JP6537307B2 - Method of treating cement composition - Google Patents

Description

  The present invention relates to aggregated silica fume (hereinafter referred to as “aggregated silica fume”) and / or granular silica fume (JIS A 6207) in a cement composition containing silica fume (hereinafter referred to simply as “cement composition”). The invention relates to a method of determining the abundance of the silica fumes described and to a method of treating cement compositions comprising agglomerated silica fumes and / or granular silica fumes.

Recently, silica fume is frequently used as an additive for high strength mortar and high strength concrete.
However, fine silica fume with a BET specific surface area of 15 m ² / g or more tends to partially aggregate during storage to form heterogeneous aggregates, and a premix type cement in which such silica fume and Portland cement are mixed The composition often has the problem of containing agglomerated silica fume. In addition, even when non-aggregated silica fume is used, in the case of a premix type cement composition containing silica fume having a BET specific surface area of 15 to 25 m ² / g, the silica fume is contained after half a year after production. There is a problem of aggregation. Kneading of mortar and concrete (hereinafter referred to as "mortar and the like") using such cement composition requires time for crushing aggregated silica fume, and is a cement composition containing non-aggregated silica fume at the time of production The kneading time is longer than that of mortar and the like, and the production efficiency of the mortar and the like is reduced accordingly.

When silica fume having a BET specific surface area of 12 to 25 m ² / g is used as an admixture, the silica fume is often processed into a granular form for shipment for the purpose of improving storage performance and workability at the time of transportation. . However, kneading of a mortar or the like using a cement composition containing the granular silica fume also requires a time for crushing the granular silica fume, so the kneading time becomes long.

By the way, in relation to the determination method of the cement composition,
Patent Document 1 proposes a method of determining the quality of silica fume. Specifically, the method applies external force to silica fume in water, measures changes in particle size distribution of silica fume and changes in parameters related to particle size distribution before and after applying external force, and determines the quality of silica fume It is a method. Also,
In patent document 2, the measuring method of the largest dimension of solid content in aqueous slurry is proposed. Specifically, the method adds a colorless and transparent molasses-like diluted solution to the slurry, and microscopically observes the state of aggregation and dispersion of particles in the slurry, and solid content consisting of single particles and aggregated particles Is a method of measuring the largest dimension of
However, the method described in Patent Document 1 does not aim to determine the state of aggregation in silica fume, and the method described in Patent Document 2 observes individual particles with a microscope to measure the maximum dimension, and thus takes time and effort. It takes.

Furthermore, in relation to the method of treating the cement composition,
Patent Document 3 proposes a method of producing high-strength cement using silica fume in the form of granules (granules). Specifically, when pulverizing cement clinker, the method adds a granular material having a particle diameter of less than 2 mm, which comprises cement clinker and ultrafine particles such as silica fume having a particle diameter of 1 μm or less, and a grinding aid It is a method of crushing. Then, according to the method, the proportion of ultrafine particles dispersed as single particles in cement is significantly increased, and the fluidity and strength development of cement are improved. However, even with this cement, when it is produced for more than half a year, the dispersed silica fumes aggregate to form agglomerated particles, and the mortar using cement containing the silica fume has a kneading time There is a problem of becoming long.

Japanese Patent Application Laid-Open No. 07-035676 JP, 2012-137411, A Unexamined-Japanese-Patent No. 5-147984 gazette

  Therefore, according to the present invention, there is provided a method capable of easily determining the amount of agglomerated silica fume and / or granular silica fume in a cement composition, and a cement composition determined to contain agglomerated silica fume and the like based on the determination method, An object of the present invention is to provide a method for treating such that the kneading time of mortar or the like containing the cement composition is shortened.

The inventor examined the determination method and the processing method meeting the object,
(i) The longitudinal relaxation time of the paste of the cement composition, which is measured using a pulse NMR measurement apparatus, is an index for determining the amount of aggregated silica fume or the like.
(ii) A mortar using a cement composition obtained by stirring a cement composition containing aggregated silica fume and the like using a specific mixer was found to shorten the kneading time, and the present invention was completed.
That is, the present invention is a method of judging a cement composition having the following constitution.

