JP3271492B2 - High strength concrete - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength concrete, and more particularly to a concrete composition for further increasing the strength of this type of concrete.

[0002]

2. Description of the Related Art In many cases, reinforced concrete underground continuous walls are used not only as temporary retaining walls when constructing an underground structure but also as a part of a main body. This type of underground continuous wall is specifically a retaining wall of a large underground structure (for example, an LNG underground storage tank),
It is used for starting or reaching shafts in shield tunnels, and is also used as a foundation for underground dams and high-rise buildings, for example.

In recent years, underground structures of this type have been increased in size and depth, and concrete strength for underground continuous walls employed in such underground structures has been increased, for example, by design. A standard strength of about 600 to 700 kgf / cm ² is required. On the other hand, this kind of underground continuous wall is also required to function as a water impervious wall, and it is also an important required performance that the concrete be hardened after the hardening of the concrete.

[0004] In order to meet such demands for higher strength and water-shielding, low heat-generating cements such as a mascon type blast furnace Class B cement and ternary ultra-low heat have been used from the viewpoint of suppressing temperature cracking. A method of using cement and using a fluidizing agent and the like in combination to reduce the unit water amount and the cement amount as much as possible has been adopted. However, such a conventional high-strength concrete has a technical problem described below in order to further increase the strength.

[0005]

That is, if the strength of concrete is further increased, for example, the thickness of the continuous underground wall can be reduced, so that the amount of excavated soil can be reduced and the cost can be reduced. As the strength increases, the water-cement ratio decreases in accordance with the progress, and the viscosity of the concrete increases. When the viscosity of concrete increases, the workability and the filling property of the concrete decrease, and some cases of poor filling have been reported.

[0006] Such deterioration of workability and filling property is a great hindrance to further increase the strength of concrete and to achieve higher strength, for example, 800 kgf / cm ² or more in design standard strength. Had become. Further, when the water-cement ratio is greatly reduced, even if low-heat-generating cement is used, the amount of cement increases, so that there is a problem that the temperature change during the hardening process of the concrete increases, and cracks are easily generated.

The present invention has been made in view of such conventional problems, and an object of the present invention is to further increase the strength while avoiding deterioration in workability and fillability. It is to provide a high strength concrete that can be achieved. Another object of the present invention is to provide high-strength concrete capable of suppressing temperature cracking even when the water-cement ratio is reduced.

[0008]

In order to achieve the above-mentioned object, the present invention comprises a cement, an aggregate and a high-performance AE water reducing agent ,
Tremie into the excavated hole in the ground while filling with liquid
In high-strength concrete poured via a pipe, the high-performance AE water reducing agent is mainly composed of a polycarboxylate-based polymer compound, and the cement has a belite component of 45%.
A percent of high belite cement, the water-cement ratio was 30% or less at 20% or more, the flow time of the concrete charged into the O funnel having a hollow cylindrical funnel portion closing gate is provided, hitting 10-3 just before installation
Set the time to within 0 seconds, and set the
The high temperature rise was set to 65 ° C. or less . When the water-cement ratio is 20% or less, the strength of the concrete increases, but the fluidity is remarkably reduced, and the workability and the filling property are deteriorated. Further, if the water cement ratio exceeds 30%, it is not possible to increase the strength of the concrete, so it is necessary to maintain the water cement ratio at 30% or less. Further, when the water-cement ratio is maintained within the above range, the maximum temperature rise of concrete can be suppressed to 45 ° C. or less. In this case, a high belite cement having a C ₂ S (belite component) of 45% or more is used. In the high-strength concrete of the present invention, a high-performance concrete containing a polycarboxylate-based polymer compound as a main component
Use E water reducer. When such a high performance AE water reducing agent is used, the synergistic effect with high belite cement
Further strengthening can be achieved while avoiding deterioration of workability and filling property. High strength concrete of the present invention, pre-workability by O funnel test, it is possible to evaluate the filling factor, O funnel flow time, is set to be in the range of 10 to 30 seconds before hitting設直 , in the design strength 800 k
gf / cm ² or more and a concrete suitable for the actual construction is obtained. The high strength concrete of the present invention, it is pouring through a tremie pipe to stable liquid filled while drilled groove holes in the ground to. When the underground continuous wall is constructed by such a method, the excavated soil amount can be reduced by reducing the wall thickness.

