JPH08100528A - Placing method for mass concrete - Google Patents

Abstract

PURPOSE: To minimize the addition rate of a hydration heat-decreasing agent and prevent cracking. CONSTITUTION: The whole placing area D of mass concrete is divided into the first area of concrete 1 without hydration heat-decreasing agent and the second area of concrete 2 with hydration heat-decreasing agent. The placing area L of the second concrete 2 is divided into n areas 11 , 12 ,..., 1n and the initial value of the addition rate in respective layers of the second concrete 2 is a1 , a2 ,...an . The addition rate of the hydration heat-decreasing agent of respective layers of the second concrete 2 is increased gradually by every a from the initial value to the upper limit value Amax and the placing area is increased gradually at every addition rate from the initial value to the whole placing area D to get the addition area of the second concrete 2 at the time when the tensile stress of concrete in respective positions, calculated from a temperature-stress analysis is less than the tensile strength of concrete and the addition rate of the hydration heat-decreasing agent becomes minimum.

Description

Detailed Description of the Invention

[0001]

This invention relates to mass concrete
The present invention relates to a method for placing mass concrete, which prevents cracking that occurs in concrete due to heat of hydration of concrete after placing (concrete having a large casting thickness).

[0002]

2. Description of the Related Art When pouring mass concrete, heat of hydration is generated when the concrete is set and hardened by a hydration reaction between cement and water. This heat of hydration generally reaches the maximum temperature 2 to 5 days after the concrete is poured, and the hydration reaction continues after that, and the strength also increases with the hydration reaction. At this time, the maximum temperature of the mass concrete may rise to about 80 ° C. when the ambient temperature is 10 ° C. to 30 ° C.

FIG. 5 shows a concrete 5 containing no hydration heat reducing agent that suppresses the heat generation rate of hydration placed in a mold 52.
6 shows the temperature change of the inner layer at the position of height L ₁ from the bottom surface of the concrete 51 and the temperature change of the outer layer at the position of height L ₂ from the bottom surface of the concrete 51. Above concrete 5
The heat of hydration of the outer layer of 1 is radiated to the outside, but the heat of hydration of the inner layer has a large casting thickness, so it is difficult to radiate to the outside, and the temperature of the inner layer of the concrete 51 becomes higher than that of the outer layer of the concrete 51. There is a temperature difference between the inner and outer layers.

That is, the outer layer of the concrete 51 at the age t ₀ after casting reaches the maximum temperature T ₅ and then shrinks while lowering the temperature, while the inner layer of the concrete 51 has an age t ₁ Expands as the temperature continues to rise to the maximum temperature T ₁ . That is, since the outer layer of the concrete 51 is likely to radiate heat to the outside, the maximum temperature of the outer layer is as low as T ₅ with respect to the maximum temperature T ₁ of the inner layer of the concrete 51, and the temperature difference is ΔT ₃ . Further, as shown in FIG. 7, the Young's modulus of the inner layer and the outer layer of the concrete 51 rises to E ₁ from the casting to the age t ₁ and becomes a solidified state. Therefore, tensile stress and compressive stress act on the inner and outer layers of the concrete 51 depending on the temperature difference between them. That is, the inner layer concrete having a high temperature is subjected to compressive stress by the outer layer concrete having a low temperature, while the outer layer concrete is subjected to a tensile stress by the inner layer concrete. The tensile stress acting on the outer layer of the concrete 51 becomes the largest when the temperature difference between the inner layer and the outer layer of the concrete 51 has the maximum value ΔT ₄ (= T ₁ −T ₆ ) at the age t ₁ , and the cracking is large. It is in a state where it easily occurs. When the tensile stress generated in the outer layer of the concrete 51 exceeds the tensile strength of the concrete 51, a crack is generated in the outer layer of the concrete 51.

Therefore, as a method for placing mass concrete, there is a method in which a hydration heat reducing agent is mixed into the whole mass concrete so as to delay the rise of hydration heat and reduce the temperature rise of the mass concrete (Japanese Patent Laid-Open No. SHO 61-96). 63-11794
No. 1). In this mass concrete, the hydration heat is gentle and the heat is easily radiated to the outside, so that the temperature of the whole mass concrete becomes low and the temperature difference between the outer layer and the inner layer becomes small. Therefore, the tensile stress acting on the outer layer of the concrete 51 due to the temperature difference between the inner layer and the outer layer is reduced, so that cracking can be prevented. This method of placing a mass concrete not only prevents cracks due to internal restraint stress, but also prevents external restraint stress, that is, cracks at joints of old and new concrete.

[0006]

However, in the concrete to which the above-mentioned hydration heat reducing agent is added, breathing water increases, and water bubbles accumulate around the aggregates and the reinforcing bars, and the voids caused by the water bubbles cause the strength of the concrete to rise. As well as
There is a problem that the quality of the concrete deteriorates because the adhesive force to the reinforcing bar is weakened.

Therefore, an object of the present invention is to provide a method for placing mass concrete in which the rate of addition of the heat of hydration reducing agent is minimized to prevent cracking.

