JP7256648B2 - Cement composition evaluation method and manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for evaluating caking property that enables easy and quick estimation of caking state during storage and transportation of a cement composition, etc., and a method for producing a cement composition, etc., comprising the evaluation process. .

Since cement compositions are generally concerned about weathering due to moisture absorption, etc., the number of days from manufacture and shipment to use is set short. However, if it is not possible to ship as planned due to circumstances such as the shipping environment or transportation environment, there may be concerns about caking during the storage period depending on the structure of the silo or tank and the loading height in the silo. . In addition, in marine transportation, depending on the season and route, if the transportation distance is long, the transportation time will be long, and the inside of the tank of the transportation ship may become hot and humid. In such long-term storage, the cement composition may solidify depending on the temperature and humidity of the storage location.

Powders such as granulated blast furnace slag and fly ash, as well as cement compositions, have the property of caking due to moisture in the air, and depending on the caking state, they may be difficult to use. Powders such as cement compositions and ground granulated blast furnace slag, which have the property of being hardened by moisture in the air, are called hardening powders. Depending on the state of solidification, it may be difficult to carry out or extract the product, which not only requires a large transportation cost, but also requires processing costs such as crushing even if it is disposed of. In addition, there is a problem that the usage efficiency of the storage facility may be remarkably lowered.

The above caking phenomenon is caused not only by simply absorbing moisture from the external environment, but also varies depending on the cement composition and the powder components. For example, when a small amount of soluble components such as free calcium oxide and alkali sulfate contained in these cohesive powders are distributed on the particle surface, cross-linking between particles is likely to occur due to moisture absorption. In addition, in environments where large amounts of caking powder are stored, such as silos and ship holds, the weight of the caking powder increases the pressure at the bottom of the storage container, resulting in stronger caking properties. It may become difficult to store more than a certain amount.

In cement compositions and caking powders such as the above powders, the caking ability varies depending on the type of individual powder, and even for the same type of powder, it varies depending on the character and properties of the powder, etc. isn't it. Therefore, the caking properties of these caking powders should be evaluated in advance before they are brought into a storage facility or ship. Countermeasures such as lowering the loading height of the tank and controlling the temperature and humidity within a range where caking is difficult are being considered.

The following methods are known as methods for judging the setting properties of cement compositions and the like.
(B) In Japanese Patent No. 2950331, fly ash is packed in a container so that a standard rod used for a cement setting test is inserted to a specific depth, and the container is placed at a relative humidity of 100% (RH = 100%). A method is described in which the fly ash is allowed to absorb moisture by placing it in a humidity chamber close to 100°C, measuring the penetration depth of the above standard rod, and judging the caking property of the powder from the change over time.
(B) Japanese Patent Application Laid-Open No. 2011-144070 discloses that fly ash is allowed to stand for 18 hours in a constant temperature and humidity chamber at a relative humidity of 66% and a temperature of 32 ° C., and then the pack set index is A method for determining caking by measuring is described.
(C) Japanese Patent Application Laid-Open No. 2002-286220 discloses that a container is filled with fly ash, and the container is allowed to stand in a constant temperature and humidity environment with a relative humidity of 100% and a temperature of 30° C. for 24 hours. A method of measuring the shear strength of fly ash by the vane method and judging the caking property from the increase in the shear strength is described.

(E) In Japanese Patent No. 6069119, after a high-humidity step of leaving fly ash to stand for 4 to 10 hours in an environment with a temperature of 0 to 30°C and a relative humidity of 50% or more, Perform a low-humidity process in which the product is left to stand in an environment with a temperature of 40 to 80 ° C and a relative humidity of 0 to 40% until it reaches a constant weight, observe the caking property before and after these steps, and compare the values to determine the caking property It describes how to judge.
(F) In Non-Patent Document 1, fly ash is left at a humidity of 90% and a temperature of 20 ° C., a Vicat needle standard rod is inserted into it, and the amount of penetration is measured from 1 to 5 d to determine the caking property. It describes how to do it.
(G) Non-Patent Document 2 describes a method in which fly ash is left for 24 hours in an environment with a relative humidity of 100% and a temperature of 20 ° C., and the caking property is determined by comparing the penetration resistance values before and after the standing. Are listed.

Japanese Patent No. 2950331 JP 2011-144070 A Japanese Patent Application Laid-Open No. 2002-286220 Japanese Patent No. 6069119

Shunichiro Naito et al., "Clarification of coal ash caking mechanism - part 1", The 110th Annual Meeting of the Japan Society of Inorganic Materials, Abstracts, June 2, 2005, Japan Society of Inorganic Materials. Noboru Nagakai et al., "Caking of fly ash and its prevention method," Cement Concrete, The Cement Association, August 1969, No. 270, pp. 22-29

All of the conventional determination methods described above are methods for measuring powder that has been made to absorb moisture under constant temperature and humidity conditions, and do not consider the effects of pressure applied to powder during storage or transportation. For this reason, there is a problem that the caking property caused mainly by pressurization cannot be properly evaluated in an environment of low humidity.

