Use of Fluidized Bed Combustion Fly Ash as Addition Reducing Shrinkage of Concrete

Abstract

Volumetric changes during ageing belong to natural properties of concrete. These changes, either growing or shrinking, can present a problem, which has to be taken into account during design and realization phases. This phenomenon is influenced by various factors and volumetric changes can be eliminated in many ways. One of the possibilities is setting appropriate combination of input materials and use of special additions and admixtures. This paper focused on verification of the method reducing shrinkage of concrete by means of using high temperature combustion fly ash combined with fluidized bed combustion fly ash as addition. The precondition is growth of new forms, in particular primary ettringite and monosulphate, which form because of the content free lime and sulphates in fluidized fly ash. If these minerals are formed in fresh concrete, they can positive prevent shrinkage without destruction of the composite material.