JP2021035900A - Csg and csg construction method - Google Patents

Abstract

To reduce deterioration of a compaction degree of CSG after compaction (rolling) and also reduce deterioration of structure strength if a long period of time is necessary until reaching compaction (rolling) after adding and mixing cement and water to a boring geologic material (site generation material).SOLUTION: A CSG contains an unwashed boring geologic material, cement, water and a setting retarder having an action that delays a condensation reaction of the cement. With a CSG construction method, CSG is laminated in a layer shape to construct a structure 101 by repeating the step of spreading and rolling the CSG.SELECTED DRAWING: Figure 1

Description

The present invention relates to a CSG and a CSG method.

Cement and water are added and mixed with the locally generated material (excavated soil material) obtained by excavating with a hydraulic excavator, transported to the construction site by a dump truck, leveled with a bulldozer, and compacted with a vibrating roller (rolling). A CSG method for constructing a structure by pressing) is known.

Japanese Unexamined Patent Publication No. 2011-168977

However, in the CSG method, it may take a long time from the addition and mixing of cement and water to the locally generated material to the compaction (compacting). In such a case, the inventors of the present application have performed after compaction (compacting) as compared with the case where the time from adding and mixing cement and water to the locally generated material to compaction (compacting) is short. We have found the problem that the degree of compaction of CSG becomes low and the strength of the constructed structure becomes low.

The present invention has been made in view of the above problems, and when it takes a long time from the addition and mixing of cement and water to the locally generated material to compaction (compacting), compaction (compacting) The purpose is to suppress a decrease in the degree of compaction of CSG after (rolling) and to suppress a decrease in the strength of the structure.

The present invention is a CSG containing an unwashed excavated soil material, cement, water, and a coagulation retarder having the effect of delaying the coagulation reaction of the cement.

Further, the present invention comprises excavated soil material, cement, water, and a coagulation retarder having an action of delaying the coagulation reaction of cement, and the excavated soil material is JIS A 1204 “Soil particle size test method”. According to the above, the mass fraction of the sieve passing through the nominal size of 0.15 mm exceeds 3%, which is CSG.

Further, the present invention is a CSG method for constructing a structure by stacking CSGs in layers by repeating the steps of leveling and compacting the CSGs.

According to the present invention, when it takes a long time from the addition and mixing of cement and water to the excavated soil material (locally generated material) to compaction (compacting), CSG after compaction (compacting) It is possible to suppress a decrease in the degree of compaction and suppress a decrease in the strength of the structure.

It is a vertical sectional view of a dam. It is a front view of the dam seen from the upstream side. The leaving time (horizontal axis) after adding and mixing cement and water to the excavated soil material, and the degree of compaction (vertical axis) when compaction (rolling) is performed after the lapse of the leaving time represented by the horizontal axis. It is a graph which shows the relationship of. It is a figure which shows the compaction curve of the excavated soil material. The standing time (horizontal axis) after adding and mixing cement and water to the excavated soil material, and the peak strength (vertical axis) when compaction (rolling) is performed after the leaving time represented by the horizontal axis. It is a graph which shows the relationship of. It is a figure which shows an example of the particle size addition curve Pd which shows the particle size distribution of the excavated soil material (locally generated material) at the construction site of a dam. It is a figure corresponding to FIG. 3, and is a graph which shows the result of the compaction test (Example 1) of CSG which added and mixed the setting retarder. It is a figure corresponding to FIG. 3, and is a graph which shows the result of the compaction test (Example 2) of CSG which added and mixed the setting retarder. It is a figure corresponding to FIG. 5, and is a graph which shows the result (Example 1) of the compression test of CSG which added and mixed the setting retarder.

Hereinafter, the CSG (Cemented Sand and Gravel) according to the embodiment of the present invention and the CSG method which is a method for constructing a structure using the CSG will be described with reference to the drawings. In this embodiment, a case where the structure constructed by the CSG method is a dam 101 will be described.

The dam 101 will be described with reference to FIGS. 1 and 2. FIG. 1 is a vertical cross-sectional view of the dam 101, and FIG. 2 is a front view of the dam 101 viewed from the upstream side (in FIG. 1, a view of the dam 101 viewed from the left side). As shown in FIG. 1, the dam 101 is a trapezoidal dam having a trapezoidal cross section. As shown in FIG. 2, the left and right sides of the dam 101 are rocked on the bedrocks 102 and 103, respectively.

