Earth block, semi-finished earth block, and method for manufacturing earth block

Abstract

To provide a soil-based block, a half-finished product of the soil-based block, and a method for manufacturing the soil-based block capable of avoiding the discharge of a large amount of carbon dioxide in a manufacturing process and facilitating pavement construction.SOLUTION: A mixture is obtained by kneading a soil-based aggregate, a solidifying agent containing magnesium oxide and magnesium chloride, and phosphoric acid, the mixture is molded into a pavement block by an immediate demolding method, and a soil-based block semi-finished product is obtained when strength required for a pavement material is developed through a curing process. When shot processing is applied to this semi-finished product, it becomes a soil-based block. Since magnesium oxide and magnesium chloride are used as solidifying agents and cement is not used, large emissions of carbon dioxide can be avoided in the manufacturing process. In addition, it is molded into pavement blocks so that pavement construction can be performed easily.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an earth block used for paving, etc., a semi-finished earth block, and a method for manufacturing an earth block. [Background technology]

[0002] Concrete blocks have traditionally been used for paving. The cement used to manufacture concrete blocks is made by heating raw materials such as limestone and clay in a kiln to a high temperature of around 1500°C, and then adding gypsum to the resulting clinker. This manufacturing process, which includes a high-temperature firing step, generates a large amount of carbon dioxide. Carbon dioxide emissions have a significant negative impact on global warming, so it is desirable to avoid them. Therefore, the use of cement-free soil-based paving materials has been considered.

[0003] The prior art of Patent Document 1 is a technology in which a mixture of soil and magnesium oxide is used as a paving material. This conventional technology requires two steps for paving work: a spreading step in which the paving material is spread evenly on the ground and a hardening step in which the material is hardened by spraying water on the ground. This makes construction extremely time-consuming. Furthermore, even when the mixture is molded into paving blocks, it lacks strength.

[0004] The prior art in Patent Document 2 discloses a soil solidification agent for solidifying soil used in paving, which contains magnesium oxide and different metal salts, including magnesium chloride. In this conventional technique, a soil solidifying agent is added to the soil, which is then stirred and mixed to form a soil paving material, which is then used for paving work. Construction requires three steps: a spreading process in which the soil paving material is poured onto the foundation ground and leveled evenly, a compaction process in which the material is firmly compacted, and a hardening promotion process in which an aqueous solution of a hardening accelerator is sprayed to promote hardening. Therefore, construction is extremely time-consuming. Furthermore, since the above mixture lacks strength, Patent Document 2 does not mention molding it into paving blocks. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-51849 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-154735 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above circumstances, the present invention aims to provide soil blocks, semi-finished soil blocks, and a method for manufacturing soil blocks that can avoid large amounts of carbon dioxide emissions during the manufacturing process and that facilitate paving construction. [Means for solving the problem]

[0007] The soil block of the first invention is a mixture of soil aggregate, a solidifying agent containing magnesium oxide and magnesium chloride, and phosphoric acid, and the mixture is molded into a paving block. The mixing ratio of the solidifying agent is 0.1 to 0.6 mass% relative to the soil aggregate, the amount of magnesium chloride used in the solidifying agent is 50 to 150 mass% relative to the magnesium oxide, and the amount of phosphoric acid added is 0.005 to 0.04 mass% relative to the solidifying agent, and the surface of the paving block is shot-processed. Characterized by 。 No. 2 The semi-finished soil block of the present invention is a mixture obtained by adding and kneading a solidifying agent containing magnesium oxide and magnesium chloride with phosphoric acid, The mixture is used for paving block The mixing ratio of the solidifying agent is 0.1 to 0.6 mass% with respect to the soil aggregate, the amount of magnesium chloride used in the solidifying agent is 50 to 150 mass% with respect to the magnesium oxide, and the amount of phosphoric acid added is 0.005 to 0.04 mass% with respect to the solidifying agent, and the surface of the mixture remains in the molded state. Characterized by 。 [Effects of the Invention]

