Reuse of waste rockwool for improving the performance of LC3-based mortars made with natural and recycled aggregates for sustainable building solutions

The objective of this study is to investigate the effect of waste rockwool (RW) addition on the thermo-physical, mechanical, and fire resistance properties of limestone calcined clay cement (LC3)-based mortars. LC3 binder has been produced by replacing 60 wt% of OPC with limestone (LS) powder and metakaolin (MK) at a percentage of LS to MK of 1:2 (wt%). Waste RW was added at various ratios of 1, 3 and 5 % (by weight of binder) into two types of LC3-based mortars made with natural sand (NS) and ferrochrome waste slag (FCS) aggregates with a binder-to-aggregate vol% of 1:3. Upon the addition of 5 wt% of waste RW, significant enhancements of about 19 % and 21 % were obtained for the compressive strength of NS and FCS mortars, respectively, and attributed to the improved physical packing. After exposure to standard fire for 1 h with a maximum applied temperature of 945 degrees C, residual strengths of about 57.5 % and 63.8 % have been maintained by the sand and FCS-blended LC3 mortars, respectively. Generally, the incorporation of RW led to a slight increase in the thermal conductivity of both types of mortars; however, the FCS-blended LC3 mortar possessed relatively higher increment rates as compared with the sand mortar, which is helpful in improving the thermal performance in hot climate regions. Remarkable improvements in the microstructure characteristics in terms of compactness, uniformity, and interfacial transition zone (ITZ) tightness were attained by RW addition. Lifecycle assessment (LCA) results demonstrated that about 38-45 % lower carbon emission is associated with the designed LC3-based mortars than the conventional OPC mortar.