JP4375663B2 - Cement composition for jet grouting method and jet grouting method - Google Patents

Description

  The present invention relates to a cement composition for a jet grouting method, and a jet grouting method using the same, and more specifically, a jet grouting method for use in improving the ground by creating a cylindrical hardened body of about 0.5 to 5 m in the ground. The present invention relates to a cement composition and a jet grout method.

  Generally, as a method of injecting chemicals into the ground, solidifying the ground, increasing the strength, decreasing the water permeability, and as a method of injecting substances to achieve those purposes, Chemical solution injection methods such as a high-pressure injection injection method, a water glass injection method, a bentonite injection method, and a urethane injection method are performed.

  In addition, the high pressure injection injection method includes a CCP method (Chemical Churning Pile) and a jet grout method as a method for improving the ground by injecting cement milk at an ultrahigh pressure while rotating.

  The jet grout method is roughly classified into two types.

  The first is to spray compressed air and cement milk while rotating into the ground at an ultra-high pressure to cut the ground in a short time, and at the same time to apply the slime mixed with the excavated soil and cement milk generated during excavation. Is a JSG method (Jumbo-Jet Special Grout Method) that creates a cylindrical hardened body, and one is to spray ground while rotating compressed air and ultra-high pressure water in the ground, It is a column jet grouting method in which the slime is discharged to the ground surface and filled with cement milk at the same time to form a cylindrical hardened body.

  However, in these construction methods, when cement milk is mixed with clay soil or clay with clay by high-pressure jetting, the viscosity increases or the injection becomes incomplete, and slime generated when the ground is cut is not generated. There was a problem that the ground was not lifted by the injection pressure, and the ground was not improved.

  In addition, when water is added so that the slime is likely to rise, the amount of slime increases, the processing costs increase, and the pile strength also decreases.

  Furthermore, techniques have been developed that use phosphate to obtain similar results. However, phosphorus eutrophies the environment and pollutes rivers and lakes, and its use is not preferred.

  As a result of various studies to solve the problems in the jet grout method, the present inventor can solve the problems and improve the solid ground by using a specific cement composition. Obtaining knowledge, the present invention has been completed.

That is, the present invention relates to (1) one or more selected from 0.1 to 30 parts by weight selected from sodium carbonate, lithium carbonate, and potassium carbonate, and (2) 0.1 to 20 inorganic bicarbonates per 100 parts by weight of cement. And (3) a cement admixture for jet grouting method comprising 0.1 to 30 parts by weight of phosphate and / or 1 to 40 parts by weight of inorganic sulfate with respect to a total of 100 parts by weight of cement and the cement admixture. , A cement composition for jet grout method , contained within the range of 0.5 to 30 parts by weight , and (1) one kind selected from sodium carbonate, lithium carbonate, and potassium carbonate with respect to 100 parts by weight of cement Alternatively, for jet grout method comprising 0.1 to 30 parts by weight of two or more , (2 ') 0.5 to 20 parts by weight of ammonium salt, and (3) 0.1 to 30 parts by weight of phosphate and / or 1 to 40 parts by weight of inorganic sulfate . the cement admixture, Se Against cement and the cement admixture 100 parts by weight of the total, a jet grouting method cement composition comprising in the range of 0.5 to 30 parts by weight, further, the cement admixture is for the jet grouting method, The jet grouting method cement composition comprising 0.1 to 30 parts by weight of a phosphate and 1 to 40 parts by weight of an inorganic sulfate with respect to 100 parts by weight of the cement, and the jet grouting method cement composition, This is a jet grout method characterized by high-pressure injection of cement milk mixed with water into the ground, mixing with soil, and hardening.

By using a cement admixture containing sodium carbonate, lithium carbonate, and potassium carbonate, and a composition containing cement, the amount of phosphate used can be reduced, and jet grouting with excellent strength and economy It was possible to obtain a cement composition for a construction method, and it was possible to provide fluidity that was sufficiently satisfactory in construction. The combination of inorganic bicarbonate and inorganic sulfate, and the combined use of ammonium and inorganic sulfate eliminates the need to use phosphate, and is a cement admixture for jet grouting with excellent workability without the possibility of phosphorus pollution Could be developed.

Hereinafter, the present invention will be described in more detail.
In the present invention, (1) 0.1 to 30 parts by weight of one or more selected from sodium carbonate, lithium carbonate and potassium carbonate and (2) 0.1 to 20 parts by weight of inorganic bicarbonate or (2 ′) ammonium salt 0.5 For jet grouting method comprising: -20 parts by weight and (3) 0.1 to 30 parts by weight of phosphate and / or 1 to 40 parts by weight of inorganic sulfate 1 to 40 parts by weight of cement admixture for jet grouting and 100 parts by weight of cement the cement composition to use.

