JPS5914417B2 - cement additives - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cement additive comprising a naphthalene sulfonic acid formaldehyde high condensate or its salt (hereinafter abbreviated as NS) and polyvinyl alcohol (hereinafter abbreviated as PVA), and more specifically, Concrete is a hydraulic cement mixture.

The present invention relates to a cement additive that prevents the fluidity of mortar or paste from decreasing over time and improves its workability and workability.

Conventionally, cement, water and if necessary sand, gravel.

Cement mixtures made by mixing admixtures (agents) undergo physical and chemical aggregation of cement particles over time after being mixed, and do not gradually lose fluidity, resulting in poor workability and workability over time. decreases.

For this reason, cement compositions have the disadvantage that their workable time (pot life) is limited.

Furthermore, after the cement mixture is mixed, it is often transported to the pouring site by an agitator truck (ready concrete mixer truck), and the time required for transportation varies greatly depending on the transportation distance, traffic congestion, etc.

For this reason, at the pouring site, the fluidity differs depending on the agitator car, making it extremely difficult to obtain consistent workability.

In addition, when pumping a cement mixture, if the pumping is temporarily interrupted due to a lunch break or changing stages, and then the pumping is restarted, the fluidity of the cement mixture in the piping will decrease and the pumping will be delayed when the pumping is resumed. There are also many problems such as a sudden increase in pressure or blockage.

Furthermore, in the case of centrifugally compacted concrete or mortar, centrifugal forming forms are filled with concrete after mixing, and centrifugal compaction is often started when several forms have been filled.

In this case, if it takes time to fill the formwork, the fluidity of the concrete decreases and centrifugal compaction becomes difficult.

For this reason, several methods have been devised to prevent the decline in fluidity of cement mixtures.

For example, there is a method of adding a curing retarder such as oxycarboxylic acid for the purpose of preventing chemical aggregation.

Although this method can delay the water utilization reaction of cement, it is difficult to prevent physical agglomeration, and therefore slump loss cannot be prevented.

Further, there are disadvantages such as a decrease in the early strength of concrete and mortar.

There is a method of preventing slump loss by adding granular concrete fluidizing agent such as NS to concrete, etc., and gradually dissolving the granular fluidizing agent (Japanese Patent Laid-Open Publication No. 139929/1989: This method can prevent slump loss to some extent, but the strength is due to the granular fluidizer remaining locally in the concrete after hardening.

This results in drawbacks such as decreased durability.

There is also a method of maintaining the fluidity of concrete for a long time by adding a fluidizing agent such as NS to concrete etc. in portions or continuously (Japanese Patent Publication No. 51-15856).

Although this method is effective as a method for preventing slump loss, it is time-consuming to add the fluidizing agent, and the fluidizing agent may It is not possible to prevent slump loss in concrete where it is difficult to add separately.

These conventional methods for preventing a decrease in the fluidity of cement mixtures have had many problems and have not been considered satisfactory.

The present invention has been made to improve the drawbacks of the conventional methods described above. By mixing NS and PVA in a specific proportion, this mixture maintains the fluidity of the cement mixture for a long time and maintains the fluidity at a constant level. As a result, they have found that the scales can significantly improve construction and workability, and have completed the present invention.

That is, the present invention uses 100 parts by weight of N5 and 4 to 20 parts by weight of PVA.
It is a cement additive consisting of parts by weight, and is an extremely effective cement additive for preventing a decrease in the fluidity of cement mixtures, that is, for preventing slump loss.

The mechanism of preventing slump loss according to the present invention is inferred as follows.

Cement, water and if necessary sand, gravel, admixtures (agents)
The cement particles in the cement mixture consisting of
After crosstalk, chemical aggregation due to water use reactions and physical aggregation due to interparticle attraction progress, resulting in a gradual loss of fluidity.

For this reason, slump loss occurs in cement mixtures such as concrete-Dou7 mortar.

By adding an anionic surfactant such as NS at this point, a repulsive force is generated between the cement particles, the cement particles are dispersed, and fluidity is improved, so that slump loss can be temporarily prevented.

However, the water utilization reaction of cement progresses further, and a gel of Etrin guide (commonly known as Cementobacillus or calcium sulfoaluminate) is continuously produced.

As a result, the fluidity of the system continues to decrease, and NS etc. are adsorbed or stored in new precipitated minerals such as ettrin guides that are newly formed in the solution and on cement particles, and the NS concentration in the solution decreases. , aggregation of cement particles progresses.

