Weed prevention paving method

Abstract

When paving a roadbed using a geopolimer paving material containing a geopolimer and a sodium-based alkali activator, the occurrence of various problems caused by sodium components deposited on the paving surface is suppressed. 【Solution means】In step S1, a roadbed is formed. In step S2, a geopolimer paving material containing at least an active filler containing blast furnace slag fine powder and sodium silicate powder as an activator is spread over the roadbed. In step S3, water is sprayed on the surface layer of the geopolimer paving material spread over the roadbed. In step S4, the sodium components deposited on the surface layer of the geopolimer paving material are confirmed. When the sodium components are confirmed, in step S5, an aqueous solution containing a boron-containing compound is sprayed on the surface layer of the geopolimer paving material.

Description

Technical Field

[0001] The present disclosure relates to a method for paving a roadbed using geopolymers.

Background Art

[0002] Geopolymers have attracted attention worldwide as a new binder to replace Portland cement. In Japan, fly ash and blast furnace slag fine powder are often mixed and used as the main raw materials of geopolymers.

[0003] The CO2 emissions of geopolymers vary depending on the evaluation method. When fly ash is used as the main raw material, it is said to have a CO2 reduction effect of about 80% compared to Portland cement. Even when fly ash and blast furnace slag fine powder are used in combination, it is said to have a CO2 reduction effect of 65 - 70%.

[0004] Geopolymers are superior in acid resistance and heat resistance (refractoriness) compared to hardened Portland cement. In addition, geopolymers are less likely to cause alkali-silica reactions, and a function of fixing harmful substances such as radioactive substances has been found from the solidification mechanism, and its utilization is expected.

[0005] As a prior art related to the present disclosure, Patent Document 1 can be cited. Patent Document 1 discloses an alkali-activated loess wet paving material applied to promenades, sidewalks, park roads, bicycle roads, etc. The paving material of Patent Document 1 contains blast furnace slag fine powder or fly ash and a non-sodium-based alkali-activated binder such as calcium hydroxide. However, Patent Document 1 also mentions a paving material in which a sodium-based alkali-activated binder is combined with blast furnace slag fine powder or fly ash as a paving material related to the present disclosure.

[0006] Patent Document 2 discloses a herbicide composition that is mixed or injected into the soil of parks, gardens, residential areas, parking lots, etc., or sprayed or dripped onto the soil surface. Patent Document 2 focuses on the fact that an oily substance extracted from trees belonging to the order Pinales such as the Cupressaceae family and the Pinaceae family has a weed control effect. Patent Document 2 describes that boron-containing compounds such as boric acid, borax, and calcium borate enhance the weed control effect of the oily substance.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] The inventors of the present disclosure have been developing a geopolimer paving material containing a geopolimer and a sodium-based alkaline activator and having a weed control function. In this development, powdered sodium silicate is used as the alkaline activator, and after spreading a geopolimer paving material added with a boron-containing compound for the purpose of imparting a weed control function on the roadbed, a method of spraying water on the surface layer of the geopolimer paving material for the purpose of solidifying the geopolimer paving material and fixing it to the roadbed material has been adopted.

[0009] However, it has been found that in this method, there is a problem that sodium components generated by the reaction of sodium silicate and water are deposited on the paving surface. When sodium components are deposited on the paving surface, not only does the aesthetics deteriorate, but there is also a possibility that the paving surface becomes slippery when the sodium components are wetted by rainfall or the like. In addition, if sodium components remain on the paving surface for a long period of time, there is also a possibility that cracks will occur on the paving surface due to the repeated cycle of water absorption and dehydration between the surrounding environment. Therefore, an improvement for suppressing the occurrence of such problems is desired.

[0010] One object of the present invention is to suppress the occurrence of various problems caused by sodium components deposited on the pavement surface when paving a roadbed using a geopolimer paving material containing a geopolimer and a sodium-based alkaline activator.

Means for Solving the Problems

[0011] Since the sodium component deposited on the pavement surface has a high affinity for water, if the sodium component is deposited during the solidification of the geopolimer paving material, water can be sprayed to dissolve it. However, if the water evaporates due to changes in the surrounding environment of the pavement surface, the sodium component will precipitate again. As a result of studying this problem, the inventors of the present disclosure found that by mixing the boron-containing compound not with the geopolimer paving material but with the water sprayed during the solidification of the geopolimer paving material to form an aqueous solution and then spraying it, the sodium component can be neutralized.

