Lightweight Pumice Mortars with Polypropylene Fiber Reinforcement

The use of porous particles as aggregates in cementitious mixes presents advantages such as reducing dead load and assisting in thermal insulation of constructions. Pumice aggregates are most commonly used because they are cheap, natural and easily obtainable. However, there are also disadvantages such as brittle behavior and decrease in strength. In this study, 0, 1 and 2 vol% polypropylene fibers (PF) having 40 micrometer diameter were used in the production of mortars containing acidic (AP) and basaltic pumices (BP) in place of calcareous sand (CS), in order to overcome these challenges. In addition to mechanical properties (compressive, flexural and splitting tensile strength), physical properties (bulk density and capillarity) and morphology of mortars (scanning electron and optical microscopy) were also investigated. The results showed that bulk density of BP mortars was about 10% lower and that of AP mortars was about 15% lower than that of CS mortars. Flexural strength of BP and CS mortars were over 7 MPa, whereas that of AP mortars were in 4–6 MPa range. Addition of 1% PF improved the mechanical properties, whereas addition of 2% PF resulted in a decrease in strength in all mortar types. The highest 1-year compressive strength was obtained by the BP sample having 1% PP fiber. Furthermore, there was a strong relationship between the strength and bulk density of mortars.