JP4477657B2 - Method for determining the proportion of finely divided powder in shotcrete, method for dividing and mixing the shotcrete obtained by this decision method and method for determining the proportion of thickener added to shotcrete - Google Patents

Description

The present invention relates to a method for determining a fine powder blending ratio of a sprayed concrete and a thickening agent so as to determine an optimum blending ratio capable of reducing concrete rebound (hereinafter referred to as rebound) when spraying concrete in a tunnel or the like. The present invention relates to a method for dividing and mixing sprayed concrete obtained by a method for determining an addition ratio and a method for determining a blending ratio of fine powder of shotcrete.

Conventionally, as a tunnel construction method, a shield method, a bench cut method, a NATM method, and the like are known. In these methods, lining work is performed to cover the ground of the inner wall of the tunnel with concrete. As the lining work, a concrete spraying method is used in which concrete is sprayed directly onto the ground in the tunnel and temporary support work is constructed as the primary lining.
By the way, in the conventional concrete spraying method, about 30% of rebound occurs when concrete is sprayed on natural ground, which is a big loss. As a concrete spraying method for improving this, a technique for increasing the viscosity of concrete for spraying by combining silica fume and fine limestone powder in a concrete material has been proposed.
In this case, silica fume and limestone fine powder are set in advance to a specific blending amount, which is replaced with a part of fine aggregate and mixed. By this construction method, the loss of concrete due to rebound during spraying can be reduced to about 20%. In addition, the amount of dust scattering is specified to reduce the amount of dust in the air at a position 50 m behind the face from 7 to 8 mm / m ³ in the conventional method to about ³ mm / m ^3. Yes.

  In the method described in Patent Document 1, 5 wt% silica fume is replaced and mixed in cement, and fine aggregate is mixed with fine limestone powder so that 15% of the size is 0.15 mm or less for the fine aggregate. It is adjusting. However, this method has the disadvantage that silica fume is relatively expensive and costly, and the substitution addition amount of 15% by weight of limestone fine powder is an empirically set value. Depending on the type, the rebound reduction effect may vary.

By the way, when constructing temporary support works by spraying concrete onto natural ground at each construction site such as a tunnel, it is necessary to use cement, fine aggregate, coarse aggregate, etc. collected in the surrounding area of the construction site. It is common. For this reason, since the type of material changes at each site, a spray test was performed to determine the optimum blend ratio of each material with little rebound (see Patent Document 2).
In the method for determining the mixing ratio of concrete materials described in Patent Document 2, etc., about 10 types of cement, fine aggregate, coarse aggregate, and fine powder, etc., with different mixing ratios are selected on site during the spray test. And knead to produce a test sample. In this case, the blending amount of silica fume and fine limestone powder was selected from a plurality of blending ratios by appropriately changing the replacement ratio of fine aggregate. Then, about 3 types of concrete were narrowed down from the obtained concretes with about 10 types of mixing ratio and actually sprayed on the ground, and the craftsmen selected concrete with an optimal mixing ratio with little rebound.
Japanese Patent No. 3448634 JP 2002-337132 A

  However, since the types of materials such as cement and aggregate change when the area of the construction site changes, it is necessary to repeat the spray test at the construction site each time, which is extremely complicated and expensive. In particular, the spray test conducted at the construction site has the disadvantage of high costs due to the large amount of equipment and labor costs. Moreover, the spray test at the construction site is very time-consuming and the work must be interrupted during the test period.

In view of such circumstances, the present invention does not perform a spray test at each construction site or minimizes it, and determines the blending / addition ratio of the fine powder or thickener in the concrete that affects rebound and the like. A method for determining the proportion of finely divided powder in sprayed concrete that can be determined and reducing costs, a method of dividing and mixing the sprayed concrete obtained by this determination method , and a method of determining the proportion of thickener added to sprayed concrete. The purpose is to provide.

The method for determining the mixing ratio of fine powder of sprayed concrete according to the present invention includes cement, water, fine aggregate and coarse aggregate, and mixes and kneads fine powder such as limestone fine powder, blast furnace slag fine powder or fly ash. In the method for determining the blending ratio of mixed shotcrete, regarding the blending of mortar from which coarse aggregate is removed from shotcrete, a part of fine aggregate is replaced with fine powder and the content of the fine powder is sequentially changed. obtaining a plurality of types of mortar by kneading and mixing, the fluidity and viscosity changes in fluidity and viscosity of the plurality kinds of mortar for substitution rate of the fine powder as measured by the flow test and viscosity test linear due to the inclination change changing point of change is detected, respectively, the proportion of fine powder in the vicinity of any of the change point of fluidity and viscosity or range of change points Characterized by being adapted to determine the proportion of the mortar I.
According to the present invention, a fluidity test and a viscosity test are performed on mortar with different blending ratios of fine powder, and the change point where the slope of the change in flowability and viscosity with respect to the substitution rate of the fine powder changes from the test result is changed. and found, it was to determine any or proportion of fine powder in the range of the change point in the vicinity of the change point of fluidity and viscosity as a blending ratio of the mortar. Therefore, it is possible to determine the blending ratio of fine powder to reduce rebound of shotcrete at a place other than the construction site, and manufacture multiple concrete samples with different blending ratios of fine powder at the construction site as before. In addition, it is not necessary to determine the optimal blending ratio of fine powder by performing the spray test, and it is possible to reduce the cost of the spray test and the time required for the spray test and to eliminate the need to stop the construction during the spray test. Can be reduced.

