JP7699465B2 - Retarders and concrete joint treatment method - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act 2020 Japan Society of Civil Engineers National Conference 75th Annual Academic Lecture [Collection of Lecture Abstracts] Publication date August 1, 2020 Construction Machinery Construction Vol. 72 No. 9 (No. 847) Date of issue: September 25, 2020

The present invention relates to a set retarder and a method for treating concrete joints.

Conventionally, when constructing a concrete structure, a joint treatment is carried out (for example, see Patent Document 1). If the joint treatment is not carried out properly, it can become a weak point in the structure and affect durability. A typical joint treatment involves spraying a set retarder at the joint where bleeding has subsided, and then carrying out a laitance treatment the following day.

JP 2013-256804 A

However, with the above-mentioned conventional general joint processing, for example, if concrete is poured on a Friday, the laitance processing must be carried out on the following Saturday, which poses the problem of being forced to work on the holiday.

Meanwhile, in the construction industry, securing future workers is a major issue, with young engineers leaving the industry and fewer new recruits joining the industry each year. As a result, the "two-day weekend and work style reform" initiative is being promoted in the construction industry, which includes further strengthening efforts to correct long working hours and create an environment in which workers can take time off.

The present invention has been made in consideration of the above, and aims to provide a set retarder and a concrete joint treatment method that can realize a two-day weekend system at construction sites.

In order to solve the above problems and achieve the objectives, the set retarder of the present invention is a set retarder applied to the surface of concrete during concrete joint processing, and is characterized by having the ability to adjust the duration of the set retarding effect when applied to the surface of concrete.

The other retarder according to the present invention is characterized in that it is an ultra-retardant type whose retarding effect lasts for up to 72 hours when applied to the surface of concrete.

In addition, another set retarder according to the present invention is characterized in that, in the above-mentioned invention, it contains an outer film and a main agent having a set retarding effect covered by this outer film, and has a release control function in which the release of the main agent is controlled by the outer film reacting with the concrete to release the main agent.

The other setting retarder according to the present invention is characterized in that it is a thickening setting retarder composed of compound A having a setting retarding effect and compound B, which is one or more types of alkaline thickening type thickeners whose aqueous solution viscosity increases in an alkaline environment, in the above-mentioned invention.

The other setting retarder according to the present invention is characterized in that in the above-mentioned invention, the compound A is composed of one or more of oxycarboxylic acid, lignosulfonic acid, phosphonic acid, humic acid and/or salts thereof, or sugars and polyols.

In addition, another setting retarder according to the present invention is characterized in that, in the above-mentioned invention, compound B is an acrylic thickener, and is composed of one or more thickeners whose aqueous solution viscosity at 5% active ingredient is 10 mPa·s or less at pH=5 and 200 mPa·s or more at pH=12.

Another setting retarder according to the present invention is characterized in that in the above-mentioned invention, the composition of the compound A and the compound B is 10/90 to 60/40 by weight.

Another set retarder according to the present invention is characterized in that, in the above-mentioned invention, it is used by spraying 150 ml to 1500 ml ^per m2 of concrete surface area.

The concrete joint treatment method according to the present invention is characterized in that the above-mentioned set retarder is applied to the surface of the concrete to adjust the setting time of the concrete.

The set retarder according to the present invention is applied to the surface of concrete during concrete joint processing, and has the function of being able to adjust the duration of the set retarding action when applied to the surface of concrete. Therefore, by making the duration of the set retarding action longer than usual, for example, concrete poured on Friday can be jointed on Monday. This has the effect of realizing a two-day weekend system at construction sites.

In addition, the other set retarder according to the present invention is an ultra-retardant type that maintains the set retardation effect for up to 72 hours when applied to the surface of concrete, so it has the effect of maintaining the set retardation effect for up to 72 hours (3 days).

