JP6547455B2 - Ground improvement material and ground improvement method - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a ground improvement material which is excellent in solidification strength even in soils such as loam and organic soil which are less likely to have strength than ordinary ground improvement materials.

  When building structures such as roads and buildings, the strength of the ground becomes a problem. For this reason, ground improvement is generally performed by adding cement or the like to the soil to solidify it to increase its strength. However, with respect to soils such as loam and organic soils, the strength improvement is reduced with ordinary ground improvement materials. Such a decrease in strength development is considered to be mainly due to organic substances that inhibit the hydration reaction of cement, and a ground improvement material capable of obtaining sufficient solidification strength even for loam and organic soil is desired ing.

As ground improvement materials that easily develop strength in such soil, Patent Document 1 discloses 11CaO · 7Al ₂ O ₃ · CaX ₂ (X is a halogen), CaO · Al ₂ O ₃ , 12CaO · 7Al ₂ O ₃ , calcium aluminate such _{4CaO · 3Al 2 O 3 · SO} 3 is a hydraulic material consisting mainly soil improvement material is disclosed that contains.

Japanese Examined Patent Publication No. 6-78524

However, the clinker used for the ground improvement material described in Patent Document 1 contains a large amount of halogen such as Cl and SO ₃ . These circulate in the cement kiln and form a coating on a relatively low temperature portion in the kiln to cause coating troubles, which is not practical because of serious problems in manufacturing.

  An object of the present invention is to provide a ground improvement material which is excellent in strength developing property even in a soil having low strength even without using special clinker minerals which are difficult to manufacture as described above. Another object of the present invention is to provide a ground improvement method using the above ground improvement material.

  As a result of intensive studies on the above problems, the present inventors have found that even in a soil that is difficult to obtain strength by coexistence of cement clinker, gypsum, calcium aluminate hydrate, and calcium silicate hydrate. It has been found that a ground improvement material excellent in expression can be obtained, and the present invention has been completed.

  That is, the present invention is a ground improvement material containing cement clinker, gypsum, and inorganic powder, wherein the inorganic powder contains calcium aluminate hydrate and calcium silicate hydrate. Provide a ground improvement material as a feature.

  The above-mentioned ground improvement material can exhibit sufficient strength expression also to the soil (for example, loam and organic soil) in which it is difficult to secure sufficient solidification strength with the conventional ground improvement material. Although the main cause is not necessarily clear, the calcium aluminate and calcium silicate contained in the inorganic powder both have similar structures to the hydrate of the ground improvement material, and thus particularly preferably promote hydration It is thought that. Here, it is preferable that 0.1 to 5.0 parts by mass of calcium aluminate hydrate and calcium silicate hydrate are contained as the inorganic powder with respect to 100 parts by mass of the total amount of cement clinker and gypsum. When the ground improvement material contains blast furnace slag, calcium aluminate hydrate and calcium silicate hydrate are used as the inorganic powder with respect to 100 parts by mass of cement clinker, gypsum and blast furnace slag in total. It is desirable to contain 0.1-5.0 mass parts of each. Within such a range, the strength development of the ground improvement material is improved.

It is preferable that the said ground improvement material further contains a suitable amount of blast furnace slag from a viewpoint of utilization of industrial waste, and the elution amount reduction amount of a heavy metal. The content of blast furnace slag may be 5 to 80 parts by mass with respect to 100 parts by mass of the ground improvement material. Moreover, from the viewpoint of strength development, the amount of SO ₃ in the ground improvement material may be 1.5 to 15.0 parts by mass with respect to 100 parts by mass of the total mass of the ground improvement material.

  If the content of ettringite in the inorganic powder is 10% by mass or more as a quantitative value by Rietveld analysis of a powder X-ray diffraction pattern, the initial strength of the ground improvement material is improved. Moreover, if Ca / Si ratio of the said calcium silicate hydrate is 0.5-5.0, the strength expression property of a ground improvement material will improve.

  The cement clinker may contain a relatively large amount of free lime (f. CaO). For example, the free lime (f. CaO) content of the clinker may be less than 8.0% by mass.

The cement clinker is an environmental load reduction clinker, and its hydraulic coefficient (HM) is 1.75 to 2.20, silicic acid ratio (SM) is 1.50 or more and less than 2.50, iron ratio (IM) is 3 The amount of C ₃ A calculated by the Borg equation is 15% by mass or more, and the amount of C ₄ AF is 0.5 to 10% by mass. The range setting of these various factors (hydraulic factor, silicic acid factor and iron factor) reduces the amount of CO ₂ generated in the manufacturing process by lowering the firing temperature, and at the same time, for example, industrial byproducts It is because it uses a relatively large amount of coal ash (fly ash, bottom ash, etc.). In addition, setting the amounts of the interstitial phase (C ₃ A amount and C ₄ AF amount) relatively high also contributes to lowering the firing temperature. In addition, the use of the environmental load reduction clinker further enhances the strength development of the ground improvement material.

The cement clinker is, for example, a waste or by-product having an Al ₂ O ₃ content of 10% by mass or more and a SiO ₂ / Al ₂ O ₃ mass ratio of 5.0 or less, 250 to 600 kg / t-cl ′ iron material amount ₂ O ₃ is not less than 30 wt% was a 30kg / t-cl 'hereinafter as a raw material, it can be manufactured through a step of firing the raw material at a firing temperature of 1,200-1,450 ° C.. By using less than 30 kg / t-cl '(also when not using iron (0 kg / t-cl')), heavy metals contained in iron (such as copper glaze) can be used as clinker The amount brought in can be reduced sufficiently. For example, in the above environmental impact reduction clinker, the Mo content is preferably 30 mg / kg or less, the total Cr content is preferably 100 mg / kg or less, and the Pb content is 100 mg / kg or less preferable.

