JPH0280385A - Admixture for cement concrete and mortar using high-water-absorption resin - Google Patents

Abstract

PURPOSE:To prevent bleeding and a decrease in the compressive strength by using a composition obtained by coating the surface of a water-absorptive resin with a hydrophobic material as the admixture, and thereby preventing the water absorption during the kneading of the cement composition or during the conveyance of the kneaded material. CONSTITUTION:The surface of a water-absorptive resin (the fine powder having >=10g/g, or preferably >=30g/g, absorption for alkaline water at pH12.5 and <=150mu mean particle diameter is preterably used) is coated with a hydrophobic material to obtain a composition to be used as an admixture for cement concrete and mortar. From 0.5 to 280 pts.wt., or preferably 0.5-200 pts.wt., of the coating material is preferably used with 100 pts.wt. of the water-absorptive material, and the thickness of the coating layer is controlled to 0.005-1mm, or preferably to 0.1-0.5mm. The 'Sunwet 1M-1000MPS(R)' (starch-acrylate cross- linked graft copolymer) of the SANYO KASEI Co. is used as the water- absorptive resin, and the synthetic resin such as polystyrene, long-chain fatty acid, rubber, etc., as the hydrophobic material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to cement concrete and mortar admixtures. More specifically, the present invention relates to an admixture material comprising a water-absorbing composition in which the time from contact with water to when it substantially starts absorbing water is controlled.

[Prior Art] A cement composition consists of cement, fine aggregate, coarse aggregate, and other cement-added materials as necessary, and the hardening phenomenon of this cement composition is due to a chemical hydration reaction between cement and water. It is. Generally, the strength of concrete obtained through a hydration reaction increases as the water/cement ratio decreases. However, concrete (especially in the case of ready-mixed concrete)
Currently, the amount of water per unit is usually increased in order to ensure workability during pouring. As a result, (l) breathing water is generated after pouring, and this breathing water forms a water film on the lower surface of horizontal reinforcing bars and coarse aggregate, which inhibits the adhesion of these with mortar; (2) breathing water As the water migrates to the upper layer, the water/cement ratio in the upper layer increases and the strength decreases, making the strength of the concrete uneven. (3) The water path created by breathing continues even after the concrete hardens. (4) Along with breathing water, inorganic substances that are not involved in the hydration reaction float on the concrete surface and deposit laitance. (5) The unit water volume is reduced for the purpose of ensuring workability. This causes various problems such as the need for more time than necessary for the concrete to set.

On the other hand, methods have been proposed in which water-absorbing resins such as polyacrylates, isobutylene-maleic acid copolymers, or saponified vinyl acetate-acrylic ester copolymers are added to cement compositions (for example, JP Showa 56-69257
No. and Japanese Unexamined Patent Publication No. 12-132747).

[Problems to be Solved by the Invention] However, since the conventional cement-added materials made of water-absorbing resins as described above start absorbing water immediately upon contact with water, especially in the case of ready-mixed concrete, cement) The saturated water absorption amount is reached during the mixing process after water is added, or between the time the mixed material is transported by a concrete mixer truck and placed at the pouring site. Therefore, since the water-absorbing resin that has already reached its saturated water absorption capacity does not exhibit any more water-absorbing power, the above-mentioned (1) to (
5) It is not possible to solve the problem.

Means for Solving Problem C] The present inventors have developed an admixture material for cement, concrete, and mortar that does not substantially start absorbing water during kneading or transportation of a mixed material by adding water to a cement composition. As a result of intensive study, we have arrived at the present invention. In other words, the present invention provides a cement/concrete and mortar admixture comprising a water-absorbing composition obtained by coating the surface of a water-absorbing resin with a substance that is hydrophobic to water; This is a mixture of cement, concrete, and mortar, which is made of a water-absorbing composition obtained by coating the surface of the mixture with a water-absorbing resin with a substance that is hydrophobic to water.

In the present invention, water includes all types of water that can be obtained artificially or naturally, such as tap water, well water, river water, rainwater, and distilled water. It also includes breathing water generated from concrete and mortar. Preferably,
In view of the situation in which the admixture of the present invention is used in cement concrete and mortar, water with a pH of 6 or more is neutral and alkaline. More preferably PH
is 10 or more alkaline water.