The dam 101 according to the present embodiment is constructed by covering the surface of the dam main body portion made of CSG raised in a trapezoidal shape with protective concrete by the CSG method. CSG, which is the material of the dam body, is manufactured by mixing water and cement with excavated soil material (locally generated material) made of gravel, rock mass, etc. that can be obtained near the construction site. The excavated soil material may be treated by removing or crushing the oversized material, but basically no classification, particle size adjustment, or cleaning is performed. For this reason, equipment such as aggregate manufacturing equipment and turbid water treatment equipment required for the construction of a normal concrete dam becomes unnecessary. CSG is a mixture of excavated soil material with cement and water added and mixed, and can be continuously produced by a facility simpler than a concrete production facility.

In the CSG method, the ground is excavated by an excavation machine such as a hydraulic excavator and the excavated soil material (locally generated material) is collected, and the excavated soil material collected in the excavation process is mixed with cement and water. A CSG manufacturing process for manufacturing CSG (mixed material), a transport process for transporting the CSG produced in the CSG manufacturing process to the construction site by a transport machine such as a dump truck, and a laying of the CSG transported in the transport process with a bulldozer or the like. A leveling process of leveling with a leveling machine and a compaction process (compacting process of rolling) in which the CSG leveled in the leveling process is compacted by a compaction machine (compacting machine) such as a vibrating roller. By repeating ,, CSGs are stacked in layers from bottom to top to construct a dam (structure) 101. In addition, between the excavation process and the CSG manufacturing process, an oversize cut is performed to remove the oversized one, if necessary. Further, after the compaction step (compacting step), a placing step of placing protective concrete so as to cover the side surfaces of the upstream side and the downstream side of the CSG layer is performed. The height h of one CSG layer is about 75 cm to 100 cm.

In FIGS. 1 and 2, a dam 101 composed of 6 CSG layers is simply shown. The upper layer of the CSG layer is formed to have a shorter length in the upstream and downstream directions. Therefore, a plurality of stepped portions are formed on the upstream and downstream side surfaces of the dam 101 in an inclined surface or in a stepped manner.

Each CSG layer constituting the dam 101 is constructed by a so-called thin layer rolling method in which the CSG is spread thinly and widely. For example, there are three layers, a lower layer, an intermediate layer, and an upper layer. It is constructed by curing the layers.

Specifically, first, the CSG transported to the construction site by a transport machine such as a dump truck, a conveyor, or a crane is compacted by a leveling machine such as a bulldozer to form a lower layer.

Subsequently, the CSG is conveyed to the upper surface of the spread lower layer by a transfer machine, and the conveyed CSG is compacted by being leveled by the leveling machine to form an intermediate layer. Further, the CSG is conveyed to the upper surface of the leveled intermediate layer by a transfer machine, and the transferred CSG is compacted by leveling with a leveling machine to form an upper layer.

Then, after the upper layer is formed, the surface of the upper layer is compacted by a compaction machine (compacting machine) such as a vibrating roller, and the lower layer, the intermediate layer and the upper layer are compacted. That is, the layer to be leveled on top of the plurality of layers forming the CSG layer is leveled by the leveling machine, then compacted by the compaction machine and compacted. As with the upper layer, the lower layer and the intermediate layer may also be leveled by a leveling machine and then compacted by a compaction machine.

The heights of the lower layer, the intermediate layer, and the upper layer formed in this manner are each set to about 10 cm to 30 cm, and the height h of one layer of the CSG layer is set to about 75 cm to 100 cm.

The dam 101 is constructed by repeating such operations and stacking CSG layers from bottom to top in layers.

Here, in the above-mentioned CSG method, when it takes a long time (for example, about 6 hours at the maximum) from the addition and mixing of cement and water to the excavated soil material (locally generated material) to compaction (compacting). There is. Further, as described above, when the CSG layer is composed of a plurality of layers, vibration occurs after the lowest layer is leveled by a leveling machine or the intermediate layer and the upper layer are leveled. It takes a relatively long time to be compacted by a compaction machine (compacting machine) such as a roller. However, if the time (standing time) from the addition and mixing of cement and water to the excavated soil material to compaction (compacting) is long, the peak strength decreases as the compaction degree of CSG decreases. There's a problem. The details will be described below.

FIG. 3 shows compaction when cement and water are added and mixed with the excavated soil material and then compacted (compacting) after the standing time t (horizontal axis) and the standing time t represented by the horizontal axis have elapsed. It is a graph which shows the relationship with degree (vertical axis). The degree of compaction shown in FIG. 3 is the ratio of the dry density ρd of the mixed material (CSG) compacted after the elapse of the standing time t to the theoretical maximum dry density ρdmax ((ρd / ρdmax) × 100 [. %]).