Here, if NS, which is the main dispersion agent of cement particles, can be continuously supplied by some method, slump loss can be prevented.

As a result of intensive research, the present inventors have invented a cement additive that can continuously supply NS, which is the main dispersion agent of cement particles, into a cement mixture and maintain its fluidity for a long time. .

That is, in the cement additive according to the present invention, NS
It is assumed that a complex is formed with a 1:1 molar ratio of polymerized units of PVA and PVA, and this complex is caused by NS in the cement compound solution being stored in new precipitated minerals such as Etrin guide, and When the NS concentration decreases and the system becomes unbalanced, the complex consisting of NS and PVA dissociates at a moderate rate, as if to compensate for NS, and gradually releases NS into the solution.

It is presumed that the fluidity of the cement mixture can be maintained for a long time by maintaining the NS concentration in the cement mixture solution within a certain range through dissociation of this complex, that is, sustained release of NS.

The complex in the present invention refers to the polyvalent metal of NS or Ca'' present in the cement mixture.

It is assumed that this is an intermolecular metal complex between NS and PVA, as shown in the formula below, which occurs when polyvalent metals such as Fe, Fe, Mg, or calcium chloride, iron chloride, etc. are added to the cement mixture.

M: A certain chain length (
(critical chain length), that is, the participation of a certain number or more of reactive groups is required, and NS has a viscosity of 1.0 in a 10% aqueous solution at 30°C.
High condensate with increased condensation degree showing 5 cps or more, PV
When A has a degree of polymerization of 1,000 or more, the formation of a complex is observed for the first time.

The cement additive according to the present invention differs from those in which NS is encapsulated or granulated, in that the complex becomes ultra-fine particles and dissolves in the cement mixture, and eventually disappears by dissociation and diffusion. It does not have the disadvantages of localized presence of grains and particles in cement formulations.

The NS used in the present invention must be a salt having a viscosity of 1.05 to 1.25 cps in a 10% aqueous solution at 30 DEG C., and preferably a sodium salt or a calcium salt.

In addition to naphthalene sulfonic acid formaldehyde high condensates or their salts, NS may also include co-condensates of naphthalene sulfonic acid and other chemicals, such as benzene sulfonic acid, toluene sulfonic acid, benzoic acid, phthalic acid, and lignin sulfonic acid. It's okay.

Furthermore, mixtures of naphthalene sulfonic acid formaldehyde high condensates or salts thereof and other chemicals, such as lignins and oxycarboxylic acids.

Sugars, dialkyl sulfosuccinic acids, rosin soaps.

It may also be a mixture with other cement admixtures such as air-entraining agents, early-strengthening agents, retarders, water-reducing agents, fluidizing agents, waterproofing agents, and the like.

PVA has a polymerization degree of 1000 to 2700. Saponification degree 70-99
．． It needs to be 9 mol%, and it is possible to use a compound generally called polypinol which has many hydroxyl groups and other groups in its side chains.

NS, which is a component of the present invention, is known as a cement additive (Japanese Patent Publication No. 41-11737), and PVA is also known as a cement additive (Tasushi Shibasaki, Cement Technology Annual Report, X■, 194-199). .

Method for producing lightweight concrete by adding NS and PVA to cement (Special Publication No. 55-37513)
(Japanese Patent Laid-Open Publication No. 1983-1999) and a method for fluidizing concrete (Japanese Patent Application Laid-open No.
75955) is publicly known.

Although the inventive concept of the present invention is clearly different from the above-mentioned known technology, after dissociation of the complex, NS and PVA
is present in cement formulations.

However, in this case, the amounts of NS and PVA in the cement mixture are as follows:
This method is clearly different from the method described in Japanese Patent No. 5-75955.

In other words, the amount of water-soluble polymer substance in the method of Japanese Patent Publication No. 55-37513 is 0.2 to 3% by weight of the amount of cement (600g to 9000% if the amount of cement is 300 kg/m).
g), and if such a large amount is used, the fluidity of concrete will be inhibited and the fluidity of concrete cannot be kept constant.

The amount of organic sizing agent in the method of JP-A-55-75955 is 10 to 61 per m' of concrete.

In this case, even if PVA is used as an organic sizing agent, the effects of the present invention cannot be achieved in such a small amount.

The amount of PVA in the cement mixture after complex dissociation in the present invention is 70 to 450 g per 1 m3 of concrete.
It is.

The cement additive according to the present invention can be added to a cement mixture either in the form of an aqueous solution (slurry or gel) or in the form of two powder particles. It is also possible to add it to the cement mixture once it has been kneaded.

