JP7136456B2 - Quantification method of xonotlite formation rate by thermal shrinkage - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for quantifying the xonotlite production rate in calcium silicate hydrate produced by a hydrothermal reaction based on the thermal shrinkage rate.

Both xonotlite and tobermorite are representative calcium silicate hydrates and are widely used as building materials with excellent thermal stability. These xonotlite and tobermorite are produced by adding fibrous substances, if necessary, to a main raw material consisting of a silicic raw material such as silica and quartzite and a calcareous raw material such as CaO, and then adding water to form a slurry. , is generally produced by a method of forming a compact by causing a hydrothermal reaction in an autoclave at high temperature and high pressure.

Among xonotlite and tobermorite produced in this way, xonotlite in particular has little water of crystallization, as can be seen from the composition _{formula 6CaO.6SiO.sub.2.H.sub.2O} . have. In addition, xonotlite is produced by growing primary particles into hollow secondary particles and then hardening them. Because of its shape, it has the characteristics of light weight and high strength. Due to these characteristics, xonotlite compacts have long been used as heat insulating materials for high temperatures, such as fireproof coatings.

By the way, the xonotlite molded body produced by stirring the siliceous raw material and the calcareous raw material in water in the high-temperature and high-pressure autoclave described above originally has a high strength as described above. Depending on the conditions, sufficient strength may not be obtained. Moreover, when heated to a high temperature, the shrinkage rate may become too large. Therefore, Patent Literature 1 proposes a method of producing a xonotlite compact in the same manner as conventional lightweight cellular concrete (ALC) using Portland cement as a calcareous raw material.

That is, in the production method of Patent Document 1, as raw materials, a calcareous raw material powder containing Portland cement and a silicic raw material powder are mixed in a predetermined mixing ratio and prehydrated, and then metallic aluminum powder is added thereto. is added with water to foam and harden, and the resulting semi-hardened body is charged into a high-temperature and high-pressure autoclave and cured in a steam atmosphere. It is possible to produce a xonotlite molded body having a strength of

JP-A-3-141171

However, in the method for producing a xonotlite molded body described in Patent Document 1, the trivalent aluminum ion Al ³⁺ can be a factor that inhibits the formation and crystal growth of xonotlite. It is a requirement that the atomic ratio of Al/(Si+Al) obtained from Al ₂ O ₃ and SiO ₂ present in the mixture be suppressed to 7% or less. Therefore, depending on the manufacturing conditions, the xonotlite compact produced using cement containing about 5% by mass of Al ₂ O ₃ as a chemical component may not have the desired strength.

In addition, in the method for producing xonotlite using cement, since the synthesis conditions for xonotlite are close to those for tobermorite, it is difficult to synthesize a compact consisting of a single phase of xonotlite, resulting in a mixture of both. . Thus, it has been difficult to stably produce a xonotlite molded body having a desired strength by a method similar to the conventional ALC panel production method. In this case, if the generation rate of xonotlite, which is an index of fire resistance performance, can be correctly grasped, the strength of the produced compact can be estimated, so it is possible to stably provide building materials with a certain quality.

Conventionally, the production rate of xonotlite is generally determined by X-ray diffraction (XRD) peak intensity. Alternatively, as another method, a method of calculating the production rate of xonotlite from the mass reduction rate obtained from thermogravimetric analysis (TG) has been proposed. However, when tobermorite is mixed in addition to xonotlite, the coexisting tobermorite crystals are affected by the heat of the coexisting tobermorite crystals, which change to wollastonite and the decarboxylation of calcium carbonate. was difficult to obtain accurately. Therefore, the only way to accurately determine the production rate of xonotlite is by comparing the peak intensity with a standard material by XRD.

The inventors of the present invention conducted intensive studies on a simple method for quantifying the xonotlite formation rate, and found that by varying the curing conditions, xonotlite and tobermorite coexisted in different ratios. As a result of examining their thermal shrinkage characteristics, we obtained the knowledge that the amount of shrinkage differs depending on the curing conditions. Therefore, as a result of separately analyzing the samples by XRD and examining the relationship with the above heat shrinkage characteristics, it was found that a high correlation was observed between the XRD analysis results and the heat shrinkage characteristics. The present invention has been completed.

