What is typically true about the early age strength of concrete cured at temperatures above 80°F?

Curing concrete is a delicate balance that involves various factors, including temperature. When concrete is cured at temperatures above 80°F, it tends to experience a faster rate of hydration initially due to the increased kinetic energy available in warmer conditions. This might suggest that early strength could be higher. However, while this rapid hydration can produce some early strength gains, it can also lead to issues such as increased evaporation rates, a higher likelihood of plastic shrinkage cracking, and ultimately less stability over time.

At high temperatures, the concrete can also experience a phenomenon known as thermal cracking and can lose moisture quickly, leading to a reduction in effective hydration. Therefore, it is not unusual to find that the overall early age strength could be compromised compared to concrete cured under more moderate temperatures, which allow for a more controlled hydration process and help maintain appropriate moisture levels.

As temperatures increase beyond the optimal curing range, the negative effects often outweigh the benefits of any initial strength gains, causing the early age strength of concrete to be lower than that cured at moderate temperatures. This understanding is crucial for concrete inspectors to ensure the longevity and durability of concrete structures.