JP2015197381A - Strength estimation method of concrete, and high-strength concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-strength concrete considering an influence of an aggregate on the compressive strength of the concrete.SOLUTION: The high-strength concrete includes a binding material, fine aggregate, coarse aggregate, water, and admixture, and is prepared so that the compressive strength is 150 N/mmor more. The weight ratio of water to the binding material is 12% or more and 13% or less, and the volume of the coarse aggregate for 1 mconcrete is 0.20 mor more and 0.25 mor less. Alternatively, the weight ratio of water to the binding material is more than 13% and 14% or less, and the volume of the coarse aggregate for 1 mconcrete is 0.25 mor more and 0.27 mor less.

Description

  The present invention relates to a concrete strength estimation method and high-strength concrete.

  High-strength concrete is obtained by increasing the compressive strength by reducing the weight ratio of water to the binder (water binder ratio) and densifying the concrete structure after hardening.

The Architectural Institute of Japan Standards for Construction Work and the Japan Society of Civil Engineers' Standard Specification for Concrete show blending design methods that set the upper limit of the water binder ratio to ensure the required concrete strength.
Therefore, it is common to perform concrete blending design based on these blending design methods.

On the other hand, especially in high-strength concrete, the influence of aggregate on concrete strength is great.
For example, Patent Document 1 discloses that the compressive strength of high-strength concrete is reduced to 135 N / mm ² or less by mixing coarse aggregate into high-strength mortar with compressive strength exceeding 200 N / mm ^2. Yes.

However, a concrete blending design method considering the influence of aggregate has not been established.
Therefore, as shown in Patent Document 2, the present applicant has proposed a method for estimating the concrete strength using the compressive strength and Young's modulus of the mortar portion of the concrete and the compressive strength and Young's modulus of the coarse aggregate.

Japanese Patent No. 4374106 Japanese Patent No. 4268065

According to the method for estimating the strength of concrete in Patent Document 2, it is possible to estimate the effect on the compressive strength of high-strength concrete when using coarse aggregates having different physical properties. It was not possible to estimate the effect on the compressive strength of high-strength concrete when the amount of coarse aggregate per ³ ) was changed.

In the general formulation design concrete, water binder ratio and defines an air volume binder content and to set the amount of water per the concrete 1 m ³ also for automatically determining, aggregate (fine aggregate and Sohone The volume of the material is also determined.
Therefore, when the amount of coarse aggregate is changed, the amount of fine aggregate is also changed, and the physical properties of the mortar are also changed.

  An object of the present invention is to propose a concrete strength estimation method and high-strength concrete in consideration of the influence of aggregate on the compressive strength of concrete.

  In order to solve the above-mentioned problems, the concrete strength estimation method of the present invention includes a preliminary preparation step, a condition setting step, and a strength estimation step.

In the preliminary preparation step, a compression strength test is performed on a plurality of hardened mortar bodies having the same water binder ratio and different fine aggregate volumes, and the upper limit Vs _{0 of the} fine aggregate volume that does not cause a decrease in the strength of the mortar. And a first preparatory step for determining a correction coefficient Ks relating to a decrease in strength of the mortar due to the inclusion of fine aggregate, and estimating the compressive strength Fp of the paste based on the result of the first preparatory step, or A second pre-preparation step of determining the compressive strength Fp of the paste by performing a compressive strength test of the paste, and a plurality of water-binding material ratios and fine aggregate volume ratios Vs / Vm in the mortar that are different in coarse aggregate volume of it performs compression strength test to the cured body of the concrete, the upper limit value Vg 0 of coarse aggregate volume which does not cause reduction in the strength of the _concrete, and, regarding the strength reduction of the concrete due to the mixture of coarse aggregate It contains a third preparatory step of determining a correction factor Kg that.

  The condition setting step is a first condition setting step for determining a unit water amount and a water binder ratio of the concrete whose compressive strength is to be estimated, and calculating a volume Vp of paste and a volume of aggregate contained in the concrete having the volume Vc. The volume Vg of the coarse aggregate and the volume Vs of the fine aggregate included in the aggregate are determined, and the volume Vm of the mortar portion in the concrete is calculated by adding the volume Vs of the fine aggregate to the volume Vp of the paste. And a second condition setting step.