[1] After adjusting the slurry of the cement composition, within 5 seconds, was measured using a pulsed NMR measurement apparatus, the longitudinal relaxation time of the slurry,
It is determined that the cement composition exceeding the standard value of the longitudinal relaxation time determined from the fluidization time of the mortar satisfying the required performance is rich in agglomerated silica fume and / or granular silica fume,
A method of treating a cement composition, wherein the cement composition is subjected to agitation processing using a Pro-shear mixer, an Eirich mixer, or a Henschel mixer .

  According to the method of determining a cement composition of the present invention, the amount of aggregated silica fume and / or granular silica fume in the cement composition can be easily determined. Further, according to the method for treating a cement composition of the present invention, since the kneading time of mortar or the like using a cement composition containing agglomerated silica fume and / or granular silica fume can be shortened, the production efficiency of these can be improved.

It is a figure which shows the correlation of the longitudinal relaxation time of the paste of a cement composition, and the fluidization time of the mortar using this cement composition. It is a schematic diagram showing an example of a pro shear mixer. It is a figure which shows the flow and fluidization time of the mortar containing the cement composition A processed using a proshear mixer a of a postscript, Comprising: (1) shows the effect of stirring time, (2) is a rotational speed of a chopper (3) shows the effect of the peripheral speed of the shovel blade. It is a figure which shows the flow and the fluidization time of the mortar containing the cement composition C processed using the post-shear mixer a of a postscript, Comprising: The effect of stirring time is shown. It is a figure which shows the flow and fluidization time of the mortar containing the cement composition A processed using a post-seal pros-a-mixer b later, Comprising: The effect of stirring time is shown.

The determination method of the cement composition of the present invention is, as described above, based on the longitudinal relaxation time of the paste of the cement composition measured using a pulse NMR measuring device, aggregated silica fume and / or granular silica fume in the cement composition Is a method of determining the degree of
Further, the method of treating a cement composition according to the present invention has a blade-shaped stirring blade having a cement composition determined to contain a large amount of aggregated silica fume and / or granular silica fume based on the method of determining a cement composition. It is a method of stirring processing using a mixer.
Hereinafter, the present invention will be described in detail, divided into a method of judging a cement composition and a method of treating a cement composition.

1. Determination Method of Cement Composition (1) Cement Composition The cement composition to be determined in the present invention is a composition containing silica fume and cement.
(I) Silica fume The BET specific surface area of agglomerated silica fume or granular silica fume contained in the cement composition is usually 12 to 25 m ² / g. Silica fume whose value falls outside this range is difficult to obtain. The BET specific surface area is preferably 13 to ²⁰ m ² / g.
Here, the aggregated silica fume refers to, for example, silica fume in which the ratio of particles having a particle diameter of 1 μm or more measured by a laser diffraction / scattering type particle size distribution measuring apparatus is 20% by mass or more. In addition, even if it uses the silica fume which is not aggregated for manufacture of a cement composition, when it passes for half a year or more after manufacture, the silica fume contained in a cement composition tends to aggregate. Further, depending on storage conditions, silica fume contained in the cement composition may coagulate within several months after production.
Granular silica fume refers to silica fume described in JIS A 6207.

(Ii) Cement The cement contained in the cement composition includes one or more types of Portland cement selected from the group consisting of ordinary Portland cement, early-strength Portland cement, moderate heat Portland cement, and low-thermal Portland cement.
Among these cements, medium heat Portland cement and low heat Portland cement are preferable from the viewpoint of fluidity and workability of mortar and the like.

(2) Composition of Cement Composition The composition of the cement composition is preferably 5 to 40 parts by mass of silica fume per 100 parts by mass of cement. When the value is in the above range, the cement composition has high fluidity and strength development. The composition of the cement composition is more preferably 8 to 35 parts by mass, still more preferably 10 to 30 parts by mass, with respect to 100 parts by mass of cement.
The cement composition may also include additives such as limestone powder, quartz powder, gypsum, fly ash, coal ash, blast furnace slag, and expansive agents. The blending amount of the admixture is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, with respect to 100 parts by mass of cement.

