JP7751049B2 - 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 bicarbonate, 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 due to its strength and ease of construction, it is widely used as a structural material in construction and civil engineering projects such as buildings, dams, bridges, and port facilities.

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-mixed concrete, which is then transported to the construction site while being mixed in an agitator truck (mixer truck).The ready-mixed concrete is then poured (placed) into formwork using a concrete pump truck, left to harden for a certain period of time, and the formwork is then removed.

A concrete pump truck is a vehicle used to pour ready-mixed concrete into formwork at a construction site. Its main components for pumping ready-mixed concrete are a hopper, a pressure pump, and piping. Ready-mixed concrete is supplied from an agitator truck to the hopper of a concrete pump truck or other vehicle, and is pumped through long piping until it is poured into the formwork.

When pumping ready-mixed concrete using a concrete pump truck or similar device, if pumping begins without any pre-treatment, before the entire pipe is filled with ready-mixed concrete, only cement and other materials will adhere to the inner wall surface from the front of the pipe. As a result, only concrete components such as gravel will reach the outlet of the pipe. This 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 pre-treatment, cement paste or mortar is generally pumped into the pipe before pumping the ready-mixed concrete, coating the inner wall surface of the pipe with the cement paste or mortar. Then, ready-mixed concrete is continuously pumped, preventing the pipe from becoming clogged (see, for example, Patent Document 1).

However, when pre-treating with cement paste or mortar, a relatively large amount of cement paste must be used to coat the inner wall surface of the pipe, which is costly and cumbersome. Furthermore, because cement paste and mortar are also components of ready-mixed concrete, pre-treating with them means that the hardening reaction continues even between pre-treatment and pumping the ready-mixed concrete, making it difficult to precisely predict and control the quality of the concrete after it has been poured.

Therefore, various methods have been proposed that can serve as alternatives to pretreatment with cement paste or mortar. For example, Patent Document 2 describes a concrete 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 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 Application Publication No. 8-1643 Japanese Patent Application Laid-Open No. 2000-34461 Japanese Patent Application Publication No. 2020-1586931 Japanese Patent Application Laid-Open No. 2008-74086

When using thickeners as pre-agents as an alternative to cement paste or mortar in pre-treatment before pumping ready-mixed concrete using concrete pump trucks, etc., it is possible to simplify the process and reduce costs compared to using cement paste or mortar, but it has not been found that this method can sufficiently prevent blockages in pipes, etc.

The present invention therefore 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 use of thickeners as precursors for pumping fresh concrete in concrete pump trucks and other vehicles fails to adequately prevent pipe clogging. This is because, when pumping fresh concrete begins, the thickener loses its viscosity upon contact with the fresh concrete, and the coating layer that had formed on the inner wall of the pipe disappears as the precursor agent flows. 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 fresh concrete begins until the entire pipe is filled with fresh concrete. In other words, the coating layer that has formed on the inner wall of the pipe can be maintained after pumping fresh concrete until the entire pipe is filled with fresh concrete, thereby improving the effectiveness of preventing pipe clogging as a pretreatment before pumping fresh concrete.

The present invention therefore 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 bicarbonate, and trisodium citrate, as well as a method for pumping ready-mixed concrete using the same.

Prior to pumping fresh concrete using a concrete pump truck or similar device, a solution containing sodium polyacrylate and a specified salt as its active ingredients is circulated through the pipe as a precursor agent. This allows the viscous solution to coat the inner walls of the pipe, forming a coating layer. Even after pumping of the fresh concrete begins, the viscosity of the solution is maintained, and the coating layer is preserved, until the entire pipe is filled with fresh concrete. Therefore, by using this technology as a pretreatment before pumping fresh concrete, clogging of pipes and other structures can be easily, inexpensively, and effectively prevented.

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

<Regarding the pre-mixing agent for pumping ready-mixed concrete according to the present invention>
The present invention broadly encompasses a pre-mixing agent 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, a polymer of acrylic acid, and a wide variety of known sodium polyacrylates can be used.

