JP3017024B2 - Mass concrete casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a mass concrete
The present invention relates to a method of placing mass concrete, which prevents the occurrence of cracks that occur in concrete due to the heat of hydration of concrete after placing (thick concrete with thick placement).

[0002]

2. Description of the Related Art At the time of casting concrete, heat of hydration is generated when concrete hardens due to a hydration reaction between cement and water. The heat of hydration generally reaches the maximum temperature 2 to 5 days after the concrete is cast, and the hydration reaction continues thereafter, and the strength 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 concrete 5 without a hydration heat reducing agent added thereto, which suppresses the hydration heat generation rate, which is poured into a mold 52.
1 shows a cross-sectional view, and FIG. 6 shows a temperature change of the inner layer at a position L ₁ above the bottom of the concrete 51 and a temperature change of an outer layer at a position L ₂ above the bottom of the concrete 51. Concrete 5 above
Although the heat of hydration of the outer layer 1 is dissipated to the outside, the heat of hydration of the inner layer is hard to be dissipated to the outside because the cast thickness is large, and the temperature of the inner layer of the concrete 51 is higher than that of the outer layer of the concrete 51, There is a temperature difference between the inner and outer layers.

[0004] That is, the outer layer of concrete 51 in wood age t ₀ from pouring, after reaching the maximum temperature T _5, but contracts with temperature drop, the inner layer of concrete 51 contrast, wood age t ₁ temperature rise of up to a maximum temperature T ₁ is expanded along with the following. That is, the outer layer of the concrete 51 for easily radiated to the outside, the maximum temperature of the outer layer with respect to the maximum temperature T ₁ of the inner layer of concrete 51 is lowered and T _5, the temperature difference will become one [Delta] T _3. Further, as shown in FIG. 7, the inner layer, the Young's modulus of the outer layer of concrete 51 between the pouring to wood age t ₁ rises to E _1, it becomes solidified state. For this reason, tensile stress and compressive stress act on the inner layer and the outer layer of the concrete 51 according to the temperature difference between them. That is, compressive stress acts on the inner layer concrete having a high temperature by the outer layer concrete having a low temperature, while tensile stress acts on the outer layer concrete by the inner layer concrete. Tensile stress acting on the outer layer of the concrete 51, the inner layer of concrete 51 in wood age t _1, when the temperature difference between the outer layer is the maximum value _{ΔT 4 (= T 1 -T 6} ), becomes largest, cracks It is likely to occur. When the tensile stress generated in the outer layer of the concrete 51 exceeds the tensile strength of the concrete 51, cracks occur in the outer layer of the concrete 51.

[0005] Therefore, as a method of casting mass concrete, there is a method of mixing a hydration heat generation reducing agent into the entire mass concrete to delay a rise in hydration heat and reduce a rise in temperature of the mass concrete (Japanese Patent Application Laid-open No. Sho. 63-11794
No. 1). In this mass concrete, since the heat of hydration is moderate and the heat is easily radiated to the outside, the temperature of the entire mass concrete is lowered, and the temperature difference between the outer layer and the inner layer is reduced. Accordingly, since 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, cracks can be prevented. This method of casting mass concrete not only prevents cracks due to internal restraint stress, but also prevents external restraint stress, that is, cracks at the joint of new and old concrete.

[0006]

However, in the concrete to which the above-mentioned hydration heat generation reducing agent is added, the amount of breathing water increases, and water bubbles accumulate around the aggregate and the reinforcing steel. Together with
There is a problem that the adhesive force to the reinforcing steel is weakened, and the quality of the concrete is reduced.

Accordingly, an object of the present invention is to provide a method of placing mass concrete in which the rate of addition of the hydration heat reducing agent can be reduced as much as possible to prevent cracking.

[0008]

In order to achieve the above-mentioned object, a method for casting mass concrete according to claim 1 is provided. And a method of placing mass concrete in which the concrete is placed separately in the placement area of the second concrete to which the hydration heat reducing agent is added and mixed, wherein the tensile stress of the concrete at each position calculated by the temperature stress analysis is reduced. The addition area of the second concrete and the addition rate of the hydration heat reducing agent are adjusted so as to be equal to or less than the tensile strength of the second concrete. Determining a concrete casting area; and placing the second concrete with the minimum hydration heat reducing agent addition rate in the casting area when the hydration heat reducing agent addition rate is minimum. And the above 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.

