Concrete Sidewalk Investigations

SGH visited the sites to observe the extent of deterioration and based on our observations, we selected locations to collect core samples.

At our in-house laboratory, SGH conducted a petrographic examination of the extracted core samples. Highlights of our evaluation include the following:

• Microscopic examinations of the samples to identify constituents of the concrete mix, assess the condition of the hardened concrete, and make observations of the finishing technique
• Chloride ion content testing to evaluate the penetration of deicing salts
• Hardened air-void analyses on prepared (polished) sections to determine the overall air content and air void parameters and to opine on how these factors affect the concrete durability

The causes of deterioration varied for each location, but general causes included one or more of the following:

• Incorrect specifications
• Low overall entrained air content
• Finishing procedures, resulting in loss of near-surface air voids
• Trapped bleed water, leading to a weakened concrete surface
• Late season placement with insufficient curing
• Early exposure to deicing salts
• Inadequate resistance to cyclic freezing and thawing