JP7593574B2 - 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, the active ingredient of which is crushed sand with a particle size of 1 to 1,000 μm, and a method for pumping ready-mixed concrete, which includes a step of mixing the pre-mixing agent with water and pumping the mixture prior to the ready-mixed concrete.

Concrete is a material made by solidifying coarse aggregate (such as gravel), fine aggregate (such as sand), and water with cement. Due to 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).

Also, various means that can be used as substitutes for 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 cement paste or mortar as a pretreatment agent for pumping ready-mixed concrete with a concrete pump truck or the like, it is necessary to use a relatively large amount of cement paste, which is costly and cumbersome. On the other hand, when a thickener or the like is used as a pretreatment 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.

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 present invention provides a pre-mixing agent for pumping ready-mixed concrete, the active ingredient of which is crushed sand with a particle size of 1 to 1,000 μm, and a method for pumping ready-mixed concrete using the agent.

This precursor agent can be obtained, for example, by crushing natural rocks. The crushed sand obtained by crushing has a particle size of 1 to 1,000 μm, and is angular and non-spherical. Therefore, by mixing it with water, a mixture with the appropriate viscosity can be prepared. Therefore, prior to pumping fresh concrete with a concrete pump truck or the like, such crushed sand can be mixed with water as a precursor agent and then circulated in the pipes in advance. This makes it possible to simply, effectively, and sufficiently prevent blockages in the pipes, etc., even after pumping of the fresh concrete has begun, until the entire pipes are filled with fresh concrete.

The crushed sand in this precursor agent also contains fine particles of 150 μm or less, which contributes to the appropriate viscosity when mixed with water. In addition, this precursor agent has the advantage of being easy and inexpensive to manufacture, since there is no need to take the trouble of removing these fine particles when producing crushed sand. In addition, this type of fine particle in crushed sand, which previously had almost no use and was discarded or disposed of, can now be used without removal, making it useful from the perspective of effective resource utilization and waste reduction.

In addition, the present invention is extremely useful and effective in that it can prevent blockages even in thinner and longer pipes than those normally used.

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, as an active ingredient, crushed sand having a particle size of at least 1 to 1,000 μm.

Crushed sand includes all crushed natural rocks. In principle, it also broadly includes sand-like materials with a specific particle size and non-spherical particle shape, and is not narrowly limited to only those derived from natural rocks or sand-like materials obtained by crushing.

A wide variety of known natural rocks can be used as the raw material for crushed sand, and there are no particular limitations. For example, sandstone, granite, basalt, andesite, diabase, limestone, diorite, shale, etc. may be used.

The chemical composition of the crushed sand is not particularly limited as long as it has the same composition as crushed natural rocks. For example, the crushed sand may contain 50-85% _SiO2 , 5-20 _{% Al2O3} , and 0.1-5.0 _{% Fe2O3} , with the total content not exceeding 100%.

The method for producing crushed sand can be a wide variety of known methods and is not particularly limited. For example, natural rocks are crushed using a crusher or grinder, and then the crushed sand can be produced by a dry production method in which the natural rocks are crushed using a crusher or grinder, and then the crushed sand is heated and dried using a boiler or the like, sieved, and collected using a dust collector. By producing crushed sand using a dry production method, it is possible to produce crushed sand that contains fine particles of 150 μm or less.

The crushed sand that is the active ingredient of the pre-pumping agent for ready-mix concrete of the present invention is an accumulation of crushed sand with various particle sizes, but the particle sizes are preferably in the range of 1 to 1,000 μm, more preferably in the range of 1 to 800 μm, and most preferably in the range of 1 to 500 μm.

When crushed sand contains fine particles of 150 μm or less (1-150 μm) or 75 μm or less (1-75 μm), these also contribute to the appropriate viscosity when mixed with water. In addition, when this method is adopted, it becomes unnecessary to remove the fine particles when producing crushed sand, so the desired crushed sand can be produced easily and inexpensively. Furthermore, since the fine particles in such crushed sand, which have traditionally had little use and were discarded or disposed of, can be used without removal, it is also useful from the perspective of effective use of resources and reduction of waste.

