KR20050032358A - Early strengthening type cement composition to restore surface and not separated underwater - Google Patents

Abstract

Provided is an early strength type cement composition which has superior underwater non-separation property, high fluidity to fill in fine pores and good early strength development and thus is useful for placing underwater concretes and restoring an underwater concrete structure. The early strength type cement composition for surface restoration and underwater non-separation is produced by mixing 0.2 to 2.0 parts by weight of a cellulose ether-based thickener, 0.3 to 2.5 parts by weight of a super plasticizer containing polycarbonate as a main component and 0 to 1.0 parts by weight of an anti-foaming agent, each being based on 100 parts by weight of a calcium sulfoaluminate-based cement with a fineness of 4,000 to 6,000 cm^2/g. The high-early strength type cement composition may further comprise 1 to 50 parts by weight of a filling material selected from fine powdered limestone, fly ash, silica fume and metakaolin alone or in a mixed form.

Description

Early strengthening type cement composition to restore surface and not separated underwater}

The present invention relates to a rough steel-type underwater fire separation cross-sectional recovery cement composition, and more particularly, to repair underwater concrete structures by implementing the underwater fire separation characteristics, fluidity to fill even micropores, and early strength development at the same time, It is suitable for use in underwater mortar or concrete pouring.

Recently, the demand and construction of underwater concrete structures are increasing rapidly according to the trend of marine development, and the domestic conditions are surrounded by the sea on three sides, and there are many projects related to the sea such as ports, marine civil engineering, and pedestrian bridges. There is a lot of construction going on.

As such, for the construction of underwater concrete structures, sand and aggregates should not be separated from the cement applied to the concrete during underwater work, should be able to express the desired level of strength after curing, and fluidity that can fill even the fine pores of the concrete structure. In order to increase the viscosity of the cement in the composition of the cement was used as a water-insoluble immiscible admixture in the cellulose ether and acrylic water-soluble polymer admixture.

Known cellulose ether-based water-insoluble admixtures include nonionic methyl cellulose (MC), ethyl cellulose (EC), hydroxy ethyl cellulose (HEC), hydroxy propyl cellulose (HPC), and hydroxy propyl methyl cellulose (HPMC). ), Hydroxyethyl methyl cellulose (HEMC), hydroxy ethyl methyl cellulose (HEEC) and ionic carboxymethyl cellulose (CMC), and the acrylic dissociable admixtures include polyacrylamide (PAA), sodium acrylate, polyacrylamide And partial hydrolyzates. Polyethylene oxide (PEO), polyvinyl alcohol (PVA), and the like are also used.

These thickeners can improve the non-isolating properties in water, but have side effects such as fluidity decrease, initial strength decrease, bubble generation, etc., and have tried to increase the strength by using antifoaming agent or adding alkali metal salt as hardening accelerator. Or calcined alum was used, and some of the cellulose ethers were partially substituted with sulfonic acid bases to prevent cure delays.

However, this method alone has disadvantages in terms of construction, such as delayed condensation of mortar and concrete, early strength drop rate, difficulty in securing workability, securing watertight concrete, and inevitably have limitations in enhancing long-term strength.

In particular, the early strength development is important when renovating an underwater concrete structure that has already been constructed, but the existing underwater unseparable cement composition has been developed in accordance with the underwater concrete placement, which has the disadvantage of inferior early strength development.

The present invention has been proposed in view of the above-mentioned problems, and includes a cellulose ester-based or acrylic viscosity-increasing agent for preventing material separation in water, calcium sulfo aluminate-based cement having a powder of 4,000 to 6,000 cm 2 / g, and A polycarboxylic acid-based dispersant for improving the dispersing characteristics, an antifoaming agent for removing bubbles contained in the slurry, and various fillers used for physical improvement can be mixed in an appropriate amount to fill in water disintegration characteristics and even micropores. It is an object of the present invention to provide a crude steel-type underwater separation separation recovery cement composition capable of realizing fluidity and early strength development.

Hereinafter, the present invention will be described in detail according to the present embodiment.

The crude steel-type underwater fire-free cross-sectional recovery cement composition according to the present invention is filled with active or inactive powders such as limestone, fly ash, silica fume, metakaolin, etc., based on 100 parts by weight of calcium sulfo aluminate cement having a powder degree of 4,000 to 6,000 cm 2 / g. 0 to 50 parts by weight of the material, 0.2 to 2.0 parts by weight of cellulose ether thickener having a viscosity of 8,000 to 50,000 cps in a 2% solution of 20 ° C aqueous solution, 0.3 to 2.5 parts by weight of a high softening agent mainly containing a polycarboxylic acid, and an antifoaming agent 0 It is made by mixing -1.0 parts by weight, and is used by mixing an appropriate amount of sand and gravel.

