JPH10158052A - Slurry and powder of cement hydrate and cement composition containing the slurry or powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cement milk having low bleeding property and high density and showing desired strength without using calcium silicate hydrate by hydrating a cement with specified water/cement ratio and effecting the reaction while preventing aggregation. SOLUTION: A cement is mixed with water by 1 to 20 water/cement ratio and hydrated till the weight reduction by heating of the sample after dried at 80 deg.C becomes >=12%, and effected the reaction while preventing aggregation to obtain a cement hydrate slurry containing a cement hydrate having <=10μm average particle size. The cement hydrate slurry is dried till the weight reduction by heating at 80 deg.C becomes <=10%, and then classified to obtain <=10μm average particle size. Thus, a material with low bleeding property is obtd. comprising a cement hydrate powder having >=10,000m<2> /g Brain specific surface area. The material with low bleeding material, cement and water are compounded to obtain a cement milk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an underground diaphragm wall construction method,
Civil engineering such as muddy water method, pouring method, auger pile method, boring method, blanket method, caisson method, deep mixing method, column-type continuous wall, pouring grouting method, backfill pouring method, chemical liquid pouring method, lightweight embankment method, etc. The present invention relates to cement hydrate slurries and powders used in general construction work, and cement compositions containing these slurries and powders.

[0002]

2. Description of the Related Art In general, cement milk compounding used in various ground improvement methods, column-type continuous walls, injection methods, etc.
Water: about 50-200% in cement. In addition, there is a type in which air bubbles are mixed for the purpose of weight reduction.

[0003] Bentonite is mainly used as a material for reducing the bleeding of cement milk.
Bentonite has the property of absorbing water and expanding its apparent volume several times.

[0004]

In the case of cement milk, material separation of the cement milk suspension occurs due to bleeding, which leads to troubles in construction, reduction of compacts such as ground improvement bodies and cement milk column piles. In addition, problems such as variations in strength in the height direction occur.

[0005] Cement bentonite milk (hereinafter referred to as CB milk) is a mixture containing bentonite for the purpose of preventing bleeding of cement milk.
The problem of B milk is low bleeding, but there are many problems in construction.

[0006] The main component of bentonite is montmorillonite, which swells due to its layered structure. However, this montmorillonite does not swell due to the exchange reaction in the presence of calcium ions. It is necessary to perform two-stage kneading in which muddy water is produced, and after sufficient swelling, cement is charged. If cement and bentonite are kneaded at the same time, bleeding of CB milk occurs to the same extent as that of cement milk alone. In addition, bentonite does not swell in water containing calcium ions such as seawater, so that there is a problem in application to gulf construction.

[0007] CB milk is a highly viscous slurry. High viscosity slurries often cause construction problems such as injection pumping ability, ground injection resistance, and mixing resistance.
In the method of recovering surplus soil and solidified material on the ground surface, increasing the viscosity of the slime is a major cause of pipe blockage problems. At sites where bentonite is used only for the purpose of preventing bleeding, the low viscosity of cement milk is ideal.However, in order to prevent bleeding, bentonite is used, and in practice it is difficult to increase viscosity which is not desirable in construction. It is. In order to ensure a normal construction state, the limit of the amount of bentonite added to cement is generally said to be about 15% by weight.

In some cases, the strength of the improved body (solidified body) is required to be low for the purpose of construction. Applications include improvement work that requires re-excavation such as starting and reaching standing piles, solidification of the entire target ground such as ground liquefaction countermeasures, and the same strength as the injected ground, such as the shield backfill injection method. Some are required to be expressed.

In the case of a low-strength improved body, the strength of the improved body is affected by the unit cement amount, and it is necessary to reduce the cement amount. This means that the water / cement ratio increases, and the solidified body has a low density, which causes a problem in durability. When bentonite is positioned as powder in milk, if it is desired to obtain high-density milk, it is conceivable to increase the amount of bentonite mixed and increase the powder concentration in milk without increasing the amount of cement, There is a limit in dealing with the problem.

