TWI846008B - Controlled low strength backfill material - Google Patents

Abstract

A controlled low-strength backfill material comprises crushed material and raw material components. The crushed material is formed by hydrating a reaction component comprising a fly ash component and water until the exothermic phenomenon ends, and then crushing the fly ash component, and the fly ash component comprises fly ash containing more than 50 wt% of calcium oxide. The raw material component comprises cement and water. By hydrating the fly ash containing more than 50wt% of calcium oxide with water, the fly ash containing more than 50wt% of calcium oxide can be applied to the controlled low-strength backfill material, which can not only avoid the expansion phenomenon, but also make the fly ash containing more than 50wt% of calcium oxide have recycling value, thereby reducing the secondary pollution to the environment. At the same time, it also gives the controlled low-strength backfill material the advantage of a short initial setting time and shortening the construction project progress.

Description

Controlled low strength backfill material

The present invention relates to a concrete, in particular to a controlled low-strength backfill material.

General industrial waste, such as ash residue (such as fly ash or bottom ash) after incineration or toxic waste, is often disposed of by landfill because it has no recycling value. However, this landfill method has problems such as high land cost, difficulty in finding sites, waste of land resources, and secondary pollution to the environment. Therefore, how to effectively reuse industrial waste, especially fly ash, has become a widely studied issue.

Due to its catalytic activity, fly ash is widely used in concrete engineering and is used to replace part of cement. However, since some fuels will produce a large amount of sulfur oxides (such as SO ₂ ) that are harmful to the human body and the environment during the combustion process, in order to avoid the emission of a large amount of sulfur oxides, lime that can absorb sulfur oxides is often added to the fuel. However, this practice causes the fly ash produced to contain more than 50wt% of calcium oxide. The applicant of the present invention has found through research that such fly ash can be directly used in controlled low strength materials (CLSM), which will cause the volume expansion of the controlled low strength materials and cause the potential risk of instability.

Therefore, how to effectively apply fly ash with more than 50wt% calcium oxide to controlled low-strength backfill materials to reduce the impact on the environment is a difficulty that is expected to be overcome.

Therefore, the object of the present invention is to provide a controlled low-strength backfill material.

Therefore, the controlled low-strength backfill material of the present invention comprises crushed material and cement components. The crushed material is formed by hydrating a reaction component comprising a fly ash component and water, and then crushing the fly ash component, and the fly ash component comprises fly ash having more than 50wt% of calcium oxide. The raw material components comprise cement and water.

The effect of the present invention is that by hydrating the fly ash containing more than 50wt% of calcium oxide with water, the fly ash containing more than 50wt% of calcium oxide can be applied to the controlled low-strength backfill material, which can not only avoid the expansion phenomenon, but also make the fly ash containing more than 50wt% of calcium oxide have recycling value, thereby reducing the secondary pollution to the environment, and at the same time, the controlled low-strength backfill material has the advantage of a short initial setting time and shortening the construction project progress.

The controlled low-strength backfill material of the present invention comprises crushed material and raw material components. The crushed material is formed by hydrating a reaction component comprising a fly ash component and water until the exothermic phenomenon ends, and then crushing the fly ash component, and the fly ash component comprises fly ash having more than 50wt% of calcium oxide. The raw material component comprises cement and water.

The present invention is described in detail below.

The fly ash may be, for example but not limited to, fly ash from the Guantian Plant of Taiwan Cogeneration Corporation.

In some embodiments of the present invention, the weight ratio of the fly ash component to water in the reaction composition ranges from 0.9 to 1.1:1.

In some embodiments of the present invention, the temperature of the hydration reaction is in the range of 50°C to 70°C, and the time is in the range of 30 minutes to 40 minutes. In the present invention, by subjecting the fly ash component to a hydration reaction, the calcium oxide in the fly ash is reacted into calcium hydroxide, so that when mixed with the raw material component, it is not easy to have a large volume expansion phenomenon, thereby giving the fly ash with more than 50wt% of calcium oxide the value of being able to be reused, so that the harm of secondary pollution caused to the environment can be reduced.

The size of the crushed material is not particularly limited, as long as it can be uniformly mixed with the raw material component. In some embodiments of the present invention, the size of the crushed material ranges from 15 mm to 25 mm. In some embodiments of the present invention, based on the total amount of the controlled low-strength backfill material as 100 wt%, the amount of the crushed material ranges from 75 wt% to 88 wt%.

The cement is, for example but not limited to, Portland cement produced by Taiwan Cement Co., Ltd. The Portland cement is, for example but not limited to, Portland cement Type I.