[0008]

In order to achieve the above object, the method for placing mass concrete according to claim 1 is such that the entire placing area is the placing area of the first concrete in which the hydration heat reducing agent is not added. A method of placing mass concrete in which the second concrete is mixed with a hydration heat reducing agent added and mixed into the placing area, and the tensile stress of concrete at each position calculated by temperature stress analysis is The tensile strength of the second concrete and the addition rate of the hydration heat reducing agent are adjusted so as to be less than or equal to the tensile strength of the second concrete. And a step of determining a casting area of the concrete, and placing the second concrete having the minimum addition rate of the hydration heat reducing agent in the casting area when the addition rate of the hydration heat reducing agent is minimum. In addition to setting Is characterized in that the the punching region where the other than the above droplet formation regions concrete and a step of pouring the first concrete.

Further, in the mass concrete pouring method according to the second aspect, the pouring area of the first concrete without addition of the hydration heat reducing agent and the hydration heat reducing agent are added and mixed in all the pouring areas. A method for placing mass concrete in which the second concrete is placed in the placement area, wherein the tensile stress of concrete at each position calculated by temperature stress analysis is equal to or less than the tensile strength of concrete. 2. The step of determining the second concrete pouring area when the addition rate of the hydration heat reducing agent is minimized by adjusting the concrete pouring area and the addition rate of the hydration heat reducing agent; When the tensile stress of the concrete at a certain position calculated by the above temperature stress analysis does not become equal to or lower than the tensile strength of the concrete even if the pouring area of the second concrete and the addition rate of the hydration heat reducing agent are adjusted, Serial to reduce the total droplet region where, as concrete tensile stress of the positions calculated by the temperature stress analysis is below the tensile strength of concrete, the second
By adjusting the addition area of the hydration heat reducing agent and the addition area of the hydration heat reducing agent of the second concrete, and setting the addition area of the second concrete when the addition rate of the hydration heat reducing agent of the second concrete is minimum. The step of determining and placing the second concrete having the minimum addition rate of the hydration heat reducing agent in the casting area when the addition rate of the hydration heat reducing agent is minimum, And the step of placing the first concrete in a casting area other than the casting area of the second concrete.

Further, in the mass concrete pouring method according to the third aspect, the pouring area of the first concrete without addition of the hydration heat reducing agent and the hydration heat reducing agent are added and mixed in all the pouring areas. A method for placing mass concrete in which the second concrete is placed separately in the placing area, wherein the initial value of the addition rate of the hydration heat reducing agent of the second concrete and the initial value of the placing area are set. And the addition rate of the hydration heat reducing agent of the second concrete is gradually increased from the initial value of the addition rate, and the casting area of the second concrete is placed for each addition rate. While gradually increasing from the initial value of the region, set the adiabatic temperature rise formula based on each addition rate of the hydration exothermic reducing agent, the tensile stress of concrete at each position by temperature stress analysis based on the adiabatic temperature rise formula The second step to calculate If concrete tensile stress of a position calculated by the second step exceeds the tensile strength of concrete, the total droplet formation regions decreases predetermined area,
With the reduced total casting area as a new total casting area, the third step of returning to the second step, and the tensile stress of the concrete at each position calculated in the second step below the tensile strength of concrete. In addition, the second concrete having the minimum addition rate of the hydration heat reducing agent is placed in the casting area when the addition rate of the hydration heat reduction agent is minimum, and the second concrete is also placed. And a fourth step of pouring the first concrete in a pouring area other than the pouring area.

Further, the mass concrete pouring method according to claim 4 is the mass concrete pouring method according to any one of claims 1 to 3, wherein the hydration heat reducing agent is added and mixed. Is plural, and the second
It is characterized in that the respective addition rates of the concrete are increased as the hydration heat reducing agent is separated from the side of the first concrete without addition of the hydration heat reducing agent.

[0012]

According to the method for placing mass concrete of claim 1, the hydration heat reducing agent is added and mixed so that the tensile stress of the concrete at each position calculated by the temperature stress analysis becomes equal to or lower than the tensile strength of the concrete. By adjusting the pouring area of the above-mentioned second concrete and the addition rate of the hydration heat generation reducing agent, the pouring area of the second concrete when the addition rate of the hydration heat generation reducing agent becomes the minimum is determined. Then, the second concrete having the minimum addition rate of the hydration heat reducing agent is cast in the casting area where the addition rate of the hydration heat reducing agent is minimum, and the second concrete is cast. The first concrete is poured into a casting area other than the area. That is,
When the casting area of the second concrete is increased, the proportion of the area in which the rate of hydration heat generation is slow increases with respect to the entire casting area of the mass concrete to suppress the temperature rise of the entire mass concrete. Increasing the addition rate of the hydration heat reducing agent for the second concrete slows down the hydration heat increase rate of the second concrete, suppressing the temperature rise of the first concrete and increasing the temperature rise of the entire mass concrete. Suppress. Therefore, the hydration heat generation rate of the second concrete has a gentler gradient than the hydration heat generation rate of the first concrete, and the temperature difference between the first concrete and the second concrete is reduced. Since the tensile stress due to temperature expansion is reduced, cracking can be prevented.