[0010] The problems of the CB milk as described above are summarized as follows. Bentonite takes time with two-stage kneading,
Moreover, there is no construction capability (flashing power) due to the two-stage kneading (the simultaneous kneading of cement and bentonite is not possible). Since bentonite cannot be premixed with cement, two separate silos of bentonite and cement are required. Seawater cannot be used and cannot be applied to soils affected by seawater. It is a highly viscous milk. Low-strength, high-density (high powder content) milk is highly viscous and cannot be pumped. Bentonite is a natural mineral and its quality varies, so that CB milk with stable quality cannot be produced.

These problems can be solved by using, for example, a synthetic calcium silicate hydrate powder. However, depending on the properties of the raw material silicate or calcium silicate,
The reaction time and the production method need to be devised, which may cause a cost problem.

On the other hand, JP-A-58-173183 and JP-B-5-173183 disclose the use of inexpensive calcium silicate hydrate.
There is also a technique disclosed in -81546, but in these cases the water / powder ratio is small.

However, it is necessary to suppress bleeding when the water / powder ratio is large.

Further, Japanese Patent Application Laid-Open No. 58-173183 and Japanese Patent Publication No.
The use amount of calcium silicate disclosed in -81546 is insufficient as the bleeding suppressing ability and cannot be used as a general bleeding reducing material.

The present invention has been made in order to solve all of the above problems, and has low bleeding, high density, low viscosity, low strength to high strength without using calcium silicate hydrate. It is an object of the present invention to obtain a cement milk exhibiting any desired strength.

[0016]

In order to solve such a problem, the inventors of the present invention have generally used Portland cement, which is generally available at a low cost, as a raw material and hydrated under specific conditions. The present invention was found to be useful as a material for reducing bleeding, and the present invention was completed.

That is, the present invention provides a cement hydrate slurry and a method for producing the same, a cement hydrate powder, and a cement composition and a cement milk containing these cement hydrate slurry and cement hydrate powder. The characteristics as a cement hydrate slurry include a cement hydrate hydrated until the loss on ignition of the sample after drying at 80 ° C is 12% or more, and the average particle size is It is set to 10 μm or less.

A feature of the method for producing a cement hydrate slurry is to produce a cement hydrate slurry by hydrating cement at a water / cement ratio of 1 to 20 and reacting so as not to aggregate.

Further, the feature of the cement hydrate powder is that the cement hydrate slurry hydrated until the loss on ignition of the sample after drying at 80 ° C. becomes 12% or more is reduced when dried at 80 ° C. Is dried to 10% or less, and the average particle size is
It is classified so as to be 10 μm or less, and has a Blaine specific surface area of 10,000 cm ² / g or more.

Further, the characteristics of the cement composition include:
The cement hydrate slurry hydrated until the loss on ignition of the sample after drying at 80 ° C is 12% or more is dried so that the loss on drying at 80 ° C is 10% or less, and the average particle size is 10μ
m and the specific surface area of Blaine
It is that the cement hydrate contains a cement hydrate powder of 10,000 cm ² / g or more and cement.

Further, the characteristics as cement milk are as follows:
A cement hydrate slurry containing cement hydrate having an average particle size of 10 μm or less, hydrated until the loss on ignition of the sample after drying at 80 ° C. is 12% or more, cement, and water It has been included.

Further, another characteristic of the cement milk is that the cement hydrate slurry hydrated until the loss on ignition of the sample after drying at 80 ° C. becomes 12% or more is reduced when dried at 80 ° C. Dried to 10% or less and average particle size
The reason for this is that it contains cement hydrate powder having a Blaine specific surface area of 10,000 cm ² / g or more, which is classified so as to have a particle size of 10 μm or less, cement, and water.

The cement hydrate of the present invention can be used as described above.
Cement is hydrated until the loss on ignition of the sample after drying at 80 ° C is 12% or more, and the average particle size is 10 μm.
It consists of the following particles.

In the production method, the cement particles are hydrated in a water / cement ratio of 1 to 20 with high-speed stirring or in a ball mill so that the cement particles do not aggregate during hydration.

The slurry containing the cement hydrate can be used as it is or after drying.

When drying, the material is dried until the loss on drying at 80 ° C. becomes 10% or less, and classified so that the average particle size becomes 10 μm or less.

This powder has a Blaine specific surface area of 10,000 cm ²
/ g or more.

When the slurry is used as it is, necessary amounts of cement and water are added at the time of use.

