Construction method for underwater structures using ash mortar

Abstract

To provide an ash mortar that can secure a normal slope in a normal slope part of a submerged structure without using an additive and can ensure fluidity required for pumping during construction, and to provide a method for constructing an underwater structure using the ash mortar.SOLUTION: An ash mortar is a mixture of a solidification material, a coal ash and water to form an underwater structure 10A having a normal slope part 3A. The coal ash is composed of: a fly ash as a main component; and a clinker ash as a secondary component.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention uses fly ash and clinker ash, which are coal ash. Ash This invention relates to a method for constructing underwater structures using mortar. [Background technology]

[0002] Coal ash, a by-product of coal-fired power generation, can be broadly divided into fly ash and clinker ash. When pulverized coal is burned in a boiler at a coal-fired power plant, molten ash particles float in the high-temperature combustion gas. As the temperature drops at the boiler outlet, they turn into fine spherical particles that are collected by an electrostatic precipitator. This is called fly ash. Clinker ash is produced when coal ash particles generated by combustion in the boiler aggregate to form porous lumps that fall and accumulate in a clinker hopper (water tank) at the bottom of the boiler. These lumps are then crushed into sand using a crusher. After being dehydrated in a dehydration tank or similar, the particle size is adjusted using a sieve or similar device depending on the application (see Non-Patent Document 1). Fly ash consists of fine spherical particles (see Non-Patent Document 2). Clinker ash is gravelly and porous, with excellent water retention, drainage, and breathability, and its particles are mostly fine gravel and coarse sand, with a particle size distribution similar to that of sand (see Non-Patent Document 3). In terms of chemical composition, the main components of both fly ash and clinker ash are silica and alumina, and there is not much difference between the two.

[0003] Some of this coal ash is disposed of in landfills as waste, but much of it is effectively used as an admixture for cement and concrete, or as various aggregates in civil engineering works. One of the effective utilization technologies is fly ash mortar. In port civil engineering works, fly ash mortar is used as a fill material for revetments, backfill material, and covering material for backfill material.

[0004] Patent Document 1 discloses that the coal ash-based material used for landfilling at controlled offshore waste disposal sites is made by filling a powdered mixture of fly ash and cement into a water-permeable, dustproof bag, which solidifies after being dropped into water, thereby realizing ease of construction and space savings in the manufacturing yard (abstract). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-190086 [Non-patent literature]

[0006] [Non-Patent Document 1] "Coal Ash Generation and Production Process" Japan Fly Ash Association http: / / www.japan-flyash.com / process.html [Non-patent document 2] "Chemical and Physical Properties of Fly Ash" Japan Fly Ash Association http: / / www.japan-flyash.com / fchemiphysi.html [Non-patent document 3] "Chemical and Physical Properties of Clinker Ash" Japan Fly Ash Association http: / / www.japan-flyash.com / cchemiphysi.html Summary of the Invention [Problem to be solved by the invention]

[0007] However, when using fly ash mortar as a backfill or covering material, the high fluidity of fly ash mortar poses the problem of not being able to ensure the required slope. To solve this problem, technologies have been proposed that use additives such as thickeners, anti-separation agents, and hardening accelerators to ensure slope, but this raises concerns about increased costs. Furthermore, when using fly ash mortar in marine areas, it may be necessary to obtain permission to use additives from the relevant authorities, which can be cumbersome. Furthermore, in actual construction, it is necessary to ensure the fluidity required for pumping. Currently, when using fly ash mortar as a backfill or covering material, fly ash is used alone without mixing in clinker ash.

[0008] The coal ash utilization material in Patent Document 1 is a powder mixture made by mixing fly ash and cement, which is filled into a water-permeable, dust-proof bag.The mixture must be filled into the bag, which requires a filling process and materials (bags), making the process complicated and increasing material costs, which is disadvantageous in terms of cost.