  The inorganic powder is an inorganic powder produced using EP dust and / or chlorine bypass dust generated in the cement production process as a raw material. By using such an inorganic powder, waste utilization can be further promoted.

  The present invention provides a ground improvement method using the above ground improvement material. According to the ground improvement method using the ground improvement material, excellent solidified treatment strength can be obtained even in a soil with low strength such as loam or organic soil.

  The ground improvement material according to the present invention has the effect of being excellent in strength development even in a low-strength soil such as loam and organic soil, and having various cement clinkers including a general portland cement clinker available.

It is an example of the X-ray-diffraction pattern of calcium aluminate hydrate powder.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

<Ground improvement material>
The ground improvement material of the present embodiment includes a cement clinker, gypsum, and an inorganic powder including calcium aluminate hydrate. This ground improvement material can exhibit sufficient strength expression even to a soil (for example, loam or organic soil) which has been difficult to secure sufficient solidification strength with the conventional ground improvement material.

(Cement clinker)
Examples of the cement clinker include various cement clinkers such as common portland cement clinker, early strong portland cement clinker and the like. The following environmental load reduction clinkers may be used with or instead of these cement clinkers. By using an environmental load reduction clinker, waste and industrial by-products can be sufficiently used effectively as part of the raw material, and the amount of CO ₂ generated in the production process can be sufficiently reduced.

The above environmental impact reduction clinker has a hydraulic modulus (HM) of 1.75 to 2.20, a silicic acid ratio (SM) of 1.50 to less than 2.50, and an iron ratio (IM) of 3.0 to 10. It is 0 and the amount of C ₃ A calculated by the Borg equation is 15% by mass or more, and the amount of C ₄ AF is 0.5 to 10% by mass.

The hydraulic modulus (HM) of the environmental load reduction clinker is calculated by the following equation (1). The hydraulic rate of the environmental load reduction clinker is 1.75 to 2.20 (1.75 to 2.20). When the hydraulic ratio is less than 1.75, the hydraulic property of the ground improvement material is likely to be reduced, and the strength development tends to be insufficient. On the other hand, if the hydraulic modulus exceeds 2.20, the firing temperature in the process of producing the environmental impact reduction clinker can not be lowered sufficiently. The hydraulic coefficient of the environmental load reduction clinker is preferably 1.85 to 2.20, more preferably 1.95 to 2.20, and still more preferably 2.00 to 2.20.
HM = CaO / (SiO ₂ + Al ₂ O ₃ + Fe ₂ O ₃ ) (1)

The silicic acid ratio (SM) of the environmental load reduction clinker is calculated by the following equation (2). The silica rate of the environmental load reduction clinker is 1.50 or more and less than 2.50. If the silicic acid ratio is less than 1.50, it is difficult to obtain an environmental load reduction clinker having an appropriate composition. On the other hand, when the silicic acid ratio is 2.50 or more, it is difficult to increase the amount of waste used as compared to the conventional Portland cement clinker, and the production cost of the environmental load reduction clinker rises. The silica rate of the environmental load reduction clinker is preferably 1.60 to 2.30, more preferably 1.80 to 2.05.
SM = SiO ₂ / (Al ₂ O ₃ + Fe ₂ O ₃ ) (2)

The iron percentage (IM) of the environmental load reduction clinker is calculated by the following equation (3). The iron rate of the environmental load reduction clinker is 3.0 to 10.0. If the iron ratio is less than 3.0, it is difficult to increase the amount of waste or industrial by-products as compared to the conventional Portland cement clinker, and the production cost of the environmental load reduction clinker increases. On the other hand, when the iron ratio exceeds 10.0, the fluidity of the slurry obtained by adding water to the ground improvement material containing the environmental load reduction clinker deteriorates. The iron ratio of the environmental load reduction clinker is preferably 3.5 to 9.0, more preferably 4.0 to 8.5, and still more preferably 5.0 to 8.0.
IM = Al ₂ O ₃ / Fe ₂ O ₃ (3)

The cement clinker contains C ₃ A, C ₄ AF, C ₃ S and C ₂ S, and its composition can be calculated by the Borg equation. The Borg equation is a formula for determining the content of major four minerals in cement clinker. The Borg equation for a cement clinker is represented as follows:
C ₃ S content = (4.07 × CaO) - ( 7.60 × SiO 2) - (6.72 × Al 2 O 3) - (1.43 × Fe 2 O 3)
C ₂ S content = (2.87 × SiO ₂ ) − (0.754 × C ₃ S)
C ₃ A amount = (2.65 × Al ₂ O ₃ ) − (1.69 × Fe ₂ O ₃ )
C ₄ AF amount = 3.04 × Fe ₂ O ₃

In the formula, “CaO”, “SiO ₂ ”, “Al ₂ O ₃ ” and “Fe ₂ O ₃ ” are the entire cement clinker of CaO, SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ in cement clinker, respectively. It is a content rate (mass%) with respect to mass. The content ratio of these can be measured by JIS R 5202 (2010) “Chemical analysis method of portland cement”.

The environmental load reduction clinker has a C ₃ A amount of 15% by mass or more calculated by the Borg equation. If the amount of C ₃ A is less than 15% by mass, the strength expression of the cement composition becomes insufficient and the firing temperature in the process of producing the environmental load reducing clinker can not be sufficiently lowered. The amount of C ₃ A of the environmental load reducing clinker is preferably 15 to 40% by mass, more preferably 16 to 40% by mass, still more preferably 20 to 35% by mass, particularly preferably 21 to 35% by mass %. When the amount of C ₃ A of the environmental load reducing clinker exceeds 40% by mass, the fluidity of the slurry obtained by adding water to the ground improvement material containing the environmental load reducing clinker tends to deteriorate.