[0009]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows a specific application example of the high-strength concrete according to the present invention. In the figure, the high-strength concrete of the present invention is applied to a method of constructing an underground continuous wall. In the underground diaphragm wall method, a rectangular excavation hole 10 is excavated and formed to a predetermined depth while being filled with a stable liquid. Is replaced with concrete, a rectangular panel 14 is formed.

The replacement between the concrete and the stabilizing liquid is performed by using a hollow cylindrical tremy tube 16. in this case,
The concrete is supplied by freely falling in the tremy tube 16, and the supplied concrete is sequentially discharged from the bottom of the drilled hole 10 from the tip of the tremy tube 16. As the top of the concrete poured into the borehole 10 rises, the tremee pipe 16 is gradually raised.

At this time, the rising speed is controlled so that the tip of the tremie tube 16 is always located in the discharged concrete. When the cast concrete is cured and one panel 14 is formed, the excavation hole 10 is formed in the lateral direction, and the above-described steps are sequentially repeated so that the rectangular panel 14 is moved in the lateral direction. A connected underground wall is constructed.

In the continuous underground wall construction method shown in FIG. 1, the high-strength concrete of the present invention was used, and various characteristics of the high-strength concrete were measured. The plane shape of the panel 14 actually constructed in the ground is, as shown in detail dimensions in FIG. 1, length × width = 0.9 m × 2.4 m, and the depth is 33
m. Reinforcing cage 12 is vertical x horizontal = 0.67m x
In order to measure the temperature and pressure of the cast high-strength concrete at 2.14 m, a thermocouple was previously attached to a predetermined position of the reinforcing rod cage 12. In FIG. 1, a thermocouple for measuring the temperature in the section of the high-strength concrete cast at the position indicated by ● was installed.

Concrete, cement, aggregate and high performance
A high-strength concrete containing an AE water reducing agent was used. This
If the cement is high belite cement (low heat
Rutland cement, made by Chichibu Onoda Co., Ltd., specific gravity 3.
22, specific surface area 3440cm ^Two, C_TwoS54%) used
did. Aggregate is crushed stone from Kasama 2005 (compared to coarse aggregate).
2.65 weight, water absorption 0.70%, coarse grain ratio 6.58, actual
Rate of 60.0%) and coarse sand from Kashima as fine aggregate
(Specific gravity 2.61, water absorption 0.77%, coarse particle ratio 2.80,
The actual rate was 65.8%).

As the high-performance AE water reducing agent, one containing a polycarboxylic acid salt-based polymer compound as a main component was used. The mixing ratio of the high-strength concrete was set as shown in Table 1 below. The high-strength concrete has a water-cement ratio of 30% (first embodiment) and a water-cement ratio of 22% (second embodiment).
Example) were prepared.

[0015]

[Table 1] 2 and 3 show the results of the property test of the fresh concrete according to the first and second embodiments of the present invention. FIG. 2 shows the properties of the high-strength concrete according to the first embodiment of the present invention, and FIG. 3 shows the properties of the high-strength concrete according to the second embodiment. In the figure, the state immediately after the production, in which high-strength concrete was blended, and the state immediately before the concrete were transported to the casting site by an agitator wheel were measured.

In this result, a point to be particularly noted is:
It is the funnel falling time. The funnel flow time was measured using an O funnel 20 as shown in FIG. The O funnel 20 shown in the figure has a hollow frustoconical funnel 20a, a hollow cylindrical part 20b connected to the lower end of the funnel 20a.
And an opening / closing gate 20c for opening and closing the lower end of the cylindrical portion 20b.