[0009] In view of the problems of the prior art as described above, the present invention is capable of ensuring the slope gradient of the slope portion of an underwater structure without using additives, and also capable of ensuring the fluidity required for pumping during construction. Ash The object of the present invention is to provide a method for constructing underwater structures using mortar. [Means for solving the problem]

[0010] To achieve the above objectives Used in the construction of underwater structures The ash mortar is a mixture of a solidifying agent, coal ash, and water for forming underwater structures with sloped sections, and the coal ash is composed of fly ash as a main component and clinker ash as a secondary component.

[0011] This ash mortar, which is composed of coal ash primarily composed of fly ash and secondary clinker ash, can ensure the required slope gradient in the sloped sections of underwater structures without the use of additives. Adding clinker ash, which has a relatively larger particle size than fly ash, to fly ash as aggregate facilitates the formation of a particle skeleton in the ash mortar, making it easier to form a slope gradient. This improves slope gradient formation characteristics, enabling the required slope gradient to be achieved in the sloped sections without the use of additives. The blend ratio of fly ash to clinker ash, the primary component, exceeds 50%.

[0012] The fly ash and the clinker ash are mixed in a mixing ratio of 9:1 to 8:2. do. The above-mentioned blending ratio is the ratio of fly ash and clinker ash to the total weight of fly ash and clinker ash, and the same applies to the following explanation.

[0013] The solidifying material is preferably one, two, or all of blast furnace slag cement, ordinary Portland cement, and fly ash cement.

[0014] The amount of the solidifying material mixed is 50 kg / m 3 ~200kg / m 3 It is preferable that the range is within the range of

[0015] The flow value of the ash mortar after mixing is When the blending ratio is 9:1 At least 88mm , when the blending ratio is 8:2, it is at least 92 mm This ensures the fluidity required for pumping ash mortar.

[0016] The water-to-powder ratio obtained by dividing the weight of the water by the total weight of the solidification material and the coal ash is within the range of 0.350 to 0.439. do.

[0017] The ash mortar can be used as a backfill material for the underwater structure or as a coating material for the backfill material.

[0018] The method for constructing an underwater structure to achieve the above object is a method for constructing an underwater structure having a sloped slope portion using ash mortar obtained by mixing coal ash consisting of fly ash as a main component and clinker ash as a secondary component, a solidifying agent, and water, the fly ash and the clinker ash being mixed in a mixing ratio of 9:1 to 8:2, the method comprising: forming the sloped slope portion using the ash mortar in which the solidifying agent, the coal ash, and the water are mixed so that the water-to-powder ratio, obtained by dividing the weight of the water by the total weight of the solidifying agent and the coal ash, is within a range of 0.350 to 0.439. When constructing, the water-powder ratio is adjusted within the range so that the slope of the slope portion is within the target value within the range of 1:1.2 to 1:4.4. It is something.

[0019] According to this method for constructing underwater structures, the slope is constructed using ash mortar made by mixing solidifying material, coal ash (fly ash and clinker ash), and water so that the water-to-powder ratio is within the range of 0.350 to 0.439. When the water-powder ratio is adjusted within the range so that the normal gradient is a target value within the range of 1:1.2 to 1:4.4, By doing so, it is possible to ensure a slope gradient in the range of 1:1.2 to 1:4.4 in the slope gradient portion without using any additives.

[0020] In the above-mentioned method for constructing an underwater structure, it is preferable that the flow value of the ash mortar when pumping the ash mortar into water to construct the sloped section is equal to or greater than the lower limit value that can ensure the fluidity required for the pumping.

[0021] Furthermore, it is preferable to carry out a mixing test and an underwater casting test in advance on ash mortar prepared by mixing the solidifying agent, coal ash, and water in a plurality of predetermined ratios to determine a first relationship between the flow value of the ash mortar and the slope gradient of the slope gradient section, and a second relationship between the flow value and the water-powder ratio, and then determine the water-powder ratio from the design value of the slope gradient based on the first and second relationships, and use ash mortar mixed based on the determined water-powder ratio.