The amount of water is adjusted according to the desired properties of the controlled low-strength backfill material and the on-site construction operating conditions.

In some embodiments of the present invention, the raw material component further includes aggregates. The aggregates are, for example but not limited to, sand or stone. The amount of the aggregates is adjusted according to the required properties of the controlled low-strength backfill material and the on-site construction operation conditions.

In some embodiments of the present invention, the raw material component further includes a cement-based treatment agent, such as a soil improver, such as but not limited to a cement-based soil improver with a brand of China United Resources Company and a model of HSC301.

The present invention will be further described with respect to the following embodiments, but it should be understood that these embodiments are only for illustrative purposes and should not be interpreted as limitations on the implementation of the present invention.

Embodiment 1

5712 grams of fly ash (source: Guantian Plant of Taiwan Cogeneration Co., Ltd.; containing 50 wt% of calcium oxide) was mixed with 5712 grams of water and subjected to a hydration reaction at 50°C for 40 minutes to obtain a mixture (containing 53 wt% of calcium hydroxide). Then, the mixture was crushed to obtain 6148 grams of crushed material with a particle size of 19 mm. The crushed material was mixed with raw material components to obtain a controlled low-strength backfill material, wherein the raw material components included 212 grams of Portland cement type I (source: Global Cement), 530 grams of cement-based soil conditioner (brand: China United Resources Corporation; model: HSC301), and 1133 grams of water.

Embodiment 2

4368 grams of fly ash (source: Guantian Plant of Taiwan Cogeneration Co., Ltd.; composition: 50 wt% calcium oxide) was mixed with 1092 grams of calcium oxide to obtain a fly ash component. 5460 grams of the fly ash component was mixed with 5460 grams of water and subjected to a hydration reaction at 57°C for 40 minutes to obtain a mixture (containing 64 wt% calcium hydroxide). Then, the mixture was crushed to obtain 6150 grams of crushed material with a particle size of 19 mm. The crushed material is mixed with a raw material component to obtain a controlled low-strength backfill material, wherein the raw material component includes 212 grams of Portland cement type I (source: Universal Cement), 530 grams of cement-based soil conditioner (brand: China United Resources Company; model: HSC301), and 1133 grams of water.

Examples 3 to 8

The preparation methods of Examples 3 to 8 are substantially the same as those of Example 2, with the main differences being that the amounts of fly ash, water and crushed materials, and the conditions of the hydration reaction are changed.

Comparison Example 1

6148 grams of fly ash (source: Guantian Plant of Taiwan Cogeneration Corporation; composition: 50 wt% calcium oxide) was mixed with raw material components to obtain concrete, wherein the raw material components included 212 grams of Portland cement Type I (source: Universal Cement), 530 grams of cement-based soil conditioner (brand: China United Resources Corporation; model: HSC301), and 1133 grams of water.

Comparison Example 2

4921 grams of fly ash (source: Guantian Plant of Taiwan Cogeneration Co., Ltd.; composition: 50 wt% calcium oxide) was mixed with 1230 grams of calcium oxide to obtain a fly ash component. The fly ash component was mixed with a raw material component to obtain concrete, wherein the raw material component included 212 grams of Portland cement type I (source: Universal Cement), 530 grams of cement-based soil conditioner (brand: China United Resources Corporation; model: HSC301), and 1133 grams of water.

Comparison Example 3

The preparation method of Comparative Example 3 is substantially the same as that of Comparative Example 2, with the main difference being that the amounts of fly ash, calcium oxide and aggregate are changed.

Evaluation items

In order to clearly describe the measurement process, the controlled low-strength backfill material of Example 1 is used for illustration below, and the controlled low-strength backfill materials of the other embodiments and the concrete of the comparative example are measured according to the process.

Drop strength test: Referring to the ASTM D6024 method for determining the load-bearing time of controlled low-strength backfill materials by using a drop ball, the two end brackets of the test hemisphere are fixed on a flat plate, and then the heavy ball is lifted to a height of about 11.4 cm. Then, the heavy ball is allowed to fall freely and hit the test plate, and this is repeated five times. Then, the diameter of the dent produced on the test plate after the impact is measured using a vernier ruler. In particular, referring to the sample preparation section disclosed in ASTM D6024, the controlled low-strength backfill material of Example 1 is made into a test plate of 15 cm x 15 cm x 53 cm.

