JPH10310457A - Concrete using coal ash and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily obtain a lightweight concrete having good water absorptivity and no cracks at a low cost to use coal ash as the source material by binding an aggregate essentially comprising coal ash and a cement with a cement to constitute the concrete. SOLUTION: An aggregate essentially comprising coal ash and a cement, preferably 7:3 to 9:1 ratio of the coal ash to the cement is bound with a cement, preferably by 7:3 to 9:1 ratio of the aggregate to the cement to obtain a concrete. The concrete is hardened by mixing coal ash, cement and water, preferably by 100 to 200 wt.% water to the cement, and then pulverized to prepare an aggregate. Then the aggregate is mixed with a cement and water preferably by 40 to 55 wt.% water to the cement, and hardened. A coal ash produced in a thermal power station can be used as the coal ash of this method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to concrete using coal ash and a method for producing the same.

[0002]

2. Description of the Related Art In a thermal power plant, a large amount of coal ash is produced by using coal as a fuel, and the produced coal ash is usually landfilled as industrial waste. In recent years, concrete in which cement is mixed with coal ash to harden the coal ash has been developed.

[0003]

However, the conventional concrete using only coal ash has a problem that cracks are easily generated.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a concrete using coal ash, which hardly causes cracks, and a method for producing the same.

[0005]

Means for Solving the Problems In order to achieve the above object, concrete using coal ash according to the present invention is obtained by combining an aggregate mainly composed of coal ash and cement with cement. Features.

[0006] The method for producing concrete using coal ash according to the present invention is a method of mixing coal ash, cement, and water, hardening the mixture, and then crushing the aggregate, cement, and water. , And cured.

The cement used is preferably Portland cement. The aggregates can be uniform in size or can vary considerably in size. Aggregate, even after hardening, shattered after some shrinkage subsided,
The material may be crushed immediately after curing to reduce the shrinkage to some extent. The amount of cement with respect to coal ash when making the aggregate is preferably 7: 3 to 9: 1, depending on the purpose of use. The amount of water for cement when making aggregate is 100% to 2%.
00% is preferred. The amount of cement relative to the aggregate when making concrete using the aggregate is preferably 7: 3 to 9: 1, depending on the purpose of use. The amount of water with respect to the cement when making concrete using the aggregate is preferably 40% to 55%.

[0008] In the concrete using coal ash according to the present invention, the coal ash can be recycled by using aggregate obtained by solidifying the coal ash with cement. Since the shrinkage of the aggregate after curing hardens to a certain extent, the concrete obtained by cementing the aggregate with cement does not shrink and does not crack. The concrete using the coal ash according to the present invention is lightweight and has good water absorption because the aggregate contains the coal ash. According to the method for producing concrete using coal ash according to the present invention, the concrete using coal ash according to the present invention can be easily produced.

[0009]

Embodiments of the present invention will be described below. As a first step, coal ash, Portland cement, and water were mixed by a mixer with the composition shown in Table 1, and the mixture was cured.

[0010]

[Table 1]

When the shrinkage had subsided 28 days after curing, the mixture was crushed by a crusher to produce crushed coal ash. The crushing was performed to such an extent that the crushed coal ash became the same size as the aggregate of general concrete. The compression strength, specific gravity and water absorption of the coal ash crushed stone on the 28th day after hardening were measured. The compression strength was 120 kg / cm ² , the specific gravity was 1.41 and the water absorption was 20.0.
Met. A general mortar using the same weight percent of standard sand instead of coal ash has a specific gravity of 2.5 and a water absorption of 0.2,
It can be seen that the manufactured coal ash crushed stone has a lower specific gravity and a higher water absorption rate than ordinary mortar.

Next, as a second stage, the aggregate of crushed coal ash prepared in the first stage, Portland cement, and water are mixed by a mixer according to the composition shown in Table 2, and the mixture is formed. The concrete was cured and manufactured using coal ash. In addition, what made the coal ash crushed stone into the surface dry expansion state was used for the aggregate.

[0013]

[Table 2]

When the compressive strength, specific gravity and water absorption of the concrete on the 28th day after hardening were measured, the compressive strength was 1
35 kg / cm ² , specific gravity 1.49 and water absorption 18.1. General concrete using the same weight percentage of gravel instead of coal ash in the composition of Table 2 has a compressive strength of 225 kg.
/ Cm ² , specific gravity 2.40, and water absorption 4.0, indicating that concrete using coal ash has a lower specific gravity and a higher water absorption than ordinary concrete.

The shrinkage of the concrete using the manufactured coal ash was measured at predetermined intervals. At the same time, coal ash, Portland cement, and water were mixed by a mixer with the composition shown in Table 1, and after mixing, the cured product (comparative example) was measured for shrinkage. Table 3 shows the results.

[0016]

[Table 3]

Table 3 shows that the concrete using the coal ash of the example has a much smaller shrinkage ratio than the comparative example in which the coal ash is not crushed. In particular, when the elapsed time after production is long, the difference from the comparative example is remarkable,
It can be seen that the shrinkage is remarkably small as compared with the comparative example, and cracks are hardly generated.

Concrete using the coal ash of the embodiment is as follows:
Cracks are less likely to occur without adding a crack inhibitor,
Since it is hard to crack even large products, it can be used for gateposts, lanterns, garden stones, revetment greening blocks, algae reef concrete, fish reef concrete and the like. In particular, when molded into a lantern or garden stone, it is porous and has good water absorbability, so that moss can be easily grown and aged and wavy feeling can be produced. Since the concrete using the coal ash of the example has a small specific gravity, when molded into a large product, it is lighter in weight and easier to transport than a general concrete. In the concrete using the coal ash of the example, after hardening, the aggregate slightly shrinks to form a slight pore around the aggregate, and is lighter and has better water absorption. Moreover, you may make a flowerpot with the concrete using the coal ash of an Example. The plant pot thus produced has good water absorption and air permeability, and is therefore suitable for growing plants.

[0019]

According to the concrete using coal ash and the method for producing the same according to the present invention, the coal ash can be used for concrete to recycle resources, and the produced concrete hardly generates cracks. The concrete using the coal ash according to the present invention is lightweight and has good water absorption.

Claims (2)

[Claims] 1. A concrete using coal ash, comprising an aggregate mainly composed of coal ash and cement bonded with cement. 2. A coal ash characterized by mixing and hardening a mixture of coal ash, cement and water, and then crushing the aggregate, cement and water. Concrete manufacturing method.