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Ferrovial Agroman

(Ferrovial) New Construction Materials

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In order to manufacture high-strength concrete, the following are necessary:

  • A detailed analysis of the concrete formula and comparison with tests.
  • Proportioning of aggregate must be sufficiently precise and homogeneous.
  • Use of high-strength cement.
  • Monitor the water content, taking into account that in the aggregate and additives.
  • Use of additives which reduce the water to enable formulas with a low water/cement ratio, and a cone for application.
  • Use of silica fume in order to fix the free lime.

Today, most concrete plants used in public works projects fully comply with the first five points. In order to manufacture high-strength concrete (e.g. H-650), it is necessary only to add more superfluidiser and a certain percentage of silica fume to the regular H-300 or H-350 concrete. This reduces the cost of producing high-strength concrete and enables it to compete with solutions based on ordinary concrete.

As with many technological advances, this type of concrete is only successful if:

  • The new technology results in significant monetary savings.
  • The new technology makes it possible to do what was previously impossible, and the customer is willing to pay for them.

Regarding the first case, in the piling for medium-span bridges (about 30 m.), high-strength concrete reduces not only the number of pillars but also their diameter. One such example is the bridge over the Miño.

Regarding the second case, high-strength concrete can be used to reduce the dimensions of structures for purely esthetical considerations. The Archena truss bridge is an example: the tower dimensions were such that the bridge could not have been built using ordinary concrete.

These two cases necessitated high levels of compression, for which high-strength concrete is aptly suited because increasing the characteristic strength is equivalent to increasing the area without increasing the overall dimensions. Structures subject to simple bending have other requirements, such as durability, compactness, low flow coefficient.