Originally Posted by
Florypb505
Sorry its taken so long to respond, I wanted to have the time to give a decent one.
When you do research in concrete the one thing to remember is that concrete is closer to baking then anything else. That's an oversimplification but the fact of the matter is that any published research in concrete is extremely hard to reproduce accurately, The materials available, humidity, and ability to mix a similarly homogeneous mixture all add to this situation. Now when your talking about organic material you add an additional level of complexity with an inability to reproduce the results. Relating it to just materials testing a more homogeneous material like steel have results that fall within a few percent of each other when using the same batch. On the other hand concrete material testing with a 10% variance in data is pretty common and that can be over one batch mix, and can spread even more when considering multiple batch mixes on different days.
I am the civil engineering director of laboratory research for NJIT, we have the biggest University concrete lab in NJ currently and most of the state's concrete research work comes through us. Alternatively Rutgers has the comprehensive asphalt lab and we sort of split the work coming from the DOT, Transit Authority, ACI North East, and some of the MTA work.
5 occasions we have done testing with organic material concrete fillers for some of the agencies partnered with companies promoting the said products. 2 of those have been exclusively hemp based. The first is fiber strand the second is granular, they were trying to reduce weight, add sound insulation, and fiber reinforcement to sound walls along the major highways using organic based concrete fillers. Avoiding the non disclosure information, the organic reinforcement is prone to rot in all cases besides resin coated as commented on before, termites also became a major concern for the non granulated organics specifically. As I stated earlier best case came from kiln firing the granular organics to produce charcoal, which semi acts as a pozzolan, but tends to reduce ductility more similar to a fly ash then a slag or silica fume based pozz. Cellulose based organic fillers also have the tendency to absorb water, because that is kind of what they do naturally, during the mix and after the setup if they are not sealed from the elements.
Addressing the lime comment, all general long kiln produced portland 1-4 have some lime in the mix, it is also added to any spec approved submerged curing baths, and hot tank curing. Steel reinforcement is typically in all concrete, and it wont rust until it gets exposed to air and water through micro cracks that develop into spalling or visible cracking, which is the main reason that all current state projects require epoxy coated reinforcement on new construction. The accelerated reinforcement rot in the environmental freeze thaw testing with organic fillers swayed my opinion to feel that there ability to absorb both air and water has lead to the accelerated rot I described.
Again results will vary especially with organics grown, leading to even less homogeneous concrete and work that cannot be replicated every time and will vary depending on the region it is being produced, mixed, and tested in. With that being said all of these types of concrete have a place but most of them are not usable everywhere, I stay weary of organic fillers in concrete in the north east just as I am weary of pervious concrete in anywhere that freezes. I could see organic fillers doing decent in desert style climates.
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