Also, NS and PVA may be mixed in advance,
Alternatively, one may be blended into cement, or one may be blended into cement and kneaded before the other is blended.

Other cement additives (materials) such as concrete water reducer, air entrainment agent, fluidizing agent, waterproofing agent, swelling agent (material), glass fiber, steel fiber fly ash,
It can also be used in combination with blast furnace slag, etc.

Concrete containing such a cement additive according to the present invention can be cured by a conventional method of curing concrete, and can also be cured by methods such as steam curing and autoclave curing.

The most characteristic effect of using the cement additive according to the present invention is that the fluidity of concrete can be maintained constant, and simply by adding the additive according to the present invention to concrete. This is the first disclosure of the present invention that fluidity can be maintained constant.

As mentioned above, it is possible to impart such characteristic performance to concrete within a very limited range of NS and PVA.

In fluidized concrete, in order to fluidize the base concrete and maintain a constant slump after fluidization, P.
Add and use NS in an amount equivalent to or more than VA, and use NS in an amount more than equivalent to PvA, that is, N that does not form a complex with PVA.
This is possible by increasing the fluidity with S and by releasing NS in a sustained manner through dissociation of the complex.

In this way, it becomes possible to maintain fluidized concrete within the optimal fluidity range most suitable for concrete construction.

Since the present invention makes it possible to maintain constant fluidity of concrete, the cement additive according to the present invention is specifically used for various purposes.

For example, it is used as a pumping aid. Cement mixtures are increasingly being poured by pumping, but as mentioned above, if pumping is temporarily interrupted due to a mechanical failure, etc.
If the interruption time is prolonged, the fluidity of the concrete in the pressure-feeding piping decreases, leading to problems such as a sudden increase in the pressure when pressure-feeding is resumed or blockages.

However, when the cement additive according to the present invention is added, the fluidity of concrete is kept constant, preventing a decrease in fluidity, and it is possible to prevent the pumping pressure from increasing when pumping is resumed after pumping is interrupted. This makes it possible to significantly improve the efficiency of pumping work.

As another example, it can be used as a centrifugal compaction aid.

The centrifugal compaction molding method is a method of molding and manufacturing cement-containing materials such as mortar, concrete, and asbestos-cement mixtures by using centrifugal force caused by rotation. If concrete is compacted using centrifugal force, the fluidity of the concrete before forming can be maintained for a long time, making it easier to finish the product, and is also effective in preventing slag and clarifying wastewater.

Further examples include cement milk or mortar grafting aids, cement mixtures cast with tremie pipes, underwater concrete, concrete for continuous underground walls, etc. to maintain fluidity and prevent material separation. It is also effective for

As described in detail above, the concrete industry has been seeking a method for preventing slump loss in concrete for many years, but the present invention has made it possible to solve this problem for the first time.Example 1 Degree of Condensation Using four types of calcium salts of naphthalene sulfonic acid formaldehyde high condensates with different degrees of polymerization and four types of PVA with different degrees of polymerization, we confirmed the formation of complexes and investigated the effect of preventing a decrease in concrete fluidity.

The materials used were naphthalene sulfonic acid formaldehyde high condensate calcium salt; the viscosity of a 10% aqueous solution at 30° C. (measured with an Ubbelohde viscometer) was 1.0 cps.

Four types of condensates showing 1.1 cps, 1.22 cps, and 1.30 cps Polyvinyl alcohol: Four types of polymers with a degree of saponification of about 98 mol% and a degree of polymerization of 300.500.1700.2400 Cement: Ordinary Portland cement Fine aggregate: Kino usage (specific gravity = 2.58. Coarse particle ratio - 2.76
) Coarse aggregate: Hidaka usage (specific gravity = 2.61. Coarse particle ratio = 6.6
7) Admixture: Air entrainment agent.

Table 1 shows the concrete formulation.

Concrete (10
01 concrete was mixed for 2 minutes using a tilting mixer), a 40% aqueous solution of naphthalene sulfonic acid formaldehyde high condensate calcium salt and a 5% aqueous solution of polyvinyl alcohol were mixed so that the molar ratio of polymer units was 1:1. 0.5% by weight of the 16 types of blended mixture based on the amount of cement
(NS:PVA=100:18 weight ratio) was kneaded for 1 minute.

From now on, the slump value of concrete is calculated every 15 minutes according to JIS
Measured according to A 1101.

During this time, the concrete is rotated 4 times per minute by an agitator.
I kept it inside.

