| Abstract [eng] |
The master's thesis reviews the possibilities of using secondary raw materials in civil engineering field. Test object – composite concrete produced by using ordinary concrete mixture incorporating rubber and steel cords as well as steel wires from tire waste. In order to investigate the efficiency and rational usage of such concrete, a literature review and experimental tests were completed. The literature review discusses the influence of rubber on the main physical properties of concrete: density, porosity, water absorption, fire and cold resistance, as well as microstructural changes. Mechanical properties section discusses the impact of rubber on the compressive, tensile and bending strengths of concrete, changes in the modulus of elasticity. Based on the literature, the use of steel fibres in concrete and reinforced concrete structures and mechanical properties are discussed. The testing part examines samples made of composite and depressively reinforced concrete with secondary raw materials obtained during tire utilization process. Compressive, bending, cracking strength tests and tests for determination of frost resistance as well as modulus of elasticity of the samples were performed. An additional tensile test of steel cords and wires was also performed. It was observed that the compressive strength is lower in rubber-containing concrete specimens than in the control mix concrete specimens. Determination of the modulus of elasticity show that the use of rubber in the concrete mix slightly reduces the modulus of elasticity of such concrete. The cold resistance tests were performed by subjecting the samples to 200 and 275 freeze-thaw cycles. All tested concrete specimens withstood the cycles, but it was observed that rubber-containing concrete has higher frost resistance. Conducted experiments of rubber-containing concrete are summarized that it is effective to use of tire waste rubber in concrete mixes, but higher amounts of rubber can lead to a deterioration in the mechanical properties of such concrete elements. The flexural strength of steel tire cord and wire reinforced specimens was evaluated by a beam triaxial bending test, which results showed that, under bending conditions, the reinforcement of concrete specimens with steel cords and wires is no less effective than with the use of certified steel fibres. In order to more accurately determine the rational usage of steel tire cords when using them for dispersive concrete reinforcement, the tensile strength of the cords is determined. Tensile test results showed that steel tire cords and wires have none the less tensile strength as certified steel fibre. The results of these studies suggest that steel cords and wires can be rationally used as a substitute for the prevailing steel fibres on the market. Thesis structure: number of tables – 17; number of pictures – 39; number of bibliographic records – 39. |