[0023] It is preferable to construct the slope portion by pumping the ash mortar into water.It is preferable that the sloped portion is a backfill portion of the underwater structure or a covering portion of the backfill portion. [Effects of the Invention]

[0024] The present invention Ashes According to the method for constructing underwater structures using mortar, the slope of the sloped portion of the underwater structure can be ensured without using additives, and the fluidity required for pumping during construction can be ensured. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a side cross-sectional view showing an example of an underwater structure to which the ash mortar according to this embodiment can be applied as a backfill material. [Figure 2] FIG. 1 is a side cross-sectional view showing an example of an underwater structure to which the ash mortar according to this embodiment can be applied as a coating material for a backfill material. [Figure 3] FIG. 1 is a schematic diagram showing the underwater casting experiment conditions used in this experimental example. [Figure 4] 1 is a graph showing the relationship between the flow value and the casting gradient for ash mortar using only fly ash (FA) of this comparative example. [Figure 5] 1 is a graph showing the relationship between the flow value and the pouring gradient for ash mortar in this experimental example, in which fly ash (FA) and clinker ash (CA) are mixed in a mixing ratio of 9:1. [Figure 6] 6 is a graph showing the relationship between the flow value and the water-to-powder ratio for ash mortar mixed at a mixing ratio of 9:1, similar to that of FIG. 5. [Figure 7] 1 is a graph showing the relationship between the flow value and the pouring gradient for ash mortar in this experimental example, in which fly ash (FA) and clinker ash (CA) are mixed in a mixing ratio of 8:2. [Figure 8] 8 is a graph showing the relationship between the flow value and the water-to-powder ratio for ash mortar mixed at a mixing ratio of 8:2, similar to that of FIG. 7. [Figure 9] 10 is a photograph showing the appearance of a roughly conical cone-shaped peak formed in the underwater casting experiment of this experimental example. DETAILED DESCRIPTION OF THE INVENTION

[0026] The following describes an embodiment of the present invention. Ash mortar according to this embodiment can be produced by mixing and kneading a solidifying agent, coal ash, and water. The coal ash is composed of fly ash as a main component and clinker ash as a secondary component, and is suitable for forming underwater structures with sloped sections.

[0027] The blending ratio of fly ash to clinker ash exceeds 50%, but preferably the blending ratio of fly ash to clinker ash is within the range of 9: 1 to 8: 2. This range roughly corresponds to the ratio of the discharge amounts of fly ash, which is coal ash generated and discharged as a by-product in coal-fired power generation, to clinker ash, and therefore can contribute to the efficient and effective utilization of fly ash and clinker ash.

[0028] The solidifying agent may be one, two or all of blast furnace slag cement, ordinary Portland cement and fly ash cement, and the mixing amount of such solidifying agent is 50 kg / m 3 ~200kg / m 3 is within the range.

[0029] In the ash mortar, the water-to-powder ratio obtained by dividing the weight of water by the total weight of the solidifying material and coal ash is preferably within the range of 0.350 to 0.439.

[0030] In the ash mortar of this embodiment, the clinker ash particles are mostly fine gravel and coarse sand, with a particle size distribution similar to that of sand and a relatively large particle size compared to fly ash. Adding clinker ash as aggregate to fly ash facilitates the formation of a particle skeleton. This facilitates the formation of slope gradients in the ash mortar, improving slope gradient formation characteristics and enabling the desired slope gradient to be achieved in sloped sections. By using coal ash consisting primarily of fly ash and secondary clinker ash, the desired slope gradient can be achieved in sloped sections of underwater structures without the use of additives.

[0031] The ash mortar of this embodiment is preferably used as a backfill material for underwater structures or as a covering material for backfill material. The backfill portion and covering portion of the backfill portion of the underwater structure to which the ash mortar of this embodiment is applied will be described with reference to Figures 1 and 2. Figure 1 is a side cross-sectional view showing an example of an underwater structure to which the ash mortar of this embodiment can be applied as a backfill material. Figure 2 is a side cross-sectional view showing an example of an underwater structure to which the ash mortar of this embodiment can be applied as a covering material for backfill material.

