Generally, techniques in which the ratio of water to a powder, the dispersion condition of particles is changed by a pH regulator or a water-absorbing polymer is added to control excess water have been used to control the rheology characteristics, such as viscosity, of a slurry containing water and the powder.
In particular, the techniques in which a water-soluble polymer compound is added to a slurry system to make use of the thickening effect produced by the tanglement of the polymers ensure a large thickening effect at low costs and are put to practical use in a wide range of applications including civil/construction fields. For example, cellulose derivatives such as methyl cellulose and hydroxyethyl cellulose disclosed in JP-B5-39901 and water-soluble polymer compounds such as a poly(ethylene oxide) disclosed in JP-A11-189452 are used for pastes, mortars, underwater concretes, self-compacting concretes and the like to improve segregation resistance of materials.
Also, when a water-soluble polymer is used for a paste, mortar and concrete, many formulations in which the ratio of a powder is small (ratio of water/powder: 30% or more) are used. Formulations having a larger water-to-powder ratio are more reduced in the stability of viscosity with time and tend to give rise to segregation such as an outflow of bleeding water.
The pipe jacking method is one in which a drilling machine is attached to the distal end of a driving pipe (e.g., reinforced concrete pipe, hard vinyl chloride pipe, steel pipe and cast iron pipe) manufactured in factories and the pipe is pressed into the ground by the driving force of a jack to construct a pipe channel. The pipe jacking method is roughly classified into three construction methods, namely, “cutting edge pipe jacking method”, “closed type pipe jacking method” and “small-diameter pipe jacking method”. Particularly, the closed type pipe jacking method includes, for example, a mud pressure type pipe jacking method. In this method, while a “pipe jacking additive” is injected to promote the plastic and fluid properties of drilled sediment, it is mixed with drilled sediment by a drilling head, pressure is applied to the sediment by the driving force of a main pushing jack, the sediment's pressure is applied effectively on the whole cutting edge and the sediment is discharged with a screw conveyer, while maintaining the stability of the cutting edge, thereby to proceed in drilling.
The pipe jacking additive of pipe jacking method is used in the following cases: (1) where soil cannot be discharged smoothly even together with water, because of lack of fine grain content, in drilling in ground having a large coefficient of permeability, a lot of spring water and a small content of clay and silt, also called fine grain content, that is, soil having a particle diameter of 0.075 mm or less; or (2) where soil having a high porosity and a poor grain balance is converted to sludge having plastic and fluid properties and non-permeability.
As to, particularly, hydraulic compositions, in the meantime, there is a description concerning a hydraulic composition additive prepared by combining specified first and second compounds as a hydraulic composition additive which raises the viscosity and fluidity of concretes and the like and can impart excellent characteristics as to segregation resistance of aggregates, cement and water in JP-A2003-238222.
The additive described in JP-A2003-238222 is regarded as an additive that can impart excellent characteristics as to segregation resistance to a hydraulic composition as a slurry.