  One or more carbonates selected from sodium carbonate, lithium carbonate, and potassium carbonate have the property of improving strength expression by adding an appropriate amount. Specifically, sodium carbonate , Lithium carbonate, and potassium carbonate, and one or more of these can be used. Among these, sodium carbonate is preferably used from the viewpoints of anti-caking property and strength development. The particle sizes of sodium carbonate, lithium carbonate, and potassium carbonate can be used without any problem as long as they are generally commercially available products. However, in consideration of solubility, use of 0.3 mm or less is preferable. The amount of sodium carbonate, lithium carbonate, and potassium carbonate used is preferably 0.1 to 30 parts by weight and more preferably 1 to 20 parts by weight with respect to 100 parts by weight of cement. If the amount is less than 0.1 parts by weight, strength development cannot be expected, and if it is used in excess of 30 parts by weight, the initial strength development may be reduced.

  In the present invention, a cement admixture for jet grouting method is used, in which a cement admixture containing one or more selected from sodium carbonate, lithium carbonate, and potassium carbonate and a cement are blended at a specific ratio. The cement admixture can also be used in combination with inorganic bicarbonate, ammonium salt, phosphate and / or inorganic sulfate.

  Examples of the inorganic bicarbonate according to the present invention include alkali bicarbonates such as sodium bicarbonate and potassium bicarbonate.

  The particle size of the inorganic bicarbonate is not particularly limited, and is usually sufficient as it is commercially available.

  The amount of inorganic bicarbonate used is preferably 100 parts by weight or less, more preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of cement from the viewpoint of reducing the slime viscosity of the jet grout and reducing the amount of slime generated. . If the amount exceeds 100 parts by weight, the cement-clay mixture may condense in a short time and the injection tube may be blocked.

  As the ammonium salt according to the present invention, any of ammonium sulfate, ammonium carbonate, ammonium bicarbonate, ammonium acetate, ammonium nitrate, ammonium phosphate, ammonium citrate, and aluminum ammonium sulfate can be used. Of these, ammonium sulfate is preferred from the standpoint of strength development and easy availability and low cost. In addition, ammonium sulfate is generally used as a fertilizer and has little risk of causing environmental destruction.

  The particle size of the ammonium salt can be used as long as it is that of a commercially available product, but it is preferably 0.3 mm or less in consideration of solubility.

  The amount of ammonium salt used is preferably 0.5 to 20 parts by weight and more preferably 1 to 10 parts by weight with respect to 100 parts by weight of cement. If the amount is less than 0.5 parts by weight, it is difficult to prevent the cement from condensing. If the amount exceeds 20 parts by weight, the working environment may be deteriorated due to an ammonia odor.

  Here, phosphates include monosodium phosphate, disodium phosphate, trisodium phosphate, sodium pyrophosphate, sodium tripolyphosphate, sodium trimetaphosphate, sodium hexametaphosphate, and sodium tetrapolyphosphate or potassium salts thereof. Any of these can be used, but monosodium phosphate and sodium tripolyphosphate are preferred from the standpoints of preventing condensation and developing strength.

  Also, water-soluble phosphates that increase fluidity when mixed with cement or soil can be used.

  The particle size of the phosphate is not particularly limited, and any particle size of a commercially available product can be used, but from the viewpoint of solubility, use of 0.3 mm or less is preferable.

  The amount of phosphate used is preferably 0.1 to 30 parts by weight and more preferably 1 to 10 parts by weight with respect to 100 parts by weight of cement. If the amount is less than 0.1 parts by weight, it is difficult to prevent the cement from congealing, and if it exceeds 30 parts by weight, the short-term strength may be lowered.

  Examples of the inorganic sulfate include calcium sulfate, sodium sulfate, potassium sulfate, and magnesium sulfate, and one or more of these can be used.

  In addition, alum represented by aluminum sulfate and calcined alum stone obtained by firing alumite can be used.

Among these, the use of sulfuric acid calcium are preferable from the viewpoint of anti-caking properties and strength development.

The particle size of the inorganic sulfate is preferably 2,000 cm ² / g or more in terms of brain value.

  The amount of inorganic sulfate used is preferably 1 to 100 parts by weight and more preferably 2 to 40 parts by weight with respect to 100 parts by weight of cement. If it is less than 1 part by weight, it is difficult to prevent the cement from congealing, and if it exceeds 100 parts by weight, the initial strength may be poor.

In the present invention, inorganic sulfites can also be used. As the inorganic sulfite, sodium bisulfite is preferable as shown in the Examples, and as shown in Table 2, strength development is achieved by using 1 to 100 parts by weight with respect to 100 parts by weight of cement. The viscosity can be reduced without hindering.

