JP7528403B2 - Concrete setting and hardening control material and its manufacturing method - Google Patents

Description

Related to the technical field of concrete.

Many types of admixtures for concrete have been developed, including water reducers, fluidizing agents, hardening accelerators, set retarders, set accelerators, and shrinkage reducers. Hydration heat inhibitors, which are used to prevent heat generation in mass concrete, have also been developed.

Patent Document 1 (JP 2019-064839 A) proposes a hydration heat inhibitor for cement using a chelating agent such as citric acid, ethylenediaminetetraacetic acid, hydroxyethanediphosphonic acid, nitrilotriacetic acid, and hydroxyethylethylenediaminetriacetic acid and an oxycarboxylic acid dispersant.
Patent Document 2 (JP Patent Publication No. 2004-137091) proposes a cement admixture that contains γ-C2S and a hydration heat inhibitor (dextrin) and that can reduce the amount of heat generated by hydration.
Patent Document 3 (JP Patent Publication 7-187749A) discloses a method for providing a phenolic resin cement admixture having heat insulating properties, in which the phenolic resin is a reaction product of (a) a resorcinol component including a resorcinol novolak resin which is a reaction product of resorcinols and aldehydes, and (b) a phenolic resol resin which is a reaction product of formaldehyde and phenol, and a method for producing a phenolic resin cement admixture containing a resorcinol-modified phenolic resin and cement, in which the phenolic resin is mixed with the (b) phenolic resol resin and then the (a) resorcinol component is mixed. This invention relates to adding this admixture when mixing concrete (mortar).

JP 2019-064839 A JP 2004-137091 A Japanese Unexamined Patent Publication No. 7-187749

The objective of the present invention is to provide a concrete admixture that allows control of the hydration reaction.

1. A concrete setting and hardening regulator characterized by being cement powder coated with phenolic resin.
2. The concrete setting and hardening regulator according to 1., characterized in that the mass ratio of cement powder:phenolic resin is 100:2.5 to 10:1.
3. The concrete setting and hardening regulator according to claim 1 or 2, wherein the cement powder has a diameter of 2 mm or less.
4. A method for producing a concrete setting and hardening regulator, comprising spraying a phenolic resin solution using an anhydrous solvent onto cement powder while stirring, to coat the surface of the cement powder with the phenolic resin.
5. A method for producing a concrete setting and hardening regulator, comprising coating the surface of cement powder with a phenolic resin while melt-kneading the phenolic resin with the cement powder.
6. The method for producing a concrete setting and hardening regulator according to 4. or 5., characterized in that the stirring is accompanied by rotation, and cement powder is produced by rotary stirring.
7. A concrete that inhibits setting and hardening by mixing a concrete setting and hardening regulator described in any one of 1. to 3. with cement as a cement component, and mixing it with aggregate, water and other concrete components.

1. We have succeeded in realizing a concrete admixture with stable quality that allows control of the hydration and hardening reaction time. Because the hydration and hardening reaction time can be controlled, it can be used as a temperature rise suppressant and strength enhancer. In particular, by suppressing initial heat generation, thermal cracking can be reduced.
2. The concrete setting and hardening regulator of the present invention is a powder smaller than fine aggregate, so it can be mixed with cement powder and used, and can be mixed uniformly with concrete compositions such as aggregate.

FIG. 1 shows a test composition for exploring candidate substances. FIG. 2 shows the heat generated by the condensation reaction corresponding to the test substances shown in FIG. 1. FIG. 2 is a diagram showing a manufacturing process of phenolic resin-coated cement powder. FIG. 4 is a graph showing the results of heat generation measurement in Example 1. FIG. 2 is a diagram showing the results of a test to confirm the effect of different addition forms of phenolic resin on cement hydration reaction. FIG. 1 shows the compositions of Examples 2 to 5. FIG. 1 shows the heat generation test results of Examples 2 to 5. FIG. 1 is a diagram showing the mechanism of fever suppression.