In the case of a dry powder, it can be mixed with cement in advance, and is mixed with water at the time of use.

As the cement, a mixed cement such as Portland cement, blast furnace cement, fly ash cement and the like can be used.

Further, various known admixtures and extenders may be added to the above-mentioned cement milk as required.

[0032]

Since the present invention has the above-described structure, the following effects are obtained.

The solid surface in contact with the aqueous solution has a surface charge due to the adsorption of ions from the solution or the dissociation reaction of the surface.

The counter ion in the solution having the opposite sign to the surface charge is electrostatically attracted to the surface charge and forms an electric double layer at the solid-liquid interface. Due to this electric double layer, a repulsive force acts between the solids having the same charge, and an attractive force acts between the solids having the different charge.

Further, an intermolecular attractive force acts between the solids, and dispersion and agglomeration occur due to these balances.
By controlling the dispersion and aggregation, bleeding can be suppressed and the viscosity can be reduced.

The cement hydrate according to the present invention has been developed for the purpose of reducing the bleeding of cement milk. The hydrate forms a floc by a weak cohesive force and acts to suppress the occurrence of bleeding by confining water inside the floc. is there.

On the other hand, since the cohesive force is weak, the floc is eliminated when a force is applied from the outside or during the flow, and the water trapped in the floc becomes free water to obtain fluidity. Can be.

Portland cement is alite, bi
Calcium silicate compound called 3lite and 3CaO
・ Al_TwoO_ThreeAluminate phase or 4CaO.
Al _TwoO_Three・ Fe_TwoO_ThreeFrom a ferrite phase whose main component is
You.

It is said that the surface potentials of calcium silicate, aluminate and ferrite phases have opposite signs, and flocs due to aggregation are more easily formed than hydrates having the same sign of calcium silicate alone. it is conceivable that.

In addition, the effect of gypsum in cement and fine calcium hydroxide generated by hydration increase the bleeding suppressing effect.

Since the bleeding reducing material according to the present invention is a hydration product of cement, when used in cement milk, it forms a hydrated layer upon contact with water so that it has almost the same surface properties as the bleeding reducing material. Forms a uniformly dispersed floc with the cement.

This means that not only the properties of the cement milk in a slurry state can be made uniform, but also the properties after curing can be made uniform.

From the above reasons, it is preferable that calcium silicate hydrate, aluminate, and ferrite hydrate having charges of different signs appear on the particle surfaces of the cement hydrate as the bleeding reducing material for the above reasons. . Therefore, it is better to be formed from fine particles.

The average particle size is 10 μm or less, preferably 6 μm or less.

For this purpose, it is important to hydrate while dispersing as much as possible using high-speed stirring or a mill during production.

Even when a block-like cement hydrate, such as a usual hardened cement, is produced and dried and pulverized, the specific surface area is small, and the specific surface area is small, as described in JP-A-58-173183 and JP-B-5-8154.
As in No. 6, the bleeding prevention effect is small.

By adjusting the water / cement ratio at the time of hydration to 1 to 20, the Blaine specific surface area (measured on a dry powder) of the formed particles must be 10,000 cm ² / g.

If it is smaller than 1, it is difficult to make the dispersion uniform, and a coagulated and hardened hydrate is formed, which is not preferable.

On the other hand, if it is larger than 20, the effect on the performance is small, but if it is used as a cement milk, the effective ingredient is too small, and if it is used as a powder, separation and drying are troublesome and uneconomical.

The degree of hydration can be judged by the weight loss when the slurry is dried at 80 ° C. and then ignited at 1000 ° C. It is necessary that the hydration be at least 12%.

Below this, the unreacted cement component is too large to provide a sufficient bleeding suppressing effect.

When used in a slurry state, there is a problem that the quality fluctuates during storage.

When the slurry is dried to obtain a powder,
Dry the dried product so that the weight loss when placed at 80 ° C for 24 hours is 10% or less.

If there is more water than this, it changes during storage alone or mixed with cement.

Since light agglomeration occurs during drying, the average particle diameter is preferably 10 μm or less, preferably 6 μm using a classifier or the like.
It is necessary that the specific surface area of the powder be not less than 10,000 cm ² / g.

The cement hydrate powder thus produced can be used by previously mixing a predetermined amount with Portland cement.

