JP2003246657A - Hardening accelerator for cement containing incineration ash of sewerage sludge and cement composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hardening accelerator for cement with the incineration ash of sewerage sludge added in which the increase of the unit water content of the cement is suppressed, and the reduction of the initial and long term strength of the cement is improved, and to provide a cement composition. <P>SOLUTION: The hardening accelerator for cement containing the incineration ash of sewerage sludge essentially consists of quicklime and/or slaked lime. The cement composition is obtained by blending the incineration ash of sewerage sludge in 10 to 50 pts. and a quicklime and/or slaked lime-containing material in 1 to 15 pts. by an amount expressed in terms of free lime (f-CaO) (the total of the content of the f-CaO content and a value obtained by converting Ca(OH)<SB>2</SB>into an f-CaO content) to 100 pts. of cement. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hardening accelerator for cement, and more specifically, it promotes setting hardening of cement paste, mortar or concrete using incineration ash of sewer sludge, and reduces deterioration of long-term strength. A hardening accelerator for cement and a cement composition to which incineration ash of sewer sludge is added.

[0002]

2. Description of the Related Art If a large amount of sewer sludge, which is generated permanently and is not heat-treated, is filled up, there are problems such as groundwater pollution due to elution of harmful metals.
To be effectively used as an aggregate or extender for cement paste, mortar or concrete (hereinafter simply referred to as concrete), building materials, etc. by melting at high temperature of 0 ° C, vitrifying (called slag) and crushing. Is being considered. Furthermore, in a new firing method in which a slurry whose moisture content is adjusted is blown into a high-temperature furnace at 1400 to 1500 ° C together with air having a high oxygen concentration, dehydration to melting is instantaneously performed, and a spherical shape with a diameter of several microns is used. Fine glass beads (called molten powder) are produced and can be effectively used as an extender for concrete and building materials without being crushed. The Tokyo Sewer Bureau is promoting joint research with concrete product companies. (Weekly sewer information, No. 1181, issued January 25, 2000). By vitrifying, even if it is a fine powder, the unit water content of concrete does not increase, so it has preferable properties as an extender for concrete, but since it becomes inactive, it is not possible to expect an increase in strength due to the pozzolan activating action. And, raising the firing temperature until it becomes vitrified (until it melts) requires the above-mentioned high temperature for both slag and molten powder, which leads to an increase in equipment construction cost and maintenance cost, which is uneconomical. . Therefore, in consideration of economy, the firing temperature is lowered to the extent that it does not melt,
The thing burned at 0 degreeC is only called an incineration ash, and this incineration ash is used for some concrete products.

[0003]

However, the secondary particle form of this incinerated ash becomes bulky (does not take the form of particles), and when added to concrete, the unit water amount is remarkably increased and the strength is lowered. There is a problem that only a small amount of about 5% can be added to cement.
Furthermore, in the incineration ash, the pozzolanic activity increases when the firing temperature is lowered, but as a basic problem, the incineration ash contains 5 to 1 of a phosphoric acid compound which is a component that delays the setting and hardening of cement.
Since it is contained in a large amount of 5%, the development of early and long-term strength of the cement is hindered, and this point is also a problem from the purpose of utilizing a large amount of incinerated ash. In order to solve the problem of the phosphate, a method of extracting the phosphate in the sewer sludge before firing by extracting with caustic soda is also proposed, but as in the present invention, the phosphate There is no proposal for a dedicated curing accelerator that accelerates the setting and hardening of the cement itself containing the incinerated ash containing as it increases the initial strength and reduces the decrease in long-term strength. On the other hand, a large number of inorganic compounds and organic compounds have been conventionally known as setting hardening accelerators for cement. Inorganic compounds include classical chlorides such as calcium chloride, alkali metal or alkaline earth compounds of nitrates or nitrites, alkali metal or aluminum compounds of soluble sulfates or sulfites, alkali metal or alkalis of thiosulfates. There are earth compounds and the like, and further, alkali metal carbonates, bicarbonates, silicates, aluminates, etc. are known as cement setting agents which are stronger than accelerators. However,
These accelerators have a small effect of accelerating the setting and hardening of the cement containing the incinerated ash even if the added amount is increased,
Moreover, the effect of improving the decrease in long-term strength is poor. Further, a method of using slaked lime or the like for early demolding of a concrete product for steam curing has already been proposed (Japanese Patent Publication No. 57-1186), but this method is an insoluble anhydrous gypsum and slaked lime in cement and / or Molded concrete with soft-calcined quick lime added, 35-35% higher than the kneading temperature
It is to cure by steam at a high temperature of 55 degrees to obtain demolding strength in a short time, and describes whether or not there is an effective hardening promoting effect for those having a strong setting retarding action such as incineration ash. There is no. The present inventor, as a result of diligent research for solving the above-mentioned problems of sewer incineration ash, in addition to a method for suppressing an increase in the unit water amount of cement using incineration ash of sewer sludge, among many hardening accelerators. It was found that the specific component of 1 improves the deterioration of initial and long-term strength of the cement to which the incinerated ash is added, and the present invention has been completed.