Cement admixture for jet grouting method comprising one or more selected from sodium carbonate, lithium carbonate, and potassium carbonate , inorganic bicarbonate or ammonium salt, and phosphate and / or inorganic sulfate Is used in an amount of 0.5 to 30 parts by weight, more preferably 1 to 20 parts by weight, based on 100 parts by weight of the cement and the cement admixture. If it is less than 0.5 part by weight, it is difficult to prevent the cement from agglomerating when mixed with soil, and if it exceeds 30 parts by weight, the initial strength may be poor.

  Here, various types of Portland cements such as normal strength, ultra-high strength, and moderate heat, various mixed cements obtained by mixing blast furnace slag and fly ash with these Portland cements, alumina cements, fast-hardening cements, calcium Examples include cement containing or containing sulfoaluminate, and commercially available fine particle cement.

  The amount of water used in the present invention is not particularly limited, but for example, it is preferable to use 50 to 300 parts by weight with respect to 100 parts by weight of the cement composition.

  In the present invention, a cement admixture such as bentonite or a water reducing agent can be used in combination depending on the state of the soil. In particular, the combined use of a high performance water reducing agent is effective.

  The mixing and stirring conditions in the present invention are not particularly limited, but it is preferable to mix the cement composition and water in advance with a grout mixer rotating at a rotational speed of about 10 to 1,000 rpm.

  Next, the jet grouting method using the cement composition for jet grouting method of the present invention will be described.

  First, drill holes where ground improvement is required. The depth of the drilling hole is not particularly limited, but is usually about 20 to 50 m. The diameter of the drilling hole is not particularly limited as long as the rod can be inserted.

  Next, double or triple rods are inserted, and cement milk made of the jet grout cement composition is pumped and injected using a grout pump, an ultrahigh pressure pump, a compressor, or the like.

The pumping pressure of cement milk is preferably higher, but it is usually performed at about 50 to 700 kg / cm ² in consideration of nozzle wear and the like.

  Although the amount of liquid feeding is not particularly limited, it is preferably about 30 to 200 liters / min.

  The columnar diameter into which the cement milk is filled varies greatly depending on the filling depth. For example, when the filling depth is 15 to 40 m, 1 to 5 m is appropriate.

  In addition, the cement composition for jet grouting method of the present invention is effective for all methods of mixing soil and cement, and is not limited to just for grouting method. Can be used.

  As shown in Table 1, the inorganic bicarbonate A, an inorganic salt A, is mixed with 100 parts by weight of cement as shown in Table 1, the water / cement composition ratio is 150%, and mixed for 2 minutes with a mortar mixer to prepare cement milk. did.

  A diatomaceous earth exhibiting the same properties as viscous soil when mixed with water and this cement milk were further mixed for 2 minutes with a mortar mixer at a volume ratio of 1: 1 to prepare a mixture.

  The viscosity of this mixture was measured with a B-type viscometer for a predetermined time, and further, this mixture was placed in a 4 × 4 × 16 cm mold and cured, and the compression strength at a predetermined age was measured using a specimen. The results are also shown in Table 1.

<Materials used>
Cement: Ordinary Portland cement inorganic salt A manufactured by Denki Kagaku Kogyo Co., Ltd .: Inorganic bicarbonate, sodium bicarbonate, reagent grade diatomaceous earth: NITALC. Main component SiO ₂

As is clear from Table 1, when the amount of inorganic bicarbonate used is increased, the viscosity of the slime tends to decrease gradually, and the amount used increases from about 5 parts by weight. However, there is a tendency that the additive effect is not seen.

  The same procedure as in Example 1 was performed except that an inorganic salt was mixed as shown in Table 2 with respect to 100 parts by weight of cement. The results are also shown in Table 2.

<Materials used>
Inorganic salt B: Inorganic sulfite, sodium hydrogen sulfite, reagent primary inorganic salt C: Inorganic carbonate, sodium carbonate, reagent primary inorganic salt D: Ammonium salt, ammonium sulfate, reagent primary

As is clear from the table, the effect of decreasing the viscosity was observed without inhibiting the strength development.

  The same procedure as in Example 1 was performed except that an inorganic salt was mixed as shown in Table 3 with respect to 100 parts by weight of cement. The results are also shown in Table 3.

As is clear from the table , by using the inorganic salt in combination, the effect of reducing the viscosity was obtained, and the viscosity was further reduced as compared with the case where each was used alone, and the synergistic effect by the combined use was obtained.

  The same procedure as in Example 1 was performed except that an inorganic salt was mixed as shown in Table 4 with respect to 100 parts by weight of cement. The results are also shown in Table 4.

As is apparent from the table , when three or more inorganic salts are used in combination, the effect of reducing the viscosity is exhibited.