The present invention solves the above-mentioned problems in the conventional method for judging the caking property, and evaluates the caking property of caking powder such as a cement composition in consideration of the pressure due to the weight of the powder during storage. provide a way. The present invention also provides a method for producing a cement composition, which includes the step of evaluating caking properties.

The present invention relates to a method for evaluating caking property having the following constitution and a method for producing a cement composition having the method for evaluating caking property.
[1] A method for evaluating the caking property of a caking powder having the property of caking, characterized by comprising the following steps (a), (b) and (c).
(a) a step of filling the caking powder into a container;
(b) a pressure heating step of leaving the caking powder filled in the container under pressure of 0.1 to 2.0 MPa and a temperature of 30° C. to 90° C. for a certain period of time;
(c) After the pressurization and heating process, the container is impacted and the caking property is evaluated by the number of impacts and the collapse state of the powder, or the first needle is inserted into the powder in the container at a constant pressure, and the first An evaluation process that evaluates the caking properties of the powder by the penetration depth of the needle.
[2] In the evaluation process, the container is impacted by the following (a), (b), or (c) method, and the solidification of the powder is determined by the number of times that more than half of the powder in the container falls out of the container. The method for evaluating caking property described in [1] above for evaluating caking property.
(b) a method of applying impact by dropping the container from a predetermined height with the opening of the container facing downward;
(b) A method of placing a container on a flow table specified in the standard (JIS R 5201) and repeatedly dropping the flow table with a predetermined amplitude to apply an impact.
(C) A method of applying shock by fixing the container to a table vibrator used for filling mortar molds specified in the standard (JISR5201) and vibrating it with a predetermined amplitude and frequency.
[3] A method for producing a cement composition, comprising evaluating the caking properties of the powder by the following steps (a), (b) and (c).
(a) a step of filling the caking powder into a container;
(b) a pressure heating step of leaving the caking powder filled in the container under pressure of 0.1 to 2.0 MPa and a temperature of 30° C. to 90° C. for a certain period of time;
(c) After the pressurization and heating process, impact the container and evaluate the caking property based on the number of impacts and the collapse state of the powder, or insert the first needle into the powder in the container and Evaluation process for assessing body consolidation.
[4] In the production method described in [3] above, the powder caking property evaluation step by the above steps (a), (b) and (c) is provided after the raw material pulverization step or classification step, or A method for producing a cement composition, wherein the index of caking property obtained by the caking property evaluation step is fed back to the pretreatment step of the cement composition producing step.

The method of the present invention will be specifically described below.
The caking property evaluation method of the present invention uses powders (caking property It is a method for evaluating the caking property of powder).

Specifically, the caking property evaluation method of the present invention is a caking property evaluation method characterized by having the following steps (a), (b), and (c).
(a) a step of filling the caking powder into a container;
(b) a pressure heating step of placing the caking powder filled in the container in an environment of pressure 0.1 to 2.0 MPa and temperature of 30° C. to 90° C .;
(c) After the pressurization and heating process, the container is impacted and the caking property is evaluated by the number of impacts and the collapse state of the powder, or the first needle is inserted into the powder in the container at a constant pressure, and the first An evaluation process that evaluates the caking properties of the powder by the penetration depth of the needle.

[Filling process]
In the filling step, the container is filled with the caking powder. The container may be, for example, a cylindrical container having an inner diameter of 50 mm and a height of 100 mm. Using a cylindrical container whose opening is closed by a pressurizing stem facilitates pressurization in the next step. The caking powder is filled into the container to a height of 50 mm to 60 mm (approximately half the height of the container) by, for example, tapping several times, and the top surface is flattened. The environment of the filling process is preferably normal temperature (around 25° C.) and relative humidity around 40%.

[Pressure heating process]
After the filling step, the above stem is pressed against the upper surface of the caking powder filled in the container, and a pressure of 0.1 to 2.0 MPa is continuously applied to the caking powder throughout the stationary period, and the temperature is 30. C. to 90.degree. C. for one week. As a heating method, a heater may be provided on the outer circumference of the container to heat the container to a temperature of 30° C. or higher and 90° C. or lower. The magnitude of the pressure, the heating temperature, and the standing period may be determined according to, for example, the transportation period, the storage conditions, and the storage period. If the pressure is less than 0.1 MPa, the solidified state cannot be sufficiently reproduced, and if the pressure exceeds 2 MPa, the powder in the container becomes too hard, making it difficult to produce a difference in evaluation. Also, if the temperature is less than 30°C, the solidified state cannot be sufficiently reproduced, and if it exceeds 90°C, the powder in the container becomes too hard, making it difficult to produce a difference in evaluation.