Also, 10% aqueous solution of naphthalene sulfonic acid formaldehyde condensate calcium salt and 2% polyvinyl alcohol.
The aqueous solution was mixed so that the molar ratio of polymerized units was 1:1, and then diluted to 100%, and the formation of a complex was visually observed.

The measurement results are shown in Table-2.

From the measurement results, experimental ml, 2, 3, 4, 5, 6°9.10
, 13, and 14, no complex formation was observed, and the slump value of the concrete increased immediately after addition, and thereafter slump loss occurred with time.

From this result, it is inferred that the slump loss occurred because NS acted as a fluidizing agent immediately after addition and no complex was formed, so there was no NS to be released gradually.

On the other hand, complex formation was confirmed in the formulations of Experiment Arashi 7, 8, 11, 12, 15, and 16, and experiment A7,
In samples No. 8, No. 11, and No. 12, the slump value of the concrete could be maintained within a certain range for 60 minutes, and the effect of preventing slump loss was confirmed.

However, in Experiments &15 and 16, although the formation of complexes was observed, the degree of condensation of NS was too high, so it was presumed that the dissociation of the complexes was insufficient, and no slump loss prevention effect was observed.

Based on the above experimental results, the present invention is applicable.

It is presumed that the slump loss prevention effect of cement additives is brought about by the sustained release of NS due to the dissociation of complexes, and the critical chain length (critical chain length) required for complex formation, that is, the specific number of reactions. Requires group involvement.

Example 2 The effect of preventing cement additives on fluidity in fluid concrete by varying the mixing ratio of NS and PVA was investigated.

The materials used, the concrete preparation, and the experimental method were the same as in Example 1.

In Experiment 51, only NS was added.

Experiment A2 added only PVA.

Experiment A3 was a comparative example in which the blending ratio of NS and PVA was 100:3.75.

Experiment No. 54 was a comparative example in which the mixing ratio of NS and PvA was 100:37.5.

Experimental Arashi 5t A 6 is a product of the present invention.

Table 3 shows the slump and air amount measurement results.

From the measurement results, when only NS shown in Experiment 51 was added,
Immediately after addition, slump increases, and thereafter slump loss occurs with time.

Also, the amount of air decreases significantly.

When only PVA shown in Experiment A2 is added, slump loss occurs immediately after addition.

Also, the amount of air increases slightly.

In Experiment A3, slump increased immediately after addition, and thereafter slump loss occurred with time, and no effect on preventing fluidity reduction was observed.

This is considered to be because the amount of PVA is as low as 3.75 parts by weight relative to 100 parts by weight of N5, and the effect of preventing a decrease in fluidity is not recognized.

However, the slump increasing effect immediately after addition is significant.

In experiment A4, the amount of PVA was 37.5 parts by weight for 100 parts by weight of N5.
Excess PVA, which is as high as 5 parts by weight, causes cement particles to aggregate, and slump starts to decrease immediately after addition, and no effect on preventing fluidity decrease is observed.

The concrete to which the products of the present invention were added as shown in Experiments A5 and 56 maintained the slump within a certain range for 60 minutes after fluidization, and the air content was maintained at approximately the same value as the air content before addition.

From the results of this experiment, it can be seen that the excellent effects of the present invention are exhibited only when the NS and PVA of the present invention are mixed in a specific ratio.

Example 3 The effect as a pumping aid in the pumping of concrete was investigated.

Lightweight concrete with the mixture shown in Table 4 was pumped to the 8th floor (pumping height 26.6 m) using a pump truck (Mitsubishi DC90, horizontal single-acting double-row hydraulic piston type, discharge roller diameter finch). The discharge pressure (piston front pressure) and concrete quality were measured.

The materials used for concrete are as follows.

Cement: Ordinary Portland cement Fine aggregate: Produced in Hibi, Okayama Prefecture (specific gravity = 2.51. Coarse particle ratio -2,
51) Coarse aggregate 2 Artificial lightweight aggregate Mesalite (specific gravity = 1.26゜ Coarse particle ratio - 6.41) Admixture: Air-entraining water reducer Cement additive (product of the present invention): Naphthalene sulfonic acid formaldehyde high condensate Sodium salt (30℃, 10%
Aqueous solution, viscosity 1.18 cps) and polyvinyl alcohol (degree of polymerization 2,400).

6 m of concrete of the same composition with a blending weight ratio of 100:18 (Saponification degree: 98 mol%) was transported to the pouring site using a ready-mixed concrete truck.Transportation time: 1 = 35 minutes.