The environmental load reduction clinker has a C ₄ AF amount of 0.5 to 10% by mass calculated by the Borg equation. If the amount of C ₄ AF is less than 0.5% by mass, the firing temperature in the production process of the environmental load reduction clinker can not be lowered sufficiently. On the other hand, when the amount of C ₄ AF exceeds 10% by mass, the strength development of the ground improvement material is lowered, and the content of heavy metals such as hexavalent chromium specified in the environmental standard is increased. The amount of C ₄ AF is preferably 1 to 8.5% by mass, more preferably 3 to 8% by mass, still more preferably 5 to 7.5% by mass, particularly preferably 6 to 7.5 It is mass%.

The total amount of the C ₃ A amount and the C ₄ AF amount of the environmental load reduction clinker is preferably 21 to 35% by mass. If the total amount is less than 21% by mass, the amount of clay substitute waste used as a cement clinker raw material decreases, and the contribution to a resource recycling society decreases. On the other hand, if the total amount exceeds 35% by mass, the strength development and fluidity of the ground improvement material decrease, and the amount of melt of the environmental load reduction clinker increases, and stable manufacture can be performed using a common rotary kiln. It becomes difficult. The total amount of the C ₃ A amount and the C ₄ AF amount is more preferably 24 to 32% by mass, and still more preferably 27 to 30% by mass.

The amount of C ₂ S in the environmental load reduction clinker is preferably 10 to 50% by mass, more preferably 11 to 45% by mass, and still more preferably 15 to 40% by mass. If the C ₂ S content is less than 10% by mass, long-term strength development tends to be insufficient, while if it exceeds 50% by mass, the short-term strength may decrease. The amount of C ₃ S is preferably 20 to 70% by mass, more preferably 30 to 60% by mass, and still more preferably 35 to 60% by mass. When the C ₃ S content is less than 20% by mass, the medium- and long-term strength development tends to be insufficient, while when it exceeds 70% by mass, the contraction accompanying the increase of the calorific value becomes large and the strength development is insufficient Not only that, but the amount of interstitial phase is not sufficient, the firing temperature may be increased.

The free lime content (f. CaO content) in the cement clinker is preferably as small as possible (for example, 1% by mass or less) from the viewpoint of strength development. However, when the environmental load reducing clinker is used for preparation of the ground improvement material, the environmental load reducing clinker may contain a large amount of free lime as compared with the case of using it for preparation of portland cement. The upper limit value of the free lime content of the environmental load reduction clinker is preferably 8.0% by mass, more preferably 6.0% by mass, still more preferably 5.0% by mass, and particularly preferably 4. It is 5% by mass. On the other hand, the lower limit value of the free lime content of the environmental load reduction clinker is preferably 0% by mass, more preferably 1.0% by mass, and still more preferably 3.0% by mass. If the free lime content of the environmental load reduction clinker is 8.0 mass% or less, when using the environmental load reduction clinker as a ground improvement material, strength expression of equal to or higher than that of the conventional product can be secured, and its manufacturing process Can be fired at a sufficiently low temperature to reduce the amount of CO ₂ generated.

  The content of molybdenum in the environmental impact reducing clinker is preferably as low as possible, for example, preferably 30 mg / kg or less. When the molybdenum content exceeds 30 mg / kg, there is a possibility that the elution amount of molybdenum from the solidified soil may increase depending on the solidification treatment conditions when the environmental load reduction clinker is used as a ground improvement material. If the molybdenum content in the environmental load reduction clinker is, for example, less than 5 mg / kg, the amount of the waste and industrial by-products prepared as cement clinker raw materials decreases, and the production cost of the environmental load reduction clinker rises. The molybdenum content in the environmental impact reduction clinker is preferably 6 to 28 mg / kg, more preferably 12 to 24 mg / kg, from the viewpoint of achieving both sufficiently low production cost and sufficiently low molybdenum elution amount.

  The total chromium content in the environmental load reducing clinker is preferably as low as possible, for example 100 mg / kg or less. Here, the total chromium content refers to the total content of all chromium having different valences such as trivalent chromium and hexavalent chromium contained in the environmental load reduction clinker. If the total chromium content in the environmental load reduction clinker exceeds 100 mg / kg, there is a risk that the amount of elution of hexavalent chromium from the solidified soil may increase depending on the solidification processing conditions when the environmental load reduction clinker is used as a ground improvement agent. is there. If the total chromium content in the environmental load reducing clinker is, for example, less than 30 mg / kg, the compounding amount of waste and industrial by-products as a cement clinker raw material decreases, and the manufacturing cost of the environmental load reducing clinker increases. The total chromium content in the environmental load reduction clinker is preferably 40 to 65 mg / kg, more preferably 43 to 62 mg / kg, from the viewpoint of achieving both sufficiently low production cost and sufficiently low hexavalent chromium elution amount .

  The hexavalent chromium content in the environmental load reducing clinker is preferably 20 to 45 mg / kg. As with the total chromium content, the hexavalent chromium content is preferably as low as possible, but if the hexavalent chromium content in the environmental impact reducing clinker is less than 20 mg / kg, waste and industrial by-products that can be used for cement clinker raw materials There is a tendency for the volume to decrease and the cost of manufacturing to rise. On the other hand, when the hexavalent chromium content in the environmental load reducing clinker exceeds 45 mg / kg, there is a tendency for the elution amount of hexavalent chromium from the solidified treated soil to increase when the environmental load reducing clinker is used as a ground improvement agent. From the viewpoint of achieving both sufficiently low production cost and sufficiently low hexavalent chromium elution amount, the hexavalent chromium content in the environmental load reduction clinker is preferably 25 to 40 mg / kg, more preferably 30 to 35 mg / kg. is there.

  The lead content in the environmental load reducing clinker is preferably as low as possible, for example, preferably 100 mg / kg or less. If the lead content in the environmental load reduction clinker exceeds 100 mg / kg, there is a risk that the amount of lead elution from the solidified soil may increase depending on the solidification processing conditions when the environmental load reduction clinker is used as a ground improvement material. If the lead content in the environmental load reducing clinker is reduced to, for example, less than 10 mg / kg, the amount of the waste and industrial by-products prepared as cement clinker raw materials decreases, and the manufacturing cost of the environmental load reducing clinker increases. The lead content in the environmental load reduction clinker is preferably 10 to 100 mg / kg, and more preferably 30 to 70 mg / kg, from the viewpoint of achieving both a sufficiently low production cost and a sufficiently low lead elution amount.