According to a second aspect of the present invention, there is provided a mass concrete casting method, wherein the entire concrete casting region is mixed with the first concrete casting region to which no hydration heat generation reducing agent is added and the hydration heat generation reducing agent. A method of placing mass concrete in which the concrete is placed separately in the placement area of the second concrete, wherein the tensile stress of the concrete at each position calculated by the thermal stress analysis is equal to or less than the tensile strength of the concrete. Adjusting the casting area of the concrete and the addition rate of the hydration heat reducing agent to obtain the second concrete casting area when the addition rate of the hydration heat reducing agent is minimized; When the tensile stress of the concrete at a certain position calculated by the above temperature stress analysis does not become lower than the tensile strength of the concrete, even when adjusting the casting area of the second concrete and the addition rate of the hydration heat reducing agent, 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
The concrete casting area and the addition rate of the hydration heat reducing agent are adjusted so that the second concrete placing area when the addition rate of the hydration heat reducing agent of the second concrete is minimized. Obtaining 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 generation reducing agent is the minimum, And placing the first concrete in a casting area other than the casting area of the second concrete.

According to a third aspect of the present invention, there is provided a mass concrete casting method, wherein the entire concrete casting area is mixed with the first concrete casting area to which no hydration heat reducing agent is added and the hydration heat reducing agent. What is claimed is: 1. A method for placing mass concrete in which the concrete is placed separately in a placement area of a second concrete, wherein an initial value of an addition rate of the hydration heat reducing agent of the second concrete and an initial value of the placement area are set. A first step of sequentially increasing the addition rate of the hydration heat reducing agent of the second concrete from the initial value of the addition rate, and setting the casting area of the second concrete for each addition rate. While increasing sequentially from the initial value of the region, an adiabatic temperature rise equation based on each addition rate of the hydration heat generation reducing agent is set, and the tensile stress of the concrete at each position is determined by a temperature stress analysis based on the adiabatic temperature rise equation. The second step of calculating 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,
A third step of returning the reduced entire casting area as a new entire casting area to the second step, and a step in which 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. In addition, the second concrete with the minimum addition rate of the hydration heat reducing agent is poured into the casting area when the addition rate of the hydration heat reduction agent is minimum, and the second concrete And placing the first concrete in a casting area other than the casting area.

According to a fourth aspect of the present invention, there is provided the mass concrete casting method according to any one of the first to third aspects, wherein the hydration heat reducing agent is added and mixed in the second concrete. Is a plurality, and the second
Is characterized in that the respective addition rates of the concrete are increased as the distance from the first concrete side where no hydration heat generation reducing agent is added is increased.

[0012]

According to the mass concrete casting method of the first aspect, the hydration heat generation reducing agent is added and mixed so that the tensile stress of the concrete at each position calculated by the temperature stress analysis is equal to or less than the tensile strength of the concrete. The addition area of the second concrete and the addition rate of the hydration heat generation reducing agent are adjusted to determine the second concrete placement area when the addition rate of the hydration heat generation reducing agent is minimized. Then, the second concrete with the minimum addition rate of the hydration heat reducing agent is poured into the casting area where the addition rate of the hydration heat reduction agent is minimum, and the second concrete is placed with the second concrete. The first concrete is cast in a casting area other than the area. That is,
When the casting area of the second concrete is enlarged, the proportion of the area where the hydration heat generation rate is gentle is increased with respect to the entire casting area of the mass concrete, and the temperature rise of the entire mass concrete is suppressed. When the addition rate of the hydration heat reducing agent of the second concrete is increased, the rate of increase in the hydration heat of the second concrete becomes slower, and the temperature rise of the first concrete is suppressed, and the temperature rise of the entire mass concrete is reduced. Suppress. Therefore, the gradient of the hydration heat generation rate of the second concrete is gentler than that of the first concrete, and the temperature difference between the first concrete and the second concrete is reduced. Thus, since the tensile stress due to temperature expansion is reduced, cracks can be prevented.

