JPH075341B2 - Cement-based cured product manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a hardened cementitious material used as a flooring material, a wall material, or another building material.

(Conventional technology and its problems) Conventionally, cement-based hardened materials used for flooring materials have been reduced in weight for the purpose of improving their handleability, and foamed cement is used as the method. In addition, foamed lightweight aggregates such as pearlite and shirasu balloon are mixed in cement.

However, according to such a means, pores and aggregates of several tens of μ or more formed by foaming on the surface of the cement-based hardened body are exposed and the surface becomes rough, and adhesion suitability with other materials and coating suitability There is a problem such as deterioration.

In addition, if a resin such as SBR is mixed into the cement-based hardened material for the purpose of improving the surface property and cutting suitability, the fire resistance is lowered, and therefore a large amount cannot be mixed.

Therefore, the inventors of the present application focused on a clay mineral having a layered structure having an appropriate amount of minute voids, mixed this layered structure clay mineral into a cement-based hardened body, and molded and hardened it into a plate to obtain a fire resistance. Although it was possible to reduce the weight and the cutting workability without damaging it, it was found that a large number of cracks were generated in the cement-based hardened body.

Such a crack, when the layered structure clay mineral is kneaded with water, swells once with the water that has entered between the layers,
Then, it is presumed that, as a result of the shrinkage of the cement and the clay minerals and the layer of the clay separating from each other due to the original shrinkage in the curing and drying step, large irregular voids were continuously generated.

Further, as such a material, for example, Japanese Patent Application Laid-Open No. 58-32046
The one shown in the publication is proposed. In this publication, when smashing clay as sludge, add salts of alkali silicate (= water glass: generally sodium silicate, other lithium silicate), sodium phosphate, sodium chloride, etc. Japanese Patent Application Laid-Open No. 2004-242242 discloses that a high-strength cured product can be obtained by increasing tackiness and plasticity and mixing Portland cement.

However, all the salts disclosed in this publication are compounds having a monovalent cation.

When the monovalent cations as described above are mixed in the clay mineral as an aqueous solution, the swelling action between the layers of the clay mineral is large, and when the cement is mixed and dried, the cement is largely contracted, and the hardened cement body is cracked to form a homogeneous molded body. There was a drawback that you could not get.

This is because the cation of the salt is monovalent, and the cohesive action between the layers of the swollen clay mineral is small, so that when the cement undergoes a hardening reaction in the swollen state and undergoes dry contraction, This is probably because the blocking effect is unlikely to occur, and as a result, the hardened cement product causes a large number of cracks.

The present invention has been made in view of such problems,
Provided is a method for producing a cement-based hardened product, which has excellent surface properties and cutting workability, and is intended to disperse a large number of fine voids in the hardened cement product in order to reduce the weight without impairing the fire resistance. To do.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the method for producing a cement-based hardened product of the present invention comprises the steps of adding an aqueous solution of a salt having a divalent or higher cation such as calcium chloride or magnesium chloride. , Kaolinite, sepiolite, mica, and other layered structured clay minerals are mixed, and various cements and cementitious hardening substances such as calcium silicate are kneaded and then hardened.

(Function) When a layered structure clay mineral is mixed in an aqueous solution of a salt having divalent or more cations, the aqueous solution infiltrated between the clay mineral layers causes the clay mineral to swell and exchangeable cations of the clay mineral and cations of the salt. And the cations of the salt enter between the clay mineral layers, and the once swollen clay mineral causes a cohesive action.

In that state, when the cement-based hardening substance is kneaded into the above mixture, the cement-based hardening substance has a large particle size of 40 to 80 μ, so it does not penetrate into the clay mineral layer of 1 μ or less, but it is generated from the cement-based hardening substance. Due to the action of alkali, the cations having a valence of 2 or more in the salt between the clay mineral layers are fixed. As a result, even if the once swollen and agglomerated clay mineral is dried, the salt that enters between the layers exerts a blocking effect and suppresses the shrinkage of the clay mineral, and the cement-based hardening substance and the layered structure clay mineral and the cement-based hardening The substances are hardened by the hydration reaction of the cement-based hardening substance while having minute voids, and are bonded uniformly and firmly.

