JP6789131B2 - Construction method of cast-in-place geopolymer cured product - Google Patents

Description

The present invention relates to a method for constructing a cast-in-place geopolymer cured product for curing a cast-in-place geopolymer composition to construct a cast-in-place geopolymer cured product.

Conventionally, as shown in Patent Document 1, fillers such as fly ash and blast furnace slag fine powder and alkaline activators such as water glass are mixed as concrete having higher acid resistance and heat resistance than ordinary cement concrete. Cement-free concrete is produced using geopolymer technology, which is then shrink-polymerized. Since this technology can contribute to the reduction of CO ₂ emissions and the effective utilization of industrial waste, various utilization technologies are being studied in the construction field.

When geopolymer concrete using these geopolymer technologies is cured at room temperature in the initial stage during the curing period, the polycondensation reaction is slow and the compressive strength is not sufficiently developed. Therefore, the geopolymer concrete is generally cured while being heated. On the other hand, heating over the entire curing period is not preferable because it easily induces evaporation of water and causes cracks due to drying shrinkage. As described above, since geopolymer concrete is complicated to handle during the curing period, most of its usage forms are limited to use as precast members manufactured by steam curing in factories where the curing period can be easily managed.

Under such circumstances, a curing sheet for cold concrete is known as an equipment capable of heating and curing concrete. For example, Patent Document 2 discloses a curing sheet in which a heat-generating sheet and a waterproof sheet are laminated and integrally molded on a non-woven fabric, and when used for curing, the surface of the non-woven fabric is covered with concrete.

This curing sheet has the function of maintaining the wet state of the concrete casting surface by supplying water using non-woven fabric, and the temperature inside the sheet is maintained at around 10 ° C by releasing heat using the heat supply sheet. It has a function to do. In addition, since the non-woven fabric and the heat-generating sheet are integrally molded, the wet state of the cast surface and the curing temperature of around 10 ° C can be maintained for the entire curing period, so that the cold concrete using cement that hardens by the hydration reaction Suitable for.

Japanese Patent No. 5091519 Japanese Patent No. 2000-274075

However, when this curing sheet is diverted to the curing of geopolymer concrete, various inconveniences occur. Specifically, since the heat-generating sheet is integrated, it cannot be removed even if heating becomes unnecessary during the curing period, so that the heat-generating sheet cannot be reused, which is inefficient. Further, the temperature at which the heat generating sheet dissipates heat is not high enough to heat the geopolymer concrete. Further, since the non-woven fabric does not have a water-shielding function, it cannot retain the water to be evaporated from the uncured geopolymer concrete, and tends to cause drying shrinkage.

The present invention has been made in view of the above problems, and a main object thereof is a cast-in-place geopolymer cured product capable of constructing a sound cast-in-place geopolymer cured product with few cracks at a construction site. Is to provide the construction method of.

In order to achieve such an object, the method for constructing a cast-in-place geopolymer cured product of the present invention is a cast-in-place geopolymer for curing a geopolymer composition cast at a construction site to construct a cast-in-place geopolymer cured product. A method for constructing a cured polymer, in which the geopolymer composition after casting on site is covered with an impermeable sheet, and then a heating sheet formed separately from the impermeable sheet is placed on the impermeable sheet. It is characterized by comprising a step of laminating in a geopolymer and curing while heating with the heating sheet, and a step of removing the heating sheet after a lapse of a predetermined time from the start of curing and leaving the impermeable sheet to cure at room temperature. And.

According to the method for constructing a cast-in-place geopolymer cured product of the present invention, since heating is performed using a heating sheet, it is possible to promote a rapid polycondensation reaction and shorten the period until curing. As a result, it is possible to reduce the loss of water in the geopolymer composition, suppress shrinkage cracks caused by drying, and develop high compressive strength at an early stage.

