JPH02133356A - Lightweight extruded cement building material - Google Patents

Abstract

PURPOSE:To provide the extruded cement building material which has closed cells in the matrix, is light in weight and has excellent freezing resistance by compounding a water absorptive polymer which has water absorbability of >=20 times the water absorbability of cement under the strong alkalinity of the cement and exhibit a granular state in a water absorbing state with the cement. CONSTITUTION:The water absorptive polymer (e.g., 'Sumicagel S type(R)' produced by Sumitomo Chemical) which has >=20 times the water absorbability of the cement under the strong alkalinity of 12 to 13pH and maintains the granular state in a water absorbing state is mixed at 0.1 to 5wt.% with an admixture composed of a hydraulic binder, such as Portland cement, aggregate, such as silica sand powder, flyash, and pearlite, heat resistant inorg. or org. fibers, thickener, etc., and the mixture is kneaded and extrusion-molded. The molding is thereafter cured in an autoclave at >=120 deg.C, more preferably >=150 deg.C by which the lightweight extruded cement building material having the closed cells is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ceramic-based lightweight extruded cement building material, that is, a lightweight concrete building material.

(Prior Art) Lightweight cement building materials are materials made by reducing the weight of hardened cement, and have excellent properties such as lightness, heat insulation, nonflammability, and fire resistance. It is widely used today as a building material.

The following methods can be used to reduce the weight of conventional ceramic-based extruded cement building materials.

■Methods that use inorganic lightweight aggregates such as perlite and shirasu balloons, ■Methods that use organic foamed lightweight aggregates such as styrene beads, ■Methods that use surfactant-based, protein-based, etc. A method of introducing air bubbles into the cement matrix using a foaming agent; ■ A gel-like substance obtained by hydrothermally reacting silicic acid raw materials and calcium raw materials in the presence of water is mixed into cement material, molded, and then autoclaved for curing. Boat fishing is a method of reducing weight by dissipating gel water in a gel-like substance by drying or drying.

In this way, weight reduction can be broadly divided into methods that use organic and inorganic lightweight aggregates, methods that use foamed materials, and methods that perform dehydration during the curing process.

When extrusion molding is used as a molding method, the material is kneaded to a certain degree of hardness to prevent the surface of the mold after molding, and is also pressurized during molding, which consolidates the material and makes it difficult to reduce weight. is required.

Experiments conducted by the present inventors have revealed that extruded cement building materials having closed pores in the matrix, such as those made of shirasu balloons or expanded styrene beads, have excellent freeze resistance.

However, since inorganic lightweight aggregates such as shirasu balloons are destroyed during extrusion molding, there is a limit to weight reduction. In addition, foamed organic lightweight aggregates such as styrene beads are compressed during extrusion and return to the original volume after extrusion, resulting in poor surface conditions of the extruded material.

Therefore, a method of using a foaming agent may be considered, but if one blower is used, the extrusion material is a hard kneading material, so defoaming is easy during mixing and kneading, and defoaming also progresses during extrusion molding. Therefore, the effect on weight reduction is small. Furthermore, since calcium silicate gel-like substances contain a large amount of water, when applied to hard kneaded materials such as extruded materials, they must be dehydrated to some extent, which complicates the manufacturing process.

As described above, the weight reduction of extruded products has several unique problems that are not seen in cast molded products.

In terms of weight reduction, a lightweight inorganic extrusion product has been proposed that uses a combination of amorphous silica, which is produced as a by-product during glass production, and a water-absorbing polymer (Japanese Patent Laid-Open No. 167267/1982). In this proposal, weight reduction can be achieved mainly by using amorphous silica, but since amorphous silica alone causes a decrease in freeze resistance and nailing performance, a water-absorbing polymer is used in combination to compensate for this.

Types of water-absorbing polymers in this case include polyacrylate-based, starch-based, polyvinyl alcohol-based, etc., and it is said that polyacrylate-based polymers are preferable. However, the water-absorbing polymer becomes gel-like when it absorbs water, and the water-absorbing polymer shown in the examples of the above-mentioned publication also becomes gel-like when it absorbs water.

