JPH0733274B2 - Mineral aggregate that prevents base reaction and method for suppressing base-aggregate reaction - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a non-base-reactive aggregate that substantially prevents reaction with a basic component, and a composition containing a mineral aggregate that is reactive with a basic component. Method for suppressing the base-silica reaction in water. INDUSTRIAL APPLICABILITY The present invention is extremely useful in, for example, improving the durability of a cement-based cured product and preventing surface contamination.

Conventional Technology and Problems Base-aggregate reaction has become a serious problem especially with regard to the durability of concrete structures, and the service life of concrete may be 20 years or less. The main reason for this is that the reactive silica mineral in the aggregate reacts with the base component (particularly the alkali metal component) in the cement to form an alkali-silica gel, and the gel absorbs water to expand and It is thought to deposit and form concrete cracks, damage, pollution, etc.

Conventionally, as a method of suppressing this alkali-aggregate reaction, a method of reducing the content of alkali metal components in cement, adding granulated blast furnace slag or fly ash,
A method of suppressing the alkali-aggregate reaction due to the alkali trapping effect or the dilution effect has been taken (Cement Chemistry Expert Committee Report C-2, "Literature survey on alkali-aggregate reaction", published by Cement Association, 1984). However, it is essentially difficult for such a method to suppress the reactivity of the aggregate for a long period of time, and the alkali-aggregate reaction tends to occur after one month or several years.

The main object of the present invention is to provide a mineral aggregate in which the above-mentioned base-aggregate reaction is substantially prevented, and a method for suppressing the base-aggregate reaction in a hydraulic cement composition.

Means for Solving the Problems The present inventors have found that the reactivity of a silicate-based aggregate that is reactive with a basic component (typically, an alkali component) depends on the reactivity of the silica component of the silicate (for example, It was noted that the main cause is the reactivity of the silica component due to radicals or ions. Unexpectedly, by bringing ozone-containing water (hereinafter sometimes referred to as O ₃ water) into contact with the silicate-based aggregate,
It was found that the surface structure of the aggregate particles in contact with the basic component is modified and stabilized in the long term.

Therefore, according to the present invention, a mineral substance which substantially prevents a reaction with a base, which is obtained by contacting a mineral substance reactive with a basic component with ozone in the presence of water to modify the reaction site of the aggregate. A sex aggregate is provided.

As a method of bringing the above-mentioned ozone into contact with the aggregate particles, a method of immersing in ozone-containing water (O ₃ water), a method of spraying O ₃ water, and the like are typical. When the aggregate is mixed with the cement-based material, the aggregate modified in advance with ozone may be used, or the ozone water may be added or used when the admixture water of the inorganic cement is added. .

Accordingly, according to the present invention, a mineral aggregate that is reactive with a basic component is used as an aggregate for cement, which is treated with ozone in the presence of water, and is used as a cement aggregate for cement. A method for suppressing a base-aggregate reaction is provided. Further, when mixing a cementitious material containing a mineral aggregate that is reactive with a basic component, a hydraulic cement and water, it is characterized in that 0.02 wt% or more ozone of the water component is present. Base of hydraulic cement-based composition
A method for suppressing an aggregate reaction is provided.

Detailed Description of the Invention (1) Examples of Concrete Aggregates Reactive with Basic Components As reactive aggregates, reactive silica minerals such as opal, cristobalite, tridymite, volcanic glass, and And / or those containing chalcedony and the like. Generally, there are igneous rock aggregates, and pyroxene andesite is typical. Blast furnace slag, coarse aggregate, fine aggregate, finely ground slag and the like, which are usually granulated blast furnace slag, also contain the above components and are particularly reactive when a small amount is used. In addition, ground ceramics such as ceramics and ground glass aggregate are also reactive. Sea sand is also a highly reactive aggregate. In the present invention, it is of course possible to use these reactive aggregates in combination with other aggregates.

(2) Ozone As ozone used in the present invention, ozone obtained from an ozone generator utilizing silent discharge or electrolysis can be advantageously used. For example, ozone is inexpensively obtained by silently discharging oxygen or dry air with an AC voltage.
The concentration (% by weight) of the O ₃ water used (which may be an aqueous or supersaturated aqueous solution of ozone or ozone-containing water such as ozone-containing steam) is generally about 0.02% or more and about 0.02%.
Is in the range of about 3%, usually about 0.05 to 2%, and even higher concentration is possible in the case of ozone-containing water vapor. The ozone supersaturated aqueous solution is obtained by introducing ozone or an ozone-containing gas into water under pressure. The above-mentioned ozone-containing water vapor is obtained by mixing ozone or an ozone-containing gas with, for example, saturated water vapor, and the ozone concentration with respect to water can be as high as about 20 to 30%. When contacted treated with O ₃ water, O ₃ water immersion (e.g. more than several tens of minutes at 0.5% to 2% concentration) or, or O ₃ water can be sprayed. When adding or using O ₃ water when adding mixed water to the cementitious material, the O ₃ water concentration is about 0.02% or more, preferably about
0.05% or more is suitable. When a supersaturated aqueous solution of O ₃ or water vapor containing ozone is used, it is generally preferable to seal the container for the contact treatment. Further, the mineral aggregate to be subjected to contact treatment is placed in a container, and (a) ozone-containing water vapor is continuously introduced, or (b) water is added to immerse or wet the substance, and then the container is placed in the container. It is also a preferable treatment method to continuously introduce ozone or an ozone-containing gas.

