JP3378965B2 - Method for improving strength of hardened cement - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a novel combination of hydraulic materials such as cement, fine aggregate and coarse aggregate, water and a water reducing agent, and a combination of unprecedented kneading means and curing method. The present invention relates to a method for improving the strength of a hardened cement material at a construction site of a concrete structure or a secondary concrete product factory at the early stage, for a long time, and dramatically increasing the strength of the hardened concrete material or the hardened cement material.

[0002]

2. Description of the Related Art Conventionally, concrete at a construction site has a compressive strength of 400 to 400% for shortening the construction period, or for concrete at a secondary product factory for early demolding and improvement of operating rate.
High strength concrete of about 1000 [kgf / cm ² ] is required. In that case, as in the concrete mixing shown in Table 5 below, a so-called cement-rich concrete was mixed and used by simply increasing the amount of cement, that is, reducing the conventional W / C. Note that FIG. 7 shows the compressive strength for each maximum curing temperature [° C.] when W / C is 20 [%], 25 [%], and 35 [%]. In this case, the age is 3 [days]. As is clear from the figure, the higher the maximum curing temperature, the higher the compression strength, and the smaller the W / C value, the higher the compression strength.

[0003]

[Table 5]

However, since the concrete by such a conventional method uses a large amount of cement, in a member having a relatively large cross section when cast in situ, the temperature rise amount due to the heat of hydration of the cement becomes large, and the initial amount of cement increases. In the concrete temperature becomes high. Therefore, as shown in Fig.8, the one with a high temperature of 85 [℃] is standard (2
0 [℃]) Initial strength is higher than that of curing, but elongation of long-term strength is small, and it stays at a level lower than that of the specimens that have undergone the standard curing, so that the purpose of generating high strength cannot be achieved. There was a big flaw fundamentally.
In addition, such drawbacks in the prior art also existed in the case of concrete products such as precast concrete by heating and pressure curing in an autoclave.

[0005]

As described above, in order to advance the construction technology and improve the operating rate at the site and factory,
The demand for ultra-high strength concrete that exceeds the conventional high strength of about 1000 [kgf / cm ² ] is extremely large. Therefore, various attempts have been made in the past, such as excessive mixing with a smaller W / B and cooling concrete. However, it is still 1000 at the site or factory.
A method for improving the strength to obtain ultra high strength concrete of [kgf / cm ² ] or more has not been established.

The present invention eliminates the drawbacks of the prior art, solves the problems, and in the normal operation of the site and the factory, a novel hardened cement for obtaining super high strength concrete which exceeds the conventional level. The purpose is to create and provide a method for improving the strength of.

[0007]

The feature of the "method for improving the strength of a hardened cement product" of the present invention is that it is a hydraulic substance obtained by mixing cement, slag powder, silica powder and ettringite powder. The weight ratio of water / hydraulic substance (hereinafter referred to as W / B) to the above-mentioned hydraulic substance is 15% or more 2
5% or less of water, 0.05 to 5 times by weight of the hydraulic substance, and 0.5 to 5 times of the coarse substance by weight of the hydraulic substance. using the composition composed of a 0.1 water reducing agent by weight relative to the hydraulic material, first it was uniformly kneaded with the hydraulic material and the fine aggregate and the water and the water-reducing agent , The coarse aggregate is added, and the mixture is further uniformly kneaded, and then driven into a mold, and if necessary, the maximum temperature range for curing is set to 50 [° C] or more and 180 [° C] or less by warm air and / or hot steam. After the concrete is poured into the range of the time to reach the maximum curing temperature range, 0
That is, it is configured to cure at an atmospheric pressure of not less than atmospheric pressure and not more than 10 [atm] for 48 hours to 48 hours.

In the present invention, the denominator of W / B is the cement added with the admixture, because these admixtures generally form a hydrated compound for a long period of time and contribute to strength generation. Further, the lower limit of W / B is set to 15 [%], because if it is less than that, the kneading cannot be performed uniformly, and the upper limit is set to 25 [%]. This is because the purpose of strength cannot be achieved.

Next, cement is mixed with slag powder and silica.
Powder, fly ash powder, ettringite powder
In the case where only slag powder is selectively used as an admixture from among (referred to as hydraulic materials including cement), the upper limit of cement usage is 90%. This is because the long-term strength cannot be sufficiently generated, and the lower limit is set to 20% because the short-term strength is insufficient at less than 20%.

Next, cement is mixed with slag powder and silica.
Powder, fly ash powder, ettringite powder
In the case where only silica-based powder is used as an admixture and silica fume is selectively used, the lower limit of use of silica fume is set to 5 [%]. This is because the long-term strength is insufficiently generated, and the upper limit is set to 50 [%] because if it exceeds that, the short-term strength becomes insufficient.

Next, in the case of claim 2 , the cement content is set to 90% or less because the elongation of the long-term strength decreases if it exceeds it, and the lower limit is set to 40% or more. The reason is that if it is less than that, short-term strength is insufficiently generated. The reason why the slag powder is 10% or more and the silica fume is 5% or more is because the elongation of the long-term strength becomes too small when the content is lower than that. In addition, slag powder and silica fume are 50
The reason why it is set to [%] or less is that if the amount is exceeded, the amount of cement used becomes too small and the short-term strength becomes insufficient.