  The strength estimating step includes a mortar strength estimating step for estimating the compressive strength Fm of the mortar based on the compressive strength Fp of the paste, and a concrete strength estimating step for estimating the compressive strength Fc of the concrete based on the compressive strength Fm of the mortar. include.

In the mortar strength estimation step, when Vs / Vm ≦ Vs ₀ / Vm, the compressive strength Fm of the mortar is estimated by Formula 1, and when Vs / Vm> Vs ₀ / Vm, the mortar is calculated by Formula 2. The compression strength Fm is estimated.
Further, in the concrete strength estimation step, when Vg / Vc ≦ Vg ₀ / Vc, the compressive strength Fc of the concrete is estimated by Formula 3, and when Vg / Vc> Vg ₀ / Vc, the concrete is calculated by Formula 4. The compressive strength Fc is estimated.
Fm = Fp (Formula 1)
Fm = {1−Ks × (Vs / Vm−Vs ₀ / Vm)} × Fp (Formula 2)
Fc = Fm (Formula 3)
Fc = {1-Kg × (Vg / Vc−Vg ₀ / Vc)} × Fm (Formula 4)

According to the concrete strength estimation method, the compressive strength of the concrete can be estimated from the compressive strength of the paste contained in the concrete, the volume of the coarse aggregate, and the volume of the fine aggregate.
Therefore, a higher concrete strength can be obtained with the same water binder ratio, and as a result, a margin in the strength management of the concrete is increased.

In addition, it is possible to increase the ratio of the water binder for obtaining the same concrete strength, and hence the amount of the binder can be reduced, and the cracking due to self-shrinkage and hydration heat generation can be suppressed.
Furthermore, the material cost can be reduced by reducing the amount of the binder.

The high-strength concrete of the present invention includes a binder, fine aggregate, coarse aggregate, water, and an admixture, and is formulated so that the compressive strength is 150 N / mm ² or more. Te, it volume of coarse aggregate per concrete 1 m ³ or less than 12% and 13% weight ratio of water to binder is 0.20 m ³ or more and 0.25 m ³ or less, or water to binder is characterized in that the weight ratio of the volume of coarse aggregate per concrete 1 m ³ greater than 13% and 14% or less is 0.25 m ³ or more and 0.27 m ³ or less.

The high-strength concrete is composed of cement and an admixture containing at least silica fume, and the fine aggregate is sand, crushed sand, artificial lightweight fine aggregate, or a mixture of at least two of these. Preferably, the coarse aggregate is made of crushed stone having a maximum size of 20 mm or less, and the weight of water per 1 m ^{3 of} concrete is 140 kg or more and 160 kg or less.

  According to the concrete strength estimation method and high-strength concrete of the present invention, it is possible to generate high-strength concrete in consideration of the influence of aggregate on the compressive strength of concrete.

It is a graph which shows the relationship between the volume ratio of the fine aggregate in mortar, and the ratio of the compressive strength of the mortar with respect to the compressive strength of the mortar whose volume ratio of the fine aggregate is 0.09. It shows the relationship between the volume ratio of coarse aggregate in concrete and the ratio of compressive strength of concrete to compressive strength of mortar. It is a graph which shows the relationship between a unit coarse aggregate volume and the compressive strength of concrete. It is a graph which shows the relationship of the ratio of the compressive strength of concrete with respect to the compressive strength of a unit coarse aggregate volume and a paste.

  In the present embodiment, a case will be described in which the strength of concrete is estimated from the blending of concrete and high strength concrete that expresses a desired strength is generated based on the estimation result.

  The high-strength concrete of this embodiment contains a binder, fine aggregate, coarse aggregate, water, and an admixture.

The binder of the present embodiment is configured to include ordinary Portland cement, slag gypsum-based admixture, and silica fume.
In addition, although the material which comprises a binder is not limited, What consists of cement and the admixture containing at least silica fume is desirable.

In this embodiment, crushed sand having a maximum dimension of 5 mm or less is used as the fine aggregate.
The material constituting the fine aggregate is not limited. For example, sand, crushed sand, artificial lightweight fine aggregate, or a mixture of at least two of them may be used. Further, the maximum size of the fine aggregate is not limited.

In this embodiment, crushed stone having a maximum dimension of 20 mm or less is used as the coarse aggregate.
The material constituting the coarse aggregate and the maximum size of the coarse aggregate are not limited.

