Concrete Patio slabs Clean Part 1: Acid Wash - YouTube
Bostik Professional Patio cleaner, 5L Jerry can | DIY at B&Q
High Strength Brick Acid A super strength (18% hydrochloric acid) cleaner that will remove cement and mortar splashes from brickwork, paving, concrete floors and warehouses.
Larsen Patio & Brick Cleaner 1Litre XD - Goodwins
Brick & Patio Cleaner A powerful acid based cleaner