The present invention relates to a control material that controls the time it takes for concrete to set and harden (hereinafter, also referred to as a "concrete setting and hardening control material").
The present invention also relates to a phenolic resin-coated cement powder (hereinafter sometimes referred to as "cement powder") in which a phenolic resin film is formed on a cement powder. The phenolic resin-coated cement powder according to the present invention means either a cement powder in which the phenolic resin is uniformly coated on the cement powder or a cement powder in which the phenolic resin is unevenly coated on the cement powder, or both. As a means for coating the cement powder with the phenolic resin, a spray stirring means using an anhydrous solvent or a heat melting means can be used. For example, a concrete setting and hardening regulator, which is the phenolic resin-coated cement powder, can be produced by making a solution of the phenolic resin in an ethanol solvent, spraying it on the cement powder, stirring it, and granulating it.
The phenolic resin-coated cement powder of the present invention is added to cement, mixed with concrete components such as aggregate and water, and then cast and hardened to form a concrete body. The concrete undergoes a hydration reaction and hardens while generating heat. The concrete setting and hardening regulator of the present invention can suppress the initial hydration reaction and keep the reaction heat low.
In the case of the concrete setting and hardening regulator of the present invention, when the hydration reaction starts in the concrete under alkaline conditions after casting, the untreated cement starts to hydrate, but the concrete setting and hardening regulator covered with a phenolic resin film does not come into contact with water due to the phenolic film and cannot react, so the hydration reaction is suppressed overall. Also, under alkaline conditions, the phenolic film gradually deteriorates and the exposed cement powder gradually hydrates, suppressing the initial reaction heat and ultimately resulting in the same reaction amount as that of normal concrete.
By using the concrete setting and hardening regulator of the present invention as an admixture for concrete, it is possible to realize concrete of stable quality whose hydration and hardening reaction time can be controlled. In addition, since the concrete setting and hardening regulator of the present invention can control the hydration and hardening reaction time, it can be used as a temperature rise suppressant, strength enhancer, etc.
Since the concrete setting and hardening regulator of the present invention is mixed into cement as a powder, it is preferable that the size is smaller than that of fine aggregate, and it is suitable to have a diameter of 2 mm or less, which is similar to that of sand. Furthermore, a diameter of 1 mm or less is suitable, and in one embodiment, a diameter of even finer 100 to 200 μm is suitable.
The smaller the powder, the easier it is to mix uniformly with the cement powder. On the other hand, if the diameter is large, the breakdown of the phenol resin coating is delayed, which results in a slower hydration reaction and reduced heat generation, but also slows down the development of strength with hardening. In addition, with large diameters, small coated cement powders may combine to form larger granules during the granulation process, resulting in multiple layers of coating, and even after the surface coating breaks down, the inner coatings continue to break down, prolonging the hydration reaction. Note that if the diameter is 100 μm or less, there is a possibility that the cement powder is not coated with phenol.
The amount of ethanol solvent used to dissolve the phenolic resin is set to an amount that can dissolve the phenolic resin and can be sprayed, for example, the ratio of phenolic resin to ethanol solvent is 1:9 (mass ratio). The amount of phenolic resin to be coated on the cement powder is about 2.5 to 10 parts per 100 parts of cement powder.

<Basic composition of the present invention>
<Phenol resin coated cement powder>
The type of cement to be used for coating the phenolic resin of the present invention may be any commonly used alkaline cement.
For example, Portland cement such as ordinary Portland cement, blended cement such as blast-furnace cement, and special cement based on Portland cement.

