Thin Precast Elements

[Martino8]

We've recently been asked to provide structural calcs for precast concrete stair treads.
Most suppliers are providing 2.5" thick treads x up to 4 feet spans and 3" thick for spans above that.

ACI 318 Cover Requirements:
A. < #5 bar in precast elements exposed to earth or weather = 1.25 inch.
B. < #5 bar in precast elements not exposed to earth or weather = 5/8 inch.

I would assume that exterior stairs are expose to weather (even if they're in a covered breezway).
If that's the case, how can a 2.5 inch thick tread meet the concrete cover requirements?

 

[HTURKAK]

The stairs could receive tiling , non slip coating etc? and justify indoor conditions with someway?

Table 20.5.1.3.3—Specified concrete cover for precast-nonprestressed or prestressed concrete
members manufactured under plant conditions. Specifies clear cover for Slabs, joists, and
walls with No. 11 bar, W31 or D31 wire, and smaller = 5/8 in.



He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48