In the present invention, the water-absorbing composition includes: (1) a water-absorbing composition obtained by coating the surface of a water-absorbing resin with a substance that is hydrophobic to water; (2) a mixture of a thermoplastic resin and/or rubber and a water-absorbing resin; Examples include water-absorbing compositions obtained by coating the surface of the composition with the above-mentioned substance that is hydrophobic to water.

Among these, preferred ones are those that can be manufactured at low cost, have easy control of 11H at the start of water absorption (the time from contact with water until the actual start of water absorption), and have a conventional water absorbency after the start of water absorption. It is a water-absorbing composition rated ① in that it exhibits a water-absorbing rate equivalent to that of resin.

Here, the time until water absorption actually starts does not only mean that the water absorption function originally possessed by the water absorbent resin is expressed after an arbitrary period of time has passed, but also means the time until water absorption starts, that is, the water absorption It also includes the time required to reach the saturated water absorption of the composition, usually 30%, preferably about 10%. In addition, after starting water absorption, it is preferable that the water absorption rate is the same as that of a normal water absorbent resin.

In the composition (2), substances that are hydrophobic to water include hydrophobic synthetic resins (e.g., polyethylene, polypropylene, chlorinated polyethylene, polystyrene, etc.), hydrophobic natural resins (e.g., beeswax, natural waxes such as tallow, etc.), Long chain fatty acids (e.g. behenic acid, etc.), long chain alcohols (e.g. behenyl alcohol, stearyl alcohol, etc.), rubbers (e.g. bunal rubber, imprene rubber, butadiene rubber, chloroprene rubber, styrene-diene copolymer rubber, acrylonitrile-diene copolymer rubber, isobutylene) - Synthetic rubber such as isoprene copolymer rubber, natural rubber, recycled rubber, etc.
These hydrophobic substances may be used alone or in combination of two or more. Preferred among these are polyethylene, polystyrene, and beeswax.

The water-absorbing resin in the composition (2) includes starch or cellulose (a), a water-soluble monomer containing a carboxyl group and/or a sulfonic acid group, and/or a monomer (b) that becomes water-soluble upon hydrolysis. There is a water-absorbing resin obtained by polymerizing a crosslinking agent (c) and a crosslinking agent (c) as essential components, and performing hydrolysis if necessary.

Details of (aL (b) and (C), proportions of (a), (b) and (c), manufacturing method, and specific examples of water-absorbing resins used in the production of the above-mentioned water-absorbing resins are disclosed in Japanese Patent Application Laid-Open No. 52-11911) 2588
No. G, Special Publication No. 1199, Special Publication No. 1199, Special Publication No. 53-46
No. 200 and Japanese Patent Publication No. 55-21041.

Water-absorbing resins other than the above resins include those obtained by polymerizing (a) and (b), such as hydrolysates of starch-acrylonitrile graft polymers, hydrolysates of cellulose-acrylonitrile graft polymers, etc. (a) Cross-linked products such as carboxymethylcellulose cross-linked products; (
Copolymers of b) and (C), such as partially hydrolyzed crosslinked polyacrylamide, crosslinked sulfonated polystyrene, JP-A-52-14889 and JP-A-52-
Saponified products of vinyl ester-unsaturated carboxylic acid ester copolymers, crosslinked polyacrylates, crosslinked acrylic acid-acrylic acid ester copolymers, described in JP 27455,
Examples include crosslinked inbutylene-maleic anhydride copolymer and crosslinked carboxylic acid-modified polyvinyl alcohol. Further, polymers (b) having self-crosslinking properties (for example, self-crosslinking polyacrylates), crosslinked polyethylene oxide, crosslinked polyvinyl alcohol, etc. can also be used.

It is also possible to use a resin in which the above-mentioned water-absorbing resin is further surface-crosslinked with a crosslinking agent to provide a crosslinking gradient.

The water-absorbing resin has a small saturated absorption amount (log/g, preferably 30 g/g or more) for alkaline water having a pH of 12.5.

There is no particular restriction on the shape of the water-absorbing resin, and it may be in any shape such as powder, flakes, or fibers, but powder is preferable. More preferably, it is a fine powder with an average particle size of 150 μm or less.