Phenolic resins are polymers mainly composed of resinous substances obtained by condensation reaction of phenols and aldehydes, and are widely used in molded products, shipments, adhesives, paints, foams, etc. As the phenolic resins, known phenolic resins such as novolac type phenolic resins, resol type phenolic resins, terpene modified phenolic resins, aralkyl type phenolic resins, dicyclopentadiene type phenolic resins, and salicylaldehyde type phenolic resins can be used. In one embodiment, the phenolic resin is a novolac type phenolic resin. Specific examples of the novolac type phenolic resin include phenol novolac resins, cresol novolac resins, biphenylene type phenolic resins, dicyclopentadiene type phenolic resins, xylylene type phenolic resins, trishydroxyphenylmethane novolac resins, and bisphenol A novolac resins, but are not limited thereto. In one embodiment, the novolac type phenolic resin is a xylylene type phenolic resin. These may be used alone or in combination of two or more. The phenol resin is used in the form of a solution in a solvent such as ethanol, or in a heated and molten state.
The resin coating on the cement powder is performed by mixing and stirring the phenol resin and the cement powder to form a film of the phenol resin on the surface of the cement powder. Coating methods include wet granulation and dry granulation. Specific examples of the wet granulation method include stirring granulation, fluidized bed granulation, and extrusion granulation, and specific examples of the dry granulation method include, but are not limited to, the melt kneading method and the compression granulation method.
When spraying the cement powder for coating, the viscosity is adjusted to a level that does not interfere with spraying. A mass ratio of cement powder to phenolic resin in the range of 100:2.5 to 100:25 is suitable. In one embodiment, the mass ratio is 100:2.5 to 100:15, in another embodiment, 100:2.5 to 10:1, and in yet another embodiment, 100:2.5 to 100:5.

The solvent for the phenolic resin of the present invention is an anhydrous solvent that is capable of dissolving the phenolic resin and does not cause a hydration reaction with the cement powder when mixed. Examples include methyl ethyl ketone, 2-ethoxyethanol, dimethylformamide, methanol, ethanol, isopropanol, and acetone. In one embodiment, the solvent is ethanol. The amount of the solvent used is an amount capable of dissolving the phenolic resin. For example, the phenolic resin concentration is about 10% by mass.

The cement powder granules coated with phenolic resin according to the present invention refer to either cement powder granules in which phenolic resin is uniformly coated on the cement powder or cement powder granules in which phenolic resin is non-uniformly coated on the cement powder, or both. In the present invention, the cement powder granules coated with phenolic resin are produced by rolling granulation while adding a phenolic resin ethanol solution to the cement powder. The cement powder granules have a particle size equal to or smaller than that of sand grains (2 mm), preferably 1 mm or less in diameter, and more preferably 100 to 600 μm in diameter, and in some embodiments, even smaller diameters of 100 to 200 μm are suitable. 100 to 200 μm is suitable. The size of the phenolic resin coated cement powder granules can be used as a factor in controlling the setting and hardening of concrete, since a larger particle size can delay the hydration reaction of concrete and slow down the heat generation.

The concrete setting and hardening regulator of the present invention is used by mixing with the components of concrete, such as cement, aggregate, and water. The concrete setting and hardening regulator coated with phenolic resin also functions as a concrete hardening agent. However, since not all of the concrete acts as a hardening agent, it is necessary to adjust the cement component. In addition, since the phenolic resin coating may disintegrate over a long period of time, the concrete can still exert its strength development function even after it has been used as a concrete body.
The ingredients that can be mixed to make concrete are the basic components of cement, water, and aggregate, as well as various commonly used admixtures.
The concrete setting and hardening regulator of the present invention is capable of suppressing the hydration reaction and keeping the heat generation temperature low, and is therefore suitable for applications in which a large amount of thick concrete is used, such as mass concrete.
When producing high-strength concrete, a large amount of high-performance air-entraining water-reducing agent must be added due to excessive viscosity, but during construction, the air-entraining water-reducing agent can be mixed in the same way as for normal concrete, and the concrete will later disintegrate and develop its strength.