The theoretical maximum dry density ρdmax will be described with reference to FIG. FIG. 4 is a diagram showing a compaction curve C of the excavated soil material, in which the horizontal axis represents the water content ratio w and the vertical axis represents the dry density ρd. The compaction curve C is a curve showing the relationship between the dry density ρd and the water content ratio w when the excavated soil material is compacted. The compaction curve C is a compaction test in which the excavated soil material is compacted by applying a constant impact energy in a container having a predetermined volume, and the dry density ρd of the compacted excavated soil material is contained while changing the water content ratio w. Obtained by plotting against the ratio w. This compaction curve C can be obtained by a compaction test according to JIS A 1210: 2009 “Soil compaction test method by compaction”. From the compaction curve C, the maximum dry density ρdmax, which is the maximum value of the dry density ρd, and the water content ratio at which the maximum dry density ρdmax can be obtained, that is, the optimum water content ratio wopt, which is the water content ratio that can be compacted most efficiently, are obtained. Be done. In the present embodiment, the maximum dry density ρdmax of the excavated soil material thus obtained is the theoretical maximum dry density of CSG, that is, the standing time t after adding cement and water to the excavated soil material and mixing them. The maximum dry density when = 0.

The degree of compaction shown in FIG. 3 is obtained from the theoretical maximum dry density ρdmax of CSG and the dry density ρd of the mixed material (CSG) compacted after the elapse of the standing time t. The dry density ρd of the compacted mixed material (CSG) is such that after the mixed material (CSG) obtained by adding cement and water to the excavated soil material and mixing is left for a predetermined time, a constant impact energy is applied in a container having a predetermined volume. It is obtained by performing a compaction test (test according to JIS A 1210: 2009) of feeding and compacting.

As shown in FIG. 3, the inventor has found that the degree of compaction decreases as the standing time t increases. This phenomenon does not occur in the compaction of concrete, and the mass of uncleaned excavated soil material and excavated soil material passing through the nominal size of the sieve of 0.15 mm according to JIS A 1204 "Soil particle size test method". It was a phenomenon that the rate exceeded, for example, 3%, 4%, 5%, and 10% of the total excavated soil material. Therefore, it was hypothesized that this is due to the fact that the coagulation reaction in which cement and water react with each other proceeds by adding and mixing cement and water to the excavated soil material. In the case of aggregate for concrete, fine particles are mainly contained in the fine aggregate, and although the sieve has a nominal size of 0.15 mm, the mass fraction is about 5% at the maximum, which is the entire excavated soil material. And it becomes 3% or less. The decrease in the degree of compaction of concrete using such a concrete aggregate (fine aggregate) was small.

Additional testing was done to verify this finding. Hereinafter, as shown in FIG. 4, by adding and mixing cement and water to the excavated soil material, a mixed material (CSG) having a water content ratio w immediately after mixing and a dry density ρd of ρ0 was produced. A case (see S1) will be described as an example. If cement and water are added and mixed with the excavated soil material and then compaction (compacting) is performed on the material immediately, the dry density ρd theoretically rises to the dry density ρ2 on the curve C. (See S4). The conditions for compaction (rolling compaction) are the same as the conditions for obtaining the compaction curve C.

On the other hand, when cement and water are added and mixed with the excavated soil material and then left for a predetermined time, the free water in the mixed material is deprived by the condensation reaction (hydration reaction) in which the cement and water react. Therefore, the water content ratio w decreases with the passage of time after adding and mixing cement and water to the excavated soil material (see S2). As can be seen from the compaction curve C, in the excavated soil material, at a water content ratio w lower than the optimum water content watt, the smaller the water content ratio w, the smaller the dry density ρd. Therefore, it was assumed that the decrease in free water due to the cement condensation reaction (hydration reaction) causes a decrease in the dry density ρd after compaction (compacting).

Further, in the mixed material in which cement and water are added and mixed with the excavated soil material, a network structure in which small crystals called cement gel are entangled with each other is formed by a coagulation reaction (hydration reaction) of cement. Cement gel reticulated structures grow in size and become more complex in shape over time. When such a network structure of cement gel is formed, it becomes difficult to fill the voids when the mixed material (CSG) is compacted (compressed), so that the dry density ρd of the mixed material (CSG) is sufficiently increased. Cannot be made (see S3). For example, the dry density ρd when compaction (compacting) is performed in a state where the water content ratio w is lowered to w0 is ρ1 which is lower than the dry density ρ2 and the dry density on the compaction curve C at the water content ratio w0. ..

In this way, compaction (compacting) is applied to the mixed material (see S2) in which the water content ratio w is lowered due to the cement coagulation reaction (hydration reaction) and the network structure of the cement gel is formed. If this is done, it is assumed that the dry density ρd may not be sufficiently increased (see S3). Therefore, as shown in FIG. 3, the longer the standing time t, the lower the compaction degree. The longer the standing time t, the more the free water decreases due to the coagulation reaction (hydration reaction) of the cement, and further, the cement gel. It was assumed that the main cause was the progress of the formation of the reticulated structure.