In addition, another set retarder according to the present invention contains an outer film and a main agent with a set retarding effect covered by this outer film, and has a release control function that controls the release of the main agent by the outer film reacting with the concrete to release it, so that the effect of being able to easily adjust the duration of the set retarding effect is achieved.

In addition, another set retarder according to the present invention is a thickening set retarder composed of compound A, which has a set retarding effect, and compound B, which is one or more types of alkaline thickening type thickeners whose aqueous solution viscosity increases in an alkaline environment, and therefore has the effect of easily adjusting the duration of the set retarding effect.

In addition, according to another setting retarder of the present invention, the compound A is composed of one or more of oxycarboxylic acid, lignin sulfonic acid, phosphonic acid, humic acid and/or their salts, or sugars and polyols, and therefore, the duration of the setting retardation effect can be easily adjusted.

In addition, according to another setting retarder of the present invention, the compound B is an acrylic thickener, and is composed of one or more types of thickeners whose aqueous solution viscosity at 5% active ingredient is 10 mPa·s or less at pH=5 and 200 mPa·s or more at pH=12, so that the duration of the setting retardation effect can be easily adjusted.

In addition, according to another setting retarder of the present invention, the composition of the compound A and the compound B is 10/90 to 60/40 by weight, which has the effect of easily adjusting the duration of the setting retardation effect.

In addition, according to another set retarder of the present invention, 150 ml to 1500 ml is sprayed per ^square meter of concrete surface area, which has the effect of easily adjusting the duration of the set retardation effect.

In addition, according to the concrete joint treatment method of the present invention, the above-mentioned set retarder is applied to the surface of the concrete to adjust the setting time of the concrete, which has the effect of realizing a two-day weekend system at the construction site.

FIG. 1 is a schematic diagram showing a procedure of an embodiment of a concrete joint treatment method according to the present invention. FIG. 2 is a diagram showing an example of a state in which a setting retarder is sprayed.

Below, an embodiment of the set retarder and concrete joint treatment method according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment.

(Set retarder)
First, an embodiment of the setting retarder according to the present invention will be described.
The set retarder according to the present embodiment is applied to the surface of concrete during concrete joint processing, and has the function of being able to adjust the duration of the set retarding action after application to the surface of concrete. The duration of the set retarding action may be longer than that of a normal set retarder, but it is preferable that it is an ultra-retarding type that lasts for a maximum of 72 hours (3 days).

The retarder may contain an outer film and a main agent having a retarding effect covered by the outer film, and may have a release control function in which the release of the main agent is controlled by the outer film reacting with the concrete to release the main agent. This release control function makes it easy to adjust the duration of the retarding effect. An example of a retarder that embodies this is a liquid agent containing multiple small capsules. The outer film of the capsule reacts with the alkaline components and moisture in the concrete, gradually dissolves, and releases the main agent. By appropriately setting the thickness and material of the outer film of the capsule used, the size of the capsule, and the like, the desired duration can be easily adjusted. Note that the release control function of the present invention is not limited to this, and other release control functions may be used.

According to this embodiment, by extending the duration of the setting retardation effect, for example, it is possible to carry out the pouring process of concrete poured on a Friday on Monday. This makes it possible to realize a two-day weekend system at construction sites.

In the above embodiment, a thickening retarder may be used that is composed of compound A having a setting retarding effect and compound B, which is one or more types of alkaline thickening type thickeners whose aqueous solution viscosity increases in an alkaline environment. In this way, the duration of the setting retarding effect can be easily adjusted.

Compound A may be composed of one or more of oxycarboxylic acid, lignin sulfonic acid, phosphonic acid, humic acid and/or their salts, or sugars and polyols. Compound B may be composed of one or more acrylic thickeners having an aqueous solution viscosity of 10 mPa·s or less at pH=5 and 200 mPa·s or more at pH=12 at 5% active ingredient. Compound A and compound B may be composed of, for example, 10/90 to 60/40 by weight ratio. The setting retarder may be used by spraying, for example, 150 ml to 1500 ml ^per m2 of surface area of concrete.

