JPH10218644A - Acid resistant cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an acid resistant cement composition capable of utilizing a waste molten slag, etc., and aiming at the improvement of an acid resistance, a water proof property and a penetration resistance by containing a specific noncrystalline calcium silicate aluminate-based slag powder, a water glass and aggregates. SOLUTION: This acid resistant cement composition is obtained by mixing a raw material consisting of a clay, a lime stone, a burnt sewage polluting material, a burnt waste material, an industrial waste material, etc., so as to attain 0.1-1.2 molar ratio of CaO/SiO2 , melting the mixture at a high temperature, then rapidly cooling to obtain a noncrystalline calcium silicate aluminate- based slag powder having 1000-15000cm<2> /g specific surface area, and blending 10-95wt.% of the slag powder with 1-20wt.% water glass (solid portion) and 0-85wt.% aggregates so as to attain 0.05-0.40 weight ratio of the water glass/the slag powder. An acid resistant concrete product is obtained by mixing the composition with water, forming and then curing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement composition and a concrete product which can utilize waste molten slag and have excellent acid resistance.

[0002]

2. Description of the Related Art Conventionally, alkaline slag concrete and water glass concrete are known as acid-resistant concrete. Among them, alkali slag concrete is a hydraulic concrete obtained by adding an alkali metal salt or the like as a stimulant to blast furnace slag slag powder and hardening without using any cement at all. Slag used in this alkali slag concrete is blast furnace water slag slag obtained in pig iron production process, usually, CaO38～45 wt% as chemical components, SiO ₂ 33 to 35 wt%, Al ₂ O ₃ 14 to 18 weight %, MgO 4 to 8% by weight, Fe ₂ O ₃ 0.5 to 2% by weight
It is said that the molar ratio of CaO / SiO ₂ is 1.3 or more. When the molar ratio of this CaO / SiO ₂ is 1.
It is said that concrete using 3 or more blast furnace slag slag powder and water glass has stronger acid resistance than ordinary cement concrete because free Ca (OH) _{2, which} is weak to acid in the cured product, is not generated at all. ing.

On the other hand, water glass concrete is concrete obtained by adding sodium silicate or condensed aluminum phosphate as a hardening agent to water glass as a binder. Silica gel is formed and hardened in water glass concrete using a hardening agent such as sodium silicofluoride or condensed aluminum phosphate.

[0004] Since this silica gel has excellent acid resistance, water glass concrete also has excellent acid resistance.

[0005]

However, when water glass and blast furnace slag are used for acid-resistant cement, since the blast furnace slag has a large CaO content, the hardened body contains CSH (CaO) in addition to silica gel. —SiO ₂ —H ₂ O) gels are also produced in large amounts. This C—S—H gel is weak to acids, resulting in low acid resistance. The sulfuric acid is C-S
The cured product may be destroyed by expansion stress because it reacts with the -H gel to generate an expandable substance such as gypsum. Therefore, ordinary blast furnace slag containing a large amount of CaO and slag concrete using water glass are more acid-resistant than ordinary cement concrete, but are not acid-resistant for use in special applications such as acid-resistant concrete structures and acid-resistant concrete products. Is not enough.

[0006] In water glass concrete, silica gel has a problem in that although it has strong acid resistance, it is inferior in water resistance and shrinks greatly upon dehydration. Also, it is difficult for the reaction shown in the above reaction formula to completely progress to the end. For this reason, unreacted water glass and soluble metal salts remain generated, and as a result of dissolving them in water or dilute acid, the cured product becomes porous and has poor penetration resistance. Therefore, water glass concrete has a drawback of being inferior in water resistance and penetration resistance.

On the other hand, especially in large cities, various industrial wastes such as construction waste materials, including treatment of sewage sludge and municipal waste, have various problems such as securing a final disposal site. Investigation research on resource utilization is being actively conducted. Also, municipalities and equipment manufacturers are in charge of sewage sludge incineration ash and municipal waste incineration ash incinerated to reduce the volume of sewage sludge and municipal waste, and slag that has been melt-processed to further reduce the volume. We are developing effective utilization technology. However, its use has begun to be used as a raw material for roadbed materials, aggregates of blocks, blocks, tiles, bricks, etc., but the amount is insignificant, and technical, price restrictions, distribution problems, etc. There is still little effective utilization, and it is not at the stage where it is being actively utilized.

For example, regarding sewage sludge, the Ministry of Construction
Since 1975, we have been conducting research on the recycling of sewage sludge. Also, to promote the effective use of sewage sludge,
Effective sludge utilization facilities are subsidized. Furthermore, since 1988, a sewage sludge resource utilization model project has been implemented, which includes the use of sludge products (roadbed materials, soil improvement materials, etc.) in sewerage construction projects. However, despite the long years of studying its effective use, significant effective use has not yet been achieved, including sewage sludge incineration ash and garbage incineration ash, as well as molten slag that has been made into molten slag. .

Accordingly, an object of the present invention is to provide a cement composition and a concrete product which can effectively utilize waste molten slag and have the above-mentioned drawbacks and have excellent acid resistance.

