Sweeping or vacuuming loose dirt and debris is the most straightforward approach to cleaning concrete walls. Next, mix warm water with a mild detergent to make a cleaning solution. Scrub the walls carefully with a mop or a brush with soft bristles. Pay close attention to any tough stains or blemishes. You can use a solution of equal parts water and white vinegar for stubborn stains. Rinse the walls with fresh water and remove any extra detergent or vinegar with a sponge or towel. The walls will seem clean and revitalized if you let them air dry.