JPS632845A - Concrete admixing agent and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a concrete admixture that is mainly used for concrete, mortar, and cement, and particularly for improving the mechanical strength and waterproofness of concrete, mortar, etc. This is a proposal regarding a concrete mixture suitable for concrete mixing and its manufacturing method.

Such concrete admixtures are used in addition to concrete, as well as mortar and cement, to impart or improve desired properties. Among these, waterproofing admixtures (hereinafter simply referred to as "waterproofing agents") promote the hydration reaction of cement, thereby filling voids with cement gel and creating water impermeability or interlocking properties inside mortar and concrete. It is used as a material that prevents water absorption and permeation in mortar and concrete due to its ability to form a layer or membrane.

(Prior art) Conventionally, waterproofing agents have been made of naturally occurring pozzolanic substances such as clay and clay, flyanche produced as a by-product in thermal power plants, fine particulate silica hume produced as a by-product during the production of ferrosilicon, calcium chloride, and silica. Acid sodium, higher fatty acids, liquid paraffin (paraffin emulsion)
, water-soluble polymers, etc. were used.

(Problems to be Solved by the Invention) Pozzolanic substances such as naturally occurring white clay and slate in the above-mentioned conventionally used mixtures for reducing water permeability have physical and chemical problems because they are natural products. There are many variations in physical properties, and the effect when added to mortar or concrete is inconsistent, so there was a problem in that properties had to be tested before use. This includes:
For example, there are even cases where the properties of the same mine change when the mining area changes slightly.

In addition, in the case of flyanche, the reaction rate is slow and it takes several months for the effect to become apparent, while silica hume has excellent performance as a waterproofing agent, but its supply sources are scarce and it is expensive. There was a problem.

Furthermore, in the case of low calcium chloride, sodium silicate, etc., although they exhibit waterproof properties, they are expensive and have the problem of lowering the strength of mortar and concrete.

The present invention aims to overcome the problems of conventional waterproofing agents as described above, and is particularly effective in improving the mechanical strength and water impermeability of mortar and concrete, and is also effective in preventing alkaline aggregate reactions. The purpose is to provide an effective concrete admixture and its effective manufacturing method.

(Means for resolving the problems) The above objectives will be reliably achieved by adopting measures that are based on the following matters. That is, the present invention provides a concrete admixture having a coating layer of silicic acid sol and/or silicic acid gel obtained by neutralizing an alkali silicate with an acid on the surface of a silicic acid-containing substance containing soluble silica. , and having a coating layer of silicic acid sol and/or silicic acid gel obtained by neutralizing an alkali silicate with an acid on the surface of a silicic acid-containing substance containing soluble silica,
Furthermore, we propose a concrete admixture made by adhering fine particulate silicic acid to the surface of the coating layer.

As a means for obtaining each of the above admixtures, the present invention first adds an alkali silicate to a silicic acid-containing substance containing soluble silica, and then adds an acid to the surface of the silicic acid-containing substance. It is characterized by neutralizing the alkaline content in the previously added alkali silicate, forming a layer of silicate sol and/or silicate gel on the surface of the silicate-containing substance, and drying if necessary. A method for producing a concrete admixture, and first, adding an amount of acid sufficient to neutralize the alkaline content in the alkali silicate to produce a silicate sol and/or a silicate gel. By adding the already obtained silicic acid sol and/or silicic acid gel to the silicic acid-containing material, the silicic acid sol and/or silicic acid gel is added to the surface of the silicic acid-containing material containing soluble silica. We propose a method for producing a concrete admixture characterized by coating with acid gel and drying if necessary.

(Function) The "silicic acid-containing substance containing soluble silica" constituting the admixture of the present invention includes pozzolanic natural minerals such as white clay, clay, fly ash, silica-containing slag, etc. The average particle size is preferably about 1 to 100 μm. Normally, natural minerals can be used as is, but they may be crushed if necessary.

In terms of ingredients, amorphous high silica (containing a large amount of soluble silica) is preferable. This is because so-called high-silica admixtures with a high silica content increase the strength and water resistance of concrete.

The reason is that the amorphous silica (soluble silica) contained in this admixture combines with free CaO in the concrete,
A stable insoluble substance called 2CaO-mSiO2/nHJ is created (called a pozzolanic reaction), which strongly binds between concrete particles, increasing the strength as a result, and this stable substance also eliminates voids caused by breathing after water has drained out. It is believed that by decreasing the amount of water, the voids are filled and dense concrete is formed, which increases its water impermeability.

However, this pozzolanic reaction is very slow with naturally occurring amorphous silica, fly ash, and silica in slag, and requires a certain temperature and long time to complete the reaction, so improvements are desired.

On the other hand, if alkali silicate (sodium silicate), which is used as a waterproofing agent, is mixed into concrete, sodium silicate (sodium silicate)
The Na2O part in mNa, o・n5io, ) is CaO
This is not preferable for use in concrete because it replaces mcao·n5iO□, which liberates alkali and causes an alkali-aggregate reaction, causing the concrete to collapse.

Therefore, the present inventors conducted research to solve the above-mentioned bottlenecks of the characteristics of the silicic acid substance and the silicate salt, and found that the alkali silicate can be neutralized with an inorganic acid (such as sulfuric acid, hydrochloric acid, etc.) or an organic acid. They found that good results could be obtained by preparing active sol or gel silica either beforehand or afterward, and coating it on the surface of natural pozzolanic materials, fly ash, or slag. . The concrete obtained by adding the admixture thus obtained was found to have high strength and excellent water impermeability.

