JPH04164845A - Cement admixture and cement composition - Google Patents

Abstract

PURPOSE:To suppress neutralization of cement cured body and improve development of strength thereof by blending calcium aluminosilicate glass with an inorganic sulfate and reactive silica based substance. CONSTITUTION:100 pts.wt. calcium aluminosilicate consisting of 60-30wt.% CaO, 20-60wt.% Al2O3 and 5-25 wt.% SiO2 and having >=50wt.% vitrification ratio and >=3000cm<2> blaine's specific area is blended with 50-500 pts.wt. inorganic sulfate (e.g. II type anhydrous gypsum) having >=3000cm<2> blaine's specific area and 20-300 reactive silica based cement (e.g. active silica) having <=5mum particle diameter to provide the cement admixture. Then 100 pts.wt. cement is blended with 10-50 pts.wt. of the above-mentioned admixture and setting controller, aggregate, water-reducing admixture, etc., to provide the cement composition.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to cement admixtures, particularly to cement admixtures and cement compositions used for preventing deterioration and repairing cement structures.

(Conventional technology) In recent years, the deterioration of cement structures has become a social problem.
There is an urgent need to establish countermeasures and repair methods.

The main causes of deterioration of cement structures are: (1) Rust formation of iron in cement structures due to neutralization of hardened cement.

(2) Occurrence of cracks due to drying shrinkage.

(3) Deterioration due to chemical action of cement.

(4) Damage caused by freeze-thaw effects.

(5) Rust of iron in cement structures due to salt content or intrusion of salt.

(6) Deterioration due to alkaline aggregate reaction.

(7) Damage caused by repeated or sustained loading.

There are a wide variety of things.

(Problems to be Solved by the Invention) Among the above-mentioned problems, the present inventors particularly aimed at suppressing the carbonation of hardened cement and shortening the repair work period (by improving strength development). As a result of various studies, it was found that a specific composition was effective, and the present invention was completed.

(Means for Solving the Problems) That is, the present invention is a cement admixture characterized by comprising calcium aluminosilicate glass, an inorganic sulfate, and a reactive siliceous substance as main components, and furthermore, the cement admixture This is a cement composition characterized by containing wood and cement as main components. The present invention will be explained in detail below.

Calcium aluminosilicate glass (hereinafter referred to as C) according to the present invention
AS glass) has a composition range of CaO:60
-30% by weight A1□03: 20-60〃 5iOz: 5-25〃 are preferred, more preferably CaO: 55-30% by weight Al2O3: 30-60〃 SiO□ = 10-20〃. If CaO is less than 30% by weight or Alz03 is more than 60% by weight, rapid hardening will be poor;
exceeds 60% by weight, or A1□03 exceeds 20% by weight
If it is less than that, instantaneous setting will occur even if a large amount of setting modifier is added, which is not preferable from the viewpoint of workability. Also, SiO□ is 5
If it is less than 25% by weight, no long-term strength increase can be expected, and if it exceeds 25% by weight, the initial strength will be low. In addition,
General industrial raw materials include MgO, FezO3, TiO2, K
It naturally contains impurities such as zO and NatO, and
Since these impurities expand the vitrification region of the Ca0-Al□03-5iO7 system, their presence in an amount of less than 10% by weight is preferable, and there are no problems with rapid hardening, workability, long-term strength growth, etc. . - It is preferable to add alkali nitrate (NaNO3, KNO3, etc.), calcium fluoride (CaFz), borax, etc., which are fluxing agents for glass, because they lower the melting point of the glass.

The glass referred to here is what is commonly referred to in the field of glass, that is, "a material that exhibits a glass transition point." Note that it is not necessary that all of the material is glass, and there is no problem as long as the vitrification rate is 50% by weight or more. It is more preferably 70% by weight or more, still more preferably 80% by weight or more. If it is less than 50% by weight, problems arise in terms of early strength.

In addition, the method for measuring the vitrification rate is that the glass of the present invention is
After heating at 000°C for 2 hours (h), it was slowly cooled at a cooling rate of 5°C/min (m), and the area S0 of the main peak of the crystalline mineral was determined by powder X-ray diffraction method. The vitrification rate χ was determined from the main peak area S of .

