JP2013203580A - Cement hardening accelerator and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement hardening accelerator, not eroding steel rods, accelerating cement hardening at normal temperature and a low temperature because of having no temperature dependency, being excellent in strength development in a short period, and being economical; and to provide a method for producing the same.SOLUTION: A cement hardening accelerator to be added and blended in cement is a cement hydrate slurry where an aggregate is removed from an existing concrete composition or cement hydrate powders where the cement hydrate slurry is dried. It is favorable that the cement hydrate slurry passes completely through a sieve of 45 μm and further a cement hydrate is hydrated until the ignition loss of powders obtained after drying at 80°C reaches 5% or more.

Description

  The present invention relates to a cement hardening accelerator and a method for producing the same, and in particular, a cement capable of accelerating the hardening of cement paste, mortar and concrete at room temperature or low temperature and exhibiting excellent short-term strength development. The present invention relates to a curing accelerator and a method for producing the same.

As a cement hardening accelerator, many inorganic compounds and organic compounds have been conventionally known, and many of these chemicals are used.
For example, chlorides such as calcium chloride, nitrates and nitrites, sulfates and sulfites, thiosulfates, alkali metal carbonates, bicarbonates, silicates, and the like are used as inorganic compounds.
As organic compounds, formate, acetate, amino acid compounds, triethanolamine and the like are used.

  In recent years, cement hardening accelerators in which the composition of inorganic compounds and organic compounds has been devised, and cement hardening accelerators in which the blending ratio and blending combination are devised have been proposed.

  In JP 2011-088757 A (Patent Document 1), two or more kinds of alkanolamine compounds, cement dispersants such as polycarboxylic acid copolymers, lignin sulfonic acid dispersants, and naphthalene dispersants are included. The two or more alkanolamine compounds include triethanolamine and triisopropanolamine, and the mass ratio of triethanolamine to triisopropanolamine is triethanolamine / triisopropanolamine = 10 to 90. A cement hardening accelerator is disclosed which is / 90-10.

  JP-A-2003-277111 (Patent Document 2) contains slaked lime and at least one selected from thiosulfate, formate, nitrate and nitrite, and includes slaked lime and thiosulfate. Further, a cement hardening accelerator is disclosed in which the blending ratio of at least one selected from formate, nitrate and nitrite is 97/3 to 5/95 by mass ratio, and Japanese Patent Application Laid-Open No. 2001-213646. Japanese Patent Publication (Patent Document 3) proposes a cement hardening accelerator comprising a mixture of formate and sulfate.

However, conventional cement hardening accelerators such as nitrite have a large temperature dependency, and are not sufficiently accelerated particularly at low temperatures, making it difficult to use them in cold regions.
Furthermore, due to temperature fluctuations and seasonal changes, the pot life and curing time are likely to fluctuate. As a result, there was a problem that short-term strength development was not stable, especially in winter.
Moreover, the conventional cement hardening accelerator which is a chemical has a possibility of corroding a reinforcing bar when concrete and mortar are applied to a building by mixing with cement.
There is also a problem that chemicals are expensive.

JP 2011-088757 A JP 2003-277111 A JP 2001-213646 A

The object of the present invention is to solve the above-mentioned problems, without corroding the reinforcing bars, and having no temperature dependence, can promote cement hardening at normal temperature or low temperature, and therefore has excellent short-term strength development, Another object of the present invention is to provide an economical cement hardening accelerator and a method for producing the same.
Yet another object is the effective reuse of ready-made concrete compositions, such as return concrete generated during the production of ready-mixed concrete, and adherent concrete that has been disposed of by washing in the past. Is to provide.

  In order to solve the above-mentioned problems, the present inventor uses a return concrete, adhered concrete, or the like, which is a residue of a ready-made concrete composition, as a cement hardening accelerator, so that the temperature is not affected by the temperature, and even at room temperature In addition, the inventors have found that short-term strength development can be promoted and have reached the present invention.

That is, the cement hardening accelerator added to the cement of the present invention is a cement hardening accelerator characterized by being a cement hydrate slurry obtained by removing aggregate from an existing concrete composition.
Further, the cement hardening accelerator to be added to the cement of the present invention is a cement hydrate powder obtained by removing aggregate from an existing concrete composition and drying the obtained cement hydrate slurry. It is a cement hardening accelerator characterized by these.

