Basalt fiber as reinforcement for lime-based mortars
Natural fibers have been used in order to upgrade workability and toughness of concrete, mortars, and even bricks since early history, but they have ever shown problems related to their durability and resistance against bio-deterioration. After the building science revolution consisting of cement concretes, the use of traditional natural lime concrete and mortars sensibly diminished. Materials of tradition have been recently re-discovered due to their bio-compatibility, but their performances are still inferior to the ones of cement concrete. The present overall research aims at the improvement of mechanical and physical characteristics of traditional natural materials such as lime-mortars and concrete through the use of different types of natural fibers. Amongst the possible natural fibers, basalt ones were chosen as first case study because of the excellent results shown in other applications, their quite recent entrance into the industrial market and their environmentally friendly character. The purpose of this phase of the research was the optimization of the content and type of basalt fibers necessary to improve the behavior of a traditional natural hydraulic lime-mortar. It is well known that the incorporation of short fibers in mortar and concrete products can reduce plastic shrinkage, as well as improve some of their properties such as toughness, flexural strength and durability. Samples of a natural hydraulic lime (NHL) based mortar studied in comparison with ones mixed using cement as binder have been prepared and investigated through physico-mechanical tests as per Italian and European regulations. The results of this preliminary step will be used to perform the subsequent phases, including the assessment and comparison of the effects of several commercial types of fibers on mechanical and chemical properties of the ensuing mortars.