Natural Pozzolanic Mortars. Ancient Indications for Modern Working Capacity

The paper deals with the mechanical behavior of lime mortar with natural pozzolana, widely used in historical masonry. The research undertaken at the University of Brescia, demonstrated how the use of pozzolana in the mortar was well known by architects and engineers since the II-I century b.C.. The first information about the use of this material can be found in Vitruvius’ De Architectura. Later, many authors referred to pozzolana in their architectural treatises as well, but they didn’t give practical and technical information on the use of this volcanic material. Only between the end of the XVIII and the first half of the XIX century, up to the Sixties, architects and engineers turned their attention to the practical uses of this volcanic material. From the mechanical point of view, the effectiveness of pozzolana, as natural addictive for mortar, is strictly connected to its chemical and physical characteristics. The power of the pozzolanic reaction derives, as a matter of fact, from different aspects: the main features are the dimension of the pozzolana grains and the percentage of the different chemical component of the pozzolana. The first one depends on the mining method and the next grinding of the pozzolana, the second one hinges on the geological nature of the volcanic material. The study aims at investigating the large unevenness of these parameters and tries to provide first mechanical indications needful for using pozzolanic mortars.