As described above, the environmental load reduction clinker has a relatively high iron ratio (IM, Al ₂ O ₃ / Fe ₂ O ₃ ) (3.0 to 10.0) and a C ₃ A content ((2.65 × Al) ₂ O ₃ )-(1.69 x Fe ₂ O ₃ ) is relatively high (15 mass% or more), that is, the amount of Al ₂ O ₃ brought in from the raw fuel is Fe ₂ O _{3 in} the environmental load reduction clinker In particular, C ₃ A (aluminate phase) hydrates rapidly, so water is added to the ground improvement material included in the environmental impact reduction clinker with a large amount of C ₃ A. When preparing the slurry, the flowability of the slurry may be insufficient.In order to ensure sufficient flowability of the slurry, in other words, the hydration activity of C ₃ A contained in the environmental load reduction clinker is appropriately adjusted. To reduce environmental impact, This treatment may be applied to the environmental load reduction clinker or may be performed in the process of producing the ground improvement material (see “grinding process” described later). ).

(plaster)
The proportion by mass of gypsum in the ground improvement material is preferably 5 to 30 parts by mass, more preferably 10 to 25 parts by mass, and still more preferably 15 to 20 parts by mass with respect to 100 parts by mass of cement clinker. If the mass ratio of gypsum in the ground improvement material is less than 5 parts by mass, the strength development of the solidified soil tends to be insufficient. In addition, although there exists a tendency for the strength expression property of solidification treatment soil to improve as the mass ratio of the gypsum in a ground improvement material increases, the addition effect is saturated when it exceeds 30 mass parts.

  The form of gypsum used for the above ground improvement material is not particularly limited, and any of dihydrate salt, hemihydrate salt and anhydrous salt can be used. Specific examples of the gypsum include natural gypsum, by-product gypsum by-produced by flue gas desulfurization treatment, natural anhydrous gypsum, and hydrofluoric anhydride gypsum by-produced in the production process of hydrofluoric acid. When using a ground improvement material by a slurry construction method, it is preferable to reduce the usage-amount of hemihydrate gypsum as much as possible, and to mainly use a dihydrate or an anhydrous salt. For example, the ratio of hemihydrate gypsum to total gypsum contained in the ground improvement material is preferably 40% by mass or less, more preferably 0.1 to 30% by mass, and still more preferably 0.5 to 20% by mass. is there. By setting the ratio of hemihydrate gypsum to 40% by mass or less, when the slurry is prepared by adding water to the ground improvement material, it is possible to suppress that the slurry is strengthened.

The amount of SO ₃ in the above ground improvement material is preferably 1.5 to 15.0 parts by mass, more preferably 1.8 to 14.5 mass with respect to 100 parts by mass of the ground improvement material from the viewpoint of strength development. Part, more preferably 3 to 14.0 parts by mass, particularly preferably 8 to 13.0% by mass. The amount of gypsum may be adjusted so that the amount of SO _{3 of the} ground improvement material falls within the above range.

(Inorganic powder)
The inorganic powder contains calcium aluminate hydrate and calcium silicate hydrate. The addition amount of the inorganic powder is preferably 0.1 to 5.0% by mass of calcium aluminate hydrate and calcium silicate hydrate, respectively, more preferably to the total amount of the cement clinker and gypsum. It is preferable to add so as to be contained 0.1 to 3.0% by mass, more preferably 0.1 to 2.0% by mass. When the ground improvement material contains blast furnace slag, the amount of the inorganic powder added is calcium aluminate hydrate and calcium silicate hydrate relative to the total amount of cement clinker, gypsum and blast furnace slag. It is preferable to be added so as to contain 0.1 to 5.0% by mass, more preferably 0.1 to 3.0% by mass, and still more preferably 0.1 to 2.0% by mass. Within such a range, the strength development of the ground improvement material is improved. The proportion by mass of the inorganic powder in the ground improvement material is preferably 0.1 to 5.0 parts by mass, more preferably 0.1 to 4.0 parts by mass with respect to 100 parts by mass of cement clinker. Preferably, it is 0.1 to 3.0 parts by mass. When the proportion by mass of the inorganic powder in the ground improvement material is less than 0.1 parts by mass, the blending effect of the inorganic powder is likely to be insufficient, and when it exceeds 5.0 parts by mass, the long-term strength expression is likely to decrease. Become.

  The inorganic powder preferably contains ettringite as calcium aluminate hydrate. The amount of ettringite in the inorganic powder is desirably 10% by mass or more as a quantitative value by Rietveld analysis of a powder X-ray diffraction pattern using a Cu-k alpha ray. More preferably, it is 20% by mass or more, still more preferably 30 to 70% by mass, and particularly preferably 40 to 60% by mass.

  As the inorganic powder, commercially available or naturally occurring calcium aluminate hydrate and / or calcium silicate hydrate, ground matter of mortar and / or concrete, liquid phase method, hydrothermal synthesis method, ball mill, etc. Hydrates synthesized by the used mechanochemical method can be used. In addition, hydrates produced using EP dust and / or chlorine bypass dust generated in the cement production process can be used.

  As the calcium aluminate hydrate, commercially available or naturally occurring calcium aluminate hydrate and a ground product thereof, and hydrate produced using EP dust and / or chlorine bypass dust generated in the cement production process as raw materials And the crushed material can be utilized. Furthermore, it is desirable that the calcium aluminate hydrate contains 50% by mass or more, preferably 65% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more of ettringite. Moreover, the calcium aluminate hydrate may be used in various forms such as solid, granular, powder, and a slurry obtained by mixing these with a liquid.

