JP2540422B2 - Rolling compact concrete paving material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for compacted concrete pavement which is inexpensive and excellent in long-term strength by using coal ash, which is a by-product generated from a fluidized bed boiler, as a substitute for cement.

[0002]

2. Description of the Related Art Compacted concrete pavement is excellent in durability without rutting due to flow unlike in asphalt pavement. Further, compared with the conventional cement concrete pavement, it is a construction method that has been drawing attention in recent years as a solution to the problems faced by conventional pavements, such as faster construction speed and faster traffic release. This compacted concrete paving material is usually composed of cement, water, coarse aggregate, and fine aggregate. As a material for the above-mentioned compacted concrete pavement, it has been proposed to use coal ash generated from a boiler of a thermal power plant as an admixture from the viewpoint of improving workability and economical efficiency by using a by-product. (See Proceedings of 19th Japan Road Conference 469, Utilization of fly ash in compacted concrete).

[0003]

However, this coal ash is generated from the boiler of a thermal power plant, and if the coal ash is replaced by 10 to 30% by weight of cement, the material age is 90%.
The long-term compressive strength of the day is 64, which does not replace coal ash.
Compared to 9 kg / cm ² , replacement rate of 10% is 621 kg / cm ² , replacement rate of 20% is 639 kg / cm ² , replacement rate of 30% is 631 kg / cm ^2.
Therefore, the long-term strength development cannot be expected by replacing coal ash with cement.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is a coal ash (pulverized coal) generated from a boiler of a thermal power plant that has been used as an admixture for a conventional compacted concrete pavement. As an alternative to ash), by replacing the coal ash generated from the fluidized bed boiler as a substitute for cement, the long-term compressive strength of 90 days is 1% at a replacement rate of 10% compared to the one not replacing the coal ash. .04
Fold, a long-term strength of 1.06 times can be obtained at a substitution rate of 20%. As a result, it is possible to supply a compacted concrete pavement material that is inexpensive and has excellent long-term strength development and improved durability, as in the past, and open the way for expanding the use of coal ash as a by-product. That is, the gist of the present invention is cement, water,
A compacted concrete pavement material comprising coarse aggregate and fine aggregate, wherein coal ash generated from a fluidized bed boiler is replaced by 10 to 20% by weight of the cement. It is in the materials for use.

The present invention will be described in detail below. Since the fluidized bed boiler uses limestone as a desulfurizing agent, the generated coal ash contains a large amount of lime and gypsum which are desulfurization products as shown in Table 1, as compared with pulverized coal ash. Therefore, this coal ash (F) produces ettringite by adding water (W), and for example, the coal ash generated from the fluidized bed boiler having the chemical components shown in A of Table 2 is as shown in FIG. It has the property of hardening to. The W / F of FIG.
Indicates the weight ratio of water to coal ash. In addition, the granular shape is indefinite, as spherical particles such as pulverized coal ash are not seen. This is considered to be because the combustion temperature of the fluidized bed boiler is kept low as a measure against Nox, and the softening temperature of ash has not been reached.

[Table 1]

Paying attention to the characteristics of the coal ash generated from these fluidized bed boilers, the coal ash of A in Table 2 in the composition shown in Table 3 was replaced with cement at a rate of 0, 10, 20, 30%, and the material was aged. The bending strength of 28 days was measured. The materials used were blast furnace cement type B as cement and natural crushed stone 20 as coarse aggregate.
05, sea sand as fine aggregate, and AB water reducing agent as admixture. As a result, the design standard bending strength of 28 days of age 50 kg / c
60 kg / cm ² at a replacement rate of 0% and 58 kg / c at 10% for m ^2.
m ^2, 20% by 56kg / cm ^2, 30% became a 54kg / cm ^2, both satisfied the design standard flexural strength. However, when the substitution rate is 30%, floating water is generated when the bending strength test piece is prepared, and it is difficult to apply it in the actual work, and there is a possibility that the surface property and the flatness may be deteriorated during the construction.

[Table 2]

[Table 3]

Next, the long-term bending and compression strength of 28 days, 90 days, and 180 days of age is evaluated at the rate of replacement of coal ash with cement, which is considered to be applicable in the actual work, at 0, 10 and 20%. It was measured. As a result, as shown in Tables 4 and 5, age 90
It was found that, with a long-term age of more than one day, the greater the replacement rate of coal ash with cement, the better the strength development. Since this contains a large amount of lime and gypsum, which are the characteristics of coal ash generated from a fluidized bed boiler, the long-term strength is enhanced by the hydration reaction and the pozzolanic reaction as a mixture of coal ash, cement and water. It is considered to be a thing. Also,
It is speculated that the irregular particle shape of the coal ash contributes to the improvement of the interlocking property of the aggregate in the compacted concrete and the improvement of the compaction property, thereby contributing to the enhancement of the long-term strength.

[Table 4]

[Table 5]

[0008]

[Examples] Based on the above test results, an example of practical use of a compacted concrete pavement material using coal ash generated from a fluidized bed boiler will be described. The coal ash of B in Table 2 was mixed with that of B in Table 3 (10% substitution of cement),
For comparison, a road was actually constructed using the material for compacted concrete pavement having a substitution rate of 0% of A in Table 3 and the effect on the actual road was confirmed. The road constructed is 10% of the roadbed CBR,
The roadbed thickness is 20 cm and the compacted concrete layer thickness is 20 cm. The amount of deflection on the compacted concrete layer during construction is shown in Table 6.
As shown in, the replacement rate of 10% is 0.05 mm, and the replacement rate is 0.
%, The flatness was 0.04 mm, and the flatness was 10%, the flatness was 1.51σ, and the substitution rate was 0%, the flatness was 1.52σ. It was confirmed that these values were similar to the surface texture and flatness of the conventional compacted concrete pavement, and the surface texture and flatness 180 days after construction were almost the same as those at the time of construction. In addition, as a result of measuring the bending strength for 180 days on the cut specimen of the compacted concrete layer of the road actually constructed in order to confirm the long-term strength, as shown in Table 7, 75% of the replacement rate is 10%.
It was 70 kg / cm ² with kg / cm ² and a substitution rate of 0%, and it was demonstrated that the long-term strength is improved by using coal ash as a substitute for cement.

[Table 6]

[Table 7]

[0009]

As described above, the coal ash generated from the fluidized bed boiler of the present invention is 10 to 20% by weight of cement.
The compacted concrete pavement material characterized by being replaced is similar to the conventional compacted concrete pavement using pulverized coal ash, has good workability even with a small amount of cement, and can be manufactured at low cost. In particular, compared to conventional compacted concrete pavements that use pulverized coal ash and those that do not, it is possible to improve durability over conventional compacted concrete pavement materials because of its excellent long-term strength development. , To open the way for expanding the use of coal ash generated from fluidized bed boilers,
It shows a remarkable effect.

[Brief description of drawings]

FIG. 1 shows the self-hardening property of coal ash generated from a fluidized bed boiler.

Claims (1)

(57) [Claims] 1. A compacted concrete pavement material composed of cement, water, coarse aggregate and fine aggregate, wherein coal ash generated from a fluidized bed boiler is mixed in an amount of 10 to 10 by weight ratio of the cement.
A material for compacted concrete pavement characterized by being replaced by 20%.