Water-absorbing resin as an extender and filler as powder powder [e.g. cellulose derivatives, starch derivatives, pulp powder, stearate compounds, etc.]; inorganic powders (e.g. perlite, silica, bentonite, zeolite, shirasu balloon, etc.); hydrophobic It can be used in combination with synthetic fibers, etc. In addition, a surfactant, a water repellent, a crosslinking agent, etc. may be used in combination if necessary, and there is no particular limitation on the amount of these mixed, and the amount that is usually used in combination may be used.

Water-absorbing composition (1) is produced by coating, encapsulation, or the like. for example(
b) Substances that are hydrophobic to water are mixed with organic solvents (alcohol-based, ketone-based, aliphatic or aromatic hydrocarbon-based, ester-based solvents, mixed solvents thereof, or water-containing solvents, etc.) usually from 0.1 to A method of dissolving the water absorbent resin at a concentration of 30% by weight, immersing the water absorbent resin in this solution and drying it, (b) dispersing the water absorbent resin in the solution of the above substance and micro-coating it by coacervation method or flocculagelon method. encapsulation method, (c) microencapsulation method using a hybridization system, (d) method of spraying or applying the above substance solution on the surface of a water-absorbing resin and drying it, (v) water-absorbing property. A method of spraying or applying non-aqueous or aqueous emulsion of the above substance on the resin surface and drying it;
Examples include (f) a method of jet coating using a device such as a coat miser, and (g) a method of directly coating the surface of the water-absorbing resin with the above substance in a molten state and cooling it.

The water absorption start time of the water-absorbing resin composition obtained in this way can be determined by changing the type of coating substance, coating amount, film thickness, and particle size of the composition, or by adding other additives as described below. It can be controlled appropriately.

The ratio of the water-absorbing resin to the covering substance is 100% of the water-absorbing resin.
The amount of the material to be coated is usually 0.05 to 280 parts by weight, preferably 0.5 to 200 parts by weight.

The thickness of the coating layer is usually 0.005 to 111 mm on average.
Preferably it is 0.1 to 0.5 servings.

In the production of the above composition, other additives may be added as necessary, such as inorganic or organic fillers (silica, bentonite, asbestos, glass, mfiL, etc.), surfactants (sorbitan aliphatic ester, calcium stearyl lactate, etc.), and wall membranes. A forming aid (such as dimethylpolysiloxane) can be used in combination.

In the composition (2), examples of the thermoplastic resin include polyethylene, polypropylene, polyamide, ethylene-
Examples include vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, chlorinated polyethylene, chlorosulfonated polyethylene, soft polyvinyl chloride, polyurethane, and linear thermoplastic polyester resin.

The rubber may be the same as that explained in the section on hydrophobic substances.

These thermoplastic resins and/or rubbers may be used alone or in combination of two or more.

Among the above thermoplastic resins and/or rubbers, preferred are ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, chlorinated polyethylene, polyurethane, and acrylonitrile-diene copolymer rubber.

Examples of the water-absorbing resin include those similar to those mentioned above.

The blending ratio of the thermoplastic resin and/or rubber to the water-absorbing resin is usually 5 to 500 parts by weight, preferably 10 to 40 parts by weight, of the water-absorbing resin to 100 parts by weight of the thermoplastic resin.
It is 0 parts by weight.

Mixture of thermoplastic resin and/or rubber and water absorbent resin
Il [For example, as a method for producing composition (1)
A predetermined amount of thermoplastic resin and water-absorbing resin are blended, and if necessary, anti-aging agents, fillers, plasticizers, etc. II Ri properties imparting agent A method of vulcanizing a mixture of rubber, water-absorbing resin, and, if necessary, the above-mentioned additive components in a specified amount using normal amounts of rubber vulcanizing agents, vulcanization accelerators, vulcanization aids, etc. Examples include a method of molding it into a predetermined shape and size.

The mixed material of the present invention can be obtained by coating the surface of this kneaded X1 product with the above-mentioned hydrophobic substance in the same manner.

The mixed feed of the present invention includes cement and optional sagging material,
It is used by blending it into a cement composition made of the cement-added material of the pond. It can also be mixed into concrete or mortar.