Water is added in a range of 140 kg or more and 160 kg or less per 1 m ^{3 of} concrete.
The material constituting the admixture is not limited, but in this embodiment, a polycarboxylic acid ether-based high-performance water reducing agent (SP) and a polyalkylene glycol-based antifoaming agent (Ad) are used.

  The concrete strength estimation method of this embodiment includes a preliminary preparation step, a condition setting step, and a strength estimation step.

  The preparatory process includes three steps (first preparatory step to third preparatory step).

In the first preparatory step, an upper limit value Vs ₀ of the fine aggregate volume that does not cause a decrease in the strength of the mortar and a correction coefficient Ks regarding a decrease in the strength of the mortar due to the mixing of the fine aggregate are determined.
The upper limit value Vs ₀ and the correction coefficient Ks of the fine aggregate volume are determined by performing a compressive strength test on a cured body of a plurality of mortars having the same water binder ratio and different fine aggregate volumes Vs.

The volume ratio Vs ₀ / Vm of the fine aggregate that does not cause the strength reduction of the mortar and the correction coefficient Ks relating to the strength reduction of the mortar due to the mixing of the fine aggregate vary depending on the strength region of the concrete, the type of the fine aggregate used, and the like. Therefore, the value obtained by the compression test is used.

In the first pre-preparation step, first, a mortar is prepared using a binder, water, fine aggregate, and an admixture. In this embodiment, as shown in Table 1, three types of blended mortars are created. Table 2 shows the materials used for the mortar.
In addition, the preparation of the mortar used in the first preliminary preparation step is not limited to three types.

Next, a compression test is performed on the three types of mortar.
In the present embodiment, compression tests were performed on the blends M1 to M3 at a material age of 28 days and 91 days. The result of the compression test is shown in FIG. In addition, the age of the mortar which performs a compression test is not limited.

Here, the horizontal axis of FIG. 1 is Vs / Vm (Vs: volume of fine aggregate, Vm: volume of mortar) which is the volume ratio of fine aggregate in mortar, and the vertical axis is Vs / Vm = 0.09 ( Fm / Fm ₀₉ , which is the ratio of the compressive strength Fm of each mortar to the compressive strength Fm ₀₉ of 28-day strength: 157 N / mm ² , 91-day strength: 184 N / mm ² ).

  As shown in FIG. 1, no clear difference was observed in the compressive strength of the mortar in the formulation of the fine aggregate volume ratio Vs / Vm ≦ 0.27. Therefore, the influence of the fine aggregate amount on the compressive strength of the mortar can be evaluated as indicated by a broken line X in the figure.

Therefore, in this embodiment, the volume ratio Vs ₀ /Vm=0.27 of the fine aggregate that does not cause the strength reduction of the mortar, and the correction coefficient Ks = 0.36 regarding the strength reduction of the mortar due to the mixing of the fine aggregate. Can do. The correction coefficient Ks is the magnitude of the slope of the broken line X when Vs / Vm> 0.27.

In the second preparatory step, the compressive strength Fp of the paste is determined.
The compressive strength Fp of the paste is estimated based on the result of the first preliminary preparation step or determined by performing a compressive strength test of the paste. In the present embodiment, the compressive strength (= 184 N / mm ² ) of material age 91 at Vs / Vm = 0.09 is estimated as the compressive strength Fp of the paste.

In the third preliminary preparation step, an upper limit value Vg ₀ of the coarse aggregate volume that does not cause a decrease in the strength of the concrete and a correction coefficient Kg related to the decrease in the strength of the concrete due to the mixing of the coarse aggregate are determined.

The upper limit value Vg ₀ and the correction coefficient Kg of the coarse aggregate volume are the same for the hardened concrete bodies having the same ratio of water binder and fine aggregate volume ratio Vs / Vm in the mortar but different coarse aggregate volumes Vg. Determine by performing a compressive strength test.

The coarse aggregate volume ratio Vg ₀ / Vc that does not cause a decrease in the strength of concrete and the correction coefficient Kg related to the decrease in the strength of the mortar due to mixing of the coarse aggregate vary depending on the strength region of the concrete, the type of coarse aggregate used, and the like. Therefore, the value obtained by the compression test is used.

