KR20220029086A - Backfiller Composition With High Flowability - Google Patents

Abstract

The present invention provides a high-flowing filler composition suitable for backfilling of excavations after a structure is completed in constructing the foundation of buildings, bridges, culverts, drainage pipes, retaining walls, and other structures. A binder composition for a high-flowing filler according to the present invention is usually composed of: 5 to 20 wt% of Portland cement; 75 to 90 wt% of supercritical fluidized bed boiler fly ash; 0.5 to 3 wt% of calcium aluminate; 3 to 8 wt% of petro-coke ash; and 0.1 to 1.0 wt% of a high-performance water reducing agent.

Description

{Backfiller Composition With High Flowability}

The present invention relates to a filling material suitable for backfilling work after excavating the structure after excavation in constructing the foundation of a building, bridge, culvert, drain pipe, retaining wall and other structures, and more particularly, backfilling It relates to a new backfill composition that secures economical efficiency and workability while expressing required performance such as high fluidity, strength development, and compaction-free properties optimized as a material, and a manufacturing method for preferably using it as a backfilling material.

In general, for backfilling of buildings, bridge abutments, culverts, drainage pipes, retaining walls, and other structures, it should be constructed after sufficiently compacting using materials such as high-quality soil or sand. However, in the case of the majority of backfill construction in downtown areas, it is difficult to transport the backfill material and enter the compaction equipment because the space is narrow and there are many obstacles. Also, even in a situation where equipment enters, it is difficult to make a sufficient commitment to prevent delays in follow-up work.

In order to solve this problem, an on-site mixed soil having fluidity was developed by mixing the soil and solidified material generated in the field at the site. However, in the case of flowable on-site mixed soil, it is not suitable for narrow urban areas because it requires a large area of work site for the installation of plant equipment that sorts, processes, and mixes excavated soil and for on-site soil storage.

Recently, low-strength, high-fluidity fillers that have sufficient fluidity to enable backfilling of structures without compaction by using industrial by-products such as fly ash and low-cost materials that are usually easily obtained, such as Portland cement, as a filling material and set after pouring. came to develop

Registered Patent 10-2037203 Registered Patent 10-1835795 Registered Patent 10-1146339 Patent Publication 10-2020-0034431

The present invention is proposed in order to solve the various problems of the prior art as described above, and it is possible to improve economic efficiency by using industrial by-products such as supercritical fluidized bed fly ash and petrocoke ash and general-purpose materials such as ordinary Portland cement as a binder for filling materials. It has sufficient fluidity to enable backfilling of the structure without compaction work, has coarse rigidity so that it can be hardened within an appropriate time after filling so as not to delay the subsequent process, and maintains low strength for easy excavation during future maintenance It is intended to provide a high fluidity filler for backfilling, characterized in that

Furthermore, the present invention is to provide a method for manufacturing a filling material composition that can be preferably used for backfill construction in a narrow site site.

The present invention in order to solve the above technical problem, usually Portland cement 5 to 20% by weight; 75-90 wt% of supercritical fluidized bed boiler fly ash; 0.5 to 3% by weight of calcium aluminate; 3 to 8% by weight of petrocoke ash; It provides a high-flowing filler composition for backfilling structures using industrial by-products, characterized in that it contains 0.1 to 1.0% by weight of a high-performance water reducing agent.

According to the present invention, the following effects can be expected.

First, it is possible to provide an economical new binder composition for fillers optimized for the performance required as fillers for backfilling structures. In other words, it is possible to secure economic feasibility by actively utilizing industrial by-products, and due to high fluidity, it is possible to perform mass pouring construction using pressure-feeding equipment at the site, and it is possible to proceed with subsequent processes with rapid strength development.

Second, the binder composition for backfill according to the present invention is pre-mixed in a factory and supplied to a silo in the field, and since it is possible to manufacture a filling material by mixing only water in the field, it is possible to work sufficiently even in a narrow working space in the downtown area. It can be used to your advantage in construction.

The present invention relates to a filler composition for use in backfilling structures, and by actively utilizing a small amount of ordinary Portland cement and a large amount of industrial by-products to form a binder, promote economic feasibility, and use calcium aluminate and a high-performance water reducing agent to provide crude rigidity And it is characterized in that it provides fluidity. As industrial by-products, supercritical fluidized bed boiler fly ash and petrocoke ash are used.