(Set retarder composition)
Next, an embodiment of the setting retarder composition will be described.
In a first embodiment, the present invention provides a retarder composition for cement-based building materials, said composition comprising, in each case relative to the total weight of the composition:
a) 3-13 wt. % of at least one set retarder selected from the group consisting of sugar acids, sugars, sugar alcohols, hydroxycarboxylic acids, lignosulfonic acids, phosphoric acids, phosphonic acids, boric acids, and salts thereof;
b) 10-20 wt % of at least one thickening agent selected from alkali-swellable polymers; and
c) The remainder is water.

A retarder in the context of the present invention is a chemical or mixture of chemicals that slows down the hydration of cement-based building materials after the addition of mixing water, compared to the case without the addition of such retarder. In particular, retarders affect the hydration reaction at early ages and reduce the increase in compressive strength.

The at least one retarder is present in the composition of the present invention in an amount of 3 to 13 wt%, preferably 5 to 10 wt%, particularly preferably 8 wt%, based on the total weight of the composition. According to an embodiment, the at least one retarder is selected from the group consisting of sugar acids, sugars, sugar alcohols, hydroxycarboxylic acids, lignosulfonic acids, phosphoric acids, phosphonic acids, boric acids and salts thereof.

In the present invention, a sugar acid is a monosaccharide having a carboxyl group, such as aldonic acid, urosonic acid, uronic acid, or aldaric acid. A preferred sugar acid is aldonic acid. Examples of sugar acids useful in the present invention include, but are not limited to, glyceric acid, xylonic acid, gluconic acid, ascorbic acid, neuraminic acid, glucuronic acid, galacturonic acid, iduronic acid, tartaric acid, mucic acid, and saccharic acid. The sugar acid exists as a free acid or as a salt. In an embodiment, the salt of the sugar acid is a salt with a metal of groups IIa, IIa, IIb, IIb, IVb, VIIIb of the periodic table of the elements. Preferred salts of the sugar acid are salts of alkali and alkaline earth metals, iron, cobalt, copper, or zinc. Particularly preferred are salts of monovalent metals such as lithium, sodium, and potassium.

The sugars in the present invention are carbohydrates having an aldehyde group. In a particularly preferred embodiment, the sugars belong to the group of monosaccharides or disaccharides. Examples of sugars include, but are not limited to, glyceraldehyde, threose, erythrose, xylose, lyxose, arabinose, ribose, allose, altrose, glucose, mannose, gulose, idose, galactose, talose, fructose, sorbose, lactose, maltose, sucrose, lactulose, trehalose, cellobiose, chitobiose, isomaltose, palatinose, mannobiose, raffinose and xylobiose.

The sugar alcohol of the present invention is a polyhydric alcohol that can be derived from a sugar by an oxidation-reduction reaction. Thus, the sugar alcohol belongs to the class of alditols. Examples of sugar alcohols include, but are not limited to, ethylene glycol, glycerol, diglycerol, threitol, erythritol, pentaerythritol, dipentaerythritol, xylitol, ribitol, arabitol, sorbitol, sorbitan, isosorbide, mannitol, dulcitol, fucitol, iditol, iditol, inositol, volemitol, lactitol, maltitol, isomalt, maltotriitol, maltotetraitol, and polyglycitol.

Hydroxycarboxylic acids according to the present invention are carboxylic acids containing an OH-moiety in the same molecule. Examples of hydroxycarboxylic acids include, but are not limited to, malic acid, citric acid, isocitric acid, tartaric acid, tartronic acid, mandelic acid, salicylic acid, lactic acid, tannic acid and humic acid. Preferred hydroxycarboxylic acids are citric acid, tartaric acid and lactic acid. Hydroxycarboxylic acids are present as free acids or salts. According to an embodiment, the salts of hydroxycarboxylic acids are salts with ammonium or metals of groups IIa, IIa, IIb, IIb, IVb, VIIIb of the periodic table of the elements. Preferred salts of hydroxycarboxylic acids are alkali metal salts, alkaline earth metal salts or ammonium salts.