If the pressure range (0.1 to 2.0 MPa), temperature range ( 30°C to 90°C ), and standing period (1 week) are taken as the standard conditions, the powder of the sample will be a general solid state. Connectivity can be evaluated. Further, if the standing period is determined according to the transportation period and the storage period, it is possible to evaluate the caking property of the sample powder under specific implementation conditions.

[Evaluation process]
After the pressurization and heating step, impacts are applied to the container, and the caking property is evaluated based on the number of impacts and the collapsed state of the powder. Specifically, for example, by dropping the container from a predetermined height, for example, 30 mm, with the opening of the container facing downward, an impact is applied, and more than half of the powder in the container collapses out of the container. The caking property of the powder is evaluated by the number of drops.
For example, based on the number of drops of 5 times, if the number of drops is less than 5 times and more than half of the powder in the container collapses out of the container, it is considered to be non-caking, while more than half of the powder in the container is considered to be non-caking. If it takes 5 times or more to collapse out of the container, it is considered to have caking properties.
In addition, it is possible to relatively evaluate the solidification property of the powder based on the number of drops. For example, for powder X in which more than half of the powder in the container collapses out of the container by falling seven times, and powder Y in which more than half of the powder in the container collapses out of the container by falling 12 times, It can be seen that the powder X has a lower caking property than the powder Y.

The drop impact method may be a method using a flow table shown in the standard (JIS R 5201 "Physical Test Method for Cement"). Specifically, the container that has undergone the pressurization and heating process is placed on the flow table with its opening facing downward, and is repeatedly dropped with a predetermined amplitude to apply impact. Specifically, the flow table is repeatedly dropped at a predetermined height, for example, 10 mm, and when the container is lifted from the table, the number of times more than half of the powder in the container collapses out of the container. Evaluate the caking properties of the powder.

A drop test using a flow table can eliminate artificial test errors as much as possible. In the drop test without a flow table (direct drop test), the test piece is dropped from a height of 30 mm. Since the force is less than in the direct drop test, the number of times more than half of the powder in the container is dropped tends to be greater than in the direct drop test.

In addition, evaluation using a vibrating vibrator can also be performed. Specifically, for example, using a table vibrator used for filling mortar molds stipulated in the standard (JISR5201), fix the container to this, vibrate it for a certain period of time at a predetermined amplitude and frequency, and drop it. Evaluation methods can be used to check for the presence or absence of For example, the amplitude of the vibrator should be 0.80±0.05 mm and the frequency of the vibrator should be 2800±50 times/minute. Moreover, the caking standard may be evaluated based on the vibration time applied to the container.

As a method for evaluating the caking property of the powder, a method of inserting a first needle into the powder in the container under a constant pressure and evaluating by the state of penetration thereof may be used. Using the coagulation test equipment specified in the standard (JIS R 5201 "Physical test method for cement"), insert the initial needle into the upper surface of the powder in the container that has undergone the pressure heating process, and depending on the penetration depth The caking properties of the powder are evaluated.
Specifically, for example, powder with a penetration depth of less than 1 mm is evaluated as having caking properties, and powder with a penetration depth of 1 mm or more is evaluated as having no caking properties. The measurement conditions such as the shape of the starting needle and the insertion pressure should be in accordance with the above standard (JIS R 5201 "Physical test method for cement").
The caking property of the powder can be judged by the penetration test of the first needle as well as the drop test.

The present invention includes a method for producing a cement composition having a step of evaluating caking properties by the above steps (a), (b) and (c).

According to the evaluation method of the present invention, for caking powders such as cement compositions, ground granulated blast furnace slag, fly ash, etc., which have the property of caking by compaction due to moisture in the air or powder's own weight, The caking property can be evaluated considering the pressure exerted on the powder during loading, storage or transport.

Further, by introducing the evaluation method of the present invention into the production process of cement compositions, etc., caking can be prevented during the production of cement compositions, etc. For example, in the production of a cement composition or the like, if the evaluation method of the present invention is introduced after the pulverization step or the classification step, caking of raw material powder can be prevented. In addition, the caking property index obtained by the evaluation method of the present invention may be fed back to the manufacturing process of the cement composition or the like or its pretreatment process.

