Pre-mixed concrete pumping agent and ready-mixed concrete pumping method - Google Patents

Description

The present invention relates to 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, which includes a step of pumping a solution containing the pre-mixing agent prior to the ready-mixed concrete.

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 construction and civil engineering works such as buildings, dams, bridges, and port facilities.

In most cases, concrete structures are constructed in a batcher plant (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, left to harden for a certain period of time, after which the forms are removed.

A concrete pump truck is a vehicle used to pour ready-mixed concrete into forms 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 is supplied to the hopper of a concrete pump truck or the like from an agitator truck, and is pumped through long piping until it is poured into the formwork.

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 pipe is filled with ready-mixed concrete, only the cement and other substances will adhere to the inner wall surface from the front of the pipe first, and only the gravel and other concrete components will reach the outlet side of the pipe, which can easily result in accidents where the pipe becomes clogged with gravel and the ready-mixed concrete cannot be pumped. For this reason, as a pretreatment, cement paste or mortar is generally pumped into the pipe before pumping the ready-mixed concrete, covering the inner wall surface of the pipe with cement paste or mortar, and then the ready-mixed concrete is pumped continuously to prevent the pipe from becoming clogged (see Patent Document 1, for example).

However, when pretreating with 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, because cement paste or mortar are also components of ready-mix concrete, pretreating with them causes a hardening reaction to proceed between pretreating and pumping the ready-mix concrete, making it difficult to precisely predict and control the quality of the concrete after it is poured.

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.
Japanese Patent Publication No. 8-1643 JP 2000-34461 A JP 2020-1586931 A JP 2008-74086 A

When using a thickener as an alternative to cement paste or mortar as a pretreatment agent in pre-treatment for pumping ready-mix concrete with a concrete pump truck, etc., 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.

The present invention aims to provide a simple, inexpensive, and effective means for preventing blockages in pipes, etc., when pumping ready-mixed concrete using a concrete pump truck, etc.

The inventors have newly discovered that the reason why thickening agents, etc., used as pre-agents for pumping fresh concrete in concrete pump trucks, etc., cannot sufficiently prevent blockages in pipes, etc., is that when pumping of fresh concrete begins, the viscosity of the thickening agent is lost through contact with the fresh concrete, and the coating layer that had formed on the inner wall of the pipe disappears due to the flow of the pre-agent. The inventors have also newly discovered that by mixing a specific salt with sodium polyacrylate, the viscosity of the solution can be maintained after pumping of the fresh concrete begins until the entire pipe is filled with fresh concrete, that is, the coating layer formed on the inner wall of the pipe can be maintained after pumping of the fresh concrete until the entire pipe is filled with fresh concrete, and the effect of preventing pipe blockages as a pre-treatment when pumping fresh concrete can be improved.

The present invention provides a pre-mixing agent for pumping ready-mixed concrete that contains sodium polyacrylate and a salt as active ingredients, and the salt is one or more of sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium bicarbonate, and trisodium citrate, and a method for pumping ready-mixed concrete that uses the pre-mixing agent.

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 an advance agent is circulated through the pipes, so that the inner walls of the pipes are 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 pipe is filled with fresh concrete. Therefore, by adopting this technology as a pretreatment when pumping fresh concrete, clogging of pipes etc. can be easily, inexpensively and effectively suppressed.

Pretreatment using this invention makes it possible to easily, inexpensively, and effectively prevent blockages in pipes and other areas when pumping ready-mix concrete using concrete pump trucks, etc.

<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.

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

The salt according to the present invention is any one or more of sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium bicarbonate, and trisodium citrate (a mixture of two or more of these), and any known salt can be used. The present invention broadly includes salts that contain at least one of these salts.

The prior agent according to the present invention may be in the form of a mixed powder in which sodium polyacrylate powder and salt powder are mixed until they are substantially uniform, or in the form of an aqueous solution in which these powders are dissolved in water.

In addition, the prior agent of the present invention also broadly includes those obtained by dissolving these powders in a water-soluble organic solvent, or those further diluted with water.