The salt according to the present invention is one or more of sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium bicarbonate, and trisodium citrate (a mixture of two or more of these), and a wide variety of known salts can be used. The present invention also broadly encompasses products containing at least one of these.

The prior art 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.

Furthermore, those powders dissolved in water-soluble organic solvents, or those further diluted with water, are also broadly included in the precursor agents of the present invention.

A wide range of known water-soluble organic solvents can be used and are not narrowly limited.

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, dimethyl sulfoxide, sulfolane, propylene carbonate, diethylene glycol ethyl methyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, and triethylene glycol. Other suitable solvents include ethylene glycol diethyl ether, diethylene glycol dibutyl ether, and triethylene glycol butyl methyl ether, as well as 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 precursor 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 or maintaining and stabilizing the quality of solutions.

The mixing ratio of sodium polyacrylate to salt is not narrowly limited, as long as it is within the range that is effective as a pre-mixing agent for pumping ready-mixed concrete. For example, a weight ratio of 1 part sodium polyacrylate to at least 0.6 parts salt can effectively prevent blockages in pipes when pumping ready-mixed concrete using a concrete pump truck or similar device. The upper limit of the salt mixing ratio can be determined appropriately taking into account factors such as the raw material price of the salt, and is not particularly limited. For example, a weight ratio of 1 part sodium polyacrylate to 10 parts salt or less, preferably 7.0 or less, and more preferably 5.0 or less, may be used. However, if the salt is sodium dihydrogen phosphate, a range of 1 part sodium polyacrylate to 3.0 parts sodium dihydrogen phosphate or less is preferred.

<Method for pumping ready-mixed concrete according to the present invention>
The present invention encompasses 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 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, the inclusion of other steps. Note that the "solution containing sodium polyacrylate and a salt" here broadly encompasses, for example, the above-mentioned.

Preparation of ready-mixed concrete involves, for example, (1) adding a precursor agent to a concrete pump truck and pumping the agent into the pump and piping, (2) pre-treating the ready-mixed concrete with the precursor agent, then pumping it into the piping, (3) recovering the ready-mixed concrete that was pumped initially so as not to change the exact composition of the concrete to be poured due to the inclusion of the precursor agent, and (4) actually pouring the ready-mixed concrete into the formwork.

Of these, the process of adding and delivering the precursor agent only requires that a solution containing at least sodium polyacrylate and a specified salt as active ingredients be circulated through the pump and piping of a concrete pump truck, and any known method can be widely adopted, with no narrow limitations.

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

The concentration of sodium polyacrylate and salt in this solution is not narrowly limited, as long as it is within a range that can effectively prevent clogging of pipes, etc. through pretreatment. For example, when the above-mentioned blending 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 using a concrete pump truck, etc. can be effectively prevented.

The amount of solution added can be set appropriately depending on the diameter and total length of the concrete pump truck's piping, and is not narrowly limited as long as it can effectively prevent clogging of the piping through pretreatment. For example, if the outer diameter of the concrete pump truck's piping is 5 inches (approximately 12.7 cm) and the total length is approximately 11 to 40 m, pretreatment with a precursor agent can be carried out by pumping 1 to 500 L, more preferably 5 to 100 L, and most preferably 8 to 50 L, of a solution with the above-mentioned concentration, to effectively prevent clogging of the concrete pump truck's piping.

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 stirred well to dissolve the powder. As a control, 1g of sodium polyacrylate powder alone was dissolved in 100g of water. As a result, both aqueous solutions exhibited roughly the same strong viscosity.

Next, 40 g of cement (powder) was added to both aqueous solutions and stirred thoroughly. The viscosity was then visually evaluated to see if it was maintained after the addition of the cement.