Preferably, in the above-mentioned cement hardening accelerator of the present invention, the cement hydrate slurry passes through a 45 μm sieve, and the cement hydrate is a strong powder obtained after drying at 80 ° C. It is characterized by being hydrated until the heat loss becomes 5% or more.
More preferably, in the cement hardening accelerator according to the present invention, the ready-made concrete composition includes a return concrete composition generated during production of ready-mixed concrete and / or an attached concrete composition attached to a concrete mixer truck. It is the remainder of the composition.

The method for producing a cement hardening accelerator according to the present invention removes coarse aggregate from an existing concrete composition, then removes fine aggregate so as to contain particles having a specific size or less, and produces a cement hydrate slurry. It is the manufacturing method of the cement hardening accelerator characterized by obtaining.
In another method for producing a cement hardening accelerator according to the present invention, the coarse aggregate is removed from the ready-made concrete composition, and then the fine aggregate is removed so as to include particles having a specific size or less, and the cement water is removed. A method for producing a cement hardening accelerator, comprising obtaining a Japanese slurry and drying the cement hydrate slurry to obtain a dry fine powder.

  Preferably, in the method for producing a cement hardening accelerator according to the present invention, after the coarse aggregate is removed, the fine aggregate is removed by passing through a JIS 45 μ sieve, and the cement hydrate slurry passes through the 45 μm sieve. Furthermore, the cement hydrate is characterized by being hydrated until the loss on ignition of the powder obtained after drying at 80 ° C. is 5% or more.

The cement hardening accelerator of the present invention, when added to the cement, has no temperature dependence and can promote cement hardening at both normal and low temperatures, and can exhibit excellent short-term strength development. .
As a result, the construction can be rationalized and the road can be opened early, such as road pavement and road repair, and can be effectively used for construction requiring urgency such as emergency construction.
In addition, since the cement hardening accelerator of the present invention is prepared from a concrete composition, not a chemical, when the concrete or mortar obtained by using it together with cement as a cement accelerator is applied to a building In addition, there is no risk of corroding the reinforcing bars.
Furthermore, the remaining amount of the ready-made concrete composition, for example, the return concrete generated during the production of ready-mixed concrete, and the adhering concrete that has adhered to the concrete mixer truck and has been disposed of by washing in the past is effectively reused. be able to.
Moreover, the manufacturing method of the cement hardening accelerator of this invention is a method which can prepare the said cement hardening accelerator of this invention effectively.

The present invention will be described with reference to the following preferred examples, but is not limited thereto.
The cement hardening accelerator added to the cement of the present invention is a cement hydrate slurry obtained by removing aggregate from an existing concrete composition.
Another cement hardening accelerator added to the cement of the present invention is a cement hydrate powder obtained by removing aggregates from an existing concrete composition and drying the resulting cement hydrate slurry.

Here, the “cement hydrate” is not in a state where the cement hydration reaction is completely completed, but until the loss on ignition of the powder obtained after drying at 80 ° C. becomes 5% or more. It shall mean the hydrated state.
The “cement hydrate slurry” refers to a slurry containing the cement hydrate.
“Prefabricated concrete composition” is a concrete composition that has already been prepared and has already been produced, such as a return concrete composition generated during the production of ready-mixed concrete, or an attached concrete composition that adheres to a concrete mixer truck. A concrete composition residue is also included, and the cement hydrate contained in the preformed concrete composition is the cement hydrate.

The cement hardening accelerator according to the present invention removes the aggregate part from a precast concrete composition such as return concrete or adherent concrete with a sieve or the like, and uses the fine powder part of the obtained cement hydrate slurry as a cement hardening accelerator. To do.
In order to remove the aggregate from the ready-made concrete composition, any known separation means such as a sieve can be used.
Preferably, the coarse aggregate is first removed from the preformed concrete composition. Any known means can be used as the removing means, and for example, it can be removed by a wet screening method.

The cement hydrate slurry obtained after removing the coarse aggregate is further passed through any known separation means such as a JIS sieve to remove fine aggregate that does not pass through the sieve.
The mesh size of the JIS sieve is desirably 150 to 22 μm, particularly 45 μm, more preferably 26 μm.
The cement hydrate slurry that has passed through the separating means such as the JIS sieve is used as a cement hardening accelerator.
The degree of hydration of the cement hydrate slurry as the cement hardening accelerator is determined by hydration of cement hydrate until the loss on ignition of the cement hydrate fine powder after drying at 80 ° C. is 5% or more. It is a slurry containing a product.
Specifically, after the slurry is dried at 80 ° C., the weight loss when ignited at 1000 ° C. needs to be 5% or more.
If it is less than 5%, the effect as a cement hardening accelerator may not be effectively exhibited.