By the way, when the above-mentioned water-absorbing polymer, which becomes gel-like when it absorbs water, comes into contact with a strong alkali such as cement, a remarkable drainage phenomenon is observed from the water-absorbing polymer. As a result, the amount of water retained in the polymer becomes extremely small, making it impossible to achieve weight reduction for reasons described below. On the other hand, in order to increase the amount of water retained, a large amount of polymer must be added, which causes problems such as hardening of the cement.

Therefore, in the past, instead of adding such a water-absorbed polymer to a cement material, a method has been used in which the polymer before water absorption is triblended with cement, and then kneaded water is added to finalize the mixture. However, even with this method, the water absorption capacity is less than 1/100 of that of pure water,
It is difficult to retain large amounts of water in cement matrix. Furthermore, by employing extrusion molding, even a small amount of absorbed water may be leached out under pressure during molding, making it impossible to achieve sufficient weight reduction.

However, if the above-mentioned water-absorbing polymer is used, a large number of continuous open pores will be present in the cement matrix, so the inventor's experiments did not necessarily show sufficient freeze resistance.

As already mentioned, several methods have been considered to reduce weight. However, until now there has not been a sufficient means for reducing the weight of extruded products.

(Problems to be Solved by the Invention) An object of the present invention is to provide an excellent lightweight extruded cement building material that eliminates the drawbacks of the prior art.
It is.

Furthermore, a specific object of the present invention is to provide a lightweight cement building material that is lightweight and has excellent freeze resistance.

(Means for Solving the Problems) In order to improve the above-mentioned drawbacks, the inventors of the present invention focused on the possibility of making light oil by using water-absorbing polymers and conducted various studies. We learned that by using a water-absorbing polymer that has the above water-absorbing ability and maintains its granular form in the water-absorbing state, extruded cement building materials with excellent freeze resistance can be obtained using light oil and having independent pores in the 7 trisox. The invention has been completed.

In other words, extruded materials using water-absorbing polymers that have a water-absorbing capacity of 20 times or more even under strong alkaline conditions such as cement and maintain their granular form in a water-absorbing state will drain some of the water from the polymer during extrusion molding. Therefore, it was revealed that the moldability was improved, and although some of the polymer was fragmented by the extrusion pressure, many independent pores remained in the matrix after extrusion molding. It has also been found that by using the water-absorbing polymer according to the present invention, the amount of thickener required for extrusion molding can be reduced.

Here, the gist of the present invention is to combine a hydraulic binder, one or more types of aggregate, one or more types of admixtures, and a cement that has a water absorption capacity of 20 times or more even under strong alkali conditions. 0 of mixed pure water that maintains granularity in water absorption state
．． This is a lightweight extruded cement building material with closed pores obtained by extrusion molding a material mixed and kneaded with 1 to 5% by weight of water-absorbing polymer particles and then curing in an autoclave.

In addition, in the hardened cement body according to the present invention, the higher the autoclave curing temperature of the extrusion molded material, the lower the water absorption rate of the hardened cement body and the better the freeze resistance.

(Function) Next, the reason why the structure of the present invention is limited as described above will be explained in detail below.

The water-absorbing polymer particles used have a water absorption capacity of 20 times or more even under strong alkaline conditions with a pH of 12 to 13, and maintain a granular shape even in a water-absorbed state. For example, a water-absorbing polymer that has the chemical composition of acrylic acid/vinyl alcohol copolymer and maintains its granular shape even when water is absorbed (Sumikagel S manufactured by Sumitomo Chemical Co., Ltd.)
type) is preferred.

The particle size of the water-absorbing particles is not particularly limited, but generally about 0.1 to 0.5 mm is sufficient.

The reason why the water absorption capacity is set to 20 times or more is because if it is less than this, the effect of weight reduction becomes small.

The water-absorbing polymer used in the present invention may be used after being sufficiently swollen in part or all of mixed pure water, or may be tri-blended into cement or aggregate. However, extrusion moldability tends to be more stable if the material is swollen in kneading water before use.

As shown in Figure 1, when polymer particles pre-swollen with distilled water are immersed in cement supernatant liquid, the water is drained over time and the water absorption capacity gradually decreases to a constant value, and the polymer particles are immersed in cement supernatant liquid as they are. When immersed in water, it absorbs water over time and the water absorption capacity gradually increases to a certain value. It takes 40 to 60 minutes for the water absorption capacity to become constant in &.