Compressive strength measurement: Referring to the laboratory concrete specimen preparation and curing method of CNS 1230 of the National Standard of the Republic of China, the controlled low-strength backfill material of Example 1 was subjected to specimen preparation and curing to obtain a specimen. Then, referring to the preparation and testing method of controlled low-strength material cylindrical specimens of ASTM D4832 of the American Society for Materials and Testing, and using a compression testing machine (brand: ELE; model: AUTO2000), the compressive strength of the specimen was measured.

Slump flow measurement: The measurement is carried out in accordance with the slump flow test method for high-flow concrete in the Republic of China National Standard CNS 14842. Wet the slump cone with clean water and place it on the steel plate. Then, step on the slump cone with both feet to fix the slump cone on the steel plate. The controlled low-strength backfill material of Example 1 is filled into the slump cone in three layers and compacted. Then, the controlled low-strength backfill material of Example 1 protruding from the top of the slump cone is scraped off with a scraper. Then, the slump cone is lifted vertically within 5 seconds, and the controlled low-strength backfill material of Example 1 begins to slump. After the slump action is completed, the vertical distance from the controlled low-strength backfill material of Example 1 to the top of the triangular cone of the slump cone is measured, and the height (i.e., the slump) is recorded. In addition, the diameter of the approximate circle of the controlled low-strength backfill material of Example 1 after it spreads on the ground and diffuses to all sides until it stops is measured, and the diameter (i.e., the slump flow) is recorded.

Table 1 Comparison Example Embodiment 1 2 3 1 2 3 4 Fly ash components Fly ash (g, 50wt% calcium oxide) 6148 4921 3690 5712 4368 3180 2076 Calcium oxide (g) 0 1230 2460 0 1092 2120 3114 Calcium oxide content (wt%) 50 60 80 50 60 70 80 Total amount (g) 6148 6151 6150 5712 5460 5300 5190 Amount of water (g) 0 0 0 5712 5460 5300 5190 Hydration reaction Temperature(℃) -- -- -- 50 57 65 70 Time(minutes) -- -- -- 40 40 30 30 Calcium hydroxide in the mixture (wt%) 0 0 0 53 64 75 85 Crushed matter Yield (g) 0 0 0 6148 6150 6148 6140 Particle size (mm) -- -- -- 19 19 19 19 Raw material components Portland Cement Type I (g) 212 212 212 212 212 212 212 Cement-based soil conditioner (g) 530 530 530 530 530 530 530 Water (g) 1133 1133 1133 1133 1133 1133 1133 Drop strength test Dent diameter (mm) Not measured 72 72 71 71 Time required for dent diameter less than 76mm (hr) Not measured 20 20 19 19 28-day compressive strength (kgf/cm ² ) Not measured 60 65 63 67 Slump(cm) Not measured 51 50 51 50 Slump flow (cm) Not measured 55 54 55 49

Table 2 Embodiment 5 6 7 8 Fly ash components Fly ash (g, 50wt% calcium oxide) 6854 10282 12338 2491 Calcium oxide (g) 0 0 0 3737 Calcium oxide content (wt%) 50 50 50 80 Total amount (g) 6854 10282 12338 6228 Amount of water (g) 6854 10282 12338 6228 Hydration reaction Temperature(℃) 50 51 50 70 Time(minutes) 40 40 40 30 Calcium hydroxide in the mixture (wt%) 53 53 53 84 Crushed matter Yield (g) 7380 11070 13284 8122 Particle size (mm) 19 19 19 19 Raw material components Portland Cement Type I 212 212 212 212 Cement-based soil conditioner (g) 530 530 530 530 Water (g) 1133 1133 1133 1133 Drop strength test Dent diameter (mm) 72 72 72 71 Time required for dent diameter less than 76mm (hr) 20 20 20 twenty one 28-day compressive strength (kgf/cm ² ) 62 63 65 63 Slump(cm) 49 55 51 50 Slump flow (cm) 50 50 49 47

It can be seen from the sinking strength test in Table 1 and Table 2 that in Examples 1 to 8, the fly ash having more than 50 wt% of calcium oxide is hydrated and then applied to the controlled low-strength backfill material, so that the time required for the embossing diameter to be less than 76 mm is 19 hours to 21 hours. This indicates that the design of hydrating the fly ash having more than 50 wt% of calcium oxide and then using it can indeed reduce the initial setting time of the controlled low-strength backfill material, thereby helping to shorten the construction project progress.

