JPH107443A - Cement admixture and cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote both the setting and hardening of a mortar or a concrete and the development of the short time strength by including gypsums, active silica and an aluminate of an alkali metal or a silicate thereof. SOLUTION: This cement admixture comprises gypsums, active silica, an aluminate or a silicate of the alkali metal. Furthermore, the cement composition is obtained by blending 100 pts.wt. of a cement with 1.0-6 pts.wt. of gypsums having >=2500cm<2> /g specific surface area (measured according to the Blaine method), 5-10 pts.wt. of an active silica and 0.1-0.8 pts.wt. of an aluminate of an alkali metal or a silicate thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement admixture and a cement composition, and more particularly to a cement admixture and a cement composition which accelerate the setting and hardening of mortar or concrete during heat curing such as steam curing, and promote the development of short-time strength. Used for early demolding of concrete secondary products.

[0002]

2. Description of the Related Art Conventionally, secondary concrete products are of various types and types, and are sold in large quantities. It is necessary to keep a large number of them, and a vast product yard (site) is also required. Therefore, various early demolding methods are being studied in order to increase production efficiency with as few molds as possible. Common methods of early demolding include raising the curing temperature, using highly hydraulic cements, or using strong cements such as chlorides, nitrates, and rhodanates to accelerate the setting and hardening of concrete. The use of setting accelerators is conceivable.

[0003] However, such a method for forcing the hydration reaction of cement to accelerate the demolding strength in a short time (depending on the shape and weight of the secondary product, but generally, the
It is 6 N / mm ² is ~15N / mm ²⁾ can be obtained,
As a result, the subsequent development of strength was suppressed, and there were problems such as the necessity of increasing the unit cement amount and the like in order to secure the design strength.

[0004] In order to cover the above-mentioned drawbacks caused by the conventional setting accelerating method, the present inventor contains gypsum and a sulfate band or alumite and sub-, bi-, or pyrosulfite. An admixture utilizing the production of ettringite (JP-A-4-160042) was proposed.

[0005] However, in this proposal, although the demolding strength can be obtained by short-time heat curing and the long-term strength can be prevented, a rapid hydration reaction of aluminum sulfate or the like is suppressed by sulfite or the like. In order to increase the production cycle, shorten the pre-curing time until heat curing,
There has been a problem that it is difficult to obtain sufficient demolding strength when the heating and holding time until demolding is shortened.

As a result of intensive studies to solve the above-mentioned problems, the present inventor has promoted the setting and hardening more rationally, and developed a strength that can be released from the mold in a shorter time from the start of the heat curing. The inventor found an excellent admixture and completed the present invention.

[0007]

That is, the present invention provides (1)
(2) a cement admixture containing gypsum, activated silica, and one or more alkali metal aluminates or alkali metal silicates; (2) cement; A cement composition characterized by containing a cement admixture.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The gypsum used in the present invention is called insoluble or hardly soluble.
Gypsum dihydrate, hemihydrate gypsum, soluble other than type II anhydrous gypsum
III-type anhydrous gypsum, effective in developing long-term strength
You. And the compounding amount is based on 100 parts by weight of cement.
And CaSO_Four6 parts by weight at the most
It is preferably at most 5 parts by weight, and the most preferred range is 1.
0 to 4.0 parts by weight. And less than 1.0 parts by weight
Long term strength elongation is small, and if it exceeds 6 parts by weight, long term
Strength developability is good, but the effect of retarding setting is large.
And it is difficult to obtain demolding strength in a short time.
Absent. It is also called insoluble or hardly soluble in gypsum.
Type II anhydrous gypsum is the most
preferable. The specific surface area of gypsum by the Blaine method
Is not particularly limited and is 2500 cm ^Two/ g or better
It is.

The activated silica used in the present invention is
For example, silica fume, fly ash fume, metakaolin, silicified wood incineration ash, Aerosil, and the like. And these are ultrafine powders one order finer than cement, and are generally known as high-strength admixtures,
Its practical compounding amount is 5 per 100 parts by weight of cement.
And 10 to 10 parts by weight.

