JP2005225706A - Pc grout admixture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PC (prestressed concrete) grout admixture which can reduce the amount of soluble chloride ions of a PC grout while using a cement adapted to the new JIS containing chloride ions possible to cause corrosion of steel material, more than the conventional cements, and a durability equivalent to or more than the conventional ones, can be secured. <P>SOLUTION: For the PC grout admixture, a zeolite is used combinedly with an admixture, which has been used heretofore. By constituting like this, the zeolite reacts with a cement hydrate to produce a Friedel's salt being a calcium-aluminium-based hydrate having chloride ions in its structure. By this reaction, the soluble chloride ions are reduced by fixing a part of the soluble ions in a hardened PC grout. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an admixture for PC grout mainly used for PC grout.

(Technical background)
Most of the waste and by-products discharged from the production and recycling processes of industrial products and daily human life are incinerated or landfilled. However, due to recent tightening of landfill sites and stricter regulations on waste, large-scale landfill disposal cannot be expected in the future.

  For this reason, active use of waste and by-products is desired, and the cement industry contributes to the creation of a recycling-oriented society by using various waste and by-products as raw materials in the cement manufacturing process. .

  Incidentally, one of the deterioration of concrete structures is corrosion of steel materials involving chlorides. In order to prevent this, products such as chloride content in concrete (JIS A 5308; revised in 1998) and chloride ions of Portland cement (JIS R 5210; revised in 1997) are made up of products and their components. The amount of chloride allowed is specified for each material.

  As described above, chlorides are harmful to concrete structures. However, various wastes and by-products used in the cement manufacturing process may contain harmful chlorides. .

Under such circumstances, the “Society on the Regulation of Total Salt Content in Concrete and Alkali-Aggregate Reaction Suppression” was established in October 2001, and the cement industry has become more involved in building a recycling society In order to contribute, “the concrete chloride total amount regulation value that can ensure the durability of the concrete: within the range that satisfies 0.3 kg / m ³ , the chloride content regulation value in the cement: 200 ppm (0.02 %) Is suggested to the Ministry of Land, Infrastructure, Transport and Tourism.

  In December 2002, the Ministry of Land, Infrastructure, Transport and Tourism, in the direct control of the Ministry of Land, Infrastructure, Transport and Tourism, reduced the regulation value of the chloride content of ordinary Portland cement from 200 ppm (0.02%) or less to 350 ppm (0.035%). The JIS standard was revised in November 2003, informing the parties concerned that it would be relaxed as follows.

(Conventional technology)
By the way, a prestressed concrete structure in which a compressive stress is applied to concrete using a PC steel wire is adopted for a bridge or the like.

  As is well known, this is a high strength steel material called PC steel wire that is tensioned and fixed to give compressive force to concrete, but the hole through which the PC steel wire is inserted (in detail) Is poured into a hole in the sheath) and fluidized PC grout such as cement milk is solidified to be integrated as a concrete structure.

  In this way, prestressed concrete is a concrete structure, but it is a mixture of cement, water and PC grout admixture with a so-called concrete part that is a mixture of aggregate such as sand and gravel and water. There is a PC grout part.

  The latter admixture for PC grout is used to prevent bleeding of PC grout and to improve (stabilize) filling and fluidity. It is indispensable for filling the scale hole with PC grout without gaps.

Prior art of such an admixture for PC grout includes, for example, an expansion material produced by heat-treating a composition containing a CaO raw material, an Al ₂ O ₃ raw material, and a CaSO ₄ raw material, a carboxyl group and a polyalkylene in the side chain. There are those containing a polycarboxylic acid-based polymer having an oxide structure, and according to this configuration, for example, even in use conditions where the grout material temperature exceeds 30 ° C., such as in summer, it is necessary for construction It is said that a sufficient grout effect can be obtained for a period of time (see, for example, Patent Document 1).
JP 11-79816 A (first page)

By the way, as described above, the amount of chloride ions of cement, that is, ordinary Portland cement was relaxed from 200 ppm (0.02%) or less to 350 ppm (0.035%) or less. The total regulation value of chloride ions as concrete mixed with aggregate, 0.3 kg / m ³ is the same as before.