[0032] As shown in Figure 1, the underwater structure 10A according to this embodiment comprises a gravity caisson 1, a mound 2 constructed on the water bottom G using rubble and on which the caisson 1 is installed, a backfill section 3 constructed on the back side (shore side) of the caisson 1 so as to have a predetermined slope gradient, and backfill soil 4 constructed from earth and sand further on the shore side of the backfill section 3, and can be used to form, for example, a revetment structure or a quay wall structure. By using the ash mortar of this embodiment as the backfill material for constructing the backfill section 3, it is possible to construct a backfill section 3 having a slope gradient section 3a with a predetermined slope gradient.

[0033] The underwater structure 10B in Fig. 2, like that in Fig. 1, comprises a caisson 1, a mound 2, a backfill section 3, and backfill soil 4, and can be used to form, for example, a revetment structure or a quay wall structure. The backfill section 3 is constructed from backfill stones such as crushed stone, and a covering section 5 is constructed by covering the backfill section 3 with a covering material. By using the ash mortar of this embodiment as the covering material for constructing the covering section 5, it is possible to construct a covering section 5 having a slope gradient section 5a with a predetermined slope gradient. In addition, a sand control sheet 6 is partially placed on the shoulder section at the upper end of the backfill section 3 on the shore side.

[0034] When the backfill section 3 in Figure 1 and the covering section 5 of the backfill section 3 in Figure 2 are constructed using the ash mortar of this embodiment, the water-to-powder ratio of the ash mortar can be adjusted within the range of 0.350 to 0.439 to construct the backfill section 3 in Figure 1 and the covering section 5 in Figure 2 so that the slope gradient sections 3a, 5a are within the range of 1:1.2 to 1:4.4. In other words, the water-to-powder ratio of the ash mortar is adjusted within the range of 0.350 to 0.439 so that the slope gradient sections 3a, 5a in the backfill section 3 in Figure 1 and the covering section 5 in Figure 2 are within the target slope gradient range of 1:1.2 to 1:4.4.

[0035] The backfill section 3 in Figure 1 and the covering section 5 in Figure 2 can be constructed by pumping the ash mortar of this embodiment underwater. However, the flow value of the ash mortar must be high enough to ensure the fluidity required for pumping. In this case, if the coal ash is fly ash alone, a particle skeleton can be formed by the fly ash alone. However, this requires a small void ratio (lower water content). As the water content decreases, the consistency of the fly ash decreases, making pumping difficult. In contrast, by blending fly ash and clinker ash as coal ash, as in this embodiment, the particle skeleton is easily formed. This eliminates the need to reduce the void ratio (lower water content), maintains the flow value, ensures fluidity, and facilitates pumping. Furthermore, adding clinker ash to the fly ash reduces the apparent liquid limit (wl) of the fly ash, which is advantageous in terms of ensuring fluidity.

[0036] The relationship between pumpability and flow value (vane shear strength) varies depending on the pump capacity, but assuming the use of general-purpose equipment used in civil engineering works, the lower limit of the flow value is about 88 mm for ash mortar made with a mixture of fly ash and clinker ash in a 9:1 ratio, and about 92 mm for ash mortar made with the same mixture in an 8:2 ratio. Also, when focusing on ensuring workability in water (non-separation in water, fluidity), the above figures become the lower limit of the flow value, being neither too hard nor too soft.

[0037] According to this embodiment, the ash mortar is required to have improved slope formation characteristics and to have fluidity for pumping. Therefore, the former must be hard enough to ensure a pouring gradient of 1:1.2, and the latter must be fluid (soft enough) to allow pumping. However, by adding clinker ash to the fly ash, it is possible to facilitate the formation of a particle skeleton in the ash mortar, thereby improving the slope formation characteristics without simply hardening the ash mortar (reducing its fluidity).

[0038] Furthermore, in the construction method using water-permeable, dustproof bags filled with a powder mixture of fly ash and cement, as in Patent Document 1, it is necessary to stack a large number of bags in the backfill area, etc., which increases construction costs. However, according to this embodiment, the ash mortar is pumped and poured underwater, thereby achieving cost reductions.

