Valorisation des brasques traitées utilisées dans la production de matériaux de construction et miniers

Abstract

The use of treated spent pot lining in the manufacture of construction materials has aroused the curiosity of scientific researchers and industrial engineers in order to know its environmental impacts and its potential roles, with respect to its physical-mechanical properties. The main objective is to evaluate the potential of valorization of treated spent pot lining its use in the production of concrete and mining backfill. This work consists in performing life cycle analyses or LCA and laboratory tests with percentages ranging from 5 to 15% of treated spent pot lining as a cement additive in concrete and mining backfill. Using the Ecoinvent database and OpenLCA software according to ISO 14040 and 14044, LCA studies are performed with the ReCiPe H method. Laboratory tests are carried out with the addition of treated spent pot lining in the recipes of the concrete and paste backfill from the LaRonde mine. Other binders such as blast furnace slag and fly ash are used to compare results. The LCA results show that cement is the material that contributes most to the impacts and also has a remarkably high carbon footprint due to the calcination phase of its raw materials at 1450oC to manufacture clinker. Transportation by truck is the second largest contributor to greenhouse gases. Water and plasticizer are elements that generate very little impact. Gravel and sand have high contributions to natural land transformation and average emissions at the different levels of the other selected categories. The carbon footprints of LCLL Ash (Low Caustic Leaching and Liming Ash) and calcined LCLL Ash are medium to low, so their use represents a promising and interesting solution to reduce the environmental impacts of concrete production. The results of the sensitivity analyses based on calcination show a minor difference between the found values of the impacts. The use of calcined LCLL Ash considered as a clay calcined at 800, 1000 and 1450°C is a promising technique to counter the depletion of natural resources for construction materials and is also an effective way to reduce CO2 emissions related to the use of cement in concrete production. As for the sensitivity analysis on transportation, the impacts generated when fly ash is transported by truck to make concrete show values that are much closer to that of fly ash transported by ship from Italy, although the distance to bring fly ash from Italy is large (7563.39 km). The sensitivity analysis based on calcination shows littles variations between impacts. This minor difference between values is influenced by the choice of assumptions considering calcination parameters (type of calcination, type of kiln, type of calcination fuel). The results of the air content measurements show that the manufactured concretes have contents with values between 2.51 and 3.70%. These results are lower than the air content of a fresh concrete which is generally between 5 and 8%. The measured temperatures are between 19.6 and 21°C and are values within the temperature range of fresh concrete (i.e., 10 to 25°C). The results of the strength measurements show that the addition of LCLL Ash to the recipe results in a decrease in compressive strength compared to the backfill made with blast furnace slag and an increase in strength compared to the concrete made with 100%GU. The use of blast furnace slag in the backfill has a better compressive strength than the use of LCLL Ash. As for concrete made with LCLL Ash, their compressive strengths are somewhat more similar to concrete made with fly ash with a minor difference. LCLL Ash maintains the compressive strength of concrete at different ages (7 d, 28 d, and 90 d) and its use is promising in concrete production as a supplementary cementing material.

Date	16 Aug 2023
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Claudiane Ouellet-Plamondon (Supervisor)