JP2009051910A - Gypsum-based solidification material and additive for gypsum-based solidification material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solidification material for reusing construction sludge generated from cast-in-place pile work, shield tunneling work or the like, surplus soil generated in construction such as digging surplus soil, or dredge soil of bottom mud in streams, lakes and sea area by solidifying them in a neutral zone so as to be able to be carried out, as a subsoil material, and to provide an additive for gypsum-based solidification material. <P>SOLUTION: The solidification material is obtained by adding an aluminum compound and a calcium compound to hemihydrate gypsum. The solidification material obtained by adding the hemihydrate gypsum in the excessive amount than the formed amount of ettringite is obtained by adding the excessive amount of the hemihydrate gypsum than the formed amount of the ettringite to an ettringite precursor material of the compound thereof. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  This invention solidifies and discharges construction waste mud generated from cast-in-place pile construction and shield construction, construction generated residual soil such as excavation residual soil, or bottom mud dredged soil in rivers, lakes, and seas in a neutral region. The present invention relates to an additive to a solidifying material and a gypsum-based solidifying material that can be reused as a ground material.

  As is well known, construction sludge and dredged soil have a high water content and cannot be used as a ground material. In addition, general excavation residual soil is softened by disturbance and often cannot be reused.

  When these soft materials are used as the ground material, compaction and drainage have been performed in the past, but depending on the construction method, noise may be generated and the construction period may be long, so that sufficient effects may not be exhibited. Therefore, a method of adding and mixing ground improvement materials such as cement and lime and solidifying is widely adopted.

  When sludge and construction residual soil are improved, quick lime, cement-based solidified material, and polymer water-absorbing agent and semi-water gypsum are used alone or in combination when neutrality is required (see Patent Document 1).

JP 2003-155482 A

  However, cement, cement-based solidified material, or quicklime, which is widely used for soil solidification, has been widely used in recent years because it can be solidified and improved at a low cost and with high strength in a short construction period. In the cement-based solidified material, a part of CaO occupying about 60% thereof precipitates as slaked lime, and exhibits alkalinity of pH 12 or higher. Quicklime has similar problems. Even solidified soil mixed with soil has a pH of about 10 to 11.

  For this reason, the improved soil with cement lime has the problem that it cannot be planted directly. According to the Ministry of Health, Labor and Welfare's “Law Concerning Hydrogen Ion Concentration of Improved Soil (Emission Standard)”, the pH of improved soil is 5.8 to 8.6 outside the sea area and 5.0 to 9.0 in the sea area.

  In addition, polymeric water-absorbing agents have been developed and used as a method for improving construction soil in the neutral range. However, this is intended to improve handling by reducing the apparent water content by absorbing a large amount of soil moisture, and since it does not harden itself, re-mudging at the destination is a problem. is there.

  In addition, some natural products such as guar gum rot due to long-term storage and have odor problems.

  Therefore, a solidified material using a hydration reaction of gypsum plaster is known. This utilizes the reaction which hardens as a two-water gypsum by adding water to a half-water gypsum. Gypsum is a neutral compound, and it is known that treated soil becomes neutral.

  However, when the soil contains a large amount of moisture as in the soil generated from construction, it is difficult to develop the strength. Therefore, a large amount of gypsum must be used, resulting in an increase in the amount of discharged residual soil and an increase in cost. It has been pointed out that there is a problem.

  Moreover, although using together the said gypsum and a polymeric water absorbing agent is also implemented, it is not solved about the re-mudging in a delivery destination, but there also exists a problem also in cost.

  The present invention was devised in view of the current situation, and the object thereof is a solidified material in which the solidified soil is in a neutral region, and a solidified material capable of expressing a predetermined strength with a small addition amount. Is to provide.

  In order to achieve the above object, the solidifying material according to claim 1 is a solidified material obtained by adding an aluminum compound and a calcium compound to semi-water gypsum, and adding semi-water gypsum in excess of the amount of ettringite produced. Features. In other words, the ettringite precursor which is these compounds is characterized by adding semi-water gypsum in excess of the amount of ettringite produced.

  The solidified material of claim 2 is based on the technical premise of the solidified material of claim 1 and uses aluminum hydroxide, aluminum oxide, aluminum sulfate as the aluminum compound, and calcium oxide or calcium hydroxide as the calcium compound. It is characterized by.