CAS of χ (weight%) = 100 x (1--) or more
The composition of glass is completely different from the composition of granulated blast furnace slag, which is produced as a by-product in metallurgy or metal smelting, and the present invention is not derived from the composition of granulated blast furnace slag. By the way, the average chemical composition of granulated blast furnace slag is Ca
b: 40-43% by weight, MgO: 5-8% by weight, Al2
O,: 13-15% by weight, and SiO2: 31-35
Weight%.

Moreover, the CAS glass of the present invention is not derived from alumina cement. That is, the amount of 5i02 in normal alumina cement is less than 5% by weight [Jun Kasai, Concrete Engineering, Vol. 22, No. 8, p. 67 (1984)
)), and the vitrification rate does not exceed 25% (
Published by Academic Press Incorporated, London, 1964, H, F, Vl, T.
The Chemistry of Cement (Th
e Chemistry of Cement), Volume 2, Page 16].

Raw materials for the CAS glass according to the present invention include quicklime (Cab) and slaked lime (Ca (01
()Z:L, limestone (CaCOa), etc. can be used, alumina, bauxite, diasbore, feldspar, clay, etc. can be used as AIZ03 raw materials, and silica sand, white clay, silica can be used as SiO□ raw materials. Algae etc. can be used. Alternatively, it can also be achieved by supplementing relatively inexpensive blast furnace slag with CaO-based raw material and A1□03-based material.

After blending the above CaO raw materials, A1□03 raw materials, and SiO□ raw materials in a predetermined ratio, they are melted using a direct current melting furnace or high-frequency furnace, and the resulting melt is heated using compressed air or high-pressure water. It is manufactured by blowing it away or pouring it into water. Alternatively, CAS glass can also be produced by melting it in a rotary kiln and rapidly cooling it.

The finer the fineness of the CAS glass, the better the reactivity will be, and in particular, the finer the finer the powder, the more the plane specific surface area will be 3.000 a.
112/g or higher is better.

The inorganic sulfate according to the present invention refers to an alkali metal or alkaline earth metal sulfate, and preferable examples thereof include anhydrous, semi-hydrated, and double calcium sulfates. Particularly preferred are those that are sparingly soluble or insoluble. The fineness of inorganic sulfate is usually 3,000 an”/g.
The above is preferable.

The amount of inorganic sulfate used is 50 to 500 parts by weight, preferably 100 to 300 parts by weight, based on 100 parts by weight of CAS glass. If it is less than 50 parts by weight, the rapid hardening is insufficient, and if it exceeds 500 parts by weight, the dimensional stability of the cement composition may deteriorate.

The reactive siliceous substances according to the present invention include activated silica, opalescent silica, silica hume, colloidal silica, diatomaceous earth, Aerosil, silica gel, vitreous No. 1.2 and 3.4 sodium silicate, crystalline meth There are sodium silicate-based substances such as sodium silicate, sodium orthosilicate, and sodium pyrosilicate, and it is possible to use one or more of these. Among them, sodium silicate substances have a composition with a molar ratio of Na
2O/SiO□=0.1 to 5.0 is preferable, 0゛, 2
-1.1 is more preferable, and it can be used in powder form or solution form.

The particle size of the reactive siliceous material is not particularly limited, but it is usually preferably 5 microns or less.

The amount of reactive siliceous material used is 20 to 300 parts by weight, preferably 50 to 2 parts by weight, per 100 parts by weight of CAS glass.
00 parts by weight. If the amount used is other than this, a favorable effect in terms of suppressing carbonation will not be obtained.

The cement admixture of the present invention includes various Portland cements such as normal, early strength, super early strength, and moderate heat, as well as silica and
It can be used by mixing with various mixed cements containing blast furnace slag and fly ash.

The amount of cement admixture used is preferably 10 to 50 parts by weight per 100 parts by weight of cement. If it is less than 10 parts by weight, strength development is low, which is not preferable in terms of shortening the construction period.On the other hand, if it exceeds 50 parts by weight, it is not only economically disadvantageous but also undesirable from the viewpoint of workability.