[0012] Therefore, the inventors further studied and found that spraying an aqueous solution of a boron-containing compound is excellent in that it can efficiently promote the processes of solidification of the geopolimer paving material, dissolution and neutralization of the sodium component, and thus completed the present invention.

[0013] The first aspect of the present disclosure is a weed control paving method, which has the following features. The weed control paving method includes: spreading a geopolimer paving material containing at least an active filler containing fine blast furnace slag powder and sodium silicate powder as an activator on a roadbed; spraying water on the surface layer of the geopolimer paving material spread on the roadbed; after spraying water on the surface layer, checking for sodium components deposited on the surface layer; when sodium components deposited on the surface layer are confirmed, spraying an aqueous solution containing a boron-containing compound on the surface layer. and

[0014] The second aspect of the present disclosure further has the following features in the first aspect. The weed prevention paving method further includes spraying an aqueous solution containing a boron-containing compound on the surface layer, and then checking the sodium component remaining on the surface layer, when the sodium component remaining on the surface layer is confirmed, adding and spraying an aqueous solution containing a boron-containing compound, and includes.

[0015] The third aspect of the present disclosure further has the following features in the first or second aspect. The confirmation of the sodium component deposited on the surface layer is performed after the elapse of a predetermined curing time starting from the completion of spraying water on the surface layer.

[0016] The fourth aspect of the present disclosure further has the following features in the first or second aspect. Spraying water on the surface layer is performed two or more times before confirming the sodium component deposited on the surface layer.

[0017] The fifth aspect of the present disclosure further has the following features in the first or second aspect. Sodium silicate powder contains sodium orthosilicate. The content of sodium orthosilicate is 2 to 50 parts by weight with respect to 100 parts by weight of the activator.

[0018] The sixth aspect of the present disclosure further has the following features in the first or second aspect. Sodium silicate powder contains anhydrous sodium metasilicate. The content of anhydrous sodium metasilicate is 10 to 30 parts by weight with respect to 100 parts by weight of the activator.

Advantages of the Invention

[0019] According to the present disclosure, when precipitation of sodium components is confirmed after spraying water on the surface layer of a geopolimer paving material laid on a roadbed, an aqueous solution containing a boron-containing compound is sprayed on this surface layer. Thereby, the sodium components (alkalis) precipitated during the solidification of the geopolimer paving material can be dissolved and neutralized by the aqueous solution containing the boron-containing compound. In addition, boric acid is effective in preventing weeds on the paved surface (particularly in preventing the growth of mosses), and it is also possible to impart a weed prevention function by fixing the boric acid component contained in the aqueous solution containing the boron-containing compound to the surface layer of the geopolimer paving material.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0021] Embodiments of the present invention will be described in detail below. In this specification, "parts by weight" means the ratio to the weight when the weight of the active filler is used as a reference. Also, when a numerical range is represented using "~", the range includes the numerical values at both ends.

[0022] 1. Geopolimer paving material In the weed prevention paving method according to the embodiment, a geopolimer paving material is used. This geopolimer paving material includes, for example, an active filler containing at least fine powder of blast furnace slag, and sodium silicate powder as an activator.

[0023] The blast furnace slag fine powder used as an active filler (hereinafter also referred to as "BFS") is a by-product obtained when iron is refined in a blast furnace. The main components of BFS are calcium oxide (CaO), silicon dioxide (SiO2), alumina (Al2O3), etc., and its quality is specified in JIS A 6206. BFS is an amorphous substance with latent hydraulicity, and the calcium component contained therein reacts in the geopolymers paving material to generate calcium silicate hydrate (CSH) and harden.

[0024] BFS is classified based on the range of the Blaine specific surface area. The range of the Blaine specific surface area is 2750 cm 2 / g or more and less than 3500 cm 2 / g, 3500 cm 2 / g or more and less than 5000 cm 2 / g, 5000 cm 2 / g or more and less than 7000 cm 2 / g, and 7000 cm 2 / g or more and less than 10000 cm 2 / g. The BFS preferably used as an active filler includes standard surface area powder with a Blaine specific surface area of 3000 - 4500 cm 2 / g, and high surface area powder with a Blaine specific surface area of 6000 - 10000 cm 2 / g. These BFSs are used alone or simultaneously.