In more detail, the crude steel-type underwater fire-free sectional recovery cement composition according to the present invention is calcium sulfo aluminate-based cement, limestone fine powder, fly ash as a filler, silica fume, metakaolin, cellulose ether thickener, polycar It consists of an acid-based high fluidizing agent, an antifoaming agent, etc. The calcium sulfo aluminate cement used in the present invention not only has excellent initial strength but also excellent durability by securing high strength, and is hydrated by ethrinzite (C ₃ A It is well known that 3CaSO ₄ 32H ₂ O) is a stable compound which mainly produces hydrates. The calcium sulfo aluminate-based cement can be used as a water-insoluble separation admixture, and compared to alkali metal salts or anhydrous or calcined alum, which are added to compensate for its shortcomings, there is no gas condensation phenomenon, and durability is reduced due to initial strength enhancement. It is stable and has no side effects. In order to use it as a water-disintegrated cross-sectional recovery cement composition, it is preferable to use it by pulverizing it with a specific surface area of 4,000∼6,000㎠ / g, and considering limestone (CaCO) ₃ content of 95wt% or more) It is good to use fine powder (more than 4,000cm2 / g of powder) or to substitute fly ash. In addition, it is possible to secure excellent quality by using metakaolin, silica fume, etc. for the purpose of improving the physical properties only.

In the case of limestone, not only the limestone can contribute to the increase of durability by filling the pores, but also the initial strength can be secured by the production of mono carbo aluminate or tricarbo aluminate hydrate. In addition, fly ash, silica fume, metakaolin and the like can produce a calcium aluminate or calcium silicate hydrate in addition to the pore filling effect to create a cured product excellent in the initial and long-term strength expression. In particular, these mixtures are needed to improve the function of the material that can help to increase the bending strength. In addition, when the structural surface cross-sectional recovery portion is massive, it may also play an important function in reducing the heat of hydration.

In the present invention, the thickener used to impart separation resistance in water can be used both cellulose and acrylic, and as the fluidizing agent, naphthalene sulfonate, melamine sulfonic acid, ligline sulfonate can be used, but calcium sulfo aluminate It is most advantageous to use a polycarboxylic acid-based high performance sensitizer in view of its properties. If the amount is less than 0.2wt%, the fluidity decrease occurs, so it is impossible to work, and when it is used more than 2.5wt%, it is uneconomical. In addition, the defoaming effect does not occur when using more than 1.0wt%.

In addition, the air entrainer can be used in parallel at the place where the structure is exposed to the air after concrete pouring and is likely to undergo a freeze-thawing action.

Below is a compressive strength test value of the cement composition and the comparative example prepared according to the present invention.

Table 1 shows the measured compressive strength of mortar prepared by mixing a common ordinary Portland cement and a crude steel type underwater fired cross-sectional recovery cement according to the present invention, respectively.

TABLE 1

                                                              22.5% water ratio

division Compound (parts by weight) Flow (mm) Compressive strength (kgf / ㎠) Ordinary cement Crude steel underwater fire separation cement sand High Performance Supervisor Underwater fire separation admixture 1 day 7 days 28 days No. 3 No. 5 No. 6 Plain 500 - 150 200 150 - - 240 70 198 240 Comparative Example 1 500 - 150 200 150 Polycarboxylic acid system 2.25 220 65 173 217 Example 1 - 500 150 200 150 Polycarboxylic acid system 2.25 225 126 235 336

As shown in Table 1, it can be seen that in the comparative example 1 using the in-water separation admixture in the same formulation, a significant decrease in strength occurs, and in Example 1 according to the present invention using the crude steel-in-water separation cement, 1 day, 7 days and The 28-day strength is usually higher than the mortar compressive strength of the cement alone (plane), it can be seen that the daily strength is expressed more than 50 higher than the plain.

In addition, the compressive strengths of the poly sulfonic aluminate cements using polycarboxylic acids (Example 1), the naphthalene series (Comparative Example 2) and the melamine series (Comparative Example 3) The measurement is shown in Table 2.