  As the calcium silicate hydrate, commercially available or naturally occurring calcium silicate hydrate and a ground product thereof, and hydrate produced using EP dust and / or chlorine bypass dust generated in the cement production process as a raw material And the ground material, the ground material of mortar, and / or the ground material of concrete, etc. can be utilized. Further, calcium silicate hydrate synthesized by a liquid phase synthesis method, a hydrothermal synthesis method, a mechanochemical method using a ball mill, or the like can be used. As a raw material for synthesizing calcium silicate hydrate by the above method, a Ca source such as Ca hydroxide and an Si source such as ethyl silicate or silica may be used, and the amounts of the Ca source and the Si source are adjusted Then, adjust the C / S (= CaO [mol] / SiO2 [mol]) ratio of calcium silicate hydrate. 0.5-5.0 are preferable, as for C / S ratio of a calcium silicate hydrate, 2.0-4.0 are more preferable, and 2.0-3.0 are especially preferable.

  The inorganic powder may be in the form of a slurry previously mixed with a liquid (such as water). For example, when using the ground improvement material as a slurry in deep layer mixing treatment method and using it, the ground improvement material excluding a part or all of the inorganic powder and the slurry containing a part or all of the inorganic powder You may mix and use.

(Brusher slag)
The ground improvement material preferably further includes a suitable amount of blast furnace slag. As a specific example of blast furnace slag, blast furnace granulated slag, blast furnace slowly cooled slag, etc. are mentioned. The content of blast furnace slag in the ground improvement material is preferably 5 to 80 parts by mass, more preferably 10 to 70 parts by mass, and still more preferably 20 to 50 parts by mass with respect to 100 parts by mass of the ground improvement material. is there. If the proportion by mass of blast furnace slag in the ground improvement material is less than 5 parts by mass, effective utilization of industrial by-products (blast furnace slag) tends to be insufficient, and when processing volcanic ash clay soil such as Kanto loam, depending on the solidification treatment conditions The reduction effect of the elution amount of heavy metals such as chromium tends to be insufficient. On the other hand, if the proportion by mass of blast furnace slag in the ground improvement material exceeds 80 parts by mass, the strength of the solidified soil tends to be insufficient.

<Method of manufacturing ground improvement material>
The manufacturing method of the said ground improvement material is demonstrated. This manufacturing method includes a raw material preparation step, a firing step, and a grinding step in this order. A cement clinker is manufactured through the raw material preparation process and the baking process, and a ground improvement material is manufactured through the subsequent crushing process. Here, although the case where an environmental load reduction clinker is manufactured and used as a cement clinker is exemplified, for example, various purchased Portland cement may be used instead.

(Raw material blending process)
In the raw material preparation step, the various ratios (hydraulic ratio, silicic acid ratio and iron ratio) are in the above range, and the amounts of constituent compounds (C ₃ A and C ₄ AF amounts) calculated by the Borg equation are in the above range It is a process of preparing raw materials so that environmental load reduction clinker can be obtained. That is, in this step, the raw materials are selected and the amount used (raw material basic unit) is adjusted so as to obtain an environmental load reduction clinker having desired physical properties (various proportions and amounts of constituent compounds).

  Limestone, silica stone, clay waste etc. are mainly used as raw materials for environmental impact reduction clinker. Clay-based wastes include coal ash, construction soil, slag and the like. Here, the amount of iron raw materials such as copper carami and iron concentrate used in ordinary Portland cement clinker is minimized. By reducing the amount of use of the iron material as much as possible, it is possible to sufficiently suppress that heavy metals contained in the iron material are carried into the environmental load reduction clinker.

It is preferable that the raw material unit per ton of environmental load reduction clinker be in the following range.
Limestone: 800-1300 kg, more preferably 900-1200 kg, still more preferably 1000-1150 kg.
Silicate: 0 to 100 kg, more preferably 0 to 50 kg, still more preferably 0 to 20 kg.
Clay-based waste: 250 to 600 kg, more preferably 300 to 500 kg, still more preferably 350 to 450 kg.
Iron raw material: 0 to 30 kg, preferably 0 to 20 kg, more preferably 0 to 10 kg, particularly preferably 0 kg.

The amount of Al ₂ O _{3 in the} clay-based waste (including clay-based industrial by-products) is preferably 10% by mass or more, more preferably 10 to 70% by mass, and still more preferably 20 to 65% by mass. And particularly preferably 25 to 60% by mass. The SiO ₂ / Al ₂ O ₃ mass ratio of the clay-based waste is preferably 5.0 or less, more preferably 1.0 to 4.0, and still more preferably 2.0 to 3.0. . Specific examples of such clay-based waste include coal ash (eg, fly ash, bottom ash) and the like. In addition, it is preferable to select and use coal ash etc. which contain 3 mass% or more (more preferably 4 to 6 mass%) of Fe ₂ O ₃ as the clay-based waste, and even if it does not use an iron raw material by this The granulation of the environmental load reduction clinker can be facilitated, and the powderization of the environmental load reduction clinker can be suppressed. As a result, the heat exchange efficiency in the cooler and the dust collection efficiency can be enhanced, so that the environmental load reduction clinker can be manufactured more stably and with less energy.

The amount of Fe ₂ O ₃ of the iron raw material is preferably 30% by mass or more, more preferably 30 to 90% by mass, still more preferably 40 to 80% by mass, and particularly preferably 50 to 70% by mass. is there. Specific examples of such iron raw materials include copper carami, iron concentrate, converter kiln and the like.

(Firing process)
A baking process is a process of obtaining an environmental impact reduction clinker by baking the raw material obtained by passing through a raw material preparation process. Examples of equipment for carrying out this process include NSP kiln, SP kiln and the like. These facilities include a burn-point temperature measuring device for measuring a firing temperature, and f. It is preferable to have a CaO amount measuring machine (or f. CaO amount analyzer).