When measuring the falling time of the high-strength concrete, the O funnel 20 is supported horizontally and the volume is 10 l.
Is slowly poured into the funnel 20. Then, after leveling the high-strength concrete in the O funnel 20, the opening / closing gate 20c is opened and at the same time the measurement is started with a stopwatch, and the time for the sample to flow down is read to the unit of 0.1 second.

By previously measuring the funnel flowing time of the fresh concrete in this way, the workability and the filling property at the time of placing high-strength concrete can be evaluated in advance, and it is clear from the test results described later. Oro
If the heat flow time is 10 seconds or more immediately before casting (Example 1) , the compressive strength is 800 without lowering the workability.
Concrete of kgf / cm ² or more can be obtained.

Also, the falling time of the O funnel is 30 minutes before the casting.
If the time exceeds the second (second embodiment) , the workability may be remarkably deteriorated. Therefore, it is necessary to set the value within this range. FIG. 5 shows the results of the setting test of the high-strength concrete of the first and second examples. As shown in the figure, in the high-strength concretes of Examples 1 and 2, the setting of the cement starts after about 8 hours, and after about 14 hours, considerable strength is developed. It can be seen that the setting time of concrete is not so different from that of ordinary concrete.

On the other hand, in the case of conventional high-strength concrete (mass-con-type blast furnace type B cement or ternary ultra-low heat cement), the setting time is very slow, and it takes a very long time to develop strength. I was When there is such a difference in the setting time, in particular, when concrete is poured into the excavation hole 10, it takes time to stabilize the hole wall in the conventional high-strength concrete, but in the high-strength concrete of the present invention, This has the advantage that the hole wall can be stabilized at an early stage.

FIG. 6 shows details of the arrangement of the thermocouple for measuring the temperature distribution in the cross section shown in FIG. As shown in the figure, the thermocouples for measuring the temperature distribution in the cross section are TA-1 to T-1.
Six A-6 were arranged at the positions of the dimensions shown. FIG. 7 shows a measurement result of a temperature change by each thermocouple of the high-strength concrete of Example 1, and FIG. 8 shows a measurement result of a temperature change by each thermocouple of the high-strength concrete of Example 2. I have.

[0022] As apparent from the results of these temperature measurements, the high strength concrete of Examples 1 and 2, even if the water-cement ratio is small Example 2, the highest temperature is 65
℃ or less, and despite the small water-cement ratio,
It was confirmed that the temperature rise was very small. Accordingly, the probability of occurrence of cracks generated during the hardening process of the cast high-strength concrete is extremely reduced, and the water barrier of the underground continuous wall can be sufficiently ensured.

FIG. 9 shows that the high-strength concretes of the first and second embodiments are collected at a manufacturing plant and a casting site, respectively, and cured under standard curing conditions (in water at 20 ± 3 ° C.). The measurement result of the compressive strength is shown. As is clear from the results shown in the figure, the compressive strength of the high-strength concrete of Example 1 was about 900 kgf after 91 days of age.
/ Cm ^2, and in the case of Example 2, the material age 91
After days, the compressive strength exceeds about 1100 kgf / cm ² .

In the same figure, the measurement results for each agitator vehicle are very close to each other, and it can be seen that the high-strength concrete of this embodiment can obtain homogeneous high-strength concrete with little variation in compressive strength. . FIG. 10 shows that the high-strength concrete of Examples 1 and 2 was cast and the panel 1
4 shows the sampling position when a core specimen was collected by actually forming the core 14 of the obtained panel 14 and performing core boring in the vertical direction. The inner diameter of core boring is 10
The measurement was performed at two locations in the vertical direction with 0 mm.

FIG. 11 shows the test results of the core strength in the longitudinal direction when the high-strength concrete of the first embodiment was used. FIG. 12 shows the results of the test using the high-strength concrete of the second embodiment. Test results of core strength in the direction are shown. In these figures, what is indicated by AV-1 and AV-2 is
These correspond to the positions indicated by the same reference numerals in FIG.
FIG. 13 shows the distribution of the measured values of the compressive strength in the longitudinal core test. FIG. 13 (A) shows the high-strength concrete of Example 1, and FIG. 13 (B) shows the high-strength concrete of Example 2. It is high-strength concrete. As is clear from the test results shown in FIGS. 11 to 13, in the high-strength concrete of the present example, it is found that there is very little variation even in the depth direction, and uniform high-strength concrete can be obtained.