That is, the method for quantifying the xonotlite production rate according to the present invention is to add metal aluminum powder to a slurry prepared by adding water to a silicic raw material powder and a calcareous raw material powder to foam and harden it, and obtain a semi-hardened A method for quantifying the xonotlite formation rate in calcium silicate hydrate produced by autoclaving a body, in which X-ray diffraction was performed on multiple calcium silicate hydrate samples previously produced under various autoclave curing conditions. The correlation between the peak intensity at a given diffraction angle and the thermal shrinkage rate is obtained by analysis and measurement of the thermal shrinkage rate, and the thermal shrinkage rate of the calcium silicate hydrate to be quantified is measured. The xonotlite production rate is obtained based on the peak intensity at the predetermined diffraction angle obtained by collating the measurement results obtained by the above-mentioned correlation with the above-mentioned correlation.

According to the present invention, the production rate of xonotlite can be easily measured.

1 is a graph showing XRD diffraction patterns of calcium silicate hydrates of Samples 1 to 9 produced in Examples of the present invention. 1 is a graph showing XRD diffraction patterns of calcium silicate hydrates of Samples 10 to 15 produced in Examples of the present invention. 1 is a graph showing thermal shrinkage by TMA of calcium silicate hydrates of Samples 1 to 9 produced in Examples of the present invention. FIG. 10 is a graph showing thermal shrinkage by TMA of calcium silicate hydrates of Samples 10 to 15 produced in Examples of the present invention. FIG. 4 is a graph showing the correlation between the peak intensity of XRD and the thermal shrinkage rate of TMA.

Hereinafter, an embodiment of the method for quantifying the xonotlite production rate of the present invention will be described with reference to the drawings. The substance targeted by the method for quantifying the xonotlite production rate of the embodiment of the present invention is calcium silicate hydrate, which can be produced by the same manufacturing method as the conventional ALC panel. That is, first, a silicic raw material powder and a calcareous raw material powder are prepared as main raw materials, and after mixing them so as to have a predetermined mixing ratio, a predetermined amount of water is added to form a slurry. Silica stone, silica sand, diatomaceous earth, chart, and the like can be used as the siliceous raw material powder. On the other hand, one or more of quicklime, slaked lime, and cement such as Portland cement can be used for the calcareous raw material powder. The above raw materials may further include gypsum and fibrous material.

After metal aluminum powder is further added to the slurry prepared above, the slurry is poured into a mold and foamed and cured to obtain a semi-cured body. The resulting semi-cured product is dried if necessary, cut into panels with piano wire or the like, and preferably autoclaved in a steam atmosphere at 190 to 260°C. This gives a calcium silicate hydrate containing xonotlite.

The calcium silicate hydrate produced by the above production method is sampled and the thermal shrinkage rate is measured by a thermomechanical analyzer TMA. The peak intensity at the predetermined diffraction angle can be determined by comparing the measurement result with the previously obtained correlation between the peak intensity at the predetermined diffraction angle of X-ray diffraction and the thermal shrinkage rate. Since the relationship between the x-ray diffraction peak intensity at the given diffraction angle and the xonotlite production rate is already known, the xonotlite production rate can be obtained from the peak intensity obtained above. That is, by measuring the thermal shrinkage of the calcium silicate hydrate, the xonotlite formation rate of the calcium silicate hydrate can be quantified.

In addition, it is preferable to adopt 2θ=12.6° indicating the xonotlite (001) plane as the predetermined diffraction angle. As the thermal shrinkage measured by the thermomechanical analyzer, it is preferable to adopt the thermal shrinkage within the range of 700 to 900° C., which is the temperature range in which xonotlite changes to β-wollastonite.

