JP7305141B1 - Construction method of cement paste and PC grout for winter - Google Patents

Abstract

[Problem] To provide a winter PC grout that can be used for construction in the cold in a general area at a low cost without taking measures for heating, and a construction method thereof. SOLUTION: This winter PC grout material is formed by kneading at least cement, water and an admixture. The cement is high-early-strength Portland cement, and the admixture is composed of a cement dispersant containing a polycarboxylic acid-based polymer as a main component, a thickener, and an antifoaming agent. 0.20 to 0.40 parts by mass of the cement dispersant, 0.015 to 0.020 parts by mass of the thickener, and 0.010 to 0.015 parts by mass of the antifoaming agent are contained with respect to 100 parts by mass of cement. When the water-cement ratio is 29 to 32% and the curing period is 28 days, the minimum temperature from the 1st day to the 7th day of the initial curing is −12 ° C. and the total time of the day when the temperature is −8 ° C. or less is 6 hours or less. In an environment where the daily average temperature is −6.0 ° C. or higher, the strength of the winter PC grout material is the desired strength or more even if no heating measures are taken during the curing period. [Selection figure] None

Description

The present invention provides a PC grout and a construction method thereof, in which the PC grout, which is constructed in the cold within the range of predetermined conditions, does not freeze in winter, and the desired strength can be obtained without taking measures such as warming during the curing period. It is about.

Conventionally, a PC steel material is inserted into a sheath arranged in a concrete structure, and the prestress is introduced into the structure by tensioning and fixing the PC steel material, and then the sheath is filled with grout (referred to as PC grout). A method of constructing PC structures such as buildings and bridges by a so-called post-tension method is known.

PC grout requires fluidity at the time of filling, and also needs to exhibit sufficient strength after filling. For this reason, the Standard Specifications for Civil Engineering Concrete defines the period in which the average daily temperature is expected to be 4°C or less as the cold season. The standard is that there is no If PC grout is unavoidably injected in the cold, the concrete temperature around the duct (sheath) must be kept at 5°C or higher before injection, and the PC grout temperature must be kept at 5°C or higher for at least 3 days after injection. principle to keep. For this reason, a heating method is adopted in which a heating device is placed outside the member and the entire concrete structure is enclosed (covered) with a cold-proof sheet to heat it. However, it is not only costly and time-consuming to heat it, but also measures against strong winds must be taken into consideration.

On the other hand, conventional techniques relating to PC grout for winter use, in which PC grout that is constructed in the cold does not freeze without special warming measures, are disclosed in a number of patent documents. Patent Document 1 discloses a cement composition for cold weather construction containing cement and a compound capable of releasing cations having a hydrated ion radius three times or more as large as the crystal ion radius. It is disclosed that by using this composition, normal concrete construction can be performed without frost damage even in cold construction at minus 20°C, and the cured product exhibits sufficient strength.

In Patent Document 2, by using an antifreeze cement composition in which an antifreeze cement additive comprising an alkali metal polycarboxylate or an alkaline earth metal polycarboxylate is blended with cement, a cement kneaded product is cooled at a freezing point of -15 ° C. It is disclosed that it is possible to work without using a heating and curing device in cold regions because it does not freeze.

Japanese Unexamined Patent Publication No. 6-234556 Japanese Unexamined Patent Application Publication No. 2007-119268

The prior arts disclosed in Patent Documents 1 and 2 are intended to prevent freezing even at -10°C or lower, which is considered to be the limit of strength development due to the progress of hydration reaction. There are problems in strength development and economy. Especially in extremely cold regions such as Hokkaido, in addition to the severe outside temperature, unspecified factors such as unpredictable snowfall and strong winds greatly affect the initial frost damage of PC grout. It is the present condition that it has not come to be generally used.
In addition, as described above, in the Standard Specifications for Civil Engineering Concrete, when injecting PC grout in the cold, the temperature of the concrete around the duct (sheath) must be 5°C or higher before injecting, and As a general rule, the temperature of PC grout should be kept above 5°C for at least 3 days after injection. It is the most important factor in anti-freezing of PC grout. In other words, as long as the hydration reaction between cement and water progresses reliably without freezing in three days and the initial frost damage can be prevented, it is possible to carry out construction in the cold without freezing the PC grout.