As described above, the second concrete placing area is obtained when the tensile stress of the concrete at each of the above positions is equal to or lower than the tensile strength of the concrete and the addition rate of the hydration heat reducing agent becomes the minimum, and Since the second concrete and the first concrete are cast at the same time, the addition rate of the hydration heat reducing agent is made as small as possible to prevent cracking of the mass concrete and to reduce the generation of breathing water. It is possible to prevent the strength of concrete from being reduced and the adhesive force to the reinforcing bar from being weakened due to the voids formed by the water bubbles around the material and the reinforcing bar.

Further, according to the method for placing mass concrete of the above-mentioned claim 2, the tensile strength of the concrete at each position calculated by the temperature stress analysis is equal to or lower than the tensile strength of the concrete. The pouring area and the addition rate of the hydration heat reducing agent are adjusted to find the pouring area of the second concrete when the addition rate of the hydration heat reducing agent becomes the minimum. At this time, when the tensile stress of the concrete at a certain position calculated by the temperature stress analysis does not become equal to or lower than the tensile strength of the concrete even if the pouring area of the second concrete and the addition rate of the hydration heat reducing agent are adjusted The addition of a second concrete placing area and a hydration heat reducing agent so that the total placing area is reduced and the tensile stress of concrete at each position calculated by temperature stress analysis is equal to or lower than the tensile strength of concrete. The rate is adjusted to determine the casting area of the second concrete when the rate of addition of the hydration heat reducing agent of the second concrete is minimum. Further, when the tensile stress of the concrete at the above-mentioned position does not become equal to or lower than the tensile strength of the concrete, the entire casting area is reduced and this is repeated. Then, the second concrete with the minimum addition rate of the hydration heat reducing agent is cast in the casting area where the hydration heat reducing agent has the minimum addition rate, and the area other than the casting area of the second concrete is placed. Pour the first concrete into the casting area.

As described above, the hydration heat reducing agent is added to the second concrete so as to minimize the addition rate, and the tensile stress of the concrete at each position is made equal to or lower than the tensile strength of the concrete. The addition rate of the heat reducing agent is made as small as possible to prevent the cracking of mass concrete and the generation of breathing water is reduced, so that the strength of concrete may be reduced by the voids caused by the water bubbles that have accumulated around aggregates and reinforcing bars. , It is possible to prevent the adhesion to the reinforcing bar from weakening. Further, the addition rate of the hydration heat reducing agent is within a range from the initial value to, for example, a predetermined upper limit value in the casting area of the second concrete, and in a range from the initial value to, for example, a predetermined upper limit value. In the case where the casting area at the time of the minimum is not found, the entire casting area is reduced to enhance the effect of suppressing the temperature rise by the second concrete and suppress the overall temperature rise. Then, by using the reduced total casting area as a new total casting area, the casting area when the addition rate of the hydration heat reducing agent is minimized is obtained, and cracking is prevented even if the casting is performed at one time. The maximum possible casting area can be determined.

According to the method for placing mass concrete of the above-mentioned claim 3, the initial value of the addition rate of the hydration heat reducing agent of the second concrete in which the hydration heat reducing agent is added and mixed in the first step. And set the initial value of the casting area. And
In the second step, the rate of addition of the hydration heat reducing agent for the second concrete is gradually increased from the initial stage, and the second rate is increased for each second rate.
In addition to increasing the casting area of the concrete from the initial value one by one, set the adiabatic temperature rise formula based on each addition rate of the hydration heat reducing agent, and perform the temperature stress analysis based on the adiabatic temperature rise formula to analyze the concrete at each position. The tensile stress is calculated respectively. When the tensile stress of the concrete at a certain position calculated in the second step exceeds the tensile strength of the concrete, in the third step, the total casting area is reduced by a predetermined area, and the reduced total casting area is renewed. Then, the process is returned to the second step as above. On the other hand, when the tensile stress of the concrete at each position calculated in the second step is equal to or less than the tensile strength of the concrete, the second concrete pouring area where the addition rate of the hydration heat reducing agent becomes the minimum in the fourth step A second concrete with the minimum addition rate of the hydration heat reducing agent is poured into the first concrete, and the first concrete is poured into a casting area other than the casting area of the second concrete.

Therefore, the hydration heat reducing agent is added to the second concrete so that the addition rate is minimized, and the tensile stress of the concrete at each position is made equal to or lower than the tensile strength of the concrete. By reducing the additive ratio of the agent as much as possible to prevent the cracking of mass concrete and reduce the generation of breathing water, the strength of concrete may be reduced due to the voids caused by water bubbles accumulated around aggregates and reinforcing bars, It can prevent the adhesive strength from becoming weak. In addition, when the addition rate of the hydration heat reducing agent of the second concrete is in the range from the initial value to, for example, a predetermined upper limit value, and the casting area is in the range from the initial value to, for example, the predetermined upper limit value, temperature stress analysis is performed. When the tensile stress of the concrete at a certain position exceeds the tensile strength of the concrete and the casting area of the second concrete when the addition rate of the hydration heat reducing agent becomes the minimum cannot be found, the entire casting is performed. By reducing the area, the effect of suppressing the temperature rise due to the second concrete is enhanced, and the temperature rise of the whole is suppressed. Then, by using the reduced total casting area as a new total casting area, the casting area when the addition rate of the hydration heat reducing agent is minimized is obtained, and cracking is prevented even if the casting is performed at one time. The maximum possible casting area can be determined.

