Abstract
The resistance of alkaline‐activated silico‐manganese fume (SMF) and blast furnace slag (BSF)‐based mortar, prepared by varying BFS and NaOHaq composition, during 20 weeks of exposure to 5% sulfuric acid (H2SO4aq) of initial pH = 0.24 and pure water (controlled) was studied. The deterioration was monitored by visual, alkalinity, mass, compressive strength and microstructural tests. The set of specimens synthesized included: (a) BFS‐free high alkaline, (b) SMF‐BFS blended high alkaline, and (c) SMF‐BFS blended mild alkaline system. Their residual strengths after 20 weeks of acid exposure were 20.1, 18.6, and 16%, respectively. BFS‐free specimens exhibited high resistance to acid attack due to the dearth of Ca in SMF. BFS‐admixed mild alkali system resulted formation of more gypsum and dealumination attributed to incomplete dissolution of Ca grains leading to severe spalling. BFS‐admixed high alkaline system underwent moderate resistance due to dense microstructure formed by additional C‐S‐H, K‐A‐S‐H, and C‐Mn‐H gel which enhanced retention of the polymerized framework.