In addition, it is preferable to select the one with the lower content of the fine powder out of the blending ratio of the fine powder in the vicinity of the change point of fluidity and viscosity.
In the case of selecting a lower content of fine powder, the amount of fine powder mixed is small, and the material cost can be reduced. Alternatively, if the mixing ratio of the fine powder in the vicinity of the changing point with a low cost in total is selected, the one with the larger amount of fine powder may be adopted. The rebound of shotcrete can be further reduced by selecting the blending ratio of fine powder near the changing point of the higher viscosity.

The method for determining the mixing ratio of fine powder of sprayed concrete according to the present invention includes cement, water, fine aggregate and coarse aggregate, and mixes and kneads fine powder such as limestone fine powder, blast furnace slag fine powder or fly ash. In the method of determining the blending ratio of mixed shotcrete, regarding the blending of mortar from which coarse aggregate is removed from shotcrete, a part of fine aggregate is replaced with fine powder and the content of this fine powder is changed sequentially. obtaining a plurality of types of mortar by fluid mortar while mixing is kneaded by blending a water reducing agent to be constant, for substitution ratio of the fine powder by performing the viscosity test of the plurality kinds of mortar the slope of the viscosity change detects a change point that changes the curve of a gentle slope from the straight line, the mortar by mixing ratio of fine powder definitive near the change point Characterized by being adapted to determine the mixing ratio.
According to the present invention, while maintaining the fluidity constant, fine powder by performing the viscosity test for mortar having different mixing ratio detecting a change point of the change in viscosity, fine powder definitive near these change points The blending ratio in the mortar was determined by the blending ratio. Therefore, it is possible to determine the blending ratio of fine powder to reduce the rebound of shotcrete at places other than the construction site, and to maintain the fluidity constant regardless of changes in the viscosity of the mortar. This makes it easier to determine the blending ratio.

In addition, the optimum blending ratio of fine powder should be determined by setting a plurality of blending ratios of fine powder in the vicinity of the change point and conducting a spray test on concrete containing mortar mixed with fine powders of each blending ratio. It may be.
In the present invention, a spray test is performed at a construction site or the like, and a plurality of fine powder blending amounts near the changing point at which the slope of the change in viscosity with respect to the substitution rate of the fine powder changes from a straight line to a gentle slope curve is set. When the spray test is performed, the rebound of all the concrete is reduced. Therefore, the mixing ratio of fine powder for obtaining high-precision concrete with lower rebound can be determined with a small number of concrete samples.

The method of dividing and mixing sprayed concrete according to the present invention is obtained by mixing the powdered concrete obtained by mixing the fine powder whose mixing ratio is determined by the method for determining the mixing ratio of the fine powder of concrete according to any one of claims 1 to 4 . Concerning the split kneading method , as shown in the following equation (1), the amount of restraint water of cement (α × C), the amount of restraint water of fine powder (γ × Ls), and the amount of restraint water of fine aggregate (βOH × S) are accumulated. It is characterized by dividing and kneading as a temporary amount of water.
W1 = α × C + γ × Ls + βOH × S (1)
However, W1: Optimal primary water volume
α: Restraint water ratio of cement
γ: Restrained water rate of limestone fine powder βOH: Restrained water rate of fine aggregate C: Unit cement amount Ls: Unit limestone fine powder amount S: Unit fine aggregate amount

The method for determining the amount of thickening agent added to sprayed concrete according to the present invention includes cement, water, fine aggregate, and coarse aggregate. In the determination method, regarding the blending of mortar from which coarse aggregate has been removed from sprayed concrete, a plurality of types of mortars are obtained by adding and kneading with the addition amount of the thickener being sequentially changed. The change in fluidity and viscosity of the fluid is measured by the fluidity test and the viscosity test, and the change point where the slope of the change in fluidity and viscosity changes with the addition rate of the thickener is detected. characterized by being adapted to determine the addition ratio of the thickener in the mortar by adding the percentage of thickener definitive near Kano change point.
According to the present invention, a fluidity test and a viscosity test are performed on mortar with different addition ratios of the thickener, and the slope of the change in flowability and viscosity with respect to the addition ratio of the thickener changes from the test results. by detecting a change point, the addition ratio of the thickener definitive near these changing point was determined as the proportion of the added to the mortar. Therefore, it is possible to determine the proportion of thickener added to reduce the rebound of shotcrete at locations other than the construction site, and produce a large number of concrete with different proportions of thickener added at the construction site as before. Therefore, it is not necessary to determine the optimum addition ratio of the thickener by performing the spray test, and it is possible to reduce the cost of the spray test and the labor of the spray test, and to perform the spray test without having to stop the construction during the spray test. Cost can be reduced.

Moreover, you may make it select the one where the addition amount of a thickener is low among the addition ratios of the several thickener in the vicinity of the change point of fluidity | liquidity and a viscosity.
When the addition amount of the thickener is low, the material cost can be reduced. Alternatively, the thickener addition amount may be adopted as long as the addition ratio of the thickener in the vicinity of the change point with a low cost can be selected. If the addition ratio of the thickener with higher viscosity is determined, the rebound of sprayed concrete can be further reduced.
Further, by using a mortar made to determine the addition ratio of the thickener by the addition proportion of the thickener in the vicinity of the change point, sets a plurality of addition rate of the thickener in the vicinity of the change point, each addition ratio You may make it determine the addition ratio of an optimal thickener by performing a spray test with the concrete containing a thickener.
In the present invention, a final spray test will be performed at a construction site, etc., but if a spray test is performed with a plurality of thickener addition amounts near the change point of fluidity or viscosity, any mortar will be rebound. Therefore, it is possible to determine the amount of thickener added to obtain high-precision concrete with lower rebound with a small number of concrete samples.

