Mechanical Properties of Full-Scale Prestressed Concrete Beams with Thin Slab after Exposure to Actual Fire

Table 2

The appearance of test beam.

No.	The appearance of the floor (the floor is divided into 70 areas)
2#	The concrete was fumigated and blackened in partial areas without any other damage
3#	The color of the concrete remains unchanged. The sound of hammering in 6% of the concrete area is dull. 30% of the concrete area falls off with a characteristic depth of 2.1 cm, mostly locating at the end of the beam. And a small part of the beam-end steel strand is exposed, distributed from the fulcrum to quarter of the span
4#	6% of the concrete area is pink. Micro-crack and coarse-crack networks appear in partial areas. The sound of hammering in 76% of the concrete area is dull. 97% of the concrete area falls off with a characteristic depth of 2.6 cm. And the steel strands are exposed in some areas
5#	98% of the concrete area is pink or khaki. The sound of hammering in 96% of the concrete area is dull. 100% of the concrete area falls off with a characteristic depth of 3.6 cm. And steel strands in 25% of the concrete area have been exposed, which distributes from the fulcrum to a half of the span