In addition, since the polymer composition is cured using a water-impervious sheet at both the heating and normal temperature stages, it is possible to suppress not only the disappearance of water in the polymer composition by heating but also the surface drying during normal temperature curing. It is possible to construct a healthy cast-in-place geopolymer cured product.

Further, since the heating sheet is removed after a lapse of a predetermined time from the start of heat curing, it is possible to prevent the geopolymer composition from drying due to excessive heating, and the removed heating sheet can be used, for example, on the site site. It is possible to improve the construction efficiency, such as being able to reuse the geopolymer composition in the casting area.

The method for constructing the cast-in-place geopolymer cured product of the present invention is characterized in that the heating sheet is removed after 6 to 24 hours have passed from the start of curing.

According to the method of constructing the cast-in-place geopolymer cured product of the present invention, the heating is performed only in the initial period during the curing period, which can contribute to the suppression of cracks and the early development of compressive strength by heating, thus saving labor. At the same time, it is possible to construct a sound cast-in-place geopolymer cured product.

According to the present invention, the geopolymer composition placed at the construction site is controlled by using a water-impervious sheet so that water does not disappear, and a heating sheet molded separately from the water-impervious sheet is used. By adjusting the heating period with, it is possible to construct a sound cast-in-place geopolymer cured product with few cracks at the construction site.

It is a figure which shows the construction method of the cast-in-place geopolymer hardened body of this invention. It is a figure which shows the curing equipment which comprises the heating sheet and the impermeable sheet of this invention. It is a photograph which shows the state of the casting surface after 24 hours of the geopolymer concrete cured by the construction method of the cast-in-place geopolymer hardened body of this invention.

The present invention is a method for constructing a sound cast-in-place geopolymer cured product having few cracks by curing and curing the geopolymer composition cast on the construction site while adjusting the heating period while controlling the moisture. is there.

The geopolymer cured product is a cured product using so-called geopolymer technology in which an alkali-active filler and an alkaline solution mixed in the geopolymer composition are shrink-polymerized, and concrete that does not use a cement-based curing material. Alternatively, it is generally used as a mortar in the construction field and the like.

As the filler, fly ash, blast furnace slag fine powder, or the like is adopted, and as the alkaline solution, an aqueous sodium silicate solution, sodium hydroxide, or the like is adopted. Then, a geopolymer composition is prepared by mixing these with fine aggregate or fine aggregate with coarse aggregate, and the geopolymer composition is cast at a construction site, cured, and cured to obtain a geopolymer. Construct a cast-in-place geopolymer hardened material such as mortar or geopolymer concrete.

In the present embodiment, a case where the geopolymer concrete among the above-mentioned cast-in-place geopolymer hardened bodies is spliced onto the upper surface of a concrete skeleton using a cement-based hardened material is taken as an example, and FIGS. The construction method of the cast-in-place geopolymer cured product will be described with reference to it.

As shown in FIGS. 1 (a) and 1 (b), the inventors have placed a geopolymer composition G1 on the upper surface of the concrete skeleton C and hardened it to construct a geopolymer concrete G2 cast in the field. The following three findings have been obtained for the composition G1.

First, when curing is performed at a high temperature in the initial stage of the curing period, the polycondensation reaction is promoted, rapid curing progresses, and compressive strength is developed at an early stage. However, even if curing at a high temperature is continued, the reaction still occurs. As it converges, the intensity development reaches a plateau.

Secondly, when the curing at a high temperature is carried out for a long period of time, the water content in the geopolymer composition G1 is likely to evaporate, and the surface of the hardened geopolymer concrete is likely to undergo drying shrinkage cracks.

Thirdly, when the geopolymer composition G1 is cured at a factory, a sound secondary product can be produced by performing steam curing for about 6 to 8 hours (generally, the maximum temperature is about 65 ° C.).

Therefore, when curing the geopolymer composition G1 cast on site, care is taken to prevent water from evaporating. In addition, the first about 6 to 24 hours of the curing period is cured with heating, and then cured at room temperature. Further, the heating temperature for heating is 60 ° C.