According to the mass concrete pouring method of claim 4, in the mass concrete pouring method of claim 1 or 3, the second concrete to which a hydration heat reducing agent is added is mixed. A plurality of layers are added so that the addition rate of each layer increases as the hydration heat reducing agent is separated from the side of the first concrete without addition. For this reason, abrupt temperature changes of the first concrete to which the hydration heat reducing agent is not added and the second concrete to which the hydration heat reducing agent is added and mixed are eliminated, and the temperature gradient becomes gentle. The tensile stress due to the temperature difference between the concrete and the second concrete can be reduced to effectively prevent cracking.

[0019]

EXAMPLE A method for placing mass concrete of the present invention will be described in detail below with reference to an example.

FIG. 1 (A) shows a cross-sectional view of mass concrete poured using the method for placing mass concrete according to one embodiment of the present invention, in which 1 is a mold which is not shown. The second concrete containing no added hydration heat reducing agent is immediately placed on the first concrete 1, and a hydrolyzable tannin is added as an example of the hydration heat reducing agent. It is 2 concrete. Second above
The concrete 2 has a vertical casting area L.
The second concrete 2 may be a single layer, or may be divided into n layers (placement regions l ₁ , l ₂ , l ₃ , ..., L _n ) sequentially from the upper side. Further, the total casting area of the mass concrete is D and the casting area is S. Therefore, the casting area of the first concrete 1 is D-Σl _i . However, Σ is the sum of 1 to n for i.

Then, in FIG. 1 (A), the initial values of the divided casting areas L of the second concrete 2 are set to l ₁ , l ₂ ,
, L _n, and the initial value of the addition rate of each casting region l ₁ , l ₂ , ..., L _n is a ₁ , a ₂ , ..., A _n , the tensile stress of concrete at each position is determined by temperature stress analysis. To calculate. Furthermore, FIG.
(B), the addition rate a _1, a _2, ..., to increase sequentially the a _n, added droplet region where every index l _1, l _2, ..., increasing the l _n sequentially, temperature stress The placing area L and the addition rate of the second concrete 2 when the tensile stress of the concrete at each position calculated by the analysis is equal to or less than the tensile strength of the concrete and the addition rate of the hydration heat reducing agent is the minimum are obtained.

The process for determining the casting area in which the addition rate of the hydration heat reducing agent in the above-mentioned mass concrete is minimum will be described below with reference to the flow charts shown in FIGS.

First, in step S101, the following basic conditions 1 to 3 are set.

Setting of casting temperature of concrete Setting of temperature stress calculation model Setting of lower limit value D _min of all casting area D of concrete Setting of number of divided layers n of casting area L of hydration heat reducing agent added concrete Setting of initial value (l ₁ , l ₂ , ..., L _n ) of the casting area L Initial value (a ₁ , a ₂ , ..., _An ) of the addition rate of the above-mentioned casting area L
Setting of upper limit value A _max of addition rate of hydration heat reducing agent Temporary setting of minimum addition rate of hydration heat reducing agent A _{min In} addition, in “setting of concrete placing temperature” in step S101, Since the temperature of concrete after kneading and transportation is different, determine the temperature by estimating it.
The casting temperature of this concrete is used during temperature stress analysis. Further, in "setting of temperature stress analysis model" in step S101, an analysis model used for temperature stress analysis, such as an FEM (finite element method) analysis model, is determined. Also,
The upper limit value A _max of the addition rate of the hydration heat reducing agent is set to 3% by weight, which is a value in which generation of breathing water of concrete is small and strength development of concrete is not extremely delayed.

Next, in step S102, the initial value of the entire casting area D of concrete is set. And step S10
Proceed to 3 and compare the total placing area D of concrete with the lower limit value D _min, and confirm that the entire placing area D of concrete is the lower limit value D.
If it is larger than _min , the process proceeds to step S104. On the other hand, in step S103, the total placing area D of the concrete is the lower limit value D _min.
In the following cases, this process ends.

Next, in step S104, the total cast amount V ₀ (= S × D) of concrete is calculated. Next, step S105.
Then, the addition rate A of the hydration heat reducing agent is replaced with the initial value. However, when the casting area L is divided into a plurality of layers,
The initial value doping ratio of each layer a _1, a _2, ..., respectively replaced with a _n.

The initial values a ₁ , a ₂ , ...
a _n is such gradually increases to a ₁ from the addition ratio a _n of the first concrete 1 side. Also, each of the above-mentioned casting areas l
The sizes of ₁ , 1, ₂ , ..., L _n may be substantially the same or may be differently sized.

Next, by comparing the added factor A and the upper limit value A _max of the heat of hydration reducing agent in step S106, when the addition ratio A is less than the upper limit value A _max, the process proceeds to step S107 shown in FIG.
On the other hand, if the addition rate A is equal to or higher than the upper limit value A _max in step S106, the process proceeds to step S120, and it is determined whether or not the placement area L is registered. For example, the minimum as extremely large values the set value of the temporary addition rate A _min, by the minimum addition ratio A _min is determined whether or not smaller than the set value of the temporary, minimum addition ratio A _min in steps described below Was asked,
It is determined whether or not the placement area L has been registered. Then, if the placement area L is registered in step S120, this processing ends. On the other hand, when the pouring area L is not registered in step S120, the process proceeds to step S121, the total pouring area D of concrete is reduced by a predetermined area, and the process returns to step S103. When the second concrete 2 is divided into a plurality of layers, each addition rate a ₁ ,
a _2, ..., upper limit value A as an additive factor A largest value of a _n
Compare with _max .