The phosphoric acid of the present invention is a derivative of phosphoric acid. The phosphoric acid is free phosphoric acid, an oligomer of phosphoric acid, and/or a polymer of phosphoric acid, such as diphosphate, triphosphate, tetraphosphate. The phosphoric acid can be present in a protonated, partially deprotonated, or fully deprotonated state. Fluorinated phosphoric acid is also possible. Examples of suitable phosphoric acids are trisodium orthophosphate, tetrasodium pyrophosphate, sodium hexametaphosphate, and disodium fluorophosphate. Phosphoric acid can refer to an ester of phosphoric acid or an ester of one of its oligomers. Esters of phosphoric acid include, but are not limited to, the above-mentioned mixed esters with hydroxycarboxylic acids and/or sugar acids, mixed esters with carboxylic acids, especially mixed esters with fatty acids, alkyl esters, aryl esters, and esters with polyalkylene glycols.

The phosphonic acids may be mono-, di-, tri-, tetra-, penta- or hexa-phosphonic acids as well as their oligomers and/or esters. Preferably, the phosphonic acids have an organic functional moiety. The phosphonates exist in protonated, partially deprotonated or fully deprotonated states. Examples of suitable phosphonic acids are 1-hydroxyethylidene-1,1-diphosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 3-aminopropylphosphonic acid, aminotri(methylenephosphonic acid), and diethylenetriaminoepenta(methylenephosphonic acid).

The preferred borate salts in the present invention are salts of boric acid, boric acid or borax.

Sodium gluconate is a particularly preferred embodiment as the at least one setting retarder.

At least one thickening agent is selected from alkali-swellable polymers.

It is also possible to use a mixture of different alkali-swellable polymers. At least one thickener is present in the composition according to the invention in an amount of 10 to 20 wt. %, preferably 12 to 17 wt. %, relative to the total weight of the composition.

According to a preferred embodiment, the at least one thickening agent is an alkali-swellable polymer, preferably an alkali-swellable polymer emulsion. The alkali-swellable polymer is a carboxylic acid functional copolymer that can be produced by free radical emulsion polymerization of ethylenically unsaturated monomers. The alkali-swellable polymer is a preferential copolymer of (meth)acrylic acid and an ester of (meth)acrylic acid. The copolymer of (meth)acrylic acid and an ester of (meth)acrylic acid may have a content of further monomer units such as propylene, butadiene, styrene, vinyl chloride, vinyl alcohol and/or esters of vinyl alcohol such as vinyl acetate. The most preferred copolymers in the present invention are copolymers of methacrylic acid and acrylic acid esters, in particular of methacrylic acid and ethylene ester of acrylic acid in a molar ratio of about 1:1. The copolymer is a polymer with an anionic charge. Typically, the alkali-swellable polymer has a number average molecular weight Mn of 10,000 to 10,000,000 g/mol, preferably 10,000 to 1,000,000 g/mol, and particularly a high molecular weight of 30,000 to 500,000.

The glass transition temperature (Tg) of the alkali-swellable polymer is not particularly limited and can vary over a wide range. The Tg of the alkali-swellable polymer measured according to ASTM D3418 is in the range of -20°C to +90°C. The alkali-swellable polymer thickens by absorbing water and swelling, and the thickening depends on the change from low to high pH. At low pH, the copolymer is insoluble in water, but becomes neutralized and becomes soluble at high pH and thickens. Mixtures of two or more alkali-swellable polymers are also possible.

Particularly preferred such alkali-swellable polymers are aqueous emulsions, also called ASE (alkali-soluble/swellable polymer emulsions). Preferred ASEs have a solids content of 10-40 wt%, especially 25-35 wt%. The alkali-swellable polymer emulsions of the present invention show effective thickening at pH >5, more preferably pH >7, especially pH >8.

