Why is it important to lower the heat of hydration in massive concrete structures?

Lowering the heat of hydration in massive concrete structures is crucial primarily to prevent thermal cracking. When concrete is placed in large volumes, the exothermic chemical reaction that occurs during hydration can lead to significant temperature rises within the concrete mass. If the temperature difference between the interior and the surface of the concrete becomes too great, it can create tensile stresses that exceed the concrete's strength, resulting in cracks.

Thermal cracking can compromise the structural integrity and durability of the concrete. Therefore, managing the heat of hydration—through methods such as using low-heat cement, incorporating pozzolanic materials, or implementing appropriate curing techniques—helps ensure that the thermal stresses remain within acceptable limits, thereby maintaining the quality and lifespan of the structure.

While the other options mention aspects like strength, workability, and aesthetics, they do not directly address the critical concern of managing thermal effects in massive pours, which is vital for preventing damage and ensuring long-term performance of the concrete.