However, in the present invention, in particular, when used in combination with an alkali metal aluminate or an alkali metal silicate, the coagulation hardening is promoted in a very small amount, and the demolding strength is exhibited in a short time in the heat curing. This has the effect of causing

Preferably, the active silica is compounded in an amount of at most 2.0 parts by weight based on 100 parts by weight of cement.
1.5 parts by weight or less is more preferable, and the most preferable range is 0.1 to 1.0 part by weight. If the amount is less than 0.1 part by weight, the effect of obtaining the demolding strength in a short time is small, and
When the amount exceeds the weight part, pseudo-coagulation tends to occur, no short-term strength increase is exhibited, and the long-term strength is reduced.

Further, the alkali metal aluminate or alkali metal silicate in the present invention means sodium, potassium or lithium aluminate or silicate. These salts are usually known as quick setting agents for cement, but are used in the present invention within a range that does not cause quick setting. It will significantly lower it.

The amount of these salts is preferably at most 1.0 part by weight, more preferably at most 0.8 part by weight, most preferably 0.1 part by weight, based on 100 parts by weight of cement.
1 to 0.5 parts by weight. If the amount is less than 0.1 part by weight, the effect of obtaining demolding strength in a short time is small even when used in combination with activated silica, and if it exceeds 1.0 part by weight, rapid setting may occur depending on the lot and type of cement. As described above, it is not preferable because not only the working time cannot be obtained but also the long-term strength decreases.

In the present invention, the mortar and concrete to which the admixture of the present invention is added are formed into a mold and subjected to heat curing. The heating curing method is not limited, such as steam, electric heating, hot water, and hot oil.However, since the concrete secondary products factory already has steam curing equipment, the method using steam curing is preferable, and the heating temperature is preferably It is 40 ° C. or higher, and the strength obtained in a short time increases as the curing temperature increases. Conversely, if the curing temperature is too high, cracks due to thermal expansion are likely to occur, so that the temperature is preferably 50 ° C. or higher, more preferably 60 to 85 ° C. It is. If the temperature is lower than 40 ° C., the strength development is delayed, so that the time until demolding becomes longer, which is not suitable for the purpose of early demolding. If the temperature exceeds 85 ° C., when the heating rate is increased, cracks due to thermal expansion are more likely to occur. It is not preferable.

The types of cement used in the present invention are various portland cements, belite cements and mixed cements obtained by mixing slag, fly ash or silica with various portland cements. It is not preferable because only the working time is shortened and the strength effect cannot be expected.

Further, in the present invention, the method of kneading mortar or concrete may be a conventional method, and there is no particular limitation. The method of adding the cement admixture is to mix the respective powder components in advance. Alternatively, the respective components may be separately added to a mixer together with other concrete materials and kneaded. Further, each component may be added to the mixer at the time of mixing mortar or concrete as a suspension using a part of the mixing water, or a part or the whole amount of the mixing water and the water reducing agent. Good thing.

[0017]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. Example 1 Gypsum,
Activated silica, alkali metal aluminate, alkali metal silicate, etc. were changed in the type and addition amount, concrete was kneaded, and φ10 × using a rod-shaped vibrator.
A test specimen of 20 cm was formed, heat curing was started 60 minutes after water injection during kneading, and the compressive strength at the time of demolding after 4 hours was measured. The results are shown in Tables 2 and 3. The fluctuation of the slump due to the addition of each component was adjusted by arbitrarily adjusting the amount of the water reducing agent, and the slump was kept constant.

[0018]

[Table 1]

The mixing of the concrete was carried out by mixing 30 liters of concrete using a planetary forced kneading mixer. Specifically, coarse aggregate, fine aggregate, cement and a mixture of each component lightly put into a mixer,
While stirring, a solution in which a water reducing agent was dissolved in mixing water was added. The slumping was adjusted by adding the water reducing agent while mixing as described above, and the total mixing time was 120 seconds after the addition of the mixing water. The mixing of the concrete was performed in a room at 20 ± 3 ° C. and RH 80%. The compressive strength test was performed on a specimen molded to φ10 × 20cm by 20 ± 3.
60 minutes after pre-curing (time from water injection to the start of heat curing) in a room at 80 ° C. and RH 80%, put in a steam curing tank, heat up to 80 ° C. in 30 minutes, and heat for 1.5 hours with steam After curing, the mold was taken out and demolded, and immediately after hot, the demolding strength (3 hours after mixing) was measured. The demolded specimen was air-dried in a room at 20 ° C. and RH 60%, and the 28-day-old strength was measured.

