Can bamboo be used instead of steel in concrete?
Organic building materials have been used for construction in the old times and have proved to be an apt choice. Bamboo has been used as the skeleton of the structure for a long time, later replaced by steel rebars . They are still used in some rural parts in India and Africa for making small mud-huts. Given their remarkable strength when dried, bamboo stems can be used as reinforcement in small buildings.
The problem arises with the seismic zone of the construction site. No doubt steel has much more plasticity than bamboo and thus can bear seismic forces  without leaving any impact on the building. Also, since bamboo is organic, it does not have a long life in comparison to steel reinforcement. This gets worse in areas near water bodies, especially seas and oceans which have highly corrosive water and salts that can corrode bamboo in very less time.
Since earthquakes, droughts and floods are becoming more common with the passing years as a sign of global warming, it is advisable to prefer steel reinforcement for construction. For instance, TATA Tiscon’s SD  (higher grade than Fe 415 and Fe 500) is an appreciated option since it can bear earthquakes to a bigger level, sustains underground sea water, and holds the building stronger and longer. Bamboo is definitely cheaper but not a long-lasting option for construction.