[0039] (Experimental example) Next, the present invention will be explained by way of experimental examples. In these experimental examples, several types of ash mortar were prepared by mixing fly ash and clinker ash at mixing ratios of 9:1 and 8:2 with cement and seawater at different mixing ratios, and a mixing test was carried out to measure the flow value immediately after mixing. The cement used was blast furnace slag cement type B, ordinary Portland cement, or fly ash cement, and the mixing amount was 50 kg / m. 3 ~200kg / m 3The flow test was conducted based on Cylinder Flow Test: Test Method 313 (NEXCO Test Methods, Part 3, Concrete-related Test Methods). In addition, underwater casting experiments were conducted on a real-scale scale using ash mortar with several mix proportions determined from the above mix proportion tests, as shown in Figure 3. As shown in Figure 3, the ash mortar was cast from a hose into the water in a tank, forming an approximately conical peak at the bottom of the tank as shown in Figure 9, and the casting gradient was measured.

[0040] As a comparative example, the relationship between the flow value obtained from a mix test for ash mortar made only with fly ash (FA) and the placement gradient obtained from an underwater casting experiment is shown in Figure 4. In this comparative example, the fluidity was too low to perform the experiment with a sample with a flow value of around 85 mm, but from the approximate curve in Figure 4, which was an experiment using a mix with high fluidity, the flow value that would result in a placement gradient of 1:1.2 is estimated to be 80 mm. However, a flow value of 80 mm does not ensure the fluidity required for pumping, and from the perspective of pumpability, ash mortar made only with fly ash cannot ensure a placement gradient of 1:1.2.

[0041] Next, for ash mortar made by mixing fly ash (FA) and clinker ash (CA) in a mixing ratio of 9:1, the relationship between the flow value obtained from the mix test and the casting gradient obtained from the underwater casting experiment is shown in Figure 5. From Figure 5, it can be seen that if you want a casting gradient of 1:1.2, you should set the flow value of the ash mortar to 88 mm, and if you want a casting gradient of 1:4.4, you should set the flow value to 180 mm.

[0042] As shown in Figure 5, when the flow value of the ash mortar is 88 mm, it is possible to ensure the fluidity required for pumping and to achieve a pouring gradient of 1:1.2.

[0043] Furthermore, the relationship between the flow value obtained from a mix test and the water-powder ratio for ash mortar made with a mix ratio of 9:1 fly ash (FA) and clinker ash (CA) is shown in Figure 6. Figure 6 shows that if you want the flow value of the ash mortar to be 88 mm, you should adjust the water-powder ratio to 0.364, and if you want the flow value to be 180 mm, you should adjust the water-powder ratio to 0.439.

[0044] Table 1 below shows examples of mixtures for ash mortar made by mixing fly ash (FA) and clinker ash (CA) in a ratio of 9:1, which result in water-to-powder ratios of 0.364 and 0.439.

[0045] [Table 1]

[0046] Next, Figure 7 shows the relationship between the flow value obtained from a mix test and the casting gradient obtained from an underwater casting experiment for ash mortar made with a mix ratio of 8:2 fly ash (FA) and clinker ash (CA). Figure 7 shows that if a casting gradient of 1:1.2 is desired, the flow value of the ash mortar should be set to 92 mm, and if a casting gradient of 1:3.8 is desired, the flow value should be set to 163 mm. It can be seen that a flow value of 92 mm for the ash mortar made with the above mix ensures the fluidity required for pump casting and also enables a casting gradient of 1:1.2 to be achieved.

[0047] Furthermore, the relationship between the flow value obtained from a blending test and the water-powder ratio for ash mortar made with a blending ratio of 8:2 fly ash (FA) and clinker ash (CA) is shown in Figure 8. From Figure 8, it can be seen that if you want the flow value of the ash mortar to be 92 mm, you should adjust the water-powder ratio to 0.350, and if you want the flow value to be 163 mm, you should adjust the water-powder ratio to 0.419.

[0048] Table 2 below shows examples of mixtures for ash mortar made by mixing fly ash (FA) and clinker ash (CA) in a ratio of 8:2, which result in water-to-powder ratios of 0.350 and 0.419.

