Construction materials and ground improvement methods using them

Abstract

This invention provides a construction material that is sustainable and environmentally friendly, and a ground improvement method using it, which can be used for structures as well as ground improvement applications, by using materials that can be supplied stably and do not cause environmental problems such as environmental pollution or increased carbon dioxide emissions. [Solution] A construction material whose main component is incinerated ash obtained by burning waste derived from marine and / or land products, wherein amorphous silica incinerated ash is the main component and Ca-containing incinerated ash containing at least Ca is used as a reactant, and which is used for structural purposes or as a solidifying agent in chemical grouting, high-pressure jet mixing, or mixing-type ground improvement methods. A ground improvement method using the above construction material when improving the ground by chemical grouting, high-pressure jet mixing, or mixing-type ground improvement methods.

Description

Technical Field

[0001] The present invention relates to a construction material made of a material containing metals such as silica and calcium derived from marine or terrestrial products, and a ground improvement method using the same, and particularly relates to a technology for effectively utilizing a material that has conventionally been disposed of as industrial waste as a valuable resource.

Background Art

[0002] In Japan where cities are formed on soft ground such as river basins, many damages due to liquefaction and sliding failure of the ground have been reported due to the occurrence of large earthquakes. Against this background, ground improvement is carried out by methods such as the cement mixing method and the chemical solution injection method.

[0003] Cement-improved soil is obtained by adding 5 to 15% (50 to 200 kg / m 3 ) of cement (mainly ordinary Portland cement) and an appropriate amount of water to soil, mixing them, and compacting and solidifying them. The applications of ground improvement using cement-based consolidants cover a wide range, such as earthquake resistance and liquefaction countermeasures, and are applied at various improvement sites. However, it is known that the carbon dioxide emission amount in the manufacturing process of ordinary Portland cement is approximately 800 kg / t, which is quite high.

[0004] In contrast, currently, in order to suppress the carbon dioxide emission amount, instead of ordinary Portland cement, blast furnace cement mixed with blast furnace slag or fly ash cement mixed with fly ash is used. However, the carbon dioxide emission amounts of these blast furnace slag and fly ash are still high, approximately 500 to 650 kg / t.

[0005] Furthermore, during the manufacturing process of ordinary Portland cement, trivalent chromium contained in the raw materials oxidizes, producing hexavalent chromium, a harmful substance that does not exist in nature. While sufficient hydration can be achieved in concrete products and structures, in cement-improved soil, sufficient hydration cannot be achieved due to the chemical composition of the soil, the heterogeneity of the ground, or the construction method. This raises concerns that hexavalent chromium may leach out, potentially causing environmental pollution.

[0006] Furthermore, since blast furnace slag and fly ash are by-products obtained from the Earth's resources, there is a possibility that their supply may become unavailable in the future. Specifically, fly ash is a by-product obtained when burning coal ash to generate electricity, but in recent years, there has been a shift from coal-fired power generation to renewable energy sources such as solar and wind power, so it is expected that the supply will decrease in the future. Similarly, blast furnace slag is a by-product generated when iron is melted and reduced from iron ore in a blast furnace, but because blast furnaces emit large amounts of carbon dioxide, there is a shift towards electric arc furnaces using renewable energy, and in addition, the recycling of iron waste is progressing, in which case electric arc furnaces are used. Therefore, the supply of blast furnace slag will also tend to decrease in the future.

[0007] The combustion temperature of ordinary Portland cement is around 1,300°C, while that of coal-fired power plants and blast furnaces is 1,500°C.

[0008] On the other hand, chemical grouting involves injecting a gelling liquid through injection pipes installed in the ground, replacing the pore water between soil particles and solidifying the ground. While chemical grouting was traditionally used as a temporary auxiliary method, recent technological improvements have increased its durability, leading to its use in liquefaction countermeasures and seismic reinforcement work. Among the solution-type grouting materials that offer good durability, there are activated silica colloid systems, and among the suspension-type grouting materials, there is ultrafine particle composite silica. However, activated silica colloid systems use colloidal silica obtained by removing the alkali from water glass with ion exchange resin and then curing it by heat as the main component, which tends to result in high carbon dioxide emissions during the manufacturing process. On the other hand, ultrafine particle composite silica uses granulated blast furnace slag as the main component, and therefore faces the same challenges as the blast furnace slag mentioned above.

