Method of hardening soil and hardened soil

Details Method of hardening soil and hardened soil Method of hardening soil and hardened soil

2001-04-16

2003-03-25

Bagnell, David (Department: 3673)

Hydraulic and earth engineering

Earth treatment or control

Chemical

C405S264000, C106S601000

Reexamination Certificate

active

06536995

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a method for hardening soil.
There is a well-known soil-cement method for stabilizing soil in soft ground, where the soil is mixed with cement and a proper quantity of water.
However, when the soil contains 2% or more of organic materials mostly comprising inhibiting organic acids from corroded organism such as humic acid which is insoluble organic acid, the organic materials, which exist on the surfaces of the particles of the soil, draw the water of hydronium ion (H
3
O
+
) so that the soil particles are surrounded by the water. The bonding and solidification of the cement and the particles of soil are accordingly inhibited by the surrounding water, thereby largely deteriorating the hardening of the soil.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for hardening the soil, and soil improved therewith, wherein the inhibition of the bond between the cement and soil due to the inhibiting organic acids such as humic acid included in the soil is restrained, hence solving the above described problem.
The present invention provides a method for hardening soil comprising the steps of mixing cement with soil, and mixing a soil improving agent including eight or more cations selected from Ca
++
, Na
+
, Mg
++
, K
+
, NH
4
+
, Ba
++
, Fe
3+
, Al
3+
, Mn
4+
, Co
++
and Ti
4+
, two or more anions selected from Cl
−
, SO
4
−−
and PO
4
3−
, and organic acid with the soil mixed with cement.
Upon mixing of the cement with the soil, if the soil does not contain sufficient moisture necessary for solidification of the cement, an appropriate quantity of water is added. If the soil contains enough moisture, it is not necessary to use additional water. When the cement mixed with the mixing agent is injected in the earth or added to sludge in marshes, for example, an appropriate quantity of water is added thereto.
The organic acid consists one or more of citric acid, tartaric acid and maleic acid.
In the method, it is preferable to mix 0.32 to 2 kg in solid basis of mixing agent with a soil mixture including 20 to 600 kg of cement per 1 m
3
of soil.
Another method of the present invention is suitable for the soil including a large amount of inhibiting organic acids which is difficult to be hardened by the soil improving agent.
The method comprises mixing at least Ca
++
of bivalent or more cations and an organic acid having a chelate effect with a soil so as to neutralize inhibiting organic acids included in the soil, mixing cement with the mixture of Ca
++
and the organic acid and the soil, and mixing a soil improving agent including eight or more cations selected from Ca
++
, Na
+
, Mg
++
, K
+
, NH
4
+
, Ba
++
, Fe
3+
, Al
3+
, Mn
4+
, Co
++
and Ti
4+
, anions selected from Cl
−
, SO
4
−−
and PO
4
3−
, with the mixed soil.
The quantity of the cation of bivalent or more is determined to a value necessary for neutralizing the hydrogen ion (H
+
) (cation exchange capacity (CEC) value) in the carboxyl group (—COOH).
The present invention further provides an improved soil wherein the soil is mixed with cement, and further mixed with a mixing agent for improving soil including eight or more cations selected from Ca
++
, Na
+
, Mg
++
, K
+
, NH
4
+
, Ba
++
, Fe
3+
, Al
3+
, Mn
4+
, Co
++
and Ti
4+
, two or more anions selected from Cl
−
, SO
4
−−
and PO
4
3−
, and organic acid.
The organic acid comprises one or more of citric acid, tartaric acid and maleic acid.
In the improved soil, 0.32 to 2 kg in solid basis of mixing agent is mixed with a soil mixture including 20 to 600 kg of cement per 1 m
3
of soil.
