JP7287672B2 - METHOD FOR MANUFACTURING SETTING-RETARDING ACTIVE FILLER FOR GEOPOLYMER AND METHOD FOR MANUFACTURING GEOPOLYMER SOLID BODY - Google Patents

Description

TECHNICAL FIELD The present invention relates to technology for slowing the setting of geopolymers using granulated blast furnace slag.

The geopolymer solidifies by stimulating the active filler (aluminosilicate source) with an alkaline solution (alkali source), which promotes the polycondensation reaction of the silicate complex and solidifies without using conventional cement clinker. It is an inorganic material that can produce
The active filler that constitutes the geopolymer is a source of cations necessary for solidification of the geopolymer, so it is desirable that it contains a large amount of Si and Al as constituent elements. If it is a natural product, metakaolin or the like is used. . Industrial by-products and wastes such as fly ash, granulated blast furnace slag, molten slag of municipal waste incineration ash, and molten slag of sewage sludge can also be used as active fillers. For this reason, geopolymers are positioned as an important technology from the viewpoint of effective utilization of waste.

By the way, metakaolin and granulated blast furnace slag are used as active fillers alone or in combination with other types of active fillers, in order to make geopolymers have excellent strength development and practical strength in a normal temperature environment. used in combination. Since Japan has almost no kaolin resources, granulated blast furnace slag is generally used alone or in combination. However, geopolymers using granulated blast furnace slag have a short setting time. Granulated blast furnace slag alone takes about 20 minutes at room temperature (20° C.), and even when mixed with a large amount of fly ash, it takes about 40 minutes. However, when the concrete is transported by a tank truck called an agitator vehicle, the time from mixing the concrete to the completion of pouring varies depending on the transportation distance, and in many cases it takes 60 to 120 minutes. Incidentally, the Japan Society of Civil Engineers and the Architectural Institute of Japan stipulate that the time from mixing concrete to finishing casting is within 2 hours when the outside temperature is 25°C or less, and within 1.5 hours when it exceeds 25°C. .

In the past, attempts have been made to use various sodium salts to retard the setting of geopolymers.
For example, in Non-Patent Document 1, when using blast furnace cement B type and No. 3 water glass, the setting time was 1 to 3 minutes, but by adding 1 to 2% sodium dihydrogen phosphate , can be delayed up to about 10 minutes. The solidified material using blast furnace cement type B and No. 3 water glass is not a geopolymer, but a polycondensation reaction that contributes to the solidification of the geopolymer may occur.
In addition, in Patent Document 1, 3% sodium salts of citric acid, tartaric acid, and gluconic acid are added as geopolymer additives to an active filler containing granulated blast furnace slag powder, and the pot life is around 60 minutes. is disclosed.

However, the techniques using various sodium salts as in Non-Patent Document 1 and Patent Document 1 do not provide the necessary setting retardation effect.

JP 2016-79046 A

Katsuji Akita, Takeshi Iwasaki, Naoki Nishimura, "Study on control of solidification time of cement water glass injection material", Journal of Japan Society of Civil Engineers, Special Issue F1 (Tunnel Engineering), vol.66, No.1, pp.69-78 , October 2010

The problem to be solved by the present invention is to provide a new setting delay technology for effectively utilizing granulated blast furnace slag as a raw material for geopolymer.

The present inventors conducted various tests to effectively utilize granulated blast furnace slag as a raw material for geopolymer, and found that heat treatment of granulated blast furnace slag has the effect of delaying the coagulation of geopolymer. I found out.

That is, according to the present invention, the following method for producing a setting-retarding active filler for a geopolymer and a method for producing a solidified geopolymer are provided.
1.
In the method for producing the active filler used for producing the solidified geopolymer,
A method for producing a setting-retarding active filler for a geopolymer, comprising heat-treating granulated blast furnace slag at 200 to 1000° C. to obtain the effect of delaying the setting of the geopolymer.
2.
2. The retardation of setting of the geopolymer according to claim 1, wherein the heating temperature of the granulated blast furnace slag is 200° C. or higher and not higher than a temperature at which a halo is detected in X-ray diffraction analysis using CuKα rays as a radiation source. A method for producing a mold active filler.
3.
2. The method for producing a setting-retarding active filler for geopolymer according to claim 1, wherein the heating temperature of the granulated blast furnace slag is 200[deg.]C or higher and lower than 800[deg.]C.
4.
In the method for producing a geopolymer solidified body,
A geopolymer characterized by using a setting-retarding type active filler for a geopolymer obtained by the production method according to any one of claims 1 to 3 as an active filler to delay the setting of the geopolymer. A method for producing a solidified body.