Furthermore, in the case of cast-in-place concrete as set forth in claim 3 , the lower limit of the maximum curing temperature range is set to 50 [° C.], and as a result of experiments, the strength can reach an extremely high strength range below that. This is because it becomes difficult to set the upper limit to 120
The reason why the temperature is set to [° C.] is that if the temperature is higher than that, cracking is likely to occur, and at the same time, the long-term strength does not easily become an ultrahigh strength.

Further, as described in claim 4 , in the case of factory concrete, the reason for the lower limit of the maximum curing temperature range is the same as above, but the upper limit is set to 180 [° C.].
This is because even if the temperature exceeds 0 ° C, ultrahigh strength can be generated by increasing the curing pressure, and at a temperature higher than that, the formation of hydrate-hardening mineral crystals by the cement and the admixture is insufficient. Because it will disappear. Further, in this case, the upper limit of the curing pressure of the factory product concrete is set to 10 [atm], because the factory product curing is performed by steam curing in the autoclave, which corresponds to the steam temperature upper limit of about 180 [° C]. .

The cement includes, for example, normal, early-strength and ultra-early-strength Portland cement, and the admixture also includes, for example, fine slag, silica fume, fine fly ash, and ettringite fine powder. Here, ettringite is a high-sulfate calcium aluminate hydrate with an ideal chemical formula of Ca ₆ Al.
_{2 (OH) 12 · (SO} 4) can be represented by ₃ · 26H ₂ O, having expandable. In the present invention, a small amount of the fine powder is used, if necessary, so that the strength of the concrete can be further increased to the general level.

[0015]

According to the present invention, a novel combination of a novel concrete composition using various admixtures containing a particularly small W / B and soluble silica, which has been hardly used in the past, and a new curing maximum temperature range condition are used. The concrete strength can be improved to an ultra-high strength which has been hardly obtained in the past. The mechanism action of generation of this ultra-high strength is that the soluble silicic acid in the admixture is cured more than 50 [° C.] and 120 [° C.] to 180 [° C.] or less in the most suitable maximum curing temperature range, so that All of them effectively become calcium silicate-based hydrated crystals, which enables stable and reliable generation of ultrahigh strength. In particular, as a point that has not been paid much attention in the past, the reaction of the soluble silicic acid to form free calcium in cement and a hydrated cured product increases in proportion to an increase in curing temperature within the above range. As a result, the action of producing a cured product can be promoted without waste. Therefore, it is possible to obtain a result that causes the generation of ultra-high strength, which is significantly higher than the conventional one. Further, the action of ettringite which may be used as necessary is as described above.
Since 6H ₂ O and a very large amount of water for crystallization are required, the growth pressure of the hardened crystal has a particularly large effect, so that the expandability is also large. Therefore, if fine powder of ettringite is used as dispersed as uniformly as possible in uncured concrete, coarse aggregate, fine aggregate, or hardened particles of calcium aluminate that crystallize relatively quickly can be obtained. The expanded particles of the ettringite are pushed into the uncured portions existing in the gaps, resulting in a very solid hardened concrete structure. This, combined with the above-mentioned new formulation and new curing method, has an extremely high strength exerting action which is clearly superior to the conventional one.

[0016]

Embodiments of the present invention will be described below with reference to the drawings and tables.

[0017]

[Example 1] Fig. 1 shows the values of the compressive strength for each age [day] of hardened cemented cement of concrete mix (per 1 m ³ ) shown in Table 1 with W / B 20%. The white circle in the figure has a curing temperature of 2.
The figure shows the case of standard curing at 0 ° C.
The case where a high temperature history of [° C] is received is shown.

[0018]

[Table 1]

In Table 1, the number in parentheses indicates the weight ratio [%] or the ratio to the hydraulic material (cement added with fine slag, silica fume, etc.). As shown in Fig. 1, the material with high temperature curing of 85 ° C is age 91.
Even on [day], the compressive strength is higher than that of 20 [° C] curing.

[0020]

[Example 2] Fig. 2 shows the compressive strength of the hardened cemented cement of the concrete formulation shown in Table 2 for each age [day] in W / B 20 [%]. In the figure, the white circles indicate the case of a curing temperature of 20 [° C.] and the black circles indicate the case of a high temperature curing of 85 [° C.] as in FIG.

[0021]

[Table 2]

As shown in Table 2, as the water-hardening cement, ordinary Portland cement was used and only fine slag was added. As shown in FIG.
High temperature curing at [℃] shows higher compressive strength regardless of age [day]. Further, comparing FIG. 1 and FIG. 2, the compressive strength of the early-strength Portland cement is higher than that of the normal Portland cement.

[0023]

[Embodiment 3] FIG. 3 shows the compressive strength for each age [day] of the hardened cemented cement of concrete mixing shown in Table 3 in W / B22 [%]. In the figure, white circles and black circles are the same as in the first and second embodiments
Similar to the above, the case of curing temperature of 20 [° C.] and 85 [° C.] is shown.