Then, under the above conditions, it was decided to adopt the curing equipment 1 shown in FIG. 2 in order to cure the geopolymer composition G1 placed at the construction site. The curing facility 1 includes a water-impervious sheet 2 and a heating sheet 3 formed separately from the water-impervious sheet 2.

The water-impervious sheet 2 is used to prevent the water contained in the geopolymer composition G1 (for example, the water in the alkaline solution) from disappearing due to drying. Any material may be used as long as it has water impermeability, but in the present embodiment, a polyethylene sheet is used.

The heating sheet 3 can heat the entire casting surface of the geopolymer composition G1 with the impermeable sheet 2 interposed therebetween, and can heat the inside of the heating sheet 3 to about 60 ° C. If it is, any heat source may be equipped. In the present embodiment, the heating wire 4 is laid so as to form a flat surface, and the heat insulating material 5 is laminated on the upper surface thereof, and these are sandwiched between two waterproof sheets 6 to form a mat shape.

These function as a curing facility 1 capable of heating the lower surface side of the impermeable sheet by laminating the heating sheet 3 on the upper surface of the impermeable sheet 2. Hereinafter, a method for constructing a cast-in-place geopolymer cured product using the curing equipment 1 will be described with reference to FIG.

First, as shown in FIG. 1A, a formwork 7 is installed so as to surround the upper surface of a concrete skeleton C using a cement-based hardened material, and the geopolymer composition G1 is placed inside the formwork 7. Then, by covering the casting surface of the geopolymer composition G1 immediately after casting with the impermeable sheet 2 and laminating the heating sheet 3 on the upper surface thereof, the entire upper surface of the geopolymer composition G1 is covered by the curing facility 1. Cover.

In this state, the casting surface of the geopolymer composition G1 is heated to about 60 ° C. on the heating sheet 3 and cured for about 6 to 24 hours. The heating time may be appropriately adjusted in consideration of the site conditions, the outside air temperature, the composition of the geopolymer composition G1, and the like, and the optimum heating time may be determined by conducting a test construction in advance.

In the curing, the impermeable sheet 2 may simply cover the entire surface of the geopolymer composition G1 on which it is placed, but more preferably, heavy objects are installed at equal intervals on the upper end of the impermeable sheet 2. Alternatively, the end of the impermeable sheet 2 may be sandwiched between the mold 7 and the crosspiece and fixed by nailing or the like to provide a sealing cure. By doing so, the water-impervious sheet 2 can be brought into close contact with the surface of the geopolymer composition G1, so that the evaporation of water can be further prevented.

By heating at about 60 ° C. for a predetermined time in this way, the reaction between the metal ions eluted from the filler in the geopolymer composition G1 and the alkaline solution is promoted to form an amorphous shrunk polymer, and the geopolymer concrete is formed. It becomes G2.

After a predetermined time has passed from the start of curing, as shown in FIG. 1 (b), the heating sheet 3 of the curing equipment 1 is removed, the geopolymer concrete G2 is covered only with the impermeable sheet 2, and the curing is performed at room temperature. To do. Curing should be carried out for at least 7 days.

The removed heating sheet 3 may be reused for curing the geopolymer composition G1 in another casting area on the site site, for example, as shown in FIG. 1 (c). Further, in the present embodiment, only the casting surface of the geopolymer composition G1 is covered with the impermeable sheet 2 and the heating sheet 3, but the present invention is not necessarily limited to this, and the mold 7 is also included. It may be covered.

When the geopolymer composition G1 is cured by the above procedure, the polycondensation reaction is promoted and the period until curing can be shortened by heating using the heating sheet 3. As a result, shrinkage cracks due to drying can be suppressed without excessively eliminating the water content in the geopolymer composition G1, and high compressive strength can be exhibited at an early stage.

