Bostik Powermix Block A350Powermix Block A350 Flexible, fibre reinforced and specially modified high grade acrylic polymer that is mixed with Portland Cement to provide superior water protection and more to concrete surfaces. Uses: Once the primed surface is dry to the touch, prepare the Powermix cementitious mixture (1 gallon Powermix: 4. 5 kgs or 3. 5 liters Portland cement) to cover an area of 8sqm. Apply the mixture with a brush as the first coat over the measured area.