(1) Preparation of raw materials and production of calcium silicate hydrate First, silica stone, cement, quicklime, and slaked lime are prepared as raw materials, and the ratio of quicklime/slaked lime is 1/3 by mass, and the molar ratio of CaO/(CaO+SiO ₂ ) is 0.5, Al ₂ O ₃ /(Al ₂ O ₃ +SiO ₂ ) was measured so that the molar ratio was 0.04. Furthermore, aluminum powder in a mass ratio of 0.0007 and water in a mass ratio of 0.67 were separately prepared with respect to the total powder weighed as described above. The above-mentioned silica stone used was Chichibu Mining's Blaine value of 3800 cm ² /g, the cement used was high-early-strength Portland cement manufactured by Sumitomo Osaka Cement, and the quicklime used was manufactured by Ueda Lime Manufacturing. JIS standard products manufactured by Wako Pure Chemical Industries, Ltd. were used as slaked lime, and those manufactured by Yamato Metal Powder Industry were used as aluminum powder.

Next, in a 100 ml plastic cup, the entire amount of the cement and silica stone prepared above is added, half of the prepared amount of water is added, and the mixture is stirred for 10 minutes with a spatula. and slaked lime were added, and the remaining half of water was added and stirred for 2 minutes with a spatula. Finally, the entire amount of the aluminum powder prepared above was added and stirred for 1 minute with a spatula.

After stirring for 1 minute, the plastic cup was immediately wrapped with plastic wrap and cured at 60° C. for 20 hours using a dryer. After curing, the sample was divided into 15 samples 1 to 15, and autoclave curing was performed under conditions of different heating rates, holding temperatures, and holding times, respectively, as shown in Table 1 below. After the autoclave curing, it was quickly cooled with water so as not to be affected by the temperature after the autoclave curing.

(2) X-ray diffraction After drying each sample taken out of the autoclave at an atmospheric temperature of 70 ° C. for 5 hours, a part was cut out and pulverized to 150 μm or less using a mortar, and analyzed by X-ray powder diffraction method XRD. gone. Rigaku's Mini Flex II (CuK _α ray) was used as the XRD apparatus, and the measurement conditions were 30 kV, 15 a, and 20° C./min. Among the obtained diffraction patterns, the peak intensity at the diffraction angle (2θ=12.6°) representing the xonotlite (001) plane was used as an index.

FIGS. 1(a) to (i) and FIGS. 2(a) to (f) show the diffraction patterns of samples 1 to 15 measured by the above XRD. As can be seen by comparing the diffraction patterns of Samples 1 to 15, the peak intensity of the xonotlite (001) plane (2θ = 12.6°) and the peak intensity of the tobermorite (002) plane differed depending on the curing conditions. There is a difference in (2θ=7.8°). Specifically, it can be seen that the higher the holding temperature and the longer the holding time, the higher the peak intensity of xonotlite. Conversely, the lower the holding temperature and the shorter the holding time, the lower the peak intensity of xonotlite, and the peak of tobermorite was also observed. Therefore, it is considered that tobermorite and xonotlite coexist because tobermorite cannot be sufficiently converted to xonotlite when autoclave curing is not performed at a sufficient temperature and time. At a holding temperature of 210° C. and a holding time of 6 hours, no xonotlite peak was observed, and only a tobermorite peak was observed.

(3) Thermal shrinkage property A test piece having a size of 8 mm x 8 mm x 15 mm was cut out from the remaining sample after a portion was cut out as a sample for XRD analysis, and the thermal shrinkage property was measured. A thermomechanical analyzer TMA-60 manufactured by Shimadzu Corporation was used to measure the thermal shrinkage characteristics, and measurements were made at 5°C/min in an air atmosphere from room temperature to 1000°C. The thermal contraction rate at 700° C. before changing from xonotlite to β-wollastonite and at 900° C. after changing was used as an index.

