# Life Cycle Assessment of Mortars Produced Partially Replacing Cement by Treated Mining Residues
## 4 Conclusions  
The decarbonisation of the power sector and the implementation of materials' strategies will be important drivers towards a net zero carbon emissions in the construction industry. In particular, the incorporation of innovative circular materials and products, that can be recovered in closed-loop systems, could contribute to decrease the environmental burdens from cement uses in mortars. Although technological and commercial viable solutions exist, stronger policies and collaborations to accelerate scale up are crucial. Aiming to provide a decision-making tool for future developments, while keeping up with the technological progress, this work presents a LCA methodology to quantify the sustainability of mortars produced with secondary mining resources partially replacing cement. Considering six environmental categories, 1 t of 10 different mortars were analysed: a reference mortar (100% of CEM II/B-L 32.5 as binder) and mortars with cement substitutions in 10%, 25%, and 50% by raw, electrodialytic treated and electrodialytic plus thermal treated mining residues. * Generally, mortars produced with mining residues presented an eco-friendlier behavior than the reference mortar. The use of mining residues as binder can avoid almost 50% of the GWP, meaning the release of 55.1 kg CO\({}_{2}\) eq./t modified mortar. The lower the cement content, the lower the energy involved in mortar production, namely due to the clinker formation that requires temperatures above 1000 \({}^{\circ}\)C and energy consuming milling. * The adoption of mining residues management scenarios, before their reuse in mortars' manufacture, was assessed considering direct disposal, ED treatment and ED treatment coupled with a thermal procedure. Herein, the impacts of mortars were strongly alleviated in POCP (\(-\)99%), ODP (\(-\)76 to \(-\)98%) and AP (\(-\)90 to \(-\)94%), comparing to the reference. The avoided mining residues discharges were key factor for these decreases, together with lower cement incorporation. * The overall mortar lifecycle was performed considering all the mortar components and respective management scenarios. The aggregate fraction demonstrated higher impact weight in ODP (between 46 and 78%), while the typology of the binder applied showed different environmental performances. ED mining residues showed higher representativity in POCP (53%) and ODP (52%), whereas ED plus thermal treated mining residues contributed to 64-84% of the POCP, and to almost 100% of the ADP. * Cement has a significant expression in ADP (almost 100%) and GWP (51-97%). The impacts of mortars with treated mining residues are mainly caused by cement contents, even at higher replacement ratios. Nevertheless, fossil fuels needed for the thermal treatment of mining residues increased the resources required, promoting a higher ADP than cement. Furthermore, other stages not considered in the present work may influence the embodied energy of mortars, namely construction, use and end-of-life phases. The energy spend on grinding activities can differ from material to material, and according to industrial methods. Scaling up approaches and the increase of renewable energy in the grid will be important steps to decrease the impacts of fossil fuels consumption during the involved processes. The cost analysis of the mortars produced by partial replacement of cement with treated mining residues could also complement the life-cycle assessment. This step is relevant to evaluate the economic feasibility of the mortars in the current market and correlate data with the environmental benefits observed. Conceptualization, J.A. ; Data curation, J.A. ; Formal analysis, P.F., A.B.R. and A.S.S. ; Funding acquisition, P.F. and A.B.R. ; Methodology, J.A. ; Project administration, P.F. and A.B.R. ; Resources, P.F. and A.B.R. ; Supervision, P.F., A.B.R., and A.S.S. ; Validation, P.F., A.B.R., and A.S.S. ; Writing--original draft, J.A. ; Writing--review and editing, J.A., P.F., A.B.R., and A.S.S.