(3) Measurement of Longitudinal Relaxation Time of Slurry of Cement Composition Using Pulsed NMR Measurement Device Next, measurement of the vertical relaxation time used as an index in the method of determining a cement composition of the present invention will be described.
In the longitudinal relaxation time (T ₁ ), after inserting a sample tube containing a slurry of cement composition into a coil between two permanent magnets in a pulse NMR measurement apparatus, the coil is irradiated with an electromagnetic wave pulse. Measure. The slurry of the cement composition is subjected to measurement preferably within 10 seconds after preparation. After 10 seconds after the preparation of the slurry, the measurement error of the longitudinal relaxation time may become large. The time until the measurement is performed is more preferably within 5 seconds.

  The protons in the slurry of the cement composition align in the direction of the static magnetic field due to the static magnetic field between the two permanent magnets after several seconds of inserting the sample tube into the coil. In this state, when the coil is irradiated with an electromagnetic wave pulse of about 14 MHz to excite the coil, the proton is temporarily induced in the direction of the magnetic field by the large oscillating magnetic field generated. Then, when the induction stops, the protons align again in the direction of the static magnetic field and return to the original state. A longitudinal relaxation time is one of the times from irradiation to excitation to return to the original stable state. In order to know the longitudinal relaxation time, it is necessary to irradiate a plurality of pulses at a timing that matches the longitudinal relaxation time.

(4) Determination of cement composition A cement composition is prepared by mixing cement and silica fume, and the longitudinal relaxation time of the paste of the cement composition after a predetermined period has passed and the mortar composition using the cement composition There is a positive correlation with the fluidization time as shown in Table 1 and Figure 1 below. And, in the example of FIG. 1, the fluidization time of the mortar is largely different when the longitudinal relaxation time is 75 ms. This difference in fluidization time is related to the amount of agglomerated silica fume that is produced over time after mixing.
However, the criteria for determining the amount of aggregated silica fume and / or granular silica fume in the cement composition are relative, for example, when evaluating the cement composition by the fluidization time of mortar using the cement composition, the requirement A fluidization time value satisfying the performance is determined, and a longitudinal relaxation time reference value is determined from the value. Then, when the reference value is satisfied, it is determined that the content of the agglomerated silica fume and / or the granular silica fume in the cement composition is small. For example, in the example of FIG. 1, when the reference value of the longitudinal relaxation time is set to 75 ms, it is determined that the aggregated silica fumes are small at 75 ms or less and the aggregated silica fumes are large at more than 75 ms.

2. Method for Treating Cement Composition The method for treating a cement composition according to the present invention comprises a cement composition that is determined to contain aggregated silica fume and the like based on the method for determining a cement composition, such as a mortar containing the cement composition. It is a method of processing using a specific mixer so as to shorten the kneading time.
(1) Mixer The specific mixer is a mixer having a blade-like stirring blade, and examples thereof include a proshear mixer, an Eirich mixer, and a Henschel mixer. Each of these mixers is equipped with a blade-like high-speed stirring blade (chopper or rotor) having a strong dispersing force (shearing action), and its rotational speed can be adjusted in a range of approximately 1000 rpm to 6000 rpm.
The pro shear mixer is mainly composed of a shovel blade 1 and a chopper 2 as shown in FIG. 2 as an example, and the powder material charged from the material charging port 3 is a floating diffusion mixing by mixing action of the shovel blade 1 After being dispersed and mixed by high-speed shear dispersion by the dispersing action of the chopper 2, the mixer discharges powder from the material outlet. When a pro shear mixer is used as a mixer, a pro shear mixer having a stirring capacity of preferably 2000 rpm or more, more preferably 3000 rpm or more is desirable. The pro shear mixer is, for example, a pro shear mixer manufactured by Pacific Kikko Co., Ltd., and examples thereof include WB-20 (inclined type) and WB-2400.
Further, the Eirich mixer is, for example, an Eirich mixer manufactured by Nippon Eirich Co., Ltd., and its type includes R02. The Henschel mixer is, for example, the Henschel mixer manufactured by Nippon Coke Industry Co., Ltd., and the type thereof is FM20C.
In the present invention, by stirring using the mixer having the blade-like stirring blade, agglomerated silica fume and / or granular silica fume in the cement composition is crushed, and the kneading time of mortar and concrete is shortened. I guess that will be.