3(a)-(c) and 4(a)-(b) show the relationship between the heating temperature and the thermal shrinkage of samples 1-15 measured by the above TMA. As can be seen by comparing the curve patterns of these samples 1 to 15, the different curing conditions cause differences in the thermal shrinkage patterns. In particular, sharp shrinkage was observed at around 700 to 900°C where xonotlite changed to β-wollastonite, while mild shrinkage was observed at room temperature to 700°C. The mild shrinkage of the latter is considered to be due to the dehydration of adsorbed water and water of crystallization due to the presence of CSH or tobermorite. CSH is a general term for calcium silicate hydrates, which are compositions in which calcium oxide, silicon dioxide, and water are combined in various mixing ratios.

In addition, it can be seen that the amount of shrinkage at 700°C is greater at a holding temperature of 210°C than at a holding temperature of 230°C. Furthermore, the shorter the holding time, the larger the shrinkage amount, and there is a remarkable difference in the shrinkage amount at the holding temperature of 210°C. Since the amount of shrinkage is large under autoclave curing conditions of low temperature and short time, it is considered that a large amount of CSH or tobermorite is present in the compacts produced under these conditions. On the other hand, except for the shrinkage up to 700°C, the shrinkage rate at 900°C increased as the holding time became shorter, and the shrinkage rate became more pronounced at the holding temperature of 210°C. In other words, if the holding temperature is 210° C. and the holding time is 18 hours, the shrinkage amount from 700° C. to 900° C. is close to the holding temperature of 230° C. and the holding time of 12 hours.

At both 210° C. and 230° C., the amount of shrinkage is significantly increased under the conditions of 5 hours of temperature rise and 6 hours of holding. The reason for this is considered to be the difference in the amount and rate of formation of xonotlite due to the difference in the pathway of precursors (from tobermorite to xonotlite and from CSH to xonotlite).

(4) Correlation between X-ray diffraction peak intensity and thermal shrinkage ratio Table 2 below shows the xonotlite (001) plane peak intensity (2θ = 12.6°) measured in the above “(2) X-ray diffraction”, and The heat shrinkage rate at 700°C and the heat shrinkage rate at 900°C measured in "(3) Heat shrinkage properties" are shown. All were measured with n=2, and their average values were calculated.

Among the results shown in Table 2 above, except for the data considered to indicate that xonotlite crystals were not generated because no peak intensity was observed near 12.6°, the other data were measured as shown in FIG. It was plotted on a graph with peak strength on the axis and heat shrinkage on the vertical axis. As a result, it was confirmed that the thermal shrinkage rate at 900° C. and the peak strength had a high correlation. It was also confirmed that the thermal shrinkage rate at 700° C. before changing from xonotlite to β-wollastonite has a high correlation with the peak strength. From the graph of FIG. 5, it can be considered that the xonotlite formation rate is highest under the condition that the shrinkage rate from room temperature to 700° C. is 0% and the shrinkage rate from room temperature to 900° C. is about 1%.

Claims (4)

Calcium silicate hydrate produced by adding metal aluminum powder to a slurry prepared by adding water to silicic raw material powder and calcareous raw material powder, foaming and hardening, and autoclave curing the obtained semi-hardened body. A method for quantifying the rate of xonotlite formation in
Multiple calcium silicate hydrate samples previously produced under various autoclave curing conditions were analyzed by X-ray diffraction and the thermal shrinkage rate was measured, and the correlation between the peak intensity at a given diffraction angle and the thermal shrinkage rate based on the peak intensity at the predetermined diffraction angle obtained by comparing the measurement result obtained by measuring the thermal contraction rate of the calcium silicate hydrate to be quantified with the correlation. A method for quantifying a xonotlite formation rate, characterized in that the xonotlite formation rate is determined by 2. The method of quantifying xonotlite production rate according to claim 1, wherein the calcareous raw material powder comprises portland cement. 3. The method for quantifying the xonotlite production rate according to claim 1 or 2, characterized in that the predetermined diffraction angle is 2[theta]=12.6[deg.] indicating the xonotlite (001) plane. Quantification of the xonotlite production rate according to any one of claims 1 to 3, characterized in that the thermal shrinkage rate is a thermal shrinkage rate within a range of 700 to 900 ° C. measured with a thermomechanical analyzer. Method.

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