JP6844951B2 - Cement-based mixture spraying method - Google Patents

Description

In the present invention, for example, aggregate and cement milk are separately pumped to a mixing means arranged upstream of the spray nozzle, and a cement-based mixture such as mortar or concrete formed by the mixing means is applied from the spray nozzle. The present invention relates to a method of spraying a cement-based mixture suitable for spraying on an object.
In this specification, those containing at least water, cement and aggregate (whether fine aggregate or coarse aggregate) are defined as "cement-based mixture", and those containing at least water and cement are defined as "cement-based mixture". These terms are used by defining "cement fluid" and defining water and cement and optionally cement admixture as "cement milk". That is, "cement fluid" includes both "cement-based mixture" and "cement milk".

The applicant has developed a method for spraying a cement-based mixture (mortar or concrete) in which aggregate and cement milk are separately pumped, and has already proposed various techniques related to this method (for example, Patent Documents 1 and 2). reference). Compared to the general spraying method, in which water, cement, and aggregate are kneaded and then the highly viscous kneaded material is pumped, the pipe resistance is suppressed to a low level, enabling long-distance, high-lift pumping. Has the advantage of

Japanese Patent No. 4229260 Japanese Unexamined Patent Publication No. 2005-1505069

By the way, if some trouble occurs during the implementation of the spraying method and the pumping of cement milk is stopped, there is a problem that the pipe through which the cement milk flows is blocked due to the thixotropy phenomenon.

Therefore, in order to avoid the blockage, it is conceivable to prevent the cement milk from staying in the pipe when the pumping of the cement milk is stopped. As a method, for example, a delivery hose is separately connected to the pipe through which the cement milk flows, and when the pumping is stopped, the cement milk is returned to the supply source through this delivery hose, taken out to the outside, or until the pumping is restarted. It can be circulated. However, these methods may lead to a significant cost increase, and neither of them is realistic.

It is considered that the above-mentioned blockage occurs not only when the pressure feeding of the cement milk is stopped but also when the pressure feeding of the cement fluid is stopped.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a cement-based mixture spraying method capable of effectively preventing the occurrence of blockage when the pumping of cement milk is stopped. ..

In order to achieve the above object, in the cement-based mixture spraying method according to the present invention, cement-free aggregate and cement milk are separately pumped from their respective sources and mixed by a mixing device. the resulting cementitious mixture, a spraying method cementitious mixture producing spray of the cementitious mixture, the cement milk connecting the cement flow animals pumping device is the source of the cement milk and the mixing device When pumping through a pipe, the cement milk at the supply source contains 40-60% non-volatile content containing an acrylic copolymer, pH 6.0-10.0, and viscosity 80-150 mPa · s. by adding an acrylic latex can be suppressed thixotropic behavior of the cement milk to be added to the cement milk I polymer latex der, to suppress the thixotropic behavior of the cement milk, the piping of the cement milk pumping Prevents blockage when stopped (claim 1).
The acrylic latex may be added in an amount of 1 to 10% of the amount of cement to the cement milk when the water-cement ratio (W / C) is 50% (claim 2).

According to the present invention, a cement-based mixture spraying method capable of effectively preventing the occurrence of blockage when the pumping of cement milk is stopped can be obtained.

That is, in the cement-based mixture spraying method of the invention according to each claim of the present application, by adding acrylic latex to cement milk, the thixotropy phenomenon can be suppressed and stable pumping without clogging of the piping becomes possible. It is also possible to improve workability and achieve a longer pumping distance by reducing the cleaning time and number of pipes.

In addition, the bearing effect of acrylic latex can improve the fluidity of cement milk.

Further, the polymer particles of the acrylic latex are filled in the voids between the cement particles and become dense (fine), so that the durability of the mortar or concrete after formation is also improved.

Cracks in mortar and concrete occur due to factors such as drying shrinkage, but with the addition of acrylic latex, the hydration reaction of the cement fluid becomes slower and heat shrinkage is less likely to occur, so drying shrinkage occurs. The occurrence of cracks due to the above is suppressed. When short fibers are added, which is effective as a means for preventing cracks due to drying shrinkage, there is a concern that the workability during kneading and pumping may be reduced due to a decrease in fluidity. However, the addition of acrylic latex improves the fluidity. Such a concept does not occur.

