A backfill concrete product containing slags obtained from high carbon ferrochrome production furnaces as aggregate raw material

Abstract

The invention relates to a backfill concrete product containing slags obtained from high carbon ferrochrome production furnaces as aggregate raw material.

Description

[0001] DESCRIPTION

[0002] A BACKFILL CONCRETE PRODUCT CONTAINING SLAGS OBTAINED FROM HIGH CARBON FERROCHROME PRODUCTION FURNACES AS AGGREGATE RAW MATERIAL

[0003] TECHNICAL FIELD

[0004] The invention relates to a backfill concrete product containing slags obtained from high carbon ferrochrome production furnaces as aggregate raw material.

[0005] PRIOR ART

[0006] Concrete is a material made by mixing cement, natural or artificial coarse aggregate, water and, when necessary, chemical or mineral additives and gains strength with the hydration of cement. Backfilling in mining is the process of partially or completely filling a space opened by production using hand, gravity, mechanical, pneumatic and hydraulic tools. The development and utilization of backfilling technology in the world has made great progress in the last two decades. The mining industry is particularly interested in this technology for filling large production open spaces underground. The concretes prepared for this purpose are called backfill concrete. Backfill concrete recipes generally consist of cement, aggregate, and water components. In backfill concrete, the change is usually in the aggregate used.

[0007] According to their sources, aggregates generally have two origins as natural aggregates (sand-gravel, crushed stone) and artificial aggregates (blast furnace slag, perlite). Natural aggregates are obtained from natural sources such as creeks, streams, lakes, plains, sea beds, deserts or quarries. Natural aggregates obtained without any chemical treatment are crushed in crushing machines called crushers and subjected to the washing process. In quarries, natural rocks are obtained in large blocks as a result of blasting. These boulders are then transported by trucks and crushed by crushers at the quarry plants. As a result of the process carried out to make it suitable for the concrete mixture, aggregates of various sizes are obtained according to the sectors. Artificial aggregates, on the other hand, are crushed or unbroken aggregates that emerge as a by-product exposed to high temperatures as a result of industrial processing. These aggregates, which are industrial products, are blast furnace slag, fly ash aggregate, expanded perlite, and expanded clay artificial aggregates.

[0008] Ferrochrome slags are formed during physico-chemical processes in electric arc furnaces of ferrochrome production plants. Ferrochrome slags (high carbon ferrochrome slag) are inactive and gain a crystalline form due to being left to slowly cool in the air. This type of slag is therefore called “Air Cooled Electric Arc Furnace Slag”. Slag in this form has high mechanical properties and is mostly used as aggregate. However, these slags have different elemental contents due to factors such as the raw material from which they are obtained, the region where they are located, and the firing processes. Therefore, the ferrochrome slag obtained in each ferrochrome plant differs characteristically.

[0009] Most of the ferrochrome slag obtained from furnaces is stored in stock and storage areas. However, these stocks cause environmental problems. Environmental problems such as air, soil and water pollution affect human health and plant growth. This situation is becoming an issue that needs to be prevented day by day or requires different uses for ferrochrome slag to be created.

[0010] Earthquakes that have occurred in recent years have shown that the use of concrete wastes obtained from buildings destroyed in earthquakes as filling on beaches creates very inconvenient situations. In addition, another reason is that there are no natural resources in large settlements, and the resources that are available are far from the city center, which increases the costs of transporting these heavy materials. Another reason is that 75% of collapsed buildings are made of concrete, and this waste concrete is disposed of without any utilization, leading to loss of space and environmental pollution in the places the wastes are disposed. Aggregate constitutes 55%-80% of concrete. If alternative aggregate sources are not found, the concrete industry will consume 8-12 billion tons of natural aggregate every year in the world after 2010. Therefore, decreasing raw materials, increasing transportation costs and environmental impacts have brought recycling aggregates to the limelight.

[0011] As a result, all the above-mentioned problems have made it imperative to make an innovation in the relevant technical field. SUMMARY OF THE INVENTION

[0012] The inventors of the present invention propose that the slags obtained from the high carbon ferrochrome production furnaces should be researched and developed as a reusable raw material. For this purpose, it aims to introduce technical teachings on the use of aggregate as raw material, especially in backfill concrete products.

[0013] Accordingly, the primary object of the present invention is to introduce a backfill concrete containing slags obtained from high carbon ferrochrome production furnaces.

[0014] The other secondary object to be achieved with the realization of this is to ensure that these technical problems are avoided by including the slags obtained from ferrochrome furnaces, which are difficult and costly to store, in a value-added product.