In these cases, it is generally preferable that the treated mineral aggregate is washed with water after the contact treatment, but it may not be washed. In order to reduce the action of O ₃ , it is also desirable to use a small amount (for example, 2/3 or less equivalent to ozone equivalent of O ₃ water) of a reducing compound (for example, sulfite or nitrite) together. It is a mode.

(3) Concrete Examples 1 to 3 As an aggregate, pyroxene andesite which is alkali silica reactive 20
% And 80% by weight of the less reactive river sand were used. The pyroxene andesite aggregate is untreated (Example 1),
The container was sealed and immersed in an excess amount of 1.5 wt% O ₃ water for 1 week (Example 2), and the container was immersed in O ₃ water for 1 week and washed with water (Example 3).

In accordance with ASTM C 227-81, 2.25 parts by weight of aggregate (particle size 0.15 to 4.75 mm) is used per 1 part by weight of cement, and the amount of water is adjusted to 105 to 120 by table flow to prepare mortar. did. After demolding the mortar bar test piece (25 × 25 × 285 mm), the temperature was maintained at 37.8 ± 1.7 ° C. and R100%, and the length change was measured by a comparator. The cement used was ordinary Portland cement, and its total alkali content (R ₂
O) 0.49% for terms of Na ₂ O _{(Na 2 O: 0.3, K} 2 O: 0.29). In order to change the amount of R ₂ O, reagent grade NaOH and KOH were added in the above ratio to make R ₂ O 1.38%. The results of length measurement are shown in the table below.

The above results are based on JIS A5308 Annex 8 similar to the above ASTM.
It is also clear from the criteria of the (mortar bar method): “If the average expansion coefficient is less than 0.100% after 6 months, it is harmless, and if it is 0.100% or more, it is harmful”. That is, Example 1 (Comparative Example) is extremely harmful, and Examples 2-3 are completely harmless.

Action and effect Base-aggregate reaction in a composition in which a base component and an aggregate that is reactive therewith coexist (especially alkali-silica reaction of aggregate)
Was extremely detrimental to the durability and staining of the composition, but was essentially unsolved. The operation of the present invention is
Although not fully clarified, by contacting the reactive aggregate with O ₃ -containing water, the surface glass structure, which is a reactive site of the aggregate particles, is modified into a hydrous gel-like substance, It is thought to achieve the effect that reactivity is effectively suppressed. For example, the reactive silica component is typically ≡Si-O.
However, in this case, it is considered that O ₃ water acts to modify the structure to a stable ≡Si-OH structure for a long time and the reactivity is sufficiently suppressed. However,
The present invention is not bound by such a representative theory.

The non-reactive modified aggregate according to the present invention is extremely useful for long-term stabilization of a composition coexisting with a base component (particularly an alkali component). Typically, it is effective for long-term stability of hardened cementitious materials such as mortar and concrete. Furthermore,
The effect of facilitating the use of admixtures, additives, etc. having a high content of alkali components in the composition is also achieved. The ozone-containing water used in the present invention, unlike other additive chemicals, becomes substantially water after the action, is non-toxic, and has the effect that the residual components do not adversely affect the quality and strength of the product.

 ─────────────────────────────────────────────────── ─── Continuation of the front page Examiner Noriko Suzuki

Claims (3)

[Claims] 1. A mineral aggregate that is reactive with a basic component is contacted with ozone in the presence of water to modify the reaction site of the aggregate, which substantially prevents the reaction with a base. Mineral aggregate. 2. A hydraulic cement-based composition, characterized in that a mineral aggregate that is reactive with a basic component is contacted with ozone in the presence of water to be used as an aggregate for cement. A method of suppressing the reaction of bases and aggregates of materials. 3. When mixing a mineral aggregate, a hydraulic cement, and a cementitious material containing water which are reactive with a basic component, 0.02% by weight or more of ozone of the water component is allowed to be present. And the base of the hydraulic cement-based composition
Method of suppressing aggregate reaction.