Potential of siliceous fly ash and silica fume as a substitute for binder in cementitious concretes

Nowadays, concrete constructions are often erected from a material that has been modified with mineral additives or chemical admixtures. Thanks to such modifications, modern and innovative visions of architects and constructors are realizable. Modification of concrete microstructure with mineral additives results in a partial change of its properties as well as physical and mechanical parameters. Ecological and economic reasons are an additional cause of increased interest in the potential use of such additives as fly ash (FA), silica fume (SF), lime powder or granulated blast-furnace slag. The basic physical mechanism of interaction of FA and SF with concrete is primarily to seal the composite microstructure. In the paper a concrete modified with a constant amount of densified silica fume, and a variable percentage amount of siliceous fly ash was analyzed. Concrete samples have been subjected to mechanical and physical tests. Their results allowed to determine the optimal composition of a concrete mix containing the mineral supplements in the context of planned experiments. The use of a combined SF and FA additive as a substitute for a cement binder in a concrete mix allows for an optimal increase in the strength parameters of the concrete, thus not degrading its physical properties. The article presents the characteristics of materials used to make concretes and then analyzes the results of the composites' tests. An in-depth analysis of the results showed the usefulness of silica fumes and siliceous fly ashes as useful raw materials for a concrete production