Sols and gels produced in the process of neutralizing alkali silicate are composed of colloidal particles, and the surfaces of these colloidal particles have a large amount of silanol groups (-Si-OH). Therefore, when the surface of a silica-containing material such as pozzolan is coated with this sol or gel, the surface is activated. Note that when such silanol groups are heated (especially at temperatures exceeding 200°C), they undergo a dehydration reaction, forming siloxane bonds with low chemical activity (St-0
-3t), so it is desirable to carry out the drying treatment at 200°C or lower.

In short, the present invention is characterized in that a coating layer of silicic acid sol and/or gel is formed on the surface of a silica-containing substance containing soluble silica, and the coating agent is prepared in advance to form a core layer. For example, alkali silicate neutralized with an inorganic or organic acid such as sulfuric acid, hydrochloric acid, nitric acid, or phosphoric acid is used. In this case, the pH of neutralization is 9-4
(9: Sol>7> Gel: 4). Regarding the concentration, it is preferable to use a silica sol suitable for coating, considering the mixing during the next surface coating, but even with silica gel, the surface can be coated sufficiently uniformly by using a mixer. Note that it is desirable to dry the product after this coating at a temperature of 200° C. or lower considering the surface condition.

Regarding surface coating, in addition to the method described above, it is also possible to first mix a predetermined amount of alkali silicate with a silica-containing substance and then neutralize it by adding the same acid as above, which is the same as a concrete admixture. Demonstrates the effect of

In the present invention, the mixing ratio of the alkali silicate and the silica-containing substance has no effect when the alkali silicate added is 0.1 wt% or less with respect to the silica-containing substance.
Even if it is added in an amount of 40 wt% or more, the effect hardly changes and it becomes more expensive. When applied to cement, a suitable upper limit addition amount is about 20-t%.

In addition, fine particulate (approximately 10 to 20 mμ) amorphous silica such as white carbon or silica fume is attached to the surface of the above-mentioned mixture of the present invention that has been coated.
By sprinkling), the strength and waterproofness can be improved.

In addition, in the present invention, even if a gel-like material is dried and pulverized and mixed with a silica-containing substance (coated on the surface), an effect exceeding that of the prior art can be expected.

(Example) As an example of the present invention, first, naturally produced clay silicate (71.5% total silica, 47.3% soluble silica, average particle size 10
μ), a gel obtained by diluting JIS No. 3 water glass with 10 times the amount of water and neutralizing it to pH 7 with sulfuric acid was added to 100 parts of the above clay to 2.5 parts of water glass ( Sample A)
and 5 parts (sample B) were mixed, dried at 100°C, and crushed to obtain a sample.

Next, JIS diluted 10 times with water to 100 parts of white clay.
3 glass with water glass etc. 2.5 parts (sample C) and 5.0 parts
Part (Sample D) was mixed, and sulfuric acid (10% sulfuric acid) necessary for neutralizing to pH 7 was added and mixed, and then dried and crushed to obtain a sample.

Sample E uses fly ash (total silica 58.6%, soluble silica 33.7%, average particle size 23μ) instead of the silicate clay.

F, and in addition, sample A was made of white clay with silica hneem (total silica 90
．． 7%, soluble silica 72.4%, average particle size 0.3m
Sample G was obtained by adding and mixing 5 parts of silica hneem with sample E, and sample H was obtained by adding 5% of silica hneem to sample E.

As comparative examples, an example using untreated silicate clay was designated as I, and an example using untreated fly ash was designated as J.

For each of the above samples (A-J) shown in Table 1, J
Table 2 shows the test results for compressive strength and water permeability when added to mortar according to the IS A1404 test method for cement waterproofing agents for construction.

As can be seen from this table, for example, when we look at test floor 1, the compressive strength after 6 months is 22 kgf/cm2 higher than that of test floor 11, which is the standard product, and the water permeability is also 4 g higher. The admixture of the present invention showed better results in both strength and waterproofness.

In addition, good results were obtained with either of the two methods for samples A, B and C, D, and the method of pre-neutralization with water glass (
It was found that either method A or B), in which water glass is added after neutralization, may be used.

(Effects of the Invention) As explained above, according to the present invention, when the obtained admixture is applied to concrete, the coated active silica first undergoes a pozzolanic reaction, improving strength and water permeability, and The silica-containing substances used in this process also react over a long period of time, resulting in concrete that is strong and water-resistant from short to long term.

Claims (1)

[Claims] 1. On the surface of a silicic acid-containing substance containing soluble silica,
A concrete admixture with a coating layer of silicic acid sol and/or silicic acid gel. 2. On the surface of a silicic acid-containing substance containing soluble silica,
A concrete admixture comprising a coating layer of silicic acid sol and/or silicic acid gel, and further having fine particulate silicic acid adhered to the surface of the coating layer. 3. First, an alkali silicate is added to a silicic acid-containing substance containing soluble silica, and then an acid is added to remove the previously added alkali silicate present on the surface of the silicic acid-containing substance. A method for producing a concrete admixture, which comprises neutralizing the alkali content of the silicic acid-containing substance to form a layer of silicic acid sol and/or silicic acid gel on the surface of the silicic acid-containing substance. 4. First, an amount of acid sufficient to neutralize the alkaline content in the alkali silicate is added to produce a silicate sol and/or a silicate gel, and then soluble silica is added. A method for producing a concrete admixture, comprising coating the surface of a silicic acid-containing substance with the previously prepared silicic acid sol and/or silicic acid gel.