The results are shown in Table 1. In the table, "No. 1" represents the result of evaluating whether viscosity was maintained for a sample in which only sodium polyacrylate was dissolved in water (control), and "No. 2" represents the result of evaluating whether viscosity was maintained for a sample in which sodium polyacrylate and sodium dihydrogen phosphate were dissolved in water. Viscosity was evaluated on a four-point scale, with "×" representing a case in which the viscosity was lost and the sample returned to a nearly water-like state after the addition of cement, "△" representing a case in which the sample retained some viscosity but returned to a nearly water-like state, "◯" representing a case in which a certain viscosity was maintained, and "◎" representing a case in which the viscosity was maintained at approximately the same level as before the addition of cement.

As shown in Table 1, in the case of an aqueous solution containing only sodium polyacrylate, the addition of cement caused the solution to lose viscosity and return to an almost water-like state, whereas in the case of an aqueous solution containing sodium polyacrylate and sodium dihydrogen phosphate, the solution maintained a viscosity almost equal to that before the addition of cement, even after the addition of cement.

These results suggest that the reason why using a sodium polyacrylate solution as a pre-mixing agent for pumping fresh concrete was unable to sufficiently 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. The results also suggest that by mixing sodium dihydrogen phosphate with sodium polyacrylate, the viscosity of the solution can be maintained even after the fresh concrete has been pumped. In other words, the coating that had formed on the inner walls of the pipe can be maintained after the fresh concrete has been 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 an aqueous solution would be maintained when cement was added to the aqueous solution containing salts other than sodium polyacrylate and sodium dihydrogen phosphate.

Salts other than sodium dihydrogen phosphate were prepared: disodium citrate, disodium succinate, and potassium dihydrogen phosphate. As in Example 1, 1 g of sodium polyacrylate powder and 1 g of each salt powder were placed in each beaker and mixed until uniform. 100 g of water was then added and the mixture was stirred thoroughly to dissolve the powder. As a result, all of the aqueous solutions exhibited strong viscosity.

Next, 40 g of cement (powder) was added to each aqueous solution and stirred thoroughly. The solution was then visually evaluated to see if viscosity was maintained after the addition of cement.

The results are shown in Table 2. In the table, "No. 3" represents the result of evaluating whether viscosity was maintained for a sample prepared by dissolving sodium polyacrylate and disodium citrate in water, "No. 4" represents the result of evaluating whether viscosity was maintained for a sample prepared by dissolving sodium polyacrylate and disodium succinate in water, and "No. 5" represents the result of evaluating whether viscosity was maintained for a sample prepared by dissolving sodium polyacrylate and potassium dihydrogen phosphate in water. The viscosity evaluation criteria were the same as in Example 1.

As shown in Table 2, in the case of aqueous solutions containing sodium polyacrylate and disodium citrate or disodium succinate, the viscosity was almost completely lost upon addition of cement, and the solution either separated from the cement or returned to a water-like state. In contrast, in the case of aqueous solutions containing sodium polyacrylate and potassium dihydrogen phosphate, the viscosity remained roughly the same even after the addition of cement as it was before the addition of cement.

In Example 3, we investigated the blend 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. 100 g of water was then added and stirred thoroughly 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, then potassium dihydrogen phosphate was added and stirred, and water was then 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, a visual evaluation was performed to see if viscosity was maintained after the addition of cement.

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

As shown in Table 3, samples in which 0.8-2.0g of sodium dihydrogen phosphate was added to 1g of sodium polyacrylate maintained roughly the same viscosity as before the addition of cement, even after the addition of cement. These results suggest that the ideal ratio of sodium polyacrylate to sodium dihydrogen phosphate, which maintains viscosity even after the addition of cement, is a weight ratio of 1 part sodium polyacrylate to 0.6 or more parts sodium dihydrogen phosphate, and in the case of sodium dihydrogen phosphate, the upper limit is a range of 1 part sodium polyacrylate to 3.0 or less parts sodium dihydrogen phosphate.

