In Concrete composite, the fine particle size have a lots of advantages in both the mechanical and fresh properties. Hence the nano materials are the trending one in both cement concrete and geopolymer concrete. What could be the possible effect of these fine materials that give such advantages?
The small sizes of the fine aggregates ensure more rapid reaction with the other components in concrete, as reducing size of a matter increasing its reactivity. For example; nano-silica is more reactive than macro silica due to it size.
Also, the small size of these fine aggregates also equip them with the ability to act as fillers, micro fillers and nano fillers which further densify the micro and nano structure of the concrete thereby improving its overall strength and durability
Assuming you are referring to Portland cement concretes, in addition to the points by Adeyemi Adesina , small particle size precursors can also perform as nucleation centers for the condensation of hydration products. If the precursors are pozzolanic, these will consume Ca(OH)2 and speed up the formation of hydration products.
We have noted that nano particles of a geothermal silica can have a favorable and also detrimental effect depending on the curing conditions (long story).
Dear all,
I think that precursor is a term connected to geopolymer technology . I‘m agree with previous considerations about the use of Portland cement as binder , where pozzolana like micro or nano silica is very efficient .
Reducing size of precursors reactivity will be increased , but also related silicate demand. Final strength will be better ,using same amount per cubic meter , but this parameter is better visible when you use waste , like fly ash F type , that is usually quite weak, specially at room temperature.
The problem of geopolymer concrete is that its cost need to remain quite low to be comparable with Portland based concrete . Will be necessary take in account the cost of micronising of precursors and the increasing of silicate demand, with saving about total amount of binder (powder plus silicate) , that will be replaced by cheap aggregates.
Should be a great idea to produce good (with same properties or better than Portland based) geopolymer concrete using lower amount of reactive part and more aggregate . Stability will be more under control .
All the best
Alex Reggiani
Dear Shaswat,
You are right that nanoparticles are a hot trend in cement and concrete research. It's important to note that there have not been any applications of them in contstruction, outside of research.
Nanoparticles have a set of multi-scale effects in concrete. The most important mechanism appears to be the nucleation of the hydration of cement and secondary cementitious materials. Some nanoparticles (especially nano-SiO2 and clays) may be pozzolanic, but this does not appear to be a major mechanism when realistic quantities of these materials (no more than 1%) are used. On the bulk scale, workability is reduced, strength and other mechanical properties are generally increased, and durability properties are generally improved.
I've summarized these effects in Table 1 and Figure 5 of the attached paper.
Hope this helps!
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