Therefore, the present invention emphasizes workability, economic efficiency and practicality, and in particular, limits the construction method (conditions) during kneading and the outside temperature during the initial curing period (7 days), such as Hokkaido and mountainous areas. Winter PC grout and its construction that can be used in cold weather in general areas at low cost without taking measures to heat it, excluding severe cold regions where the construction environment is strongly affected by snow and strong winds in addition to severe outside temperatures from the scope of application. The purpose is to provide a method.
Although there are various definitions of cold districts administratively and academic guidelines in each field, the present invention conforms to "cold districts" based on the Ministry of Land, Infrastructure, Transport and Tourism "Next Generation Energy Conservation Standards for Housing". All other areas are called general areas.

The cement paste used as the winter PC grout material of the present invention is formed by kneading cement, water, and an admixture alone. The cement is high-early-strength Portland cement, and the admixture comprises only a cement dispersant mainly composed of a polycarboxylic acid polymer, a thickener, and an antifoaming agent, and the cement dispersant is 0.20 to 0.40 parts by mass is contained with respect to 100 parts by mass of the cement; The foaming agent is contained in an amount of 0.010 to 0.015 parts by mass with respect to 100 parts by mass of the cement, and has a water-cement ratio (W/C) of 29 to 32%. When the curing period is 28 days after the injection work of PC grout material is performed, the cumulative time of the day when the lowest temperature is -12 ° C or higher and -8 ° C or lower from the 1st day to the 7th day is 6 hours or less and the average daily temperature is -6.0 ° C or higher, the strength of the cement paste applied in the cold without taking warming measures during the curing period is as follows. characterized by

The cement paste of the present invention has a compressive strength of 4.0 N / mm ² or more when the material age, which is the number of days of the curing period after injection, is 1 day, or the material age is 7 days. In some cases, the compressive strength is 20 N/mm ² or more, or when the material age is 28 days, the compressive strength is 30 N/mm ² or more.

In the winter PC grout construction method of the present invention, the kneading work is carried out in an environment where the temperature is -1.0 to 10.0°C. The construction method includes a step of kneading the cement, the water, and the admixture using a mixer, wherein the rotation speed of the mixer is 1000 rpm or more, and the cement to be kneaded per time is After the step of having a mass of 25 to 100 kg and a kneading time of 3 minutes or more, and the step of kneading, the cement paste is added so that the flow down time by the JP funnel after 1 hour is 5 to 15 seconds. and a step of controlling the kneading temperature immediately after kneading to fall within the range of 9.0 to 18.0°C.

According to the present invention, in a general area where the average daily temperature is -6.0 ° C. or higher, the lowest temperature in the initial curing period from the first day to the seventh day is -12 ° C. and -8 ° C. or lower. As the application range is limited to environmental temperatures where the cumulative time of the day is 6 hours or less, it is possible to carry out construction of PC grout in cold weather, which is inexpensive and economical without taking measures for warming. In addition, the construction method of the present invention does not require the labor of construction, has the same workability as in other seasons, does not require troublesome temperature control during the curing period, and can be easily constructed in the cold without freezing. .
In addition, even though the water-cement ratio (W/C) is much lower than the normal (W/C = 45%), good fluidity can be maintained and practicality is improved without compromising workability. It is a PC grout for winter with.

FIG. 10 is a photograph showing the inside of a freezer including a test piece in a state in which an example of a winter PC grout test according to an embodiment of the present invention is being performed; FIG. 2 is a time chart of the temperature of the specimen shown in FIG. 1 and the temperature inside the freezer; 1. It is a photograph which shows the test body shown in FIG. 1 after demolding (before a compression test) and after a compression test.

Hereinafter, a winter PC grout material according to an embodiment of the present invention and a construction method using the winter PC grout material will be described.