[0025] The fact that the active filler "contains at least BFS" means that other active fillers may be included. Examples of such active fillers include pozzolanic substances. In this specification, pozzolanic substances are substances other than BFS that react with the calcium component contained therein to generate calcium silicate hydrate. Examples of pozzolanic substances include fly ash, metakaolin, silica fume, pulp sludge incineration ash, sewage sludge incineration ash, and waste glass powder. These pozzolanic substances are used alone or simultaneously.

[0026] Preferred pozzolanic materials used in combination with BFS include fly ash (hereinafter also referred to as "FA"). FA is coal ash generated during coal combustion in coal-fired power plants and is recovered from exhaust gas by a dust collector. The main components of FA are silicon dioxide, alumina, etc. FA is classified into types I to IV based on particle size and flow value according to JIS A 6201. Preferred AFs used in combination with BFS include types I and II with fine particle size and high reactivity.

[0027] When BFS and an active filler other than BFS are used in combination, the blending amount of the active filler is not particularly limited, and it can be appropriately adjusted according to the application destination of the geopololymer paving material (for example, the central separation strip, roadside strip, tree planting strip of a road, the side of a railway track, near a level crossing, passageways (such as schools, welfare facilities, cemeteries, companies, factories, etc.), residences (entrance approaches, dog runs, gardens, etc.)) and the desired mechanical properties such as abrasion resistance, impact resistance, and elasticity imparted to the geopololymer paving material. When BFS and an active filler other than BFS are used in combination, the blending amount of the active filler is, for example, 10 to 200 parts by weight with respect to 100 parts by weight of BFS. In another example, the blending amount of the active filler other than BFS is 100 to 200 parts by weight with respect to 100 parts by weight of BFS. In yet another example, the blending amount of the active filler other than BFS is 10 to 100 parts by weight with respect to 100 parts by weight of BFS.

[0028] Examples of the powdered sodium silicate used as an activator include sodium orthosilicate and anhydrous sodium metasilicate. Sodium orthosilicate and anhydrous sodium metasilicate may be used alone or simultaneously. Sodium silicate is also called water glass, and many of the compounds collectively referred to as water glass are in a liquid state. For example, all of the sodium silicates No. 1 to No. 3 specified in JIS K 1408 are liquids. On the other hand, sodium metasilicate and sodium orthosilicate are in a powder state. Sodium metasilicate is classified into three types: nonahydrate, pentahydrate, and anhydrous salt according to the number of hydrated water molecules. The anhydrous salt among these corresponds to anhydrous sodium metasilicate. Although hydrated salts also exist in sodium orthosilicate, there is no classification based on the number of water molecules like that of sodium metasilicate.

[0029] As the powdered sodium silicate, sodium metasilicate other than anhydrous sodium metasilicate, powders obtained by drying and pulverizing liquid water glass, etc. can also be used. However, when these other sodium silicates are used as an activator, a highly alkaline solution is required for the solidification of the diopolymer paving material. In this regard, sodium orthosilicate and anhydrous sodium metasilicate have the advantage that they can generate sodium hydroxide by adding water, so the use of a highly alkaline solution can be omitted, and the safety of the construction work can be enhanced.

[0030] When sodium orthosilicate is used as the powdered sodium silicate, from the viewpoints of the initial and final setting times (initial and final solidification times), the blending amount of sodium orthosilicate is 2 to 50 parts by weight with respect to 100 parts by weight of the active filler. The lower limit of this blending amount is preferably 5 parts by weight, more preferably 15 parts by weight. On the other hand, the upper limit of this blending amount is preferably 45 parts by weight, more preferably 35 parts by weight.

[0031] When anhydrous sodium metasilicate is used as the sodium silicate powder, from the viewpoints of initial and final setting times, the compounding amount of anhydrous sodium metasilicate is 10 to 30 parts by weight with respect to 100 parts by weight of the active filler. The lower limit of this compounding amount is preferably 15 parts by weight. On the other hand, the upper limit of this compounding amount is preferably 25 parts by weight.

[0032] 2. Boron-containing compound In the weed control paving method according to the embodiment, an aqueous solution containing a boron-containing compound is also used. Examples of the boron-containing compound include water-soluble boron compounds. Examples of the water-soluble boron compounds include boric acid, borax, sodium metaborate, sodium tetraborate, potassium borate, ammonium borate, etc. Water-soluble boron-containing minerals (natural boron ores) such as colemanite, ulexite, and inyoite, which are raw materials for boron, borax, etc., are also included in the boron-containing compound. Preferred boron-containing compounds include borax, sodium metaborate, potassium borate, and colemanite, which have high water solubility.

