Fluid (Wet-Cast) Countertop Mixes vs. Stiff Countertop Mixes | Concrete Decor
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Fluid (Wet-Cast) Countertop Mixes vs. Stiff Countertop Mixes

Are you new to countertops? Are you confused about what the term "wet-cast" means? Here's a look at fluid concrete mixes for wet-casting as compared to stiff mixes for hand-packing, which is also known as "the Buddy Rhodes method."

Stiff Mix
A stiff concrete mix is characterized by its zero-slump, stiff plastic state. The fresh concrete is easy to mold. It typically uses an all-sand mix design.A stiff concrete mix is characterized by its zero-slump, stiff plastic state. The fresh concrete is easy to mold. It typically uses an all-sand mix design.

Pros

  • Almost all styles of concrete are possible: uniform, terrazzo, veined, etc.
  • Forms do not need to be watertight. Caulking is not necessary.
  • Complex shapes using simple forms are possible.
  • Reinforcing steel stays where it is put.
  • Ghosting is significantly reduced or eliminated.
  • Final product is very natural in appearance.
  • Can control surface void shape and size.
  • A wide range of stiffness and plasticity is possible.
  • Screeding and troweling can be performed soon after casting.
  • No bleed water.
  • Casting tables do not need to be perfectly level.
  • Stiff mix can be placed in thin lifts, and form "buttering" is possible. Face buttering reduces expensive pigment and aggregate costs.

Cons

  • Casting takes longer.
  • Achieving fine detail, crisp edges, etc., requires more care and skill.
  • Requires a paddle-type mortar/plaster mixer for proper and adequate mixing.
  • Cast surface always has some voids and pinholes.
  • Improper compaction can result in more voids and weaker concrete.
  • All-sand mix requires more cement to achieve good workability.
  • Mix consistency is sensitive to superplasticizer and water contents.

Fluid (Wet-Cast) Mix
A fluid concrete mix for wet-casting is characterized by high slump and high fluidity.A fluid concrete mix for wet-casting is characterized by high slump and high fluidity. It typically uses graded aggregates with sizes ranging from sand to gravel. High-slump concrete is very flowable concrete when vibrated. It uses powerful superplasticizers and viscosity stabilizers to achieve large spread with no particle separation.

Pros

  • Casting is quick.
  • Little skill is required for casting.
  • Mixer may be rotary drum or paddle type.
  • Material is easy to level.
  • Fine detail is easy to capture.
  • Vibrating significantly reduces air voids at the surface.
  • It's possible to achieve a very smooth and uniform as-cast finish.
  • Reinforcing steel is easily coated and encapsulated.
  • Can reduce cement content to maintain slump through careful aggregate grading.

Cons

  • Requires watertight forms. Caulking is necessary.
  • Requires level casting tables.
  • May require a vibrating table if a zero-pinhole surface is required.
  • Potential for bleed water and separation with improper mix.
  • Mixture is often sticky and difficult to trowel (once it starts to set up).
  • Cannot achieve variegation.
  • Higher risk of shadowing or ghosting.
  • Reinforcing steel can sink.
  • Front-edge returns or 3-D casting requires complex forms.
  • The surface must be processed with great care if aggregate is not supposed to be visible.
  • Material cannot easily be placed in thin lifts. The high slump prevents buttering. This increases the cost when expensive pigments and aggregates are used.
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