In this way, the concrete placing area of the second concrete when the tensile stress of the concrete at each of the above positions is equal to or less than the tensile strength of the concrete and the addition rate of the hydration heat reducing agent is minimized is determined. Since the second concrete and the first concrete are poured at once, the rate of addition of the hydration heat reducing agent is made as small as possible, and the occurrence of breathing water is reduced while preventing cracking of the mass concrete. It is possible to prevent a decrease in the strength of the concrete and a decrease in the adhesive force to the reinforcing bar due to voids formed by water bubbles accumulated around the material and the reinforcing bar.

Further, according to the method for casting mass concrete of the second aspect, the second concrete is placed so that the tensile stress of the concrete at each position calculated by the thermal stress analysis becomes equal to or less than the tensile strength of the concrete. The casting area and the addition rate of the hydration heat generation reducing agent are adjusted to determine the second concrete placement area when the addition rate of the hydration heat generation reducing agent is minimized. At this time, if the tensile stress of the concrete at a certain position calculated by the temperature stress analysis does not become lower than the tensile strength of the concrete even if the casting area of the second concrete and the addition rate of the hydration heat generation reducing agent are adjusted. The addition of the second concrete casting area and the hydration heat generation reducing agent such that the entire casting area is reduced and the tensile stress of the concrete at each position calculated by the temperature stress analysis becomes equal to or less than the tensile strength of the concrete. By adjusting the rate, the casting area of the second concrete when the addition rate of the hydration heat reducing agent of the second concrete is minimized is determined. Further, when the tensile stress of the concrete at the certain position does not become lower than the tensile strength of the concrete, the entire casting area is reduced, and this is repeated. Then, the second concrete with the lowest addition rate of the hydration heat reducing agent is poured into the casting area where the hydration heat reducing agent has the minimum addition rate, and the second concrete other than the second concrete casting area is added. The first concrete is cast in the casting area.

As described above, the hydration heat generation 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 less than the tensile strength of the concrete. Since the rate of addition of the heat generation reducing agent is reduced as much as possible to prevent cracking of mass concrete and reduce the generation of breathing water, the strength of concrete is reduced by voids formed by water bubbles accumulated around aggregates and reinforcing bars. In addition, it is possible to prevent the adhesion to the reinforcing bar from becoming weak. Further, when the casting area of the second concrete is in the range from the initial value to, for example, a predetermined upper limit, and the addition rate is in the range from the initial value to, for example, a predetermined upper limit, the addition rate of the hydration heat generation reducing agent is increased. If the casting area when the value of the minimum is not found, the entire casting area is reduced, thereby increasing the effect of suppressing the temperature rise by the second concrete and suppressing the overall temperature rise. The reduced total casting area is used as a new total casting area to find a casting area in which the rate of addition of the hydration heat reducing agent is minimized. The maximum possible casting area can be determined.

Further, according to the mass concrete casting method of the third aspect, the initial value of the addition rate of the hydration heat reducing agent of the second concrete to which the hydration heat reducing agent is added and mixed in the first step. And the initial value of the casting area. And
In the second step, the addition rate of the hydration heat reducing agent of the second concrete is gradually increased from the beginning, and the second
The casting area of concrete is gradually increased from the initial value, and the adiabatic temperature rise formula based on each rate of addition of the hydration exothermic reducing agent is set. Calculate the tensile stress respectively. When the tensile stress of the concrete at a certain position calculated in the second step exceeds the tensile strength of the concrete, the entire casting area is reduced by a predetermined area in a third step, and the reduced entire casting area is newly added. The process returns to the second step as the entire casting area. On the other hand, if 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 fourth concrete placement area in which the addition rate of the hydration heat reducing agent is minimized Then, the second concrete with the minimum addition rate of the hydration heat reducing agent is poured, and the first concrete is poured into a casting area other than the casting area of the second concrete.