[0010]

Means for Solving the Problems In view of such circumstances, the present inventors have conducted intensive studies and found that CaO / SiO ₂ such as sewage sludge or waste molten slag obtained by converting municipal waste into molten slag.
Amorphous calcium silicate aluminate slag powder having a molar ratio of 0.1 to 1.2, water glass and a cement composition containing a specific amount of required aggregate can be a concrete product having excellent acid resistance. Thus, the present invention has been completed.

That is, the present invention relates to (A) CaO / SiO
₂ to 10 to 95% by weight of amorphous calcium silicate aluminate slag powder having a molar ratio of 0.1 to 1.2,
The present invention provides an acid-resistant cement composition containing (B) 1 to 20% by weight of water glass in solid content and (C) 0 to 85% by weight of aggregate.

The present invention also provides an acid-resistant concrete product obtained by mixing and molding the acid-resistant cement composition and water.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Amorphous calcium silicate aluminate slag powder used in the present invention is CaO, SiO
₂ and Al ₂ O ₃ as main components, and various raw materials such as clay, limestone, incineration of sewage sludge, incineration of garbage, and industrial waste are adjusted to have the above-mentioned chemical components. And crushed slag obtained by rapid cooling. Here, various raw materials may be used by mixing commercially available materials, but sewage sludge incineration, garbage incineration, and industrial waste have a chemical composition within the above range even when used directly. Most of them are used from the viewpoint of economic efficiency and effective use of unused resources. That is, it is preferable to use waste melting slag such as sewage sludge incineration melting slag, refuse incineration melting slag, and industrial waste incineration melting slag. The chemical composition of waste slag that melts sewage sludge and municipal waste is 5-35% CaO and SiO
₂ 30-70 wt%, Al ₂ O ₃ 5 to 25 wt%, F
e ₂ O ₃ is 2-20 wt%, the alkali content of 1-15 wt%, phosphorus content of 0.5 to 23 wt%, a MgO is such as 2-6 wt%, most cases CaO / SiO ₂ The molar ratio is 1.2 or less.

CaO of slag powder (A) used in the present invention
The molar ratio of / SiO ₂ is 0.1 to 1.2, preferably 0.2 to 1.0, and particularly preferably 0.3 to 1.0.
0.8. When the molar ratio of CaO / SiO ₂ is 0.1
If the amount is less than the above, the hydration activity of the slag becomes extremely small, and even if a large amount of water glass is used, a cured product having a strength that can be practically used may not be obtained. On the other hand, if the molar ratio exceeds 1.2, the content of CaO becomes relatively high, so that a problem similar to that of alkaline slag concrete may occur. That is, the acid resistance is weakened, and in the presence of sulfuric acid, cracks and surface peeling are liable to occur due to expansion accompanying the formation of gypsum.

The slag powder (A) contains, in addition to the above components, one or more selected from iron oxide, alkali, phosphorus, titanium oxide, manganese oxide, magnesium oxide and halogen. Is preferred. The contents of these components are as follows: iron oxide (in terms of Fe ₂ O ₃ ), alkali (in terms of total of Na ₂ O and K ₂ O), phosphorus (in terms of P ₂ O ₅ ), titanium oxide (in terms of TiO ₂ ), Manganese oxide (M
One or more selected from nO) and magnesium oxide (MgO) are preferably about 0.1 to 50% by weight in total and / or about 0.1 to 10% by weight of halogen content.

The finer the slag powder (A), the greater the specific surface area of the powder, the faster the hydration reaction proceeds,
Concrete with high strength is preferable, but specific surface area is 1
If it exceeds 5,000 cm ² / g, the energy and time required for pulverization become enormous, resulting in lack of economy. on the other hand,
When the specific surface area is less than 1000 cm ² / g, the hydration activity is poor and the demolding strength cannot be obtained, and the acid resistance is also poor, which is not preferable. Therefore, slag powder (A)
Has a specific surface area of 1000 to 15000 cm ² / g, particularly 20
It is preferably from 00 to 8000 cm ² / g.

As the water glass (B) used in the present invention, any commercially available water glass, that is, anhydrous water glass, liquid water glass, water glass containing K ₂ O, etc. can be used. Considering the effect as a stimulant, those having a large amount of alkali, that is, those having a small SiO ₂ / Na ₂ O molar ratio are preferable. Specifically, among commercially available water glasses 1 to 3, water glass 1 is preferable. The amount of water glass to be used is 1 to 20% by weight, preferably 2 to 15% by weight (in terms of solid content) in the acid-resistant cement composition. When the amount is less than 2% by weight, the amount as the alkali stimulant is too small, so that sufficient strength cannot be obtained. When the amount exceeds 20% by weight, the viscosity of the mixture in a fresh state becomes too large,
Molding or work may be difficult. The weight ratio of water glass (B) / slag powder (A) is 0.05 to 0.4.
0, particularly preferably 0.10 to 0.30.