When mixing the mortar, add primary water (W1) to the fine aggregate and knead the mixture, then add the mixed powder containing limestone fine powder and admixture to the cement and cement, and mix them further. You may make it manufacture mortar by adding the secondary water amount (W2) which removed the primary water amount (W1) from the water amount (W), and kneading.
Or you may make it manufacture mortar by supplying the total amount of water and dividing it into lump without dividing into primary water and secondary water.

As described above, according to the method for determining the proportion of fine powder blended in the shotcrete and the method for determining the proportion of thickener addition according to the present invention, the blending and blending of the fine powder or the thickener by the fluidity test and the viscosity test, or the viscosity test. Since the change point of the slope of the characteristic of the mortar with respect to the addition ratio is found and the mixing ratio and the addition ratio are determined, the optimum mixing ratio of the concrete with little rebound and dust can be determined. In addition, there is no need to perform a spray test with multiple types of concrete samples with different blending / addition ratios of fine powder or thickener, even if the cement or fine aggregate used at each construction site is different. The cost of spray test can be greatly reduced, and the composition and addition ratio of sprayed concrete can be completed in a short period of time at a location other than the construction site. .
In addition, even when a final spray test is performed at the construction site, only changes in slope of viscosity characteristics, etc. depending on the blending / addition ratio of fine powder or thickener, and sprayed concrete with several blending / addition ratios before and after that Therefore, the spray test can be performed in a short period of time and at a relatively low cost.
According to the method of dividing and mixing sprayed concrete according to the present invention, concrete having an optimal composition with little rebound and dust can be obtained, which is optimal for spraying.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a graph showing the results of testing the flowability and viscosity of shotcrete when changing the substitution rate of fine limestone powder according to the first embodiment of the present invention.
As a base material for high-strength shotcrete used in the first embodiment of the present invention, cement, water, fine aggregate, coarse aggregate and admixture collected in the surrounding area of the construction site are blended in the proportions shown in Table 1 below. Use what you did. In addition, this concrete does not need to contain the admixture (water reducing agent).

In the shotcrete with the composition shown in Table 1, the portion excluding the coarse aggregate has a mortar composition ratio of the same composition conditions. In this mortar, in order to reduce rebound (bounce rate) at the time of spraying, limestone fine powder is mixed by substituting a part of the fine aggregate with respect to the volume of the fine aggregate. As shown in Table 2, the ratio of fine limestone powder to be replaced with fine aggregate is NO. The sample increased from 0 vol% to 25 vol% at 1 to 8 at a predetermined interval is selected as a test sample. The blending conditions of this mortar are approximately 200% sand cement ratio and 47.5% water cement ratio.
In Table 2, NO. 1, the total weight of fine aggregate is 2kg, the amount of fine limestone powder is 0, the amount of fine limestone powder is 3vol%, 5vol%, 7vol%, 10vol%, 15vol%, 20vol without changing the total weight. %, 25 vol%, and the content of fine aggregate is decreased as it is sequentially increased. In Table 2, for reference, the blending ratio (substitution rate) of limestone fine powder is shown in weight (wt)% in addition to volume (vol)%.

Table 2 shows the blending ratio of limestone fine powder. In order to produce each sprayed concrete by adding a predetermined proportion of coarse aggregate to the mortar composition set to 1-8, the sprayed concrete may be kneaded together, but in this embodiment, for example, Japanese Patent No. 2597835, Japanese Patent No. 3318580 No. 3, Patent No. 3448634, etc., and using the divided kneading method (SEC (registered trademark) method), it is manufactured by mixing in two stages.
The split kneading method is described in detail in the above-mentioned patent publications and will be briefly described. In the split kneading method, the primary water amount W1 is added to the aggregate made of fine aggregate (which may contain coarse aggregate) and adjusted and kneaded, so that moisture is evenly attached to the entire circumference of each fine aggregate. Let After that, a limestone fine powder or mixed powder containing admixture is added to the required amount of cement or cement, followed by primary kneading, and the cemented cement or mixed powder in the capillary state adheres around each fine aggregate. Shelled.
Then, by adding the secondary water amount W2 (and admixture if necessary) from which the primary water amount W1 has been removed from the total water amount W, and performing the secondary mixing, the cement and the mixed powder are well dispersed and a homogeneous concrete is obtained. Will be.
The obtained sprayed concrete contains coarse aggregate, but the mortar component excluding coarse aggregate has the same component ratio as mortar not containing coarse aggregate.

Here, the fluidity and viscosity of the mortar are important for spraying with reduced rebound of sprayed concrete. Since sprayed concrete is pumped by a pump, if the fluidity is low, there is a problem that the pumping is not performed smoothly, and if the fluidity is too high, the strength of the concrete decreases and the adhesion ability by spraying decreases, so the rebound increases. To do. In addition, viscosity is required to reduce rebound of shotcrete. On the other hand, if the viscosity is too high, the fluidity is lowered and pumping by the pump is not smooth.
Therefore, the NO. About each mortar of 1-8, the fluidity | liquidity of a mortar is measured as a "F15 flow value (mm)" by a mortar flow test. Further, the viscosity of the mortar is measured as “plastic viscosity (Pa-s)” (viscosity) by a viscosity measurement test such as a rotational viscometer or a flow time measurement test of the mortar.