Examples of cement include Portland cement [for example, ordinary Portland cement, early-strength Portland cement, moderate heat Portland cement, sulfate-resistant Portland cement, etc.; mixed cement [for example, blast furnace cement, fly ash cement].

silica cement, etc.). Other special cements such as alumina cement and white cement are also included.

As aggregates, for example, ordinary aggregates such as river sand, sea sand, gravel, crushed stone, etc.; lightweight aggregates; ultra-light aggregates; heavy aggregates; and other slag, whitebait, flyanyu, perlite, etc.
Examples include asbestos, rock wool and mixtures thereof. The amount of these compounds is usually 50-+000 parts by weight per 100 parts by weight of cement.

Other cement additive materials include water-soluble polymers [
For example, cellulose derivatives such as methylcellulose, polyvinyl alcohol, synthetic resin emulsions [e.g. EVA emulsions, vinyl acetate emulsions, etc.]
, natural or synthetic rubber latex [such as SBR latex], Yoiki sulfonic acid compounds [sodium lignin sulfonate, sodium allyl sulfonate, etc.], quick-setting agents [
For example, alkali aluminates and alkali carbonates alone or as a mixture, water glass type, carunium aluminate type quick setting agents, inorganic fibers [e.g. glass fibers, asbestos, rock wool, etc., water reducing agents, fluidizing agents, efflorescence, etc. Known additive materials such as inhibitors are used as appropriate for the purpose of improving workability, adhesion, reinforcement, etc. of the cement composition.

The blend n of these other cement additive materials may be in the amounts normally blended.

The amount of the water-absorbing polymer substance to be mixed into the cement composition can be appropriately selected depending on the type of cement, water/cement ratio, unit water amount, type and amount of aggregate, etc., but it is usually 0.01 to 20% relative to the cement. % by weight, preferably 0.1-
It is 10% by weight. If the blending amount is less than 0.01% by weight, prevention of breathing water generation, laitance generation, etc. will be incomplete, and the object of the present invention will not be achieved.

On the other hand, if the amount exceeds 20% by weight, the strength of the concrete will be impaired and it will also be economically disadvantageous.

The method of applying the admixture of the present invention to a cement composition is as follows: (1) A predetermined amount of the admixture is mixed into the above cement composition, and the mixture is mixed using a mixing device such as a concrete mixer, mortar mixer, ribbon blender, conical blender, or screw conveyor. be.

Usually, concrete or mortar is obtained by adding a predetermined amount of water to this premixed dry cement composition and kneading it.

(2) A method in which water is added to a cement composition to produce concrete or mortar, and (3) a method in which it is mixed in with concrete or mortar before pouring.

[Examples] The present invention will be further explained below with reference to Examples and Usage Examples, but the present invention is not limited thereto. Note that parts in the examples are parts by weight.

The water absorption start time of the admixture material (the time from when it comes into contact with water until it actually starts absorbing water) was determined by the following measurement method.

Measuring method> The saturated absorption ffi (Ag/g) of the admixture with alkaline water adjusted to pH 12.5 in advance is measured by the tea bag method. Add the above alkaline water containing Ag to a measuring cylinder, then add a sample of tg, and measure the time until the volume of the absorbed and swollen product reaches 20% of the initial alkaline water volume. The time required was defined as the water absorption start time.

Examples 1 to 4 Commercially available powdered water-absorbing resins "Aquaric C3J (manufactured by Nippon Shokubai Kagaku Kogyo aGlj, cross-linked sulfonate-based water-absorbing resin, water absorption start time within 1 minute)", "Sumikagel S-50J"
(manufactured by Sumitomo Chemical F) 1, saponified vinyl acetate-acrylic acid ester copolymer, water absorption start time within 1 minute),
"K Nigel" (manufactured by Kuraray ■, isobutylene-maleic acid copolymer cross-linked product, water absorption start time within 1 minute) or "Sunwet" 1N-100ONPSJ (manufactured by Sanyo Chemical Industries, Ltd., starch-acrylate graft copolymer cross-linked product,
A 5% toluene solution of polystyrene was coated on the surface of the water absorption fJ (approximately 3 minutes starting time) using a spray drying method and dried.
A water absorbent composition having a weight ratio of water absorbent resin/polystyrene of 100/3G was obtained. These are mixed material (A) of the present invention,
(El), (tl:) and (D). The water absorption start time was about 70 minutes in all cases.