The calcination temperature is preferably 1200 to 1450 ° C., more preferably 1250 to 1400 ° C., still more preferably 1300 to 1400 ° C., particularly preferably 1350 to 1400 ° C. If the firing temperature is less than 1200 ° C., the strength improvement of the ground improvement material tends to be insufficient, while if it exceeds 1450 ° C., the CO ₂ emission reduction effect in the firing step tends to be insufficient. The fired environmental load reduction clinker is collected every 1 to 12 hours, and f. It is preferable to measure the amount of CaO. f. The amount of CaO may be monitored, and the firing conditions (temperature, time (rotational speed in the case of a rotary kiln), etc.) may be adjusted so that the value satisfies a predetermined condition (for example, less than 8.0% by mass).

(Crushing process)
The grinding step is a step of obtaining a ground improvement material by grinding a mixture containing an environmental load reduction clinker, gypsum, an inorganic powder, and optionally blast furnace slag. As equipment for carrying out this process, a ball mill, vertical roller mill and the like can be mentioned. When adding gypsum to cement clinker, blast furnace slag or coal ash may be added.

The brane specific surface area of the ground improvement material obtained through the grinding step is preferably 3000 to 5000 cm ² / kg, more preferably 3500 to 5000 cm ² / kg, from the viewpoint of the appropriate reactivity of the ground improvement material. More preferably, it is 4000 to 5000 cm ² / kg.

  From the viewpoint of sufficiently securing the flowability of the slurry prepared using the ground improvement material, a treatment for suppressing the reactivity of the ground improvement material may be carried out in the grinding step. For example, the ground improvement material may be weathered by adding a predetermined grinding aid (organic grinding aid and / or water) to the environmental load reduction clinker in the grinding step and grinding. Examples of organic grinding aids include diethylene glycol and triethanolamine. As a grinding aid, an organic grinding aid and water may be used alone or in combination. In the pulverizing step, the use of a pulverization aid also has the effect of being able to suppress the temperature at pulverization to a predetermined temperature or less (for example, 120 ° C. or less). The ground improvement material may be weathered by aging the ground improvement material in the silo instead of or together with the weathering treatment in the grinding process.

  In the mixture to be ground, the content of the organic grinding aid is preferably 0 to 1.0 parts by mass, more preferably 0. to 1.0 parts by mass with respect to 100 parts by mass of the total of environmental load reduction clinker, gypsum and blast furnace slag. It is 0.001 to 0.1 parts by mass, and more preferably 0.01 to 0.05 parts by mass. If the content (addition amount) of the organic grinding aid exceeds 1.0 part by mass, the strength developing property of the cement composition may be lowered.

  In the mixture to be ground, the content of water is preferably 0.5 to 5.0 parts by mass, more preferably 0.3 to 5.0 parts by mass with respect to 100 parts by mass in total of environmental load reduction clinker, gypsum and blast furnace slag. It is 3.0 parts by mass, more preferably 0.5 to 2.0 parts by mass. If the water content (addition amount) is less than 0.5 parts by mass, there is a risk that the slurry fluidity and strength development of the cement composition may be reduced. The slurry fluidity and strength development of the composition may be reduced.

The degree of weathering of the ground improvement material can be determined by measuring the water vapor adsorption amount of the ground improvement material. More specifically, the ground improvement material of this embodiment has a water vapor adsorption amount at a relative pressure of 0.9265 in the adsorption process of 4.9 g or less (more preferably 0.1 to 4) per 100 g of the ground improvement material. The difference (hysteresis) of the water vapor adsorption amount between the adsorption isotherm and the desorption isotherm at a relative pressure of 0.1000 is not more than 1.9 g (more preferably 0.1 to 0.1 g) per 100 g of the ground improvement material. It is preferable that it is 1.9 g). Here, the water vapor adsorption amount at a relative pressure of 0.9265 reflects the content (C ₃ A amount and f. CaO amount) of the component highly reactive with water in the ground improving material. On the other hand, the difference (hysteresis) of the water vapor adsorption amount between the adsorption isotherm and the desorption isotherm at a relative pressure of 0.1000 reflects the hydration activity of the ground improvement material before water vapor adsorption. That is, by intentionally weathering the ground improvement material such that these two values satisfy the above condition, the flowability of the slurry containing the ground improvement material can be sufficiently secured.

It is preferable that the manufacturing method of this embodiment further include the process of measuring the water vapor adsorption amount of a ground improvement material after a grinding process. By carrying out this step, it is possible to grasp whether the degree of weathering of the manufactured cement composition is in an appropriate range from the viewpoint of reactivity, and to obtain useful information for product management. it can. The amount of water vapor adsorption can be measured by degassing the ground improvement material at 40 ° C (under vacuum) for 12 hours with a high-precision fully automatic gas adsorption device (BELSORP 18 manufactured by Nippon Bell Co., Ltd.) and performing a water vapor adsorption test at 25 ° C Good. Thereby, the hysteresis (difference) of the water vapor adsorption amount at the relative pressure of 0.9265 and the water vapor adsorption amount of the adsorption isotherm at the relative pressure of 0.1000 and the desorption isotherm can be obtained. In addition, what is necessary is just to use the following formula | equation for conversion from the volume to the mass of the amount of water vapor adsorbed to the ground improvement material.
B = C / (22.7 × 1000) × 18 × 100
B: Water vapor adsorption amount per 100g of ground improvement material (g / 100g)
C: Water vapor adsorption amount per 1 g of ground improvement material (cm ³ (STP) / g)

  It is preferable that the manufacturing method of this embodiment further include the process of measuring the ratio (hemihydrate gypsum conversion ratio) in the gypsum used for manufacture of a ground improvement material. By using a gypsum having a hemihydrate gypsum conversion rate of 40% by mass or less, when preparing a slurry by adding water to the ground improvement material, it is possible to suppress the occurrence of firmness in the slurry. The measurement of the hemihydrate gypsum conversion rate is carried out by quantitative determination of dihydrate gypsum and hemihydrate gypsum by powder X-ray diffraction measurement, or by measurement of dehydration temperature and dehydration amount by thermogravimetric measurement / differential thermal analysis (TG-DTA) device. be able to.