Moreover, the cement hydrate fine powder obtained by drying the cement hydrate slurry that has passed through the separating means such as the JIS sieve is dried and used as a cement hardening accelerator.
It is desirable that the drying is performed until the loss on drying at 80 ° C. is 10% or less because the ignition loss of the hydrate powder after the obtained cement hydrate is dried at 80 ° C. is 5% or more. .
Specifically, the cement hydrate fine powder is a fine powder that has passed through a sieve or the like having the JIS mesh after drying the cement hydrate slurry. That is, it is preferable that the fine powder has passed through a JIS sieve mesh of 45 μm, more preferably 20 μm.
In order to obtain cement hydrate fine powder, the dried cement hydrate slurry can be passed through the JIS sieve as it is, or the dried one can be crushed and then passed through the JIS sieve. Good.

The feature of cement hydrate fine powder is that cement hydrate slurry hydrated until the loss on ignition of cement hydrate fine powder after drying at 80 ° C. is 5% or more is dried at 80 ° C. It is dried so that the weight loss at the time becomes 10% or less.
Specifically, when the slurry is dried to form a powder, it is dried so that the weight loss when the dried product is placed at 80 ° C. for 24 hours is 10% or less. If there is more moisture than this, it is not desirable because it may change quality during storage alone or mixed with cement.

The cement hardening accelerator thus obtained can be used by changing the blending ratio according to the type and application of the cement to be used, thereby arbitrarily adjusting the setting time of the cement. it can.
For example, in terms of cement hydrate powder, 1 to 15 parts by mass, preferably 5 parts by mass, for example, can be added to 100 parts by mass of cement.
If it is less than 1 part by mass, the effect of accelerating the curing is small, and if it exceeds 15 parts by mass, the strength development is not enhanced and there are few practical advantages.

  When the above cement hydrate slurry is used as a cement hardening accelerator, it can be used as it is together with other materials when producing concrete or mortar, and when the above cement hydrate powder is used, It can be used as a premix to be mixed with cement, or it can be used together with other materials when producing concrete or mortar.

  The cement hardening accelerator of the present invention can be premixed in advance with alumina cement as described above, and can be of a powder type because it eliminates the trouble of separately adding and mixing during construction. preferable. Further, the method of mixing the curing accelerator is not particularly limited, and is blended so as to obtain a desired blending ratio. Any type of cement, V-type blender, cone blender, nauta mixer, pan-type mixer, and By mixing and blending using a mixer such as an omnimixer, concrete and mortar having no temperature dependency and excellent short-term strength development can be prepared even at room temperature or low temperature.

The invention is illustrated by the following examples and comparative examples.
Example 1
[Curing Accelerator of the Present Invention]
The curing accelerator of the present invention was prepared as follows.
However, the following materials were used as materials.
Cement (C): Ordinary Portland cement, manufactured by Sumitomo Osaka Cement Co., Ltd. Fine aggregate (S): Land sand from Kagoshima Coarse aggregate (G): Crushed stone from Kasama Admixture: High-performance water reducing agent (trade name Leo Build SP8SBS, BASF Manufactured by Pozoris)
Water: Tap water

Using each material shown in the above [curing accelerator of the present invention], each material was blended at a blending ratio shown in the following Table 1 and stirred and kneaded to prepare a concrete composition.
In Table 1, the slump value is a value measured according to JIS A 1101, and the air amount is a value measured according to JIS A 1128.

  Two hours after kneading, the coarse aggregate contained was removed from the obtained concrete composition by a known wet screening method to obtain a cement hydrate slurry. The cement hydrate slurry was hydrated so that the loss on ignition of the sample after drying at 80 ° C. was 5% or more. Next, the resulting cement hydrate slurry was separated from fine aggregate using a JIS sieve (sieving 45 μm), and the resulting slurry was dried at 80 ° C. and passed through a JIS sieve (sieving 20 μm). A fine powder of cement partial hydrate was obtained. The fine powder was used as a curing accelerator of the present invention.