In the sprayed concrete shown in Table 1 and Table 2, when the fluidity and viscosity obtained as the substitution rate (mixing ratio) of the limestone fine powder is increased, the graph shown in FIG. 1 is obtained.
Here, in FIG. 1, when the mixing rate of the limestone fine powder is increased from 0 with respect to the fluidity, almost the same flow value is exhibited up to 10 vol% with a very gentle slope, and the mixing rate of 10 vol% of the limestone fine powder is slightly reduced. When the mixing rate was further increased as the change point P1 at which the slope of the change in flowability with respect to the powder replacement rate changed by a straight line , the flowability gradually decreased.
Also, regarding the viscosity, when the mixing rate of limestone fine powder is increased from 0, it increases almost linearly with a gentle slope up to 15 vol%, and the change in viscosity with respect to the substitution rate of the fine powder is increased by 15 vol% of the limestone fine powder. When the mixing rate was further increased as the changing point P2 at which the slope of the straight line changes, the result was that the viscosity rapidly increased. In a region where the viscosity has rapidly increased, it is necessary to take measures such as adding a chemical such as a water reducing agent or increasing the amount of water distribution in order to ensure a predetermined fluidity. However, the addition of chemicals increases the material cost, and increasing the amount of water may decrease the concrete strength.

For this reason, when considering the necessity to balance each characteristic of fluidity and viscosity as preferred properties of sprayed concrete, the mixing rate of limestone fine powder as each change point is around 10 vol% and 15 vol%, or 10 vol% to 15 vol%. It can be said that the range is a preferable blending ratio. In this way, when the substitution rate of limestone fine powder is changed sequentially, it is possible to detect a favorable region of mortar spraying characteristics from the change point of fluidity and viscosity, so many samples are set and sprayed at construction sites such as tunnels. It is not necessary to perform a test, and the optimal blending ratio can be determined by performing a fluidity and viscosity test in a room or the like.
In this embodiment, it can be said that it is preferable to employ 10 vol% having the smallest blending ratio of the limestone fine powder for cost reduction. Alternatively, even when a mixing ratio of 15 vol% of limestone fine powder is selected, it is sufficient if the total cost can be reduced as compared with a case of adding a drug for ensuring viscosity in the case of 10 vol%.

When a mixing ratio of 10% by volume of limestone fine powder is selected, the mixing ratio of high-strength sprayed concrete is as shown in Table 3. And it knead | mixed about the concrete compounding ratio shown in Table 3, and when the property and intensity | strength were measured about the obtained fresh concrete for spraying, the result shown in Table 4 was obtained. From the results shown in Table 4, the target slump and strength of the sample for spraying concrete (standard specimen) were sufficiently satisfactory.
In addition, the sprayed concrete with this blending ratio was kneaded with a real machine batcher at the construction site and subjected to the spraying test. As a result, the results shown in Table 5 were obtained and the properties of the sprayed concrete were good and the rebound was 20%. It was confirmed that the following can be reduced.

As described above, according to the method for determining the proportion of sprayed concrete according to the present embodiment, a plurality of types containing fine limestone powder in which a part of fine aggregate is replaced in a place such as a room different from the construction site. By using the flow rate test and the viscosity test, it is possible to determine the change points P1 and P2, which are the optimal mix rate of the fine limestone powder, and the vicinity thereof by performing the fluidity test and the viscosity test. A sprayed concrete that can secure sufficient strength and reduce rebound is obtained. Moreover, when determining the blending ratio of limestone fine powder, it is not necessary to set a large number of samples and perform a spray test at each construction site even if the materials such as cement and aggregate change at each construction site. This eliminates the time and effort required to perform a spray test at the site, and there is no need to interrupt the construction, so the cost for performing the spray test at the construction site can be greatly reduced.
Moreover, generation | occurrence | production of the dust at the time of spraying can be suppressed by making spray concrete low rebound.

In the first embodiment described above, a mortar is manufactured by setting a plurality of blending ratios of limestone fine powder in a room different from the construction site, and an appropriate blending of limestone fine powder by a fluidity test and a viscosity test. Although the ratio is determined, the blending ratio of the limestone fine powder may be determined more precisely. For that purpose, in addition to the blending ratio of limestone fine powder determined in the vicinity of fluidity or viscosity change points P1 and P2, a plurality of blending ratios in the vicinity of the change points P1 and P2 are set to manufacture each mortar for spraying. Then, a mortar containing a limestone fine powder having a suitable blending ratio with the least rebound may be determined by performing a spray test at a construction site.
Even in this case, the number of samples can be reduced as compared with a determination method based on a spray test performed at a conventional construction site, and spray concrete with a high-accuracy blending ratio with less rebound can be manufactured.

Next, a method for determining the blending ratio of shotcrete according to the second embodiment of the present invention will be described.
In the first embodiment described above, by changing the blending amount of the limestone fine powder, the flowability and viscosity of the mortar are made variable, and the optimum blending ratio of the limestone fine powder is determined from the respective change points of both. In this embodiment, the blending ratio is determined from the relationship between the blending amount of limestone fine powder and the viscosity (plastic viscosity) with the mortar fluidity being constant.
In this embodiment, the fluidity tends to gradually decrease by sequentially increasing the blending amount of the limestone fine powder in the mortar, but the fluidity can be maintained constant even if the blending amount of the limestone fine powder is changed. Adjust the amount of water reducing agent used and knead.
Thus, when the viscosity measurement test of mortar is implemented and the relationship between the compounding quantity of limestone fine powder and viscosity (plastic viscosity) is calculated | required, it will come to show in FIG. In FIG. 2, when the blending amount of fine limestone powder is replaced with fine aggregate and gradually increased, the plastic viscosity initially increases with a steep slope, and a curve is drawn that transitions to a gentle slope at the change point P3. It can be said that the blending amount of the limestone fine powder in the vicinity of the change point P3 is a low-cost value that reduces the amount of rebound and dust generation in the sprayed concrete and minimizes the blending amount of the limestone fine powder.