It is an overall composition explanatory drawing which shows roughly the structure of the cement-based mixture spraying method which concerns on one Embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the cement-based mixture spraying method (hereinafter abbreviated as the spraying method) according to the present embodiment includes the aggregate (sand in this example) 2 supplied from the aggregate pumping machine 1. This is for forming a legal frame 6 by spraying a cement-based mixture 5 obtained by mixing water 3 and cement milk pumped by a cement fluid pumping device 4 onto a slope N.

Specifically, a net 7 such as a wire mesh is stretched on the slope N, and reinforcing bars 8 are arranged in a grid pattern on the net 7 to form a legal frame spraying portion, and a space portion of the legal frame spraying portion is formed. While arranging the curing sheet 9 on the surface, the cement-based mixture 5 is sprayed so as to cover the lattice-shaped reinforcing bars 8 to form a lattice-shaped legal frame 6, and then the curing sheet 9 is peeled off and plant seeds and fertilizer are applied. The vegetation base material 10 containing the vegetation base material 10 is sprayed onto the slope 6 to protect the slope N from greening.

In this embodiment, the cement-based mixture 5 is a mortar material in which cement, sand as a fine aggregate, and water are mixed (usually, the weight mixing ratio is cement: sand: water = 1: 4: 0). In the present invention, for example, cement, sand as a fine aggregate, gravel, gravel, crushed stone, etc. as a coarse aggregate, and concrete mixed with water will be described. It is also applicable when the material is used as the cement-based mixture 5.

By the way, the spraying method of the present embodiment can be carried out by using a cement-based mixture spraying device (hereinafter, abbreviated as a spraying device) shown in FIG.

In this spraying device, an air compressor 11 that supplies compressed air is connected, and an aggregate pumping machine (supply of aggregate 2 and water 3) for pumping aggregate 2 and water 3 that do not contain cement (cement milk) is connected. Source) 1 and a cement fluid pumping device 4 for pumping cement milk separately from the aggregate 2 and water 3 are provided. Then, the aggregate 2 and the water 3 are supplied from the aggregate pumping machine 1 to the portable mixing device 13 as the mixing means via the pipe (hose) 12, and the pipe (hose) is supplied from the cement fluid pumping device 4. Cement milk is supplied to the mixing device 13 via 14. The aggregate 2, water 3, and cement milk supplied to the mixing device 13 are mixed, and then sprayed from the spray nozzle 16 through the pipe (hose) 15 so as to cover the reinforcing bar 8 as the cement-based mixture 5.

Then, in the present embodiment, the thixotropy effect is obtained by adding (mixing and stirring) acrylic latex to cement milk (at least an example of cement fluid containing cement and water) in the cement fluid pumping device (supply source) 4. By pumping cement milk in a state where the pressure is suppressed, it is possible to effectively prevent blockage of the piping when the pumping of cement milk is stopped.

That is, when the pumping of general cement milk to which acrylic latex is not added is stopped, the piping through which the cement milk flows is blocked due to the thixotropic phenomenon, but when acrylic latex is added to cement milk, the cement milk is cured. No clogging of the piping due to the above.

The reason for this is considered as follows. First, the occurrence of the thixotropy phenomenon is caused by the difference in specific gravity of each component of cement milk causing separation, sedimentation, precipitation, consolidation, and hardening of cement milk. Then, when an acrylic latex is added to the cement milk, the high molecular polymer having a high viscosity reducing effect (bearing effect) contained in the acrylic latex adheres uniformly around the cement particles in the cement milk component. (The particle size of the high molecular polymer is equivalent to 0.2 μm, which is 1/100 of the cement particles), and phenomena such as separation due to the difference in specific gravity of each component of cement milk are suppressed, and when the pumping of cement milk is stopped. Piping blockage will be avoided.

Hereinafter, the viscosity reducing power of acrylic latex (high molecular polymer) will be considered in more detail.

