JPS6262886A - Ground improving material - Google Patents

Abstract

PURPOSE:An improving material, consisting of granulated blast furnace slag, slaked lime and moderate heat portland cement, capable of increasing the extension of strength for a long period while suppressing the initial strength at a small value and suitable for flimsy soil, e.g. sea bottom and land, mainly by a depth mixing treatment construction method. CONSTITUTION:An improving material obtained by incorporating (A) granulated blast furnace slag with (B) preferably <=15wt%, particularly 5-10wt% slaked lime and (C) preferably 15-30wt% moderate heat portland cement. EFFECT:Since the above-mentioned improving material has improved setting performance, the amount thereof to be used is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention mainly relates to improved materials for soft and weak materials (on the seabed and on land) by a deep mixing treatment method.

(Prior Art and its Problems) Conventional soil improvement materials include ordinary Portland cement (hereinafter simply referred to as ordinary cement), blast furnace cement, lime, and the like.

However, the strength development characteristics improved by these improved materials are not necessarily optimal for various ground improvement works, whether on land or at sea, or they may form improved surfaces with a high pH value. As a result, there are problems such as making it undesirable for growing plants.

In addition, as a special case, when carrying out construction work using improved materials in the form of slurry, problems such as the improved materials condensing inside the transport pipes during transportation of the slurry, causing problems with the transport pipes, have been pointed out. A solution was strongly desired.

For this reason, wood inventors have already invented various compounding systems based on granulated blast furnace slag powder (hereinafter simply referred to as slag) as ground improvement materials for deep mixing treatment, and have No. 58-194977, Japanese Patent Application Publication No. 1983
-91190 and JP-A-59-193984.

Among these, the slag-slaked lime system and the slag-moderate heat Portland cement system are currently in practical use (
In both cases, the improvement of soft seabed soil is specifically considered.)

Although these improved materials have excellent strength development characteristics for deep mixing treatment, they have not reached the point where a wide range of strength development patterns can be expected. The strength of the improved soil improved by the improving material is relatively low in the early stage of the material's life (for example, the compressive strength at 3 days old is less than 5 K g f / cm'). )in,
In addition, it was required to have a property of exhibiting relatively high strength in the long term (for example, 50 K g f / cm' at 91 days of age).

However, in cases where the improvement depth is not as great as in offshore construction, such as deep mixing treatment work on land-L, and where there are almost no problems with the construction period due to weather conditions, the improvement This means that the initial strength of the material may be greater than that required for offshore construction (
(Specific required strength values vary depending on individual construction projects and cannot be specified uniformly.)

In addition, in many cases, it is desirable for the long-term material strength to be high for improvement purposes. In other words, if we take deep mixing treatment construction on land as an example, the strength development characteristics of the improved materials used for it tend to be the same as those for offshore construction.
In addition, it can be said that a somewhat high strength value is required.

The strength development tendency of conventionally used ordinary cement and blast furnace cement is that the initial development accounts for a large proportion of the total strength development, and is not suitable for deep mixing treatment, especially in the case of ordinary cement.

The present invention was proposed as a result of studies to solve these conventional problems.

(Means for Solving the Problems) In order to solve the above problems, the basic feature of the present invention is that the ground improvement material is composed of granulated blast furnace slag, slaked lime, and moderate heat Portland cement. be. That is, the slag-slaked lime system and the slag-moderate heat Portland cement system i1 are useful as ground improvement materials for deep layer 42 treatment. ! A problem with improved materials is that if the initial strength is kept low, sufficient strength cannot be obtained over a long period of time. As a result of research to solve this problem, we created a ground improvement material by mixing slag powder with slaked lime and moderate heat Portland cement.

It was found that the long-term strength of this material increased significantly compared to conventional improved materials. In this case, the blending ratio of slaked lime is 15
It is preferably 5% to 10% by weight or less, more preferably 5 to 10% by weight.
It is. The blending ratio of moderate heat Portland cement is 15
-30% by weight is preferred; however, if the blending ratio of slaked lime exceeds 15% by weight, the long-term strength will actually decrease.

(Example) Hereinafter, the present invention will be explained in detail using Examples and Comparative Examples.

The chemical composition and fineness of the granulated blast furnace slags A and B used here are shown in Table 1.

Granulated blast furnace slag A, slaked lime and moderate heat Portland cement in weight percentages of 70:0:30 and 70:5, respectively.
A ground improvement material was prepared by mixing the ingredients in the following ratios: 25, 70:10:20 and 70:15:15. these#! The characteristics of the soil improvement material are shown in Table 4.
After adding g and mixing, mold into φ50 x 100 mm,
It was sealed and cured in water at 20±2°C.

The -axial compressive strength was measured at specified ages (3, 7, 28 and 91 days). The measurement results are shown in Table 2.

1) Granulated blast furnace slag B, slaked lime and moderate heat Portland cement in weight% of 70:0:30 and 70:5, respectively.
A ground improvement material was prepared by mixing the ingredients in a ratio of 25, 70:10:20 and 70:15:15. The same operation as in Example 1 was performed, and the -axial compressive strength was measured. The measurement results are shown in Table 3.

A ground improvement material was prepared by mixing granulated blast furnace slag A, slaked lime, and moderate heat Portland cement in a weight percent ratio of 70:20:10. The same operation as in Example 1 was performed, and the -axial compressive strength was measured. Table 2 shows the measurement results.
Shown below.

A ground improvement material was prepared by mixing granulated blast furnace slag B, slaked lime, and moderate heat Portland cement in a weight ratio of 70:20:10, respectively. The same operation as in Example 1 was performed, and the -axial compressive strength was measured. Table 3 shows the measurement results.
Shown below.

Table 4 Characteristics of sample extraction (physical test condensation (effect)) As is clear from the above examples, the ground improvement material according to the present invention can suppress initial strength to a low level while greatly increasing long-term strength. The ground improvement material of the present invention also has the advantage of reducing the amount of improvement material used. arise.

Claims (2)

[Claims] (1) A ground improvement material composed of granulated blast furnace slag, slaked lime, and moderate heat Portland cement. (2) The invention according to item 1 above, wherein the blending ratio of slaked lime is 15% by weight or less, and the blending ratio of moderate heat Portland cement is 15 to 30% by weight.