The average particle size (volume average size) of the crushed sand including fine particles is preferably 10 to 300 μm, more preferably 10 to 200 μm, and most preferably 10 to 150 μm. Furthermore, when the average particle size of the crushed sand is within this range, the crushed sand contains fine particles of 150 μm or less (1 to 150 μm) or 75 μm or less (1 to 75 μm).

It is preferable that the particle shape of the crushed sand containing fine particles is non-spherical. When the particles in the crushed sand are non-spherical, the mixture can have an appropriate viscosity when mixed with water, and can be used as a pre-mixing agent for pumping ready-mix concrete.

When the particles are perfectly spherical, the number mean diameter (MN) and the volume mean diameter (MV) are the same for the average particle diameter. On the other hand, when the particles are non-spherical, the number mean diameter and the volume mean diameter are different values. Therefore, the difference between the number mean diameter and the volume mean diameter is an indicator of the non-spherical shape of each crushed sand. In the crushed sand according to the present invention, the difference between the number mean diameter and the volume mean diameter is preferably 10 μm or more, more preferably 20 μm or more, and most preferably 30 μm or more. If the particle shape of each crushed sand is approximately spherical, the viscosity may be insufficient, while if the particle shape of each crushed sand is approximately lamellar or approximately flat, the viscosity may be too high. Although it is difficult to analyze the upper limit of the difference between the number mean diameter and the volume mean diameter, it is assumed that, for example, if it is 150 μm or less, more preferably 100 μm or less, the viscosity of the mixture when mixed with water is at least moderately maintained.

In addition, other known compounds may be added to the precursor agent of the present invention as appropriate depending on the purpose and application.

<Method for pumping ready-mixed concrete according to the present invention>
The present invention encompasses all methods for pumping ready-mixed concrete that include a step of mixing any of the above-mentioned pre-mixing agents for pumping ready-mixed concrete with water and pumping the mixture prior to the ready-mixed concrete, and is not narrowly limited, for example, by including other steps.

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.

Of these, the process of adding and pumping the precursor agent involves mixing and stirring the above-mentioned precursor agent for pumping ready-mixed concrete with water, and then circulating the mixture through the pump and piping of a concrete pump truck. Any known means can be widely adopted and is not narrowly limited.

For example, a mixture of the above-mentioned pre-mixed concrete pumping agent and water can be poured into the hopper of a concrete pump truck, and the pump can be started to circulate the mixture through the pump and piping.

The viscosity of a mixture of a pre-mixture agent for pumping ready-mixed concrete and water may be measured, for example, in a slump test using a slump cone with a height of 30 cm, a diameter of 10 cm at the top, and a diameter of 20 cm at the bottom. In the present invention, the slump value of the mixture of a pre-mixture agent for pumping ready-mixed concrete and water is preferably 5 to 25 cm, more preferably 8 to 20 cm, and most preferably 10 to 18 cm.

The mixing ratio of the pre-mixing agent for pumping ready-mixed concrete to the water is not particularly limited and may be determined based on the viscosity of the mixture. For example, a ratio of 1 to 10:1 is preferable, 2 to 8:1 is more preferable, and 2 to 6:1 is most preferable.

The present invention can effectively prevent blockages in pipes on concrete pump vehicles, even when the pipes are thinner than those normally used, for example, when the pipes on concrete pump vehicles have an outer diameter of 4 inches (approximately 10.16 cm). The present invention can also effectively prevent blockages in pipes on concrete pump vehicles, even when the pipes are longer than those normally used, for example, when the pipes have a total length of approximately 200 m.