As the aggregate (C) used in the present invention, any aggregate having acid resistance may be used, and examples thereof include quartz rock, andesite, basalt, and crushed ceramics.
Further, the above-mentioned waste molten slag in a granular or massive form can also be used as an aggregate. The amount of the aggregate used is 0 to 85% by weight, preferably 0 to 8% by weight in the acid-resistant cement composition depending on the use.
It is preferably 0% by weight. If this amount exceeds 85% by weight, the amount of the other binder may be too small, the viscosity of the mixture in a fresh state may be insufficient, and molding may not be possible due to a dryness.

If the acid-resistant cement composition of the present invention and water are mixed and molded, a concrete product having excellent acid resistance can be obtained. Here, the mixing ratio between the cement composition and water is the same as in the case of ordinary concrete production, and is appropriately determined by a desired concrete product molding means.

As a molding method of this mixture, any of a casting method, an extrusion method, a centrifugal force method, a pressurizing method and the like may be used. The curing method includes room temperature curing, steam curing,
Any method such as autoclave curing may be used. Examples of the concrete product of the present invention include acid-resistant structures, for example, factories using acids, tanks in an acidic hot spring area, floors, walls, etc., acid-resistant backfill materials, acid-resistant concrete products, for example, chemical factories. Drainage pipes, sewer pipes and the like are mentioned.

In the present invention, by using an amorphous calcium silicate aluminate slag powder having a CaO / SiO ₂ molar ratio of 0.1 to 1.2, the C—S— Acid resistance is improved by reducing the amount of H gel. In addition, alkali such as NaOH generated by hydration of water glass becomes a stimulant of the slag powder of the present invention and is consumed. By the consumption of NaOH,
Furthermore, the hardening of the water glass will be accelerated. In other words, the water glass serves as a stimulant for the amorphous calcium silicate aluminate slag powder of the present invention, and the amorphous calcium silicate aluminate slag powder serves as a hardener for the water glass. Therefore, by using the amorphous calcium silicate aluminate-based slag powder having a molar ratio of CaO / SiO ₂ of 0.1 to 1.2, neither conventional alkali slag concrete nor water glass concrete is used. Thus, an acid-resistant cement composition having strong acid resistance, water resistance and penetration resistance and small shrinkage can be obtained.

[0022]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1 A straight concrete pipe having an inner diameter of 150 mm and a thickness of 26 mm was prepared using sewage sludge molten slag of Osaka City having a molar ratio of CaO / SiO ₂ of 1.11 (Table 1). The strength and compressive strength were measured. The composition, molding method and curing conditions in that case are as follows. That is, the composition was such that the molten slag powder having a fineness of 4500 cm ² / g was
3 kg / m ³ , No. 1 water glass 86 kg / m ³ , sand 781 kg /
m ^3, gravel 1059kg / m ^3, and water and 150 kg / m ^3.
The molding method was centrifugal force molding, and the gravitational acceleration was 3 minutes at a low speed of 3 g, 2 minutes at a medium speed of 12 g, and 6 minutes at a high speed of 30 g. Curing conditions are up to 80 ° C using steam curing.
The temperature was raised at a rate of 0 ° C./hour, and then maintained at 80 ° C. for 8 hours, followed by natural cooling. As a result, the external pressure strength is 3
It was 0.2 kN / m, and the compressive strength was 366 kgf / cm ² . The numerical value was sufficiently higher than the JIS standard value of 25 kN / m of the external pressure strength of a plain concrete pipe having a nominal diameter of 150, and was a value that would not hinder practical application.

Examples 2 to 18 Test Methods Acid-resistant cement compositions (Formulation Nos. 1 to 18 are products of the present invention, and A to C are comparative products) having the compositions shown in Tables 2 and 3 (Table 1) were used as ISO cements. According to the method of preparing the mortar, it was molded into a size of 2 × 2 × 8 cm, and after steam curing under the following conditions, it was removed from the mold to obtain a test specimen for bending, compressive strength, and acid resistance test. In the acid resistance test, the sample was immersed in 10% sulfuric acid at 20 ° C. corresponding to 10 times the volume of the test sample for 10 days, and then its weight was measured and its appearance was observed. The acid solution was replaced every two days. The results are shown in Tables 4 to 8.

[0025]

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

[Table 5]

[0031]

[Table 6]

[0032]

[Table 7]

[0033]

[Table 8]

[0034]

The acid-resistant concrete product obtained from the acid-resistant cement composition of the present invention is excellent not only in acid resistance but also in water resistance and permeation resistance and has little shrinkage.
Further, since waste molten slag obtained by melting sewage sludge or municipal waste can be used as a raw material, it is possible to effectively utilize these.

Claims (4)

[Claims] (A) The molar ratio of (A) CaO / SiO ₂ is 0.1.
10 to 95% by weight of amorphous calcium silicate aluminate slag powder of 1 to 1.2, (B) 1 to 20% by weight of water glass in solid content and (C) 0 to 85% by weight of aggregate Acid resistant cement composition. 2. The acid-resistant cement composition according to claim 1, wherein a part or all of the amorphous calcium silicate aluminate slag powder (A) is a waste molten slag. 3. The acid-resistant cement composition according to claim 1, wherein the aggregate (C) is granular or massive waste molten slag. 4. An acid-resistant concrete product obtained by mixing and molding the acid-resistant cement composition according to claim 1, 2 or 3, and water.