EXAMPLES Examples of the present invention will be described. First, a salt having a divalent or higher cation is dissolved in water to prepare an aqueous solution, and a layered structure clay mineral is added to the aqueous solution to form a paste or slurry. A mixture is obtained.

The amount of salt mixed is 1 with respect to 100% by weight of the layered structure clay mineral.
It is preferably in the range of up to 40% by weight, and it is not preferable to add more than this amount, because it will be liberated.

As the salt, various salts having divalent or higher cations such as aluminum sulfate, nickel nitrate, magnesium chloride and calcium chloride can be used. Among these salts, deliquescent of calcium chloride, magnesium chloride and the like can be used. When a substance having a high strength is used, the obtained cement-based cured product itself has moisture absorption and desorption properties and can be used as a humidity control material.

Examples of the layered structure clay minerals added to the aqueous solution of this salt include kaolinite, allophane, sepiolite, montmorillonite, mica, vermiculite, and the like. Good.

As described above, when the layered structure clay mineral is mixed into the aqueous solution of the salt having a cation having a valence of 2 or more, the once swollen clay mineral is exchanged with the exchangeable cation between the clay mineral layers and the cation of the salt. The cations having a valence of 2 or more are aggregated in a state of entering between the clay mineral layers, and are fixed by the action of the alkali of the cement-based hardening substance to be added next, so that the shrinkage of the layered structure clay mineral due to drying is suppressed.

Then, the cement-based hardening substance is kneaded with the paste-like or slurry-like mixture at a compounding ratio of 10 to 300% by weight with respect to 100% by weight of the layered structure clay mineral.

As the cement-based hardening material, various cements, calcium silicate, blast furnace slag, gypsum slag, lime and the like as a main component or a complex are used.

In addition, to this cement-based hardening material, silica, sand, aggregates such as cold water stones and asbestos, synthetic fibers, reinforcing fibers such as metal fibers, and other additives such as various synthetic resins, water reducing agents, and foaming agents, It may be added to the extent that the fire resistance and heat resistance of the obtained cement-based cured product are not impaired.

When a cement-based hardening material is kneaded into a mixture of the aqueous salt solution and the layered structure clay mineral, the cement-based hardening material has a large particle size of 40 to 80 μ, so that it does not penetrate between the clay mineral layers of 1 μ or less, Due to the action of the alkali generated from the cement-based hardening substance, the cations having two or more valences in the salt between the clay mineral layers are fixed. As a result, even if the swelled and agglomerated clay mineral is dried, the salt that enters between the layers exerts a blocking effect, suppressing the shrinkage of the clay mineral, and hardening cement and layered structure clay mineral and cement The hardened substances are hardened by the hydration reaction of the cementitious hardened substance and are uniformly and firmly bonded to each other, whereby a cement-based hardened product having innumerable fine voids and having a smooth surface without cracks can be obtained.

The reason why such a cement-based hardened body is obtained will be described with reference to FIG. 1. When the layered structured clay mineral is mixed in an aqueous solution of a salt having a divalent or higher cation, the layered structured clay mineral swells. Then, the salt (2) which has aggregated and entered between the clay mineral layers (1) and (1) by the ionic reaction of the exchangeable cation between the layered structure clay mineral and the divalent or higher cation of the salt is It is fixed by the alkali of the added cement and exerts a blocking effect to suppress the shrinkage of the clay mineral layer (1). As a result, between the cement (3) and the clay mineral layer (1) and between the cement (3) and the cement ( This is probably because the bond between 3) becomes strong.

Further, the voids between the clay mineral layers can be formed into a plate-like object with almost no damage, and a porous cement-based hardened product having innumerable fine pores due to the voids can be obtained.