Therefore, also in this embodiment, while maintaining the fluidity constant, the pump pressure when pumping the sprayed concrete is kept constant, and the limestone at the viscosity change point P3 of the sprayed concrete obtained by the viscosity test By determining the blending amount of the fine powder, similarly to the first embodiment, rebound of sprayed concrete can be reduced, and the blending cost of the limestone fine powder can be reduced while reducing the blending cost. Moreover, since it does not require a spray test at the construction site, the cost for determining spray concrete can be reduced.

As a modification of the second embodiment, as in the determination method according to the first embodiment, a plurality of blending ratios in the vicinity of the change point P3 are mixed with respect to the blending ratio of the fine limestone powder determined in the vicinity of the viscosity change point. It is possible to determine the blending ratio of the fine limestone powder to obtain a suitable mortar with few rebounds by producing a mortar for spraying by setting the type and conducting a spray test at a construction site.
Even in this case, the number of samples can be reduced as compared with a determination method by a spray test performed at a conventional construction site, and spray concrete with a high-accuracy blending ratio can be manufactured with less rebound and low cost.

Next, a method for determining the proportion of sprayed concrete according to the third embodiment of the present invention will be described.
In the third embodiment, a thickener such as a dust reducing agent is used in place of the limestone fine powder as a material for reducing rebound. In this case, the thickener is not replaced with a part of the fine aggregate but is added to the sprayed concrete compounding material. The addition amount of the thickener is set in proportion to the weight of the cement. As shown in FIG. 3, the addition amount ranges from 0 wt% to 0.02 wt%, 0.05 wt%, 0.10 wt%, 0.15 wt%, 0 It shall increase in the order of 20 wt%. The blending ratio of sprayed concrete excluding the thickener is the same as that shown in Table 1.
Spray concrete is produced by kneading the spray concrete compounding material to which the thickener is added at each addition amount. FIG. 3 is a plot of the flowability value “F15 flow value” measured by mortar flow (F15) and the plastic viscosity (viscosity) measured by a B-type rotational viscometer for sprayed concrete obtained by adding each thickener. As shown.

In FIG. 3, the fluidity shows a tendency to gradually decrease as the amount of thickener added increases, and then increases slightly at 0.20 wt%. Also, the viscosity tends to increase gradually as the addition amount of the thickener increases, and tends to increase up to around 0.10 wt%, but the viscosity does not increase at 0.15 wt% or more. Here, when the addition ratio of the thickener exceeds a certain value exceeding 0.10 wt%, fine air bubbles are mixed inside the mortar due to the viscosity effect, so that the fluidity is slightly increased or the viscosity is increased. It shows a tendency to not.
As is apparent from FIG. 3, the curves indicating the fluidity and the viscosity are changed at the change point P4 where the slope of the change of the fluidity and the viscosity with respect to the addition rate of the thickener is changed similarly to the case where the fine powder of limestone is mixed. , P5 exist, respectively , and the fluidity and viscosity of the mortar are balanced by the addition amount of the thickener near these change points P4, P5. Moreover, it can be said that at these change points P4 and P5, the addition amount of the thickener for the mortar capable of exhibiting stable fluidity and viscosity is the smallest and the cost is low. In particular, it can be said that the amount of the thickener added near the change point P4 of the fluidity is less than that at the change point P5, and the cost is low.
The optimum thickener addition rate at the change point P4 shown in FIG. 3 is 0.12 wt%.

Also in the third embodiment, by adding a thickening agent with an addition amount in the vicinity of the change point P4, it is possible to create a large number of samples at the construction site and perform a spray test at a place different from the construction site. Rebound and dust can be reduced, and the amount of thickener added to shotcrete with sufficient strength can be determined. Therefore, it is possible to determine the optimum blending ratio of the shotcrete with low cost and little rebound.

As a modification of the third embodiment, as with the determination method according to the first and second embodiments, the addition amount of the thickener determined near the fluidity or viscosity change point P4 or P5 is A plurality of thickener addition amounts in the vicinity of the changing point are set and spray mortars are produced as samples. Based on the mortar of these samples, a spray test can be performed at a construction site to determine mortar or concrete containing a thickener with an optimum addition amount with sufficient strength and less rebound and dust.
Even in this case, it is possible to produce sprayed mortar or concrete with a low-cost, high-accuracy blending ratio with less rebound and dust compared to the conventional method of determination by spraying tests performed at construction sites. .

In each of the embodiments described above, limestone fine powder is employed as the fine powder, but various fine powders such as blast furnace slag fine powder and fly ash can be employed instead of or together with the limestone fine powder.
Needless to say, the blending ratio of the coarse aggregate such as cement and fine aggregate is not limited to that according to the embodiment of Table 1. Depending on the characteristics of concrete materials such as cement, fine aggregate, coarse aggregate, etc. employed at each construction site.

