Comparison of Pre-Stressed Concrete, Partially Pre-Stressed Concrete and Reinforced Concrete in Terms of Different Aspects

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  • Topic: Concrete, Rebar, Reinforced concrete
  • Pages : 11 (2989 words )
  • Download(s) : 148
  • Published : October 26, 2011
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1.INTRODUCTION

1.1Background

The report will mainly focus on the differences between reinforced, prestressed and partially stressed concrete. These concrete reinforcing methods differ in the period they have been used. Reinforced concrete was developed by a nursery owner in Paris in 1867, Joseph Monier, applying it to practical use for the first time (Salmon & Wang, 2007). Prestressed concrete’s discovery dates back to the late 1800’s. Freyssinet was one of the first engineers who used this method and realised that, for this method, high quality concrete with very high tensile steel wires, stressed as high as possible was needed (Chris Burgoyne, 2005). The chief purpose of reinforcement methods is to strengthen concrete in its tensile capacity. Concrete can support loads when in compression, but it cannot handle any tensile stress, which leads to the cracking, shrinking and creeping of concrete. Therefore, reinforcement is placed at areas in the concrete where tensile stresses develop. In this report the reinforcement methods will for the most part be discussed in terms reinforcement in beams. Stresses in a beam develop as illustrated in the following figure:

Choosing the right methods of reinforcement for a specific concrete element will depend on the properties of the concrete mix and the materials of which the reinforcement is made. The properties of the materials include tensile strength, compressive strength, elasticity, creep and shrinkage, durability, expansion coefficient and other related properties. Other aspects, such as the economical implementation and resources, must also be taken into account when choosing reinforcement.

In practise the best method of reinforcement to apply in concrete, in a specific structure, has to be identified in order to be able to design an appropriate structure which can uphold the forces that act upon it. The properties of the reinforcement thus have to be known.

The report discusses the different uses and properties of reinforced concrete, prestressed concrete and partially prestressed concrete to finally determine which method would be appropriate for a specific application. The report further elaborates on the types of methods used for reinforcement.

2.REINFORCED CONCRETE

Reinforced concrete was invented by Joseph Monier in 1849, who recognized and applied its potential uses (Salmon & Wang, 2007). Reinforced concrete is used to eliminate tensile stresses in concrete. By reinforcing the concrete, its ductility and toughness is enhanced. Reinforced concrete is installed by placing bars, grids, plates of fibres on strategic positions in the cement mix when casted. Ferroconrete is iron or steel reinforced concrete (http://www.encyclopedia.com/doc/1O1-ferroconcrete.html). The different types of reinforced concrete includes in-situ concrete (concrete is poured into a cast and reinforcement placed in on site) and precast concrete (concrete parts are manufactured and reinforced at a factory and ready to use on site) (Curry, 2011).

2.1Types of reinforcement used

STEEL REBAR
Textured steel rods are placed in the concrete when it is poured. During curing the concrete then adheres to the rebar allowing stress to be transferred between the different materials, thus transferring the tensile stresses which form in the concrete, to the steel rebar (Darwin et al., 2003). STEEL PLATE

Steel plates are used in the place of rebar. It takes less time to fix the plate to the concrete and it often has higher strength, because it is placed on the outside where the tensile stress is the greatest. Occasionally, steel plates are used when maintaining a concrete element (Darwin et al., 2003). FIBER REINFORCED CONCRETE

This concrete compound consists of glass, steel or plastic fibers and is mostly used in ground floors and pavement. The cost of fiber reinforced concrete is relatively low (Darwin et al., 2003). NON-STEEL REINFORCEMENT

This type of...
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