  In the third pre-preparation step, first, concrete is prepared with a binder, water, fine aggregate, coarse aggregate, and an admixture. In the present embodiment, one type of mortar (mixed M4) and four types of concrete (mixed C1 to C4) were prepared by the mixing shown in Table 3. Table 4 shows the materials used for the concrete (mixing C1 to C4) and the mortar (mixing M4).

Note that the concrete used in the third preliminary preparation step is not limited to four types.
In this embodiment, concrete (mixing C1-C4) produces | generates by adding a different quantity of coarse aggregate to the mortar of mixing M4 in order to make the mortar part in each mixing | blending into the same conditions.

Next, a compressive strength test is performed on the mortar of the blend M4 and the concrete of the blends C1 to C4. The compressive strength test is performed for each formulation at age 7, 28, 91 days. The result of the compression test is shown in FIG.
In addition, the mixing and age of the concrete which performs a compression test are not limited.

Here, the horizontal axis of FIG. 2 is Vg / Vc, which is the volume ratio of coarse aggregate in concrete, and the vertical axis is a mortar of formulation M4 with Vg / Vc = 0 (7-day strength: 112 N / mm ² , 28-day strength). : 140N / ^mm 2, 91 days strength: a Fc / Fm which is the ratio of compressive strength of concrete for each formulation relative to 160N / mm ^2).

  As shown in FIG. 2, the compressive strength of concrete decreases as the volume ratio Vg / Vc increases. Therefore, the influence of the amount of coarse aggregate on the concrete can be evaluated by a regression line (broken line Y in the figure) passing through the volume ratio Vg / Vc = 0 and the compressive strength ratio Fc / Fm = 1.

In the present embodiment, based on the broken line Y, the volume ratio Vg ₀ / Vc = 0 of the coarse aggregate that does not cause a decrease in the strength of the concrete, and the correction coefficient Kg = 0.30 related to the decrease in the strength of the mortar due to the mixing of the coarse aggregate. The correction coefficient Kg is the magnitude of the inclination of the broken line Y.

The condition setting process includes a first condition setting step and a second condition setting step.
In the first condition setting step, the unit water amount and the water binder ratio of the concrete whose compressive strength is to be estimated are determined, and the volume Vp of the paste contained in the concrete having the volume Vc and the volume of the aggregate are calculated.

  In the present embodiment, the unit water amount of concrete to be estimated and the water binder ratio are set as shown in Table 5. Table 5 shows the volume Vp of the paste and the volume of the aggregate contained in the concrete having the calculated volume Vc. In addition, each material which comprises concrete (mixing C12-C15) is as showing in Table 6.

  In the second condition setting step, the volume Vg of the coarse aggregate and the volume Vs of the fine aggregate contained in the aggregate are determined, and the volume Vs of the fine aggregate is added to the volume Vp of the paste to add a mortar portion in the concrete. The volume Vm is calculated.

  The strength estimation step includes a mortar strength estimation step and a concrete strength estimation step.

In the mortar strength estimating step, the compressive strength Fm of the mortar is estimated based on the compressive strength Fp of the paste.
At this time, when Vs / Vm ≦ Vs ₀ / Vm, the compressive strength Fm of the mortar is estimated by the equation 1, and when Vs / Vm> Vs ₀ / Vm, the compressive strength of the mortar is calculated by the equation 2. Is estimated.

Fm = Fp (Formula 1)
Fm = {1−Ks × (Vs / Vm−Vs ₀ / Vm)} × Fp (Formula 2)
Where Fm: compressive strength of mortar
Fp: Compressive strength of paste
Ks: Correction coefficient for strength reduction of mortar
Vs: Volume of fine aggregate
Vm: Volume of mortar
Vs ₀ / Vm: Upper limit value of Vs / Vm that does not cause reduction in strength of mortar

In the concrete strength estimation step, the compressive strength Fc of the concrete is estimated based on the compressive strength Fm of the mortar.
At this time, when Vg / Vc ≦ Vg ₀ / Vc, the compressive strength Fc of the concrete is estimated by Expression 3, and when Vg / Vc> Vg ₀ / Vc, the compressive strength of the concrete is determined by Expression 4. Is estimated.