Next, as a fourth embodiment, a sprayed concrete obtained by mixing the limestone fine powder whose mixing ratio is determined by the above-described method for determining the mixing ratio of the fine powder of concrete and obtained by the division kneading method will be described. This divided kneading method is a SEC (registered trademark) method.
Regarding the method for determining sprayed concrete in which the mixing ratio of fine limestone powder is determined by the method according to the first and second embodiments described above, the amount of water restrained by cement (α × C), the amount of water restrained by fine powder (γ × Ls) The amount of primary water obtained by accumulating the amount of restricted water (βOH × S) of the fine aggregate is determined by the following equation (1).
W1 = α × C + γ × Ls + βOH × S (1)
However, W1: Optimal primary water volume
α: Restraint water ratio of cement
γ: Restrained water rate of limestone fine powder βOH: Restrained water rate of fine aggregate C: Unit cement amount Ls: Unit limestone fine powder amount S: Unit fine aggregate amount

Here, the restricted water ratio α of the cement is determined in advance by a test depending on the type of the cement. In this test, as shown in FIG. 4, the horizontal axis represents the primary water amount W per unit cement amount C, and the water amount W to be added to the unit cement amount C is gradually increased while performing a torque test at W / C. As a result, W / C is gradually increased. In the example shown in FIG. 4, the load current value (torque value) A of the screw is set by setting W / C in increments of 2% and rotating and adjusting the screw for the primary water amount W per unit cement. Ask for. When the torque value (A) with respect to W1 / C in increments of 2% is measured and plotted with W / C on the horizontal axis and the torque value (A) on the vertical axis, the graph shown in FIG. 4 is obtained.
In this case, the torque value is the highest and the optimum value at the position of W / C = 24%, which can be said to be in the capillary state. In this way, the restricted water ratio α of the unit cement is obtained.
Moreover, since the limestone fine powder is a powder, the restricted water rate γ of the limestone fine powder can be set by the same test as the above-described cemented water rate α of the cement. FIG. 5 shows the primary water amount W / Ls per unit limestone fine powder amount on the horizontal axis, and while performing a torque test at W / Ls, the water amount W introduced to the unit limestone fine powder amount Ls is gradually increased in increments of 5%. Increase the torque test sequentially.
And the value W / Ls = 21% with the highest torque value A (load current value) is the optimum restricted water ratio γ.

Further, the restricted water ratio βOH of the fine aggregate is also determined in advance by a test.
The unit fine aggregate amount S per unit cement C is represented by S / C, and the ratio of water remaining after centrifugal dehydration of the hydrated mortar is represented by a residual water powder ratio WZ / C. In FIG. 6, the absolute dry weight S / C (= 0, 1, 2) obtained by gradually adding the unit fine aggregate amount S to the unit cement C is taken on the horizontal axis, and the residual water powder ratio is taken on the vertical axis. Taking WZ / C, the ratio of WZ / C to S / C is represented by tan θ = βo (adsorption water ratio).
And since the restricted water content βOH of the fine aggregate is the water content in the surface dry state, it is expressed by the following equation.
βOH = (βo−Q) ÷ (1 + Q / 100) (2)
Here, Q: Water absorption rate of fine aggregate (physical property value measured by the method defined in JIS)

In this manner, the constrained water rate α of cement, the constrained water rate γ of fine limestone powder, and the constrained water rate βOH of fine aggregate are obtained, and the primary water rate W1 is obtained by the above equation (1).
In the divided kneading method, the primary water amount W1 is added to the aggregate made of fine aggregate (which may contain coarse aggregate), and the mixture is adjusted and kneaded so that moisture is evenly distributed around the entire circumference of each fine aggregate. Adhere to. After that, add the required amount of cement or mixed powder containing limestone powder or admixture to the required amount of cement as a dispersing agent and perform primary mixing, and the cemented cemented powder or mixed powder adheres around each fine aggregate And shelled.
Then, by adding the secondary water amount W2 (and admixture if necessary) from which the primary water amount W1 has been removed from the total water amount W, and performing the secondary mixing, the cement and the mixed powder are well dispersed and a homogeneous concrete is obtained. It is done.
In the third embodiment, the thickener is not replaced with a part of the fine aggregate, but is added to the sprayed concrete blending material. Therefore, according to the above-described divided kneading method (1) The method for determining the primary water amount is not adopted, and the thickener may be gradually added to the mortar in the capillary state to which the primary water amount has been added.

Next, examples of the present invention will be described.
Example 1
As Example 1, a specific example of the method for determining the mixing ratio of the fine powder of the shotcrete according to the first embodiment will be described.
First, sprayed concrete having a blending ratio shown in Table 1 was manufactured as a conventional example. The sprayed concrete was not mixed with fine limestone powder, and the fine aggregate alone was 948 kg / m 3.
On the other hand, in this example, No. 2 in Table 2 shown in the first embodiment. The change in fluidity and viscosity of each of mortars 1 to 8 was plotted with the graph shown in FIG. From FIG. 1, the change points P1 and P2 can be determined.
And in Example 1, No. of above-mentioned Table 2 is shown. As shown in FIG. 5, 10 vol% limestone fine powder, which is the changing point P1, was selected in consideration of the viscosity of the mortar and the cost of the limestone fine powder replacement amount. Example 1 A sprayed concrete having the composition shown in Table 3 (limestone fine powder = 98 kg / m3) in which coarse aggregate was added to mortar composition in which 10 vol% of limestone fine powder was substituted for fine aggregate was produced. It was.
And about the prior art example and Example 1, the test which sprays each sprayed concrete on the wall surface in a tunnel was done. The results are shown in Table 6. The measurement of the rebound rate was performed according to JSCE-F-563-2005 of the Japan Society of Civil Engineers. The bounce rate was measured three times each.
In addition, the measuring method of a rebound rate shall use the same thing also in the following Examples 2-4.

  In the test results, the rebound rate of the conventional example was 25.5 vol%, and the rebound rate of the example was 15.1 vol%. Therefore, according to the sprayed concrete according to the blending ratio of the present embodiment, the loss of concrete due to rebound during spraying from the sprayed concrete according to the conventional blending ratio by the substitution rate of 10 vol% of the limestone fine powder at the inflection point of the smaller numerical value. It has been confirmed that can be further reduced.