In the winter PC grout material according to the embodiment of the present invention and the construction method using the winter PC grout material, warming measures are taken in winter in general areas (for example, warm areas, warm areas according to the climate classification of the Japan Meteorological Agency). The purpose is to obtain the desired strength without freezing when the PC grout is injected without freezing. On the other hand, application in a construction environment with a severe outside temperature (for example, -20°C like in Hokkaido) is intentionally excluded. For this reason, in the winter PC grout material of this embodiment, the environmental temperature at the time of initial curing is the most important factor in preventing the PC grout from freezing. By blending and combining well, it produces an antifreeze effect conveniently. Moreover, the anti-freezing effect can be obtained not only by mixing, but also by limiting the construction conditions. In this way, the winter PC grout material of the present embodiment emphasizes economic efficiency, and aims to enable PC grout construction without using heating means in winter in general districts.

In view of the above, the winter PC grout material according to the embodiment of the present invention is formed by kneading only cement, water, and an admixture.

As the above-mentioned cement, high-early-strength Portland cement is used. The early-strength Portland cement may satisfy, for example, the component composition specified in JIS R 5210. Also, the production site where cement is produced may be arbitrary.

The above-mentioned admixture is composed of a cement dispersant, a thickener and an antifoaming agent. As the admixture, for example, an admixture with a reduced amount of chloride ions is used in order to prevent corrosion of steel materials. As for the properties of the admixture, for example, before kneading with cement and water, it may be powdery, and after kneading, it is preferable that the viscosity is low and bleeding does not occur.

As the cement dispersant described above, one containing a polycarboxylic acid-based polymer as a main component is used. The main component may be, for example, modified polycarboxylate or the like, but is not limited to this. The cement dispersant is contained in an amount of 0.20 to 0.40 parts by mass with respect to 100 parts by mass of the above cement. More specifically, the content of the cement dispersant may be, for example, 0.20 parts by mass or 0.38 parts by mass with respect to 100 parts by mass of cement.

The thickening agent mentioned above may be, for example, methyl cellulose, etc., but is not limited thereto. The thickener is contained in an amount of 0.010 to 0.020 parts by mass with respect to 100 parts by mass of the above cement. More specifically, the content of the thickener may be, for example, 0.015 parts by mass or 0.17 parts by mass.

The antifoaming agent mentioned above may be, for example, a surfactant or the like, but is not limited thereto. The antifoaming agent is contained in an amount of 0.010 to 0.015 parts by mass with respect to 100 parts by mass of the above cement. More specifically, the content of the antifoaming agent may be, for example, 0.010 parts by mass with respect to 100 parts by mass of cement.

In the winter PC grout material of this embodiment, the water-cement ratio (W / C), which is the weight ratio of cement to water, is 29 to 32%, and the curing period is 28 days. In an environment where the minimum temperature on the 7th day from the beginning is -12 ° C and the cumulative time of the day is -8 ° C or less and the daily average temperature is -6.0 ° C or higher, the curing Even if no warming measures are taken during the period, the strength of the PC grout material for winter will exceed the desired strength.

In the winter PC grout material of the present embodiment, when the material age, which is the number of days of the curing period after injection, is 1 day, the compressive strength of the winter PC grout material is 4.0 N / as the desired strength. mm ² or more. When the material age is 7 days, the compressive strength is 20 N/mm ² or more as the desired strength. When the material age is 28 days, the compressive strength is 30 N/mm ² or more as the desired strength. For measuring the compressive strength, for example, a compression test method specified in JIS A 1107, 1108 may be used. The details of this feature will be described later in the section of [Example].

The construction method using the winter PC grout material according to the embodiment of the present invention is a construction method using the winter PC grout material configured as described above in an environment where the temperature is -1.0 to 10.0 ° C. is.
In other words, in general areas, assuming construction during the daytime in winter, the hydration reaction progresses and the inside of the duct (sheath) of the member before midnight when the environmental temperature drops to -10 ° C, which is the limit of strength expression. The heat of hydration generated in the PC grout is used to develop initial strength, and the temperature inside the duct (sheath) inside the member rises before the temperature drops to the extent that it affects the freezing of the PC grout. It is a construction method that assumes the scope of application.
The specific construction method includes two steps, firstly, a kneading step is performed, and then a kneading temperature control step is performed.

The kneading step is a step of kneading the cement, water, and admixture using a mixer. The rotation speed of the mixer during kneading is 1000 rpm or more. The mass of cement to be kneaded per time is 25-100 kg. The kneading time is 3 minutes or longer. As for the order of kneading, for example, after kneading water and an admixture for 30 seconds, cement may be added and further kneaded for 3 minutes or more.

