Complex sentence: Lime would have been used locally to improve the heavy, clay-rich Wealden soil, in the mixing of mortar for construction, and was also used in Sussex for plasterwork and'white washing'.
Split into simpler sentences: Lime would have been used locally for agricultural improvements (to improve the heavy, clay-rich Wealden soil) in the mixing of mortar for construction. Also used in Sussex for plasterwork and'white washing'.