  In Examples 2 to 4 below, with regard to ordinary sprayed concrete that is often used for the general specifications of construction contractors at construction sites A, B, and C, the fineness of sprayed concrete according to the first to third embodiments is used. Specific examples in the case of applying the powder blending ratio determination method and the thickener addition ratio determination method will be described.

(Example 2)
For ordinary sprayed concrete at site A (unit cement amount C = 360 kg / m3), the mortar obtained by removing coarse aggregate from the conventional blending in Table 7 (using the above-mentioned SEC method (registered trademark) as a mixing method) With the blending ratio, the relationship between the substitution rate of the fine limestone powder according to the first embodiment, fluidity and viscosity was determined. As a result, the graph shown in FIG. 7 was obtained.
In addition, the viscosity at this time was defined as the flow-down time when a J14 funnel shown in the Japan Society of Civil Engineers standard JSCE-F-531-1999 was fixed to a shaking table and vibration of 30 Hz was applied.
From the result of the mortar test shown in FIG. 7, the limestone fine powder substitution rate at the viscosity (flowing time) change point P2 was 7.7 vol%. And with respect to the conventional mixing | blending shown in Table 7, the shotcrete mixing | blending in the case of mixing limestone fine powder with this substitution rate of 7.7 vol% is as showing in following Table 8. This is Example 2.

(Example 3)
In Example 3, fly ash was used in place of limestone as a fine powder partially replacing the fine aggregate blended in the shotcrete.
For normal shotcrete at site B (unit cement amount C = 360 kg / m3), the relationship between fly ash substitution rate, fluidity and viscosity at the blending ratio of mortar excluding coarse aggregate from the conventional blending in Table 9 Asked. As a result, the graph shown in FIG. 8 was obtained.
From the result of the mortar test shown in FIG. 8, the fly ash substitution rate at the change point P2 of viscosity (flowing time) was 10 vol%. Compared to the conventional blending shown in Table 9, the shotcrete blending when fly ash is mixed at this substitution rate of 10 vol% is as shown in Table 10 below.
This is Example 3.

Example 4
Example 4 demonstrates the specific example about the determination method of the thickener addition ratio of sprayed concrete by 3rd embodiment.
For normal shotcrete at site C (unit cement amount C = 360 kg / m3), the addition ratio and fluidity of thickener at the blending ratio of mortar excluding coarse aggregate from the conventional blending shown in Table 11 below. And the relationship of viscosity was obtained. As a result, the graph shown in FIG. 9 was obtained.
From the result of the mortar test shown in FIG. 9, the thickener addition rate at the change point P2 of viscosity (flowing time) was C × 0.05 wt%. Table 12 shows the composition of shotcrete in the case of mixing the thickener (C × 0.05 wt%) at this addition rate with respect to the conventional composition in Table 11.
This is Example 4.

And the example which substituted 7.7 vol% of limestone fine powder with respect to each conventional type with the conventional type (normal) shotcrete whose unit cement amount C in each site A, B, and C is 360 kg / m ³ 2. About Example 3 which substituted 10 vol% of fly ash, and Example 4 which mixed the thickener Cx0.05%, various tests including the spraying test of shotcrete were implemented, respectively. The results are shown in Table 13.

As described above in Examples 1 to 4, the substitution rate or addition rate, fluidity and viscosity of each fine powder and thickener were measured using a mortar formulation in which coarse aggregate was removed from the concrete formulation. From the relationship with the test results, the optimum substitution rate or addition rate of the fine powder and the thickener can be obtained.
Moreover, about each Example 2-4, each shotcrete was manufactured with each optimal substitution rate or addition rate, and it sprayed on the tunnel wall surface, and performed the spray test. Compared to conventional (ordinary) shotcrete at each site A, B, C where no fine powder or thickener is used, fine powder and increased by Examples 2-4 at each site A, B, C It was confirmed that the shotcrete for which the optimum replacement rate or addition rate of the adhesive was determined had a low rebound rate.

In addition, in Example 1 mentioned above, since the admixture was added and the spray concrete of the high fluid mixing | blending was employ | adopted, the limestone considered that the one where there was little addition amount of an admixture would reduce manufacturing cost. A change point P1 of fluidity with a relatively small addition ratio of fine powder was selected.
On the other hand, in Examples 2-4, since the admixture is not added to sprayed concrete, it is not necessary to consider the material cost by an admixture. Moreover, even if the amount of fine powder or thickener added is slightly increased, the increase in material cost is small. On the other hand, in order to reduce the rebound of the shotcrete, it is preferable that the viscosity is higher. Therefore, the change point P2 is selected so that the rebound has a smaller characteristic. In this way, which change points P1 and P2 are selected can be appropriately selected in consideration of the required characteristics and costs of the concrete at each construction site, such as cost and rebound.

Moreover, in this invention, in each embodiment mentioned above and its Examples 1-4 etc., when determining the substitution rate or addition rate of each fine powder or thickener, the graph which shows the relationship with fluidity | liquidity and viscosity. Although it is preferable to determine at or near any of the change points P1, P2, the values near the change points P1 and P2 may be used. Alternatively, the substitution rate or addition rate of each fine powder or thickener within the range of the change points P1 and P2 may be selected. If you decide within the change point P1 to P2, there is a possibility that a slight rebound, etc. is increased than when determined in the vicinity of the change point P1, P2 or, even then, the range of the change point P1 to P2 Preferred results are obtained when a deviating replacement rate or addition rate is selected or over conventional sprayed concrete.