Alkali-swellable polymers can also be hydrophobically modified. This is typically done by incorporating a small number of hydrophobic macromonomers into the polymer. Such macromonomers are esters of (meth)acrylic acid with hydrophobic alcohols, derivatives of styrene, or non-ionic surfactants. The molecular weight of the hydrophobically modified alkali-swellable polymers is typically lower than that of the ASE polymers mentioned above. Hydrophobically modified alkali-swellable polymers are preferentially used as aqueous emulsions, also called HASE (hydrophobically modified alkali-soluble polymer emulsions).

Suitable ASEs and HASEs are available under the brand names Acrysol from Dow Chemical, Acryset from Nippon Shokubai, or Rheovis from BASF.

Pigments can be used to add color to the retarder composition of the present invention. This is useful during application of the retarder composition to identify where it has already been applied. Suitable pigments are organic or inorganic pigments. Organic dyes can also be used. Suitable pigments are known to those skilled in the art. According to an embodiment, titanium dioxide ( _TiO2 ) is used as the pigment. According to another embodiment, azo pigments are used as the pigment. According to yet another embodiment, fluorescein, rhodamine or derivatives thereof are used as the pigment. Pigments can be used in the retarder formulation of the present invention in an amount of 1 wt% or less, based on the total weight of the retarder composition.

In a second embodiment, the present invention relates to a retarder composition for cement-based building materials, said composition comprising:
a) 3 to 13 wt. % of at least one additive for cement hydration selected from the group consisting of sugar acids, sugars, sugar alcohols, hydroxycarboxylic acids, lignosulfonic acids, phosphates, phosphonic acids, borates and their salts;
b) 10-20 wt. % of at least one thickening agent selected from the group consisting of alkali-swellable polymers;
c) optionally 20 to 90 wt. %, preferably 50 to 90 wt. %, in particular 67 to 87 wt. %, of at least one filler,
d) 0-1 wt. % pigment;
e) Consists of 0-1 wt% preservative, and the remainder is water.

In a third embodiment, the present invention relates to a method for producing a washed concrete finish, comprising the steps of: a) contacting a surface of an unhardened cementitious building material with a retarder composition as described above; b) hardening the cementitious building material while the surface is in contact with the retarder composition; and c) removing the retarder composition and residual materials from the concrete surface.

(Method of processing concrete joints)
Next, an embodiment of a concrete joint treatment method according to the present invention will be described.
The concrete joint processing method according to the present embodiment applies the above-mentioned retarder to the surface of the concrete to adjust the setting time of the concrete. Specifically, as shown in FIG. 1, first, a retarder whose duration of retarding action is adjusted to a predetermined time (e.g., 3 days) is prepared in advance (step S1). Next, concrete pouring is completed, for example, on Friday evening (step S2). After the concrete pouring is completed, the concrete is left to stand for a predetermined time (e.g., 1 to 3 hours) until the bleeding settles down, and then the retarder is sprayed on the concrete surface (step S3). An example of the spraying state is shown in FIG. 2 (1).

The retarding effect of this retarder lasts for three days, so work can be rested on the following Saturday and Sunday (step S4). Next, on Monday, the concrete is poured using a water jet or other method (step S5). An example of the completed concrete pouring process is shown in Figure 2 (2).

In this way, according to this embodiment, the concrete poured on Friday can be joined on Monday, and the intervening Saturday and Sunday can be set as holidays. This allows a two-day weekend system to be realized at construction sites. This makes it possible to break away from the 3Ks known as "hard, dirty, and dangerous" in the construction industry, and to realize the new 3Ks of "salary, holidays, and hope." It is expected that increased productivity will lead to higher salaries, two days off per week will be guaranteed, and the workplace will become one in which people can have hope.

This invention is in line with the promotion of work style reform, and considering the labor costs that have been paid for joint processing up until now, it is believed that there is high value in using the retarder, even if the material cost of the retarder increases.

