JP6058474B2 - Method for producing a cured geopolymer - Google Patents

Description

  The present invention relates to a method for producing a cured geopolymer, and more particularly to a method for controlling the setting time.

  Conventionally, a geopolymer hardened body is used as a secondary product of concrete such as a sleeper for railways.

  In the cured geopolymer, if an expensive K-based material is used, the setting time can be increased. However, if an inexpensive Na-based material is used, the setting time is short, and the pot life (time available for production) cannot be increased.

  As a solution to this problem, the present inventor has proposed a method of heating the solution. That is, by subjecting a geopolymer precursor obtained by mixing a sodium silicate solution (for example, water glass) and an alkaline solution (sodium hydroxide) to a predetermined temperature or higher and holding it for a predetermined time. It has been proposed to significantly delay the setting start time and ensure a sufficient pot life (see Patent Document 1 below).

That is, in the conventional method for producing a cured geopolymer, as shown in FIG. 5, the powder (FA) 103 such as coal ash is heated in order to prevent the (sodium silicate solution) of the water glass 101 from solidifying. mixed with hydroxyl kana thorium (NaOH) solution 102 to produce the geopolymer cured product.

JP 2012-240852 A

  However, the conventional method for producing a cured geopolymer described above is good when only coal ash (fly ash) is used, but there is a drawback that condensing is accelerated when blast furnace slag is used.

  In view of the above situation, the present invention provides a process in which the silica content is post-added with silica fume powder, so that even in a system utilizing blast furnace slag, the pot life can be increased. It aims at providing the manufacturing method of the geopolymer hardening body which enables manufacture at the industrial level of a polymer hardening body.

In order to achieve the above object, the present invention provides
[1] In the method for producing a cured geopolymer, after stirring sodium hydroxide solution and coal ash / blast furnace slag powder , silica (SiO ₂ ) fine particle powder is used without using a sodium silicate solution as a Si source. By adding the body, the fine particle powder of silica is gradually dissolved, and the setting time is extended and the pot life is ensured as compared with the case where the Na silicate solution is used .

[2] The method for producing a cured geopolymer according to [1] above, wherein the silica fine particle powder which is the silicon content is silica fume (SF).

  [3] The method for producing a cured geopolymer according to [1] or [2], wherein the cured geopolymer is used as a sleeper for a railway.

  According to the present invention, the pot life has heretofore been short and cannot be manufactured. However, the pot life can be increased and the cured geopolymer can be manufactured at low cost. In particular, such a cured geopolymer is robust and inexpensive, and is suitable for use as a railway sleeper.

It is a schematic diagram which shows the manufacturing method of the geopolymer hardening body which shows the Example of this invention. It is a figure which shows the relationship between the heating temperature and time of the sodium silicate solution of FA-GP hardening body, and initial time. It is a characteristic view which shows the first time (minutes) of the conventional method and the post-SF addition method. It is a characteristic view which shows the kneading temperature (degreeC) and compressive strength (MPa) of the conventional method and the post-SF addition method. It is a schematic diagram which shows the manufacturing method of the conventional geopolymer hardening body.

The method for producing a cured geopolymer is to stir the sodium hydroxide solution and coal ash / blast furnace slag powder, and then add silica (SiO ₂ ) fine particle powder without using the sodium silicate solution as the Si source. By doing so, the silica fine particle powder is gradually dissolved, and the setting time is extended as compared with the case where the Na silicate solution is used, and the pot life is ensured.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a schematic diagram showing a method for producing a cured geopolymer according to an embodiment of the present invention.

In the case of a conventional method for producing a cured geopolymer, when blast furnace slag is used, the Ca content of the blast furnace slag reacts to produce C—S—H (calcium silicate hydrate), which condenses. Therefore, in the case of the present invention, powders such as sodium hydroxide (NaOH) 1, coal ash (fly ash , hereinafter referred to as FA ) 2 and blast furnace slag ( hereinafter referred to as BS) 3 are agitated without forming a sodium silicate solution. After that, the silica fume ( hereinafter referred to as “ SF”) [Meiko (trademark) MS610] manufactured by BAFS Co., Ltd.] 4 is gradually dissolved to obtain a setting time and a pot life. To do. The silicon content is not limited to silica fume (SF), and the same fine particle powder (for example, rice husk incineration ash, Tosoh silica NIPSIL, NIPGEL, etc.) may be used.

  Hereinafter, the improvement of the problem at the time of manufacturing a geopolymer cured body will be described in detail.

(1) Development of a method for controlling the setting time by heating the solution When manufacturing a geopolymer (hereinafter referred to as GP) cured body, Na-based JIS No. 1 water glass ( hereinafter referred to as WG), which is less expensive than K-based, is used. Then, the properties before curing may be deteriorated and it may be difficult to put into the mold, and the condensation time is shortened, sometimes congealing during kneading. . For this reason, it was necessary to add an expensive K-based material, but it is important to obtain a sufficient pot life with an inexpensive Na-based material in order to reduce the cost and to put it to practical use. Then, the method of extending the pot life when using Na-type solution was examined. The test method is as follows.