The amount of the mixture of water and pre-mixed concrete pumping agent can be appropriately set depending on the diameter and overall length of the concrete pump truck's piping, and is not narrowly limited as long as the pre-treatment effectively prevents blockage of the piping. In the case of a concrete pump truck's piping with an outer diameter of 4 inches (approximately 10.16 cm) and an overall length of about 10 m to 250 m, pre-treatment with the pre-mixed concrete agent can be performed by pumping, for example, 1 to 2,500 L, more preferably 5 to 500 L, and most preferably 8 to 250 L of the mixture of the pre-mixed concrete pumping agent and water, thereby effectively preventing blockage of the concrete pump truck's piping.

In Example 1, crushed sand was produced from granite.

The granite was crushed and re-pulverized in a crusher. The resulting crushed material was heated in a boiler (100-140°C), dried, sieved, and collected in a dust collector to obtain crushed sand containing fine particles.

The density of the obtained crushed sand (sample weight 90 g) was measured according to the JIS R 7 density test and found to be 2.64 g/ ^cm3 .

The specific surface area was measured according to JIS A 6201 8.5.2 plain method (specific surface area) and was found to be 3,650 cm ² /g.

The particle size distribution of the crushed sand obtained was measured using the laser diffraction/scattering method. The measuring device used was the "Particle Size Distribution Meter MT3300EX II (Microtrack Bell Co., Ltd.)". The measurement conditions were: measurement range 0.1-700 μm, measurement time 30 seconds, dispersing medium ethyl alcohol, and measurement count 2 times.

The results are shown in Figure 1. Figure 1 is a graph showing the measurement results of particle size distribution, with the horizontal axis representing particle size (unit: μm) and the vertical axis representing frequency (%). In addition, DV was 0.0791, transmittance (TR) was 0.831, particle refractive index was 1.81, solvent refractive index was 1.36, _D10 was 5.821 μm, _D50 (median diameter) was 39.69 μm, _D90 was 130.1 μm, MV (volume mean diameter) was 58.11, MA (area mean diameter) was 16.03 μm, MN (number mean diameter) was 3.183 μm, and SD was 46.94 μm.

As shown in Figure 1, the crushed sand obtained from granite had particle sizes distributed between 1.783 and 418.6 μm, and contained fine particles of 150 μm or less and 75 μm or less. The average particle size (volume mean diameter) was 58.11 μm. In addition, the MN (number mean diameter) was 3.183 μm, while the MV (volume mean diameter) was 58.11 μm, a difference of more than 50 μm between the two, indicating that each crushed sand was non-spherical.

The obtained crushed sand was finely pulverized in a disk mill and subjected to ignition loss at 950°C for 1 hour, after which the components were analyzed by semi-quantitative analysis using a fluorescent X-ray analyzer ZSX Primus IV (Rigaku Corporation). As a result, the ignition loss was 1.50 mass%, _SiO2 was 66.97 mass%, _{Al2O3 was} 16.49 mass%, _{Fe2O3 was} 3.18 mass%, CaO was 1.32 mass%, MgO was 0.12 mass%, _SO3 was 0.01 mass%, _Na2O was 4.53 mass%, _K2O was 5.06 mass%, _TiO2 was 0.17 mass%, _P2O5 was 0.02 mass%, _MnO was 0.08 mass%, Cl was 0.014 mass%, _F was 0.356 mass%, _V2O5 was 0.002 mass%, _Cr2O3 was 0.003 mass% _, NiO was 0.003 mass%, CuO was 0.001 mass%, ZnO was 0.020 mass%, _Ga2O The _mass percentages of _NbO3 were 0.004%, _Rb2O was 0.040%, SrO was 0.003%, _Y2O3 was 0.030%, _ZrO2 was 0.028%, _Nb2O5 was 0.008%, _SnO2 was 0.002%, _BaO was 0.014%, _CeO2 was _0.015 %, _Nd2O3 was 0.008% _{, Gd2O3 was} 0.002%, PbO was 0.006%, and _ThO2 was 0.009%.

In Example 2, the viscosity of the crushed sand obtained in Example 1 was examined.