A2-33 minutes) Immediately before pumping, in the experiment A2, the product of the present invention was added in an amount of 0.5% by weight based on the amount of cement, and the ready-mixed concrete truck drum was rotated at high speed for 30 seconds to stir.

The pump pumping amount was set at 45 m3/hr, and the pump was first pumped 3 m' and the discharge pressure was measured.

Subsequently, after a pause of 60 minutes, the pump pressure feeding was restarted, and the discharge pressure after the pumping was restarted was measured.

We also measured the quality of concrete before and after pumping.

The results are shown in Table-5.

From the measurement results, in the general concrete used for comparison in the experiment AI, the discharge pressure decreased by 1 after stopping pump pressure for 60 minutes.
It increased by 30% from 8.4 kg/d to 24.0 kg/ffl, and the pumping performance after the pause was greatly reduced.

In addition, the slump value also decreased, and the workability and workability of pouring deteriorated.

On the other hand, in the case of the concrete to which the present invention product shown in Experiment 2 was added, the discharge pressure increased by 4.
4%, and the slump loss for 60 minutes is also slight.

In addition, there was little slump loss due to pump pressure, and extremely excellent construction and workability were maintained.

The compressive strength of the concrete was also higher than that of the comparative concrete.

Example 4 Compaction properties and prevention of slag generation as an additive for centrifugally compacted concrete were investigated.

JIS A113 concrete with the mixture shown in Table-6
The experiment was conducted according to the compressive strength test method for centrifugally compacted concrete in Section 6.

For mixing concrete, a 1001 forced mixing mixer was used, and 801 minutes of concrete materials and additives were simultaneously added and mixed for 2 minutes.

The centrifugal force specimen forming machine used was CM-25 manufactured by Maruto Seisakusho, and the dimensions of the specimen were 20 cm in outer diameter and 30 CrfL in height.

Centrifugal force compaction is performed on 27 kg of concrete immediately after mixing.
was put into the specimen, and 30 minutes after the end of the charging, centrifugal compaction was started.

The magnitude of centrifugal force and rotation time in centrifugal force compaction are 4 minutes at low speed (3, 1 g) and 2 minutes at medium speed (12, 6, 9).

High speed (35g) for 6 minutes.

(Acceleration of 1 gravity: 980 CrfL/5eC2) After completion of centrifugal compaction, the amount of slag generated was measured, and the finished state of the inner surface of the specimen was visually observed.

The mold was demolded 40 hours after molding and cured in water at 20°C, and the compressive strength at 28 days of age was determined.

The material used is the product of the present invention: naphthalene sulfonic acid formaldehyde condensate calcium salt (30°C, 10% water viscosity 1.18
cps) and PVA (polymerization degree 2400, saponification degree 98 mol%) in a weight ratio of 100:18 High performance water reducing agent: Mighty 150 (manufactured by Kao Soap ■).

(Naphthalene surfactant) Cement: Ordinary Portland cement Fine aggregate: Kinoki (Specific gravity -2.58, Coarse particle ratio -2.76
) Coarse aggregate: Takarazuka crushed stone (specific gravity -2,65, coarse grain ratio -6,7
3).

The mixture of concrete is shown in Table-6. The measurement results are shown in Table-7.

Based on the measurement results, concrete injection into the centrifugal specimen is completed 3
As a result of performing centrifugal compaction after 0 minutes, the concrete of A1 had poor compaction properties and a lot of slag (dehydrated material containing fine particles) was generated.

- The concrete of Experimental Arashi 2 with the addition of the strength wood invention showed extremely excellent compaction properties even 30 minutes after the concrete was poured into the centrifugal specimen, the amount of slag generation was reduced to about 1/2, and the compaction was high. It showed strength.

Claims (1)

[Claims] The viscosity of a 210% aqueous solution at 130°C is 1.05 to 1.
100 parts by weight of a 25 cps naphthalene sulfonic acid formaldehyde high condensate or its salt and a polymerization degree of 1000~
2700, and 4 to 20 parts by weight of polyvinyl alcohol having a degree of saponification of 70 to 99.9 mol%. 2. The cement additive according to claim 1, wherein the salt of the naphthalene sulfonic acid formaldehyde high condensate is a sodium salt. 3. The cement additive according to claim 1, wherein the salt of the naphthalene sulfonic acid formaldehyde high condensate is a calcium salt. 4. The cement additive according to any one of claims 1 to 3, wherein 70 to 450 g of polyvinyl alcohol is used per 1 m3 of concrete.