Steel reinforcement rod is added to concrete because it has low tensile strength and when used in a span, the bottom-half of the 'beam' is in tension. I think bamboo would work fine for this application the day you put it in, but as it dries, rots and shrinks, you'll lose the tensile strength of the bamboo and the bond between it and the concrete without any visible change to the roof. Soon you'd have a very weak roof and it will still look the same. Also, because the concrete would trap the moisture around the bamboo, it would likely rot more quickly than if it was in open air.

The same results could be expected with any wood reinforcement. When mixing concrete, it's important to avoid any organic matter mixing in, because of this and also because it will produce gas while it's rotting that can swell and damage the concret.

Yes, re-bar will sometimes rust with the same catastrophic results, but it takes decades and an avenue for water entry. Where-as I see the bamboo lasting five or ten years at most. Better to just have a bamboo roof that you can replace when you see that it's gone bad.

As for the homeless, I figure they're mostly mental patients and druggies here in the US. They often like being homeless. Not the same worldwide.

I have seen Bamboo reinforced concrete last for 20 - 25 yearsin the Coastal areas of South India. It defies all logic.I have not gone in depth about the way the treat the bamboos.They could have used neem oil to treat the bamboos. Steelreinforced concrete is not very popular in these areas, wherethe steel rusts and becomes fragile.

Yes, I've read about it a little since and it seems that it is used often and with success. they only use bamboo that has been cut for more than three years and usually dip it in asphalt tar or latex to protect it from the moisture of the concrete as much as possible.

But if this is already common, I don't see that it makes more sense for homeless than other technologies.

When I first saw this concept being implemented, I was reallyamazed to see bamboo used to reinforce concrete. I have seensmall houses being constructed only out of bamboo reinforced concrete.A dedicated research into this concept should be highly beneficialfor low cost housing projects. I feel if the bamboos aretreated and enclosed in a small steel mesh - It would be structurallymore sturdy and long lasting.