  The invention according to claim 3 is based on a technical premise of the solidified material according to claim 1 or claim 2, and calcium aluminate, calcium sulfoaluminate, calcium fluoroaluminate, calcium as the ettringite precursor. Chloraluminate, alinite, Na2O.8CaO.3Al2O3, and alums are used alone or in combination, and gypsum is added in excess of the amount of ettringite produced.

  The invention according to claim 4 is based on the technical premise of the solidified material according to any one of claims 1 to 3, wherein 53.7 to 99% by weight of the semi-aqueous gypsum and 0.4% of aluminum hydroxide powder. ˜20.6 wt%, quick lime or slaked lime 0.3 to 22.1 wt%.

  The invention according to claim 5 is based on the technical premise of the solidified material according to claim 2 or claim 4, wherein the aluminum hydroxide is produced by a dried aluminum sludge, and the dried aluminum sludge is It is characterized in that it is a powder obtained by neutralizing, washing, dehydrating and drying a waste cleaning liquid generated in alumite treatment in which metallic aluminum is washed with caustic soda, water and sulfuric acid to form an oxide film.

  The invention according to claim 6 is based on the technical premise of the solidified material according to claim 1 or claim 2, and the molar ratio of calcium atoms and aluminum atoms of the calcium compound and aluminum compound added to the semi-aqueous gypsum is determined. By excluding calcium atoms contained in gypsum, by making Ca / Al 1.5 or less, dihydrate gypsum and a small amount of ettringite are produced as hydrated products, and some aluminum compounds are unreacted. It is characterized by remaining in a state.

  That is, even if the CaO / Al2O3 molar ratio of the aluminum compound and calcium compound is made smaller than 3, or the CaO / AL (OH) 3 molar ratio is made smaller than 1.5, and this is added to the semi-aqueous gypsum, Can play a function.

  The additive to the gypsum according to claim 7 is characterized in that it is formed of a component excluding the semi-aqueous gypsum from the solidified material according to claims 1 to 6.

  Since the solidified material and the additive to gypsum according to the present invention are configured as described above, the solidified soil is a solidified material in a neutral region, and can exhibit a predetermined strength with a small amount of addition.

  The solidifying material according to the present invention is based on a semi-aqueous gypsum, and an ettringite precursor is added to this within a range where the pH is in a neutral range.

  Next, aluminum sludge, quicklime or slaked lime is added to the half-water gypsum as ettringite precursor.

  Then, an excess of half water gypsum is produced from the amount of ettringite produced to produce as much dihydrate gypsum as neutral hydrate as possible, and a part is used for ettringite production, and the high pH due to ettringite is reduced.

  Since the increase in pH is due to lime, the Ca / Al molar ratio is made smaller than 1, and the pH is lowered and the strength is reduced by making calcium ions too small for ettringite formation (making aluminum sludge excessive for lime). Considered to maintain.

  As a result, a decrease in pH due to excess of the dried aluminum sludge with respect to lime was observed, and the strength was much higher than that of the half-water gypsum alone. Immediately after the kneading, the pH showed a value of around 10 due to the elution of lime, and the lime content was consumed over time to produce ettringite. Therefore, the pH was lowered and a neutral value could be obtained. Moreover, the neutralization effect | action by the small amount of sulfate radical contained in aluminum sludge is also considered.

[Example 1]
(1) Materials used Semi-water gypsum Yoshino gypsum Sakura mark Burned gypsum for teaching materials Quick lime Chichibu lime Powdered quick lime QA POW
Slaked lime Ryoko Lime Aluminum Sludge Dry Product Fuji Sash Ordinary Cement Pacific Cement Made Aluminum Sludge Dry Product A powdered material obtained by drying amorphous alumina gel, mainly composed of amorphous aluminum hydroxide.
{Component analysis}
Item Analysis value (%)
Al2O3 47.5%
SO3 13.0%
SiO2 0.3%
CaO 0.3%
(2) Soil to be solidified Simulated sludge was used by adding water to Silt # 250 (Table 1) manufactured by Marunaka Shirato Co., Ltd. and having a moisture content of 100% and a wet density of 1.385 t / m3. Table 2 shows the results of the solidification test.

