# Life Cycle Assessment of Mortars Produced Partially Replacing Cement by Treated Mining Residues
## 3 Results and Discussion
### Impacts of Raw Materials in Mortar Manufacture
When 50% of cement was replaced by secondary mining resources (M50), a decrease of 49% in GWP was achieved (55.1 kg CO\({}_{2}\) eq.) [PERSON] et al. [39] reported the same trend, where CO\({}_{2}\) emissions depend on the cement composition, and also on the level of fineness of the components. Since the emissions associated to the cement clinker are significantly higher than for other materials, the modification of the binder composition results in a significant reduction of the GWP [39]. The EP, POCP, and AP were lower than the REF, in sequence, when mining residues were used to replace cement at 50% (less 23%, 34%, and 46%, respectively). The EP gives an overview on nutritional elements presence in aquatic systems, namely nitrogen and phosphorus. The excessive concentration of these compounds decreases the oxygen available in water bodies and, consequently, water quality. This results in increased primary productivity and phytoplankton proliferation, where some species may present toxic risks [40]. Mines are often reported as a source of nutrients, namely regarding nitrogen that is used in the concentrate process for pH regulating, acid washing, or lixiviuart agent [41]. In this way, significant decrease in EP is not expected, as it is foreseen in other environmental categories. The M50 mortar presented the lowest EP (2.03 \(\times\) 10\({}^{-2}\) kg PO\({}_{4}\)\({}^{3-}\) eq.). On the other hand, the various gases occurring by the hydration process of cement may release NH\({}_{4}\)\({}^{+}\) (ammonium) to the environment [42], contributing to the impacts observed in the EP for the REF (2.64 \(\times\) 10\({}^{-2}\) kg PO\({}_{4}\)\({}^{3-}\) eq.). Although EP is quantified in phosphates (PO\({}_{4}\)\({}^{3-}\)) equivalents, it is also possible to convert them in ammonia (NH\({}_{3}\)) equivalents, considering that 1 kg of NH\({}_{3}\) has the same EP of 0.35 kg PO\({}_{4}\)\({}^{3-}\)[43]. The POCP is a secondary air pollution, also known as smog. This effect is mainly caused by the reactions between sunlight and emissions from fossil fuel combustion, promoting the formation of other chemicals in the troposphere, as ozone and peroxides. This leads to an increase of the ground-level ozone concentration [44]. The POCP is mainly related to the technology involved in raw materials production. In particular, grinding contributes to approximately 50% of the energy consumed from cement production [39]. This may contribute to the higher emissions from REF (1.76 \(\times\) 10\({}^{-2}\) kg ethene eq.) that affect POCP, in comparison to M10, M25, and M50 mortars (an average of 1.42 \(\times\) 10\({}^{-2}\) kg ethene eq.) The AP is also affected by the combustion of fossil fuels, from industrial equipment, such as nitrous and sulfide oxides. In the presence of water and oxygen, these substances may leach and present risks for the surrounding ecosystems [45]. The presence of sulfide minerals in mining residues composition [5] may contribute to the AP detected at higher incorporation ratios of mining residues in mortars (M50 = 1.01 \(\times\) 10\({}^{-1}\) kg SO\({}_{2}\) eq.). However, the AP of using mining residues still have lower proportions than REF (1.87 \(\times\) 10\({}^{-1}\) kg SO\({}_{2}\) eq.). The emissions from the combustion processes of the kilns in a cement industry may release HCl and HF [46], with repercussions in the AP. Contrarily, mining residues demonstrated to have higher ODP (up to 2.5%) and, more significant, ADP (above 41%), in comparison to cement. The ODP is related to the ozone density decrease through the thinning of the stratospheric ozone layer, as a consequence of anthropogenic pollutants (e.g., halocarbons) [47]. Once more, the source of pollution associated to ODP is predominantly associated to the equipment involved in mining activities and cement production, being the differences between the two types of binders marginal (an average of approximately 3.0 \(\times\) 10\({}^{-7}\) kg CFC-11 eq. for all the mortars).