The above-mentioned step of managing the kneading temperature is for the purpose of ensuring a usable time of at least one hour or more and preventing initial frost damage after the above-mentioned kneading step. This is a step of controlling the kneading temperature immediately after kneading so that it falls within the range of 9.0 to 18.0° C. so that the time for flowing down by the JP funnel is 5 to 15 seconds.
The step of managing in the present application is specifically performed as follows.
First, the kneading temperature is measured. When the kneading temperature is within a predetermined range, the kneaded winter PC grout material is injected.
If the kneading temperature deviates from the predetermined range as a result of the above confirmation, the material temperature and water temperature are adjusted, kneading is performed again, and the kneading temperature is measured. When it is confirmed that the kneading temperature is within a predetermined range, the re-kneaded winter PC grout material is injected.
In this manner, kneading for adjustment is performed until it is confirmed that the kneading temperature is within a predetermined range.
As shown in Table 1 of "Examples" described later, in the test, when kneading at a predetermined environmental temperature, the kneading temperature in each example was adjusted to fall within the range of 9.0 to 18.5 ° C. By doing so, it was demonstrated that the flowing down time by the JP funnel one hour after kneading was 4.8 to 12.5 seconds, and the pot life was 1 hour or more.
Therefore, as a construction method, the pot life of the PC grout after kneading should be secured for at least one hour or more by performing the management described above. However, in the present application, considering practicality, as a construction method, it is assumed that the running time by the JP funnel after 1 hour is 5 to 15 seconds as a condition that the pot life of 1 hour or more can be secured.
A fluidity test method specified in JSCE-F 531 is used to measure the flow-down time using the JP funnel.

As described above, according to the winter PC grout material according to the embodiment of the present invention, in a general area where the daily average temperature is -6.0 ° C or higher, the environmental temperature from the first day to the seventh day of initial curing And by limiting the construction conditions, it is possible to construct PC grout in the cold, which is economical and inexpensive without taking measures to heat it. In addition, the construction method of PC grout material for winter according to the embodiment of the present invention does not require construction labor, has the same workability as other seasons, does not require troublesome temperature control during the curing period, and does not freeze. It is a method that can be easily applied in the cold without any need.

[Example]
In order to obtain the data necessary for confirming the performance of the winter grout material for PC according to the embodiment of the present invention and setting the usage conditions, tests corresponding to each example were conducted. Table 1 shows a list of test results for each example. There are 14 examples in total, and A0, A1, A2, A3, A4, A6, A7, B0, B1, B2, B3, B4, B6, and B7 are assigned as compound codes listed in Table 1. ing. Hereinafter, each example will be referred to as Examples A0, A1, A2, A3, A4, A6, A7, B0, B1, B2, B3, B4, B6, and B7, respectively, so as to correspond to the compound symbols.

<Admixture>
Different admixtures were used for the notations "A" and "B" of the compounding symbols. In Examples A0, A1, A2, A3, A4, A6 and A7, a polycarboxylic acid-based dispersant manufactured by Company N, a cellulose-based thickener, and an antifoaming agent were blended as admixtures. The contents of the dispersant, thickener, and antifoaming agent were set to 0.20 parts by mass, 0.015 parts by mass, and 0.010 parts by mass, respectively, with respect to 100 parts by mass of cement. In Examples B0, B1, B2, B3, B4, B6, and B7, as admixtures, a polycarboxylic acid-based dispersant manufactured by Company L was blended with a cellulose-based thickener and an antifoaming agent. The contents of the dispersant, thickener, and antifoaming agent were set to 0.38 parts by mass, 0.017 parts by mass, and 0.010 parts by mass, respectively, with respect to 100 parts by mass of cement.

<Cement>
In each example, high-early-strength Portland cement manufactured by T Company was used as the cement. In Examples A0, A1, A2, A3, A4, B0, B1, B2, B3, and B4, the same manufacturer's product made in Mie Prefecture was used, and in Examples A6, A7, B6, and B7, the same manufacturer's product made in Hokkaido was used. I used the one from The purpose of using different production sites was to understand the effects of quality variations in the same cement manufacturer on the test results. In Table 1, the water-cement ratio is the value obtained by dividing the mass of water by the mass of cement. Examples A2 and B2 had a water-cement ratio of 0.29, Examples A3 and B3 had a water-cement ratio of 0.32, and all other examples had a water-cement ratio of 0.3. That is, the water-cement ratio was set within the range of 29 to 32%.