FIG. 5 shows the peak strength when compaction (compacting) is performed after the leaving time t (horizontal axis) after adding and mixing cement and water to the excavated soil material and the leaving time t represented by the horizontal axis. It is a graph which shows the relationship with (vertical axis).

The peak strength (compressive strength) was determined by performing a compressive strength test according to JIS A 1108: 1999 “Concrete Compressive Strength Test Method” on a 28-day-old mixed material. In the compressive strength test, a cylindrical core is cut out and collected using a core drill, and the compressive force is loaded on the collected core specimen. The stress-strain curve was obtained based on the displacement of the specimen and the loaded load, and the maximum value of the stress-strain curve was taken as the peak intensity.

As shown in FIG. 3, the degree of compaction decreases as the standing time t after adding and mixing cement and water to the excavated soil material becomes longer. Therefore, as shown in FIG. 5, the peak intensity also decreases as the standing time t after adding and mixing cement and water to the excavated soil material becomes longer.

As described above, from the test results of FIGS. 3 and 5, if the leaving time t from the addition and mixing of cement and water to the excavated soil material (locally generated material) to compaction (compacting) is long, it is left unattended. It can be seen that the degree of compaction of the mixed material (CSG) after compaction (compacting) is lower than that when the time t is short, and the strength of the constructed structure (dam, etc.) is reduced. ..

Here, it is conceivable to suppress a decrease in the compaction degree and peak strength of the mixed material (CSG) by increasing the amount of water added to the excavated soil material (locally generated material). However, the decrease in compaction and peak strength due to the longer standing time t after adding and mixing cement and water to the excavated soil material (locally generated material) is only the decrease in free water in the mixed material. Is not the cause. Therefore, there is a possibility that the decrease in compaction degree and peak strength cannot be effectively suppressed only by increasing the amount of water added to the excavated soil material (locally generated material).

In the present embodiment, the setting retarder delays the coagulation reaction of the cement to delay the reduction of free water and the formation of the network structure of the cement gel, thereby suppressing the decrease in the degree of compaction and the peak strength. The setting retarder is added to the excavated soil material together with cement and water in the CSG preparation step. Examples of cement include Portland cement, mixed cement, and special cement, but Portland cement and mixed cement (blast furnace cement, fly ash cement, etc.) are used for CSG and CSG construction methods. In particular, moderate heat Portland cement, blast furnace cement (class B), Portland cement mixed with fly ash, and moderate heat Portland cement mixed with fly ash cement are preferable.

The CSG according to the present embodiment includes an unwashed excavated soil material, cement, water, and a coagulation retarder having an action of delaying the coagulation reaction of the cement. The unwashed excavated soil material is a material (CSG material) adjusted to a maximum particle size (80 mm) or less by removing oversize as necessary, and JIS A 1204: 2009 "Soil particle size test method". Includes unwashed soil material that passes through the nominal size of the sieve, 5 mm, according to.

The setting retarder is a chemical admixture for concrete that has an excellent effect of economically improving the quality of concrete, and is used for the purpose of delaying the setting and initial hardening of concrete. Examples of the setting retarder include a setting retarder containing siliceous fluoride as a main component and having a delaying action, and a setting retarding agent containing an oxycarboxylic acid salt as a main component for the purpose of delaying setting for a longer period of time than before. The lignin sulfonate and oxycarboxylic acid salt are adsorbed on the surface of the cement particles and temporarily block the contact between the cement and water, thereby delaying the initial hydration reaction. The setting retarder can be selected from various agents that delay the setting reaction of cement. Specifically, as the setting retarder, sodium gluconate, gluconate, oxycarboxylate, ultrafine acrylic polymer emulsion, oxycarboxylic acid compound, polyhydroxycarboxylic acid, lignin sulfonate, and these components are used. An agent containing any of the containing complexes (for example, a complex of a modified lignin sulfonic acid compound and an oxycarboxylic acid compound) as a main component can be selected.

The setting retarder is an admixture according to JIS A 6204: 2011 "Chemical admixture for concrete", and the difference in cement setting time according to JIS A 1147: 2019 "Concrete setting time test method" is the starting time. It is preferable to select one having a characteristic longer than +15 minutes or longer than +0 minutes in the termination time. Furthermore, it is preferable to select one having a characteristic of being longer than +30 minutes in the starting time and longer than +0 minutes in the ending time. The upper limit is preferably less than +90 minutes at the start time and less than +90 minutes at the end time. Further, it is more preferable that the starting time is smaller than +210 and the ending time is smaller than +210 minutes.