Although the bleeding rate varies depending on the water / cement ratio, effective bleeding suppression performance is achieved by mixing 3 to 100 parts by weight of the cement hydrate of the present invention with 100 parts by weight of Portland cement. Is the case.

If it is less than 3, the bleeding suppressing effect is not sufficient, and if it exceeds 100, the cement hydrate according to the present invention may be used.
This can be achieved by adding a conventional fine powder material.

[0059]

Embodiments of the present invention will be described below.

Example 1 Commercially available ordinary Portland cement and early-strength Portland cement were hydrated in a ball mill while changing the water / cement ratio to produce various hydrated cement hydrates. When measuring the bleeding rate, when using the slurry as it is, add cement and water so that the cement hydrate content in the slurry becomes 100 g / L and ordinary Portland cement become 300 g / L, stir, and then use a 1000 mL graduated cylinder. Put in
The bleeding rate after 24 hours was measured.

In the case of a water / cement ratio of 20, the amount of water is too large to adjust to the desired hydrate concentration.

In the case of dried cement hydrate, 3 times the amount of ordinary Portland cement is added and mixed, and then 400 g of the mixture is added.
/ L was added and stirred, and the mixture was placed in a 1000 mL graduated cylinder, and the bleeding rate after 24 hours was measured.

The weight loss of the dried cement hydrate when dried at 80 ° C. for 24 hours was all within 5%.

As shown in Table 1, the smaller the water / cement ratio at the time of production and the loss on ignition of the sample after drying at 80 ° C., the larger the average particle size and the bleeding rate.

[0065]

[Table 1]

At a water / cement ratio of 0.5, the slurry was too viscous to produce well.

The water / cement ratio at the time of production is 1 or more and 80
Cement hydrate having a loss on ignition of the sample of 12% or more after drying at ℃ showed a small bleeding rate.

Example 2 A slurry of the sample CSH5 of Example 1 was dried under various conditions to produce a cement hydrate powder.

The bleeding rate was measured in the same manner as in the case of the dried cement hydrate of Example 1, and the bleeding rate after storing the mixture of cement and hydrate for one month was also measured.

As shown in Table 2, the particles aggregate during drying, and if not classified, the average particle size increases and the bleeding rate increases.

[0071]

[Table 2]

The samples CSHP1 and 2 whose weight loss after drying at 80 ° C. for 24 hours had a weight loss of 10% or more showed an increased bleeding rate after storage for one month.

Example 3 100 g of the sample CSHP6 of Example 2 and 250 g of ordinary Portland cement were weighed and mixed as it was or beforehand, and water was added so that the total amount was 1000 mL, followed by stirring with a mixer for 1 minute.

As a comparative example, 100 g of bentonite and 250 g of ordinary Portland cement were weighed, and the total amount was 1000 mL.
Was added thereto, and the mixture was stirred for 1 minute with a mixer.

In the case of bentonite, the mixing was carried out before mixing with water and then adding cement, and simultaneously kneading.

Table 3 shows the bleeding rate after 24 hours.

[0077]

[Table 3]

It can be seen that, even when the cement hydrate is used by previously mixing it with the cement, it exhibits the same performance as that obtained when kneaded with bentonite and water.

It can be seen that the simultaneous introduction of bentonite and cement shows a large bleeding rate under the influence of cement.

Example 4 100 g of the sample CSHP6 of Example 2 and 250 g of ordinary Portland cement were weighed out, seawater was added to make the total amount 1000 mL, and the mixture was stirred for 1 minute with a mixer.

As a comparative example, seawater was added to 100 g of bentonite, kneaded in advance, and 250 g of ordinary Portland cement was added.
, And add seawater so that the total volume becomes 1000 mL,
The mixture was stirred for 1 minute.

The bleeding rate after 24 hours is shown in Table 4.

[0083]

[Table 4]

As is clear from Table 4, the bleeding suppressing performance of bentonite was greatly reduced by seawater, but there was no problem in the case of cement hydrate, and there was no problem.

Example 5 Water was added to a mixture obtained by changing the mixing ratio of the sample CSHP6 cement hydrate of Example 2 and ordinary Portland cement to give a strength of 2, 5, 10, 15, 20, 25 N / mm for 4 weeks. ^The cement milk which became ² was manufactured.