<JP funnel flow down time>
After kneading the raw materials of each example and measuring the kneading temperature, the JP funnel flow-down time was measured. The temperature in each step was in the range of -1.0 to 10.0°C. The above cement, water and admixture were kneaded using a mixer at 1000 rpm for 3 minutes or more. The temperature of the winter PC grout material when the mixer was stopped and the kneading was completed was measured as the kneading temperature.

As shown in Table 1, in Example B4, the kneading temperature was 9.0° C., which was the lowest temperature among all the examples. On the other hand, in Example B6, the kneading temperature was 18.5° C., which was the highest temperature among all the examples. That is, the kneading temperature in each example was adjusted to be in the range of 9.0 to 18.5°C.

One hour after the mixer was stopped and kneading was completed, the JP funnel flow time of the PC grout material for winter was measured. Specifically, in a state in which the lower end opening of the JP funnel was set on a tripod and the inner wall was wetted, the winter PC grout material was poured in from the upper end opening of the JP funnel after one hour had passed. . Next, after completing the filling up to the upper surface of the JP funnel, the lower end opening was opened to start the outflow of the PC grout material for winter, and at the same time, time measurement was started. Then, the time until the outflowing grout flow was interrupted was measured as the JP funnel flow down time.

As shown in Table 1, in Example B3, the JP funnel flow-down time was 4.8 seconds, which was the shortest time among all the examples. On the other hand, in Example A0, the JP funnel flow down time was 12.5 seconds, which was the longest time in all the examples. That is, the JP funnel flow down time in each example varied within the range of 4.8 to 12.5 seconds.

This range of JP funnel run-down times indicates a viscosity level commonly referred to as low viscosity. Therefore, by adjusting the water-cement ratio to 0.29 to 0.32 (29 to 32%) and the grout kneading temperature to 9.0 to 18.0 ° C, the grout injection work can be performed one hour after kneading. It was confirmed that it can be carried out in a low-viscosity state as long as it is within the range.

<Compressive strength>
In each example, the grout obtained through the kneading described above was shaped as a test piece, and the test piece was cured. As for the shape of each specimen, a cylinder of φ50×100 mm was formed. In order to reproduce the winter environment of a general area, the specimen was cured in a freezer.

As shown in FIG. 1, each columnar specimen was allowed to stand in a freezer for curing. No separate warming measures were taken during curing. FIG. 2 shows a time chart of the temperature of the specimen and the temperature in the freezer as a representative example of each example shown in Table 1. As shown in FIG. The time charts of the temperature of the specimen shown in FIG. 2 are those of Examples A6, A7, B6 and B7 as examples. A time chart was obtained by measuring the central portion of the specimen with a thermocouple and recording it at each predetermined timing. The temperature in the freezer ranged from -1.2 to -11.6°C, with an average of -6.0°C. However, in each example shown in Table 1, the lowest temperature in the freezer measured at the time of the test was different because the time of the test was different, and the lowest temperature measured among them was -13.9 ° C. There is something

After starting curing, the compressive strength was measured for test specimens of different material ages. The curing period was set to 28 days, and in Examples A0 and B0, the compressive strength of the specimen was measured at each time point of 7 days and 28 days of material age. In Examples A1, A2, A3, A4, B1, B2, B3, and B4, the compressive strength of the specimen was measured at each time point of 1 and 7 days of material age. In Examples A6, A7, B6 and B7, the compressive strength of the specimen was measured at each time point of 1, 7 and 28 days of material age.

In the compressive strength test, the compressive strength of three specimens was measured, and Table 1 shows the average value of these as the value of the compressive strength. As examples, measured values and average values in Examples A6, A7, B6 and B7 are shown below.