Therefore, the hydration heat generation 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 less than the tensile strength of the concrete. The rate of addition of the agent is as small as possible to prevent cracking of the mass concrete and reduce the generation of breathing water.Therefore, the voids due to water bubbles accumulated around the aggregates and the reinforcing steel reduce the strength of the concrete, Adhesive strength can be prevented from weakening. In addition, the rate of addition of the hydration heat reducing agent of the second concrete ranges from an initial value to, for example, a predetermined upper limit, and the casting area ranges from the initial value to, for example, a predetermined upper limit. If the determined concrete tensile stress exceeds the tensile strength of the concrete and the addition rate of the hydration exothermic reducing agent is minimized, and the second concrete placing area is not determined, the entire casting is performed. By reducing the area, the effect of suppressing the temperature rise by the second concrete is enhanced, and the overall temperature rise is suppressed. The reduced total casting area is used as a new total casting area to find a casting area in which the rate of addition of the hydration heat reducing agent is minimized. The maximum possible casting area can be determined.

According to the method for placing mass concrete of the fourth aspect, in the method for placing mass concrete of the first or third aspect, the second concrete to which the hydration heat generation reducing agent is added and mixed is used. A plurality of layers are added so that the addition rate of each layer increases as the distance from the first concrete side where no hydration heat generation reducing agent is added is increased. For this reason, a rapid temperature change between 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 is eliminated, so that 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]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method of casting mass concrete according to the present invention will be described in detail with reference to an embodiment.

FIG. 1A is a cross-sectional view of a mass concrete cast by using the mass concrete casting method according to one embodiment of the present invention. The first concrete 2 without the added hydration heat reducing agent is immediately cast on the first concrete 1, and the first concrete 2 is added with the hydrolyzable tannin as an example of the hydration heat reducing agent. 2 concrete. The second
In the concrete 2, the casting area in the vertical direction is L.
The second concrete 2 may be a single layer or may be divided into n layers (placed areas l ₁ , l ₂ , l ₃ ,..., L _n ) in order from the upper side. Further, the entire casting area of the mass concrete is D, and the casting area is S. Therefore, striking region where the first concrete 1 is a D-Σl _i. Where Σ is the sum of 1 to n for i.

In FIG. 1 (A), the initial values of the divided casting area L of the second concrete 2 are represented by l ₁ , l ₂ ,
..., and l _n, each droplet region where _{l 1, l 2, ...,} a 1 the initial value of the addition ratio of l _n, a _2, ..., as a _n, tensile concrete at each position by Thermal Stress Analysis Stress Is calculated. Further, 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 casting 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 lower than the tensile strength of the concrete and the addition rate of the hydration heat reducing agent is the minimum.

The process for finding the casting area where the addition rate of the hydration heat reducing agent of the mass concrete is minimum will be described with reference to the flow charts shown in FIGS.

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

[0024] Concrete striking設温of the set temperature stress calculation model setting concrete of the total droplet region where the lower limit value D _min of setting hydration exothermic reducing additive for concrete droplet region where L set above division layer number n of the D Setting of initial value (l ₁ , l ₂ ,..., L _n ) of casting area L Initial value (a ₁ , a ₂ ,..., _An ) of the addition rate of casting area L
Setting water upper limit of the addition ratio of the sum fever-reducing agent A _max minimum addition rate A _min of setting hydration heat generation-reducing agent temporary In "Setting of the punching設温of the concrete" in step S101, the season Since the temperature of the concrete after kneading and transporting is different, the temperature is estimated and determined.
The concrete placement temperature is used at the time of thermal stress analysis. In “setting of thermal stress analysis model” in step S101, an analysis model used for thermal stress analysis, for example, an FEM (finite element method) analysis model is determined. Also,
The upper limit value _Amax of the addition rate of the hydration heat reducing agent is set to 3% by weight as a value that causes less generation of bleeding water in the concrete and does not extremely delay the strength development of the concrete.

