Which of the following would cause crazing (superficial cracking) on the surface of concrete?

• A. Early drying due to late curing or excessive water on surface
• B. Excessive cement content
• C. Rapid cooling after curing
• D. High humidity conditions

Answer: (A)

Crazing, which refers to the formation of small, shallow cracks on the surface of concrete, is primarily caused by early drying of the concrete before it has had a chance to cure properly. When there is late curing or if excessive water remains on the surface, the evaporation of water can occur rapidly. This rapid loss of moisture can lead to a differential shrinkage between the surface and the underlying concrete, resulting in the development of superficial cracks.

The other options do not directly lead to crazing in the same manner. While excessive cement content can affect the overall properties of concrete and might lead to other issues such as shrinkage cracking or increased heat generation during curing, it is not the primary cause of crazing. Rapid cooling after curing could impact the concrete's structure but is less directly linked to surface cracking than the moisture-related issues. High humidity conditions, conversely, generally help reduce the risk of crazing by slowing down the evaporation of water from the concrete surface. Thus, controlling the moisture levels during the curing process is vital to preventing crazing, making the first choice the correct answer.