JPH0563424B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for retarding the hardening of a hydraulic cementitious material containing a lime aluminate having a high hydration rate using hydrogen peroxide. According to the present invention,
The curing rate can be reduced without degrading other properties of the cementitious material. [Conventional technology and its problems] Hydraulic cement (e.g. alumina cement, etc.)
The aluminate lime salt contained in the It is being This early strength is a desirable characteristic depending on the application, but for example, (a) use as sufficient adhesive or blout material, (b) driving construction that requires precision, and (c) foam hardening in the production of insulating foam materials. Regarding adjustment of time, (d) approximation or adjustment of curing time with other curing components in cement, etc., it is desired to easily adjust and delay the curing speed. A typical setting retarder for aluminate lime salt is gypsum, and many other retarders have been proposed. However, since these have complex effects and side effects, there is a problem that an accurate retardation effect cannot be expected for cement paste mixtures. Furthermore, since the components of conventional retarders remain after their action, they tend to deteriorate the quality and strength of cement-based cured products. The main objective of the present invention is to overcome the above-mentioned problems and to propose a method of curing retardation that is easy to work with and easy to adjust. [Means for Solving the Problems] According to the present invention, hydrogen peroxide is added to a cement mixture containing a hydraulic cement containing an aluminate lime salt and water in an amount of 0.01% by weight or more based on the amount of the water component. A method for retarding the hardening of cementitious materials is proposed, which is characterized by causing the presence of. In this case, the action of hydrogen peroxide can be adjusted by having a reducing substance in an equivalent amount smaller than that of hydrogen peroxide in the mixture. [Detailed description of the invention] (1) Examples of aluminate lime salt Aluminate lime salt is a binary compound of CaO (hereinafter represented by C) and Al ₂ O ₃ (hereinafter represented by A). means. Typically, CA,
C ₃ A, C ₁₂ A ₇ , C ₁₁ A ₇ ·CaX ₂ , CA ₂ , CA ₆ and the like are known. Hydraulic cement to which the present invention is normally applied includes alumina cement containing CA as a main component, and C ₃ A containing 7% or more (preferably
10% or more), modified Portland cement that is made by blending aluminate lime salt with ordinary Portland cement (e.g.
Examples include jet cement containing C ₁₁ A ₇ .CaX ₂ ), synthetic aluminate lime salt cement, and mixtures thereof. In addition, the present invention relates to alumina cement and/or jet cement,
or mixtures thereof with other hydraulic cements. (2) Hydrogen peroxide (hereinafter sometimes referred to as H ₂ O ₂ ) The H ₂ O ₂ used in the present invention is 30 to 35% by weight of H ₂ O ₂ that is commercially available at low cost for industrial use.
A dilution of H ₂ O ₂ in water can advantageously be used. The above-mentioned "allowing H ₂ O ₂ to exist in an amount of 0.01% or more of the water content" means that the H ₂ O ₂ concentration is 0.01% or more by weight.
H ₂ O ₂ water may be used or mixed with
This means that H ₂ O ₂ water may be added to make the H ₂ O ₂ concentration 0.01% or more. The concentration of H ₂ O ₂ water to be applied is not limited as long as it is 0.01% or more depending on the purpose and use.
However, it is generally about 0.01 to 5%, and usually about 0.05 to 2%. To avoid _the effect of _H2O2 decomposition gas _in high concentration _H2O2 water,
Reducing substances (such as sulfites or nitrites) can also be used in combination. In addition, regardless of the concentration of H ₂ O ₂ , by adding the reducing substance to the cement mixture, the action of H ₂ O ₂ can be interrupted (for example, for about 1 to 24 hours), and the reducing agent can be consumed. Later, the effect of applying H ₂ O ₂ can be achieved. The amount of the reducing substance added is generally smaller than the molar amount (equivalent) of H ₂ O ₂ (for example, 2/3 or less equivalent)
It is. In addition, when producing a foamed heat insulating material using a foaming agent, since a high concentration of H ₂ O ₂ has a slight foaming effect, the foaming effect may be promoted. Furthermore, when base-reactive aggregate is used as an aggregate in the cementitious mixture according to the present invention, the presence of H ₂ O ₂ water may have the side effect of suppressing the alkali-silica reaction of the aggregate. This will be achieved together. (3) Specific Examples 1 to 3 2 parts by weight of river sand were added to 1 part by weight of a 1:1 weight ratio mixture of alumina cement and ordinary Portland cement. Put 3 parts by weight of the cement composition into a mortar, add 0.6 parts by weight of water or an aqueous H ₂ O ₂ solution, and knead with a pestle to determine the viscosity duration (time until kneading becomes virtually impossible). ) was measured. The results are shown in the table below. Note that no cement additive was used because the purpose was to detect the action and effect of H ₂ O ₂ .