<Ground improvement method>
The ground improvement method of the present embodiment includes the step of mixing the above ground improvement material and the soil. Target soils include loam, clay, sandy soil, organic soil and the like. The ground improvement method of the present embodiment has sufficient strength development even for loam and organic soils which have been difficult to secure sufficient solidity strength with conventional ground improvement materials. The amount of the ground improving material mixed to 1 m ³ of soil is preferably 30 to 500 kg, more preferably 50 to 450 kg, and still more preferably 200 to 400 kg, from the viewpoint of sufficiently enhancing the solidification strength of the soil. The mixing method of the soil and the ground improvement material can be added to the soil as powder and mixed, or the water can be mixed and mixed in the soil as a slurry, like the conventional ground improvement material.

The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

  Hereinafter, the contents of the present invention will be more specifically described with reference to examples and comparative examples. The present invention is not limited to the following examples.

[1. Production of Environmental Load Reduction Clinker]
The raw materials in Table 1 were used to produce the environmental load reduction clinker.

Dihydrate gypsum: Wako Pure Chemical Industries, Ltd., reagent special grade, purity 98.0%
Sodium carbonate (Na2CO3): Wako Pure Chemical Industries, Ltd., reagent special grade, purity 99.8%
Potassium carbonate (K2CO3): Wako Pure Chemical Industries, Ltd., reagent special grade, purity 99.5%

  The above-mentioned raw materials were prepared in the proportions of Table 2, and cement clinkers were fired respectively while changing the maximum firing temperature. The firing method in the electric furnace is as follows: The clinker raw material is put into the electric furnace held at 1000 ° C., the temperature is raised at 10 ° C./min to the maximum baking temperature, and the sample is held for 30 minutes at the maximum temperature Air cooled. About the cement clinker obtained by baking, the chemical component was measured according to JISR5202: 2010 "the chemical analysis method of a cement", and the ratio and mineral composition of the clinker were computed by the following formula | equation. In addition, the mineral composition as well as f. The amount of CaO was measured. The chemical composition, ratios and mineral composition of the obtained clinker are shown in Tables 3 to 5.

HM = CaO / (SiO ₂ + Al ₂ O ₃ + Fe ₂ O ₃ )
SM = SiO ₂ / (Al ₂ O ₃ + Fe ₂ O ₃ )
IM = Al ₂ O ₃ / Fe ₂ O ₃
C ₃ S = 4.07 × CaO-7.60 × SiO ₂ −6.72 × Al ₂ O ₃ −1.43 ×
Fe ₂ O ₃
C ₂ S = 2.87 × SiO ₂ −0.75 × C ₃ S
C ₃ A = 2.65 × Al ₂ O ₃ −1.69 × Fe ₂ O ₃
C ₄ AF = 3.04 × Fe ₂ O ₃

  As shown in Table 2 and Table 3, the environmental load reducing clinker K3, K4, K7 is at the same temperature or lower temperature as the general ordinary Portland cement clinker (K1) or early strong Portland cement clinker (K2, K5) F. It can be seen that the amount of CaO is sufficiently suppressed, and the ease of firing is improved. Furthermore, the Mo content in the clinker is 30 mg / kg or less, the total Cr content is 100 mg / kg or less, and the Pb content is 100 mg / kg or less. In addition, in the environmental load reducing clinkers K3, K4, K5, and K7, it is possible to use coal ash of 250 kg / t-cl 'or more, which is larger than K1, K2, and K6.

[2. Production of ground improvement materials]
The ground improvement materials are selected from gypsum, blast furnace slag, calcium aluminate hydrate powder, calcium silicate hydrate, using cement clinker (K1, K3, K4, K7) in Tables 3 to 5 The materials were added, and ground improvement materials were obtained with the formulations of Table 6 and Table 7. For grinding, a ball mill was used, and diethylene glycol (DEG) as an organic grinding aid was added by 0.04% by mass based on the total amount of cement clinker, gypsum, and blast furnace slag, and ground. The degree of fineness of the ground improvement material was set to 4500 ± 50 cm ² / g as the specific surface area of branes.

Blast furnace slag: Granulated blast furnace granulated slag fine powder, SO ₃ content: 0.1%, sulfide sulfur content: 0.861%, bran specific surface area: 3460 cm ² / g, Chiba Rebarment Co., Ltd. gypsum: hydrofluoric acid Anhydrite, SO ₃ content: 58.1%, Blaine specific surface area: 3700 cm ² / g, manufactured by Central Glass Co., Ltd.

    FIG. 1 is an X-ray diffraction pattern of calcium aluminate hydrate powder used in Examples. According to the Rietveld analysis result of the obtained X-ray diffraction pattern, the calcium aluminate hydrate powder contained 99% by mass of ettringite (3CaO · Al2O3.3 · CaSO4 · 32H2O). From the chemical composition, the remaining 1% by mass was estimated to be aluminum hydroxide.

Elemental analysis of calcium silicate hydrate used in this example was performed using an electron microscope TM3030 (manufactured by Hitachi High-Technologies) and an energy dispersive X-ray analyzer SwiftED 3000 (manufactured by Oxford Instruments, UK). . As a result of measuring elemental analysis mapping four times, the minimum value of the C / S ratio of calcium silicate hydrate was 2.08, the maximum value was 2.81, and the average value was 2.34.