[0004]

[Means for Solving the Problems] That is, the present invention is a hardening accelerator for cement containing incineration ash of sewer sludge containing green ash and / or slaked lime as a main component. 10 to 50 parts of incinerated ash of the above and free lime (f-Ca
O) conversion amount (f-CaO amount and Ca (OH) ₂
The cement composition is characterized by being mixed in an amount of 1 to 15 parts by total of the values converted into the amount).

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.

The incineration ash of the sewer sludge of the present invention (hereinafter simply referred to as "incineration ash") is a wet cake obtained by dehydrating the sewer sludge or a slurry having an adjusted water content, usually from 800 to
Although it is obtained by firing at 850 ° C., it is basically a powder fired at a temperature at which it does not melt. In the present invention, 10 to 50 parts of incinerated ash is mixed with 100 parts of cement. If the content of incinerated ash is less than 10 parts, it is too small to digest a large amount of sludge, and if it exceeds 50 parts, the unit water content increases too much, and even if the pozzolanic activity is added, the strength decreases significantly. Even if the amount of the water reducing agent is increased, the water reducing rate does not increase, which is not preferable. The content of incineration ash is preferably at most 40 parts. In addition, the compounding ratio, the part showing the addition amount, and the% used in the present invention are mass units unless otherwise specified.

[0007] The incineration ash is a brown powder, which is apparently light and dusty with a low bulk density, but the air permeation type brane specific surface area measuring device used in the cement industry has a high air permeation rate. The result is that the powder is too coarse to measure. When this incineration ash is mixed with cement to make concrete, the unit water amount increases,
Not only the long-term strength is lowered, but also the development of the initial strength is hindered because the phosphate is contained in a large amount. It was found that the incineration ash has a characteristic different from the conventional wisdom that the unit water content decreases with increasing the fineness, but on the other hand, the phosphate easily dissolves and the setting retarding effect is strong. It becomes an antinomy property of becoming.
However, by using quicklime and / or slaked lime of the present invention as a setting hardening accelerator, as a result, it is preferable that the incineration ash having a higher fineness has a higher rate of producing an insoluble calcium phosphate salt. Therefore, the incinerated ash of the present invention is preferably pulverized to have a fineness of 5,000 cm ² / g or more by the Blaine specific surface area method (measured according to JIS R5201), and 6000.
cm ² / g or more is more preferable, and 8000 to 15000
cm ² / g is more preferable. If it is less than 5000 cm ² / g, the effect of suppressing an increase in the unit water amount of the incinerated ash is small, which is not preferable. Further, even if it exceeds 15,000 cm ² / g, the effect of suppressing an increase in the unit water amount of the incinerated ash and the pozzolanic activity effect reach saturation and the increase in strength is not exhibited, and further crushing is uneconomical, which is not preferable.

The quicklime-containing substance of the present invention is not particularly limited, but examples thereof include soft-baked quicklime and calcined dolomite which are calcined at 1300 ° C. or lower. Thirteen
Although a commercial cement expansive material containing free lime hardened at a sintering region temperature of more than 00 ° C. cannot be used as it is, it can be used by digesting it or finely pulverizing it so as not to expand excessively. Of these, soft-baked quicklime is most preferred, and then calcined dolomite is preferred. Further, the slaked lime-containing substance of the present invention is not particularly limited, but it is obtained, for example, by digesting a substance containing free lime as a main component. Although it has a weaker effect of promoting setting and hardening than free lime, it has an effect of reducing a decrease in long-term strength. The free lime (hereinafter, referred to as f-CaO) equivalent amount of the substance containing quick lime and / or slaked lime in the present invention means the amount of f-CaO and Ca (OH) ₂ in the substance containing quick lime and / or slaked lime to f-. It is the sum of the values converted into the amount of CaO.

