JP6965136B2 - Construction method of mortar or concrete using ultra-fast hard cement - Google Patents

Description

The present invention relates to a method for constructing mortar or concrete using ultrafast hard cement.

For the purpose of early demolding of concrete products, repair work, emergency work, shortening of construction period of general work, etc., ultra-fast hard cement that can obtain strength at an early stage is used. This ultrafast-hardening cement originally has fast-hardening properties, but lithium carbonate, sodium sulfate, etc. are used as curing accelerators in order to further improve the early strength and secure the pot life and fluidity (Patent Document 1). 2, 2).

Japanese Unexamined Patent Publication No. 2000-23959 Japanese Unexamined Patent Publication No. 2006-335620

However, it has been found that the early strength development of the conventional ultrafast hard cement is affected by the environmental temperature, and the early strength development is different between the cold region and the high temperature region, so that there is a problem in workability. In addition, the source of lithium carbonate, which is widely used as a curing accelerator, is limited to South America and China. In recent years, the demand for it as a battery material has increased, making it difficult to obtain and soaring in price.
Therefore, an object of the present invention is to reduce the amount of lithium carbonate used and to provide an optimum method for constructing a mortar or concrete using ultrafast hard cement according to the environmental temperature.

Therefore, as a result of various studies on the optimum early strength development and reduction of the amount of lithium carbonate used in response to changes in the environmental temperature, the present inventor determined the amount of lithium carbonate and sodium sulfate used depending on the environmental temperature of the construction site (construction site). The present invention was completed by finding that the optimum construction conditions corresponding to the change in the environmental temperature can be obtained by changing the temperature.

That is, the present invention provides the following [1] to [5].

[1] A method for constructing mortar or concrete using ultrafast-hardening cement containing a hardening accelerator.
(1) In the construction site where the temperature is less than 13 ° C., (a) sodium sulfate or potassium sulfate alone, or (a) sodium sulfate or potassium sulfate and (b) lithium carbonate are used as the curing accelerator (a) / (b). Using super fast-hardening cement used in combination with a mass ratio of 1 or more,
(2) In a construction site where the temperature is above 13 ° C and below 25 ° C, (a) sodium sulfate or potassium sulfate and (b) lithium carbonate are used as a curing accelerator at a mass ratio of (a) / (b) of 0.5 to 2. Using the combined ultra-fast hard cement,
(3) A construction method characterized in that (b) ultrafast-hardening cement using lithium carbonate alone is used as a curing accelerator in a construction site having a temperature of more than 25 ° C.
[2] The construction method according to [1], wherein the total amount of the curing accelerator used is 0.5 to 2 parts by mass with respect to 100 parts by mass of Portland cement.
[3] The construction method according to [1] or [2], wherein the ultrafast-hardening cement is an Irwin-based ultrafast-hardening cement or a calcium fluoroaluminate-based ultrafast-hardening cement.
[4] As a curing accelerator, (a) sodium sulfate or potassium sulfate is contained alone, or (a) sodium sulfate or potassium sulfate and (b) lithium carbonate are used in combination (a) / (b) with a mass ratio of 1 or more. Ultra-fast hard cement for construction sites with a temperature of less than 13 ° C.
[5] As a curing accelerator, (a) sodium sulfate or potassium sulfate and (b) lithium carbonate are used in combination (a) / (b) at a mass ratio of 0.5 to 2, and the temperature is over 13 ° C. 25. Ultra-fast hard cement for construction sites below ℃.

According to the construction method of the present invention, it is possible to construct mortar or concrete using the optimum ultrafast-hardening cement corresponding to the change in the temperature of the construction site, and it is possible to reduce the amount of lithium carbonate used.

The construction method of mortar or concrete using the ultrafast-hardening cement of the present invention is a construction method in which the hardening accelerator in the ultrafast-hardening cement is changed depending on the construction environment temperature, and is characterized by the following conditions.
(1) In the construction site where the temperature is less than 13 ° C., (a) sodium sulfate or potassium sulfate alone, or (a) sodium sulfate or potassium sulfate and (b) lithium carbonate are used as the curing accelerator (a) / (b). Use ultrafast hard cement used in combination with a mass ratio of 1 or more.
(2) In a construction site where the temperature is above 13 ° C and below 25 ° C, (a) sodium sulfate or potassium sulfate and (b) lithium carbonate are used as a curing accelerator at a mass ratio of (a) / (b) of 0.5 to 2. Use the combined ultrafast hard cement.
(3) In a construction site where the temperature exceeds 25 ° C., (b) ultrafast-hardening cement using lithium carbonate alone is used as a curing accelerator.