According to the present invention, it is possible to retard the coagulation of a geopolymer made from granulated blast furnace slag. As a result, granulated blast furnace slag can be effectively used as a raw material for geopolymer.

X-ray diffraction measurement results of granulated blast furnace slag heat-treated at a temperature of 800°C or less. X-ray diffraction measurement results of granulated blast furnace slag heat-treated at 800°C to 1000°C. Thermogravimetric differential thermal analysis (TG-DTA) curve of granulated blast furnace slag. Comparison of strength test results of geopolymer mortar (solidified geopolymer) using heat-treated granulated blast furnace slag and geopolymer mortar using unheated granulated blast furnace slag. Relationship between pot life of geopolymer paste based on granulated blast furnace slag heated to 800° C. and substitution rate of granulated blast furnace slag not heated or heat-treated at other temperatures. Bending strength when granulated blast furnace slag heated to 800° C. is mixed with unheated granulated blast furnace slag or heat-treated at other temperatures to give geopolymer mortar a pot life of 120 minutes.

The setting delay technology of the present invention is based on a physical method of heat-treating granulated blast furnace slag, and is a new setting delay technology that is completely different from conventional chemical methods of adding various sodium salts.

In order to confirm the effect of the retardation technology of the present invention, granulated blast furnace slag (hereinafter referred to as "GGBS") was heat-treated, and the properties of the heat-treated GGBS were evaluated. In addition, a geopolymer (hereinafter referred to as "GP") was produced using the heat-treated GGBS, and the pot life of the GP was evaluated, and the strength of the solidified GP obtained was evaluated.

The three GGBS samples used in the experiment were JISA6206 blast furnace slag ground powder 4000 grade standard products, and their chemical analysis values and related physical constants by X-ray fluorescence spectroscopy (XRF) are shown in Table 1. The main component of GGBS is SiO ₂ —CaO—Al ₂ O ₃ , but MgO is also quite large and cannot be ignored. In XRF, whole rock analysis including trace elements was performed by the FP method using powder press samples.

70 to 80 g of GGBS was placed in an alumina crucible having a volume of about 120 cm ³ , heated at a predetermined temperature for 24 hours using a muffle type electric furnace, then taken out of the furnace and air-cooled. Heating was carried out from 100° C. to 1000° C. at intervals of 100° C., but there are cases where the heating is performed at intervals of 50° C. supplementarily. The rate of temperature increase from room temperature to each heating temperature is approximately 20° C./min.
The raw GGBS before heating and the GGBS after heat treatment were subjected to phase identification by X-ray diffraction analysis (XRD) and morphological observation by a polarizing microscope. In addition, thermal analysis of raw GGBS before heating was performed by TG-DTA.
For XRD, CuKα radiation was used as the source and a monochromator or nickel filter was used.
For polarizing microscopy, powder samples were immersed in olive oil (n=1.47) under crossed or parallel Nicols and photographed.
In TG-DTA, the temperature was raised from room temperature to 1000° C. at a rate of 10° C./min and measured in an air atmosphere.

FIG. 1 shows the results of GGBS-A heated at temperatures below 800° C. analyzed by an XRD device (40 kV-120 mA) called Rigaku Rint. Also, FIG. 2 shows the results of GGBS-A heated at 800 to 1000° C. analyzed by an XRD device (45 kV-200 mA) called Rigaku SmartLab. In FIGS. 1 and 2, the marvinite peak is indicated by M, but the galenite peak is unmarked.