<Materials used> (1) Cement: Ordinary Portland cement manufactured by Denki Kagaku Kogyo Co., Ltd. (2) Sand, crushed stone: River sand, crushed stone from Himekawa water system in Niigata Prefecture (3) Water reducing agent: Naphtalin sulfone, manufactured by Denki Kagaku Kogyo Co., Ltd. Acid salt system (liquid) A. Gypsum A-1: Type II anhydrous gypsum (hydrofluoric acid generating by-product gypsum, Blaine specific surface area 4000 cm ² / g) A-2: Gypsum (reagent, specific surface area 3800 cm ² / g) A-3: Hemihydrate gypsum (dihydrate heat treatment at 0.99 ° C., Blaine specific surface area of ^{8000cm 2 / g) a-4} : soluble anhydrite (heat treatment hemihydrate at 200 ° C., Blaine specific surface area of 12000cm ² / g) B. Active silica, etc. B-1: Silica fume (BET method specific surface area of ^{25m 2 / g) B-2} : fly ash fumes (BET method specific surface area of 30 m ² /
g) B-3: metakaolin (BET method specific surface area of ^{1.4m 2 / g) B-4} : Aerosil (BET method specific surface area of ^{160m 2 / g) B-5} : chaff ash (BET method specific surface area of 1.5 m ² / g) C.I. C-1: Sodium aluminate (reagent, anhydrous salt) C-2: Potassium aluminate (reagent, anhydrous salt) C-3: Sodium silicate (reagent, anhydrous salt)

[0021]

[Table 2]

[0022]

[Table 3]

From Tables 2 and 3, it can be seen that the short-term strength is significantly increased by the simultaneous addition of the gypsum of the present invention, the activated silica, and the alkali metal aluminate and alkali metal silicate. It is shown that the long-term strength also increases when the three components are in proper amounts. Among them, if the amount of gypsum is appropriate, the short-term strength also increases, but if the amount is too large, the short-term strength tends to decrease due to the delay of the gypsum. However, the long-term strength increases as the blending amount increases, and from the balance between short-term strength and long-term strength, it is preferably 6 parts by weight or less, more preferably 1 to 4 parts by weight with respect to 100 parts by weight of cement. . Activated silica exhibits an effect of increasing short-time strength from 0.1 part by weight, and becomes more remarkable as the added amount increases.
When more than 1 part by weight is added, equilibrium is reached, and when too much, the long-term strength tends to decrease.
It is shown that the amount is preferably not more than 0.1 part by weight, most preferably 0.1 to 1 part by weight.

Further, aluminates of alkali metal, etc.
From 0.1 part by weight, the effect of increasing the short-term strength is shown, and the effect becomes more pronounced as the amount added increases, but when the amount is too large, the long-term strength tends to decrease. In addition, it is shown that if the amount exceeds 1 part by weight, there is a case where a quick connection is made.
Therefore, the preferable addition amount of the aluminate of the alkali metal is 1 part by weight or less, and it is shown that 0.1 to 0.5 part by weight is most preferable from the balance between short-term strength and long-term strength.

[0025]

According to the present invention, a cement admixture containing gypsum, activated silica and one or more alkali metal aluminates or alkali metal silicates as a main component is used in a mortar or a mortar. By mixing with concrete, it accelerates the setting and hardening of mortar and concrete, increases the rate of strength development during heating and curing, and can obtain demolding strength in a short time, and manufactures mortar and concrete with no long-term reduction in strength can do. Therefore, in the secondary concrete product factory, the production cycle from mixing and removing mortar and concrete to demolding can be shortened, and the production efficiency can be further increased.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location // C04B 40/02 C04B 40/02 C04B 103: 10

Claims (2)

[Claims] 1. A cement admixture comprising gypsum, activated silica, and one or more alkali metal aluminates or alkali metal silicates. 2. A cement composition comprising a cement and the cement admixture according to claim 1.