For example, as a setting retarder, an admixture according to JIS A 6204: 2011 "Chemical admixture for concrete", which is a water reducing agent delayed type, an AE water reducing agent delayed type, a high-performance AE water reducing agent delayed type, and a fluidizing agent delayed type. It can be selected from the admixtures classified into any of the above. In JIS A 6204: 2011 "Chemical admixture for concrete", the difference in cement setting time according to JIS A 1147: 2019 "Concrete setting time test method" of these chemical admixtures for concrete (condensation delaying agent) is , The starting time is set to +60 minutes to +210 minutes, and the ending time is set to +0 minutes to +210 minutes. Further, as a coagulation delaying agent, it has a property of temporarily stopping the coagulation reaction (hydration reaction) of cement, delaying coagulation for a longer period of time, and then restarting the reaction, that is, so-called super-delay. You can also choose the agent. In both cases of the setting retarder and the super retarding agent, the hydration reaction gradually proceeds after the setting is delayed.

By the way, when constructing a structure using concrete, a setting retarder is used to inject concrete into a formwork having a predetermined shape and fill the entire formwork without gaps before the cement is condensed and hardened by a hydration reaction. May be used. In this case, the setting retarder added and mixed with the concrete is used in the range of about 0.2 to 1.0% in terms of the amount of cement.

On the other hand, in the present embodiment, the setting retarder is added to the CSG formed by mixing water and cement with the excavated soil material (locally generated material). FIG. 6 is a diagram showing an example of the particle size addition curve Pd showing the particle size distribution of the excavated soil material (locally generated material) at the construction site of the dam 101. The curve shown by the alternate long and short dash line in FIG. 6 shows the particle size range of the aggregate for general ready-mixed concrete.

As shown by the solid line in FIG. 6, the excavated soil material (locally generated material) is basically not washed, so that it has finer particles than the aggregate for general ready-mixed concrete (see the alternate long and short dash line). It tends to be included a lot. When a large amount of fine particles is contained, the amount of water absorbed by the fine particles increases. Therefore, the larger the amount of fine particles, the easier it is for the free water of the excavated soil material (locally generated material) to decrease.

In the present embodiment, the setting retarder is added to the CSG containing the excavated soil material (locally generated material) having a large amount of fine particles as compared with concrete. Therefore, in the present embodiment, the effect is obtained by increasing the amount of the setting retarder added to the CSG to be larger than the normal range (0.2 to 1.0% in terms of the amount of cement) when used in concrete. The cement setting reaction was delayed.

For general ready-mixed concrete aggregates, the mass fraction [%] of the sieve, which passes through the nominal size of 0.15 mm according to JIS A 1204: 2009 "Soil particle size test method", is the entire mixed material. On the other hand, it is about 2% or less and has a small amount of fine particles. On the other hand, the excavated soil material with a large amount of fine particles used in the present embodiment is basically a locally generated material that has not been washed. However, it does not mean that it cannot be used if it contains some soil materials that are not locally generated materials or if it contains washed soil materials. Regarding the specific particle size, according to JIS A 1204: 2009 "Soil particle size test method", the mass fraction [%] of the sieve passing through the nominal size of 0.15 mm exceeds 3% of the total excavated soil material. It is a thing. Furthermore, the lower limit of the mass fraction [%] of the sieve passing through the nominal size of 0.15 mm is more than 4%, more than 5%, more than 10%, and 25% with respect to the entire excavated soil material. It is intended for those who exceed. On the other hand, although the excavated soil material passes through the nominal size of the sieve of 0.15 mm, the upper limit of the mass fraction [%] is assumed to be 35% or less, preferably 30% or less of the entire excavated soil material.

In addition, since locally generated materials are basically used, the excavated soil materials used have a large variation as compared with concrete aggregates for ready-mixed concrete. Therefore, the fine particles of the excavated soil material used may temporarily or partly include those smaller or larger than the above values.

(Example)
A coagulation retarder is added to the excavated soil material (locally generated material) collected at the actual site where the dam (structure) 101 is constructed, and a compaction test (according to JIS A 1210: 2009) and a compressive strength test (JIS A) 1108: 1999) was carried out to verify the effect of the coagulation retarder. Table 1 shows the amount of water and the amount of cement per ^{1 m 3} contained in the mixed material (CSG) in this test. Of the CSGs, those excluding water and cement are compounded and designed as excavated soil materials. As the setting retarder used in this test, "Floric T (Floric is a registered trademark)" (manufactured by Floric Co., Ltd.) was added at the ratio shown in Table 1. For "Floric T", the difference in cement setting time according to JIS A 1147: 2019 "Concrete setting time test method" is about +95 minutes at the start time and about +100 minutes at the end time. The amount of the setting retarder added is shown as a ratio to the unit cement amount C (that is, the cement ratio). The compounding design is made by a well-known method. Further, in the present embodiment, the excavated soil material is unwashed, and the mass fraction [%] of the sieve passing through the nominal size of 0.15 mm according to JIS A 1204: 2009 "Soil particle size test method" is mostly. Was more than 3% and less than 15% of the total excavated soil material. In addition, in the excavated soil material used in this test, the mass fraction [%] of the excavated soil material that passes through the nominal size of the sieve of 0.15 mm according to JIS A 1204: 2009 "Soil particle size test method" is 8% of the total excavated soil material. It was more than 10% or less.

