Recycled railway concrete sleeper produced by alkali activation

Abstract

The invention relates to a concrete sleeper, which is a load-bearing superstructure element of a railway, produced by alkaline activation from recycled material and providing high strength, and which comprises steel fiber, sodium hydroxide (NaOH) and / or sodium silicate (Na2SiO3) and alkaline activated geopolymer concrete.

Description

[0001] RECYCLED RAILWAY CONCRETE SLEEPER PRODUCED BY ALKALI ACTIVATION

[0002] Field of the Invention

[0003] The invention relates generally to structural elements used in railways. In particular, the invention relates to a concrete sleeper, which is a load-bearing superstructure element of a railway, produced from recycled material by alkali activation and providing high strength.

[0004] State of the Art

[0005] One of the means of transport used today is railway transport. The structure that allows the train used in railway transport to move on the railway consists of concrete sleepers, which are the carrier structure, and the rails on which the train travels by positioning on the concrete sleepers. High strength traditional Portland cement based binder materials are used in the production of prestressed concrete sleepers used in railway applications. In concrete elements produced for use in railway superstructure projects, construction materials with strength class C60 (60 MPa compressive strength) are used. In order for the railway elements produced to reach this strength value, high cost additives are used and curing processes are applied.

[0006] Portland cement used in concrete production is the most widely used construction material and at the same time, it is the building material that causes the highest carbon dioxide emissions in nature during its production. In recent years, in order to ensure a sustainable future in the world and to combat global change, it is of great importance to reduce carbon emissions and to utilise the captured carbon dioxide. It is known that a significant percentage of carbon dioxide emissions in the world (8%) is caused by the construction sector. Considering that concrete is the most consumed material in nature after water, it is aimed to reduce carbon dioxide emissions and prevent global warming by using recyclable materials by reducing the cement used in concrete and using alternative new materials instead.

[0007] As a result of the use of Portland cement in superstructure elements, there are high energy costs and negative effects on the environment. Against these negative effects, it is of great importance to develop new alternative recyclable materials without cement.

[0008] The application numbered TR2019 / 20343 is related to ‘Boron fiber reinforced polymer reinforced strategic, domestic railway sleeper’. In this application, it is stated that the railway sleeper is produced from boron fiber reinforced polymers. However, the said polymers are added in the concrete where cement is used. This application does not mention the use of recycled material in the production of sleepers.

[0009] Application EP2946036B1 relates to a railway sleeper. This application relates to a railway sleeper comprising a concrete body having a sleeper base, in which fibers are bonded to the sleeper base on the one hand and to the concrete body on the other hand in order to bond the sleeper base to the concrete body in such a way that the sleeper base can withstand the separation force, and which partly concerns the embedding of the concrete body for its concrete. However, this application does not mention the use of recycled material in the production of sleepers.

[0010] As a result, improvements are being made in the sleepers used in railways, therefore, new structures are needed to eliminate the disadvantages mentioned above and to bring solutions to the existing systems.

[0011] Aim of the Invention

[0012] The present invention relates to a concrete sleeper which fulfils the above-mentioned requirements, eliminates all disadvantages and brings some additional advantages.

[0013] The main purpose of the invention is to provide a concrete sleeper, which is an environmentally friendly green concrete superstructure element produced by improving the mechanical properties of recycled materials by innovative alkaline activation method.

[0014] One object of the invention is to provide a self-repairable concrete sleeper which provides both high bonding capacity and ultra-high strength properties thanks to the steel fibers used.

[0015] Another object of the invention is to provide a sustainable railway element by using recyclable materials without using cement in the concrete sleeper produced. Another object of the invention is to provide a long-lasting railway superstructure element which is resistant to environmental influences with cement-free concrete sleepers.

[0016] In order to realise all the advantages mentioned above and to be understood from the detailed description below, the present invention is a concrete sleeper used as a carrier superstructure element in the railway;

[0017] - Steel fibre,

[0018] - Sodium hydroxide (NaOH) and / or sodium silicate (Na2SiO3)

[0019] - A structure containing alkaline activated geopolymer concrete was obtained.

[0020] The structural and characteristic features and all advantages of the invention will be more clearly understood by means of the figures given below and the detailed description written with reference to these figures. Therefore, the evaluation should be made by taking these figures and the detailed description into consideration.

[0021] Detailed Description of the Invention

[0022] In this detailed description, the preferred embodiments of the inventive concrete sleeper are described solely for the purpose of a better understanding of the subject matter and without limitation.

[0023] In its basic form, the concrete sleeper of the invention consists of steel fiber, sodium hydroxide (NaOH) and / or sodium silicate (Na2SiO3) and alkali activated geopolymer concrete. The steel fiber in the concrete sleeper improves the compressive and flexural strength properties of the superstructure elements and prevents damage. Preferably 2% steel fiber is used in the invention. In a preferred embodiment of the invention, the concrete sleeper element developed comprises blast furnace slag as a binding agent. The concentration of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) used in the invention is preferably 9, 12 and 15M.

[0024] In an exemplary embodiment of the invention, geopolymer concrete is produced by considering NaOH concentration and Na2SiO3 / NaOH ratio. The 7 and 28 day compressive strengths of the produced geopolymer concretes are analysed. With the structure presented in the invention, instead of superstructure concrete sleeper products produced using traditional Portland cement, recycled materials are used in new generation cementless pre-cast elements produced by alkali activation. As a result of the tests, a high performance building material that can reach ultra-high strength values (140 MPa) has been introduced to the industry. A steel fiber reinforced superstructure railway element with high strength properties was cured in water environment. In this way, low cost and high strength superstructure material can be used in railway construction works for long periods of time without the need for maintenance and repair. In addition, the materials released as a product are recycled back into production, making a significant contribution to the circular economy.

[0025] As a result, thanks to the steel fibers it contains, an ultra-high strength, maintenancerepair operations are significantly reduced and a long-lasting superstructure concrete sleeper element has been brought into production. In addition to all these, the inventive concrete sleeper can be used in a wide range of areas in the railway industry.

Claims

CLAIMS1. Concrete sleeper used as a load-bearing superstructure element on the railway, characterised by- steel fiber,- sodium hydroxide (NaOH) and / or sodium silicate (Na2SiO3),- alkaline activated geopolymer concrete.

2. Concrete sleeper according to claim 1 , characterised in that it contains 2% steel fiber.

3. A concrete sleeper according to claim 1, characterised in that the sodium hydroxide and sodium silicate are in a concentration of 9M or 12M or 15M.

4. A concrete sleeper according to claim 1, characterised in that the ratio of sodium hydroxide and sodium silicate used in the concrete sleeper is 1 / 1.