Etching new concrete is primarily done to prevent alkali from interfering with coatings. What is the substance?

Etching new concrete is primarily done to prevent alkali from interfering with coatings. What is the substance?

• A. Alkali
• B. Dust
• C. Moisture
• D. Oil

Answer: (A)

The substance is alkali. Fresh concrete contains a high-pH mix of alkaline compounds from cement, notably calcium hydroxide and other alkali salts. This alkaline surface can hinder coating adhesion and cause issues later on. Etching with acid helps remove the laitance and top contaminated layer, reducing surface alkalinity and leaving a cleaner, more porous profile for the coating to grip. Dust, moisture, and oil aren’t the primary target of the etching in this context, whereas the alkaline compounds in the concrete are what the process aims to address.

The substance is alkali. Fresh concrete contains a high-pH mix of alkaline compounds from cement, notably calcium hydroxide and other alkali salts. This alkaline surface can hinder coating adhesion and cause issues later on. Etching with acid helps remove the laitance and top contaminated layer, reducing surface alkalinity and leaving a cleaner, more porous profile for the coating to grip. Dust, moisture, and oil aren’t the primary target of the etching in this context, whereas the alkaline compounds in the concrete are what the process aims to address.