This means that in PC grouts that do not require aggregate and the unit cement amount is large, the total amount of chloride ions per unit volume will simply rise, and there is concern about the durability as PC grout, In extreme cases, there are cases where the total amount of chloride ions in the cured PC grout exceeds 0.3 kg / m ³ .

  Therefore, in order to solve such a problem, the present invention can be used in combination with the above-mentioned PC grout admixture, and is kneaded using a deregulated cement containing more chloride ions. An object of the present invention is to provide an admixture capable of reducing the amount of soluble chloride ions after curing of PC grout and ensuring the durability as usual.

  Chlorides contained in hardened concrete are divided into soluble chloride ions and chlorides fixed as Friedel's salt, a kind of cement hydrate. Among these, it is soluble chloride ions that are involved in the corrosion of steel materials, and if this is reduced, the possibility of steel material corrosion caused by chloride ions can be reduced.

  Therefore, the present inventors have conducted intensive research on substances that have a remarkable effect in reducing soluble chloride ions, and have confirmed that zeolite is extremely effective.

That is, the PC grout admixture according to claim 1 is characterized by comprising zeolite.
The admixture for PC grout according to claim 2 is characterized in that, in claim 1, the zeolite is composed of synthetic, artificial, or natural zeolite.

Thus, the following effects are produced by combining zeolite with a well-known conventional PC grout admixture.
That is, the total amount of chloride ions contained in ordinary Portland cement does not change, but the amount of soluble chloride ions in the hardened PC grout can be reduced by utilizing and exclusively using the attributes of this zeolite.

That is, zeolite reacts with cement hydrate to produce Friedel's salt, a calcium-aluminum hydrate with chloride ions in the structure. This reaction reduces the soluble chloride ions by immobilizing some of the soluble chloride ions in the cured PC grout.
The zeolite described above is preferably in the form of powder, and the amount added is preferably about 1% in terms of the weight ratio of the amount of cement used.

As described above, since the admixture for PC grout according to the present invention reduces soluble chloride ions contained in the PC grout, the admixture can be used even in PC grout containing a large amount of chloride. The possibility of steel corrosion due to chloride ions can be reduced, and a PC grout with fluidity and durability ensured according to current standards can be produced.
Moreover, as a combination method of zeolite, since zeolite is simply added to the conventional PC grout admixture, it can be produced without significant improvement in the production process and production apparatus. It is harmless to the human body and does not require any special treatment during handling.

  In addition to naturally occurring zeolites, there are synthetic and artificial ones. Naturally occurring products contain sodium, an alkali metal element, as an exchangeable cation. Sodium ion may cause deterioration due to alkali-aggregate reaction, and may lead to decrease in durability of hardened PC grout. Calcium type in which more than half of exchangeable cations are replaced with calcium ions It is preferable to use a synthetic or artificial zeolite of calcium type in which 70% or more of the exchangeable cations are replaced with calcium ions. Furthermore, since the synthetic or artificial zeolite is a powder, it can be easily obtained as well as the trouble of grinding like a natural zeolite.

Here, an example of this embodiment will be described.
The PC grout admixture according to the present embodiment is approximately half as interchangeable as a non-expanding conventional PC grout admixture in which a thickener is blended based on a melamine-based high-performance water reducing agent. It consists of a combination of synthetic zeolite powders whose main components are silicon and aluminum by replacing cations with calcium.

  First, the effect of synthetic zeolite is confirmed. Table 1 and FIG. 1 show the measurement results of the amount of soluble chloride ions of samples to which synthetic zeolite was added at various levels.

The sample used for the test was prepared with a unit cement amount of 1300 kg / m ³ and a water cement ratio of 45%.

Lot. No. Reference numeral 1 is a sample in which the amount of contained chloride ions is adjusted to the total amount of chloride ions in PC grout, which is 0.3 kg / m ³ . When a sample with a unit cement amount of 1300 kg / m ³ is prepared using ordinary Portland cement containing 350 ppm of chloride ions, the total amount of chloride ions contained is 0.5 kg / m ³ . No. The samples after 2 are samples in which the amount of chloride ions contained using sodium chloride was adjusted to about 0.5 kg / m ³ .