(Comparative Example 1)
A commercially available curing accelerator (trade name: POZTEC 99) manufactured by BASF Pozzolith was used as comparative curing accelerator 1 for comparison.
(Comparative Example 2)
After crushing ordinary concrete that has passed the age of more than 1 year, after crushing, remove the aggregate with a JIS sieve (mesh size is nominal size 45μm) and internally divide ordinary Portland cement (Sumitomo Osaka Cement Co., Ltd.) Add 30% by weight, knead well with water at a water / powder ratio (mass ratio) of 0.3, mold, demold after 24 hours, and perform moisture curing at 20 ° C and 80% humidity for 2 days. Thereafter, autoclaving was performed at 153 ° C. for 10 hours, and after curing, the powder was pulverized to a fineness of 5000 cm ² / g as comparative curing accelerator 2 for comparison.

(Test example)
Each mortar was prepared using the hardening accelerator of obtained Example 1 and Comparative Examples 1-2.
However, the following materials were used as materials.
Cement: Ordinary Portland cement, manufactured by Sumitomo Osaka Cement Co., Ltd. Sand: JIS standard sand Curing accelerator: Curing accelerator of Example 1, Curing accelerator 1 of Comparative Example 1, Curing accelerator 2 of Comparative Example 2
Water: tap water

According to JIS R 5201 “Cement physical test method”, the water / cement ratio is mass, except that each of the above materials is used and each curing accelerator is blended in an amount of 5 parts by mass with respect to 100 parts by mass of cement. Each mortar was prepared by blending so as to have a ratio of 50% and kneading. Moreover, the mortar which does not contain said each hardening accelerator was similarly prepared for the comparison (comparative example 3).
The strength of each mortar obtained was determined in accordance with JIS R 5201 “Cement physical testing method”, and the strength after 3 days and 7 days after each mortar was placed and the setting time (start time / end time) of each mortar. , Measured in an environment of 20 ° C. and 5 ° C., respectively, and the results are shown in Table 2.

  From Table 2 above, the mortar blended with the curing accelerator of the present invention has either a normal temperature (20 ° C.) or a low temperature (5 ° C.) as compared with a mortar with a commercially available curing accelerator added and an additive-free mortar. It can be seen that even in the environment, the cement has an excellent hardening promoting effect and excellent strength development.

  Concrete and mortar using the cement hardening accelerator of the present invention have excellent short-term strength development at normal and low temperatures without depending on temperature, so short-term strength development such as emergency construction in warm and cold regions It is effectively used for rationalization and early opening of roads (road pavement, etc.) for civil engineering and building structures. In addition, the remaining portion of the existing concrete composition will be used effectively.

Claims (7)

  The cement hardening accelerator added to the cement is a cement hydrate slurry obtained by removing aggregates from an existing concrete composition.   The cement hardening accelerator added to the cement is a cement hydrate powder obtained by removing aggregate from an existing concrete composition and drying the resulting cement hydrate slurry. Accelerator.   The cement hardening accelerator according to claim 1 or 2, wherein the cement hydrate slurry passes through a 45 µm sieve, and further, the cement hydrate is an ignition of powder obtained after drying at 80 ° C. A cement hardening accelerator characterized by being hydrated until the weight loss becomes 5% or more.   The cement hardening accelerator according to any one of claims 1 to 3, wherein the ready-made concrete composition includes a return concrete composition and / or an adherent concrete composition generated during production of ready-mixed concrete. A cement hardening accelerator characterized by   A cement hardening accelerator characterized by removing coarse aggregate from an existing concrete composition and then removing fine aggregate so as to contain particles of a specific size or less to obtain a cement hydrate slurry. Production method.   Removing coarse aggregate from the ready-made concrete composition, then removing fine aggregate to include particles below a certain size to obtain a cement hydrate slurry, and drying the cement hydrate slurry; A method for producing a cement hardening accelerator, characterized in that a dry fine powder is obtained.   The method for producing a cement hardening accelerator according to claim 5 or 6, wherein after removing the coarse aggregate, the fine aggregate is removed by passing through a JIS 45µ sieve, and the cement hydrate slurry passes through the 45µm sieve. A method for producing a cement hardening accelerator, characterized in that the cement hydrate is further hydrated until the loss on ignition of the powder obtained after drying at 80 ° C. is 5% or more.