ACI Color & Texture Finishing 2

Question 1

When using dry-shake color hardener on a concrete slab, at what stage should the first application be made?

Accepted Answer

After bleed water has evaporated and the surface can support foot traffic

Answer

Dry-shake hardener is applied after bleed water evaporates and the surface can just support a worker's weight without sinking more than about 1/4 inch.

Question 2

Which chemical compound is primarily responsible for the color produced by integral iron oxide pigments in concrete?

Accepted Answer

Iron oxide (Fe2O3 or Fe3O4)

Answer

Iron oxide pigments in red, yellow, brown, and black shades are the most common and stable colorants used in integrally colored concrete.

Question 3

A contractor notices that a stamped concrete patio has 'ghosting' — faint impressions from the stamp that appear lighter than the surrounding surface. What is the most likely cause?

Accepted Answer

Stamping performed too early while bleed water was present

Answer

Stamping while bleed water is still present traps water under the stamp, creating lighter, weaker areas called ghosting.

Question 4

What is the purpose of a 'release agent' when stamping concrete?

Accepted Answer

To prevent the stamp from bonding to the concrete and add a secondary color accent

Answer

Release agents serve a dual purpose: they prevent stamps from sticking to the surface and add a contrasting antiquing color that highlights pattern details.

Question 5

A concrete finisher is applying an acid stain to a cured slab. Which safety precaution is MOST critical?

Accepted Answer

Using respiratory protection and chemical-resistant gloves and eye protection

Answer

Acid stains contain hydrochloric acid and metallic salts that can cause severe burns to skin and eyes and emit harmful fumes requiring respiratory protection.

(ACI) American Concrete Institute Concrete Finisher Practice Test

(ACI) American Concrete Institute Concrete Finisher Practice Test

ACI Color & Texture Finishing 2