<Selection test of candidate materials>
We investigated coating materials for cement powder, on the assumption that the hydration reaction of cement can be controlled by coating the powder to prevent it from coming into contact with water.
The candidate substances were ethyl cellulose (colorcon, Ethocel Standard 20 Premium), polycaprolactone (Sigma, Mw 14,000), polylactic acid-glycolic acid copolymer (Evonik, 502H), and phenolic resin (Meiwa Kasei, MEHC-7800 H), and were granulated using the composition shown in Figure 1.
For example, the granules coated with the phenolic resin (E) were granulated by the following method.
Approximately 25 g of molecular sieves (Kanto Chemical, 3A 1/16) was added to 500 mL of ethanol (Kanto Chemical, special grade reagent) to remove moisture. 90 g of ethanol was weighed into a stainless steel measuring cup, and 10 g of phenolic resin (Meiwa Chemical, MEHC-7800 H) was gradually added while stirring to dissolve, to prepare a phenolic resin solution. 10 g of ordinary Portland cement was placed in a porcelain mortar, and 10 g of phenolic resin solution was added dropwise while stirring and mixing with a pestle to prepare a granulated product. The obtained granulated product was air-dried in a draft and sieved through a stainless steel sieve with 500 μm openings to obtain a powdered product. The obtained powdered product was air-dried in a draft to remove the remaining ethanol. The air-dried powdered product was sieved through a stainless steel sieve with 106 μm openings, and the powdered product on the sieve was collected.
Mortar was made using the granulated powder and ordinary Portland cement (referred to as P ordinary cement in the figure) and a setting test was carried out. The heat generation process is shown in Figure 2.
As a result of this test, it was confirmed that the phenolic resin (E) was able to suppress heat generation as a whole, and in particular, was able to suppress heat generation at an initial stage to a great extent.
The polylactic acid-glycolic acid copolymer (D) generated more heat initially than ordinary Portland cement (A) for comparison, while ethyl cellulose (B) and polycaprolactone (C) were able to suppress the amount of heat generated more than ordinary Portland cement (A), but generated more heat initially than phenol resin (E).

400 g of phenol resin and 3600 g of ethanol were used to coat and granulate 4000 g of ordinary Portland cement to produce a concrete setting and hardening regulator, which was then mixed with 4000 g of ordinary Portland cement to produce mortar and a heat generation test was performed.
(1) Process The manufacturing process of phenolic resin-coated ordinary Portland cement granules is shown in FIG.
1) MEHC-7800H manufactured by Meiwa Kasei Co., Ltd. was used as the phenolic resin, and was dissolved in ethanol to prepare a phenolic resin ethanol solution.
2) The phenolic resin ethanol solution was sprayed onto ordinary Portland cement while being rotated and stirred.
3) Stirring was continued until the ethanol was evaporated to obtain ordinary Portland cement granules coated with phenolic resin.
4) The particles having a particle size of 106 μm or more and 600 μm or less were selected using a sieve and used as additives to mortar.
5) A mortar was prepared using the phenol resin-coated ordinary Portland cement powder and the same amount of ordinary Portland cement, and subjected to a heat generation test.

The progress of the measurement results of the calorific value of the test specimens is shown in Figure 4. For the normal cement test specimen, a mass ratio of normal Portland cement:distilled water = 1:0.5 was used. For the test specimen of Experimental Example 1, a mass ratio of normal Portland cement:normal Portland cement powder coated with phenolic resin = 1:1 was used, and the cement amount of the test specimen of Experimental Example 1 and the normal cement test specimen were the same. The cement amount and water amount of both test specimens were the same, and they were set so that the cement-water ratio of the concrete was the same.
From the results shown in FIG. 4, it was confirmed that in Experimental Example 1, in which the phenolic resin-coated ordinary Portland cement powder was mixed with ordinary Portland cement in a mass ratio of 1:1, the heat generation was suppressed more than when ordinary Portland cement was used alone, and an initial temperature suppression effect was obtained.
In this test, it was found that the concentration was suppressed to about 1/6 up to 72 hours, and was suppressed to 1/2 or less even after 96 hours.

<Test 1>
A test was conducted to examine the heat generation suppression effect when phenolic resin was coated on cement and when it was simply added.
The experiment consisted of four examples: a normal mix (A), a case where the cement was coated with phenolic resin (C), a case where the cement was not coated with phenolic resin (B), and a case where the cement was not coated with phenolic resin (D). The following mix was mixed and the calorific value was measured for 24 hours. The measurement results are shown in Figure 5. In tests A, B, and D, the materials listed in the parentheses below were mixed, and in test C, granules in which the cement was coated with phenolic resin were obtained using the method described in the steps of Example 1, and then mixed with ordinary Portland cement and water.
Test A: Using normal cement (5g cement + 2.5g water)
Test B: Phenolic resin added (cement 5g + phenolic resin 0.015g + water 2.5g)
Test C: Phenol resin coated granules (2.5 g cement + 2.5 g granules + 2.5 g water)
Test D: Phenolic resin added (cement 5g + phenolic resin 0.15g + water 2.5g)
*C and D have the same amount of phenolic resin in the granules.