Furthermore, referring to Figures 1 to 3, in Comparative Examples 1 to 3, the fly ash component containing more than 50 wt% of calcium oxide is directly mixed with the raw material components including water and cement to produce an expansion reaction, resulting in a large expansion of the volume of the formed concrete. In such a state, it cannot be used as a controlled low-strength backfill material, so that subsequent measurements are not performed. Referring to Figures 4 to 11, the controlled low-strength backfill material of Examples 1 to 8 of the present invention does not have an expansion phenomenon. It can be seen that the crushed product formed by the hydration reaction of the fly ash containing more than 50 wt% of calcium oxide with water can indeed give the controlled low-strength backfill material volume stability.

In summary, by hydrating the fly ash containing more than 50wt% of calcium oxide with water, the fly ash containing more than 50wt% of calcium oxide can be applied to the controlled low-strength backfill material, which can not only avoid the expansion phenomenon, but also make the fly ash containing more than 50wt% of calcium oxide have recycling value, thereby reducing the secondary pollution to the environment. At the same time, the controlled low-strength backfill material is endowed with the advantage of a short initial setting time and shortened construction progress, so the purpose of the present invention can be achieved.

However, the above is only an embodiment of the present invention and should not be used to limit the scope of implementation of the present invention. All simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the patent specification are still within the scope of the present patent.

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein: FIG. 1 is an appearance photograph, illustrating that in Comparative Example 1, when fly ash with 50 wt% of calcium oxide is directly mixed with the raw material component, the obtained concrete expands and is exposed outside the container; FIG. 2 is an appearance photograph, illustrating that in Comparative Example 2, when fly ash component with 60 wt% of calcium oxide is mixed with the raw material component, the obtained concrete expands and is exposed outside the container and produces a large number of cracks; FIG. 3 is an appearance photograph, illustrating that in Comparative Example 3, when fly ash component with 80 wt% of calcium oxide is mixed with the raw material component, the obtained concrete expands significantly and is exposed outside the container; Figure 4 is an appearance photograph, which shows that in Example 1, when the crushed material is mixed with the raw material component, the controlled low-strength backfill material of the present invention will not expand and be exposed outside the container: and Figure 5 is an appearance photograph, which shows that in Example 2, when the crushed material is mixed with the raw material component, the controlled low-strength backfill material of the present invention will not expand and be exposed outside the container; Figure 6 is an appearance photograph, which shows that in Example 3, when the crushed material is mixed with the raw material component, the controlled low-strength backfill material of the present invention will not expand and be exposed outside the container; Figure 7 is an appearance photograph, which shows that in Example 4, when the crushed material is mixed with the raw material component, the controlled low-strength backfill material of the present invention will not expand and be exposed outside the container; FIG8 is an appearance photograph, which shows that in Example 5, when the crushed material is mixed with the raw material component, the controlled low-strength backfill material of the present invention will not expand and be exposed outside the container; FIG9 is an appearance photograph, which shows that in Example 6, when the crushed material is mixed with the raw material component, the controlled low-strength backfill material of the present invention will not expand and be exposed outside the container; FIG10 is an appearance photograph, which shows that in Example 7, when the crushed material is mixed with the raw material component, the controlled low-strength backfill material of the present invention will not expand and be exposed outside the container; FIG11 is an appearance photograph, which shows that in Example 8, when the crushed material is mixed with the raw material component, the controlled low-strength backfill material of the present invention will not expand and be exposed outside the container.

without.

Claims (2)

A controlled low-strength backfill material comprises: a crushed material, which is formed by a reaction composition consisting of a fly ash component and water undergoing a hydration reaction until the exothermic phenomenon ends, and then undergoing a crushing treatment, wherein the fly ash component comprises fly ash having more than 50 wt% of calcium oxide; and a raw material component, which comprises cement, water, and a cement-based soil conditioner; wherein the weight ratio of cement: cement-based soil conditioner: water in the raw material component: crushed material is 1:2.5:5.34:X, and X is 28.96, 29.0 ... 1, 34.81, 38.31, 52.22 or 62.66, and corresponding to X, the content of calcium oxide in the fly ash component is 80wt%, Y, 60wt%, 50wt%, 80wt%, 50wt% and 50wt% in sequence, and Y is 70wt% or 50wt%, and the weight ratio of the fly ash component to water in the reaction composition ranges from 0.9 to 1.1:1; based on the total amount of the controlled low-strength backfill material as 100wt%, the amount of the crushed material ranges from 75wt% to 88wt%. The controlled low-strength backfill material as described in claim 1, wherein the temperature range of the hydration reaction is 50°C to 70°C, and the time range is 30 minutes to 40 minutes.