We're building a floor that calls for a white dry-shake to make it light-reflective. The specs also call for a hard troweled finish. We're concerned about burning the white surface. Is a stainless steel or plastic trowel better than an ordinary steel trowel? What else can we do to prevent burn marks?
Trowel burns are caused by hard-troweling a surface so stiff that the trowel angle can be very high without causing chatter marks. Tilting the trowel increases pressure on the trowel edge and this densifies concrete at the surface. Darker concrete in the burned areas is simply concrete with a higher density and lower water-cement ratio. According to Bob Gulyas of Master Builders, using a stainless steel trowel will prevent rust stains that could occur if you used an ordinary steel trowel. But it's still possible to burn a surface with stainless steel trowel blades if pressure on the blade is high enough. We're not sure about the effect of using plastic trowels. Plastic is a softer material than steel and perhaps wouldn't have as great a tendency to burn a white surface. Have any of our contractor readers been able to hard-trowel a white floor with plastic trowel blades and avoid burning the surface? Let us know about your experience.