[0049] [Table 2]

[0050] From the results of the above experimental examples, the water-powder ratio of the ash mortar used in the mix tests and underwater casting experiments was in the range of 0.350 to 0.439. When the mix ratio of fly ash (FA) to clinker ash (CA) was 9:1, the flow value ranged from 88mm to 180mm when the water-powder ratio was in the range of 0.364 to 0.439. When this mix ratio was 9:1, the underwater casting slope when the flow value ranged from 88mm to 180mm was 1:1.2 to 4.4. When the mix ratio was 8:2, the water-powder ratio ranged from 0.350 to 0.419, the flow value ranged from 92mm to 163mm. When this mix ratio was 8:2, the underwater casting slope when the flow value ranged from 92mm to 163mm was 1:1.2 to 3.8.

[0051] From the above, for ash mortar with a clinker ash to fly ash ratio of 10% to 20%, adjusting the water-powder ratio allows the pouring gradient to be set to the target value (design value) and ensures the fluidity required for pump pouring. When the fly ash to clinker ash ratio is 9:1, a water-powder ratio of 0.364 to 0.439 for the ash mortar can be poured to a slope gradient of 1:1.2 to 4.4. Similarly, when the mixture ratio is 8:2, a water-powder ratio of 0.350 to 0.419 for the ash mortar can be poured to a slope gradient of 1:1.2 to 3.8.

[0052] In the above experimental example, the amount of solidification material mixed was 50 kg, but similar results were obtained in the flow test using a specimen with a mixed amount of 200 kg.

[0053] Although the embodiments for carrying out the present invention have been described above, the present invention is not limited to these, and various modifications are possible within the scope of the technical concept of the present invention. For example, the underwater structure shown in Figures 1 and 2 can be a revetment structure or a quay wall structure, but is not limited to this and can also be a bank structure. Furthermore, a structure using steel plate cells may be used instead of the caissons shown in Figures 1 and 2.

[0054] Furthermore, fly ash is mixed with clinker ash at a mixing ratio of more than 50%, and in this case, by conducting mixing tests with different mixing ratios of fly ash and clinker ash, it is possible to understand the degree to which the mixing ratio of clinker ash to fly ash affects the flow value. [Industrial Applicability]

[0055] According to the present invention, the predetermined slope of the slope portion of an underwater structure can be ensured without the use of additives, thereby reducing costs, eliminating the need for complicated procedures such as obtaining permission to use additives, and ensuring the fluidity required for pumping during construction, thereby achieving good workability. [Explanation of symbols]

[0056] 1 caisson 2. Mound 3 Backfill section 3a Slope section 5 Covering part 5a Slope section 10A,10B Underwater structure G underwater

Claims

1. A method for constructing an underwater structure having a sloped section using ash mortar obtained by mixing coal ash consisting of fly ash as a main component and clinker ash as a secondary component, a solidifying agent, and water, wherein the fly ash and the clinker ash are mixed in a mixing ratio of 9:1 to 8:2, When constructing the slope slope portion using ash mortar prepared by mixing the solidification material, coal ash, and water so that the water-to-powder ratio obtained by dividing the weight of the water by the total weight of the solidification material and the coal ash is within the range of 0.350 to 0.439, the water-to-powder ratio is adjusted within the range of 1:1.2 to 1:4.4 so that the slope slope of the slope slope portion reaches a target value within the range.

2. 2. The method for constructing an underwater structure according to claim 1, wherein the flow value of the ash mortar after mixing is at least 88 mm when the mixing ratio is 9:1, and at least 92 mm when the mixing ratio is 8:

2.

3. 3. The method for constructing an underwater structure according to claim 1, wherein the solidifying material is one, two, or all of blast furnace slag cement, ordinary Portland cement, and fly ash cement.

4. The amount of the solidifying material mixed is 50 kg / m ３ ~200kg / m ３ The method for constructing an underwater structure according to any one of claims 1 to 3, wherein the range is

5. 5. The method for constructing an underwater structure according to claim 1, wherein the ash mortar is pumped into water to construct the slope portion.

6. 6. A method for constructing an underwater structure according to claim 1, wherein the sloped portion is a backfill portion of the underwater structure or a covering portion of the backfill portion.

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