In the present invention, the fineness of soft-calcined quicklime, slaked lime and calcined dolomite is not particularly limited as long as it is equal to or higher than that of cement. However, the higher the fineness of powder, the more the tendency to promote the development of initial strength. is there. Especially f-C
When an expansive material containing aO is used, a commercially available material is preferably finely pulverized to have a fineness of 5000 cm ² / g or more in order to suppress expansion, and more preferably 6000 cm ² .
² / g or more.

In the present invention, 10 to 50 parts of incinerated ash of sewer sludge is mixed with 100 parts of cement, and quick lime and / or slaked lime is added to 1 to 15 parts in terms of f-CaO. Compound. If the amount of quicklime and / or slaked lime in terms of f-CaO is less than 1 part, the effect of accelerating the setting and hardening is poor, and if it exceeds 15 parts, the initial and long-term strength decreases, which is not preferable. It is preferably 2 to 12 parts, and more preferably 3 to 10 parts.

In the present invention, the state of the incineration ash or the curing accelerator and the method of adding the same are not particularly limited,
(1) A method of adding a mixture of incinerated ash and a main curing accelerator separately crushed and mixed when concrete is mixed,
(2) A method in which both are mixed and pulverized and added when kneading concrete, and (3) preliminarily prepared and burned so that a specified amount of f-CaO remains in the incinerated ash,
Any method such as adding a crushed product when kneading concrete is acceptable, but (4) crushing the incineration ash and the hardening accelerator separately and mixing both concrete components without mixing them It is more preferable to add an arbitrary amount in combination, because the strength developing property can be adjusted.

In the present invention, a special method is not required for adding and mixing to concrete, using a normal mixer, and adding it to other mixers in powder state together with other concrete materials, and mixing with the normal mixing. It is kneaded in time and used for construction of civil engineering structures and production of secondary concrete products.

In the present invention, the type of cement used is not particularly limited, and various portland cements, mixed cements, rapid hardening cements by the production of ettringite, and the like.

In the present invention, general water reducing agents such as lignin sulfonate type, polyol type, oxycarboxylate type, high performance water reducing agent and high performance AE water reducing agent are also used, but particularly preferable are: It is a high-performance water reducing agent such as polyalkylallyl sulfonate type and melamine resin sulfonate type, which has a large water reduction rate, and a high performance AE water reducing agent of polycarboxylic acid type.

In the present invention, in order to prevent a decrease in concrete strength or to increase the strength, a high-strength admixture containing gypsum as a main component, silica fume, metakaolin and fly ash classified to 20 μm or less are used. A high-strength admixture containing activated silica as a main component can be used together, and a commercially available expansive material can also be used together in order to reduce cracks and to produce a chemical prestressed concrete.

[0016]

EXAMPLES The present invention will now be described in detail with reference to examples, but the invention is not limited thereto.

Example 1 800 g of ordinary Portland cement, 1200 g of river sand produced in Himekawa, Niigata, 210 g of water, 10 g of high-performance water reducing agent (polyalkylallyl sulfonate type), JIS R 5201
According to the mortar with a flow value of 180 to 190 mm, with respect to 100 parts of cement, the types of incineration ash and hardening accelerator and f
The amount of -CaO conversion was changed as shown in Tables 1 and 2 (excluding impurities other than f-CaO in the curing accelerator and replaced with sand), and external addition was added and mixed. The amount that the flow decreases due to the composition of the incineration ash is adjusted by adding water to the flow value so that the flow value falls within 180 to 190 mm, and mixed 4 ×
It was molded into a 4 × 16 cm triple mold and the strength was measured for standard ageing for 1 day (1 piece) and 28 days (2 pieces). Table 1 shows the fluctuations in the amount of water and the strength measurement results after standard curing. The method of mixing mortar, measuring the flow value, molding the sample, and measuring the compressive strength were based on the physical test method for cement according to JIS R5201. The amount of f-CaO is
F with methyl acetoacetate and isobutanol alcohol solution
-CaO was dissolved and extracted and analyzed by a modified Franke method in which it was titrated with a 60% perchloric acid-isobutanol alcohol solution. In addition, Ca (OH) ₂ was also analyzed by the same analysis method as f-
It was converted to the amount of CaO. When f-CaO and Ca (OH) ₂ coexist, the total f-CaO amount is measured by the modified Franke method, and further, by an analyzer called TG-DTA capable of thermogravimetric analysis and differential thermal analysis at the same time, Ca (OH)
_The amount of f-CaO and the amount of Ca (OH) ₂ were calculated from the confirmation of the dehydration peak of _{2 and} the content thereof from the dehydration amount (weight reduction amount), and together with the analysis result by the modified Franke method.