[0009] Furthermore, studies are being conducted on producing highly active clinker by mixing ash obtained from burning plants with cement and firing it. However, since cement is used as the base material, it cannot be said that the reduction in carbon dioxide emissions is significant. In addition, a technology is being considered to use a mixture of rice husk ash and cement as a ground improvement material. However, since the improvement strength tends to decrease as the ash replacement rate increases, it is difficult to say that a sufficient pozzolanic reaction is being obtained.

[0010] Conventional technologies related to ground improvement are described, for example, in Patent Document 1 and Non-Patent Document 1. In addition, Patent Document 2 and Non-Patent Document 2 describe conventional technologies related to the effective utilization of seashells. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Patent No. 7578345 [Patent Document 2] Patent No. 5751923 [Non-patent literature]

[0012] [Non-Patent Document 1] Seiji Tomohisa, Kohei Sawa, Nagahide Naito, Shinya Kuroda, Hiroyuki Nakagawa, "A Study on the Strength Characteristics of River Embankment Materials," December 2006, Akashi National College of Technology Research Bulletin [Non-Patent Document 2] Takamune Yaegashi, "Resource Utilization of Seashells and Enhancement of Charcoal Functionality through Integrated Firing Technology (First Report)," 2008, Iwate Prefectural Industrial Technology Center Research Report. [Overview of the project] [Problems that the invention aims to solve]

[0013] As mentioned above, various studies have been conducted on materials used for ground improvement. However, no material has yet been found that can be supplied stably for ground improvement and does not cause environmental problems such as environmental pollution or increased carbon dioxide emissions.

[0014] Therefore, the object of the present invention is to provide a construction material that can be used for structures as well as ground improvement applications, is sustainable and environmentally friendly, and a ground improvement method using the same, by using a material that can be supplied stably and does not cause environmental problems such as environmental pollution or increased carbon dioxide emissions. [Means for solving the problem]

[0015] As a result of their investigations to solve the above problems, the inventors of the present invention have found that the above problems can be solved by using incinerated ash containing silica and metals such as calcium, obtained by burning waste derived from marine or land products, as a material for construction materials.

[0016] In other words, the present invention provides construction materials made from geopolymers derived from land or marine products as environmentally friendly and sustainable materials, by utilizing land products such as agricultural products and marine waste as resources, instead of ordinary Portland cement, blast furnace granulated slag, fly ash, etc., which have environmental problems, environmental burden, and supply sustainability issues. Specifically, agricultural waste includes plants such as rice, wheat, sugarcane, corn, and bamboo, which contain a lot of silica, and cow manure and chicken manure, which contain a lot of calcium. Marine waste includes shells such as scallops and oysters, which contain a lot of metals, such as calcium and magnesium, which is produced when salt is made.

[0017] To recycle these waste materials into construction materials, several problems arise: the chemical composition varies depending on the type of waste, and even within the same type, the degree of deterioration differs depending on the conditions and duration of natural storage. Therefore, to effectively utilize waste as construction materials, individual chemical tests must be conducted, and a composition suitable for the intended purpose must be used. Furthermore, solidification tests must be conducted to confirm that the waste is suitable for use as a construction material. This invention solves these problems and has been completed.

[0018] While incinerated ash from plant-derived waste is used as a soil modifier and concrete additive, an effective formulation for use as a construction material primarily for solidification has not yet been established. Similarly, incinerated ash from seashells is used as a concrete additive, a soil pH adjuster, and a ground solidification agent, but its solidification mechanism differs from that of the present invention. It involves the reaction of the lime obtained from calcination with moisture in the ground to form slaked lime, or the reduction of water content due to the exothermic effect.

[0019] That is, the present invention is a construction material mainly composed of incineration ash obtained by burning waste derived from marine products and / or terrestrial products. Among the incineration ash, the incineration ash of amorphous silica is the main agent, and the Ca-containing incineration ash containing at least Ca is the reactant. It is characterized in that it is used for structural purposes or as a solidifying material in a chemical solution injection method, a high-pressure jet mixing method or a mixing and stirring ground improvement method.

[0020] In the construction material of the present invention, it is preferable that the Ca-containing incineration ash further contains Mg and / or Al.