Specifically, the binder composition for backfill material according to the present invention is usually Portland cement 3 to 15% by weight; 75-90 wt% of supercritical fluidized bed boiler fly ash; 0.5 to 3% by weight of calcium aluminate; 3 to 8% by weight of petrocoke ash; It is composed of 0.1 to 1.0% by weight of a high-performance water reducing agent.

Supercritical fluidized bed boiler fly ash is a major raw material constituting the filler material for backfilling structures, and it is fly ash discharged from a supercritical fluidized bed boiler operating in a supercritical state. Here, the supercritical fluidized bed boiler is operated under supercritical conditions (218.13 atm steam pressure, 374.2 degrees steam temperature) in which water is converted into steam, thereby increasing the efficiency by 5-10% compared to the traditional natural circulation boiler, thereby increasing NOX, SOX , Mercury, fine dust, as well as greenhouse gases can be emitted relatively little, and the existing coal fuel as well as hard-to-burn fuel, biomass, etc. can be burned.

Common fly ash is ash emitted through the process of injecting undifferentiated fuel (coal) and air in a coal-fired power plant and burning it (1200~1500 degrees). Supercritical fluidized bed boiler fly ash is ash that is discharged through the process of burning fuel (coal) under supercritical conditions (218.13 atm steam pressure, 374.2 degrees steam temperature) by injecting oxygen instead of air in the supercritical fluidized bed boiler. These fly ash have in common in that they are ash emitted from coal-fired power plants, but the specific treatment methods of power plants are different, so the chemical composition and physical properties of ash are different as shown in Table 1 below. The fluidized bed boiler fly ash contains at least 20 wt% CaO, at least 15 wt% Fe ₂ O ₃ , and at least 8 wt% SO ₃ components. At this time, CaO and SiO ₂ react with water to form CSH hydrate. In addition, CaO and Fe ₂ O ₃ combine to form calcium ferrite (2CaO ^. Fe ₂ O ₃ ) mineral with hydration reactivity, contributing to strength development.

Therefore, the use of supercritical fluidized bed fly ash has the advantage of being able to express higher strength even if the same amount is used than when using ordinary fly ash or ordinary circulating fluidized bed boiler fly ash.

Characteristics of each type of fly ash division Chemical composition (wt%) physical properties CaO SiO ₂ Al ₂ O ₃ MgO Fe ₂ O ₃ SO ₃ K ₂ O Na ₂ O fineness
(cm ² /g) density
(g/cm ³ ) General
fly ash 1.0 61.0 19.4 - 6.3 - 1.0 - 2,970 2.13 circulating fluidized bed
fly ash 3.8 58.4 21.3 1.26 5.13 - 1.58 1.63 3,200 2.91 Supercritical Fluidized Bed Fly Ash 24.5 27.9 13.3 6.14 15.45 8.87 1.35 1.01 7,500 2.89

In the present invention, the supercritical fluidized bed boiler fly ash contains 10 to 20 wt% of Fe ₂ O ₃ and 5 to 20 wt% of SO ₃ It is preferable to use a powder pulverized to 6,000 to 9,000 cm ² /g. Such supercritical fluidized bed boiler fly ash can rapidly generate hydrates such as Ca(OH) ₂ to increase initial strength, improve material separation resistance of filler materials due to high fineness, and accelerate hardening reaction. It is preferable to use this supercritical fluidized bed fly ash at 75 to 90% by weight of the binder, but if it is less than 75% by weight, the use of portland cement is usually high, which leads to poor economic feasibility and high late strength expression, so there may be difficulties during re-excavation construction. If it exceeds 90% by weight, there is a concern that the workability and strength performance decrease.

In the filler composition, Portland cement is usually used as an auxiliary material to develop strength to enable subsequent work after pouring, and 5 to 20% by weight of the filler composition is suggested. If it is less than 5% by weight, initially strength is insignificant, and if it exceeds 20% by weight, economical efficiency is deteriorated.

Calcium aluminate is a quick-setting component that speeds up the setting of cement in the initial stage, and is a material for improving initial strength. In general, if CaO is C and Al ₂ O ₃ is A, C ₃ A, C ₁₂ A ₇ , CA, CA ₂ , and the like are those obtained by pulverizing heat-treated products of calcium aluminate, and among these, amorphous calcium aluminate obtained by quenching heat-treated products corresponding to the C ₁₂ A ₇ composition is preferable in terms of reaction activity. Do. Calcium aluminate has a specific surface area of 3,000 to 7,000 cm ² /g, and more preferably 5,000 cm ² /g or more, in terms of coagulation characteristics or strength development. Calcium aluminate suggests 0.5 to 3% by weight of the filler composition. If it is less than 0.5% by weight, the role of promoting coagulation is insignificant, and if it is more than 3% by weight, the initial workability is deteriorated due to the generation of a large amount of ettringite, so that the workability is deteriorated.