The bleeding rate and the flow time (pre-backed flow) of the P funnel in each of the formulations were measured.

As a comparative example, measurement was also made when bentonite was used in the same composition.

The bentonite was used in the same amount as the cement hydrate, kneaded with water for 1 minute, and then ordinary Portland cement was added and stirred again for 1 minute.

Further, a comparative test was also carried out for the case where the mixing ratio of the cement hydrate and the cement was large and the case where the mixing ratio was small
The case where limestone powder having a Blaine specific surface area of 10,000 cm ² / g and an average particle size of 3.5 μm was used in combination was also examined.

Table 5 shows the results. In Table 5, * indicates that limestone powder was added, and X indicates that the powder did not flow down.

[0091]

[Table 5]

As shown in Table 5, the bleeding ratio of bentonite is 0%, but the viscosity is so high that the flow value cannot be measured.

On the other hand, the cement hydrate has a flow value of 8 to
A low viscosity of 13 seconds can be achieved.

This is because the use of cement hydrate increases the milk concentration (the amount of powder in milk) to produce high-concentration milk, and further improves the strength from a low strength to a high strength of 25 N / mm ^2. This indicates that the intensity can be set freely.

When the amount of cement hydrate is less than 3% of the cement as in Comparative Example 5.1, bleeding tends to occur.

When the amount of addition exceeds 100% relative to the cement as in Comparative Example 5.2, it is possible to partially replace it with limestone powder or the like as in Comparative Example 5.3.

However, when the replacement amount was too large, the amount of Comparative Example 5.
Bleeding occurs as shown in 4.

Example 6 The mixing ratio of the ordinary Portland cement and the cement hydrate sample CSHP6 of Example 2 was 1: 1, 2: 1, and 4: 1 by weight.
, 6: 1, 8: 1, 10: 1, 20: 1, 30: 1, and add water so that the water / (cement + cement hydrate) ratio is 100, 200, 300%. The volume was adjusted to 1000 mL, and the mixture was stirred with a mixer for 1 minute to prepare a cement milk, and the P funnel (prepacked flow) was measured.

As a comparative example, measurement was also made when bentonite was used in the same composition.

The same amount of bentonite as the cement hydrate was used. For kneading, only bentonite was first kneaded with water for 1 minute, then ordinary Portland cement was added, and the mixture was stirred again for 1 minute.

Table 6 shows the results.

[0102]

[Table 6]

As can be seen from Table 6, the cement milk using the cement hydrate has a lower viscosity than the CB milk using the bentonite.

Embodiment 7 This embodiment is an embodiment in which the present invention is used as a backfill injection material to be injected into a tailpoid generated during shield excavation.

Cement hydrate sample CSHP6 of Example 2
90g, add water to 250g of ordinary Portland cement and add 10
Make up to 00 mL, mix for 1 minute with a mixer, and use this as solution A.

A mixture of 60 mL of No. 3 water glass and 20 mL of water is referred to as a liquid B.

Bleeding rate of solution A after 24 hours,
The compressive strength was measured for the time until 1000 mL of solution A and 80 mL of solution B were mixed and gelled, and for 1 hour, 7 days and 28 days for the gelled material.

As a comparative example, 874 g of water was added to 90 g of bentonite.
, And stirred for 1 minute by a kneader, 250 g of ordinary Portland cement was added, and the mixture was further stirred for 1 minute to prepare a liquid A.

The bleeding rate of the solution A, the gel time when combined with the solution B, 1 hour
The compressive strength on the 28th and 28th was similarly measured.

The results are shown in Table 7 below.

[0111]

[Table 7]

As shown in Table 7, the bleeding rate of backfill material A prepared using cement hydrate, the gel time when mixing liquid B, 1 hour of the gelled product, 7 hours
Both the compressive strengths on the 28th and 28th were comparable to those using bentonite, and it was found that there was no problem in practical use.

Example 8 This example relates to cement milk which is a material used in the injection replacement method performed as a foundation work for civil engineering and construction.

Cement hydrate sample CSHP6 of Example 2
60 kg, 700 kg of ordinary Portland cement and 750 kg of water were mixed, and the bleeding rate after 3 hours was measured.