[0021] In the construction material of the present invention, the incineration ash of amorphous silica is mainly composed of amorphous silica derived from gramineous plants or bamboo. When its combustion temperature is 400°C or higher and lower than 700°C, it is preferably obtained without rapid cooling after combustion or by rapid cooling, or when its combustion temperature is 700°C or higher, it is preferably obtained by rapid cooling after combustion.

[0022] In the construction material of the present invention, the Ca-containing incineration ash is preferably obtained by pulverizing one or more of shells containing Ca, plants containing Mg and / or Al and chicken manure, and sewage sludge, and heating and burning them until no weight loss is observed. In particular, it is more preferable that the construction material contains a mixed powder composed of a mixture of the incineration ash of amorphous silica and the Ca-containing incineration ash and water.

[0023] In the construction material of the present invention, when the mass of the mixed powder is P and the mass of the water is W, it is preferable that the water-powder ratio W / P is in the range of 30 to 1000%. Also, it is preferable that the molar ratio SiO2 / CaO of SiO2 and CaO contained in the mixed powder is in the range of 0.1 to 5.0.

[0024] The construction material of the present invention preferably further contains one or more of the following alkalis (i) to (iii) as an auxiliary agent. (i) An alkaline agent having gypsum and / or MgO as active ingredients. (ii) An alkaline agent containing one or more of Ca salts, Mg salts, Al salts, carbonates, and bicarbonates as active ingredients. (iii) An alkaline agent having one or more of lime, cement, caustic alkali, water glass, and silica colloid as active ingredients.

[0025] In the present invention, the strength of the solidified soil can be adjusted by adjusting the content of MgO and / or Al2O3 in the construction material.

[0026] The construction material of the present invention may be clinker obtained by mixing the waste materials that serve as raw materials for the main agent and the reactant, burning them at 900°C or higher, and then rapidly cooling them.

[0027] The ground improvement method of the present invention is characterized by using the construction materials of the present invention when improving the ground by a chemical injection method, a high-pressure jet mixing method, or a mixing and stirring system ground improvement method. [Effects of the Invention]

[0028] According to the present invention, it is possible to provide a construction material and ground improvement method that are sustainable and environmentally friendly, which can be used for structures as well as ground improvement applications, and which can exhibit strength in ground improvement applications, using materials that can be supplied stably and do not cause environmental problems such as environmental pollution or increased carbon dioxide emissions.

[0029] This invention is also useful from the viewpoint that it can recycle industrial waste derived from marine or land products containing metals such as silica and calcium. [Brief explanation of the drawing]

[0030] [Figure 1] This is an explanatory diagram showing the relationship between the combustion temperature and crystal structure of silica. [Figure 2] This graph shows the results of the thermal analysis of CaCO3. [Figure 3] This is a photographic illustration showing an example of Okinawan sugarcane fiber powder. [Figure 4] This is a photographic diagram showing an example of the powder after firing. [Figure 5] This graph shows the XRD pattern of ash obtained by slow cooling. [Figure 6] This graph shows the XRD pattern of ash after rapid cooling. [Figure 7] This is a photographic illustration showing an example of a scallop shell. [Figure 8] This is a photographic diagram showing an example of scallop shells that have been crushed and then calcined. [Figure 9] This graph shows the TGA analysis results for scallop shells. [Figure 10] This is a photographic diagram showing the results of the solidification confirmation test. [Figure 11] This graph shows the results of a uniaxial compression test. [Figure 12] This is a photographic diagram showing the situation after the compression test. [Figure 13] This graph shows the relationship between wood age and unconfined compressive strength. [Modes for carrying out the invention]

[0031] The embodiments of the present invention will be described in detail below. The present invention relates to a construction material whose main component is incinerated ash obtained by burning waste derived from marine and / or land products, wherein amorphous silica incinerated ash is used as the main component and Ca-containing incinerated ash containing at least Ca is used as the reactant. The construction material of the present invention is used not only in structures but especially in ground improvement applications, and specifically, in structural applications or as a solidifying agent in chemical grouting methods, high-pressure jet mixing methods or mixed ground improvement methods.