Fc = Fm (Formula 3)
Fc = {1-Kg × (Vg / Vc−Vg ₀ / Vc)} × Fm (Formula 4)
Where Fc: compressive strength of concrete
Fm: Compressive strength of mortar
Kg: Correction coefficient for concrete strength reduction
Vg: Volume of coarse aggregate
Vc: Concrete volume
Vg ₀ / Vc: Upper limit value of Vg / Vc that does not cause a decrease in the strength of the concrete

  For example, in the case of studying the influence of the aggregate on the concrete strength with respect to the blend C15 having a water binder ratio of 15%, it is as follows.

As shown in Table 5, since the volume of the paste portion is 0.499m ^{3 /} m 3, each variable in this embodiment is as follows.
Fp: 184 (N / mm ² ) (91-day strength of mortar formulation M1)
Vc: 1 (m ³ )
Vm: 0.499 + Vs (m ³ )
Vs: 0.501-Vg (m ³ )
Vg ₀ / Vc: 0
Kg: 0.30
Vs _{0 /} Vm: 0.27
Ks: 0.36

When the compressive strength Fc of the concrete when the coarse aggregate amount Vg is changed is calculated using Equations 3 and 4 under the above conditions, it is as shown in FIG.
As shown in FIG. 3, the range Unit coarse aggregate volume (corresponding to Vg / Vc) is below about 0.300 M ³ / ^{m 3,} the influence of the concrete strength is relatively small, the unit coarse aggregate volume ( When corresponding to vg / Vc) is greater than 0.300m ³ / ^{m 3,} decrease of the concrete strength becomes remarkable.

Thus, the water binder ratio is 15% formulation C15, it may be set the unit coarse aggregate volume of about 0.300m ³ / ^{m 3.} Here, if the coarse aggregate volume is set too small, the amount of shrinkage of the concrete may increase or the Young's modulus may decrease, so the unit coarse aggregate volume has a small effect on the concrete strength. It is desirable to make it larger.
That is, the coarse aggregate amount Vg is set to a value in the vicinity of which the inclination of the broken line of this graph changes greatly, creating a graph showing the relationship between the compressive strength Fc of concrete and the volume ratio Vg / Vc of the coarse aggregate. Is desirable.

Similarly, FIG. 4 shows the results of calculating the compressive strength of the concrete in which the coarse aggregate amount was changed for each of the blends C12 to C14.
In the blends C12 to C14, the data of the compressive strength of the paste part is not obtained, so the vertical axis in FIG. 4 is Fc / Fp.

4 as shown in, the water binder ratio of 12% Formulation C12 in the unit coarse aggregate volume 0.20 m ³ / ^{m 3} approximately, the water binder ratio is 13% of the formulation C13 Unit coarse aggregate volume 0.25 m ³ / ^{m 3} approximately, it is desirable water binder ratio is set to 14% of the formulation C14 in the unit coarse aggregate volume of about 0.27m ³ / ^{m 3.}

If the concrete strength estimation method of the present embodiment is used, the compression strength is better when the unit coarse aggregate volume is less than 0.3 m ³ / m ^{3 in} the range where the water binder ratio W / B is less than 15%. As a result, high concrete was obtained.

When the unit coarse aggregate volume is set to less than 0.3 m ³ / m ³ as described above, it is necessary to consider the influence on the shrinkage amount and Young's modulus of the concrete. However, concrete shrinkage can be dealt with by using a shrinkage reducing agent. In high-strength concrete, the Young's modulus of the paste portion tends to be close to the Young's modulus of the coarse aggregate, so the influence of the coarse aggregate amount on the Young's modulus is relatively small.

Accordingly, as an optimal value of the unit coarse aggregate volume of high-strength concrete, when the weight ratio of water to the binder is 12% or more and 13% or less, the volume of coarse aggregate per 1 m ^{3 of} concrete is 0.20 m ^3. or more and a 0.25 m ³ or less, in the following cases and 14% by weight exceeds 13% of water to binder, and the volume of coarse aggregate per concrete 1 m ³ is 0.25 m ³ or more 0.27m It can be set to ³ or less.

If the concrete strength estimation method of the present embodiment is used, it is possible to set the optimum aggregate amount of the concrete.
Therefore, it becomes possible to produce higher-strength concrete with the same water binder ratio, and the margin in strength management is increased.