Therefore, an extruded material mixed with pre-swollen polymer gradually drains water even during extrusion molding, while an extruded material made by tri-blending polymer particles with cement and aggregate and kneading with water gradually drains water during extrusion molding. will absorb water.

By the way, extruded materials require several tens of minutes to be molded after being kneaded, and the temperature of the material increases as a result of applying a large shear force to the material and kneading it to ensure uniform mixing. Water escapes, and if this is significant, the material may become clogged inside the die, making stable extrusion molding impossible. Therefore, if water is absorbed in the material during extrusion molding, the extrusion molding becomes even more unstable, so it is rather advantageous from the viewpoint of moldability to drain water during extrusion molding to compensate for the water that has escaped. . In addition, the water absorption capacity that becomes constant in the cement supernatant liquid is higher in the case of pre-swollen particles than in the case of using raw particles, so the weight reduction effect is greater when using pre-swollen polymers.

The amount of water-absorbing polymer used should be 0.1 to 0.1 of the amount of mixed pure water.
The reason why it is set at 5 wt% is that if it is less than 0.1 wt%, the weight reduction effect will be small, and if it exceeds 5 wt%, there is a possibility that the hardening reaction of cement will be inhibited.

Common hydraulic binders include early-strength Portland cement, ordinary Portland cement, blast furnace cement, and granulated blast furnace slag. Furthermore, the water absorption capacity of the water-absorbing polymer used in the present invention decreases as the alkalinity increases, so when GRC cement with low alkalinity is used, the pore size in the matrix becomes large and the weight reduction effect becomes large.

The aggregate is generally a finely powdered aggregate such as silica sand powder, fly ash, silica clay, or silica hume, but the type thereof is not limited. In addition, it is possible to further reduce the weight by using inorganic lightweight aggregates such as perlite and shirasu balloons, mechanical lightweight aggregates such as expanded styrene beads, and calcium silicate gel aggregates that can be reduced in weight by odocrape curing. is possible. These aggregates can be used alone or in combination.

In addition, in the present invention, one or more types of admixtures are blended, and such admixtures include organic or inorganic fibers having 1li4 thermal properties, thickeners, and the like.

These heat-resistant organic and inorganic fibers can be used as long as they can withstand autoclave curing at 120°C or higher, such as carbon fibers, polyprofibers, aramid fibers,
There are pulps, etc.

As a thickener, tJ thickener represented by methyl cellulose is used.
In addition to i-materials, AE agents, high-performance water reducing agents, etc. can be used.

The raw materials blended in this way are then mixed and kneaded, and after being mixed and kneaded, they are extruded.

At that time, if the extrusion pressure is high, some polymers tend to become finer, but since they hardly dehydrate even under pressure, this hardly impedes weight reduction.

The autoclave curing after extrusion molding may be carried out at a temperature of 120'C or higher, but preferably at a temperature of 150'C or higher, which is advantageous in terms of improving the freeze resistance of the hardened cement product.

This is because the water-absorbing polymer deteriorates due to heat as the temperature rises, so the water-absorbing ability after autoclave curing decreases, and even if water is supplied and the water-absorbing polymer swells again, it cannot return to its original volume and the water freezes and expands. However, since there is a volume for expansion, the expansion pressure does not directly act on the cement matrix, resulting in improved freeze resistance.

Note that depending on the autoclave curing conditions, the water in the polymer may not be sufficiently dissipated.

In this case, after curing in an autoclave, it may be dried at a temperature of 100° C. or lower.

Next, the effects of the present invention will be explained in more detail with reference to Examples.

Example In this example, a water-absorbing polymer with a chemical composition of acrylic acid and vinyl alcohol copolymer (Sumitomo Chemical Co., Ltd. (Kema Sumikagal S type) was used. The average particle size of the raw material was 227 μm, and the average water absorption capacity when distilled water was absorbed was 670 times.

For comparison, Aqua Keep 1081 manufactured by Seitetsu Kagaku Co., Ltd. is used as a conventional water-absorbing polymer that becomes gel-like when it absorbs water.
One type of water-absorbing polymer was also used.