・Example A6
· Compressive strength on the first day of material age Measured value of the first test piece: 6.1 MPa (N / mm ² )
Measured value of the second test piece: 4.8 MPa (N/mm ² )
Measured value of the third test piece: 5.6 MPa (N/mm ² )
Average of measured values: 5.5 MPa (N/mm ² )
· Compressive strength on the 7th day of material age Measured value of the first test piece: 30.0 MPa (N / mm ² )
Measured value of the second test piece: 29.0 MPa (N/mm ² )
Measured value of the third test piece: 26.4 MPa (N/mm ² )
Average of measured values: 28.5 MPa (N/mm ² )

・Example A7
· Compressive strength on the first day of material age Measured value of the first test piece: 6.3 MPa (N / mm ² )
Measured value of the second test piece: 6.3 MPa (N/mm ² )
Measured value of the third test piece: 6.1 MPa (N/mm ² )
Average of measured values: 6.2 MPa (N/mm ² )
· Compressive strength on the 7th day of material age Measured value of the first test piece: 28.0 MPa (N / mm ² )
Measured value of the second test piece: 26.7 MPa (N/mm ² )
Measured value of the third test piece: 21.9 MPa (N/mm ² )
Average of measured values: 25.5 MPa (N/mm ² )

・Example B6
· Compressive strength on the first day of material age Measured value of the first test piece: 5.3 MPa (N / mm ² )
Measured value of the second test piece: 4.8 MPa (N/mm ² )
Measured value of the third test piece: 4.8 MPa (N/mm ² )
Average of measured values: 5.0 MPa (N/mm ² )
· Compressive strength on the 7th day of material age Measured value of the first test piece: 15.5 MPa (N / mm ² )
Measured value of the second test piece: 26.7 MPa (N/mm ² )
Measured value of the third test piece: 26.7 MPa (N/mm ² )
Average of measured values: 23.0 MPa (N/mm ² )

・Example B7
· Compressive strength on the first day of material age Measured value of the first test piece: 5.8 MPa (N / mm ² )
Measured value of the second test piece: 5.0 MPa (N/mm ² )
Measured value of the third test piece: 6.1 MPa (N/mm ² )
Average of measured values: 5.6 MPa (N/mm ² )
· Compressive strength on the 7th day of material age Measured value of the first test piece: 37.1 MPa (N / mm ² )
Measured value of the second test piece: 24.2 MPa (N/mm ² )
Measured value of the third test piece: 27.5 MPa (N/mm ² )
Average of measured values: 29.6 MPa (N/mm ² )

As shown in Table 1, at 1 day old, Example B6 had a compressive strength of 5.0 MPa (N/mm ² ), which was the lowest value among all the examples measured. On the other hand, in Example A1, the compressive strength was 8.0 MPa (N/mm ² ), which was the maximum value among all the measured examples. In other words, the measured compressive strength in each example varied within the range of 5.0 to 8.0 MPa (N/mm ² ) after one day of age. The average curing temperature (that is, the temperature in the freezer) in each example measured on the first day of the material age varied within the range of -6.7 to -6.2°C.

At 7 days old, Example B6 had a compressive strength of 23.0 MPa (N/mm ² ), which was the lowest value among all the examples measured. On the other hand, in Example B2, the compressive strength was 55.3 MPa (N/mm ² ), which was the maximum value among all the measured examples. That is, at 7 days old, the measured compressive strength in each example varied within the range of 23.0 to 55.3 MPa (N/mm ² ). At 7 days old, the average curing temperature (that is, the temperature in the freezer) of each example measured varied within the range of -6.5 to -5.7°C.

At a material age of 28 days, in Example B6, the compressive strength was 39.7 MPa (N/mm ² ), which was the lowest value among all the measured examples. On the other hand, in Example A0, the compressive strength was 52.6 MPa (N/mm ² ), which was the maximum value among all the measured examples. That is, at the age of 28 days, the measured compressive strength in each example varied within the range of 39.7 to 52.6 MPa (N/mm ² ). At the age of 28 days, the average curing temperature (that is, the temperature in the freezer) of each example measured varied within the range of -6.4 to -6.2°C.

Therefore, by adjusting the water-cement ratio to 0.29 to 0.32 (29 to 32%) and the kneading temperature of the grout to 9.0 to 18.0 ° C, the average curing temperature is -6.0 ° C. Under the above environment, it was confirmed that a compressive strength of 4.0 MPa (N/mm ² ) or more can be obtained in one day of age without taking measures for warming. After that, even under the same environment, an increase in strength was observed, and a compressive strength of 20.0 MPa (N/mm ² ) or more was obtained at 7 days of age, and 30.0 MPa (N/mm 2 ), which is the standard strength at 28 days of age. mm ² ) or more can be obtained.