Examples of the present invention are shown below together with comparative examples.
Table 1 shows the physical properties of cement compositions A to D used. The degree of compression in Table 1 is defined by the following equation. The higher the degree of compaction, the lower the fluidity of the powder, and the degree of compaction of general cement is approximately 50%.
Compression degree (%) = 100 × (solidified bulk density - loosened bulk density) / consolidated bulk density Solidified bulk density: bulk density when powder is put in a container and compacted Loose bulk density: powder is put into a container Bulk density when filled and not compacted

[Example 1]
Each of the cement compositions A to D shown in Table 1 was filled in two layers in an acrylic cylindrical container (inner diameter: 50 mm, height: 100 mm) to a height of 50 to 60 mm while tapping. Next, an acrylic cylinder having a smooth pressing surface was inserted into the container, and the upper surface of the powder was lightly pressed to level it. Cement compositions A to D were filled in three containers each. The temperature during filling was 25° C. and RH 40% (filling process).
Next, the cylinder is pushed in to apply pressure of 0.1 MPa, 0.5 MPa, and 1.6 MPa to the powder in the container, and the pressure is maintained, and the container is further heated to a temperature range of 30 ° C. (normal temperature) to 90 ° C. and held for one week (pressure heating step).
After the filling step and pressure heating step, the containers containing the cement compositions A to D are turned upside down with the opening facing downward, and the standard (JIS R 5201 “Physical test method for cement”) is described. Installed on a flow table, the flow table is dropped with an amplitude of 10 mm, repeatedly impacting the powder in the container, and measuring the number of drops until more than half of the powder in the container collapses outside the container. (evaluation process). The results are shown in Table 2.

[Example 2]
Cement compositions A to D used in Example 1 were filled in a cylindrical container in the same manner as in Example 1, and after similarly holding for one week under pressure and heating, the container was turned upside down and the opening was exposed. was turned downward and dropped from a height of 30 mm, and the number of drops until more than half of the powder in the container collapsed out of the container was counted. The results are shown in Table 2.

Twelve or more drops in the flow table drop test (Example 1) and five or more drops in the direct drop test (Example 2) were evaluated as having caking properties. The results are shown in Table 2.

[Example 3]
After each of the above cement compositions A to D was transported for three weeks without adjusting the temperature and humidity inside the transport ship, it was confirmed whether the powder was solidified when discharged from the hold. The results are shown in Table 3. Cement compositions A and B that were dropped 12 or more times in the flow table drop test, and cement compositions A and B that were dropped 5 or more times in the direct drop test, both solidified during transportation. On the other hand, the cement compositions C and D, which were judged to be "no caking" in the flow table drop test and the direct drop test, did not caking even during actual transportation. , 2 gave results in good agreement with actual long-term transportation.

Claims (4)

A method for evaluating the caking property of a caking powder having the property of caking, characterized by comprising the following steps (a), (b) and (c).
(a) a step of filling the caking powder into a container;
(b) a pressure heating step of leaving the caking powder filled in the container under pressure of 0.1 to 2.0 MPa and a temperature of 30° C. to 90° C. for a certain period of time;
(c) After the pressurization and heating process, the container is impacted and the caking property is evaluated by the number of impacts and the collapse state of the powder, or the first needle is inserted into the powder in the container at a constant pressure, and the first An evaluation process that evaluates the caking properties of the powder by the penetration depth of the needle. In the evaluation process, impact is applied to the container by the following (a), (b), or (c) method, and the caking property of the powder is evaluated by the number of times that more than half of the powder in the container collapses out of the container. The method for evaluating caking property according to claim 1.
(b) a method of applying impact by dropping the container from a predetermined height with the opening of the container facing downward;
(b) A method of placing a container on a flow table specified in the standard (JIS R 5201) and repeatedly dropping the flow table with a predetermined amplitude to apply an impact.
(C) A method of applying shock by fixing the container to a table vibrator used for filling mortar molds specified in the standard (JISR5201) and vibrating it with a predetermined amplitude and frequency. A method for producing a cement composition comprising a step of evaluating the caking property of powder by the following steps (a), (b) and (c).
(a) a step of filling the caking powder into a container;
(b) a pressure heating step of leaving the caking powder filled in the container under pressure of 0.1 to 2.0 MPa and a temperature of 30° C. to 90° C. for a certain period of time;
(c) After the pressurization and heating process, impact the container and evaluate the caking property based on the number of impacts and the collapse state of the powder, or insert the first needle into the powder in the container and Evaluation process for assessing body consolidation. In the production method according to claim 3, the powder caking property evaluation step by the above steps (a), (b) and (c) is provided after the raw material pulverization step or classification step, or the caking property A method for producing a cement composition in which the caking property index obtained in the evaluation step is fed back to the pretreatment step of the cement composition production process.