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to the examples.
1. Materials used (1) Cement composition A
Aggregated silica fume with a BET specific surface area of 18.5 m ² / g (metallic silicone, particles with a particle size of 1 μm or more have a proportion of 30% by mass, density 100% by mass) to 100 parts by mass of moderate heat Portland cement (manufactured by Pacific Cement Co., Ltd.). Cement composition containing 13 parts by mass of 25 g / cm ³ (manufactured by Emchem Japan Ltd.) (2) Cement composition B
A non-aggregated silica fume with a BET specific surface area of 18.5 m ² / g (metallic silicone, particles with a particle size of 1 μm or more have a proportion of 10 mass%) per 100 parts by mass of moderate heat Portland cement (manufactured by Pacific Cement Co., Ltd.) Cement composition containing 13 parts by mass of density 2.25 g / cm ³ (manufactured by Emchem Japan Ltd.) (3) Cement composition C
Cement composition B (including agglomerated silica fume) 12 months after production
(4) Fine aggregate mountain sand (from Kakegawa City, Shizuoka Prefecture)
(5) High-performance water reducing agent Masterglenium SP8 HU X ₂ (registered trademark) (manufactured by BASF Japan Ltd.)
(6) Air amount regulator Master Air 404 (registered trademark) (manufactured by BASF Japan Ltd.)
(7) Water: tap water

2. Composition of mortar and measurement method of fluidization time and flow of mortar The composition of this mortar is the mass ratio of water / cement composition 0.14, mass ratio of fine aggregate / cement composition 0.33, high performance The amount of the water reducing agent added is the mass of the cement composition × 1.5%. In addition, the air amount of mortar was adjusted to 3% or less using an air amount adjusting agent.
According to the said mixing | blending, the raw materials of mortars, such as a cement composition, were collectively put into the Hobart mixer, knead | mixed at low speed, and fluidization time (second) was measured. The properties of the mortar containing the cement composition to be treated according to the present invention show a unique change that initially changes from powdery to gradually large lumps and changes to a fluidized state when mixed further. The fluidization time is the time from the start of kneading to the fluidization state. The kneading time of the mortar was set to the fluidization time + 180 seconds.
Next, the flow of mortar was measured according to JIS R 5201 "Physical test method of cement 11. flow test" using the kneaded mortar. However, 15 fall movements were not conducted.

3. Measurement of Longitudinal Relaxation Time of Cement Composition and Determination Based on the Time The cement composition B was prepared, then placed in a plastic bag and stored under conditions of 30 ° C. and relative humidity 80%. At the elapse of the storage period described in Table 1, 3 g of cement composition B and 3 g of distilled water were mixed to prepare a slurry of cement composition B. Next, the slurry is put into a sample tube, and the sample tube is inserted into a coil in a pulse NMR measurement apparatus (made by XiGo Nanotools, USA), and then the coil is irradiated with an electromagnetic wave pulse to produce an environment of 20 ° C. The longitudinal relaxation time under was measured 5 times per sample, and the average value was determined.
In addition, at the elapse of the storage period described in Table 1, the mortar was prepared using cement composition B, and the fluidization time of the mortar was measured according to the method described above. The longitudinal relaxation time (average value) and fluidization time obtained by measurement here are shown in Table 1 and FIG.

  As shown in FIG. 1, there is a positive correlation between the longitudinal relaxation time of the paste of the cement composition and the fluidization time of the mortar using the cement composition, and the longitudinal relaxation time is 75 ms. , The fluidization time of mortar is greatly different. And since a fluidization time becomes long, so that a storage period is long, it can be judged that flocculated silica fume in a cement composition has few vertical relaxation time in 75 ms or less, and many in 75 ms.

4. Treatment of cement composition (1) Mixer and mixing conditions used for the treatment (i) Professional shear mixer a
Model: WB-20 (tilted type), rotation speed of chopper: 3600-6000 rpm, circumferential speed of chopper: 18 m / s or more, volume: 20 liters, Pacific Kiko Co., Ltd. (ii) Professional shear mixer b
Model: WB-2400, chopper rotation speed: 3600 rpm, chopper circumferential speed:
28 m / s, volume: 2.3 m ³ , manufactured by Pacific Kiko Co., Ltd. The input amount of the cement composition to the professional shear mixer was 8.4 kg for the professional shear mixer a and 800 kg for the professional shear mixer b.