[0032] Furthermore, the construction material of the present invention can be described as a geopolymer that uses marine or land waste, which is a sustainable material with a low environmental impact, instead of blast furnace slag or fly ash. Geopolymer is a general term for silicate complexes produced by mixing activated fillers such as blast furnace slag or fly ash with alkaline solutions such as water glass or sodium hydroxide. When blast furnace slag is used, amorphous calcium silicate is produced, and when fly ash is used, amorphous aluminosilicate is produced. Concrete using geopolymer does not use any cement, so carbon dioxide emissions during cement production can be reduced, and it has excellent compressive strength, acid resistance, and durability, and also has the function of immobilizing harmful metals such as heavy metals during the hardening process, so it is expected to have expanded applications in acidic environments and in the field of environmental remediation.

[0033] Here, while ground improvement methods using plant incineration ash or papermaking incineration ash are described, for example, in the specification of Patent Document 1, which is a prior invention by the present applicant, the invention described in Patent Document 1 is a ground injection method for protecting concrete structures from air raids, and is not a technology related to the resource recovery of plant incineration ash, nor does it show specific processing methods or formulations for optimal resource recovery. Furthermore, Patent Document 1 does not disclose any problems in its practical application or specific solutions to those problems. Moreover, papermaking incineration ash is an artificial material and does not deteriorate or vary in quality depending on the disposal period and conditions in the natural phenomena of marine or land products, as is the case with the present invention. The present applicants have conducted research and development on the resource recovery of the aforementioned marine or land product-derived waste for ground improvement purposes, have identified the problems and solutions, and have invented a specific method.

[0034] First, the amorphous silica incinerated ash used as the main component in the construction material of the present invention is derived from land products such as rice and wheat husks, grasses such as sugarcane and corn, and edible plant waste containing a large amount of amorphous silica, such as bamboo. In the present invention, incinerated ash containing a large amount of amorphous silica obtained by burning these can be used. In recent years, bamboo overgrowth has become a problem in neglected forests, but using such bamboo as a material for the construction material of the present invention would be useful as a countermeasure against bamboo overgrowth. Amorphous calcined silica can be obtained by burning these plants at an appropriate temperature and then cooling them.

[0035] The most important element in this invention is obtaining amorphous silica from silica-containing plants. While it is known that silica in grasses, which are rich in silica, is amorphous, amorphous silica can be obtained through appropriate processing. Specifically, as shown in Figure 1, it is known that the crystalline structure differs depending on the temperature and time of combustion and the cooling method after combustion. In this invention, since amorphous silica is the main component, it is necessary to burn it within a predetermined temperature range, and if it is burned at a higher temperature, rapid cooling is necessary.

[0036] Specifically, amorphous silica incinerated ash can be obtained without rapid cooling after combustion if the combustion temperature is between 400°C and 700°C, for example, between 400°C and 500°C, but rapid cooling is more preferable. Furthermore, if the combustion temperature is 700°C or higher, it can be obtained by rapid cooling after combustion. In this invention, rapid cooling means rapidly cooling the incinerated ash by either immersing it in water immediately after combustion or by a water cooling method in which pressurized water is sprayed onto the incinerated ash. By processing it in this way, amorphous calcined silica can be efficiently obtained.

[0037] As shown in Table 1, the chemical components contained in the calcined ash vary greatly depending on the type of plant. Therefore, it is important to appropriately set the type and amount of the alkaline stimulant reagent, as described later.

[0038] [Table 1]

[0039] Next, the Ca-containing incinerator ash used as a reactant in the construction material of the present invention acts as an alkaline stimulant and contains at least Ca, thereby enabling a hardening effect. Preferably, the Ca-containing incinerator ash further contains Mg and / or Al, which can improve the hardening properties.

[0040] Specifically, Ca-containing incinerated ash is derived from marine or land-based waste such as seashells rich in Ca, including oysters and scallops, as well as plants and chicken manure rich in Mg and Al, and sewage sludge. It is obtained by crushing one or more of these materials into powder and heating and burning it until no further weight loss is observed.

[0041] In other words, as shown in Table 2, from the viewpoint of stability of component composition, CaO derived from seashells is highly effective as a Ca-containing incinerated ash, but chicken manure and cow manure can also be used. Furthermore, the solidification characteristics can be modified by adding metals that act as crosslinking points for geopolymers, such as bittern or incinerated sewage sludge ash.

