There are many articles in the literature on ordinary portland cement concretes produced using recycled aggregates coated with pozzolanic slurries (cement + [fly ash, silica fume, micro/nano silica etc.]).
As you know, the quality of recycled aggregates is lower than natural aggregates. In some studies in the literature, the quality of the aggregates is improved by coating the surfaces of recycled aggregates by using slurries prepared with pozzolanic materials and cement.
My question is this: Suppose we have recycled aggregate soaked in slurry, dried and coated on the surface. Will the sodium hydroxide and sodium silicate, which we use in producing geopolymer concrete, damage or remove the coating on the surfaces of aggregates whose surface has been improved? Do you think this practice makes sense? If you were the supervisor of a thesis, a jury member or a reviewer of an article, what would you comment on this application?
I would be very happy if you share your valuable ideas with me.
Best Regards,
Interesting question. Research is open-ended. Good questions make for nice research directions. To answer your question you have to be more specific. What exactly is used to coat RCA? Then one can answer what is the behavior of such a coating in high alkaline environments. If it is a pozzolanic material, it usually tends to become more reactive in alkaline media, but should not be removed or dissolve as you seem to hint. The coating of RCA is often intended to mitigate excessive water absorption, shrinkage, and bond properties. You seem to be producing a geopolymer or alkali-activated material with RCA. Why don't you use an AAM slurry to coat the RCA?
Dear Dr. Nehdi,
Thank you for your answer. Actually, I was thinking about using AAM or GP slurry. However, it becomes more and more expensive. One side of me says it is a different research question and the other side says it is not something applicable for real life, industry.
I will make some trials and see what happens.
This is the realy good question and need need further elaboration and study of conditions! In general words the answer will be: the result will depend from the content of aggregate coating: the CAS phases will be destoing by alkaline, but at the same time, pozzolanic one - strengthening...
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering
- Coating