Next, in step S102, an initial value of the entire concrete placing area D is set. Then, step S10
Proceeding to 3, the concrete placing area D is compared with the lower limit value _Dmin, and the concrete placing area D becomes the lower limit value D _min.
If it is larger than _min , the process proceeds to step S104. On the other hand, in step S103, the entire casting area D of the concrete reaches the lower limit value _Dmin.
In the following cases, this process ends.

Next, in step S104, the total amount of concrete V ₀ (= S × D) is calculated. Next, step S105
Then, the addition rate A of the hydration heat generation 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. In addition, each of the above-mentioned casting areas l
The size of ₁ , l ₂ ,..., L _n may be substantially the same or different from each other.

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 larger than the upper limit value _Amax in step S106, the process proceeds to step S120, and it is determined whether or not the casting area L has been 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 Asked for,
It is determined whether or not the casting area L has been registered. If the placement area L has been registered in step S120, this processing ends. On the other hand, if the casting area L is not registered in step S120, the process proceeds to step S121, where the total casting area D of the 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, the respective addition rates 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, conditions are determined which are determined by the following hydration heat generation reducing agent.

Setting of Adiabatic Temperature Rise Equation Setting of Young's Modulus and Tensile Strength Expression Equation The “adiabatic temperature rise equation” in step S107 is based on the material age t.
The adiabatic temperature rise When Q (t) in _{Japan, Q (t) = Q ∞} (1-e -γt) Q ∞: Ultimate adiabatic temperature rise [° C.] gamma: Ultimate adiabatic temperature rise from the wood age 0 days It is a constant relating to the temperature rise rate between reaching the temperature Q _∞. Note that the constants of Q _の and γ are determined by experiments.

Further, the "expression of Young's modulus" in step S107 is as follows: If the Young's modulus on t-day of material age is E _e (t), E _e (t) = φ (t) × 1.5 × 10 4 × ｛F ' _C (t)｝
^1/2 [kgf / cm ² ] φ (t): It is a correction coefficient of the Young's modulus due to the large influence of creep when the temperature rises. However, on the t age, the compressive strength f ' _C (t) of the concrete on the t age is f' _C (t) = t / (a + bt) x f ' _C (91) [kg
f / cm ² ] a, b: constants f ' _C (91): compressive strength of concrete on the 91st grade [kg]
f / cm ² ].

Further, the “tensile strength expression formula” of step S107 is as follows: f _t (t) = C {f ′ _C (t)} ^1/2 [kgf / cm ² ] C : Constant.

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

Next, in step S109, the casting area L and the entire casting area D of the hydration heat generation reducing agent-added concrete are compared.
If the casting area L is equal to or less than the entire casting area D, step S110
On the other hand, when the casting area L is larger than the entire casting area D, the process proceeds to step S118.

Then, in step S110, the tensile stress σ of the concrete is calculated by the temperature stress analysis. That is, the mass concrete in the casting area 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 determined by the finite element method. (｛Σ｝ = ｛σ _x σ _y σ _z γ _xy ｝ ^T ). Note that the initial strain ｛ε ₀と き when the isotropic elastic body having the linear expansion coefficient α receives 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 a stress-strain matrix.

Next, in step S111, the tensile stress σ of the concrete is compared with the tensile strength f. In other words, each position of the concrete (the position of a plurality of divided isotropic elastic bodies)
Is compared with the concrete tensile strength f. If the tensile stress σ is greater 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 greater than the tensile strength f, the process proceeds to step S122, and The casting area L is increased, and the process returns to step S109. When the casting 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 all the stresses {σ} at each position of the concrete are 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 generation reducing agent is calculated.

[0038] The amount _{M = Σ (βa i · αl} i · S)
(α ≧ 1, β ≧ 1) where 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 amount V of concrete to be added with the hydration heat generation reducing agent is calculated.

Driving amount V = Σαl _i · S (α ≧ 1) where 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 _Amin , step S1
Proceed to 17. Then, the minimum addition rate A _min of the hydration heat generation reducing agent is replaced with the addition rate A in step S115.