The range of the unit cement amount C (kg / m ³ ) contained in 1 m ³ CSG is 50 kg / m ³ (lower limit value) or more, 200 kg / m ³ (upper limit value) or less, preferably 80 kg / m ³ (lower limit value). ) Or more, 130 kg / m ³ (upper limit) or less. The unit water volume W (kg / m ³ ) is 50 kg / m ³ (lower limit) or more, 200 kg / m ³ (upper limit) or less, preferably 80 kg / m ³ (lower limit) or more, 130 kg / m ³ (upper limit). ) Or less, more preferably 90 kg / m ³ (lower limit value) or more and 120 kg / m ³ (upper limit value) or less. The water-cement ratio (W / C) is 0.70 (lower limit value) or more and 1.50 (upper limit value) or less, preferably 0.80 (lower limit value) or more and 1.20 (upper limit value) or less.

7A and 7B are graphs corresponding to FIG. 3 and are graphs showing the results of a compaction test of CSG in which a setting retarder is added and mixed. As shown in FIG. 7A, it can be confirmed that the test result (Example 1) to which the coagulation retarder is added can have a higher degree of compaction than the test result (Reference Example 1) to which the coagulation retarder is not added. It was. Further, it was confirmed that the effect of suppressing the decrease in the degree of compaction by adding the coagulation retarder increases as the standing time t becomes longer. Similarly, even in the test results (Example 2) in which the unit cement amount C is different, as shown in FIG. 7B, the degree of compaction is higher than that in the test results (Reference Example 2) in which the setting retarder is not added. I was able to confirm that I could do it.

By adding 2% of the setting retarder to the unit cement amount C, a compaction (compacting) test is performed after 360 minutes have passed since the addition and mixing of water, cement and the setting retarder. In particular, the degree of compaction in this case exceeds 98 [%] as shown in FIG. 7A, and is 90 [%] or more, which is a preferable degree of compaction, so that a sufficient degree of compaction can be obtained. Was confirmed. It is expected that the larger the amount of the setting retarder added, the higher the effect of suppressing the decrease in the degree of compaction. Therefore, for the setting retarder, for example, the difference in cement setting time according to JIS A 1147: 2019 "Concrete setting time test method" is +60 minutes to +210 minutes at the start time and +0 minutes to +210 minutes at the end time. In the case of the setting retarder, it is preferable to add 2% or more (2% equivalent amount or more) with respect to the unit cement amount C, and at least 1.5% or more (1) with respect to the unit cement amount C. It is preferable to add (1.5% or more).

As described above, the addition amount of the setting retarder (chemical admixture for concrete) indicated by the ratio to the unit cement amount C is preferably determined ^{by the following procedure to determine the specific addition weight (kg / m 3).} The following procedure is an example, and the procedure for determining the addition amount is not limited to this.

First, the unit cement of the mortar specified in JIS R 5201: 2015 "Cement Physical Test", in which the mass composition is cement (ordinary Portland cement): standard sand: water = 1: 3: 0.5. A predetermined test weight ratio (X%) of cement retardant is added to the amount. Then, the test specified in JIS A 1147: 2019 "Concrete setting time test method" is performed.

In this coagulation time test, when a coagulation retarder (admixture) having a difference in coagulation time of +60 to +210 minutes for the starting time and +0 to 210 minutes for the ending time is added to the CSG, the CSG The addition weight ratio (%) of this setting retarder to the unit cement amount C is 0.5 times (lower limit value) or more and 40 times (upper limit value) or less, preferably 1.0 times the test weight ratio (X%). It is set to double (lower limit value) or more, 20 times (upper limit value) or less, more preferably 1.5 times (lower limit value) or more, and 15 times (upper limit value) or less.