Next, in step S107, the conditions determined by the following hydration heat reducing agent are set.

Setting of Adiabatic Temperature Rise Equation Setting Young's Modulus and Tensile Strength Development Equation The above “adiabatic temperature rise equation” of step S107 is
Q (t) = Q _∞ (1-e ^-γt ) Q _∞ : Ultimate adiabatic temperature rise [° C] γ: Ultimate adiabatic temperature rise from date 0 It is a constant related to the rate of temperature rise up to the temperature Q _∞ . The constants of Q _∞ and γ are determined by experiments.

Further, "Young's coefficient expression expression" the step S107, when the Young's modulus in the timber age day t and _{E e (t), E e} (t) = φ (t) × 1.5 × 104 × {F ' _C (t)}
^1/2 [kgf / cm ² ] φ (t): It becomes a correction coefficient of Young's coefficient due to the large influence of creep when the temperature rises. However, the wood age day t, compressive strength f concrete wood age day t _'C (t) _{is, f' C (t) =} t / (a + bt) × f 'C (91) [kg
^{f / cm 2] a, b} : constant f _'C (91): compressive strength of concrete the wood age 91 days [kg
f / cm ² ].

The "expression of tensile strength" of step S107 is as follows: f _t (t) = C {f ' _C (t)} ^1/2 [kgf / cm ² ] C : It becomes a constant.

Next, in step S108, the casting area L of the hydration heat reducing agent-added concrete, that is, the second concrete 2 is replaced with the initial value. However, when the placement area L is divided into a plurality of layers, the placement area of each layer is set to the initial value l ₁ , l ₂ ,
..., l _n are replaced respectively.

Next, in step S109, the pouring area L of the hydration heat reducing agent-added concrete is compared with the total pouring area D,
If the placement area L is less than or equal to the total placement area D, step S110
On the other hand, if the placement area L is larger than the entire placement area D, the process proceeds to step S118.

Then, in step S110, the tensile stress σ of the concrete is calculated by temperature stress analysis. That is, the mass concrete in the casting region D is divided into a plurality of isotropic elastic bodies having a linear expansion coefficient α, and the stress {σ} in each isotropic elastic body after a lapse of T time from the completion of the casting is calculated by the finite element method. It is calculated by ({σ} = {σ _x σ _y σ _z γ _xy } ^T ). The initial strain {ε ₀ } when the isotropic elastic body having the linear expansion coefficient α is subjected to a temperature change of ΔT is {ε ₀ } = {ε _x0 ε _y0 ε _z0 γ _xy0 } ^T = {αΔT αΔT αΔT 0} ^T alpha: coefficient of linear expansion (℃ ^-1) ΔT: stress {sigma ₀ caused by temperature variation (℃) the initial strain {epsilon _{0}} is, {σ 0} = [D} ] {ε 0} [ D]: Determined by the stress-strain matrix.

Next, in step S111, the tensile stress σ of the concrete and the tensile strength f are compared. That is, each position of the above concrete (positions of a plurality of divided isotropic elastic bodies)
The stress {σ} and the tensile strength f of concrete are compared with each other. If the tensile stress σ is larger than the tensile strength f in step S111, that is, if at least one of the stresses {σ} at each position of the concrete is larger than the tensile strength f, the process proceeds to step S122, and the hydration heat reducing agent-added concrete is added. The placement area L is increased and the process returns to step S109. When the placement area L is divided into a plurality of layers,
The casting areas l ₁ , l ₂ , ..., L _n of each layer are increased. On the other hand, if the tensile stress σ is equal to or less than the tensile strength f in step S111, that is, if the stress {σ} at each position of the concrete is equal to or less than the tensile strength f, the process proceeds to step S112.

Next, in step S112, the addition amount M of the hydration heat reducing agent is calculated.

[0038] The amount _{M = Σ (βa i · αl} i · S)
(α ≧ 1, β ≧ 1) However, Σ is the sum of 1 to n for i. Further, alpha is striking region where l _1, l _2, ..., indicate the fold increase of l _n, beta is added rate a _1, a _2, ..., indicate the fold increase of a _n.

Next, in step S113, the pouring amount V of the hydration heat reducing agent added concrete is calculated.

Placing amount V = Σαl _i · S (α ≧ 1) However, Σ is the sum of 1 to n for i.

Next, by comparing the addition ratio A and the minimum addition rate A _min of heat of hydration reducing agent in step S114, when the addition ratio A is less than or equal to the minimum addition rate A _min, the process proceeds to step S115,
If the addition rate A exceeds the minimum addition rate A _min , step S1
Proceed to 17. Then, in step S115, the minimum addition rate A _min of the hydration heat reducing agent is replaced with the addition rate A.

Next, in step S116, the casting area L of the hydration heat reducing agent-added concrete is registered. Then, the process proceeds to step S117, the addition rate A of the hydration heat reducing agent is increased, and the process returns to step S106. When the casting region L is divided into a plurality of layers, the addition rates a ₁ , a ₂ , ..., _An of each layer are increased.