[0008] According to the first invention, magnesium oxide and magnesium chloride are used to solidify the soil aggregate, and no cement is used, so it is possible to avoid large amounts of carbon dioxide emissions during the manufacturing process. In addition, since the material is molded into paving blocks, paving construction can be easily carried out. moreover,The surface is shot-processed, resulting in a paving material that is beautiful and non-slip even during rainfall. No. 2 According to the invention, magnesium oxide and magnesium chloride are used to solidify the soil aggregate, and no cement is used, so large amounts of carbon dioxide emissions can be avoided during the manufacturing process. 。 [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a process diagram showing a method for manufacturing a soil block according to the present invention. [Figure 2] 1 is a graph showing the bending strength of Example 1 and Comparative Examples 1 and 2. [Figure 3] 1 is a graph showing the development of bending strength based on curing conditions. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, an embodiment of the present invention will be described in detail. (earth block) The soil-based block of the present invention is a block whose main material is soil-based aggregate and is characterized by not using cement. The soil-based blocks of the present invention are a mixture of soil-based aggregate, a solidifying agent containing magnesium oxide and magnesium chloride, and phosphoric acid, which is molded into paving blocks using an instant demolding method and has its surface shot-processed.

[0011] In this specification, soil aggregate refers to materials including not only soil but also sand, gravel, etc. Soil includes a variety of soil types, but a representative example is granite. Granite is a sandy soil formed by the weathering of granite rock, and is typically used as soil dressing.

[0012] Magnesium oxide and magnesium chloride are used as solidifying agents. When magnesium oxide is mixed with soil, it combines with the amorphous components contained in the soil (SiO2, Al2O3, Fe2O3, etc.) to form a hardened soil body, which allows the strength of the soil aggregate to be expressed.

[0013] Magnesium chloride reacts with calcium, iron, and aluminum in the soil, causing a caking phenomenon, which has the effect of compacting the soil aggregate.

[0014] In the present invention, both magnesium oxide and magnesium chloride are used as solidifying agents. Magnesium oxide alone does not satisfy the strength required for paving blocks, so mixing with magnesium chloride is essential. The amount of magnesium chloride used must be 50% to 150% by mass of the magnesium oxide to ensure the strength required for paving blocks. In particular, it is preferable to use approximately equal amounts of magnesium oxide and magnesium chloride to ensure strength.

[0015] Phosphate is used as a water resistance improver. When phosphate ions combine with magnesium ions, they form the water-insoluble compounds Mg2P2O7 or Mg3(PO4)2·8 / 10H2O. Because these compounds are water-insoluble, mixing them improves the water resistance of hardened soil.

[0016] When magnesium oxide and magnesium chloride, which act as solidifying agents, are mixed in the soil, they react to form 5Mg(OH)2·MgCl2·8H2O, which forms needle-shaped crystals that are very strong. The strength of the soil hardened body mixed with these needle-shaped crystals is high, and the bending strength of the blocks after they are made is also high. In the present invention, phosphoric acid is also mixed, so phosphate ions (PO4 3- ) penetrates and coats the soil in a gelatin-like form, making it difficult for moisture such as snow and rain to penetrate inside. As a result, the water resistance of the hardened soil body is improved.

[0017] The ratio of solidifying agent to soil aggregate is preferably 0.1 to 0.6 by mass. Within this range, the binding strength of the soil aggregate is sufficient for use as paving blocks. On the other hand, if the ratio is below the lower limit (10% by mass), the required binding strength cannot be achieved, and if the ratio is above the upper limit (60% by mass), the strength may increase but the texture of soil will be lost.

[0018] The amount of phosphoric acid added is 0.005 to 0.04 mass% of the solidifying agent. If the amount of phosphoric acid added is below the lower limit (0.5 mass%), water resistance will not be sufficiently improved, while if the amount is above the upper limit (4 mass%), the hardening time will be long, making it difficult to demold the next day. Furthermore, a good balance between water resistance and hardening time is achieved at 1 to 3 mass%.

[0019] The soil blocks of the present invention, to which the solidifying agent in the above-mentioned proportions has been added, have sufficient strength for use as paving materials and do not lose their shape even when people walk on them. Moreover, because the addition of phosphoric acid makes them water-resistant, the block shape does not collapse even when exposed to moisture from rain or snow. However, after a long period of use, such as several years, the blocks will self-disintegrate, losing their shape and returning to the same form as natural soil. This self-disintegrating property occurs when magnesium oxide and magnesium chloride come into contact with rainwater, etc., causing hydrolysis, which causes the needle-like crystals to disappear and weakens the binding force of the soil aggregate.