As shown in FIG. 1, in raw GGBS-A (RAW) before heating, a halo (also called a hump) due to the glass phase is detected, and a small peak overlapping it is observed. The position coincides with the main peaks of galenite (2CaO.Al ₂ O _{3.SiO 2} ) and marvinite (3CaO.MgO.2SiO ₂ ). . No particular phase change due to heating is observed up to 750°C, and sudden crystallization occurs when heated to 800°C. The product crystalline compound is galenite and a small amount of marvinite, and the halo due to the glassy phase is no longer detectable. Incidentally, the chemical formulas in parentheses are for pure phases, which are usually solid solutions containing some impurity elements.
Although the X-ray reflection intensity (vertical axis value) measured by the above XRD apparatus was different, the shape of the XRD chart of GGBS heated at 800° C. in FIG. 2 is the same as that at 800° C. in FIG. It can be seen from FIG. 2 that the crystals are crystallized at heat treatment temperatures of 900° C. and 1000° C. in the same manner as at 800° C. The crystal compounds were the same, ie, galenite and a small amount of marvinite, but there was a tendency that the higher the heating temperature, the higher the X-ray reflection intensity. That is, the crystallinity improves as the heating temperature increases.

Table 2 shows the measurement results of pot life.
At present, the method for measuring the pot life has not yet been established, and it varies depending on the researcher. This time, the mini-spatula method was used. This is a method of piercing the GP paste with a flat plate of a small spatula like an earpick, which is often used for weighing in laboratories. That is, it corresponds to the maximum time that can be kneaded in the method of starting from the time when the GP paste is finished loading into the test container and setting the time until no liquid exudation is observed in the indentation as the workable time. The pot life obtained is the time close to the end of the setting test performed with a Vicat needle.
The GP paste for measuring this pot life uses raw GGBS (RAW) before heating and GGBS heat-treated as described above, and each GGBS and an alkaline solution are mixed at a predetermined liquid filler ratio (liquid / filler mass It was obtained by kneading with a ratio).
The preparation of the alkaline solution is as follows.
Commercially available sodium-based JIS No. 1 water glass (SiO ₂ /Na ₂ O molar ratio: 2.1, specific gravity: 1.54) was diluted twice with deionized water. On the other hand, pure chemical caustic soda pellets were dissolved in deionized water to obtain a 10 mol/L aqueous solution (specific gravity: 1.32). Finally, the two were mixed at a volume ratio of 3:1 and left overnight to be used as an alkaline solution.
The specifications of the alkaline solution thus prepared are as follows.
_SiO2 : 13.5% by mass, _Na2O : 12.8% by mass, _H2O : 73.7% by mass
Concentration: 26.3%, _SiO2 / _Na2O molar ratio: 1.1

As shown in Table 2, the pot life of the GP paste using raw GGBS (RAW) before heating is as short as 14 to 48 minutes, although it varies from lot to lot. According to the results of investigation with GGBS-A, the pot life tends to be extended by heating, reaching a maximum at 400°C. After that, it tends to decrease and reaches a minimum at 600°C. When it is further heated, it tends to extend again, and when it reaches 800°C, its activity decreases due to crystallization, resulting in a very long pot life of 340 minutes. Furthermore, when heated at a high temperature of 900° C. or higher, sintering proceeds and a hard core is produced. The powder that has been lightly pulverized to the extent that there is no core has a low density (apparent density), and it seems that there are many voids, probably due to foaming. On the other hand, the specific surface area decreases, probably because sintering proceeds. However, although the reason is not clear, the pot life is significantly extended at 800°C or higher.
The liquid filler ratio of other than the GP paste using GGBS-A heated at 1000 ° C. is 0.40, but the liquid filler ratio of the GP paste using GGBS-A heated at 1000 ° C. is 0.45. bottom. This is because GGBS-A heated at 1000° C. absorbs a large amount of alkaline solution and does not have fluidity at a liquid filler ratio of 0.40.

Since GGBS-B and GGBS-C showed similar trends, detailed data were not collected. However, the following three points should be noted here. The first is heating to 400° C., and while not the same value for each, the pot life is roughly 2-4 times longer than the unheated (RAW) case. The second is heating at 700° C., and the pot life becomes almost constant at approximately 60 to 70 minutes. The third is heating at 800° C., and like the case of 700° C., the pot life becomes almost constant and shows approximately 340 minutes.
From the above, it is considered that the range of application is wide because heating at 700° C. in particular shows a certain pot life while maintaining high activity. Of course, according to the results of investigation with GGBS-A, heating at 200 ° C or higher has the effect of extending the pot life, that is, the effect of delaying the setting of GP, so the heat treatment to obtain the effect of delaying the setting of GP The temperature of 200 to 1000°C is sufficient, preferably 400 to 1000°C, more preferably 400 to 800°C.

