The effect of pozzolans addition on cement mortars

The addition of microsilica was widely used in concretes and mortars since the second half of the 20th century (in high and very high strength concretes). Silica fume consists of very fine spherical particles. This additive, thanks to its properties, fills the space between cement particles and aggregates which affects: porosity, watertightness, shrinkage reduction and increased strength. The microsilica has pozzolanic properties and reacts with calcium hydroxide and gradually forms a uniform and continuous contact phase C-S-H (calcium-silicat hydrate). The interfacial zone between cement paste and aggregate has been considered as a zone of weakness. Zeolite is a material lesser known in civil engineering which can be used as an alternative to microsilica. The article presents the investigation of the physical properties of mortars containing these two types of pozzolan. In mixes pozzolan additives at 0 to 20 percent by mass of portland cement are used. Testing of such properties of fresh mortar as workability and air content was carried out. The properties of hardened mortar such as strength, water absorption, frost resistance and capillary suction were also determined.