Next, in step S116, the casting area L of the hydration heat generation reducing agent-added concrete is registered. Then, the process proceeds to step S117, in which the addition rate A of the hydration heat generation reducing agent is increased, and the process returns to step S106. When the casting area 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 _Amin of the hydration heat generation reducing agent when the calculated tensile stress of the concrete at each position becomes equal to or less than the tensile strength of the concrete is determined. The striking region where l ₁ when doping ratio is the minimum of the wettable fever reducing agent, l _2, ..., a minimum addition rate of hydration exothermic reducing agent to l _n A
_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 generation reducing agent can be reduced as much as possible. Reduce the size to prevent cracking of the mass concrete and reduce the generation of breathing water, and reduce the strength of the concrete due to voids formed by aggregates and water bubbles around the reinforcement, and the adhesion to the reinforcement decreases. Can be prevented.

The driving 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 When there is no concrete, the total area D of the concrete is reduced by a predetermined area, and the area L of the second concrete 2 is increased with respect to the entire area D of the concrete. The casting area of the second concrete 2 when A _min is minimum can be obtained. In this case, the first concrete 1 and the second concrete 2
After the entire casting area D is cast at once, the remaining concrete is cast 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
As the distance from the concrete 1 increases, the temperature difference between the first concrete 1 and the second concrete 2 does not change rapidly, the temperature gradient becomes gentle, and the Cracks can be prevented.

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

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

In the above embodiment, hydrolyzable tannin was added to the second concrete 1 as a hydration heat reducing agent. However, the present invention is not limited to this, and dextrin or the like may be added as a hydration heat reducing agent. .

In the above embodiment, the upper limit A _max of the addition rate of the second concrete 1 was set to 3% by weight. However, the present invention is not limited to this. It is sufficient that the rate of addition is small so that 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 entire casting area D. However, the casting area of the second concrete 2 is increased from the initial value by a predetermined upper limit. It may increase sequentially to the value. In the above embodiment, the addition rate a _1, a _2, ..., multiplied by the magnification of α to a _n, striking region where l _1, l _2, ..., has been multiplied by the magnification of β to l _n, addition rate 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 embodiment, the crack due to the internal restraint stress of the mass concrete is prevented. However, the external restraint stress, that is, the crack at the joint of the old and new concrete can be prevented.

[0051]

As is apparent from the above description, in the method for casting mass concrete according to the first aspect of the present invention, the first concrete and the hydration heat reducing agent to which no hydration heat reducing agent is added are added to the entire casting area. Is a method of placing mass concrete in which the concrete is divided and poured into the second concrete, wherein the tensile stress of the concrete at each position calculated by the thermal stress analysis is equal to or less than the tensile strength of the concrete. The casting area where the addition rate of the hydration heat reducing agent of the second concrete is minimized is determined by adjusting the casting area of concrete 2 and the addition rate of the hydration heat reducing agent. The second concrete where the addition rate of the hydration heat reducing agent is minimum is cast in the casting area where the addition rate of the heat generation reducing agent is minimum, and the casting is performed in a region other than the casting area of the second concrete. The first concrete The door is intended to pouring.

Therefore, according to the method for casting mass concrete of the first aspect of the present invention, the second embodiment in which 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 concrete casting area is determined and the second concrete and the first concrete are cast at once, the addition rate of the hydration heat generation reducing agent is made as small as possible to prevent cracking of the mass concrete and breathing. By reducing the generation of water, it is possible to prevent a decrease in the strength of the concrete or a decrease in the adhesive force to the reinforcing bar due to voids formed by water bubbles accumulated around the aggregate or the reinforcing bar.

In the method for casting mass concrete according to the second aspect of the present invention, the entire casting area is filled with the first concrete without the hydration heat reducing agent and the second concrete with the hydration heat reducing agent added. A method of placing mass concrete in which concrete is divided and poured into the concrete, wherein the tensile strength of the concrete at each position calculated by the thermal stress analysis is equal to or less than the tensile strength of the concrete. And the addition rate of the hydration heat reducing agent is adjusted to determine the second concrete placing area when the addition rate of the hydration heat reducing agent is minimized, and the concrete at a certain position calculated by the thermal stress analysis is obtained. If the tensile stress does not fall below the tensile strength of the concrete, reduce the entire casting area and reduce the tensile stress of the concrete at each position calculated by the thermal stress analysis. The casting area and the addition rate of the hydration heat reducing agent of the second concrete are adjusted so as to be equal to or less than the tensile strength, and the addition rate of the hydration heat reducing agent of the second concrete is minimized. The casting area of the second concrete is obtained, and the second concrete with the lowest 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. At the same time, the first concrete is cast in a casting area other than the second concrete casting area.