In addition, although the admixture was changed for each of the compound symbols "A" and "B", no difference in performance was observed even if the products of the polycarboxylic acid-based dispersant constituting the admixture were different. . Moreover, no difference in performance was observed even if the cement manufacturing sites were different.

The effect will be considered with reference to the time chart of FIG. 2 again. After about 2 hours from immediately after placement (that is, the start of curing), the temperature of all specimens dropped below zero. Thereafter, the temperature of each specimen was maintained within the range of -1 to -2°C for 6 to 7 hours. This phenomenon is considered to be caused by the heat generated by the hydration reaction. The reason why the winter PC grout of the example does not freeze and the initial strength development is not inhibited is considered to be due to the above phenomenon. After about 24 hours (that is, 1 day old), the grout internal temperature is about -6 ° C, which is equivalent to the average curing temperature, but the compressive strength at this time is about 5 MPa as measured above. , it can be understood that the intensity expression proceeded without being inhibited. The lowest temperature measured at this time was −11.6° C., and the cumulative time of the day when −8° C. or less was reached was 6.3 hours. FIG. 3 shows, as an example, the state of the specimen of Example A4 after removal from the mold and after the compression test at a material age of 1 day. FIG. 3(a) shows the specimen after demolding and before the compression test, and FIG. 3(b) shows the specimen after the compression test. These observations showed no evidence of freezing, either externally or internally. This also confirmed that the winter PC grout of the example did not freeze.

As for the water-cement ratio (W/C), it is preferable to make it small in terms of anti-freezing.
In the present invention, although the water-cement ratio (W/C) is significantly reduced from the normal (W/C = 45%), the pot life of the kneaded PC grout material is 1 hour. By checking the flow time with the funnel, good fluidity can be maintained without impairing workability. Also, using the polyethylene bag method presented in JSCE-F532-2013, it was confirmed that there was no material separation and no bleeding occurred.

Although the present invention has been described above in more detail and specifically by showing the embodiments, the embodiments are merely illustrative descriptions and do not limit the present invention.

Claims (2)

Only cement, water and admixture,
A cement paste used as a PC grout material for winter,
The cement is high-early-strength Portland cement,
The admixture consists only of a cement dispersant containing a polycarboxylic acid-based polymer as a main component, a thickener, and an antifoaming agent,
The cement dispersant is contained in an amount of 0.20 to 0.40 parts by mass with respect to 100 parts by mass of the cement,
The thickener is contained in an amount of 0.015 to 0.020 parts by mass with respect to 100 parts by mass of the cement,
The antifoaming agent is contained in an amount of 0.010 to 0.015 parts by mass with respect to 100 parts by mass of the cement,
The water-cement ratio of the water and cement is 29 to 32%,
When the curing period is 28 days after the injection work of the PC grout material for winter is performed, the minimum temperature from the 1st day to the 7th day is -12 ° C. or higher and -8 ° C. or lower. In an environment where the cumulative time is 6 hours or less and the average daily temperature is -6.0 ° C or higher, the strength of the cement paste applied in the cold without taking warming measures during the curing period is as follows ( 1) A cement paste characterized by being one or more of (3).
(1) When the material age is 1 day, the compressive strength is 4.0 N / mm ²
(2) When the material age is 7 days, the compressive strength is 20 N / mm ²
(3) When the material age is 28 days, the compressive strength is 30 N / mm ² A winter PC grout construction method using the cement paste according to claim 1, wherein the kneading work is performed in an environment where the temperature is -1.0 to 10.0 ° C.
A step of kneading the cement, the water, and the admixture using a mixer, wherein the rotation speed of the mixer is 1000 rpm or more, and the mass of the cement to be kneaded per time is 25 to 100 kg. and the kneading time is 3 minutes or more;
After the kneading step, the cement paste is kneaded immediately after kneading so that the flow time by the JP funnel after 1 hour is 5 to 15 seconds. a step of managing to fit into
A winter PC grout construction method comprising:

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