"Materials used" (1) Incinerated ash: Phosphorus pentoxide 8.5 from Shin-Kagashi Incinerator, Sewerage Bureau, Tokyo
%, F-CaO equivalent 0%, specific gravity 2.60 A-1: Specific surface area cannot be measured (unground product) A-2: Specific surface area 5000 cm ² / g (ground product) A-3: Specific surface area 6020 cm ² / g (crushed product) A-4: specific surface area 8080 cm ² / g (crushed product) A-5: specific surface area 10000 cm ² / g (crushed product) A-6: specific surface area 15040 cm ² / g (crushed product) (2) Limes: quick lime (gas burned soft burned quick lime), f-CaO equivalent 9
8.0%, manufactured by Denki Kagaku Kogyo Co., Ltd. a-1: Specific surface area 5010 cm ² / g (ground product) a-2: Specific surface area 6090 cm ² / g (ground product) a-3: Specific surface area 9030 cm ² / g (Pulverized product) Slaked lime (digested quicklime of a), f-CaO equivalent amount 74.2% b-1: Specific surface area 10100 cm ² / g (pulverized product) Expansion material (finely pulverized product of commercially available expansion material, Denka Chemical Industry Co., Ltd. product name Denka CSA # 20), f-CaO amount 20.0% c-1: specific surface area 6100 cm ² / g (crushed product) c-2: specific surface area 9300 cm ² / g (crushed product) ) Firing dolomite (firing at 850 ° C), f-CaO equivalent 2
9.5%, fired in an electric furnace in the laboratory d-1: specific surface area 8020 cm ² / g (ground product)

[0019]

[Table 1]

[0020]

[Table 2]

As shown in Table 1, regardless of whether or not the curing accelerator of the present invention is used in combination, when the incineration ash is crushed to increase the fineness, the amount of water decreases. In particular, it becomes remarkable when the fineness is 5000 cm ² / g or more with respect to uncrushed incinerated ash,
Further, it can be seen that the water amount decreases gradually as the fineness increases, but it reaches the ceiling when it is 10000 cm ² / g or more. At this time, in the expression properties of 1-day strength, in the comparative example in which the accelerator is not used in combination, the initial strength expression property is inhibited as the fineness of powder becomes larger, and the strength value is several N / mm ² or less. On the other hand, the examples of the present invention show a high strength of a dozen N / mm ² . The 28-day strength also gradually increases as the fineness increases as the unit water amount decreases, but the pozzolanic effect is not sufficiently exerted in the comparative example, and in the example of the present invention, the strength of the comparative example is higher than that in the comparative example. Shows a high value of around 10 N / mm ² and f
-CaO suggests that the pozzolanic reaction is activated (Comparative examples of Experiment Nos. 1-2 to 1-5, No. 1-8 and No. 1-12 and N
o.2-1, 2-4, 2-7, 2-11 comparing the examples of the present invention). Fineness of ash from the standpoint of strength is preferably at least 5000 cm ² / g, more preferably 6000 cm ² / g, 80
Most preferred is 00 cm ² / g or more, but 15000 cm ²
It is easily inferred that it will reach the ceiling even if it exceeds / g.
(Examples of the present invention in Experiment Nos. 2-1, 2-4, 2-7, and 2-11).

Although the amount of incinerated ash is increased, the amount of water increases in sequence, regardless of whether or not a curing accelerator is used in combination.
Especially, it is remarkable at 40 parts or more. Along with this, the daily strength of the comparative example gradually decreases, and the value is also several N / mm ² or less.
In the examples of the present invention, a high strength of ten and several N / mm ² is exhibited, but when the incinerated ash is 40 parts or more, it tends to be rapidly decreased.
Although the 28-day strength also gradually decreases, in contrast to the comparative example having a low pozzolanic activity, the examples of the present invention show a strength higher by 10 N / mm ² or more at any addition amount. Furthermore, when the content of incinerated ash is 40 parts or more, the increase in the unit water amount exceeds the pozzolanic effect, and the strength tends to decrease sharply, and the incinerated ash is 10 to 50 parts, preferably at most 40 parts. It is understood that (Comparative examples of Experiment Nos. 1-6 to 1-11 and No. 2-5 to No. 2-
Comparison of 10 inventive examples).