Therefore, according to the mass concrete casting method of the second aspect of the present invention, the hydration heat generation reducing agent is added to the second concrete of the mass concrete so as to minimize the addition rate. The concrete's tensile stress is made equal to or less than the concrete's tensile strength. It is possible to prevent lowering and weakening of the adhesive force to the reinforcing bar. In addition, even if the addition area of the second concrete and the addition rate of the hydration exothermic reducing agent are adjusted, the casting area in which the minimum addition rate of the hydration exothermic reducing agent is not obtained. Reducing the area and enlarging the area for placing the second concrete relative to the entire area for placing concrete, so that the heat of hydration of the first concrete is dissipated through the second concrete,
The temperature rise of the first concrete can be suppressed,
The casting area where the addition rate of the hydration heat reducing agent is minimized is determined, and the maximum casting area that can prevent cracking even when the casting is performed at once can be determined.

Further, in the mass concrete casting method according to the third aspect of the present invention, the entire casting area is filled with the first concrete casting area where no hydration heat generation reducing agent is added and the hydration heat generation reducing agent is added and mixed. A method for placing mass concrete in which the second concrete is placed separately in the placement area, wherein the initial value of the addition rate of the hydration heat reducing agent of the second concrete and the placement area in the first step The initial value of the addition rate of the hydration heat reducing agent of the second concrete is sequentially increased in the second step, and the casting area of the second concrete is changed from the initial value for each addition rate. Along with the successive increase, an adiabatic temperature rise formula based on the respective addition rates of the hydration heat reducing agent is set, and the tensile stress of the concrete at each position is calculated by a temperature stress analysis based on the adiabatic temperature rise formula. A certain position calculated in the step When the tensile stress of the concrete exceeds the tensile strength of the concrete, the entire casting area is reduced by a predetermined area in the third step, and the reduced entire casting area is set as a new overall casting area, and the above-mentioned second step is performed. Along with returning
In the fourth step, the placement area where the tensile stress of the concrete at each of the positions calculated in the second step is equal to or less than the tensile strength of the concrete and the calculated addition rate of the hydration heat reducing agent is minimized, A second concrete in which the addition rate of the hydration heat reducing agent is minimum is cast, and the first concrete is cast in a casting area other than the casting area of the second concrete.

Therefore, according to the method for casting mass concrete according to the third aspect of the present invention, the hydration heat generation reducing agent is added to the second concrete so as to minimize the addition rate.
Since the tensile stress of the concrete at each position is less than the tensile strength of the concrete, it prevents cracking of the mass concrete, reduces the generation of breathing water, and reduces the strength of the concrete by voids due to water bubbles accumulated around aggregates and reinforcing bars. Can be prevented, and the adhesion to the reinforcing bar can be prevented from weakening. Further, the hydration exothermic reducing agent is used when the addition rate of the second concrete is in a range from an initial value to, for example, a predetermined upper limit, and the casting area of the second concrete is in a range from the initial value to, for example, a predetermined upper limit. When the casting area with the minimum addition rate of is not determined, the entire casting area is reduced, and the casting area of the second concrete with respect to the entire casting area is increased, so that the heat of hydration of the first concrete is reduced. 2
Since the heat is radiated through the concrete, the rise in the temperature of the second concrete can be suppressed, and the casting area at which the addition rate of the hydration heat reducing agent is minimized is determined. In addition, it is possible to obtain a maximum casting area in which cracks can be prevented.

The method of placing mass concrete according to the invention of claim 4 is the method of placing mass concrete of claim 1 or 3, wherein the second concrete to which a hydration heat generation reducing agent is added and mixed is used. Wherein the addition rate of each layer is increased as the distance from the first concrete side where no hydration heat generation reducing agent is added is increased.