TABLE 2

                                                      22.5% water ratio

division Compound (parts by weight) Flow (mm) Compressive strength (kgf / ㎠) Crude Steel Underwater Separation Cement sand High Performance Supervisor Underwater fire separation admixture 1 day 7 days 28 days No. 3 No. 5 No. 6 Example 1 500 150 200 150 Polycarboxylic acid system 2.25 225 126 235 336 Comparative Example 2 500 150 200 150 Naphthalene system 2.25 222 102 189 252 Comparative Example 3 500 150 200 150 Melamine 2.25 220 107 198 265

As shown in Table 2, Example 1 according to the present invention using a polycarboxylic acid system as a high-performance sensitizer shows a significantly higher compressive strength value in early strength and long-term strength than the comparative examples using a naphthalene-based or melamine-based. Can be.

In addition, after the crude steel-type underwater fire separation cross-sectional recovery cement composition prepared according to the present invention to produce a water-in-separated concrete test body (Example 2) in the mixing ratio as shown in Table 3 in the air, the compressive strength ratio, pH, Slump flow, the amount of suspended solids was measured, and the measured results are shown in Table 4.

Here, the evaluation method for the characteristics of cement composition for underwater construction has not been defined in Korea to date, but the "Quality Standard (Draft) of Water-incomparable Admixtures for Concrete", which is a standard set by the Korean Society of Civil Engineers, 1995, was proposed. In the present invention, the main experiment was performed using this, and the experimental method is as follows.

Slump Flow:

Remove the slump cone after filling it with concrete in the concrete slump cone. After leaving for 5 minutes, the spread diameter of the concrete is measured and two points are averaged.

Compressive Strength Ratio:

-Fabrication of airborne specimens: A mold with a diameter of 10cm × 20cm was used, and the manufacturing method is the same as that of the existing concrete strength manufacturing method (KS L 2405).

-Preparation of underwater specimens: Soak a mold for strength measurement in a water tank with a depth of 30 cm. The distance between the center of the mold and the water surface is always kept 20 cm.

The concrete is divided into 10 equal parts on the surface of the water and allowed to stand for 15 minutes to be filled by self-weight without any commitment. After 15 minutes, remove the mold and tap the left and right sides with a rubber mallet two or three times. The curing method is the same as the existing concrete curing method.

-Strength measurement is measured as the ratio of compressive strength in water and underwater after measuring the compressive strength for 7,28 days for specimens prepared in air and in water respectively.

-Amount of suspended substance:

Fill a 1000㏄ beaker (outer diameter 100mm, height 150mm) with 800㏄ of water, and divide the concrete into 500g more than 10 equal parts and leave for 3 minutes. Thereafter, 600 beakers are collected using the dropper to measure suspended matter. At this time, the suspension material is expressed in mg / ℓ.

-pH: Implement according to KS CE 95-02.

TABLE 3

aggregate W / C (%) s / a (%) Unit Usage (kg / ㎥) 25mm stone 50 75.34 water cement sand Pebble Underwater fire separation admixture 215 430 712 945 W × 1.8

TABLE 4

Test Items Amount of Suspension (mg / L) pH Compressive Strength Ratio (%) Slump Flow (cm) 7 days 28 days Example 2 72 11.2 75 79 52.0 Korean Society of Civil Engineers 150 or less 12 or less 60 or more 70 or more 45 or more

As such, as a result of comparing various properties of the concrete for underwater placing with the crude steel-type underwater unsepared cement composition according to the present invention, all evaluation items showed a good result that greatly exceeds the standards of the Korean Society of Civil Engineers, which is a cement according to the present invention. It means that the concrete prepared from the composition has superior effect to the existing water-insoluble cement composition in all aspects such as water-insoluble property as well as fillability, early strength development.

As described above, the present invention is superior in the underwater fire separation properties and filling properties compared to the existing underwater fire separation cement composition, and particularly, it has good early strength expression, so that it can be used for repairing underwater concrete structures as well as underwater concrete structures. It is the most suitable.

Claims (2)

0.2 to 2.0 parts by weight of a cellulose ether thickener, 0.3 to 2.5 parts by weight of a high softening agent containing polycarboxylic acid as a main component and 100 to parts by weight of calcium sulfo aluminate cement having a powder degree of 4,000 to 6,000 cm 2 / g. Crude steel type underwater fire separation cross-sectional recovery cement composition, characterized in that 1.0 parts by weight were mixed. The method of claim 1, A crude steel-type underwater fire-free cross-sectional recovery cement composition, characterized in that it further comprises 1 to 50 parts by weight of selected materials, either alone or in combination, from fine limestone, fly ash, silica fume and metakaolin.