Example 5 20 parts of beeswax (melting point: about Cθ°C) and 30 parts of synthetic wax (melting point: about 100°C) were melted and liquefied at 120°C, and water-absorbing resin “Sunwet IM-1000MPsJ” was added to this.
50 parts were added and dispersed and stirred. This liquid dispersion was placed in a container of appropriate size, cooled, and ground to a particle size of 100 to 20 mesh. This was further heated with hot air at 60° C. for 2 hours, and then cooled to obtain a powdery water absorbent composition. This is referred to as the admixture material (E) of the present invention. After this, the water absorption start time was approximately 50 minutes.

Example 6 Ethylene-vinyl acetate copolymer (vinyl acetate-containing fi45
%) 30 parts and water absorbent resin “Sunwet IM-1000”
470 parts of MPS were melt-kneaded using a 1' Y-MI material and extruded into chips with a particle size of 0.3 ml to obtain a mixed MI composition.

This surface was coated with a 5% solution of polystyrene in toluene/ethyl acetate by spray drying and dried to obtain a water absorbent composition having a kneaded composition/polystyrene weight ratio of 100/+5. This is referred to as the admixture material (F) of the present invention. The water absorption start time of this product was about 80 minutes.

Usage examples 1 to 4 Ordinary Portland cement 17250g 5 Tap water 9
300g1 Fine aggregate (river sand) 38900g1 Coarse aggregate (
Mixed materials (A) of Examples 1 to 4 were added to concrete containing 48,500 g of river gravel and 34.5 g of AE water reducer.
120 g of each of B), (C), or (D) were mixed. JIS A 1138 except that the kneading time is 1 hour.
Concrete was prepared according to ``How to Make Concrete in a Test Laboratory'', and its breathing m1, breathing rate, and compressive strength were measured. These results are shown in Table 1.

In addition, for the breathing test, JIS A 11+
Samples were collected according to 5 ``Method for sampling concrete that has not yet solidified'' and measured according to JIS A 1123 r Breathing test method for concrete''.

In addition, JIS A 1132 is used for compressive strength testing.
A specimen was prepared according to ``How to Make a Specimen for Concrete Strength Test'' and measured according to ``JIS A +108 r Concrete Compression Test Method''.

Comparative Examples 1 to 5 The results obtained when the admixture of the present invention was not added are also listed in Table 1 as Comparative Example 1. On the other hand, the commercially available water absorbent resin "
Aqualic C3J (made by Nippon Shokubai Chemical Industry (11))
, ``Sumikagel S-50J (manufactured by Sumitomo Chemical Co., Ltd.)
When I used RL (I Gel) (manufactured by Kuraray A) or Sunwet IM-1000MPSJ (manufactured by Sanyo Chemical Industries, Ltd.), the concrete lost all fluidity after about 5 minutes of mixing. Subsequent tests were not possible. (Comparative Examples 2 to 5) Table 1 (Unit of compressive strength: kgf/Cff1) Breathing was clearly reduced by adding the admixture of the present invention. No decrease was observed.

Usage examples 5 to 7 Ordinary Portland cement) 520g, tap water 338g
g.

4.3 g of each of the admixtures (A), (B), or (F) of the present invention were mixed into a mortar containing 1040 g of Toyoura Shibefu sand and kneaded. Table 2 shows the results of a length change test conducted on this mortar.

The test method was based on JIS A 1129r Mortar and Concrete Length Change Test Method (Comparator Method). Test conditions are temperature 2o±1'C, humidity GO
f: 5%R11.

Comparative Example 6 In Use Examples 5 to 7, the results obtained when the admixture of the present invention was not added are also listed as Comparative Example 6 in Table 2.

Table 2 The length change rate was significantly reduced.

Usage examples 8 to 10 Ordinary Portland cement 345 kg/i”, tap water 1
8 [ikg/, fine aggregate (river sand) 778 kg/m',
Coarse aggregate (river gravel) 970kg103, AEf4 water agent 0
．． Hkg/113 and the admixture of the present invention (C), (E
) or (F) with a mix of 2.4 kg/m3 each vertically. The mold was poured into a rectangular parallelepiped mold measuring 1 m x 1 m x 3 m high, and the generation of breathing water and laitance deposition were observed. After 28 days, a concrete core drill was used to drill 0.00 mm in the height direction from the bottom. Noodles, 1.5
The core specimen was cut out from a position of 2.7 m at right angles to the casting direction, and the compressive strength was determined as lllll. The results of these tests are shown in Table 3.