[0042] [Table 2]

[0043] To convert CaCO3 from seashells, cow dung, chicken manure, etc., used in Ca-containing incineration ash into CaO, combustion at around 900°C is sufficient, as shown in Figure 2.

[0044] When using the construction material of the present invention, an appropriate amount of Ca-containing incinerated ash, such as CaO derived from seashells, is added to the amorphous silica incinerated ash, which is the main component, as a reactant that acts as an alkaline stimulant. By adding water to this amorphous silica incinerated ash and Ca-containing incinerated ash, a pozzolanic reaction occurs, and a gelled product mainly of calcium silicate complex can be obtained, and a hardened body can be obtained. The amount of Ca-containing incinerated ash to be added is determined according to the amorphous silica content in the incinerated ash containing amorphous silica, and the pozzolanic reaction occurs when an appropriate amount is added.

[0045] The specific reaction begins with the calcination of seashells, which decarboxylates the main component of the shell, CaCO3, to obtain CaO. When this is mixed with incinerated ash from plant waste and water, the CaO becomes Ca(OH)2, and the pH becomes approximately 12. This alkaline stimulus causes the amorphous silica contained in the incinerated ash to dissolve, forming particles of about 1 nm. Along with this dissolution, metallic ions such as calcium, aluminum, and magnesium are released from the incinerated ash. When the silica and metallic ions reach a certain concentration, the silica crosslinks via the metallic ions, and this reaction polymerizes, forming a silicate complex. In the case of calcium-based silicates, tobermorite (Ca5(Si6O) 18 H2)·4H2O), and in aluminum-based systems, kaolinite (Al4Si4O 10 (OH)8) In magnesium-based systems, it forms a semicrystalline form of dolomite (CaMg(CO3)2).

[0046] Thus, this invention recycles waste generated during daily activities such as food production, and there is little risk of raw material depletion. Furthermore, since the incinerated ash from plant waste can be obtained from biomass power generation, and the combustion temperature for each raw material is around 900°C, the carbon dioxide emissions generated during implementation are significantly lower compared to the carbon dioxide emissions generated in the process of obtaining cement, blast furnace slag, and fly ash.

[0047] As mentioned above, when burning silica-containing plant waste at 400°C to less than 700°C to obtain amorphous silica incineration ash, rapid cooling after combustion is not necessary. However, to obtain Ca-containing incineration ash, it is necessary to burn CaCO3 derived from seashells, etc., to convert it to CaO, which complicates the process. In such cases, if the composition of the ash obtained by combustion can be known in advance, the construction material of the present invention is effective in obtaining clinker by mixing the waste materials that will serve as the main agent and the reactant, burning them at 900°C or higher, and then rapidly cooling them. That is, clinker can be obtained by mixing plant waste and Ca-containing waste in a predetermined weight ratio, burning them at 900°C or higher, and then rapidly cooling them. In this case, by adding chicken manure or bittern containing SO3, CaCO3 becomes CaSO4. This CaSO4 has the effect of contributing to the initial strength increase.

[0048] The construction material of the present invention may contain a mixed powder consisting of a mixture of amorphous silica incinerated ash and Ca-containing incinerated ash, and water. In the present invention, when the mass of the mixed powder consisting of amorphous silica incinerated ash and Ca-containing incinerated ash is P and the mass of water is W, the water-to-powder ratio W / P is preferably in the range of 30 to 1000%, more preferably in the range of 40 to 1000%, and particularly preferably in the range of 50 to 800%. Furthermore, the molar ratio of SiO2 to CaO contained in the above mixed powder, SiO2 / CaO, is preferably in the range of 0.05 to 10.0, and more preferably in the range of 0.1 to 5.0, from the viewpoint of reliably obtaining a hardening effect. This molar ratio of SiO2 / CaO of the mixed powder can be determined, for example, by XRF (X-ray Fluorescence) analysis.

[0049] In the construction material of the present invention, the strength of the consolidated soil can be adjusted by adjusting the content of MgO and / or Al2O3, and consequently, the rate of strength development and the rate of strength rise can be adjusted.