[0015] Another secondary object is to reduce the costs of backfill concrete products by using slags obtained from ferrochrome furnaces as aggregate raw materials.

[0016] BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Fig. 1 shows a representation of the values related to the strength of the backfill concrete.

[0018] DETAILED DESCRIPTION OF THE INVENTION

[0019] In this detailed description, the subject of the invention relates to a backfill concrete product containing slags obtained from high carbon ferrochrome production furnaces as aggregate raw material, and is described by way of non-limiting examples only for a better understanding of the subject matter.

[0020] High carbon ferrochrome is an alloy with a chromium ratio of 60-70% by weight and a carbon ratio of 4-9% by weight. High carbon ferrochrome is the most common type of ferrochrome used in steelmaking. It is preferred in the production of high-strength and wear-resistant steel alloys. Because of its high carbon content, high-carbon ferrochrome plays an important role in adjusting and controlling the hardness, strength, and other mechanical properties of steels. In the relevant technical field, it is known that a material must contain certain components in order to be used as aggregate and to provide the expected technical properties to the final product backfill concrete. The most important of these components are MgO, SiO2, and AI2O3 components. It is also clear that they must be in certain weight ratios. Therefore, it is necessary to research whether the raw materials to be used as aggregates contain these components. Technical teachings regarding why these components are included in the raw materials to be used as aggregates are known by experts in the art. For this reason, the technical solutions and advantages of these components as aggregate raw materials are not mentioned.

[0021] Accordingly, the inventors of the present invention propose the use of slags obtained from high carbon ferrochrome production furnaces as aggregate raw material as aggregate raw material for backfill concretes.

[0022] The inventors of the present invention have attempted to prove the technical properties of the slags obtained from the high carbon ferrochrome production furnaces and their usability as aggregate raw materials with some tests for the relevant technical field.

[0023] Firstly, elemental analysis is carried out as in Table 1 to determine the suitability of using the slags obtained from high carbon ferrochrome production furnaces as aggregate material.

[0024] Table 1. Elemental analysis of high carbon ferrochrome slag of the invention.

[0025] It comprises SiO2in the range of 25% to 35% by weight, MgO in the range of 30% to 40% by weight, and AI2O3 in the range of 20% to 30% by weight for its use as an aggregate material in the backfill concrete product of the invention. In addition, it comprises Cr2O3 between 3% to 6% by weight and Fe2O3 between 1% to 3% by weight, and these components positively affect the compressive strength. With these values it contains, its use as an aggregate material of the backfill of the present invention is proven by tests.

[0026] The values given in Fig. 1 show the uniaxial compressive strength values of backfill concretes containing slags obtained from high carbon ferrochrome production furnaces as aggregate material. Accordingly, processes are applied with 5 samples to perform these tests.

[0027] Compressive strength of concrete is the highest mechanical strength resistance of concrete in order not to break under the influence of axial load. The most researched issue in concrete is the compressive strength of concrete. What is crucial for concrete is the relationship between compressive strength and stress-deformation under pressure. The compressive strength of concrete is a function that changes over time and takes its final strength after years. Considering the strength values expected from the backfill concrete, uniaxial compressive strength values are achieved as a value of 20 MPa for 7 days, 25 MPa for 14 days and 27.5 MPa for 28 days for the average values of the samples. With these values, it is determined that the slags obtained from high carbon ferrochrome production furnaces used as aggregates are suitable for use as aggregates in backfill concrete due to their uniaxial strength properties being within acceptable limits and even more. Thus, in these experimental studies, it is seen that sufficient strength expected from backfill concrete is provided.

[0028] The backfill concrete product of the invention contains slags obtained from high carbon ferrochrome production furnaces as aggregate raw material at a value in the range of 55% to 90% by weight.

[0029] The scope of protection of the invention is specified in the appended claims and cannot be limited to what is described for illustrative purposes in this detailed description. It is clear that a person skilled in the art can produce similar embodiments in the light of what is explained above, without deviating from the main theme of the invention.

Claims

CLAIMS1. A backfill concrete product containing slags obtained from high carbon ferrochrome production furnaces as aggregate raw material.

2. A backfill concrete product according to claim 1 , characterized in that it contains slags obtained from high carbon ferrochrome production furnaces as aggregate raw material at a value in the range of 55% to 90% by weight.

3. A backfill concrete product according to one of the preceding claims, characterized in that the slags obtained from said high carbon ferrochrome production furnaces contains SiC>2 at a value in the range of 25% to 35% by weight, MgO at a value in the range of 30% to 40% by weight, AI2O3 at a value in the range of 20% to 30% by weight, Cr2O3 between 3% to 6%, and Fe2Os between 1% to 3% by weight.

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