All of these were sufficiently water-absorbed in kneading water before use. The cement used was ordinary Portland cement, the aggregate used was T5) unsilica sand, the pulp used as the heat-resistant organic fiber was NBKP (softwood bleached kraft high), and methylcellulose was used as the thickener.

Here, the attached drawing shows a graph of the water absorption capacity when an absorbent polymer that has previously absorbed distilled water and original polymer particles that have not absorbed water are immersed in a cement supernatant liquid. As a result, it was found that the water-absorbing polymer, which maintains its granular shape even after absorbing water, has a water absorption capacity of approximately 100 times even after 60 minutes have passed, even when it comes into contact with the strong alkali of cement during kneading.

Table 1 shows the blending conditions of these raw materials. Here, Comparative Example 1 is a formulation that does not use a water-absorbing polymer, and Comparative Examples 2 and 3 are formulations that do not use a water-absorbing polymer. This is a formulation in which 0.7 wL% of the kneading water is added.

In Example 1, good extrusion molding was possible because the material had appropriate fluidity.

From these facts, it can be seen that when applying the water-absorbing polymer used in the present invention to a formulation that can be extruded, it is necessary to add mixed pure water to ensure the fluidity necessary for extrusion molding. . On the other hand, in Comparative Example 3, which used a water-absorbing polymer that becomes gel-like when water is absorbed, almost all of the absorbed water was drained when mixed with cement, so the fluidity of the material after kneading was lower than that of the comparative example. 1, extrusion molding was possible. However, the absolute dry specific gravity was comparable to that of Comparative Example 1, and it became clear that there was almost no weight reduction effect. In addition, in Comparative Example 3, in which a water-absorbing polymer that becomes gel-like when absorbed is used in place of the water-absorbing polymer used in the present invention with the same formulation as in Example 1, the water absorbed during mixing with cement was removed. Since almost all of the water had been drained, more water than necessary entered the matrix and the material became too soft, making extrusion molding impossible. In Example 3, the water-absorbing polymer was added in an amount of 2 wt% of the kneading water, and the absolute dry specific gravity was smaller than in Example 1, in which the amount of the water-absorbing polymer added was 0.7 wt%. However, the water absorbing polymer is mixed with 6W of water.
In Comparative Example 4 in which t% was added, the polymer inhibited the cement hardening reaction, so the bending strength was reduced.

In addition, in Comparative Example \4 and Example 3, the amount of water-absorbing polymer added to water is large, so 60 parts by weight of the 140 parts by weight of the kneading water is absorbed by the water-absorbing polymer, and the remaining 80 parts by weight is added to the cement material. After kneading, the water-absorbed polymer was finally added and the mixture was extruded.

Autoclave curing was performed on the second day after extrusion molding. Here, in Example 1.2 where the blending conditions are the same but the autoclave curing temperature is different, Example 2 where the autoclave curing temperature is high.
had better freeze resistance.

Furthermore, among those that could be extruded, all those using the water-absorbing polymer of the present invention that maintains a granular shape in a water-absorbed state were observed to have independent pores in the matrix. Furthermore, the direct nail driving performance was also satisfactory.

(Effects of the Invention) As described in detail above, according to the present invention, a water-absorbing polymer that has a water-absorbing capacity of 20 times or more even under strong alkaline conditions of cement and maintains its granular form in a water-absorbing state can be used in cement extrusion materials. A lightweight building material with independent pores and excellent freeze resistance was obtained.

[Brief explanation of drawings]

The attached drawing is a graph showing the relationship between the soaking time into the cement supernatant liquid and the water absorption capacity for water-absorbing polymer particles that have previously absorbed residual water and the same raw polymer particles.

Claims (1)

[Claims] A hydraulic binder, one or more types of aggregate, one or more types of admixtures, and a kneaded water that has a water absorption capacity of 20 times or more than cement and maintains granular form in a water absorption state even under strong alkali conditions. A lightweight extruded cement building material having closed pores obtained by extrusion molding a material mixed and kneaded with water-absorbing polymer particles in an amount of 0.1 to 5% by weight and then curing in an autoclave.