[0050] (Example of experiment) (Preparation of incinerated sugarcane fiber powder ash (SCBA)) First, we will explain in detail the production of amorphous silica by calcining plant waste such as agricultural products. The Okinawan sugarcane fiber powder shown in Figure 3 was heated at a rate of 10°C / min to 400-900°C and then burned in a high-temperature electric furnace for 6 hours while maintaining that temperature. After that, the incinerated ash obtained from the combustion, shown in Figure 4 (hereinafter also referred to as "SCBA"), was subjected to slow cooling or rapid cooling. Slow cooling refers to allowing the incinerated ash obtained from combustion to cool at room temperature (approximately 20°C), while rapid cooling is a method of spraying cooling water at high pressure immediately after removing the incinerated ash obtained from combustion from the furnace, and is a process used in the production of blast furnace granulated slag.

[0051] The purpose of rapid cooling is to generate amorphous SiO2, which is necessary for geopolymer production. Silica structures include quartz, tridymite, cristobalite, and amorphous silica, and this structure is determined by the combustion temperature, pressure, and cooling time. As a general trend, the higher the combustion temperature and pressure and the longer the cooling time, the higher the crystallinity in the order of quartz > tridymite > cristobalite > amorphous silica, and of these, amorphous (non-crystalline) silica has the highest reactivity. Note that SiO2 incorporated into plants is basically in an amorphous state.

[0052] Figure 5 shows the XRD (X-ray diffraction) observation results for different combustion temperatures under slow cooling. Below 700°C, the material basically becomes amorphous without the need for rapid cooling, but above 800°C, the formation of cristopalite was observed.

[0053] Figure 6 shows the XRD observation results for different combustion temperatures after rapid cooling. It can be confirmed that the material is in an amorphous state at all temperatures.

[0054] (Preparation of scallop shell incineration ash (SS ash)) Next, we will explain in detail the production of calcium-containing incinerated ash by calcining seashell waste. Scallop shells (hereinafter also referred to as "SS") shown in Figure 7 were ground into a powder by grinding as a pretreatment. This powder was heated in a high-temperature electric furnace at a heating rate of 10°C / min to 900°C and burned for 2 hours while maintaining that temperature. After that, the incinerated ash shown in Figure 8 obtained from the combustion was slowly cooled. Here, Figure 9 shows the results of TGA (Thermogravimetric Analysis) performed on scallop shells that contain a large amount of CaCO3. When the reference temperature exceeded 600°C, the weight decreased rapidly due to an endothermic reaction, and when it reached approximately 740°C, no further weight loss was observed. Therefore, in order to obtain CaO, the combustion temperature needs to be set to 740°C or higher.

[0055] Furthermore, to efficiently obtain CaO by burning oyster shells, it is necessary to burn them at 900°C or higher for one hour. In this experiment, the combustion temperature was set to 900°C and the combustion time to 2 hours. The combustion temperature and combustion time required to obtain CaO from chicken eggshells are the same as for oyster shells, but the pre-treatment grinding process is easier to perform with chicken eggshells.

[0056] (Solidification test) A solidification test was conducted using the two types of ash obtained from the combustion experiment described above: SCBA and SS ash. The components of SCBA and SS are shown in Table 3.

[0057] [Table 3]

[0058] The purpose of the solidification test is to understand the effects of the presence or absence of SCBA and differences in moisture content on solidification. Table 4 shows the sample preparation conditions for the solidification test. For Case 1-1 and Case 1-2, 2.1g of SS ash and 2.9g of SCBA were mixed to a total of 5.0g. This mixing ratio was chosen so that the overall proportion of the components would be similar to the chemical composition of blast furnace slag (hereinafter also referred to as "BS") shown in Table 5. Table 5 also shows the chemical composition of the mixed incinerated ash. In contrast, for Case 1-3 and Case 1-4, SCBA was not included, and only SS ash was mixed. Distilled water (W) was then added to achieve two different water-to-powder ratios (W / P = 120% and W / P = 200%), and the mixtures were mixed in beakers. After that, stirring was performed using a metal spoon. For these four cases, the solidification test was conducted after 7 days.

[0059] [Table 4]

[0060] [Table 5]

[0061] Figure 10 shows photographs of each case after 0 days of curing (immediately after mixing). The solidification evaluation method involved inserting a bamboo skewer into the sample in the beaker, shaking the beaker by hand, and visually checking whether the hole made by the bamboo skewer was filled in. If the hole was completely filled, it was marked "×", if the hole remained but was shallow, it was marked "△", if the hole remained, it was marked "〇", and if it was judged to have solidified visually before inserting the bamboo skewer it was marked "◎".