A wide variety of known water-soluble organic solvents can be used, and there are no narrow limitations.

Examples of water-soluble organic solvents 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, dimethylsulfoxide, 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.

In addition, the prior art agents of the present invention broadly include those to which other known compounds have been added as appropriate depending on the purpose and application, such as improving the solubility of powders and maintaining and stabilizing the quality of solutions.

The mixing ratio of sodium polyacrylate to salt is not narrowly limited within the range that is 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 salt mixing ratio can be appropriately determined taking into consideration the raw material price of the 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 or less, and more preferably 5.0 or less. However, if the salt is sodium dihydrogen phosphate, the range of 1 part sodium polyacrylate to 3.0 parts sodium dihydrogen phosphate or less is preferable.

<Method for 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.

Pumping ready-mixed concrete includes, for example, (1) a process in which a precursor agent is added to a concrete pump truck, etc., and the precursor agent is pumped into the pump and piping, etc., (2) a process in which the ready-mixed concrete is pumped after pretreatment with the precursor agent, and the ready-mixed concrete is filled into the piping, (3) a process in which the fresh concrete pumped initially is recovered so that the precise composition of the concrete to be poured is not changed by the mixing of the precursor agent, and (4) a process in which the ready-mixed concrete is actually poured into the formwork.

In the process of introducing and delivering the precursor agent, it is sufficient to be able to circulate a solution containing at least sodium polyacrylate and a specified salt as active ingredients through the pump and piping of a concrete pump truck, and any known means can be widely adopted and is not narrowly limited.

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.

The concentration of sodium polyacrylate and salt in this solution is not narrowly limited, so long as it is within a range in which clogging of pipes, etc. can be effectively suppressed by pretreatment. 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-mix concrete by a concrete pump truck, etc. can be effectively suppressed.

The amount of this solution to be poured in can be set appropriately depending on the diameter and overall length of the concrete pump truck's piping, and is not narrowly limited as long as the pretreatment effectively prevents clogging of the piping. In the case of a concrete pump truck's piping with an outer diameter of 5 inches (approximately 12.7 cm) and an overall length of approximately 11 to 40 m, for example, clogging of the concrete pump truck's piping can be effectively prevented by pumping 1 to 500 L, more preferably 5 to 100 L, and most preferably 8 to 50 L of the solution with the above concentration as pretreatment with the precursor agent.

In Example 1, we investigated whether the viscosity of an aqueous solution containing dissolved sodium polyacrylate and sodium dihydrogen phosphate would be maintained when cement was added to the solution.

1g of sodium polyacrylate powder and 1g of sodium dihydrogen phosphate powder were placed in a beaker and mixed until uniform, after which 100g of water was added and thoroughly stirred to dissolve the powder. As a control, 1g of sodium polyacrylate powder was dissolved in 100g of water. As a result, both aqueous solutions showed roughly the same strong viscosity.

Next, 40 g of cement (powder) was added to both aqueous solutions and thoroughly stirred. Then, whether the viscosity was maintained after adding the cement was evaluated visually.

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.

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 even after the addition of cement as before.

These results suggest that the reason why using a sodium polyacrylate solution as a pre-mixing agent for pumping fresh concrete was not enough to prevent pipe clogging is because the sodium polyacrylate solution loses its viscosity when the fresh concrete is pumped, causing the coating that had formed on the inner walls of the pipe to disappear. They also suggest 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 walls of the pipe can be maintained after the fresh concrete is pumped until the entire pipe is filled with fresh concrete, thereby improving the effectiveness of preventing pipe clogging as a pre-treatment when pumping fresh concrete.

In Example 2, we investigated whether the viscosity of the aqueous solution would be maintained when cement was added to the aqueous solution containing salts other than sodium polyacrylate and sodium dihydrogen phosphate.

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

Next, 40 g of cement (powder) was added to each aqueous solution and thoroughly stirred. Then, it was visually evaluated whether the viscosity was maintained after the addition of cement.

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.