Petrocoke ash is ash produced when petrocoke is used as fuel and contains a large amount of CaO and CaSO4 and has a strong alkalinity of pH 12 or higher when reacted with water. Petrocoke ash reacts with calcium aluminate to form etringite, which promotes setting and improves initial strength. It is preferable to use 3 to 8% by weight of the petrocoke ash of the mixed material. The chemical reaction at this time is as follows.

C ₃ A + 3CaSO ₄ + 32H ₂ O -> C ₃ A ₃ CaSO ₄ ^. 32H ₂ O

Since the production of etringite generally promotes the production of C-S-H gel and immobilizes a large amount of free water as crystal water, it can substantially reduce the water/filler ratio and express crude rigidity.

The filler composition according to the present invention includes a high-performance water reducing agent, wherein the high-performance water reducing agent may be one or more types from the group consisting of a naphthalenesulfonic acid compound, a melamine-based compound, and a polycarboxylic acid-based compound, and may be in the form of a powder. The superplasticizer may serve to improve the initial fluidity and reduce the amount of water used by dispersing the supercritical fluidized bed boiler fly ash and ordinary Portland cement particles at the initial stage of the reaction of the filler composition. When the high-performance water reducing agent is less than 0.3% by weight, it may not exhibit the effect of improving the fluidity, and when it exceeds 1% by weight, there is a risk of material separation due to high dispersibility.

The above filler composition can be used by simply mixing with water using available equipment depending on the site conditions, and in this case, 80 to 110% by weight of the compounding water is suitable compared to the filler composition. If the blending number is less than 80% by weight, fluidity is lowered and workability is deteriorated, and when it exceeds 110% by weight, strength development is delayed. As a filler suitable for backfill construction, the water-mixed filler material exhibits performances such as high fluidity, strength expression, and compaction-free properties, and furthermore, it is advantageous in economic feasibility and workability.

Hereinafter, the present invention will be described in detail based on test examples. However, the following test examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

[Test Example] Characteristic test of filler material

1. Filling material composition

A filling material was prepared as shown in [Table 2] below.

Filler composition (wt%) General
fly ash fluidized bed
fly ash supercritical fluidized bed
fly ash Ordinary Portland Cement amorphous calcium
aluminate Petrocoke Ash high performance
water reducing agent Comparative Example 1 90.0 - - 10.0 - - - Comparative Example 2 - 90.0 - 10.0 - - - Comparative Example 3 90.0 - - 9.5 - - 0.5 Comparative Example 4 - 90.0 - 9.5 - - 0.5 Comparative Example 5 - - 90.0 10.0 - - - Comparative Example 6 - - 90.0 9.5 - - 0.5 Comparative Example 7 - - 80.0 10.0 - 9.5 0.5 Example 1 - - 80.0 10.0 One 8.5 0.5 Example 2 - - 80.0 10.0 3 6.5 0.5 *General fly ash: Table 1
*Fluid bed fly ash: Table 1
*Supercritical fluidized bed fly ash: Table 1
*Normal Portland Cement: Class 1 OPC
*Amorphous calcium aluminate: C ₁₂ A ₇ , specific gravity 2.68, fineness of 6,000cm ² /g
(The mineral containing CaO and the mineral containing alumina (Al2O3) are put in quicklime (CaO) and an electric furnace, melted completely at 1300-1500℃, then quenched and crushed to make powder)
*Petrocoke ash: specific gravity 2.69, fineness 3.920cm ² /g
*High performance water reducing agent: polycarboxylic acid (light brown liquid, specific gravity 1.2, pH 4.0~7.5)0

2. Characteristic evaluation

After mixing the mixing water with the filler composition having the same composition as in [Table 2] above, flow, bleeding rate, and compressive strength were measured. Flow (fluidity) was measured according to ACI-229R-99, bleeding rate was KS F 2433, and compressive strength was measured according to KS L ISO 679. The measurement results are shown in [Table 3] below.

