What characterizes pre-stressed concrete?

Pre-stressed concrete is characterized by the method it employs to enhance its strength and durability. This involves the use of tensioned steel rods or cables that are placed within the concrete before it is exposed to the loads it will eventually bear. The process creates internal compressive stresses, which counteract the tensile stresses that occur when the structure is in use. This pre-compression allows the concrete to withstand greater loads and reduces the likelihood of cracking.

The other options relate to different characteristics of concrete but do not accurately define pre-stressed concrete. Lightweight aggregate pertains to a different type of concrete used primarily for reducing weight, thicker concrete refers to variations in design or load-bearing characteristics, and reinforcement with plastic is not a method typically associated with enhancing the strength of concrete. Therefore, the defining feature of pre-stressed concrete is its incorporation of tensioned steel rods, which is fundamental to its structural integrity and performance.