In the production process of such a cement-based hardened product, the amount of water can be adjusted by adding a layered structure clay mineral to an aqueous solution of a salt to obtain a paste or a slurry-like mixture, and a cement-based hardened substance. May be mixed with water in advance and kneaded with a mixture of the aqueous solution of the salt and the layered structure clay mineral, in short, kneading with water necessary for finally hardening the cement-based hardening substance. Then
The water content may be adjusted within a range that facilitates the molding and drying steps.

Next, specific examples and comparative examples of the present invention will be shown.

Example 700 g of bentonite was kneaded with an aqueous solution of calcium chloride obtained by adding 35 g of calcium chloride to 500 g of water and left for 1 hour, and then 350 g of ordinary Portland cement was kneaded to form a plate, dried and cured. A cement-based cured product was produced.

Comparative Example In the above-mentioned example, a cemented hardened product having the same shape was produced without using calcium chloride but with the same other composition.

In the above-mentioned Example and Comparative Example, the specific gravity in the Example is 1.1,
A plate-like material having a fine surface with a specific surface area of 45 m ² / g (measured by the BET method) was obtained, but in the comparative example, it was brittle and many cracks were generated, and a satisfactory plate-like material was not obtained.

In addition, for the plate-like material (50 x 50 x 50 mm) obtained in the example
When a plane tensile test according to JIS A5908 was performed, the strength showed a value of 3 to 5 kg / cm ² , and this value is the conventional specific gravity.
It is equivalent to a cement-based plate material of 1.5 or more, and has practically no hindrance.

Further, the distribution of the pore diameters of the plate-shaped materials of the examples was measured by the mercury porosimetry, and as shown in FIG. 2, the pores of the cement having a small pore diameter shown by the solid line (a) and the dotted lines (b) are shown. The peak of the pore volume with the pores due to the bentonite with a large pore size is deviated, and the weight of the cement-based hardened body is reduced as much as it is biased toward the bentonite with a large pore size as a whole. Both have good machinability.

On the other hand, in the comparative example, the peak of the pore diameter appears at several tens of μ, and it seems that there are gaps caused by the shrinkage of the layered structure clay mineral, which is the cause of cracks and weakening. I think that the.

Next, regarding the moisture absorptive and desorptive properties of the examples, there is a weight increase of 2000 g / m ² when left in an environment of 20 ° C. and 90% RH for 1 week, which is 4 to 6 times that of commercially available humidity conditioners such as wood. Shows the moisture absorption capacity of
It was also found to be used as an effective humidity control material.

(Effects of the Invention) As described above, the present invention is characterized in that a layered structure clay mineral is mixed in an aqueous solution of a salt having divalent or higher cations, and a cement-based hardening substance is kneaded into the mixture and then cured. Since it relates to the method for producing a cement-based hardened product, the exchangeable cation between the layers of the clay mineral swollen by water and the divalent or higher cation of the salt are ion-exchanged and aggregated, and the cement-based hardening is also performed. Cracks in which clay minerals, cement, and cements are firmly bound to each other, by which the action of alkali of the substance fixes the cations of divalent or higher valent salt in the clay mineral layer and exerts a blocking effect, thereby suppressing the shrinkage of clay minerals It is possible to obtain a cement-based hardened product that does not cause aging, and is light in weight because of the large number of fine voids of layered structure clay mineral dispersed inside, and with excellent cuttability and handleability. A cured product can be produced, and since the voids exposed on the surface are small, a finely textured surface does not impair the adhesiveness and coating suitability.

In addition, since the main component of this cement-based hardened material is an inorganic material, it has fireproofness, and when a deliquescent salt is used, it has humidity control properties, so it exhibits excellent effects as various building materials. is there.

[Brief description of drawings]

The drawings show examples of the present invention. FIG. 1 is a simplified structural diagram of a cement-based hardened product, and FIG. 2 is a pore diameter distribution diagram. (1) …… Clay mineral layer, (2) …… Salt, (3) …… Cement.

Claims (1)

[Claims] 1. A method for producing a hardened cementitious body, which comprises mixing a layered structure clay mineral in an aqueous solution of a salt having a cation having a valence of 2 or more, kneading a cementitious hardening substance into the mixture, and then hardening the mixture. Method.