[0033] 3. Sand In the weed control paving method according to the embodiment, various sands may also be added to the geopololymer paving material. The various sands are used for the purpose of enhancing the strength and durability of the geopololymer paving material, or for the purpose of finishing the surface layer such as anti-slip, landscape, and water permeability. Examples of such sands include mountain sand, river sand, crushed sand, sieved sand, washed sand, natural sand, andesite crushed sand, silica sand, limestone sand, etc. Color sands (such as red, yellow, blue, brown, white, black, etc.) obtained by coating particles of raw material sands such as silica sand, crushed sand, and limestone sand with an inorganic pigment and a resin binder are also examples. These sands are used alone or simultaneously.

[0034] When various sands are added, the blending amount of the sand is not particularly limited and can be appropriately adjusted according to the application destination of the geopolimer paving material (for example, sidewalks, park roads, promenades) and the desired mechanical properties such as abrasion resistance, impact resistance, and elasticity imparted to the geopolimer paving material. When blending sand, the blending amount of the sand is 1 to 100 parts by weight with respect to 100 parts by weight of the active filler. In another example, the blending amount of the sand is 100 to 500 parts by weight with respect to 100 parts by weight of the active filler. In yet another example, the blending amount of the sand is 500 to 1000 parts by weight with respect to 100 parts by weight of the active filler.

[0035] 4. Specific Examples of Paving Methods Hereinafter, the weed prevention paving method according to the embodiment will be specifically described with reference to FIG. 1. FIG. 1 is a flowchart showing an example of the weed prevention paving method according to the embodiment. The example shown in FIG. 1 includes steps S1 to S5.

[0036] Step S1 is a step of forming a roadbed. In step S1, first, the vegetation and its roots at the construction site are removed. Then, crushed stones are laid at the construction site to adjust and roll the unevenness of the roadbed to form a sufficiently strong ground. The thickness of the roadbed is, for example, 100 mm or more. In order to prevent weeds, when rolling, a rolling machine such as a trowel or a roller is used according to the construction site, and sufficient rolling is performed to compact it.

[0037] Subsequent to step S1, step S2 is performed. Step S2 is a step of spreading the geopolimer paving material evenly on the roadbed formed through step S1. Examples of the geopolimer paving material are as described above. In step S2, the geopolimer paving material is laid on the roadbed, and rolling is performed using a trowel. When using a roller, after leveling the surface of the geopolimer paving material with a dragonfly or the like, rolling is performed. The even spreading of the geopolimer paving material is performed in multiple steps until the construction thickness (for example, 10 to 40 mm) is reached. After the even spreading, in order to erase the marks of the trowel or the roller and eliminate the bias of the surface particles, it may be lightly roughened and finished using a brush or a broom.

[0038] Following step S2, step S3 is carried out. Step S3 is a step of spraying water on the surface layer of the geopolimer paving material formed through step S2. The water used in step S3 is water that does not contain the boron-containing compound described above (for example, tap water). In step S3, water is sprayed to such an extent that the surface is uniformly wetted using a watering can, a spray, etc. The spraying of water is carried out in multiple times so that ponding and loss of the material do not occur. For example, after the first spraying of water, wait until the water on the surface drains, and then repeat the spraying of water, such as by carrying out the second spraying of water when the water has drained. After the water on the surface has drained, rolling may be carried out using a roller before the surface is completely dry. When using a trowel instead of a roller, this rolling may be carried out by tapping the surface.

[0039] When the geopolimer paving material leveled in step S2 contains at least one of sodium orthosilicate and sodium metasilicate anhydride, water may be sprayed as described above in step S3. Otherwise, for example, when the geopolimer paving material contains at least one of a powder obtained by drying and pulverizing a sodium metasilicate other than sodium metasilicate anhydride and a liquid water glass and does not contain sodium orthosilicate or sodium metasilicate anhydride, it is necessary to spray water added with an alkaline component such as sodium hydroxide in step S3.