Then, in the setting time test using the mortar having the above-mentioned mass compounding ratio to which the setting retarder was added, the difference in setting time was +60 minutes to +210 minutes in the starting time and +0 minutes to 210 minutes in the ending time. If the test weight ratio (X%) of the setting retarder is 1.0%, for example, the addition of the setting retarder added to CSG ^{having a unit cement amount C of 100 kg / m 3} weight (kg / m ³⁾ is, 0.5 kg / m ³ (minimum value) or more, 40 kg / m ³ (upper limit) or less, preferably 1.0 kg / m ³ (minimum value) or more, 20 kg / m ³ ( The upper limit value) or less, more preferably 1.5 kg / m ³ (lower limit value) or more, and 15 kg / m ³ (upper limit value) or less.

On the other hand, in the above-mentioned setting time test, a setting retarder (admixture) having a relatively small difference in setting time, for example, a setting delaying time of +30 to +90 minutes for the starting time and +0 to 90 minutes for the ending time. When added to CSG, the addition weight ratio (%) of this setting retarder to the unit cement amount C of CSG is 0.5 times (lower limit value) or more and 80 times (upper limit value) of the test weight ratio (X%). Hereinafter, it is preferably set to 1.0 times (lower limit value) or more and 40 times (upper limit value) or less.

Further, in the above-mentioned setting time test, a setting delay agent (admixture) having a smaller difference in setting time, for example, a setting time longer than +15 minutes and a closing time longer than +0 minutes is added to CSG. In the case, the addition weight ratio (%) of this setting retarder to the unit cement amount C of CSG is 0.5 times (lower limit value) or more, 120 times (upper limit value) or less, preferably 120 times (upper limit value) or less of the test weight ratio (X%). , 1.0 times (lower limit value) or more and 60 times (upper limit value) or less.

As described above, the setting retarder added to CSG is a chemical admixture for concrete, which has been confirmed to have a certain delay in the setting time measured in the state of being added to the mortar having the above mass compounding ratio. It should be. Further, the added weight ratio (%) of CSG to the unit cement amount C may be changed according to the degree of the confirmed delay in the setting time. For example, the upper limit of the added weight ratio (%) is set to the setting time. The coagulation retarder having a larger delay may be smaller, and the coagulation retarder may be larger as the coagulation delayer has a smaller delay. As a result, when a setting retarder having a relatively large delay in setting time is used, it is possible to suppress an increase in the construction cost of the structure by reducing the amount of the setting retarder added to the CSG.

In addition, the difference in setting time tends to decrease as the temperature rises and increases as the temperature decreases. Therefore, the weight ratio (%) of CSG added to the unit cement amount is corrected by the environmental temperature and the daily average temperature. To. Specifically, when the environmental temperature or air temperature rises, the amount of the coagulation retarder added is increased, and when the environmental temperature or air temperature decreases, the amount of the coagulation retarder added decreases. As a result, for example, when it is expected that the days when the average temperature is low will continue, the construction cost of the structure can be reduced by reducing the amount of the setting retarder added to the CSG, and the average temperature can be reduced. When it is expected that the days when the temperature is high will continue, the decrease in the degree of compaction of CSG after compaction can be surely suppressed by increasing the amount of the setting retarder added to CSG.

FIG. 8 is a diagram corresponding to FIG. 5, and is a graph showing the results of a compression test of CSG in which a setting retarder is added and mixed. As shown in FIG. 8, it was confirmed that the test result to which the coagulation retarder was added (Example 1) could have a higher peak intensity than the test result to which the coagulation retarder was not added (Reference Example 1). .. Further, when the compression test is performed after 360 minutes have passed from the addition and mixing of water, cement and the setting retarder by adding 2% of the setting retarder to the unit cement amount C. The peak intensity was higher than that when the standing time was 30 minutes, and it was confirmed that a sufficient peak intensity could be obtained. From this point of view, it can be said that it is preferable to add 2% or more (2% equivalent amount or more) of the setting retarder with respect to the unit cement amount C. Similarly, it is confirmed that even in the test results (Example 2) in which the unit cement amount C is different, the peak intensity can be increased as compared with the test results (Reference Example 2) in which the setting retarder is not added.

According to the above-described embodiment, the following effects are exhibited.

The CSG according to the present embodiment includes excavated soil material, cement, water, and a coagulation retarder having an action of delaying the coagulation reaction of cement. By delaying the coagulation reaction of the cement contained in CSG with the coagulation retarder, it is possible to suppress the decrease of free water and the formation of the network structure of the cement gel. Therefore, it may take a long time from the addition and mixing of cement and water to the excavated soil material (locally generated material) to compaction (compacting), or it may be the lowest layer in the CSG layer composed of multiple layers. After compaction (after compaction) even if it takes a relatively long time to be compacted together with the intermediate layer and upper layer by the compaction machine (compacting machine) after being leveled by the leveling machine. It is possible to suppress a decrease in the degree of compaction of CSG, and to ensure the quality of compaction characteristics. As a result, it is possible to suppress a decrease in the strength (peak strength) of the dam (structure) 101.

