What could be the possible applications of porous concrete from the aspect of structural application. What could be the feasible structural components? Porous concrete have very acknowledging pavement applications. But is it worth a try from structural aspect?
If compressive strength of concrete is suit for structural members, the concrete is normally sufficient. However, durability of the concrete is the main issue. The durability of the concrete decreases as porosity of the concrete increase. If the porous concrete can be produced in satisfactory mechanical properties and impermeability, it can be an alternative. However, all the needed propeties of the porous concrete will excessively increase the cost of the concrete in structural systems. So, i think it is not currently feasible.
As we know ,Porosity in concrete adversely affect the durability. As mentioned in the earlier answer permeability is of great importance which needs to be controlled so that reinforcement does not get corroded fast. However if it is done intentionally to save some cost then one can use some filler material having equivalent properties but no porosity can be allowed.
In structural application of porous concrete the main criteria is durability and permeability, but up to certain limit of porosity we can use it in structural application without affecting durability criteria.
Porous concrete was initially used in building walls when there was scarcity of cement during WW II. However, I am not sure whether they were load-bearing walls or just for partition. Porous concrete weighs more as functional concrete rather than structural one. if it is to be used in structural components other than pavement, higher porosity / permeability should be justified for the application. Structural members (Selected ones), that will be subjected to compression loads can be built with porous concrete, as compressive strength greater than 20 MPa can be attained. However, the permeability or porosity needs proper justification. In pavements, they are subjected to less intensity loads, that may not damage its structural integrity. However, they can be utilized in walls along with conventional walls to absorb noise , if its a issue. Even one can think of permeable blocks / bricks.
There has been some research that attempted to improve the durability and permeability of porous concrete by mixing it with some types of fibres (macro-synthetic), and some results were encouraging.
http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29MT.1943-5533.0001213
Well, the main issue of pervious concrete in the structural application is the durability because of the size of pore; we cannot use a reinforce bar because there is not a great quantity of concrete that help to avoid the corrosion of the reinforce. But, we can work with differents size of particles that help us to decrease the size of pore of the pervious concrete and obtain a concrete with excelent mechanical properties to be used in the structural field. You can read some papers where Alessandra Bonicelli talks about pervious concrete. Hoping that it will help you.
You could improve the porous concrete with addition of longer ECR glass fibers (Cem-fil) and you could improve the structural behavior with GFRP or CFRP bars, that have no react with the external moisture or water environments. However, your cost will be higher than a conventional concrete structure. We are working with porous media reinforced with glass fibers, self-compacted concretes of 45-55 MPa with good results, but the environmental conditions, the planet region and technological means play important role on the manufacturing of such material.
With concrete technology it always boils down to striking a fine balance between adequate structural performance-environment-economy. Adding fibres might well improve structural performance and lead to less cement use, but there is the cost that will become an issue. However, it is may be argued that it is worth paying extra to protect the environment.
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