  Moreover, since the ratio of the water binder for obtaining the same concrete strength can be increased, the amount of the binder can be reduced, and cracking due to self-contraction and hydration heat generation can be suppressed.

  It is possible to adjust the strength of concrete by adjusting the balance of coarse aggregate and fine aggregate with the same material unit price, so it is possible to reduce material cost by reducing the amount of binder .

The embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and the above-described components can be appropriately changed without departing from the spirit of the present invention.
For example, steel fibers or organic fibers for the purpose of ensuring toughness and fire resistance may be mixed into the concrete.
Moreover, each material which comprises concrete is not limited to what was shown by the said embodiment.

Claims (4)

Compressive strength test is performed on a hardened body of a plurality of mortars having the same water binder ratio and different fine aggregate volumes, and the upper limit value Vs ₀ of the fine aggregate volume and the mixture of fine aggregates that do not cause a decrease in the strength of the mortar A first preliminary step of determining a correction factor Ks for mortar strength reduction due to
Estimating the compressive strength Fp of the paste based on the result of the first preparatory step or performing a compressive strength test of the paste to determine the compressive strength Fp of the paste;
Compressive strength test is performed on hardened concrete with the same ratio of water binder and volume ratio Vs / Vm of fine aggregate in mortar but different coarse aggregate volume, and coarse aggregate that does not cause deterioration of concrete strength A third pre-preparation step for determining an upper limit value Vg _{0 of the} volume and a correction coefficient Kg relating to a decrease in the strength of the concrete due to mixing of coarse aggregate;
A first condition setting step of determining a unit water amount and a water binder ratio of the concrete whose compressive strength is to be estimated, and calculating a volume Vp of paste and a volume of aggregate contained in the concrete having a volume Vc;
The volume Vg of the coarse aggregate and the volume Vs of the fine aggregate contained in the aggregate are determined, and the volume Vm of the mortar portion in the concrete is calculated by adding the volume Vs of the fine aggregate to the volume Vp of the paste. Two condition setting steps;
A mortar strength estimating step for estimating the compressive strength Fm of the mortar based on the compressive strength Fp of the paste;
A concrete strength estimating step for estimating the compressive strength Fc of the concrete based on the compressive strength Fm of the mortar,
In the mortar strength estimation step, when Vs / Vm ≦ Vs ₀ / Vm, the compressive strength Fm of the mortar is estimated according to Equation 1, and when Vs / Vm> Vs ₀ / Vm, the mortar is determined according to Equation 2. The compressive strength Fm of
In the concrete strength estimation step, when Vg / Vc ≦ Vg ₀ / Vc, the compressive strength Fc of the concrete is estimated by Formula 3, and when Vg / Vc> Vg ₀ / Vc, the concrete is calculated by Formula 4. A method for estimating the strength of concrete, wherein Fc is estimated for compressive strength of the concrete.
Fm = Fp (Formula 1)
Fm = {1−Ks × (Vs / Vm−Vs ₀ / Vm)} × Fp (Formula 2)
Fc = Fm (Formula 3)
Fc = {1-Kg × (Vg / Vc−Vg ₀ / Vc)} × Fm (Formula 4) A high-strength concrete containing a binder, fine aggregate, coarse aggregate, water, and an admixture, and formulated to have a compressive strength of 150 N / mm ² or more,
More than 12% of the weight ratio of water to binder and 13% or less, the volume of coarse aggregate per concrete 1 m ³ is equal to or is 0.20 m ³ or more and 0.25 m ³ or less, high-strength concrete . A high-strength concrete containing a binder, fine aggregate, coarse aggregate, water, and an admixture, and formulated to have a compressive strength of 150 N / mm ² or more,
Beyond the weight ratio of water to binder 13% and 14% or less, the volume of coarse aggregate per concrete 1 m ³ is equal to or is 0.25 m ³ or more and 0.27 m ³ or less, high Strength concrete. The binder comprises a cement and an admixture containing at least silica fume,
The fine aggregate is sand, crushed sand, artificial lightweight fine aggregate or a mixture of at least two of these,
The coarse aggregate is made of crushed stone having a maximum dimension of 20 mm or less,
The high-strength concrete according to claim 2 or ³ , wherein the weight of water per 1 m ^{3 of} concrete is 140 kg or more and 160 kg or less.