Effects of Expanded Perlite Production Waste and Curing Conditions on the Properties of Pozzolanic Lime Mortars

This study investigates expanded perlite production waste (EPPW), an under-valorized industrial by-product, as the main pozzolanic component of lime mortars at high replacement levels, aiming to reduce conventional binder demand. To this end, mortars were prepared with 50%, 67%, and 75% EPPW by binder mass and subjected to air, water, and accelerated heat curing. Their physical, hygric, and mechanical properties were assessed, including porosity, capillary water absorption, water vapor diffusion resistance, ultrasonic pulse velocity, flexural and compressive strength tests, supported by XRD and DTG analyses. EPPW exhibited pozzolanic activity, and the highest compressive strength, about 10 MPa, was obtained at 67% replacement after 7 days of heat curing and 90 days of water curing. Under the same curing conditions, the 50% replacement level provided the lowest water and vapor transport, whereas 75% EPPW increased transport properties. As EPPW requires only grinding, grinding emissions were estimated at no more than about 3% of those avoided by the lime it replaces. The results indicate that EPPW can be upcycled into pozzolanic lime mortars potentially suitable for non-load-bearing applications such as rendering, plastering, and historic building conservation, although hygric performance, compatibility, and long-term durability require further investigation.