Further, since the water-impervious sheet 2 is used for curing at both the heating and normal temperature stages, it is possible to suppress the disappearance of water in the polymer composition G1 due to heating and the surface drying during normal temperature curing. Therefore, it is possible to construct a sound cast-in-place geopolymer concrete G2.

Further, since the heating sheet 3 is removed about 6 to 24 hours after the start of curing, it is possible to prevent the geopolymer composition G1 from drying due to excessive heating, and the removed heating sheet 3 is reused. It is also possible to improve the construction efficiency.

FIG. 3 shows the cast surface of the geopolymer concrete G2 cured by the above procedure and the comparative geopolymer concrete G3 cured without heating during the curing period. Both of them were cured for 24 hours after being placed on site.

Looking at FIG. 3A, it can be seen that the geopolymer concrete G2 heated at the initial stage during the curing period has no cracks on its surface. On the other hand, looking at FIG. 3 (b), it seems that the comparative geopolymer concrete G3, which was not heated during the curing period, had a large shrinkage in the process of polycondensation, and cracks were generated. Understand.

As described above, according to the construction method of the cast-in-place geopolymer cured product, the water-impervious sheet 2 is used to prevent drying, and a heating sheet molded separately from the water-impervious sheet 2 is used. Since the heating period can be adjusted with, it is possible to construct a sound cast-in-place geopolymer concrete G2 with few cracks at the construction site.

Further, by using the heating sheet 3, the casting surface of the geopolymer composition G1 can be raised to about 60 ° C., so that the heating curing can be performed at the optimum temperature for promoting the polycondensation reaction. It becomes.

The method of constructing the cast-in-place geopolymer cured product of the present invention is not limited to the above embodiment, and various changes can be made without departing from the spirit of the present invention.

In the present embodiment, the heat insulating material 5 is sandwiched between the two waterproof sheets 6 together with the heating wire 4 to produce the heating sheet 3, but the present invention is not necessarily limited to this. For example, a heating sheet 3 is manufactured by sandwiching only a heating wire 4 between two waterproof sheets 6, and a heat insulating material 5 is separately laminated on the upper surface thereof to form a curing facility 1 to heat the geopolymer composition G1. It may be a method of doing.

Further, in the present embodiment, the geopolymer composition G1 is cast and spliced in the formwork 7 installed so as to surround the upper surface of the concrete skeleton C, but it is not always necessary to use the formwork and it is underground. The geopolymer composition G1 may be cast and spliced on the concrete skeleton C cast in the holes by using the hole wall as a formwork.

Further, the geopolymer composition G1 is not limited to the mode in which it is cast on the upper surface of the concrete skeleton C so as to function as a protective layer on the concrete surface. For example, the geopolymer composition G1 is placed at the construction site, for example, by placing the ground directly on a compacted embankment structure or as a surface layer forming a road structure such as an airfield runway. If so, the construction method of the present invention may be adopted in any case.

1 Curing equipment 2 Water-impervious sheet 3 Heating sheet 4 Heating wire 5 Insulation material 6 Tarpaulin 7 Formwork C Concrete skeleton G1 Geopolymer composition G2 Geopolymer concrete (cast-in-place geopolymer hardened material)
G3 comparative geopolymer cured product

Claims (2)

A method for constructing a cast-in-place geopolymer cured product by curing the cast-in-place geopolymer composition at the construction site.
After covering the geopolymer composition after casting in the field with a water-impervious sheet, a heating sheet formed separately from the water-impervious sheet is laminated on the water-impervious sheet and heated by the heating sheet. The curing process and
A method for constructing a cast-in-place geopolymer cured product, which comprises a step of removing the heating sheet after a lapse of a predetermined time from the start of curing, leaving the impermeable sheet, and curing at room temperature. In the method for constructing a cast-in-place geopolymer cured product according to claim 1,
A method for constructing a cast-in-place geopolymer cured product, which comprises removing the heating sheet after 6 to 24 hours have passed from the start of curing.