Filler properties Mixing water (%) Flow value (mm) Bleeding rate (%) Compressive strength (MPa) 0 minutes 60 minutes 1 day 7 days 28 days Comparative Example 1 85% 280 280 6.4 - 0.9 1.5 Comparative Example 2 95% 280 250 2.5 0.03 2.7 4.4 Comparative Example 3 75% 310 310 7.3 - 1.4 2.3 Comparative Example 4 82% 300 260 1.8 0.08 3.0 4.9 Comparative Example 5 110% 285 265 0.7 0.2 4.2 6.0 Comparative Example 6 90% 310 285 0.5 0.3 4.9 7.4 Comparative Example 7 90% 300 275 0.4 0.4 5.2 8.1 Example 1 90% 290 270 0.2 0.9 5.4 8.7 Example 2 90% 285 260 0.1 1.4 5.9 9.1

As shown in [Table 3] above, compared to Comparative Example 1 using ordinary fly ash and Comparative Example 2 using fluidized bed boiler fly ash, Comparative Example 5 using supercritical fluidized bed boiler fly ash, despite the high mixing amount It can be seen that the initial compressive strength in 1 day is excellent, and the bleeding rate is also remarkably low, making it possible to maintain a stable volume after pouring. In particular, Comparative Example 1 using ordinary fly ash had a slight initial hardening reaction, almost no strength development in 1 day, and a bleeding rate was also quite high. In Comparative Examples 3 and 4, a portion of the ordinary Portland cement was reduced in Comparative Examples 1 and 2 and replaced with a high-performance water reducing agent, and it was confirmed that fluidity and compressive strength were improved while reducing the mixing amount compared to Comparative Example 1.2. Comparative Example 6 is an example in which a portion of cement was substituted with a high-performance water reducing agent in Comparative Example 5, and it was confirmed that fluidity, compressive strength, and bleeding rate were improved while reducing the mixing amount compared to Comparative Example 5. Comparative Example 7 was an example in which the supercritical fluidized bed fly ash was reduced in Comparative Example 6 and the petrocoke ash was substituted, and it was confirmed that the compressive strength was improved compared to Comparative Example 6.

Examples 1 and 2 are examples proposed to provide a filler composition that exhibits more improved initial strength than Comparative Examples 5 and 6, and a portion of the supercritical fluidized bed boiler fly ash is replaced with amorphous calcium aluminate and petrocoke ash This is an example used. As can be seen, as the amount of amorphous calcium aluminate increased, the curing reaction was accelerated, and it was confirmed that the compressive strength in 1 day was very high, the bleeding rate was reduced, and fluidity was also secured. Therefore, when the fillers of Examples 1 and 2 are used as fillers for backfilling structures, long-distance pressure feeding is possible with high fluidity, and thus the workability is excellent, the bleeding rate is very low, and it is possible to maintain a stable volume after curing. In addition, since the daily compressive strength is high, there is no difficulty at all in carrying out the subsequent process required at the site, and the long-term strength is also excellent, so high construction quality can be secured. According to these results, it is expected that the high-flowing filler composition according to the present invention can be advantageously used for backfilling of structures.

Claims (4)

Usually Portland cement 5-20% by weight; 75-90 wt% of supercritical fluidized bed boiler fly ash; 0.5 to 3% by weight of calcium aluminate; 3 to 8% by weight of petrocoke ash; High-flowing filler composition for backfilling structures using industrial by-products, characterized in that it contains 0.1 to 1.0% by weight of a high-performance water reducing agent. According to claim 1,
The supercritical fluidized bed boiler fly ash is a fly ash that is by-product from a fluidized bed circulating boiler operated in supercritical conditions (218.13 atm steam pressure, 374.2 degrees steam temperature) in which water is converted to steam to increase the efficiency of power generation, CaO 15 High flow for backfilling structures using industrial by-products, characterized in that it contains ~25% by weight, Fe ₂ O ₃ 10 ~ 20% by weight, SO ₃ 5 ~ 20% by weight, and is pulverized to 6,000 ~ 9,000 cm ² /g filler composition. According to claim 1,
The calcium aluminate, C ₃ A, C ₁₂ A ₇ , CA, CA ₂ characterized in that by cooling one or more heat-treated products selected from compounds represented by, and pulverizing to a powder of 3,000 ~ 7,000 cm ² /g A high-flowing filler composition for backfilling structures using industrial by-products. According to claim 1,
The high-performance water reducing agent is a high-flowing filler composition for backfilling structures using industrial by-products, characterized in that at least one selected from the group consisting of a naphthalenesulfonic acid-based compound, a melamine-based compound, and a polycarboxylic acid-based compound.