(2) Treatment of cement composition B stored for 12 weeks using the pro shear mixer a The peripheral speed of the shovel blade is 4.2 m / s and the rotational speed of the chopper is 6000 rpm using the pro shear mixer a The cement composition B stored for 12 weeks was stirred for 10 minutes. After stirring, the mortar was prepared using this cement composition B, and when the fluidization time of the mortar was measured, the fluidization time was as short as 110 seconds.

(3) Treatment of cement composition A using professional shear mixer a (i) Effect of agitation time The peripheral speed of the shovel blade of the professional shear mixer a is 4.2 m / s, and the rotational speed of the chopper is 6000 rpm. The cement composition A was stirred for 15 minutes, 10 minutes, 5 minutes and 3 minutes. The mortar was prepared using cement composition A after stirring, and the flow and fluidization time of the mortar were measured. The result is shown in (1) of FIG.
As shown in (1) of FIG. 3, the fluidization time of the mortar decreases as the stirring time increases.

(Ii) Effect of rotation speed of chopper With the circumferential speed of the shovel blade of the professional share mixer a being 4.2 m / s and the stirring time being 10 minutes, the rotation speed of the chopper was 6,000 rpm for the cement composition A. , 4800 rpm, and 3600 rpm. A mortar was prepared using cement composition A after stirring, and the flow and fluidization time of the mortar were measured. The result is shown in (2) of FIG.
As shown in FIG. 3 (2), the fluidization time of the mortar decreases as the rotational speed of the chopper increases.

(Iii) Effect of peripheral speed of shovel blade The above-mentioned cement composition A and the peripheral speed of shovel blade are 4.2 m / under the conditions that the rotational speed of the chopper of the professional shear mixer a is 3600 rpm and the stirring time is 10 minutes. Stirred at s, and 3.5 m / s. A mortar was prepared using cement composition A after stirring, and the flow and fluidization time of the mortar were measured. The result is shown in (3) of FIG.
As shown in FIG. 3 (3), the fluidization time of the mortar tends to be shortened as the peripheral speed of the shovel blade is larger.

(3) Treatment of cement composition C using pro shear mixer a The cement composition C under the conditions that the peripheral speed of the shovel blade of the pro shear mixer a is 3.5 m / s and the rotational speed of the chopper is 3600 rpm The mixture was stirred for 10 minutes and 15 minutes. The mortar was prepared using cement composition C after stirring, and the flow and fluidization time of the mortar were measured. The results are shown in FIG.
As shown in FIG. 4, in the cement composition C (untreated) before stirring, the fluidization time is long, so it is considered that the silica fume is aggregated. And, the longer the stirring time, the larger the flow value of the mortar and the shorter the fluidization time.

(4) Treatment of cement composition A using the professional shear mixer b: The peripheral speed of the shovel blade of the professional shear mixer b (actual machine for factory) is 3.5 m / s, and the rotational speed of the chopper is 3600 rpm The cement composition A was stirred for 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 45 minutes and 60 minutes. The mortar was prepared using cement composition A before (untreated) and after stirring, and the flow and fluidization time of the mortar were measured. The results are shown in FIG.
As shown in FIG. 5, the longer the stirring time, the shorter the fluidization time of the mortar.
From the above results, the method for treating a cement composition of the present invention can shorten the kneading time of mortar and concrete using a cement composition containing aggregated silica fume, and the production efficiency of mortar and concrete is improved.

1 Excavator blade 2 Chopper 3 Material inlet 4 Material outlet

Claims (1)

After adjusting the slurry of the cement composition, within 5 seconds, it was measured using a pulsed NMR measurement apparatus, the longitudinal relaxation time of the slurry,
It is determined that the cement composition exceeding the standard value of the longitudinal relaxation time determined from the fluidization time of the mortar satisfying the required performance is rich in agglomerated silica fume and / or granular silica fume,
A method of treating a cement composition, wherein the cement composition is subjected to agitation processing using a Pro-shear mixer, an Eirich mixer, or a Henschel mixer .

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