The cement used in the construction method of the present invention is an ultrafast-hardening cement containing a hardening accelerator. Examples of the ultrafast-hardening cement include Irwin-based ultrafast-hardening cement, calcium fluoroaluminate-based ultrafast-hardening cement, calcium sulfoluminate-based ultrafast-hardening cement, and calcium-aluminate-based ultrafast-hardening cement. Of these, Irwin-based ultrafast-hardening cement or calcium fluoroaluminate-based ultrafast-hardening cement is preferable, and Irwin-based ultrafast-hardening cement is more preferable.
Here, the calcium fluoroaluminate-based ultrafast-hardening cement rapidly uses compounds, solid solutions, vitreous substances, or mixtures thereof containing _{C 11} A ₇ · CaF ₂ (11 CaO · _{7 Al 2} O ₃ · CaF _{2) as a main component.} It is a cement used as a hard component. The Irwin system than rapid hardening cement is a cement and Irwin _{(3CaO · 3Al 2 O 3 ·} CaSO 4) a compound whose main component, solid solution, glassy material or fast-curing component mixtures thereof. In addition, gypsum, a high-performance water reducing agent, a setting retarder, slaked lime, and a pulverizing aid can be further added to the ultrafast hard cement.

The mortar used in the present invention is a mixture of the ultrafast-hardened cement with an aggregate, and the concrete is a mixture of the ultrafast-hardened cement with an aggregate and hardened. As the aggregate, fine aggregate and / or coarse aggregate is used. Examples of the fine aggregate include river sand, sea sand, mountain sand, crushed sand or a mixture thereof, and examples of the coarse aggregate include river gravel, sea gravel, crushed stone or a mixture thereof. The construction method of these mortars or concretes is carried out by kneading ultrafast-hardening cement, water and aggregate as usual, and then spraying or filling the construction site and then curing.

In the construction method of the present invention, in a construction site where the temperature is less than 13 ° C., that is, in a cold region, (a) sodium sulfate or potassium sulfate is blended alone as a curing accelerator, or (a) sodium sulfate or potassium sulfate is combined with (a). b) Use ultrafast hard cement in which lithium carbonate is used in combination (a) / (b) with a mass ratio of 1 or more. This ultrafast-hardening cement is useful as an ultrafast-hardening cement for construction sites having a temperature of less than 13 ° C.
The test of the construction site having a temperature of less than 13 ° C. can be performed by measuring the mortar flow value, the slump value, and the compressive strength for 3 hours in a 5 ° C. environment.

In an environment where the temperature is less than 13 ° C., (a) sodium sulfate or potassium sulfate alone is blended, or (a) sodium sulfate or potassium sulfate and (b) lithium carbonate are blended, as compared with the case where lithium carbonate is blended alone. When the compounding mass ratio [(a) / (b)] is 1 or more, the early strength development is remarkably improved and lithium carbonate is further reduced. Here, of sodium sulfate and potassium sulfate, potassium sulfate is economically preferable. The early strength development can be confirmed by the compressive strength of concrete at 3 hours of age being 24 Mpa or more.
Of these, it is preferable that (a) sodium sulfate or potassium sulfate and (b) lithium carbonate are used in combination, and (a) / (b) is 1 or more, and (a) / (b) is 1 to 5. It is more preferable that there is, and it is more preferable that (a) / (b) is 1 or 2. In addition, since lithium carbonate is most reduced, it is particularly preferable to add sodium sulfate or potassium sulfate alone.
When lithium carbonate is used alone, the amount of substitution when substituting sodium sulfate or potassium sulfate is 0.3 times or more the amount of reduction of lithium carbonate. It is preferable to add 0.5 times or more, more preferably.

Here, the total amount of the curing accelerator used is preferably 0.3 to 2 parts by mass, more preferably 0.4 to 1.5 parts by mass, and 0.5 to 1 part by mass with respect to 100 parts by mass of the ultrafast-hardened cement. The portion is more preferable.

In the construction method of the present invention, in a construction site having a temperature of more than 13 ° C. and 25 ° C. or lower, that is, in a normal environment, (a) sodium sulfate or potassium sulfate and (b) lithium carbonate are used as a curing accelerator (a) /. (B) Use ultrafast hard cement used in combination with a mass ratio of 0.5 to 2. This ultrafast-hardening cement is useful as an ultrafast-hardening cement for construction sites having a temperature of more than 13 ° C. and a temperature of 25 ° C. or lower.