Observation under a polarizing microscope revealed that when the glass transition point was exceeded, the glass phase began to fuse and the particles were enlarged. At the same time, spherical particles with a maximum diameter of about 10 μm appear, which are particularly noticeable when heated to 800° C. (photograph not shown). As shown in FIG. 1, the XRD chart of the material heated to 800° C. records the appearance of a clear crystal phase, but GGBS is considerably opaque under a polarizing microscope and individual crystals cannot be seen. As a result of examining the crystallite size by introducing the Schiller formula into the XRD peaks of the 800-heated product, the average value of the 19 peaks is 26.4 nm, which is far smaller than the limit of 1000 nm that can be recognized with an optical microscope. Met.
On the other hand, in the 900° C. and 1000° C. heated products, the glass portion that constitutes most of the GGBS is crystallized. Unrecognizable. In short, nanocrystals with a crystallite size of less than 1000 nm, and the XRD results are mostly galenite, similar to the 800° C. heated material. The crystallite diameters of the galenite heated at 900° C. and 1000° C. were 103.5 nm and 86.8 nm, respectively.

Thus, when heated at 800° C. or higher, crystallization occurs and the pot life is greatly extended. No halo is detected in X-ray diffraction measurement using CuKα rays as a radiation source, but a peak of galenite is detected.
Here, the crystallite size of the gehlenite in the slow-setting active filler for geopolymer, which is one embodiment of the present invention, is less than 1000 nm, which is clearly different from the crystallite size (about 10 μm) of the gehlenite in the slow-cooled blast furnace slag. is. Based on the above experimental results, the crystallite size of the gehlenite of the slow-setting active filler for geopolymers, which is one embodiment of the present invention, is approximately 200 nm or less.

FIG. 3 shows TG-DTA curves of three GGBS raw material samples (GGBS-A, B, C).
With heating, the TG curve shows a gradual weight decrease, and when the temperature exceeds 900°C, the weight tends to increase. On the way, except for GGBS-A, a rapid weight change is observed at 600 to 700°C. The final weight loss is about 3-4%. This weight loss is due to the fact that the glass is produced by the water granulation process, and it is considered that the main cause is the gradual loss of water trapped in the glass phase due to heating. The final weight increase is considered to be mainly due to the oxidation of ferric iron to trivalent iron.
According to the DTA curve, two exothermic peaks and one endothermic peak are observed. The exothermic peak near 500°C corresponds to the glass transition point, and is considered to be closely related to the pot life at 400°C. That is, since the pot life measurement is the result of static heating, and the DTA result is the result of dynamic heating, it is natural that there is a discrepancy between the two. Since the onset of this peak is around 450.degree. The exothermic peak near 900° C. is the crystallization of the glass phase, which looks like a double peak. Judging from the size of the peaks, it is considered that the lower temperature corresponds to the crystallization of marvinite and the higher temperature corresponds to the crystallization of galenite. The endothermic peak around 650°C is considered to be decarboxylation, which is particularly noticeable in GGBS-C. Carbonation of GGBS has already been confirmed by FTIR (measurement results are omitted), and it is certain that this peak corresponds to decarboxylation. The pot life of raw GGBS-C (RAW) before heating shown in Table 2 is much longer than that of normal GGBS, and it was purchased earlier, so it is believed that GGBS was gradually carbonated in the stock.

Next, a strength test of GP mortar (GP solidified body) using heat-treated GGBS was conducted.
In this test, a heat-treated GGBS, an alkaline solution (same as that used for the GP paste for pot life measurement described above), and sand (Toyoura sand) were mixed with a liquid filler ratio of 0.65, sand: GGBS mass ratio = 2: 1, cast in a mold (3 pieces of 20 x 20 x 80 mm, made of gunmetal), cured overnight at 20 ° C - 100% RH, and then removed from the mold. Furthermore, it was cured under the same conditions until it reached a predetermined material age, and its flexural strength was measured. The bending strength was measured by a three-point bending test method, and the average value of three pieces at each age was taken as the average value.