It is related with the concrete for spraying by 1st embodiment of this invention, and is a graph which shows the change of the fluidity | liquidity and viscosity of a mortar at the time of changing the substitution rate (mixing ratio) of a limestone fine powder. It is related with the concrete for spraying by 2nd embodiment, and is a graph which shows the change of the viscosity of the mortar at the time of changing the substitution rate (mixing ratio) of the limestone fine powder in the state which controlled fluidity | liquidity uniformly. It is related with the concrete for spraying by 3rd embodiment, and is a graph which shows the fluidity | liquidity and viscosity change of a mortar at the time of changing the addition rate of a thickener. It is related with 4th embodiment, and is a figure which shows the torque test result for determining the constrained water rate of cement when manufacturing concrete using the limestone fine powder with which the mixture ratio was determined. It is a figure which shows the torque test result for determining the restraint water rate of a limestone fine powder similarly to FIG. It is a figure which shows the test result for determining the restraint water rate of a fine aggregate. It is related with the concrete for spraying by Example 2, and is a graph which shows the fluidity | liquidity and viscosity change of a mortar at the time of changing the substitution rate of a limestone fine powder. It is related with the concrete for spraying by Example 3, and is a graph which shows the fluidity | liquidity and viscosity change of a mortar at the time of changing the substitution rate of a fly ash. It is related with the concrete for spraying by Example 4, and is a graph which shows the fluidity | liquidity and viscosity change of a mortar at the time of changing the addition rate of a thickener.

Claims (8)

In the method for determining the fine powder blending ratio of sprayed concrete containing cement, water, fine aggregate and coarse aggregate, mixed with limestone fine powder, blast furnace slag fine powder or fly ash fine powder,
Regarding blending of mortar excluding coarse aggregate from the sprayed concrete,
Replacing a part of the fine aggregate with the fine powder and changing the content of the fine powder in order and mixing and kneading to obtain a plurality of types of mortar, the fluidity of these types of mortar and the change in the viscous flow test and measured by the viscosity test fine powder for replacement rate fluidity and viscosity changes in a straight line due to the change point at which the slope changes detected respectively, the change in any of the fluidity and viscosity A method for determining a blending ratio of fine powder in sprayed concrete, wherein the blending ratio in the mortar is determined by the blending ratio of the fine powder in the vicinity of the point or within the range of these change points. The method for determining the fine powder blending ratio of shotcrete according to claim 1, wherein the one with the lower content of the fine powder is selected from the blending ratio of the fine powder in the vicinity of the change point of the fluidity and viscosity. . In the method for determining the blending ratio of sprayed concrete containing cement, water, fine aggregate and coarse aggregate, mixed with limestone fine powder, blast furnace slag fine powder or fly ash fine powder,
Regarding blending of mortar excluding coarse aggregate from the sprayed concrete,
By substituting a part of the fine aggregate with the fine powder and mixing the fine powder content by sequentially changing and mixing with a water reducing agent so that the flowability of the mortar is constant. By obtaining a plurality of types of mortar and performing a viscosity test on the plurality of types of mortar, a change point where the slope of the change in viscosity with respect to the substitution rate of the fine powder changes from a straight line to a gentle slope is detected, and the change is detected . powder blending ratio determination method of the concrete spraying, characterized in that so as to determine the proportion of the mortar by the mixing ratio of the fine powder definitive in the vicinity of the point.   A plurality of blending ratios of fine powder in the vicinity of the change point are set, and an optimum blending ratio of the fine powder is determined by performing a spray test on the concrete containing the mortar mixed with the fine powder of each blending ratio. The method for determining the proportion of fine powder blended in sprayed concrete according to any one of claims 1 to 3. Regarding the method of dividing and kneading the sprayed concrete mixed with the fine powder, the mixing ratio of which is determined by the method for determining the mixing ratio of the fine powder of concrete according to any one of claims 1 to 4,
As shown in the following formula (1), the amount of primary water is obtained by accumulating the amount of restricted water (α × C) of the cement, the amount of restricted water (γ × Ls) of the fine powder, and the amount of restricted water (βOH × S) of the fine aggregate. A method of split kneading of sprayed concrete, characterized by splitting and kneading as
W1 = α × C + γ × Ls + βOH × S (1)
However, W1: Optimal primary water volume
α: Restraint water ratio of cement
γ: Restraint water ratio of fine limestone powder
βOH: Restraint water ratio of fine aggregate
C: Unit cement amount
Ls: Unit limestone fine powder amount
S: Unit fine aggregate amount In the method for determining the amount of thickener added to sprayed concrete containing cement, water, fine aggregate and coarse aggregate, and adding and kneading the thickener,
Regarding blending of mortar excluding coarse aggregate from the sprayed concrete,
Change the addition amount of the thickener sequentially and add and knead to obtain multiple types of mortar, and measure the change in fluidity and viscosity of these multiple types of mortar by fluidity test and viscosity test the addition ratio of the fluidity and viscosity of the change in the straight line by a change point at which the slope changes detected respectively, the thickener definitive near the change point of any fluidity and viscosity to the addition rate of the thickener and The method for determining the proportion of thickener added to sprayed concrete, wherein the proportion of thickener added in mortar is determined by Wherein among the addition ratio of the thickening agent in the vicinity of the change point of fluidity and viscosity, a thickener is added in sprayed concrete according to claim 6 which is adapted to select the lower of amount of the thickener How to determine the percentage.   Using a mortar that determines the addition ratio of the thickener according to the addition ratio of the thickener near the change point, set a plurality of addition ratios of the thickener near the change point, The method for determining the proportion of thickener added to sprayed concrete according to claim 6 or 7, wherein the optimum proportion of thickener added is determined by performing a spray test on concrete containing mortar mixed with the thickener. .

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