As shown in Table 2, in the aqueous solution in which sodium polyacrylate and disodium citrate or disodium succinate were dissolved, the viscosity was almost completely lost by adding cement, and the aqueous solution and cement either separated or returned to a water-like state, whereas in the aqueous solution in which sodium polyacrylate and potassium dihydrogen phosphate were dissolved, the viscosity remained almost the same even after the addition of cement as before the addition of cement.

In Example 3, we investigated the mixing ratio of sodium polyacrylate and sodium dihydrogen phosphate that would maintain viscosity even after adding cement.

1 g of sodium polyacrylate powder and 0.5, 0.8, 1.0, 1.13, 2.0, or 3.3 g of sodium dihydrogen phosphate powder were placed in each beaker and mixed until uniform, after which 100 g of water was added and thoroughly stirred to dissolve the powder. For samples containing 0.5, 0.8, or 1.0 g of sodium dihydrogen phosphate powder, the sodium polyacrylate was dissolved in 10 g of ethanol, potassium dihydrogen phosphate was added and stirred, and water was added and stirred to dissolve.

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

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.

As shown in Table 3, in samples where 0.8-2.0g of sodium dihydrogen phosphate was added to 1g of sodium polyacrylate, the viscosity remained almost the same as before the addition of cement, even after the addition of cement. This result suggests that the optimal 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 1 part sodium polyacrylate to 3.0 parts sodium dihydrogen phosphate or less.

In Example 4, we verified whether a solution containing sodium polyacrylate and sodium dihydrogen phosphate could actually prevent blockages in the pipes of a concrete pump truck.

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 stirred well to obtain a uniform dispersion. This dispersion was added to 15L of water and stirred well to obtain a uniform solution.

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

Next, ⁵ m3 of ready-mixed concrete was poured into the hopper, the pressure pump was started, and the ready-mixed concrete was continuously pumped and circulated in the pipe. As a result, the entire pipe was filled with ready-mixed concrete.

In this example, the pumping of the ready-mixed concrete was carried out smoothly without any unstable liquid conditions because a solution of dissolved sodium polyacrylate and sodium dihydrogen phosphate was pumped into the pipes beforehand. Furthermore, during this pumping of ready-mixed concrete, no blockages occurred in the pipes, 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 of the ready-mixed concrete.

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-mix concrete, clogging of pipes in concrete pump trucks can be effectively prevented.

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

In addition to the salt-free sample (control), the following salts were prepared: (1) sodium dihydrogen phosphate powder (comparison 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, after which 200 g of water was added and thoroughly stirred to dissolve the powder. As a result, all aqueous solutions showed strong viscosity.

Next, 80 g of cement (powder) was added to each aqueous solution and thoroughly stirred. Then, it was visually evaluated whether the viscosity was maintained after the addition of cement.

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.

As shown in Table 4, the aqueous solution containing sodium polyacrylate and sodium bicarbonate (No. 13) 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 containing sodium polyacrylate and trisodium citrate (No. 14) and the aqueous solutions containing sodium polyacrylate, sodium dihydrogen phosphate, and trisodium citrate (Nos. 15-17) maintained almost the same viscosity even after the addition of cement as before the addition of cement. In addition, in this embodiment, sodium polyacrylate and sodium dihydrogen phosphate were mixed in a weight ratio of 1:2.5 for the aqueous solution containing sodium polyacrylate and sodium dihydrogen phosphate (No. 12), and the viscosity evaluation generally corresponds to that of Example 3 (Table 3).

Claims (4)

Contains sodium polyacrylate and salt as active ingredients,
The salt is one or more of sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium bicarbonate, and trisodium citrate. 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. Contains sodium polyacrylate and salt as active ingredients,
A method for pumping ready-mixed concrete, comprising the step of pumping a solution in which the salt is any one or more of sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium bicarbonate, and trisodium citrate prior to the ready-mixed concrete. The method for pumping ready-mixed concrete according to claim 3, wherein the concentration of the sodium polyacrylate and salt in the solution is 0.5 to 50 g/L, respectively.