When the amount of the curing accelerator added is increased, the 1-day and 28-day strengths gradually increase, but when the f-CaO conversion amount exceeds 15 parts, it tends to decrease. Therefore, it is understood that the curing accelerator is 1 to 15 parts, preferably 2 to 12 parts, and more preferably 3 to 10 parts in terms of f-CaO (Comparative Examples of Experiment No. 1-8 and No. 2). -Comparison of examples of the present invention from -12 to 2-18). When the hardening accelerator is slaked lime, the 1-day strength does not become so high, but the 28-day strength exhibits a slightly lower absolute value of the strength than the case of quick lime, but shows the same tendency of strength development (Experiment No. 2- 21 to 2-26). When the hardening accelerator is calcined dolomite, the 1-day strength and the 28-day strength are almost the same as those of quicklime, but the 28-day-old strength tends to be slightly lower (Experiment No. 2-29 to 2- 32). Further, the hardening accelerator tends to increase in strength for 1 and 28 days when the fineness is increased (Experiment No. 2-7, 2-19, 2-20, 2-27, 2-28).

Example 2 Nos. 2-5 to 2-1 for the experiments No. 1-1 and No. 1-8 of Example 1.
Table 3 shows the results of the same test as in Example 1 in which the water reducing agent used in Example 1 was added to the mortar Nos. 2-12 to 2-18 to increase the amount of water reducing agent.

[0025]

[Table 3]

As shown in Table 3, the daily strength tends to decrease as the amount of the water-reducing agent increases, and in particular, it becomes remarkable when the amount of the water-reducing agent is 40 g (5% of cement) or more. Also, as the amount of water reducing agent increases, the amount of water decreases, so the 28-day strength increases, but when the amount of incinerated ash exceeds 40 parts, the amount of water does not easily decrease even if the amount of water reducing agent is increased, and the strength decreases. Also grows. Also in this case, it is understood that the most preferable amount of incineration ash is 40 parts. Even when the amount of the curing accelerator added was increased, the same tendency as in Example 1 was exhibited (Experiments No. 3-9 and No. 3-15).

Example 3 The air content of the mortars of Experiment Nos. 2-1 to 2-8 of Example 2 was 2%.
And (volume), coarse aggregate so that the 1 m ³ (maximum dimension 2
Table 4 shows the results obtained by mixing concrete mixed with 5 mm of gravel) to prepare a test piece, and measuring the strength of the material for 1 day and 28 days in standard curing. The slump is 8 cm
It was within a range of ± 2 cm, and the method for producing the test piece and the method for measuring the strength were in accordance with JIS A 1132 and JIS A 1108.

[0028]

[Table 4]

From Table 4, it can be seen that even when the concrete is used, the same strength development properties as the mortar of Example 2 are exhibited.

Example 4 The concrete of Example 3 was molded into a horizontal capless mold and precured at 20 ° C. for 8 hours, and then at 85 ° C. for 3 hours.
Table 5 shows the results of measuring the demolding strength on the next day and the standard-aged 28-day-old strength on the next day.

[0031]

[Table 5]

From Table 5, Example 3 is also shown when steam curing is performed.
It can be seen that the same tendency as the 28-day-old strength of the standard cured concrete of No. 1 shows the same tendency.

[0033]

EFFECTS OF THE INVENTION By using the hardening accelerator for cement to which the incinerated ash of the present invention is added, the set retardation property and the decrease in long-term strength of the conventional incinerated ash are improved. Most of the conventional incineration ash is treated as industrial waste, but when this curing accelerator is used together, it can be utilized as a cement admixture and can be recycled as resources, which is also useful for green procurement. Since it is fired at a low temperature, the construction cost and maintenance cost of the incinerator are low and it is economical. And other effects.

Claims (2)

[Claims] 1. A hardening accelerator for cement containing incineration ash of sewer sludge containing quicklime and / or slaked lime as a main component. 2. 10 to 50 parts of incinerated ash of sewer sludge and 100 parts of cement, and a substance containing quick lime and / or slaked lime in terms of free lime (f-CaO) (f-CaO amount and Ca ( 1 to 15 parts by weight of OH) ₂ converted to the amount of f-CaO).