In addition, when cutting the core from concrete, JI
According to S A +107.

Comparative Example 7 In Use Examples 8 to 10, the results obtained when the admixture of the present invention was not added are also listed as Comparative Example 7 in Table 3.

By adding the admixture material of the present invention, Table 3 (unit of core compressive strength kgf/cm2; material age; 2
8th day) By adding the admixture material of the present invention, there was almost no breathing water and almost no laitance deposition was observed. In addition, the core compressive strength was uniform with almost no difference observed between the upper layer and the lower layer. On the other hand, in Comparative Example 7, the compressive strength of the upper layer decreased.

[Effects of the Invention] When the admixture material of the present invention is mixed into cement, concrete, and mortar, it exhibits the following effects.

(1) Almost no breathing water is generated.

The admixture material of the present invention has sufficient water absorption capacity even after pouring (which usually takes 10 to 120 minutes to transport concrete made from fresh combrand etc. to a construction site using a mixer truck, etc.) .

Therefore, the breathing water generated after concrete placement can be absorbed inside the concrete, so that the generation of breathing water on the concrete surface can be reduced.

(2) There is no need to worry about breathing water accumulating on the lower surfaces of horizontal reinforcing bars, coarse aggregate, etc., forming a water film, and reducing adhesion to mortar.

Breathing water migrates to the upper layer over time after concrete is placed, but during this process, breathing water often forms a water film on the lower surface of horizontal reinforcing bars and coarse aggregate, reducing the adhesion of mortar. . However, since the admixture material of the present invention absorbs breathing water inside the concrete 11IY structure, the above-mentioned problem of poor adhesion to mortar due to a water film does not occur.

(3) The water path created by the upward migration of breathing water remains as it is even after the concrete has hardened, and there is no problem of lowering the strength and durability of the concrete structure.

(4) Uniform quality of the structure can be achieved.

(5) There is almost no deposition of laitance.

Therefore, there is no fear that the laitance deposited on the concrete surface will scatter and harm human health, and in addition, concrete with excellent appearance and surface smoothness can be obtained.

Furthermore, when pouring new and old concrete, there is no need to remove laitance, leading to labor savings and shorter construction times.

(6) There is no reduction in workability when placing concrete.

As described in Comparative Examples 2 to 5, when conventional water-absorbing resins are used as admixtures, water absorption starts too quickly, resulting in extremely low fluidity of concrete and poor workability and stability during pouring. . However, since the admixture material of the present invention controls the water absorption start time, it is possible to ensure workability close to that obtained without additives.

(7) It is possible to reduce the drying shrinkage of concrete and prevent the occurrence of cracks.

Water absorbed by the water-absorbing polymer inside the concrete gradually transfers to the concrete side, keeping the concrete moist for a longer period than usual, reducing drying shrinkage and preventing cracks from forming.

Because of the above-mentioned effects, cement concrete or mortar mixed with the admixture of the present invention is particularly effective when concrete is manufactured from fresh combrand and transported to a construction site in a mixer truck or the like. Therefore, it can be applied to housing construction sites; dam construction sites; concrete paved surfaces such as roads; bridge support construction sites, etc. Other box culverts; precast boards, piles, blocks, U-shaped grooves, tetra pots, shield segments,
Secondary concrete products such as bridges; It is effective for all situations that require a mixture of cement, concrete, and mortar, such as concrete pouring work.

Claims (1)

[Claims] 1. A cement/concrete and mortar admixture comprising a water-absorbing composition obtained by coating the surface of a water-absorbing resin with a hydrophobic substance. 2. A mixed material for cement, concrete and mortar comprising a water-absorbing composition obtained by coating the surface of a kneaded composition of a thermoplastic resin and/or rubber with a water-absorbing resin with a substance that is hydrophobic to water. 3. The hydrophobic substance is a hydrophobic synthetic resin, a hydrophobic natural resin,
The admixture according to claim 1 or 2, which is a substance selected from the group consisting of long-chain fatty acids, long-chain alcohols, and rubbers.