20 L of the crushed sand obtained in Example 1 and 5 L of water were placed in a 40 L bucket and stirred with a stirrer. The stirred mixture (mixture) was then packed into a slump cone, which was then slowly removed and the slump value was measured. As a result, the slump value was 16.5 cm, indicating that the crushed sand derived from granite obtained had an appropriate viscosity.

In Example 3, we verified whether the use of the crushed sand obtained in Example 1 could actually prevent blockage of the pipes of a concrete pump truck.

As in Example 2, 20 L of crushed sand obtained in Example 1 and 5 L of water were mixed with an agitator, and the mixed material (mixture) was added to the hopper of a concrete pump truck (outer diameter of the pipe: 4 inches (approximately 10.16 cm), total length of the pipe: 200 m) after adding water. The pressure pump was started, and the mixed material was sent into the pump and pipe. This transfer was carried out smoothly without any unstable liquid transfer.

Next, ready-mixed concrete was poured into the hopper, the pump was started, and the ready-mixed concrete was continuously pumped and circulated through the pipe. As a result, the entire pipe was filled with ready-mixed concrete. By pumping the agitated mixture of crushed sand and water according to the present invention into the pipe beforehand, the ready-mixed concrete could be pumped smoothly without the pumping state becoming unstable. Furthermore, during this pumping of ready-mixed concrete, no blockages occurred in the pipe, and no signs of blockages were found. The same was true when the inside of the pipe was checked during disassembly and cleaning of the pipe after pumping of the ready-mixed concrete.

In this way, by mixing crushed sand with a non-spherical particle shape, particle diameters of 1.783 to 418.6 μm, including fine particles of 150 μm or less, and an average particle diameter (volume average diameter) of 58.11 μm as a pre-mixing agent for pumping ready-mixed concrete with water, and pumping it prior to the ready-mixed concrete, it was possible to effectively prevent blockages in the pipes of a concrete pump truck, even when the pipes were thinner and much longer than usual.

Crushed sand is used as an alternative to natural sand used as fine aggregate in making concrete, mortar, etc. Crushed sand is mainly manufactured by dry manufacturing and wet manufacturing. Dry manufacturing makes it relatively easy to produce crushed sand, but produces sand containing a large amount of fine particles with a particle size of 150 μm or less. Crushed sand containing a certain amount of fine particles does not meet the standards for fine aggregate for concrete, so the mainstream method of manufacturing crushed sand is wet manufacturing, which can remove these fine particles. In contrast, the present invention has the advantage that crushed sand containing fine particles of 150 μm or less, which has had little use until now, can be used as a pre-mixing agent for pumping ready-mixed concrete without removing the fine particles, so the dry manufacturing method has the advantage of being easy and inexpensive to manufacture.

In addition, (1) it can utilize the fine particles in crushed sand, which previously had little use and were discarded or disposed of, and (2) by adopting a dry manufacturing method, it can eliminate the generation of polluted water and dehydrated cake that occurs with wet manufacturing methods, making it useful from the perspective of effective use of resources and reduction of waste.

In addition, the premix for pumping ready-mix concrete according to the present invention is simply crushed natural rocks, and in principle does not contain any chemical substances such as thickeners, so it has the advantage of being environmentally friendly and easy to dispose of after use.

Graph showing the measurement results of particle size distribution in Example 1.

Claims (4)

The active ingredient is crushed sand with a particle size of 1 to 1,000 μm.
The crushed sand contains fine particles of 150 μm or less,
The fine-grained sand has an average particle size (volume average diameter) of 10 to 300 μm . 2. The premixed concrete pumping agent according to claim 1 , wherein the particle shape of the crushed sand containing the fine particles is non-spherical. 3. A method for pumping ready-mixed concrete, comprising the steps of: mixing the pre-mixing agent for pumping ready-mixed concrete according to claim 1 or 2 with water; and pumping the mixture prior to the ready-mixed concrete. 4. The method for pumping ready-mixed concrete according to claim 3 , wherein the mixing ratio of the pre-mixing agent for pumping ready-mixed concrete to the water is 2 to 10:1.