  Lot. No. 3-6 are No.3. The synthetic zeolite powder in Fig. 2 is 0.5% (Lot. No. 3), 1.0% (Lot. No. 4), 2.0% (Lot. , 3.0% (Lot. No. 6).

  Lot. No. 1 and No. The total chloride ion amounts of 2 are 0.234 kg and 0.4004 kg, respectively. On the other hand, as shown in Table 1, the amount of soluble chloride ions is No. 1: 0.024 kg, No. 1 2: The amount is about 1/10 of 0.041 kg. The sample simulating PC grout has a very high unit cement content, indicating that a large amount of chloride ions are fixed due to cement hydration.

  Lot. No. 3 is a sample to which 0.5% of synthetic zeolite powder is added based on the cement weight. The amount of soluble chloride ions was 0.041 kg, and there was hardly any decrease in the amount of soluble chloride ions due to the addition of zeolite. On the other hand, Lot. No. In No. 4, the amount of soluble chloride ions was 0.012 kg, which was reduced to about 3 to 1/4. As a result, even when a cement containing 350 ppm of chloride ions was used, the amount of soluble chloride ions was increased by adding 1% of the synthetic zeolite zeolite weight. No. It became clear that it became 1 or less.

  Lot with zeolite added at 2% or more of cement weight. In Nos. 5 and 6, the amount of soluble chloride ions was greatly reduced. A graph of the experimental results is shown in FIG.

  Thus, it was confirmed that the soluble chloride ion was remarkably reduced by combining the zeolite powder, and at least the synthetic zeolite powder was configured to be 1.0% or more by weight with respect to the cement amount. As a result, it was confirmed that the PC grout admixture was excellent in rust prevention.

  Next, the effect of the addition of synthetic zeolite powder on the fluidity of PC grout was examined. Two types of specimens were used: a grout using only a conventional PC grout admixture (Case 1) and a grout (Case 2) to which zeolite powder was further added. Table 2 shows the material ratio of each grout, and Table 3 shows the experimental results.

  In Case 2, the conventional PC grout admixture was added 1% of the cement weight, and the synthetic zeolite powder was added 1% of the cement weight.

  The fluidity was evaluated based on the funnel flow time using a JP funnel (JSCE-F531). In addition, bleeding water and expansion rate were evaluated by a method using a polyethylene bag (JSCE-F532).

The results of examining the influence of the addition of synthetic zeolite powder on fluidity and the like are shown below.
First, regarding fluidity, Case 1 is 11.1 seconds, Case 2 is 12.9 seconds, and the grout of Case 2 is slightly higher in viscosity.

Although it was the presence or absence of generation | occurrence | production of bleeding water, the sign was not visually recognized in both, and the favorable result was obtained.
Regarding the expansion rate, it was confirmed that the grout of Case 2 was slightly expanded.
The compressive strength showed a tendency that Case 2 to which the synthetic zeolite powder was added was slightly increased.

  From the above, it was confirmed that there was no problem in actual application even if synthetic zeolite powder was added.

As described above, the PC grout admixture according to the present embodiment reduces the possibility of steel corrosion by reducing soluble chloride ions without impairing workability even in cement containing a large amount of chloride ions. It is possible.
Note that the amount of soluble chloride ions can be reduced by combining other cements such as blast furnace slag cement with synthetic zeolite powder.

  As mentioned above, although the admixture for PC grout concerning this Embodiment was demonstrated, embodiment mentioned above shows an example of suitable embodiment of this invention, and this invention is in above-described embodiment. The present invention is not limited, and various modifications can be made without departing from the scope of the invention.

FIG. 3 is a diagram showing the amount of soluble chloride ions with the zeolite content as a parameter.

Claims (2)

  An admixture for PC grout, comprising zeolite. The admixture for PC grout according to claim 1, wherein the zeolite comprises synthetic, artificial, or natural zeolite.

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