First, when the specific gravity of cement used is 3.15 (kg / L), the specific gravity of water is 1.0, and the specific gravity of water cement (W / C) in the design formulation is 50%, per batch of cement milk. Calculate the specific gravity.
(1) The amount of cement W1 used per batch of cement milk is 100 kg.
(2) Similarly, the amount of water W2 used per batch of cement milk has a water-cement ratio of 50%.
W2 = cement 100kg x 0.5 = 50kg
Will be.
(3) The volume V1 of cement used per batch of cement milk is
V1 = 100kg ÷ 3.15 (kg / L) = 31.75L
(4) The volume V2 of water used per batch of cement milk is
V2 = 100kg x 50% = 50kg = 50L
(5) The specific gravity S per batch of cement milk is
S = (W1 + W2) / (V1 + V2)
= (100 kg + 50 kg) / (31.75 L + 50 L)
= 1.83 (kg / L) ≒ 1.8 (kg / L)
Will be.

That is, cement milk, which is a uniform sol state suspension (suspension) having a specific gravity of 1.8 during pumping (during stirring flow), also has a uniform sol state with a specific gravity of 1.8 due to the thixotropy phenomenon when pumping is stopped. It becomes difficult to hold it, and it starts to separate into water having a specific gravity of 1.0 and cement having a specific gravity of 3.15, and gels (solidifies).

In order to suppress this thixotropy phenomenon, a protective stabilizer having a viscosity reducing force sufficient to avoid the gravitational action which is the main cause of gelation may be added, and the acrylic latex is used as the protective stabilizer. It can be positioned as one that exerts its function.

By pumping cement milk with the thixotropy effect suppressed by adding acrylic latex, stable pumping without blockage of the piping becomes possible, reducing the cleaning time of the piping and lengthening the pumping. It is also possible to achieve distance.

In addition, the bearing effect of acrylic latex can improve the fluidity of cement milk.

Further, the polymer particles of the acrylic latex are filled in the voids between the cement particles and become dense (fine), so that the durability of the mortar or concrete after formation is also improved.

In addition, with the addition of the acrylic latex, the hydration reaction of the cement fluid becomes slower and heat shrinkage is less likely to occur, so that cracks are suppressed and the fluidity is improved in this respect as well. ..

As the acrylic latex, for example, an acrylic polymer latex having a non-volatile content of 40-60%, a pH of 6.0-10.0, and a viscosity of 80-150 mPa · s containing an acrylic copolymer can be used.

The amount of acrylic latex added may be about 1 to 10%, preferably 2 to 5% of the amount of cement with respect to cement milk having a W / C of 50%. If the amount of acrylic latex added is less than 1%, a sufficient effect of improving fluidity may not be obtained. On the other hand, if it exceeds 10%, the strength of the mortar or concrete after hardening may decrease and the required strength may not be obtained. The amount of addition can be appropriately adjusted in consideration of the hardening prevention performance of cement milk when the cement milk pumping is stopped.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can be variously modified and implemented without departing from the gist of the present invention.

1 Aggregate pumping machine 2 Aggregate 3 Water 4 Cement fluid pumping device 5 Cement-based mixture 6 Legal frame 7 Net 8 Reinforcing bar 9 Curing sheet 10 Vegetation base material 11 Air compressor 12 Piping 13 Mixing device 14 Piping 15 Piping 16 Spray nozzle N Slope

Claims (2)

Cement-free aggregate and cement milk are separately pumped from their respective sources and mixed in a mixer to obtain a cement-based mixture, which is then sprayed. upon a method, it pumped through a pipe which connects the cement flow animals pumping device is the cement milk a source of the cement milk and the mixing device,
The cement milk in the source, a nonvolatile content of 40-60% containing an acrylic copolymer, PH6.0-10.0, the cement viscosity What acrylic polymer latex der of 80-150mPa · s By adding an acrylic latex that can suppress the thixotropy phenomenon of the cement milk when added to milk and suppressing the thixotropy phenomenon of the cement milk, it is possible to prevent the pipe from being blocked when the pumping of the cement milk is stopped. Spraying method of cement-based mixture. The method for spraying a cement-based mixture according to claim 1, wherein 1 to 10% of the amount of cement is added to cement milk when the acrylic latex has a water-cement ratio (W / C) of 50%.

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