[0062] The solidification evaluation for Case 1-1 and Case 1-2, which included SCBA, was "◎". In Case 1-1, the sample was so hard that it was impossible to insert the bamboo skewer all the way to the bottom. Next, in Case 1-2, less force was required to insert the bamboo skewer compared to Case 1-1, allowing it to reach the bottom of the beaker. Also, water came out of the hole created when the bamboo skewer was inserted, suggesting a high water content. On the other hand, the solidification evaluation for Case 1-3, which did not include SCBA, was "〇", while the solidification evaluation for Case 1-4 was "△". In Cases 1-3 and 1-4, less force was required to insert the bamboo skewer compared to Cases 1-1 and 1-2. Also, the resistance when inserting the bamboo skewer in Case 1-4 felt weaker than in Case 1-3. This is thought to be due to the higher water content of the sample in Case 1-4. Furthermore, it was found that the presence or absence of SCBA significantly affects the solidification process. In this test, solidification was determined using bamboo skewers, but accurate measured values ​​can also be obtained using the Yamanaka penetration test or a bender element.

[0063] (Uniaxial compression test) Next, we will describe the uniaxial compression test of the improved soil according to the present invention, which was prepared based on the results of the solidification test described above. Table 6 shows the conditions for preparing the test specimens. SS ash and SCBA used in the solidification test were employed, and the mass of the mixed powder obtained by mixing these two ashes was defined as P. The test specimens were prepared with a diameter of 15 mm and a height of 30 mm using silica sand No. 6, with a relative density of 60%. The amount of construction material added was determined by two different ratios P / S, where S is the mass of silica sand No. 6. Furthermore, the water-to-powder ratio (W / P) of the construction material was set to two levels. The test specimens were prepared by mixing and compaction, with a curing period of 7 days. Subsequently, a uniaxial compression test was conducted at a compression rate of 0.3 mm / min.

[0064] [Table 6]

[0065] Figure 11 shows the results of the compression test. The unconfined compressive strength was 71 kPa for Case 2-1, 17 kPa for Case 2-2, 954 kPa for Case 2-3, and 246 kPa for Case 2-4. Figure 12 shows photographs of each case after the unconfined compression test.

[0066] The results of the unconfined compression test revealed that Cases 2-3 and 2-4, which had higher amounts of construction material added, had higher maximum stresses compared to Case 2-2, which had a lower amount of added material. Furthermore, comparing Cases 2-3 and 2-4, it was found that Case 2-3, which had a lower W / P value, had a higher unconfined compressive strength. From the above, it was found that the solidification strength differs depending on the material composition, water content, and water / solids ratio.

[0067] The construction material of the present invention, obtained by burning and cooling the aforementioned waste materials, contains CaO, SiO2, Al2O3, MgO, and Fe2O3, and as can be seen from Tables 3 and 5, it has a chemical composition similar to that of blast furnace slag. Therefore, in the construction material of the present invention, it is thought that if an alkaline agent is added as an auxiliary agent in addition to water to the incinerated ash of amorphous silica as the main component and the Ca-containing incinerated ash as the reactant, greater strength can be obtained through a hydration reaction.

[0068] As an alkaline agent that produces hydration bonds, (i) An alkaline agent having gypsum and / or MgO as active ingredients. (ii) An alkaline agent containing one or more of Ca salts, Mg salts, Al salts, carbonates, and bicarbonates as active ingredients. (iii) An alkaline agent having one or more of lime, cement, caustic alkali, water glass, and silica colloid as active ingredients. These can be listed, and one or more of these can be used.

[0069] Therefore, the alkaline agent was added to the combination of SS ash and SCBA, and the effect of the alkaline agent was confirmed in a solidification test. As a result, as shown in Table 7, evaluations that were △ or × became ○ or ◎, showing a significant improvement.

[0070] [Table 7]

[0071] As shown in Table 7, it was found that solidification performance could be improved by changing the chemical composition. Therefore, various incinerator ashes shown in Table 2 were mixed with SCBA, and the effect of chemical composition on solidification characteristics was investigated. For comparison, a solidified body using ordinary Portland cement (OPC) was also prepared.