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

[Brief description of the drawings]

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

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

FIG. 3 is a flowchart showing a method of placing the mass concrete.

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

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

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

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

[Explanation of symbols]

 1 ... first concrete, 2 ... second concrete.

Continuation of the front page (72) Inventor Hiroaki Shiraishi 2-2-2 Matsuzakicho, Abeno-ku, Osaka-shi, Osaka Prefecture Okumura Gumi Co., Ltd. (56) References JP-A-58-156627 (JP, A) (58) Investigated Field (Int.Cl. ⁷ , DB name) E04G 21/02 103-104

Claims (4)

(57) [Claims] 1. An entire casting area is divided into a casting area of a first concrete to which a hydration heat reducing agent is not added and a casting area of a second concrete to which a hydration heat reducing agent is added and mixed. A method of placing mass concrete to be installed, wherein the second concrete placing area and the reduction of hydration heat are adjusted so that the tensile stress of the concrete at each position calculated by the thermal stress analysis is equal to or less than the tensile strength of the concrete. Adjusting the addition rate of the hydration heat reducing agent to determine the casting area of the second concrete when the addition rate of the hydration heat reducing agent is minimized; The second concrete in which the addition rate of the hydration heat reducing agent is minimum is cast in the casting area at the time, and the first concrete is cast in the casting area other than the casting area of the second concrete. Pour 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 a first concrete to which a hydration heat reducing agent is not added and a casting area of a second concrete to which a hydration heat reducing agent is added and mixed. A method of placing mass concrete to be installed, wherein the second concrete placing area and the reduction of hydration heat are adjusted so that the tensile stress of the concrete at each position calculated by the thermal stress analysis is equal to or less than the tensile strength of the concrete. Adjusting the addition rate of the agent to determine the casting area of the second concrete when the addition rate of the hydration heat reducing agent is minimized; Even if the addition rate 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 fall below the tensile strength of the concrete, the entire casting area is reduced,
The second concrete placement area and the rate of addition of the hydration heat reducing agent were adjusted so that the tensile stress of the concrete at each position calculated by the temperature stress analysis became equal to or less than the tensile strength of the concrete. A step of obtaining the second concrete placing area when the addition rate of the hydration heat reducing agent of the concrete is minimum; and the placing when the addition rate of the hydration heat reducing agent is minimum. The second concrete where the addition rate of the hydration heat reducing agent is the smallest is cast in the area, and the first concrete is cast in a place other than the cast area of the second concrete. And placing the mass concrete. 3. The entire casting area is divided into a casting area of the first concrete to which the hydration heat reducing agent is not added and a casting area of the second concrete to which the hydration heat reducing agent is added and mixed. A method of setting mass concrete to be set, comprising: a first step of setting an initial value of an addition rate of a hydration heat generation reducing agent of the second concrete and an initial value of a setting area; The addition rate of the hydration heat reducing agent is sequentially increased from the initial value of the addition rate, and the casting area of the second concrete is sequentially increased from the initial value of the casting area for each addition rate, and the water content is increased. A second step of setting an adiabatic temperature rise equation based on each addition rate of the sum exothermic reducing agent and calculating a tensile stress of concrete at each position by a temperature stress analysis based on the adiabatic temperature rise equation; The calculated position of the When the tensile stress of the cleat exceeds the tensile strength of the concrete, the entire casting area is reduced by a predetermined area, and the reduced entire casting area is set as a new overall casting area and the process returns to the second step. And the step of: placing the hydration in the casting area when the tensile stress of the concrete at each of the positions 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 minimized. The second method wherein the addition rate of the heat release reducing agent is the minimum.
And placing the first concrete in a casting area other than the casting area of the second concrete. . 4. The mass concrete casting method according to claim 1, wherein the second concrete to which the hydration heat reducing agent is added and mixed is plural, and Characterized in that the addition rate of each of the concrete is increased with increasing distance from the first concrete side to which the hydration heat reducing agent is not added.