In an environment where the temperature is higher than 13 ° C and 25 ° C or lower, (a) sodium sulfate or potassium sulfate and (b) lithium carbonate are used in combination as compared with the case where lithium carbonate is blended alone, and the blending mass ratio [(a)). When / (b)] is 0.5 to 2, the early strength development is remarkably improved. If the compounding mass ratio exceeds 2, the fluidity may decrease. When the compounding mass ratio is less than 0.5, the amount of lithium carbonate reduced is small. If the compounding mass ratio exceeds 2, the fluidity may decrease. Here, of sodium sulfate and potassium sulfate, potassium sulfate is economically preferable. The early strength development can be confirmed by the compressive strength at 3 hours of age being 24 Mpa or more.
Of these, it is preferable that (a) sodium sulfate or potassium sulfate and (b) lithium carbonate are used in combination, and (a) / (b) is 0.5 to 2, and (a) / (b) is 0. It is more preferably .6 to 1.5, and further preferably 0.8 to 1.2 in (a) / (b).
When lithium carbonate is used alone, the amount of substitution when substituting sodium sulfate or potassium sulfate is preferably one or more times the amount of reduction of lithium carbonate, and it is preferable to add sodium sulfate or potassium sulfate. It is more preferable to add 1.5 times or more.
The test of the construction site having a temperature of more than 13 ° C. and 25 ° C. or lower can be performed by measuring the mortar, concrete, mortar flow value, slump value, and compression strength for 3 hours in an environment of 20 ° C.

Here, the total amount of the curing accelerator is preferably from 0.5 to 2 parts by mass with respect to ultra-rapid setting cement 100 parts by weight, more preferably from 0.7 to 1.5 parts by weight, 0.8 to 1. 2 parts by mass is more preferable.

In the construction method of the present invention, in a construction site where the temperature exceeds 25 ° C., (b) ultrafast hard cement using lithium carbonate alone is used as a curing accelerator. Here, the blending amount of lithium carbonate is preferably 0.4 to 2 parts by mass, more preferably 0.5 to 1.5 parts by mass, and 0.7 to 1.2 parts by mass with respect to 100 parts by mass of the ultrafast hard cement. The portion is more preferable.
The test of the construction site having a temperature of more than 25 ° C. can be performed by measuring the mortar, concrete, mortar flow value, slump value, and compression strength for 3 hours in an environment of 30 ° C.

In the construction method of the present invention, the water / cement ratio can be kneaded in the range of 35% to 55% for construction. Examples of the construction site include thickening and reinforcing the upper surface of the floor slab of an expressway and repairing the cross section of pavement concrete.
Sodium sulphate, potassium sulphate, and lithium carbonate are mixed and crushed with raw materials when producing quick-hardening cement, mixed with quick-hardening cement, mixed when kneading concrete, and water-soluble in concrete kneading water. It may be finally mixed with concrete.

(1) Composition of Super Jet Cement (Taiheiyo Cement)

Manufacture of Irwin Clinker
Type II anhydrous gypsum, bauxite, and limestone were mixed to the chemical composition shown in Table 1 and calcined at about 1350 ° C. to produce a clinker.

Manufacture of Irwin-based quick-hardening cement 125 parts by mass of early-strength Portland cement clinker and 25 parts by mass of anhydrous gypsum were mixed with 100 parts by mass of Erwin clinker and then crushed to obtain a fast- ^{hardening cement with a brain specific surface area of 4760 cm 2 / g.} Made.

(2) Composition of Jet Cement (Sumitomo Osaka Cement Co., Ltd.) Jet cement (calcium fluoroaluminate type) manufactured by Sumitomo Osaka Cement Co., Ltd., which has already been mixed with lithium carbonate, was used.

(3) Mortal test water 0.275 kg, ultra-fast-hardening cement 0.7212 kg, Yuki fine aggregate 1.2838 kg, high-performance water reducing agent (trade name Mighty 150 [registered trademark], manufactured by Kao Co., Ltd.), 100 mass of fast-hardening cement C x 0.75% in the 5 ° C test, C x 1.9% in the 20 ° C test, and a setting retarder (cement acid, reagent first grade, manufactured by Kanto Chemical Co., Inc., and heptonic acid, reagent 1). Class, equal amount mixed by Kanto Chemical Co., Inc.) with 100 parts by mass of fast-hardening cement, C x 0.45% in 5 ° C test, C x 0.7% in 20 ° C test, and Tables 3-5. The hardening accelerator shown was kneaded with 1 L of Hobart Mixer for 3 minutes, and the flow immediately after kneading and for 30 minutes was measured according to JIS-R5201 (physical test method for cement).
Separately, it was placed in a mold having a diameter of 10 and a height of 20 cm. Further, the mold was removed 3 hours after the water injection (3 hours of material age), and the compressive strength of the specimen was measured immediately after the mold removal.

(4) Concrete test The composition is shown in Table 2.