[0040] Following step S3, step S4 is carried out. Step S4 is a step of confirming the precipitation of the sodium component. When water is sprayed in step S3, the activator (powdered sodium silicate) contained in the geopolimer paving material reacts with the water, and the alkali (sodium hydroxide) generated thereby causes the geopolimer component contained in the active filler to condense and cure (solidify). However, the alkali that did not contribute to the curing reaction precipitates as the surface layer of the geopolimer paving material dries. The confirmation of the precipitation is carried out by visual inspection or recognition processing using a camera image of the surface layer.

[0041] Here, the precipitation situation of the sodium component will be described with reference to FIG. 2. FIG. 2 is a diagram for explaining a construction example of the paving material performed by the inventors of the present disclosure. In the upper part of FIG. 2, photos of the construction site from the end of construction to the third day after construction are shown. As understood from the upper part of FIG. 2, the surface layer of the paving material starts to dry from the end of construction. In the example of FIG. 2, precipitates (white precipitates) of the sodium component are confirmed on the surface layer on the third day after construction. The time until the sodium component precipitates can vary depending on construction factors such as the construction environment and the construction thickness of the geopolimer paving material. Therefore, it is desirable to perform the confirmation in step S4 in consideration of these construction factors after the elapse of a predetermined curing time starting from the end of step S3.

[0042] Returning to FIG. 1, the description will be continued. When the precipitation of the sodium component is confirmed in step S4, step S5 is performed. Step S5 is a step of spraying an aqueous solution containing a boron-containing compound on the surface layer. Examples of the boron-containing compound are as described above. In step S5, the aqueous solution containing the boron-containing compound is sprayed in multiple portions while taking care not to damage the surface layer (rolled surface).

[0043] The photo on the third day after construction shown in the upper part of FIG. 2 includes the area where the aqueous solution was sprayed and the area where it was not. By spraying the aqueous solution, the sodium component is dissolved and neutralized. If residues of the sodium component are confirmed after spraying the aqueous solution, the aqueous solution containing the boron-containing compound may be sprayed again. That is, steps S4 and S5 may be repeated until the sodium component disappears. In the lower part of FIG. 2, photos of the construction site on the seventh and eighth days after construction are shown. As understood from these photos, it is understood that after sufficient spraying of the aqueous solution, the sodium component does not precipitate even when the surface layer dries.

[0044] 5. Effects According to the embodiment described above, when precipitation of sodium components is confirmed after spraying water on the surface layer of the geopolimer paving material laid on the roadbed, an aqueous solution containing a boron-containing compound is sprayed on this surface layer. Thereby, the sodium components precipitated during the solidification of the geopolimer paving material can be dissolved and neutralized by the aqueous solution. Also, since boric acid is effective in preventing weeds on the paved surface (particularly in preventing the growth of moss), it is also possible to impart a weed prevention function by fixing the boric acid component contained in the aqueous solution to the surface layer of the geopolimer paving material.

Claims

1. A geopolymer pavement material containing at least an active filler containing ground granulated blast furnace slag and powdered sodium silicate as an activator is laid on a roadbed; Spraying water on the surface layer of the geopolymer pavement material laid on the roadbed; Spraying water onto the surface layer and then confirming the sodium component precipitated on the surface layer; When a sodium component is confirmed to be precipitated on the surface layer, spraying an aqueous solution containing a boron-containing compound onto the surface layer; A weed-prevention paving method comprising:

2. Spraying an aqueous solution containing a boron-containing compound onto the surface layer, and then confirming the sodium component remaining on the surface layer; If sodium components remaining on the surface layer are found, an aqueous solution containing a boron-containing compound is additionally sprayed; The weed-prevention paving method according to claim 1, further comprising:

3. The sodium component precipitated on the surface layer is confirmed after a predetermined curing time has elapsed, calculated from the completion of the spraying of water on the surface layer.

3. The weed-prevention paving method according to claim 1 or 2.

4. Water is sprayed onto the surface layer at least twice before the sodium component precipitated on the surface layer is confirmed.

3. The weed-prevention paving method according to claim 1 or 2.

5. the powdered sodium silicate comprises sodium orthosilicate; The content of the sodium orthosilicate is 2 to 50 parts by weight based on 100 parts by weight of the activator.

3. The weed-prevention paving method according to claim 1 or 2.

6. the powdered sodium silicate comprises anhydrous sodium metasilicate; The content of the anhydrous sodium metasilicate is 10 to 30 parts by weight per 100 parts by weight of the activator.

3. The weed-prevention paving method according to claim 1 or 2.

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