As explained above, the set retarder according to the present invention is applied to the surface of concrete during concrete joint processing, and has the function of being able to adjust the duration of the set retarding action when applied to the surface of concrete. Therefore, by making the duration of the set retarding action longer than usual, for example, concrete poured on Friday can be jointed on Monday. This makes it possible to realize a two-day weekend system at construction sites.

In addition, the other set retarder of the present invention is an ultra-retardant type that maintains the set retardation effect for up to 72 hours when applied to the surface of concrete, so the set retardation effect can be maintained for up to 72 hours (3 days).

In addition, another set retarder according to the present invention contains an outer film and a main agent with set retarding action covered by this outer film, and has a release control function that controls the release of the main agent by the outer film reacting with the concrete to release it, so the duration of the set retarding action can be easily adjusted.

In addition, another set retarder according to the present invention is a thickening set retarder composed of compound A, which has a set retarding effect, and compound B, which is one or more types of alkaline thickening type thickeners whose aqueous solution viscosity increases in an alkaline environment, so the duration of the set retarding effect can be easily adjusted.

In addition, according to another setting retarder of the present invention, the compound A is composed of one or more of oxycarboxylic acid, lignosulfonic acid, phosphonic acid, humic acid and/or their salts, or sugars and polyols, so that the duration of the setting retardation effect can be easily adjusted.

In addition, according to another setting retarder of the present invention, the compound B is an acrylic thickener, and is composed of one or more types of thickeners whose aqueous solution viscosity at 5% active ingredient is 10 mPa·s or less at pH=5 and 200 mPa·s or more at pH=12, so the duration of the setting retardation effect can be easily adjusted.

In addition, according to another setting retarder of the present invention, the composition of the compound A and the compound B is 10/90 to 60/40 by weight, so the duration of the setting retardation effect can be easily adjusted.

In addition, according to the other set retarder of the present invention, 150 ml to 1500 ml is sprayed per square ^meter of concrete surface area, so that the duration of the set retardation effect can be easily adjusted.

In addition, according to the concrete joint treatment method of the present invention, the above-mentioned set retarder is applied to the surface of the concrete to adjust the setting time of the concrete, making it possible to realize a two-day weekend system at the construction site.

As described above, the set retarder and concrete joint treatment method of the present invention are useful for concrete joint treatment, and are particularly suitable for implementing a two-day weekend system at construction sites.

Claims (7)

A set retarder applied to the surface of concrete in concrete joint treatment,
It has the ability to adjust the duration of the setting retardation effect when applied to the surface of concrete,
A thickening retarder comprising compound A having a setting retarding effect and compound B which is one or more types of alkali thickening type thickeners whose aqueous solution viscosity increases in an alkaline environment,
The compound B is an acrylic thickener, and is characterized in that it is composed of one or more thickeners whose aqueous solution viscosity at 5% active ingredient is 10 mPa·s or less at pH=5 and 200 mPa·s or more at pH=12 . The retarder according to claim 1, characterized in that it is an ultra-retardant type whose retarding effect lasts for up to 72 hours when applied to the surface of concrete. The retarder according to claim 1 or 2, which contains an outer film and a base agent having a setting retarding effect covered by the outer film, and has a release control function in which the release of the base agent is controlled by the outer film reacting with concrete to release the base agent. The set retarder according to any one of claims 1 to 3, characterized in that the compound A is composed of one or more of oxycarboxylic acid, lignin sulfonic acid, phosphonic acid, humic acid and/or their salts, or sugars and polyols. 5. The setting retarder according to claim 1 , wherein the composition of said compound A and said compound B is in a weight ratio of 10/90 to 60/40. The set retarder according to any one of claims 1 to 5 , which is used by spraying 150 ml to 1500 ml per ^m2 of surface area of concrete. A method for treating a concrete joint, comprising applying the set retarder according to any one of claims 1 to 6 to a surface of concrete to adjust the setting time of the concrete.

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