Which method is characterized by placing prestressing material before concrete pouring?

The method characterized by placing prestressing material before concrete pouring is known as pretensioning. In this process, high-strength steel strands or cables are stretched and anchored to a casting bed prior to pouring the concrete. Once the concrete has cured and gained sufficient strength, the tension is released, allowing the strands to compress the concrete. This pre-compression enhances the concrete's ability to withstand tensile stresses that occur in service, effectively improving its structural performance.

Pretensioning is commonly used in precast concrete elements such as beams, slabs, and other structural components, where the controlled environment of a manufacturing facility allows for better quality control during the curing process. This method is advantageous as it allows for longer spans and reduced structural depth compared to conventional reinforced concrete.

Other methods, such as posttensioning, involve the placement of steel tendons after the concrete has set, which differs fundamentally from pretensioning. Finishing and consolidation are processes related to surface treatment and compaction of concrete but do not involve the prestressing process.