[3. Preparation of solidified treated soil using ground improvement material]
The target soil is loam (natural water content: 132.6%, wet density: 1.361 g / cm ³ , moisture content: 0.1%, sand content: 11.0%, fine particle content: 88.9%) After adding 300 kg / m ^{3 of} ground improvement agent to the soil and mixing well with a Hobart mixer, it was packed in a cylindrical form, and a solidified treated soil sample was prepared.

[4. Strength test of solidified soil]
After curing for 7 days and 28 days at 20 ° C, the solidified soil is measured for penetration input when the penetration amount of the needle is 10 mm with a needle penetration tester (SH-70, manufactured by Maruto Seisakusho), penetration gradient Was calculated. Furthermore, the strength of the solidified soil was calculated from the penetration gradient. The following equation was used to calculate the strength of the solidified soil.

A = 94.248 ^{x 1.2567}
A: Solidification strength (N / mm ² )
X: needle penetration gradient (N / mm) = penetration input (N) / penetration amount (mm)

[5. Test results]
・ In the case of no slag composition (Table 8)
In the ground improvers of Comparative Examples 2, 4, 6 and 8 which contain only calcium silicate hydrate in the inorganic powder and do not satisfy the requirements of the present invention, the solidification strength is higher than in the case where the inorganic powder is not contained. It is improved by 10 to 50% at 7 days old and 5 to 99% at 28 days old. On the other hand, in the ground improvement materials of Examples 1 to 4 which contain calcium aluminate hydrate powder and calcium silicate hydrate as inorganic powders and satisfy the requirements of the present invention, compared with the case where inorganic powders are not included. An improvement in solidification strength is observed as much as 13 to 168% at 7-day age and 41 to 153% at 28-day age. In particular, with the ground improvement material using the environmental load reduced clinker of Examples 2 and 4, excellent solidification strength (solidification strength of 1000 N / mm ² or more at 28-day age) can be obtained. Moreover, the ground improvement materials of Examples 1 to 4 each have a solidification strength equal to or higher than the ground improvement material using ordinary portland cement shown in Comparative Example 1.

・ In the case of blast furnace slag containing composition (Table 9)
The ground improvers of Comparative Examples 10, 12, 14 and 16 which contain only calcium silicate hydrate in the inorganic powder and do not contain the calcium aluminate hydrate powder are compared with the case where the inorganic powder is not contained. Solidification strength is improved by 4 to 46% at 7 days and up to 65% at 28 days. On the other hand, the ground improvers of Examples 5 to 8 which contain calcium aluminate hydrate powder and calcium silicate hydrate as inorganic powders and satisfy the requirements of the present invention are compared to the case where inorganic powders are not included. An improvement in solidification strength of 20 to 66% at 7 days of age and up to 40% at 28 days of age is observed, and is particularly effective for improving the strength at short age.

Claims (9)

Cement clinker,
With plaster
It is a ground improvement material containing inorganic powder and
See containing said inorganic powder is hydrated calcium aluminate, a calcium silicate hydrate,
The calcium aluminate hydrate comprises ettringite,
Furthermore, the content of the calcium aluminate hydrate is 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the total amount of cement clinker and gypsum,
A ground improvement material characterized in that the content of the calcium silicate hydrate is 0.1 to 5.0 parts by mass with respect to 100 parts by mass of a total amount of cement clinker and gypsum . Cement clinker,
With plaster
It is a ground improvement material containing inorganic powder and
The inorganic powder comprises calcium aluminate hydrate and calcium silicate hydrate,
The cement clinker is
Hydraulic modulus (HM) is 1.75 to 2.20, silicic acid ratio (SM) is 1.50 or more and less than 2.50, iron ratio (IM) is 3.0 to 10.0, and it is Borg type C calculated ₃ A content is 15% by mass or more, C ₄ The ground improvement material characterized by AF amount being 0.5-10 mass%. Cement clinker,
With plaster
It is a ground improvement material containing inorganic powder and
Further contains blast furnace slag,
The inorganic powder comprises calcium aluminate hydrate and calcium silicate hydrate,
The calcium aluminate hydrate comprises ettringite,
Furthermore, the content of the calcium aluminate hydrate is 0.1 to 5.0 parts by mass with respect to 100 parts by mass in total of cement clinker, gypsum and blast furnace slag,
A ground improvement material characterized in that the content of the calcium silicate hydrate is 0.1 to 5.0 parts by mass with respect to a total amount of 100 parts by mass of cement clinker, gypsum and blast furnace slag. Cement clinker,
With plaster
It is a ground improvement material containing inorganic powder and
Further contains blast furnace slag,
The inorganic powder comprises calcium aluminate hydrate and calcium silicate hydrate,
The cement clinker is
Hydraulic modulus (HM) is 1.75 to 2.20, silicic acid ratio (SM) is 1.50 or more and less than 2.50, iron ratio (IM) is 3.0 to 10.0, and it is Borg type C calculated ₃ A content is 15% by mass or more, C ₄ The ground improvement material characterized by AF amount being 0.5-10 mass%. The content of the blast furnace slag to the equivalents該地Release modifying material 100 parts by weight is 5 to 80 parts by weight,
Soil improvement material according to claim 3 or 4 SO ₃ weight with respect to the soil improvement material 100 parts by weight characterized in that it is a 1.5 to 15.0 parts by weight. The content of ettringite in the inorganic powder is 10% by mass or more in quantitative value by Rietveld analysis of powder X-ray diffraction pattern,
And the Ca / Si ratio of the calcium silicate hydrate contained in the said inorganic type powder is 0.5-5.0, The ground improvement material of any one of the Claims 1-5 characterized by the above-mentioned. . The ground improvement material according to any one of claims 1 to 6 , wherein a free lime (f. CaO) content of the cement clinker is less than 8.0% by mass. The inorganic powder is
The ground improvement material according to any one of claims 1 to 7, which is an inorganic powder produced by using EP dust and / or chlorine bypass dust generated in the cement production process as a raw material. The ground improvement method using the ground improvement material of any one of Claims 1-8.