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

50g of sodium polyacrylate powder and 50g of sodium dihydrogen phosphate powder were mixed until uniform, then the mixed powder was added to 100g of ethanol and stirred thoroughly to obtain a uniform dispersion. This dispersion was then added to 15L of water and stirred thoroughly 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, sending the solution through the pump and piping. This transfer was carried out smoothly, without any unstable liquid transfer conditions.

Next, 5 ^m3 of ready-mixed concrete was poured into the hopper, and the pressure pump was started to continuously pump the ready-mixed concrete, causing it to circulate through the pipe. As a result, the entire pipe was filled with ready-mixed concrete.

In this example, the pumping of ready-mixed concrete was carried out smoothly without any unstable liquid conditions because a solution containing dissolved sodium polyacrylate and sodium dihydrogen phosphate was pumped into the pipes beforehand. Furthermore, no blockages occurred inside the pipes during this pumping of ready-mixed concrete, and no signs of blockages were found. The same was true when the inside of the pipes was inspected after the pumping of ready-mixed concrete by disassembling and cleaning them.

These results suggest that using a solution of sodium polyacrylate and sodium dihydrogen phosphate with a concentration of around 3.33 g/L (e.g., 0.5 to 50 g/L) as a pre-mixing agent for pumping ready-mixed concrete can effectively prevent blockages in pipes of concrete pump trucks, etc.

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 mixed powder of sodium dihydrogen phosphate powder and trisodium citrate powder (weight ratio 1:1), (5) a mixed powder of sodium dihydrogen phosphate powder and trisodium citrate powder (weight ratio 3:2), and (6) a mixed powder of sodium dihydrogen phosphate powder and trisodium citrate powder (weight ratio 4:1). 2g of sodium polyacrylate powder and 5g of each salt powder were placed in a beaker and mixed until homogeneous. 200g of water was then added and the mixture was stirred thoroughly to dissolve the powder. All aqueous solutions exhibited strong viscosity.

Next, 80 g of cement (powder) was added to each aqueous solution and stirred thoroughly. The solution was then visually inspected to see if viscosity was maintained after the addition of the cement.

The results are shown in Table 4. In the table, "Control" indicates the result of evaluating whether viscosity was maintained for a sample in which only sodium polyacrylate was dissolved in water, "No. 12" indicates the result of evaluating whether 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 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 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 viscosity was maintained for a sample in which sodium polyacrylate and trisodium citrate were dissolved in water. "No. 16" shows the results of an evaluation of whether 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 results of an evaluation of whether 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 were the same as 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 remained smooth over time without forming lumps. Furthermore, 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 approximately the same viscosity after the addition of cement as before. Regarding the aqueous solution containing sodium polyacrylate and sodium dihydrogen phosphate (No. 12), in this example, sodium polyacrylate and sodium dihydrogen phosphate were mixed in a weight ratio of 1:2.5, and its viscosity evaluation generally corresponds to that of Example 3 (Table 3).

Claims (4)

A precursor agent that is administered as a solution containing an active ingredient,
The active ingredient contains sodium polyacrylate and its salts (excluding sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium bicarbonate, trisodium citrate, disodium succinate, and disodium citrate) ,
A pre-mixed concrete pumping agent that can maintain a coating layer formed on the inner wall of a pipe by the flow of the pre-mixed concrete until the entire pipe is filled with the pre-mixed concrete after the pre-mixed concrete is pumped . The pre-mixing 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. The method includes a step of delivering a solution containing sodium polyacrylate and a salt (excluding sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium bicarbonate, trisodium citrate, disodium succinate, and disodium citrate) as an active ingredient prior to the addition of the ready-mix concrete ;
A method for pumping ready-mixed concrete that can maintain a coating layer formed on the inner wall of a pipe by the flow of a pre-mixing agent until the entire pipe is filled with ready-mixed concrete after pumping the ready-mixed concrete . The ready-mixed concrete pumping method according to claim 3, wherein the concentration of the sodium polyacrylate and salt in the solution is 0.5 to 50 g/L, respectively.