[Table] As shown above, it has been demonstrated that the presence of H ₂ O ₂ in the mixing water effectively retards the hardening of the cementitious material. (4) Examples 4 to 7 Add water or 1 part by weight of a 1:1 weight ratio mixture of alumina cement and ordinary Portland cement.
The rate of heat generation vs. elapsed time was measured for a slurry to which 5 parts by weight of aqueous H ₂ O ₂ was added. A calorimeter whose ambient temperature was maintained at 25°C was used as a measuring device. The results are shown in the accompanying Figures 1-2 and below. In addition, due to the purpose and convenience of the experiment, the experiment was conducted in the form of a slurry using approximately 5 times the amount of water without using aggregate or cement additives. As clearly shown in Figures 1 and 2, an initial exothermic peak was observed within 15 minutes after the start of the measurement (addition of water) as shown in the table below. In addition, the heat generation rate on the vertical axis
Cal/hr·g means the calorific value generated per hour per gram of dry weight of cement.

[Table] Considering the data in Figures 1 and 2, the initial heat generation (11.9 calories) in Figure 1 (Example 4),
The secondary and tertiary exotherms are mainly due to the heat of hydration of the aluminate lime salt in the cement mixture.
In Examples 6 and 7 of FIG. 2, there is no secondary heat generation, and in Example 5, a low degree of secondary heat generation is observed. The initial heat generation (3 calories) in Example 5 in Figure 2 is the sum of (a) the heat of hydration of the aluminate lime salt and (b) the heat of reaction between oxygen and the aluminate lime salt during the generation of H ₂ O ₂ . It is estimated that the heat of hydration is less than 3 calories. For example, of the initial heat generation (27.6 calories) in Example 7 in Figure 2, less than 3 calories is the heat of hydration, and 24.6 calories or more is the heat of reaction between the aluminate lime salt and H ₂ O ₂ . Presumed. That is, when comparing FIG. 1 (Comparative Example 4) and FIG. 2 (Examples 5 to 7), it is found that
By adding H ₂ O ₂ , the hardening effect of the lime aluminate in the cement is reduced or substantially lost (not expressed) under the action of H ₂ O ₂ . It is believed that the hardening of the cements in Examples 6 and 7 is substantially dependent on the hydration hardening of other slow setting components other than the lime aluminate. According to Examples 1 to 3 and Examples 4 to 7 above, the hydration hardenability of lime aluminate in cement is
It has been demonstrated that it is reduced or substantially lost (stopped) by the action of H ₂ O ₂ . [Functions and Effects] According to the present invention, it is possible to retard the hardening of a hydraulic cement material containing an aluminate lime salt having a high hydration rate by a hydrogen peroxide solution. the
Although the effect of H ₂ O ₂ is not fully understood, H ₂ O ₂ in the mixing water of cement compositions
is thought to act on the aluminate lime salt fine particles to modify the gel structure involved in the hydration reaction, thereby slowing or stopping the hydration rate. Aluminate lime salts contained in hydraulic cements (e.g. alumina cement) have excellent properties such as high adhesive strength, base/acid resistance, high heat resistance, and low temperature curing properties, and have a greatly rapid hydration rate. It is strong. In the present invention, only the hydration hardening rate of the aluminate lime salt is slowed or stopped, while other properties are preserved. As a result, they can be used, for example, in (a) adequate adhesion or use as grouting materials, (b) precision driving, (c) adjustment of foam curing time in the production of insulating foams, and (d) other slow-moving components in cement. Regarding the approximation or adjustment of the curing time with the hard curing component, by easily adjusting and delaying the curing speed,
Excellent effects can be achieved. Further, conventional setting retarders tend to have components remaining in the cured cement after their action, degrading quality, strength, etc., but the present invention, which uses H ₂ O ₂ , does not have such adverse effects.

[Brief explanation of the drawing]

The accompanying drawing is a graph of heat release rate versus elapsed time for a slurry consisting of an equal mixture of alumina cement and Portland cement and a water component. FIG. 1 is a graph of comparative experimental example 4 using water as the water component, and FIG. 2 is a graph of experimental examples 5 to 4 using hydrogen peroxide at various concentrations as the water component.
This is a graph of No.7.

Claims (1)

[Claims] 1. A cement mixture containing a hydraulic cement containing an aluminate lime salt and water, characterized in that hydrogen peroxide is present in an amount of 0.01% by weight or more based on the amount of the water component. A method for delaying hardening of the cementitious material. 2. The method of claim 1, wherein the action of hydrogen peroxide is controlled by the presence of a reducing substance in the cementitious mixture in an amount smaller than the equivalent of hydrogen peroxide. 3. The method of claim 1 or 2, wherein the cementitious admixture comprises an alumina cement and/or a jet cement.