From the measurement of the compressive strength of the standard cured specimen and the core specimen, the strengths shown in Table 2 below are guaranteed in the high-strength concretes of Examples 1 and 2.

[0027]

[Table 2] From this, the high-strength concrete of the present example can achieve a design reference strength of 800 kgf / cm ² or more, and in particular, in the case of Example 2, the design reference strength is 1 kgf / cm ^2.
000 kgf / cm ² or more can be obtained, and when achieving such high strength, the workability is not deteriorated.
In addition, cracks can be suppressed.

When the high-strength concrete of the present embodiment is applied to the construction of an underground continuous wall, it can be cast without any trouble even with a tremy tube 16 having a relatively small diameter, and a high-strength concrete can be obtained. The wall thickness of the excavation hole 10 can be made thinner than before, so that the amount of excavated soil can be reduced and the cost can be reduced .

[0029]

As described above in detail in the embodiments,
ADVANTAGE OF THE INVENTION According to the high-strength concrete which concerns on this invention, a temperature-crack is hard to generate | occur | produce, it is excellent in water-shielding, and it is highly homogeneous and high-strength. Further, according to the present invention, it is possible to determine in advance whether the workability is good or not by the O-funnel test, and it is possible to confirm the quality judgment of the high-strength concrete before placing .

[Brief description of the drawings]

FIG. 1 is a plan view and a longitudinal sectional view of a construction state when the high-strength concrete according to the present invention is applied to the construction of an underground continuous wall.

Is a graph showing the properties of the fresh state of an embodiment of a high-strength concrete that written in the present invention; FIG.

3 is a graph showing the properties of the fresh state of another embodiment of a high-strength concrete that written to the present invention.

FIG. 4 is a perspective view of an O funnel for measuring a flowing time of the high-strength concrete according to the present invention.

FIG. 5 is a graph showing the measurement results of the setting test of the high-strength concrete of the first and second embodiments of the present invention.

FIG. 6 is a detailed layout diagram of the thermocouple for temperature measurement shown in FIG. 1;

FIG. 7 is a graph showing temperature measurement results of the high-strength concrete of the first example.

FIG. 8 is a graph showing temperature measurement results of the high-strength concrete of the second embodiment.

FIG. 9 is a graph showing the measurement results of the compressive strength of the high-strength concrete of the first and second examples in the standard curing.

FIG. 10 is a plan view and a vertical cross-sectional view of a position where a core specimen is collected when a panel is formed using the high-strength concrete of the first and second embodiments.

FIG. 11 is a graph showing measurement results of a core strength test when the high-strength concrete of the first example is used.

FIG. 12 is a graph showing measurement results of a core strength test when the high-strength concrete of the second embodiment is used.

FIG. 13 is a graph showing a distribution of compressive strength of the first and second embodiments.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI (C04B 28/04 (C04B 28/04 24:22) 24:22) E 103: 30 103: 30 111: 00 111: 00 C09K 103: 00 C09K 103: 00 (72) Inventor Hideki Kawamura 2-3 Kanda Tsukamachi, Chiyoda-ku, Tokyo Obayashi Corporation Tokyo Head Office (56) References JP-A-7-76825 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) C04B 28/02-28/04

Claims (1)

(57) [Claims] 1. A cement, an aggregate and a high-performance AE water reducing agent.
In a slot excavated in the ground while containing and stabilizing liquid
The high-performance AE water reducing agent is mainly composed of a polycarboxylate-based polymer compound, and the cement has a belite component of 45% or more.
A high belite cement, the water-cement ratio of 20%
To 30% or more, the flow time of the concrete charged into the O funnel having a hollow cylindrical funnel portion closing gate is provided, pouring
Set to be in the range of 10 to 30 seconds just before and cure
High strength concrete characterized in that the maximum temperature rise during the process is 65 ° C. or less .