[0043] Thus, hitting region where the second concrete 2 l _1, l _2, ..., rate added with _{l n a 1, a 2,} ..., by adjusting the a _n, the temperature stress analysis The minimum addition rate A _min of the hydration heat reducing agent when the calculated tensile stress of concrete at each position becomes equal to or less than the tensile strength of concrete is determined. Then, the minimum addition rate A of the hydration heat generation reducing agent is added to the casting regions l ₁ , l ₂ , ..., L _n when the addition rate of the hydration heat generation reducing agent is the minimum.
_By pouring the second concrete 2 of min and the first concrete 1 in the casting area other than the casting area of the second concrete 2, the addition rate of the hydration heat reducing agent can be increased as much as possible. By making it smaller, cracking of mass concrete can be prevented, generation of breathing water can be reduced, and the strength of concrete is reduced due to voids caused by water bubbles accumulated around aggregates and reinforcing bars, and adhesion to reinforcing bars is weakened. Can be prevented.

In addition, the above-mentioned placing area L (= l ₁ + l ₂ + ... +
in the range of l _n) until the total droplet formation regions D of the concrete from the initial value, and the minimum addition rate A _min of heat of hydration reducing agent in the range of the addition ratio A is the initial value to the upper limit value A _max is Motomara If not, by reducing the total casting area D of the concrete by a predetermined area and increasing the casting area L of the second concrete 2 with respect to the total casting area D of the concrete, the addition rate of the hydration heat reducing agent is increased. The casting area of the second concrete 2 when A _min becomes the minimum can be obtained. In this case, the first concrete 1 and the second concrete 2
After pouring all the pouring area D of 1 at once, the remaining concrete is poured separately.

Further, the second concrete 2 is divided into a plurality layers, the initial value of the addition ratio of each layer a _1, a _2, ..., a a _n first
The temperature difference between the first concrete 1 and the second concrete 2 does not suddenly change, and the temperature gradient becomes gentle, effectively It can prevent cracking.

In the above embodiment, the temperature stress analysis model is
The tensile stress σ at each position of the mass concrete was calculated by the finite element method, but the method of calculating the tensile stress of concrete is not limited to this, and the compensation plane method (compensation plane meth
od) or the like may be used.

In the above embodiment, mass concrete having a substantially rectangular cross section is placed, but mass concrete 43 having a substantially trapezoidal cross section may be used as shown in FIG. 4 (a). Further, as shown in FIG. 4B, mass concrete 44 having a substantially T-shaped cross section may be used.

Although hydrolyzable tannin was added to the second concrete 1 as a hydration heat reducing agent in the above-mentioned examples, the present invention is not limited to this, and dextrin or the like may be added as a hydration heat reducing agent. .

Although the upper limit value A _max of the addition rate of the second concrete 1 is set to 3% by weight in the above embodiment, the present invention is not limited to this, and the upper limit value of the addition rate of the second concrete may be the breathing water. The addition rate is such that the occurrence of the above is small and the strength of the concrete does not decrease.

In the above embodiment, the casting area L of the second concrete 2 is gradually increased from the initial value to the total casting area D. However, the casting area of the second concrete 2 is a predetermined upper limit from the initial value. You may increase to a value one by one. Further, in the above embodiment, the addition ratios a ₁ , a ₂ , ..., A _n are multiplied by a factor of α, and the casting regions l ₁ , l ₂ , ..., L _n are multiplied by a factor of β. a ₁ ,
a _2, ..., may be respectively increased a _n every predetermined rate, droplet region where l _1, l _2, ..., may be respectively increased l _n for each predetermined region. Further, in the above-mentioned embodiment, the crack due to the internal constraining stress of the mass concrete is prevented, but the external constraining stress, that is, the crack at the joint of the old and new concrete can be prevented.

[0051]

As is apparent from the above, the method for placing mass concrete according to the first aspect of the present invention comprises the first concrete containing no hydration heat reducing agent and the hydration heat reducing agent in the entire casting area. Is a method for placing mass concrete in which it is separately placed into a second concrete mixed with and added, wherein the tensile stress of concrete at each position calculated by temperature stress analysis is equal to or less than the tensile strength of concrete. By adjusting the casting area of the second concrete and the addition rate of the hydration heat reducing agent, the casting area when the addition rate of the hydration heat reducing agent of the second concrete becomes the minimum is determined, and the hydration is performed. The second concrete with the minimum addition rate of the hydration heat reducing agent is cast in the casting area when the addition rate of the heat generation reducing agent is the minimum, and the casting is performed in areas other than the casting area of the second concrete. First concrete in the area The door is intended to pouring.

Therefore, according to the method for placing mass concrete of the first aspect of the invention, the tensile stress of the concrete at each position is equal to or less than the tensile strength of the concrete, and the hydration heat reducing agent has the minimum addition rate. Since the area for placing concrete is determined and the second concrete and the first concrete are placed at the same time, the addition rate of the hydration heat reducing agent is minimized to prevent cracking of mass concrete and breathing. It is possible to reduce the generation of water and prevent the strength of the concrete from being lowered by the voids due to the water bubbles accumulated around the aggregate and the reinforcing bar and the weakening of the adhesive force to the reinforcing bar.