(Kneading method, test method)
Next, water 4.5 kg, ultrafast hard cement 12.0 kg, fine aggregate from Yuki 21.36 kg, hard sand rock crushed stone from Sakuragawa (Nos. 5 and 6) 16.89 kg each, high-performance water reducing agent (trade name Mighty 150) [Registered trademark], Kao Co., Ltd.), and setting retarder (citric acid, reagent first grade, Kanto Chemical Co., Ltd., and heptonic acid, reagent first grade, Kanto Chemical Co., Ltd. equal amount mixture) are shown in Tables 6-8. The amount shown, and the curing accelerator shown in Tables 6 to 8 are kneaded with a pan-type mixer 55L for 3 minutes, and immediately after kneading and 10 minutes, 20 minutes, 30 minutes, and 40 minutes, slump is applied to JIS-A1101 (concrete). The measurement was performed according to the slump test method). The target slump is 12 cm ± 2.5 cm immediately after kneading at 5 ° C, 1 to 3 cm after 30 minutes, 12 cm ± 2.5 cm immediately after kneading at 20 ° C and 30 ° C, and 1 to 40 minutes after kneading. It was set to 3 cm.
Separately, it was placed in a mold having a diameter of 10 and a height of 20 cm. Further, the mold was removed 3 hours after the water injection (3 hours of material age), and the compressive strength of the specimen was measured immediately after the mold removal. ^{The target compressive strength was set to 24 N / mm 2 in} 3 hours so as to satisfy all the design and construction manuals for the top surface thickening method of the Expressway Research Institute, the design standards of each expressway company, etc., including the safety factor.

The results are shown in Tables 3 to 8.

When sodium sulfate or potassium sulfate was added according to the mortar test shown in Table 3, early strength development was improved, and the additive alternative to lithium carbonate was sodium sulfate or potassium sulfate, and the strength was rather lowered with salts other than the above. rice field. From Table 4, it was confirmed that the early strength development was improved by adding sodium sulfate even in the calcium fluoroaluminate-based quick-hardening cement. Further, from Table 5, it was confirmed that the early strength development was improved even in the environment of 20 ° C.

In the concrete actually used for the structure, as shown in Table 6, in the environment of 5 ° C., sodium sulfate alone was superior to lithium carbonate alone in the early strength development. In addition, sodium sulfate can be replaced up to the total amount of lithium carbonate, and a smaller amount of sodium sulfate can be added to obtain concrete that satisfies fluidity, pot life, and strength.
From Table 7, it was confirmed that the early strength development was improved even in the environment of 20 ° C.
Compared with (b) lithium carbonate alone, the addition of (a) sodium sulfate improved the early strength development. The compounding ratios (a) / (b) were good at 1 to 2. Further, when lithium carbonate was replaced with sodium sulfate, concrete satisfying fluidity and strength could be obtained by adding sodium sulfate in an amount equal to or more than the reduced amount of lithium carbonate.

From Table 8, in the environment of 30 ° C., the case of sodium sulfate alone is superior to the case of sodium sulfate alone in the early strength development, but even if the amount of the water reducing agent added is adjusted, the concrete that satisfies the pot life can be obtained. I couldn't get it.

Claims (2)

A method of constructing mortar or concrete using ultrafast-hardening cement containing a hardening accelerator, which measures the temperature at the time of construction at the construction site and changes the hardening accelerator in the ultrafast-hardening cement according to the temperature at the construction site. It is a method, and the super fast-hardening cement is Irwin-based super-fast-hardening cement or calcium fluoroaluminate-based super-fast-hardening cement.
(1) At a construction site where the temperature is less than 13 ° C., (a) sodium sulfate or potassium sulfate alone, or (a) sodium sulfate or potassium sulfate and (b) lithium carbonate are used as curing accelerators (a) / (b). ) Using ultrafast hard cement with a mass ratio of 1 or more,
(2) At construction sites where the temperature is above 13 ° C and below 25 ° C, (a) sodium sulfate or potassium sulfate and (b) lithium carbonate are used as curing accelerators at a mass ratio of (a) / (b) of 0.5 to 2. Using the combined ultra-fast hard cement,
(3) A construction method characterized in that (b) ultrafast-hardening cement using lithium carbonate alone is used as a curing accelerator at a construction site having a temperature of more than 25 ° C. The total amount of hardening accelerator used is 0.3 to 2 parts by mass with respect to 100 parts by mass of ultrafast-hardened cement at a construction site where the temperature is less than 13 ° C, and 100 parts by mass of ultrafast-hardened cement at a construction site where the temperature is above 13 ° C and 25 ° C or less. The construction method according to claim 1 , wherein the amount is 0.5 to 2 parts by mass with respect to 100 parts by mass, and 0.4 to 2 parts by mass with respect to 100 parts by mass of ultrafast-hardened cement at a construction site where the temperature exceeds 25 ° C.