[0024]

[Table 3]

In this case as well, the highest curing has a higher compressive strength regardless of the age [day], but the compressive strength is lower than that of FIG. The compressive strength is slightly lower than that used.

[0026]

[Example 4] The compressive strength value with respect to the age [day] in the case of the mortar formulation (weight ratio) using the ordinary Portland cement shown in Table 4 in W / B25 [%] is shown in Fig. 4, and the ordinary Portland cement is shown. Fig. 5 shows the compressive strength when early-strength Portland cement was used instead of.

[0027]

[Table 4]

As shown in FIGS. 4 and 5, the maximum curing at 85 [° C.] exceeds the standard curing at 20 [° C.], and the compressive strength of the early-strength Portland cement is higher.

FIG. 6 is a diagram showing the temperature history of the cast-in-place concrete for each material age. The solid line shows the case where the maximum curing strength is 85 [° C], the dotted line shows the case of 50 [° C], and the two-dot chain line shows the case of 20 [° C]. In both cases, the age is 48 [h
It can be seen that there is a point of maximum temperature at a point of r] or less.

[0030]

According to the present invention, the following remarkable effects are obtained. 1) Set the ratio of hydraulic material, which is slag-based powder or silica-based powder added to cement, to water within a predetermined value range, kneading conditions, curing temperature range, time to reach the maximum curing temperature, and atmospheric pressure. By setting the above values within a predetermined range, it is possible to obtain an ultrahigh-strength concrete without particularly increasing the amount of cement. 2) The strength improving method for producing this ultra-high-strength concrete can be easily applied not only to factory-produced concrete but also to cast-in-place concrete. 3) In this strength improving method, since each condition range to be controlled is finely determined, stable ultrahigh strength concrete can be produced and stable ultrahigh strength can be obtained. That is, the manufacturing reliability is high. 4) There is a wide variety of cement admixtures, and both ordinary Portland cement and early-strength Portland cement can be used, so it has wide applicability.

[Brief description of drawings]

FIG. 1 shows a curing strength of 20 when W / C = 20 [%].
FIG. 6 is a diagram showing the relationship between the age [day] and the compressive strength of concrete using silica fume at [° C.] and 85 [° C.].

FIG. 2 Curing temperature 20 when W / C = 20 [%]
The line graph which shows the relationship between the age [day] and the compressive strength of the concrete using fine slag at [° C] and 85 [° C].

FIG. 3 is a diagram showing the relationship between age [day] and compressive strength at W / C = 22 [%].

FIG. 4 is a diagram showing the relationship between the age [day] and the compressive strength when ordinary Portland cement is used with W / C = 25 [%].

FIG. 5 is a diagram showing the relationship between the age [day] and the compression hardness when using early-strength Portland cement at W / C = 25 [%].

[Fig. 6] Strength history of structural concrete and age [hr]
FIG.

FIG. 7 is a diagram showing a relationship between maximum curing strength and compressive strength in cement pastes having different W / C.

FIG. 8 is a diagram showing the relationship between age [day] and compressive strength when W / C = 30 [%] in the conventional technique.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-2-283650 (JP, A) JP-A-4-124054 (JP, A) JP-A-62-36059 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C04B 28/02-28/12 C04B 18/14 C04B 40/02

Claims (4)

(57) [Claims] 1. Cement, slag-based powder, silica-based powder and
A hydraulic substance mixed with fine ettringite-based powder, the hydraulic material to water / hydraulic substance (hereinafter referred to as W / B) and water is 15% or more 25% or less by weight, The fine aggregate has a weight of 0.05 to 5 times the weight of the hydraulic material, the coarse aggregate has a weight of 0.05 to 5 times the weight of the hydraulic material, and the fine aggregate has a weight of 0. 1
Using composition comprised by the following water-reducing agent, first it was uniformly kneaded with the water reducing agent and the hydraulic material and the fine aggregate and the water, further uniform by adding the coarse aggregate Knead, then pour into the mold, and, if necessary, warm air and / or
Or the maximum temperature range of curing by hot steam is 50 [℃] or more 1
Curing of cement at 80 [° C.] or less and curing at an atmospheric pressure of not less than atmospheric pressure and not more than 10 [atmosphere], with the range of time for reaching the above-mentioned maximum curing temperature range being 0 to 48 hours after concrete driving. How to improve body strength. 2. The composition of the hydraulic material is a cement in a weight ratio.
90% or less 40% or more, slag-based powder 10
[%] Or more and 50 [%] or less, silica powder 5 [%] or more
Cement according to claim 1, which is 50% or less.
A method for improving the strength of a cured product. 3. When the curing condition is cast-in-place concrete
The maximum curing temperature range is 50 [℃] or more and 120
The temperature is not higher than [° C.] and the atmospheric pressure is atmospheric pressure.
Or the method for improving the strength of a hardened cement material according to item 2. 4. The curing condition is that of factory product concrete.
In some cases, the maximum curing temperature range is 50 [℃] or more 180
[° C] or lower, and the atmospheric pressure is higher than or equal to atmospheric pressure and
Pressure] is less than or equal to 3. The cement hardening according to claim 1 or 2.
How to improve body strength.