Round Up Non-Selective Herbicide. If unwanted weeds and grass are taking over your driveway or patio, it's time for Roundup Weed & Grass Killer Super Concentrate. Intended for use in large affected areas, this 1L container delivers 51 L of ready-to-use product when mixed. Visible symptoms of control will occur within 3 days with complete kill in 2-4 weeks. Please check your local municipal bylaws for how to use this product safely.