Complex sentence: Before cement-based mortar, lime-based one was used which does not present an alkaline environment; therefore, majority buildings with wall tie corrosion are built before World War II. An alkaline degree gets weaken while exposed at acidic rain over the time.
Split into simpler sentences: Before cement-based mortar, lime-based one was used which does not present an alkaline environment; therefore, majority buildings with wall tie corrosion are built before WW2. An alkalince degree gets weaken while exposed at acidic rain over the time.