As a comparative example, ordinary Portland cement
Mix 760 kg with 750 kg of water to make cement milk,
The bleeding rate after 3 hours was measured.

Table 8 shows the results.

[0117]

[Table 8]

As is clear from Table 8, it was confirmed that when the cement hydrate was used, the bleeding rate was smaller than that of the conventional cement milk which was generally used.

Embodiment 9 This embodiment relates to SMW performed as a foundation work for civil engineering and construction.
The present invention relates to cement milk which is a material used for (soil mixing wall).

Cement hydrate sample CSHP6 of Example 2
Was mixed with 250 kg of ordinary Portland cement and 600 kg of water, and the bleeding rate after 1 hour was measured.

As a comparative example, 10 kg of bentonite and 250 kg of ordinary Portland cement were mixed with 600 kg of water, and the bleeding ratio after one hour was measured.

Table 9 shows the results.

[0123]

[Table 9]

As is clear from Table 9, when the cement hydrate was used, it was found that the bleeding rate was smaller and superior to that of the conventionally used cement milk of the comparative example.

[0125]

As described above, according to the present invention, a bleeding reducing material having the same performance as bentonite was obtained. This is especially useful for cement milk.

Further, the cement hydrate of the present invention can achieve low bleeding without being affected by ions such as Ca and Na as in conventional bentonite.

Further, generally, Portland cement, which can be obtained at low cost, is used as a raw material, and its quality is stable as compared with bentonite and natural substitute materials.

Further, unlike bentonite, cement and premix can be used, so that there is an advantage that labor can be saved in construction.

When the bleeding reducing material as described above is used as cement milk, there is an effect that, unlike bentonite, a material having a low viscosity can be obtained.

Further, even if the mixing amount is increased, low viscosity can be maintained up to a certain amount, so that cement milk with low strength and high concentration can be produced.

Since the cured product is made of the same cement hydrate, there is an effect that a uniform structure is formed and high durability can be achieved.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kensuke Kanai 7-55 Minamionkajima, Taisho-ku, Osaka Sumitomo Osaka Cement Co., Ltd. Cement Concrete Research Laboratory (72) Inventor Hiroaki Suzuki Taisho-ku, Osaka-shi 7-55 Minamionkajima Sumitomo Osaka Cement Co., Ltd. Cement Concrete Research Laboratory (72) Inventor Shingo Shimimi 7-55 Minamienkajima, Taisho-ku, Osaka City Sumitomo Osaka Cement Co., Ltd. Inside the concrete laboratory

Claims (6)

[Claims] 1. A sample having a loss on ignition of 12 after drying at 80 ° C.
%. A cement hydrate slurry comprising a cement hydrate having an average particle size of 10 μm or less, hydrated to a concentration of not less than 10%. 2. A method for producing a cement hydrate slurry, comprising hydrating cement at a water / cement ratio of 1 to 20 and reacting the cement so as not to aggregate, thereby producing a cement hydrate slurry. 3. The sample having a loss on ignition of 12 after drying at 80 ° C.
% Hydrated cement hydrate slurry is dried so that the weight loss when dried at 80 ° C is 10% or less,
A cement hydrate powder characterized by being classified so as to have an average particle size of 10 μm or less, and having a Blaine specific surface area of 10,000 cm ² / g or more. 4. A sample having a loss on ignition of 12 after drying at 80 ° C.
% Hydrated cement hydrate slurry is dried so that the weight loss when dried at 80 ° C is 10% or less,
A cement composition characterized by containing cement and a cement hydrate powder that has been classified so as to have an average particle size of 10 μm or less, and has a Blaine specific surface area of 10,000 cm ² / g or more. 5. A sample having a loss on ignition of 12 after drying at 80 ° C.
%, Comprising a cement hydrate slurry containing a cement hydrate having an average particle size of 10 μm or less, cement, and water, hydrated to not less than 10% by weight. 6. The sample having a loss on ignition of 12 after drying at 80 ° C.
% Hydrated cement hydrate slurry is dried so that the weight loss when dried at 80 ° C is 10% or less,
A cement milk characterized by comprising a cement hydrate powder, a cement hydrate powder having a Blaine specific surface area of 10,000 cm ² / g or more, which is classified so as to have an average particle diameter of 10 μm or less, cement, and water.