The cement admixture and cement composition of the present invention include:
It is possible to use various additives in addition to those mentioned above. For example, setting modifiers, aggregates such as silica sand, natural sand and gravel, fibrous substances such as glass fibers, carbon fibers and steel fibers, and polymer emulsions (latex).
, colorants (pigments), AE agents, water-reducing agents, AE water-reducing agents, fluidizing agents, rust preventive agents, water-inseparable admixtures such as methyl cellulose, thickeners, water retention agents, calcium chloride, sodium silicate, etc. One or more of waterproofing agents, foaming agents, foaming agents, calcium-containing compounds such as calcium hydroxide, antifreeze agents, etc. can be used in combination in amounts that do not substantially impede the object of the present invention. .

Specific examples of coagulation modifiers include chlorides such as calcium chloride, ferric chloride, and aluminum chloride; aluminates such as sodium aluminate and potassium aluminate; carbonates such as sodium carbonate and potassium carbonate; and sodium hydroxide. ,
Hydroxides such as calcium hydroxide, inorganic salts such as silicofluorides such as zinc fluorosilicide, magnesium fluorosilicide, sodium fluorosilicide, and citric acid, gluconic acid,
Organic acid compounds such as tartaric acid, or their calcium salts, sodium salts, and potassium salts are available, and they may be added alone or in combination of two or more thereof.

The amount of the setting modifier used is usually about 0.1 to 20 parts by weight per 100 parts by weight of CAS glass.

Any existing stirring device can be used as a mixing device for producing each composition of the present invention, such as a tilting mixer, an omnimixer (manufactured by Chiyoda Giken Industries, Ltd.), a type mixer, and a Henschel mixer. , Nauta mixer, etc. can be used. In addition, each material may be mixed at the time of construction, or some or all of the materials may be mixed in advance.

Regarding the actual method of applying the cement composition of the present invention,
It is sufficient to follow conventional mortar or concrete construction methods, and no special equipment or construction methods are required.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Commercially available special grade reagents CaCO3, Al2O3, and 5iO
z was mixed, 300 g was placed in a carbon crucible, heated and melted at about 2.000° C. in a high frequency furnace, and then quenched in water to synthesize 14 types of glasses A to N shown in Table 1. In addition, as shown in the remarks column, A, B, HlJ, K
Since ,N was not within the vitrification region of the Ca0-Al203-5ing system, 1% by weight of CaF2 was added to the outside, and vitrification was performed by rapidly cooling the melt diameter. Also,
M and N are comparative examples other than the present invention. Each of these CAS glasses has a plane specific surface area of 4,000 cn”7
It was ground to a weight of g. The analysis results are also listed in Table 1.

Next, a mixture having the composition shown in Table 2 was prepared, and the compressive strength and carbonation depth were measured (W/C was 60%).

(Materials used) Cement: Ordinary Portland cement manufactured by Andes Cement Co., Ltd. Inorganic sulfate: ■-type anhydrite, Blaine specific surface area 5.
900 countries 27g Reactive siliceous substance a Rainbow cahuum, a by-product during the production of ferrosilicon b: Sodium silicate (reagent) C: Sodium metasilicate (reagent) d Niopal silica e Rainbow silica gel (reagent) Aggregate = No. 8 silica sand (measurement) Method) Compressive strength: Based on JIS R5201. However, the curing conditions were a temperature of 20° C. and a humidity of 65% RH.

Carbonation test: According to the test method of "Premix polymer cement mortar for initial repair" of the Housing and Urban Development Corporation construction materials test items, the kneaded material was placed on a mortar base plate of 10 x 10 x 10 cm in thickness. 5 n was applied to make a test specimen, and it was cured for 14 days under standard conditions, at a temperature of 30°C and a humidity of 60% RH, CO
After being kept on a shelf in an accelerated neutralization test chamber at a 5% z ta degree for 30 days, neutralization was determined by a color reaction with a 1% phenolphthalein solution.

Measurement of carbonation depth is carried out for each specimen. 6 locations, total of 3 test specimens The average value of 18 locations was determined.

(Effects of the Invention) According to the present invention, a cement composition that has good strength development properties and is less susceptible to carbonation can be obtained.

Patent applicant Denki Kagaku Kogyo Co., Ltd.

Claims (1)

[Claims] 1. A cement admixture characterized by containing calcium aluminosilicate glass, an inorganic sulfate, and a reactive siliceous substance as main components. 2. A cement composition comprising the cement admixture according to claim 1 and cement as main components.