[0020] (semi-finished product) The semi-finished soil block of the present invention is a molded product obtained by adding a solidifying agent containing magnesium oxide and magnesium chloride, phosphoric acid, to soil aggregate, and kneading the mixture, and then molding it into a paving block.The only difference from the finished soil block is that it does not undergo the processing step (shot processing) in the manufacturing process described below, so it has the same solidification strength and water resistance as the finished product.

[0021] (Manufacturing method) As shown in Figure 1, the method for manufacturing soil blocks according to the present invention is a manufacturing method that sequentially carries out the following steps: a mixing step S1 in which a solidifying agent containing magnesium oxide and magnesium chloride and phosphoric acid are added to soil aggregate and mixed; a molding step S2 in which the mixture obtained in the mixing step S1 is placed in a mold and molded into a block using an immediate demolding method; a curing step S3 in which the block-shaped product obtained in the molding step S2 is cured; and a processing step S4 in which the surface of the semi-finished block that has undergone the curing step S3 is shot-processed.

[0022] In the mixing step S1, the soil aggregate is mixed with the solidifying agents magnesium oxide and magnesium chloride, and phosphoric acid, and then mixed. Initially, everything except water is mixed dry, just like cement concrete. Then, water is added and the mixture is mixed properly.

[0023] The ratio (B / A) of the total mass A of the solidifying agent consisting of magnesium oxide and magnesium chloride to the mass B of water is preferably 0.1 to 0.3. To facilitate kneading, it is preferable to use magnesium oxide and magnesium chloride in the form of fine particles or powder.

[0024] The blending ratio in the kneading step S1 is as described above. For example, 1 m of the mixture 3 It contains 140-200 kg of magnesium oxide, 140-200 kg of magnesium chloride, 7-10 kg of phosphoric acid, 28-120 kg of water, and 1800-2500 kg of earth aggregate.

[0025] In the molding process S2, the mixture obtained in the mixing process S1 is poured into a mold and molded using the immediate demolding method. For reference, there are two methods for manufacturing concrete blocks: the pouring method and the immediate demolding method. The pouring method is a method in which ready-mixed concrete with a high moisture content is poured into a mold using vibration compaction and requires approximately one day of dry curing. The immediate demolding method is a method in which dry ready-mixed concrete with a low moisture content is poured into a mold while vibrating, compacted under high pressure, and then demolded from the mold without curing.

[0026] In the present invention, the above-mentioned immediate demolding method is applied. The mixture after the kneading step S1 is in a dry state with a low water content, and is poured into a mold while being vibrated, compacted under high pressure, and demolded from the mold without curing. In this instant demolding method, the mixture in the mold is compacted by vibration to form paving blocks with high strength and excellent dimensional accuracy. There are no particular restrictions on the shape and size of the paving blocks, as long as they are suitable for construction of paved roads, etc.

[0027] The curing step S3 is a step in which the paving blocks are left under certain conditions for a certain period of time after molding. During this curing period, the necessary strength is developed.

[0028] The semi-finished product referred to in this specification refers to a block-like product that has undergone the curing step S3 but has not yet undergone the processing step S4. The semi-finished soil block product that has undergone the curing process has the same composition as the finished product and has undergone the necessary curing period, so it has the strength required for paving materials.

[0029] In the processing step S4, the surface of the semi-finished product is shotcreted. Shotcreting refers to a process in which an iron ball is struck against the surface of the block to roughen the surface. Shotcreting gives the block a beautiful appearance like the cracked surface of stone, and also provides functionality such as being less slippery even during rain. This processing step S4 is optional in the present invention, and both blocks that have been processed and those that have not been processed are included in the soil-based blocks of the present invention.

[0030] By carrying out the above steps S1 to S4, a soil block is obtained as a finished product.