In the method for placing mass concrete according to the second aspect of the present invention, the first concrete in which the hydration heat reducing agent is not added and the second concrete in which the hydration heat reducing agent is added and mixed in the entire casting area. A method for placing mass concrete in which the second concrete is placed so that the tensile stress of the concrete at each position calculated by temperature stress analysis is equal to or lower than the tensile strength of the concrete. And the addition rate of the hydration heat generation reducing agent is adjusted to find the placement area of the second concrete when the addition rate of the hydration heat generation reduction agent becomes the minimum, and the concrete at a certain position calculated by temperature stress analysis. If the tensile stress does not fall below the tensile strength of the concrete, the above-mentioned total casting area is reduced and the tensile stress of concrete at each position calculated by temperature stress analysis is When the addition area of the second concrete and the addition rate of the hydration heat reducing agent are adjusted so as to be less than the tensile strength, the addition rate of the hydration heat reducing agent of the second concrete becomes minimum. The casting area of the second concrete is obtained, and the second concrete having the minimum addition rate of the hydration heat reducing agent is cast in the casting area when the addition rate of the hydration heat reducing agent is minimum. The first concrete is placed in the placement area other than the placement area of the second concrete.

Therefore, according to the method for placing mass concrete of the invention of claim 2, the hydration heat reducing agent is added to the second concrete of the mass concrete so as to minimize the addition rate, and each position is added. Since the tensile stress of the concrete is set to be less than the tensile strength of the concrete, the generation of breathing water is reduced while preventing the cracking of mass concrete, and the strength of the concrete is increased by the voids created by the water bubbles around the aggregate and the reinforcing bars. It is possible to prevent it from lowering or weakening the adhesion to the reinforcing bar. In addition, if the casting area that is the minimum addition rate of the hydration heat reducing agent is not found even after adjusting the casting area of the second concrete and the addition rate of the hydration heat reducing agent, the entire casting Since the area is reduced and the casting area of the second concrete is enlarged with respect to the entire casting area of the concrete, the heat of hydration of the first concrete is radiated through the second concrete,
The temperature rise of the first concrete can be suppressed,
It is possible to find the casting area when the addition rate of the hydration heat reducing agent is the minimum, and to find the maximum casting area that can prevent cracking even if the casting is performed at one time.

In the method for placing mass concrete according to the third aspect of the present invention, the placing area of the first concrete without addition of the hydration heat reducing agent and the hydration heat reducing agent are added and mixed into the entire casting area. Is a method of pouring mass concrete divided into the pouring areas of the prepared second concrete, wherein the initial value of the addition rate of the hydration heat reducing agent of the second concrete in the first step and the pouring area In the second step, the initial value of the addition rate of the hydration heat reducing agent of the second concrete is sequentially increased, and the casting area of the second concrete is changed from the initial value for each addition rate. Adiabatic temperature rise formula based on each addition rate of the hydration exothermic reducing agent is set, and the tensile stress of concrete at each position is calculated by temperature stress analysis based on the adiabatic temperature rise formula. A position calculated in step When the tensile stress of the concrete exceeds the tensile strength of the concrete, the total casting area is reduced by a predetermined area in the third step, and the reduced total casting area is set as a new total casting area, and the above second step is performed. With returning
In the pouring area when the tensile stress of the concrete at each of the positions calculated in the second step in the fourth step is less than the tensile strength of the concrete and the calculated addition rate of the hydration heat reducing agent is the minimum, The second concrete with the minimum addition rate of the hydration heat reducing agent is poured, and the first concrete is poured into the casting area other than the casting area of the second concrete.

Therefore, according to the method for placing mass concrete of the third aspect of the present invention, the hydration heat reducing agent is added to the second concrete so as to minimize the addition rate,
Since the tensile stress of concrete at each position is made equal to or less than the tensile strength of concrete, the cracking of mass concrete is prevented, the generation of breathing water is reduced, and the strength of concrete is increased by the voids created by the water bubbles around aggregates and reinforcing bars. It is possible to prevent deterioration of the adhesive strength and weakening of the adhesive force to the reinforcing bar. Further, the hydration heat reducing agent is used in a range where the addition rate of the second concrete is in the range from the initial value to, for example, a predetermined upper limit value, and in the casting area of the second concrete is from the initial value to, for example, the predetermined upper limit value If the pouring area with the minimum addition rate of is not found, the total pouring area is reduced and the pouring area of the second concrete is increased with respect to the total pouring area to increase the heat of hydration of the first concrete. Two
Since the heat is radiated through the concrete of No. 2, it is possible to suppress the temperature rise of the second concrete, find the casting area when the addition rate of the hydration heat reducing agent becomes the minimum, and cast it all at once. Also, it is possible to find the maximum driving area where cracks can be prevented.

The method of placing mass concrete according to the invention of claim 4 is the method of placing mass concrete according to claim 1 or 3, wherein a plurality of the second concrete in which the hydration heat reducing agent is added is mixed. The addition rate of each layer is increased as the hydration heat reducing agent is separated from the side of the first concrete without addition of the hydration heat reducing agent.

Therefore, according to the method of placing mass concrete of the invention of claim 4, the first concrete and the second concrete
The temperature gradient of the concrete becomes gentle, the tensile stress acting on the concrete is reduced due to the temperature difference between the first concrete and the second concrete, and the crack can be effectively prevented.

