What is the defining characteristic of post-tensioned concrete?

The defining characteristic of post-tensioned concrete lies in its construction method, specifically the use of tensioned steel tendons or bars. In this technique, high-strength steel tendons are placed within ducts in the concrete slab. After the concrete has cured to a certain strength, these tendons are tensioned and anchored against the concrete. This process imparts compressive stresses to the concrete elements, which counteract the tensile stresses that arise from loads and environmental factors, thereby increasing the concrete's overall strength and durability.

This method is particularly advantageous in reducing cracking and deflection while allowing for longer spans and thinner slabs compared to traditional reinforced concrete. The other options do not accurately define this construction method; for instance, insulating with wood or the inclusion of quick-drying additives do not relate to the principles of post-tensioning, nor do they encompass the distinctive function of tensioning steel tendons. Thus, the characteristics attributed to post-tensioned concrete center on its unique tensioning method which enhances structural performance.