Materials’ Properties

MATERIALS’ PROPERTIES

• Concrete is a composite material, comprising a fibre (in the form of aggregate), and a matrix resin (in the form of a cement and water paste). • Inherently, this produces an extremely resilient and hard-wearing material: one that is very resistant to water,wind and chemical erosion, and also has a high Compressive Strength. That said, its relatively low Tensile Strength means that steel Reinforcement Bar (Rebar) may be a beneficial and worthwhile addition. • Concrete is, however, slightly porous, so the steelwould be vulnerable to corrosion from the sea water. This may lead to spalling, whereby small fragments of concrete are gradually disintegrated from the rest of the structure by the corrosion of the Rebar inside. • Moreover, freeze-thaw action will prove a major issue if water becomes trapped within the structure, because it will have the effect of breaking the material apart as the ice expands. • This information will prove extremely useful indeed, as it provides us with a vital insight into exactly what we are dealing with, and what complications must be allowed for in the use of concrete. For example, we know now that the concrete alone is not enough to protect the steel Rebar (needed to overcome the concrete’s lack of SPALLING OF CONCRETE Tensile Resilience) from corrosion, and some form of Galvanisation is therefore imperative so Source: upload.wikimedia.org as to evade spalling. Retrieved: April 3rd 2012 • We were aware from the beginning that Laing O’Rourke’s concrete is a highly-specialist material, whose performance characteristics are not only closely-guarded, but also are such that very specific manufacturing conditions are required. This would obviously influence us in our decision as to how and where the concrete should be manufactured, and whether the best option would be to cast the tower in dry dock, or to pre-fabricate structural panels and assemble these in the dock instead.