FIG. 4 shows the strength test results of GP mortar (GP solidified body) (hereinafter also simply referred to as “mortar”) using heat-treated GGBS-A. For comparison, a mortar strength test using unheated GGBS (RAW) was also conducted, and the results are also shown in FIG.
Except for the mortar using the crystallized 800°C heating material, the strength of the mortar using the GGBS heating material that has been heat-treated at 400°C or 700°C in advance is compared to the strength of the mortar using untreated raw GGBS (RAW). The results were equal to or better than At the age of 1 day, the development of strength was slightly suppressed due to the setting retardation effect, but as the age progressed, the strength approached that of mortar using raw GGBS (RAW), and at the age of 28 days, the strength of the raw GGBS (RAW) mortar was reduced. The result was that the strength was slightly higher than that of the mortar using GGBS (RAW).
In the case of heating at 700 ° C, the strength tends to decrease slightly at the age of 28 days, but it is considered that this weakness can be improved by mixing fly ash (hereinafter referred to as "FA"). Mixing is actually done for waste utilization. In the case of heating at 800° C., the initial strength is not good, but the bending strength exceeds 5 MPa at the age of 28 days. Although it depends on the type of solidified GP, the compressive strength of the solidified GP is generally 5 to 8 times the bending strength, and is empirically guaranteed to be at least 5 times. If a flexural strength of 5 MPa or more can be secured, the concrete using this geopolymer as a binder has a compressive strength of 20 MPa or more, so it is considered that it can be utilized in actual concrete construction.

Heat treatment of GGBS at 400° C., 700° C. and 800° C. in this way expands the range of application of solidified GPs using GGBS from the viewpoint of not only strength but also retarding effect on setting, and helps to put them into practical use. . For example:

As a first application, it can be applied in the following cases. In the case of large-scale construction, it is often the case that a batcher plant is set up on site to knead the concrete.

As a second application, in the case of transportation and construction of ready-mixed concrete, it is practically required by using a mixture of GGBS heat-treated at 800°C and non-heat-treated GGBS or GGBS heat-treated at a temperature lower than 800°C. It has a high strength and can achieve a pot life of 2 hours.

As shown in Table 3 and FIG. 5, in the case of GGBS heated at 800° C., which has a very long pot life, in order to achieve a pot life of 120 minutes, unheated raw The replacement ratio of GGBS (indicated as “filler replacement amount” on the horizontal axis of FIG. 5)) is 10%, the replacement ratio of GGBS when heated at 400 ° C. is 25%, and the replacement ratio of GGBS when heated at 700 ° C. is 35%. . For GGBS-C, they are 20%, 85% and 40%, respectively. As a result, in the case of heating at 700° C., the substitution ratios of GGBS-B and C are close. The reason for this is that, as shown in Table 2, the pot life when using GGBS heated to 700° C. and 800° C. is almost constant and stable regardless of the type of GGBS used as a raw material.

FIG. 6 shows the above results arranged from the viewpoint of strength. That is, the plot of "○" in FIG. 6 is the replacement ratio at which the pot life becomes 120 minutes when GGBS-B heated at 800 ° C. is used as the base (the horizontal axis in FIG. ), and the plot of "" indicates the bending strength when the pot life is 120 minutes in the case of using GGBS-C heated at 800° C. as the base. In addition, the plot of "□" indicates the average value of GGBS-A, B, and C bending strengths when the replacement rate for the 800°C heated material is 0% and 100%. It should be noted that this "□" plot does not mean that the pot life is 120 minutes.
Table 4 shows the data for each plot in FIG.

The bending strength exceeds 5 MPa at any replacement ratio.

Claims (4)

In the method for producing the active filler used for producing the solidified geopolymer,
A method for producing a setting-retarding active filler for a geopolymer, comprising heat-treating granulated blast furnace slag at 200 to 1000° C. to obtain the effect of delaying the setting of the geopolymer. 2. The retardation of setting of the geopolymer according to claim 1, wherein the heating temperature of the granulated blast furnace slag is 200° C. or higher and not higher than a temperature at which a halo is detected in X-ray diffraction analysis using CuKα rays as a radiation source. A method for producing a mold active filler. 2. The method for producing a setting-retarding active filler for geopolymer according to claim 1, wherein the heating temperature of the granulated blast furnace slag is 200[deg.]C or higher and lower than 800[deg.]C. In the method for producing a geopolymer solidified body,
A geopolymer characterized by using a setting-retarding type active filler for a geopolymer obtained by the production method according to any one of claims 1 to 3 as an active filler to delay the setting of the geopolymer. A method for producing a solidified body.

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