[0031] (Use of soil blocks as finished products) By applying the necessary shot blasting to the surface of the semi-finished earth block, it becomes a finished earth block. This earth block has a beautiful appearance like the cracked surface of stone and is less slippery when people walk on it. Construction as paving blocks can be done in the same way as concrete blocks; simply level the ground and then lay them down. After being used as paving blocks for a long period of time, they will naturally disintegrate and take on a form similar to natural soil. For this reason, they can be laid on sidewalks as blocks for a certain period of time, and then returned to soil pavement after the period is over, eliminating the need for removal. [Example]

[0032] (Example) Examples 1 and 2 were prepared with the blending ratios shown in Table 1. Example 1 used a blending ratio near the lower limit, and Example 2 used a blending ratio near the upper limit. [Table 1]

[0033] (1) Strength development through curing A comparison was made between Example 1 and Comparative Examples 1 and 2 in terms of strength development due to curing. The results are shown in Figure 2. In Figure 2, Example 1 is Example 1 shown in Table 1. Comparative Example 1 is an earth-based block similar to Example 1 except that it does not contain phosphoric acid, and Comparative Example 2 is a conventionally known cement block. The left vertical axis in Figure 2 represents bending strength (N / mm 2 ) and the right vertical axis indicates residual strength (%). Two curing conditions were prepared: one after 7 days of age (shown by coarse dots) and one after immersion in water for 3 days after 7 days of age (shown by dense dots).

[0034] The strength at 7 days was 5.5 to 6.0 N / mm for both Example 1 and Comparative Example 1. 2 The cement block of Comparative Example 2 had a strength of 4.5 N / mm 2 It shows a greater strength than After 7 days of age and 3 days of immersion in water, Comparative Example 1 without phosphoric acid had a bending strength of 1.7 N / mm 2 In comparison, Example 1 has a bending strength of 3.4 N / mm 2 This shows that the addition of phosphoric acid has improved water resistance. The residual strength (shown by the dotted line) is 100% at 7 days old, and indicates the percentage of strength loss after immersion in water for 3 days. Example 1 with phosphoric acid shows 61.4%, which is approximately double the strength of Comparative Example 1 without phosphoric acid.

[0035] (2) Effect of curing conditions on strength development A test was carried out to confirm the influence of the curing conditions on Example 1. The results are shown in Figure 3. The curing was carried out for one day after demolding, followed by natural curing for five days. The curing conditions were (A) 20°C and 30% humidity, (B) 20°C and 60% humidity, (C) 30°C and 10% humidity, and (D) 10°C and 30% humidity. The vertical axis shows the bending strength (unit: N / mm 2 The bending strength after curing was 4.3 to 4.6 N / mm under all curing conditions. 2 This indicates that the bending strength does not change much due to the temperature and humidity conditions during curing. [Industrial Applicability]

[0036] The soil-based blocks of the present invention can be used as paving materials for roads and other purposes without any particular restrictions. They can also be used for outdoor structures that are intended to self-destruct, such as walkways and pavilions in parks. [Explanation of symbols]

[0037] S1 Kneading process S2 Molding process S3 curing process S4 Processing process

Claims

1. A mixture of soil aggregate, a solidifying agent containing magnesium oxide and magnesium chloride, and phosphoric acid, which is kneaded together, and the mixture is molded into paving blocks; The mixing ratio of the solidifying agent to the soil aggregate is 0.1 to 0.6 mass %, The amount of magnesium chloride used in the solidifying agent is 50 to 150 mass % based on the magnesium oxide, The amount of phosphoric acid added is 0.005 to 0.04 mass relative to the solidifying agent, The surface of the paving blocks is shot-processed An earth-based block characterized by:

2. A mixture obtained by adding a solidifying agent containing magnesium oxide and magnesium chloride and phosphoric acid to an earth aggregate and kneading the mixture, and the mixture is molded into the shape of a paving block. The mixing ratio of the solidifying agent to the soil aggregate is 0.1 to 0.6 mass %, The amount of magnesium chloride used in the solidifying agent is 50 to 150 mass % based on the magnesium oxide, The amount of phosphoric acid added is 0.005 to 0.04 mass relative to the solidifying agent. The surface of the mixture remains in the molded state. A semi-finished earth block product characterized by:

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