As a result of the measurements, the powdered granules (Test C) in which the phenolic resin-coated cement granules of the present invention were mixed with cement in a 1:1 ratio showed a significant suppression effect on the amount of heat generated compared to Test A, in which only ordinary cement was used, and Test B, in which a small amount of phenolic resin was added to the concrete without coating it. In addition, in the case of Test D, in which the amount of phenolic resin contained in the granules was the same as that of Test C, almost no heat generation was observed, so the addition of phenolic resin alone not only suppressed the amount of heat generated, but also hardly promoted the hydration reaction of the cement itself, and did not function as cement. From the above, it was found that the cement powdered granules of the present invention (Test C), in which phenolic resin is coated on cement to form a phenolic resin film, are effective as a material for adjusting the hydration reaction of cement.

<Test 2>
Tests in Examples 2 to 5 were carried out by varying the amount of phenolic resin to be coated.
Cement powder coated with phenolic resin was produced according to the method shown in the process of Example 1 with the composition shown in Figure 6, and the same amount of cement was used to prepare mortar to produce each test specimen of Examples 2 to 5. Ordinary Portland cement was used as the cement. Comparative Example 1 was a test example in which no phenolic resin-coated cement powder was added.
The fever was measured over a 24-hour period, and the progression is shown in FIG.
The test results showed that the amount of heat generated decreased as the amount of phenolic resin coated increased, indicating that the suppression of heat generation depends on the amount of phenolic resin coated.
From the above, it was found that by adjusting the amount of coating, it is possible to control the suppression of heat generation and also to adjust the hydration reaction.

<Regarding concrete setting and hardening control>
FIG. 8 briefly explains the mechanism by which the cement powder coated with the phenolic resin of the present invention controls the setting and hardening of concrete.
The phenolic resin-coated cement powder prepared in (a) is mixed with further cement, water, and aggregate in (b) to produce ready-mix concrete (mortar). In (c), the ready-mix concrete is poured into a concrete formwork or the like and cured. The cement hydrates and hardens to form concrete.
During this process, when cement comes into contact with water, calcium carbonate components and other components dissolve, forming an alkaline solution. Since phenolic resin is alkaline soluble, the cement that was coated with the phenolic resin gradually participates in the hydration reaction, making it possible to control the setting and hardening of the concrete.
As shown in Examples 2 to 5 (see FIG. 7), the amount of heat generated can be suppressed by adjusting the amount of phenolic resin coating, which indicates that the hydration reaction, that is, the setting and hardening of concrete, can be controlled.
The setting and hardening of concrete can also be controlled by the amount of concrete setting and hardening regulator added to the concrete.
To induce reaction and develop strength, it is possible to adjust the amount of water added by moist curing or the like.

Claims (7)

A concrete setting and hardening control material characterized by being cement powder coated with phenolic resin. The concrete setting and hardening control material according to claim 1, characterized in that the mass ratio of cement powder to phenolic resin is 100:2.5 to 10:1. The concrete setting and hardening control material according to claim 1 or 2, characterized in that the cement powder has a diameter of 2 mm or less. A method for producing a concrete setting and hardening control material, characterized by spraying a phenolic resin solution using an anhydrous solvent onto cement powder while stirring, to coat the surface of the cement powder with phenolic resin. A method for producing a concrete setting and hardening control material, characterized by coating the surface of cement powder with phenolic resin while melt-kneading the phenolic resin with the cement powder. The method for producing a concrete setting and hardening control material according to claim 4 or 5, characterized in that the stirring is accompanied by rotation, and cement powder granules are produced by rotary stirring. A concrete component in which the concrete setting and hardening control material according to any one of claims 1 to 3 is mixed with cement, and the concrete is mixed with aggregate, water and other concrete components to inhibit setting and hardening.