Circular design, material properties, service life and cradle-to-cradle carbon footprint of lime-based building materials.

The massive extraction of virgin raw materials has substantially intensified the focus on circular economy of building materials. As a Cradle-to-Cradle service life and circular approach for lime-based construction materials (LBCM) is lacking, the present study evaluates the environmental impact and feasibility of creating a fully recycled second-life render (SL) by designing a closed-loop upcycling process for first-life renders (FL). To achieve this, a second-life binder was thermally activated (900, 1000, 1100, 1200 °C), while its microstructure, compressive strength, and thermal conductivity were investigated. SL had up to 33 % open porosity (FL 29 %), its compressive strength ranged from 2.5 to 3.4 MPa (FL 4.4 MPa) and the thermal conductivity from 1.002 to 1.107 W/mK (FL 1.231 W/mK). Resistance of SL and FL against sulfate attack was found to be equivalent, measured based on the recent RILEM TC 271-ASC recommendation. The environmental impact indicators integrating material properties and durability confirm that the second life-render can reduce CO2 emissions up to 55 %. The present research provides insights into unlocking essential sustainability gains through circular practices in the life-cycle of LBCM.