Using the geopolymer paste, the relationship between the heating / time of the sodium silicate solution and the initial time (the time required for condensation to reach a certain hardness) was examined.

  48% NaOH and 2-fold diluted JIS No. WG as test materials were adjusted so that alkali / water (mol) = 0.15 and Si / alkali (mol) = 0.38, and 35-90 ° C. for 5 minutes to A solution obtained by mixing and stirring a solution maintained for 24 hours and JIS type 1 FA (water / powder = 0.41) was used to measure the initial time.

  FIG. 2 is a diagram showing the relationship between the solution temperature of the FA-GP cured body of the sodium silicate solution and the initial time.

As is clear from this figure, the higher the heating temperature and the longer the heating temperature time, the longer the starting time was extended. This is considered to be because not only the temperature of the sodium silicate solution at the time of charging but also the heating time affects the polymerization structure in the sodium silicate solution. In general, the pot life required for producing concrete secondary products at the factory is at least 1 to 2 hours or more. Confirmed to meet. However, although the sodium silicate solution held at a higher temperature was used, it is considered desirable from the viewpoint of workability because the fluidity before curing is improved.

(2) Development of a method for controlling the setting time by post-addition of silica fume (SF) When BS is not used as the active filler in (1) above, a sodium silicate solution (mixed solution of JIS No. WG and NaOH solution) is heated. It was shown that the setting time can be controlled. However, when BS is used, it hardens with a reaction in which calcium-silicate-hydrate (C—S—H) is generated by the alkali stimulation of BS. Therefore, when the solution temperature is raised, condensation of BS occurs. On the contrary, the pot life is shortened. Therefore, a method has been developed in which a silica silicate solution is not used as a Si source, but silica (SiO ₂ ) fine powder is post-added to a Na hydroxide solution at the time of GP production and is gradually dissolved to extend the setting time. The test method is as follows.

  A GP mortar was prepared by a conventional method and post-SF addition, and each GP preparation method was evaluated based on the kneading temperature, start time, and compressive strength. The formulation and curing conditions are shown below.

  The composition is alkali / water (mol) = 0.165, Si / alkali (mol) = 0.350, the powder part is FA 90%, BS 10%, and the powder: fine aggregate ratio is 1: 2. is there. Curing temperature and time were 85 ° C. and 10 hours. Each production procedure is as follows.

  (1) Conventional method: A sodium silicate solution prepared by mixing commercially available JIS No. 1 WG and NaOH solution is charged into a mixture of powder and aggregate to prepare GP mortar.

(2) Post-SF addition method: After mixing the NaOH solution and BS as an active filler, SF is added, and finally aggregate is added to make a GP mortar.

  FIG. 3 is a graph showing the initial time (minutes) of the conventional method and the post-SF addition method, and FIG. 4 is a diagram showing the kneading temperature (° C.) and compressive strength (MPa) characteristics of the conventional method and the post-SF addition method.

As is clear from these figures, it was found that the post-SF addition method has a longer initial use time and a longer pot life than the conventional method. On the other hand, it was found that the compressive strength is affected by the kneading time, and by maintaining the kneading temperature of about 35 ° C., it is possible to obtain the same strength as the conventional method produced using JIS No. 1 WG.

Note that the extension of the initial time is considered to be due to the fact that the dissolution rate of SF is slowed by the fact that FA is dissolved by the NaOH solution at the initial stage of kneading and the pH is lowered. On the other hand, when the kneading temperature is low, it is presumed that the compression strength is lowered because the dissolution of SF does not proceed.

  According to the present invention, when the blast furnace slag is added, the compressive strength increases, so that the same strength can be produced at a low cost. Up to now, the pot life was short and could not be produced. However, according to the present invention, a geopolymer cured product can be produced at low cost.

  In addition, this invention is not limited to the said Example, Based on the meaning of this invention, a various deformation | transformation is possible and these are not excluded from the scope of the present invention.

  The method for producing a cured geopolymer of the present invention is a geopolymer that enables production of a cured geopolymer at an industrial level by enabling a longer pot life even in a system utilizing blast furnace slag. It can be used as a method for producing a cured product.

1 Sodium hydroxide (NaOH)
2 Coal ash (fly ash)
3 Blast furnace slag (BS)
4 Silica fume (SF)

Claims (3)

After stirring the sodium hydroxide solution and the coal ash / blast furnace slag powder , the silica fine particle powder is added by adding the fine particle powder of silica (SiO ₂ ) without using the sodium silicate solution as the Si source. A method for producing a cured geopolymer, characterized in that the body is gradually dissolved and the setting time is extended more than when the sodium silicate solution is used, thereby ensuring a pot life . 2. The method for producing a cured geopolymer according to claim 1, wherein the silica fine particle powder that is the silicon content is silica fume (SF). 3.   The method for producing a cured geopolymer according to claim 1 or 2, wherein the cured geopolymer is used as a railroad sleeper.

Images