[0072] Table 8 shows the composition of the solidifying agent. The water-to-powder ratio (W / P) of the solidifying agent was set to 100%, and the test specimens were prepared by mixing soil and solidifying agent in a volume ratio of 1:1. The soil used for the test specimens was a mixture of silica sand No. 5 and clay in a mass ratio of 7:3.

[0073] [Table 8]

[0074] Figure 13 shows the relationship between age and uniaxial compressive strength. At 28 days of age, the uniaxial compressive strength of specimens using geopolymer solidification materials derived from land or marine products (Cases 4-1 to 4-3) was higher than that of specimens using OPC (Case 4-4). This is likely because OPC had a lower ratio of SiO2 to Al2O3, CaO, and MgO compared to geopolymers derived from land or marine products, and therefore could not form sufficient silicate complexes. When comparing geopolymers derived from land or marine products, Case 4-2, which contained the most MgO, showed the highest uniaxial compressive strength.

[0075] The uniaxial compressive strength at 28 days of age for Case 4-1 and Case 4-2 is higher than that of OPC (Case 4-4), although the uniaxial compressive strength in the early stages of age tends to be lower. However, in Case 4-3, which contains a large amount of Al2O3, the uniaxial compressive strength is higher than that of OPC from the initial stage up to 28 days of age.

[0076] Thus, the differing rates and speeds of strength development are thought to be due to the ion exchange action of the soil and the proportions of Al2O3, CaO, and MgO contained in the solidifying agent, as well as their respective ionization tendencies. Therefore, it is desirable to determine an appropriate mixing ratio according to the desired strength and purpose of the improvement.

[0077] The ground improvement method of the present invention uses the construction materials of the present invention when improving the ground by chemical injection, high-pressure jet mixing, or mixing and stirring ground improvement method. Since it uses construction materials that can be supplied stably and do not cause environmental problems such as environmental pollution or increased carbon dioxide emissions, it is excellent in terms of sustainability and environmental friendliness, and is also useful from the viewpoint of resource recovery of waste.

Claims

1. A method for producing a solidifying agent comprising incinerated ash obtained by burning waste derived from marine and / or land products, wherein incinerated ash containing amorphous silica acts as the main agent and incinerated ash containing at least Ca acts as the reactant to achieve a hardening effect, the method comprising the main agent and the reactant, The aforementioned solidifying agent is used for structural purposes, or in chemical grouting, high-pressure jet mixing, or mixed ground improvement methods. When the aforementioned land-derived waste is burned at a combustion temperature of 400°C or higher but less than 700°C, rapid cooling after combustion is either performed or not performed, or when it is burned at a combustion temperature of 700°C or higher, rapid cooling is performed after combustion. A method for producing a solidifying agent, characterized by heating and burning a powder obtained by crushing one or more of the following until no further weight loss is observed: seashells containing Ca, plants and chicken manure containing Mg and / or Al, and sewage sludge, to obtain incinerated ash containing at least Ca.

2. The method for producing a solidifying agent according to claim 1, wherein the incinerated ash containing at least Ca further contains Mg and / or Al.

3. A method for producing a solidifying agent according to claim 1, wherein the aforementioned land-derived waste is mainly composed of waste from grasses or bamboo.

4. A method for producing a solidifying material according to claim 1, wherein the solidifying material comprises a mixed powder consisting of incinerated ash containing amorphous silica and incinerated ash containing at least Ca, and water, and satisfies the following conditions. 1) When the mass of the mixed powder is P and the mass of the water is W, the water-to-powder ratio W / P is in the range of 30 to 1000%. 2) SiO contained in the mixed powder ２ The molar ratio of CaO to SiO ２ The value of / CaO is in the range of 0.1 to 5.

0.

5. A ground improvement method using a solidified material obtained by a method for manufacturing a solidified material according to any one of claims 1 to 4, wherein the solidified material contains MgO and / or Al ２ O ３ A ground improvement method characterized by adjusting the strength of the consolidated soil by adjusting the content of [a certain substance].

6. A ground improvement method characterized by using a solidified material obtained by a method for manufacturing a solidified material according to any one of claims 1 to 4, when improving the ground by a chemical injection method, a high-pressure jet mixing method, or a mixing and stirring ground improvement method.

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