These and other objects and features of the present invention will become more apparent from the following detailed description.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A mixing agent for hardening soil in accordance with the present invention comprises a pulverized solid mixing agent and a liquid mixing agent.
The solid mixing agent includes one or more of magnesium chloride (MgCl
2
), potassium chloride (KCl), calcium chloride (CaCl
2
), sodium chloride (NaCl),and ammonium chloride (NH
4
Cl), each of 100 to 300 g, and 10 to 20 g of an agent consisting of cobaltous chloride (CoCl
2
), barium oxide (BaO), calcium sulfate (CaSO
4
), calcium phosphate (CaHPO
4
), and manganese dioxide (MnO
2
). The solid mixing agent further includes one or more of organic acids such as 10 to 30 g of citric acid (C
6
H
8
O
7
).
Mineral components extracted from natural vermicurite with sulfuric acid are used as the liquid mixing agent. An example of the composite of the undiluted solution for the liquid mixing agent is set below. Each component of the liquid mixing agent exists in the form of ions or minerals, and the specific gravity thereof is between 1.1 and 1.2, and pH is between 0.3 and 1.0.
Iron (Fe)
22.7
g/l
Aluminum (Al)
9.1
g/l
Magnesium (Mg)
2.7
g/l
Potassium (K)
1.5
g/l
Titanium (Ti)
832
mg/l
Manganese (Mn)
559
mg/l
Phosphor (P)
216
mg/l
Calcium (Ca)
129
mg/l
Sodium (Na)
101
mg/l
Silicon (Si)
55
mg/l
Zinc (Zn)
42
mg/l
Selenium (Se)
32
mg/l
Vanadium (V)
19
mg/l
Copper (Cu)
8.4
mg/l
Germanium (Ge)
8.0
mg/l
Cobalt (Co)
7.0
mg/l
Nickel (Ni)
6.5
mg/l
Molybdenum (Mo)
4.4
mg/l
Lithium (Li)
4.0
mg/l
Free sulfuric acid ion (SO
4
2−
)
25
mg/l
The above described liquid mixing agent is diluted 2000 times so that the sulfuric acid density becomes about 100 ppm so as to be used. The liquid mixing agent, which also serves as a diluent, is mixed with the solid mixing agent as desired in accordance with the purpose, thereby producing the soil improving mixing agent.
The above described mixing agent for hardening soil is added to 1 m
3
of soil, and mixed with 20 to 600 kg, more preferably with 50 to 300 kg, of cement to harden the soil. Upon mixing of the cement with the soil, if the soil does not contain sufficient moisture necessary for solidification of the cement, an appropriate quantity of water is added. If the soil contains enough moisture, it is not necessary to use additional water. When the cement mixed with the mixing agent is injected in the earth or added to sludge in marshes, for example, an appropriate quantity of water is added thereto.
When the cement is mixed with water, the elements in the cement such as CaO, SiO
2
, Al
2
O
2
, Fe
2
O
3
, solidify due to various reactions thereof, while forming various inorganic salts, crystals of water-containing salt thereof, and solid solution. The bonding of the solidified cement elements and the grains of soil must be strengthened in order to increase the hardness of the foundation. Moreover, the hardened soil must have numerous fine pores so as to be used for permeable road and parking lot, for solidifying sludge and planting greenery thereon, and for treating the normal plane of a river bank for growing plants. In order to achieve these objectives in the conventional soil-cement method, it is essential that, of various inorganic salts, needle crystals mainly comprising chlorettringite, which is a water-containing salt including four components which are CaO—SiO
2
—Al
2
O
3
—Cl must be formed and stabilized.
The soil hardening mixing agent of the present invention is used for the purpose of forming numerous fine pores about the firm and stable crystal group. In the improved soil, there is provided solid solution where various inorganic salts other than the chlorettringite, and planar or needle crystals of the water-containing salt thereof are mingled together. The solid solution is intensely bonded with the grains of the soil, thereby increasing the hardness thereof. In addition, the mixing agent for improving soil is used during a sludge treatment to chemically decompose the sludge and to decrease the quantity of odorous s

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