  The same procedure as in Example 1 was performed except that an inorganic salt was mixed as shown in Table 5 with respect to 100 parts by weight of cement. The results are also shown in Table 5.

<Materials used>
Inorganic salt E: Phosphate, monosodium phosphate manufactured by Yoneyama Chemical Co. F: Phosphate, sodium tripolyphosphate manufactured by Yoneyama Chemical

As is clear from the table , even when phosphate and other inorganic salts are used in combination, the viscosity reducing effect is not lost, and the amount of phosphate used can be reduced.

  The same operation as in Example 1 was conducted except that inorganic salts were mixed as shown in Table 6 with respect to 100 parts by weight of cement. The results are also shown in Table 6.

<Materials used>
Inorganic salt G: Inorganic sulfate, crushed anhydrous gypsum manufactured by Shin-Akita Kasei Chemical Co., Ltd.
Brain value 5,700cm ² / g

As is apparent from the table , the long-term strength can be improved by using the inorganic sulfate G, which is the inorganic salt G, in combination.

The same procedure as in Example 1 was performed except that an inorganic salt was mixed as shown in Table 7 with respect to 100 parts by weight of cement. The results are also shown in Table 7.

As is apparent from the table , the combined use of phosphate and inorganic sulfate G, which is inorganic salt G, does not lose the viscosity-reducing effect, and the amount of phosphate used can be reduced, improving long-term strength. It becomes possible.

  Example 1 except that the cement admixture for jet grouting method comprising 2 parts by weight of inorganic salt A, 2 parts by weight of inorganic salt B, and 6 parts by weight of inorganic salt G was changed as shown in Table 8 with respect to 100 parts by weight of cement. As well as. The results are also shown in Table 8.

As is apparent from the table , an increase in the viscosity reduction effect can be expected by increasing the use ratio of the cement admixture.

  Actually, in the same manner as in Example 1 in order to further evaluate the practicality using the cement admixture blended with inorganic salts as shown in Table 9 using the clay soil at the construction site. The results are shown in Table 9.

<Materials used>
Cohesive soil: Volcanic ash cohesive soil (Yurakucho Formation), moisture content 108%

As is clear from the table, even when using clay soil at the actual construction site, it shows a good viscosity drop, and the compressive strength is a strength that does not cause any problems in construction, and it is expressed over 20 kgf / cm ² at 28 days of age. Yes.

Using the formulation shown in Table 10, cement milk having a water / cement composition ratio of 150% was prepared, and the JSG method was carried out at a depth of 20 m and an injection pressure of 200 kg / cm ² .

  As a result, the increase in slime was very good even in the viscous soil having an N value of 0 indicating the hardness of the soil, the slime did not harden even in 3 hours, and the slime treatment proceeded very smoothly. After excavation after construction, a pile-shaped cured body having a diameter of about 2 m was confirmed. The compressive strength of the piled cured body was measured. The results are also shown in Table 10.

  For comparison, the same procedure was performed without using the cement composition of the present invention. However, the viscosity of the slime increased considerably, there was no fluidity, and the slime expanded into the gap between the casings, that is, the surrounding ground expanded. .

Claims (4)

(1) Sodium carbonate relative to the cement 100 parts by weight, lithium carbonate, and one or two or more of 0.1 to 30 parts by weight selected from potassium carbonate and (2) an inorganic bicarbonate 0.1 to 20 parts by weight (3) 0.5 to 30 parts by weight of a cement admixture for jet grouting method comprising 0.1 to 30 parts by weight of phosphate and / or 1 to 40 parts by weight of inorganic sulfate with respect to a total of 100 parts by weight of cement and the cement admixture A cement composition for a jet grout method , which is contained within the above range . (1) 0.1-30 parts by weight of one or more selected from sodium carbonate, lithium carbonate and potassium carbonate , (2 ') 0.5-20 parts by weight of ammonium salt and (3) phosphorus with respect to 100 parts by weight of cement The cement admixture for jet grouting method, comprising 0.1 to 30 parts by weight of acid salt and / or 1 to 40 parts by weight of inorganic sulfate , is 0.5 to 30 parts by weight with respect to 100 parts by weight of cement and the cement admixture in total. A cement composition for a jet grout method , which is contained within the range . The jet according to claim 1 or 2, wherein the cement admixture for jet grouting method comprises 0.1 to 30 parts by weight of phosphate and 1 to 40 parts by weight of inorganic sulfate with respect to 100 parts by weight of cement. Cement composition for grout method.   A cement milk obtained by mixing the cement composition for jet grouting method according to any one of claims 1 to 3 with water is injected into the ground at high pressure, and is mixed with soil and hardened. Jet grout method.