[Brief description of drawings]

1 (A) and 1 (B) are cross-sectional views of mass concrete cast by using the method for placing mass concrete according to one embodiment of the present invention.

FIG. 2 is a flowchart showing a method for placing the mass concrete.

FIG. 3 is a flowchart showing a method for placing the above-mentioned mass concrete.

FIG. 4 (a) is a sectional view of mass concrete having a substantially trapezoidal cross section, and FIG. 4 (b) is a sectional view of mass concrete having a T-shaped cross section.

FIG. 5 is a cross-sectional view of conventional mass concrete.

FIG. 6 is a diagram showing temperature changes in the inner layer and the outer layer with respect to the age of the above-mentioned mass concrete.

FIG. 7 is a diagram showing changes in Young's modulus of the inner layer and the outer layer with respect to the age of the mass concrete.

[Explanation of symbols]

 1 ... 1st concrete, 2 ... 2nd concrete.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takanori Kihashi 2-2-2 Matsuzaki-cho, Abeno-ku, Osaka-shi, Osaka Prefecture Okumura Gumi Co., Ltd. (72) Hiroaki Shiraishi 2-chome, Matsuzaki-cho, Abeno-ku, Osaka-shi, Osaka No. 2 No. 2 Okumura Gumi Co., Ltd.

Claims (4)

[Claims] 1. The entire casting area is divided into a casting area of a first concrete containing no hydration heat reducing agent and a casting area of a second concrete containing a hydration heat reducing agent. A method of placing mass concrete to be installed, wherein the second concrete placing area and hydration heat generation reduction are performed so that the tensile stress of concrete at each position calculated by temperature stress analysis is equal to or lower than the tensile strength of concrete. Adjusting the addition ratio of the hydration heat reducing agent to obtain the casting area of the second concrete when the addition ratio of the hydration heat reducing agent is minimized, and the addition ratio of the hydration heat reducing agent is minimized. At this time, the second concrete having the smallest addition rate of the hydration heat reducing agent is cast in the casting area, and the first concrete is cast in the casting area other than the casting area of the second concrete. Pouring concrete Striking 設方 method of mass concrete, characterized in that it comprises a step. 2. The entire casting area is divided into a casting area of the first concrete without addition of the hydration heat reducing agent and a casting area of the second concrete containing the hydration heat reducing agent added and mixed. A method of placing mass concrete to be installed, wherein the second concrete placing area and hydration heat generation reduction are performed so that the tensile stress of concrete at each position calculated by temperature stress analysis is equal to or lower than the tensile strength of concrete. Adjusting the addition rate of the agent to obtain the casting area of the second concrete when the addition rate of the hydration heat reducing agent becomes the minimum, and the casting area of the second concrete and the hydration heat Even if the addition ratio of the reducing agent is adjusted, if the tensile stress of the concrete at a certain position calculated by the temperature stress analysis does not become equal to or lower than the tensile strength of the concrete, reduce the entire casting area,
The addition rate of the hydration heat reducing agent is adjusted by adjusting the pouring region of the second concrete and the addition rate of the hydration heat reducing agent so that the tensile stress of the concrete at each position calculated by the temperature stress analysis is equal to or lower than the tensile strength of the concrete. No. 2 step of obtaining the casting area of the second concrete when the addition rate of the hydration heat reducing agent is the minimum, and the casting when the addition rate of the hydration heat reducing agent is the minimum The second concrete in which the addition rate of the hydration heat reducing agent is minimum is cast into the area, and the first concrete is cast into the casting area other than the casting area of the second concrete. A method for placing mass concrete, comprising the steps of: 3. The entire casting area is divided into a casting area of a first concrete without addition of a hydration heat reducing agent and a casting area of a second concrete containing a hydration heat reducing agent added and mixed. A method for placing mass concrete to be installed, comprising: a first step of setting an initial value of an addition rate of a hydration heat reducing agent of the second concrete and an initial value of a placing area; The addition rate of the hydration heat reducing agent is gradually increased from the initial value of the addition rate, and the casting area of the second concrete is gradually increased from the initial value of the casting area for each addition rate, and the water content is increased. The second step of setting the adiabatic temperature rise formula based on each addition rate of the sum exothermic reducing agent and calculating the tensile stress of concrete at each position by the temperature stress analysis based on the above adiabatic temperature rise formula, respectively. Calculated position When the tensile stress of the cleat exceeds the tensile strength of concrete, the total casting area is reduced by a predetermined area, and the reduced total casting area is set as a new total casting area, and returned to the second step. And the hydration in the casting area when the tensile stress of the concrete at each position calculated in the second step is equal to or less than the tensile strength of the concrete and the addition rate of the hydration heat reducing agent is minimum. The second, which has the smallest addition rate of the exothermic reducing agent
And a fourth step of casting the first concrete in a casting area other than the casting area of the second concrete. . 4. The method for placing mass concrete according to any one of claims 1 to 3, wherein a plurality of the second concretes in which a hydration heat reducing agent is added are mixed. The method for placing mass concrete is characterized in that the addition rate of each of the concretes is increased with increasing distance from the hydration heat reducing agent-free first concrete side.