As can be seen from Table 2, no. 1 is semi-gypsum simple and neutral, but the strength is low.
No. 2 is close to the ettringite composition, the strength is high, but the pH is 9 or more.
No. 3 produced dihydrate gypsum and a small amount of ettringite as a hydrate. The strength was high, but the pH was 9 or more.
No. Nos. 4 to 6 were blends satisfying claims 4 and 6, almost half-water gypsum, and aluminum sludge dry powder and lime were added at a Ca / Al molar ratio of less than 1.5 for the purpose of producing ettringite. Although the pH immediately after kneading was 9 or more, the pH decreased with time and achieved pH 8.6 or less. About intensity | strength, it became the intensity | strength of about 5 to 10 times as much as half water gypsum.
No. 7.8 is a semi-water gypsum added with 5% cement. 7 has a high strength but a high pH of around 10, far from the neutral range. No. No. 8 was obtained by setting the addition amount of the solidifying material to 1/3 compared to the others, and the pH was also high, and it did not solidify at 9.6 or more.

[Example 2]
Materials used: Same as Example 1.
Target soil: Cohesive soil Water content 46.3%
Wet density 1.66t / m3

  Table 3 shows the results of the solidification test.

As is clear from Table 3, No. 1 is a semi-gypsum simple and neutral, but its solidification strength is low.
No. 2.3 is a composition capable of forming dihydrate gypsum and ettringite as a hydrate. Although the pH immediately after kneading exceeded 8.6, it decreased with time and achieved pH 8.6 or less. The strength was high, and a strength equivalent to 70 kg / m3 in a half-water gypsum was secured at 30 kg / m3.
No. 4 is a semi-water gypsum, and aluminum sludge dry powder and quicklime were added at a Ca / Al molar ratio of less than 1.5 for the purpose of producing ettringite. Immediately after kneading, the pH was below 8.6, and the strength was No. Compared with 2.3, it was not inferior.
No. No. 5 is a blend that produces ettringite as a hydrated product, and the strength is high, but the pH does not drop, and it is 9.5 or higher even after 28 days.

  In Table 3, the strength test and the pH test were performed according to the following procedure.

  The strength test was performed by sealing and curing with a 5 cmφ × 10 cmh mold, and a uniaxial compression test was performed.

  In addition, in the pH test, immediately after kneading or after solidification, the crushed material was added with water and suspended, and the pH of the supernatant was measured.

Claims (7)

  A solidified material obtained by adding an aluminum compound and a calcium compound to semi-water gypsum, and adding semi-water gypsum in excess of the amount of ettringite produced. The aluminum compound is aluminum hydroxide, aluminum oxide, aluminum sulfate,
The solidified material according to claim 1, wherein calcium oxide or calcium hydroxide is used as the calcium compound.   The ettringite precursor is calcium aluminate, calcium sulfoaluminate, calcium fluoroaluminate, calcium chloroaluminate, alinite, Na2O.8CaO.3Al2O3, or alum or any combination thereof, and the amount of ettringite produced. The solidified material according to claim 1 or 2, wherein hemihydrate gypsum is added in excess.   The half water gypsum is 53.7 to 99% by weight, aluminum hydroxide powder 0.4 to 20.6% by weight, quick lime or slaked lime 0.3 to 22.1% by weight. The solidified material according to claim 3.   The aluminum hydroxide is produced from a dried aluminum sludge, and the dried aluminum sludge is washed with caustic soda, water and sulfuric acid to neutralize and wash the cleaning waste liquid generated in the alumite treatment to form an oxide film. The solidified material according to claim 2, wherein the solidified material is a dehydrated and dried powder.   As the hydration product, the molar ratio of calcium atoms and aluminum atoms of the calcium compound and aluminum compound added to the semi-aqueous gypsum is 1.5 or less in Ca / Al, excluding the calcium atoms contained in the gypsum. 3. The solidified material according to claim 1, wherein a dihydrate gypsum and a small amount of ettringite are produced, and a part of the aluminum compound is left unreacted.   The additive to the gypsum of the component remove | excluding the semi-water gypsum from the solidification material of Claim 1 thru | or 6.