In particular, the excavated soil material (locally generated material) is basically an uncleaned excavated soil material that is not washed, and therefore contains a large amount of fine particles. Specifically, the excavated soil material passes through the nominal size of the sieve of 0.15 mm according to JIS A 1204: 2009 "Soil particle size test method", but the mass fraction exceeds 3% of the total excavated soil material. It preferably exceeds 5%. As described above, in the excavated soil material containing a large amount of fine particles, free water is likely to be reduced as compared with concrete because water is absorbed by the fine particles. In the present embodiment, as described above, the cement setting reaction is effective by adding a setting retarder in an amount exceeding the range normally used in concrete (for example, 2% or more with respect to the unit cement amount C). It was delayed to suppress the decrease of free water and the formation of the reticulated structure of cement gel. Therefore, in the CSG containing a large amount of fine particles, it is possible to suppress a decrease in the compaction degree and the peak strength of the CSG after compaction (rolling).

<Modification example 1>
In the above embodiment, an example in which the excavated soil material is unwashed has been described, but a part of the excavated soil material that has been washed may be mixed. At a minimum, the CSG may contain unwashed excavated soil material.

<Modification 2>
In the above embodiment, the case where the structure constructed by the CSG method is the dam 101 has been described, but the present invention is not limited to this. The present invention can be applied to a CSG method for constructing various structures using CSG in which a setting retarder is added and mixed.

<Modification example 3>
In the above embodiment, as the setting retarder, any of a water reducing agent delayed type, an AE water reducing agent delayed type, a high-performance AE water reducing agent delayed type, and a fluidizing agent delayed type is used according to JIS A 6204: 2011 “Chemical admixture for concrete”. Although an example in which an admixture classified into the above or an ultra-delaying agent that positively delays the cement setting reaction is selected has been described, the present invention is not limited to this. Select the standard type of water reducing agent, the standard type of AE water reducing agent, the standard type of high-performance AE water reducing agent, and the standard type of fluidizing agent, which can delay the coagulation reaction of cement as compared with the case where they are not added. You can also. For example, among the water reducing agent standard type, AE water reducing agent standard type, high-performance AE water reducing agent standard type, and fluidizing agent standard type, the difference in cement setting time according to JIS A 1147: 2019 "Concrete setting time test method" is , The starting time longer than +15 minutes and the ending time longer than +0 minutes may be selected and added to CSG. As a result, it is possible to suppress a decrease in the degree of compaction and the peak intensity over time as compared with the case where the selected setting retarder is not added. ^{The amount of the chemical admixture used per 1 m 3} in JIS A 1147: 2019 "Concrete setting time test method" may be determined with reference to the amount recommended by the manufacturer. However, if the amount recommended by the manufacturer is unknown, or if the amount recommended by the manufacturer is different from the actual amount used, use the actual admixture ratio to the unit cement amount C added to CSG. As the amount, it is preferable to carry out the test of "concrete setting time test method".

Although the embodiments of the present invention have been described above, the above embodiments are only a part of the application examples of the present invention, and the technical scope of the present invention is limited to the specific configurations of the above embodiments. Absent.

101 ... Dam (structure)

Claims (6)

Unwashed excavated soil material and
With cement
water and,
A coagulation retarder having an action of delaying the coagulation reaction of the cement, and the like.
CSG. Excavated soil material and
With cement
water and,
Containing, a coagulation retarder having an action of delaying the coagulation reaction of the cement.
The excavated soil material passes through the nominal size of the sieve of 0.15 mm according to JIS A 1204 “Soil particle size test method”, but the mass fraction exceeds 3%.
CSG. The setting retarder is an admixture according to JIS A 6204 "Chemical admixture for concrete", and the difference in cement setting time according to JIS A 1147 "Concrete setting time test method" is greater than +15 minutes at the initial starting time. Long and longer than +0 minutes in closing time,
The CSG according to claim 1 or 2. The coagulation retarder is classified into one of a water reducing agent delayed type, an AE water reducing agent delayed type, a high-performance AE water reducing agent delayed type, and a fluidizing agent delayed type according to JIS A 6204 “Chemical admixture for concrete”. Is an agent,
The CSG according to any one of claims 1 to 3. The excavated soil material includes a soil material passing through a nominal size of 5 mm of a sieve according to JIS A 1204 “Soil particle size test method”.
The CSG according to any one of claims 1 to 4. A CSG method for constructing a structure by stacking the CSGs in layers by repeating the steps of leveling and compacting the CSGs according to any one of claims 1 to 5.