It is a known fact that the Si/Al ratio of the cementitious matrix influences the behavior of the geopolymer concrete.
However, I would like to know about the effect of the Si/Al ratio of the cementitious matrix on the behavior/characteristics of a normal Portland cement concrete or high performance concrete made with supplementary cementitious materials.
-Also, is there any method to calculate the 'Si/Al ratio of the C-S-H' from the 'Si/Al ratio of the hardened concrete'?
If I am understanding your question correctly, then the question doesn't really have an answer. In geopolymer concrete, Si and Al oxides are extensively linked and therefore the Si/Al ratio has a significance in terms of the polymer structure. But in OPC products, the primary structural backbone is C-S-H, wherein SiO2 is the primary counter-cation to CaO and only a small fraction of Si sites are Al-substituted. Other phases not found in geopolymer concrete, notably ettringite and monosulphate, contain a large fraction of the Al.
In OPC chemistry, the Si/Al ratio reflects the ratio of alite and (to a lesser extent) belite to tricalcium aluminate and calcium aluminoferite. Since the alite and (to a lesser extent) belite are the binding phases that are primarily responsible for forming C-S-H and giving OPC products their mechanical and durability properties, increasing the Si/Al ratio will improve all important properties of the OPC. From a perspective of concrete properties, there is no drawback to increasing the Si/Al ratio and, in fact, an "optimal" OPC would have Al content of zero. However, it is not possible to manufacture such OPC for a number of reasons (e.g., raw material availability and the need to form liquid phases of C3A and C4AF in the cement kiln).
Hope this helps!
If I am understanding your question correctly, then the question doesn't really have an answer. In geopolymer concrete, Si and Al oxides are extensively linked and therefore the Si/Al ratio has a significance in terms of the polymer structure. But in OPC products, the primary structural backbone is C-S-H, wherein SiO2 is the primary counter-cation to CaO and only a small fraction of Si sites are Al-substituted. Other phases not found in geopolymer concrete, notably ettringite and monosulphate, contain a large fraction of the Al.
In OPC chemistry, the Si/Al ratio reflects the ratio of alite and (to a lesser extent) belite to tricalcium aluminate and calcium aluminoferite. Since the alite and (to a lesser extent) belite are the binding phases that are primarily responsible for forming C-S-H and giving OPC products their mechanical and durability properties, increasing the Si/Al ratio will improve all important properties of the OPC. From a perspective of concrete properties, there is no drawback to increasing the Si/Al ratio and, in fact, an "optimal" OPC would have Al content of zero. However, it is not possible to manufacture such OPC for a number of reasons (e.g., raw material availability and the need to form liquid phases of C3A and C4AF in the cement kiln).
Hope this helps!
Dear Lincy,
we made this kind of attempt for marble powder used as SCM. You may see here:
https://www.researchgate.net/publication/329231062_The_Effect_of_Curing_Conditions_on_the_Properties_of_Cement-Based_Composites_Blended_with_Waste_Marble_Dust
All the best
Łukasz
Thank you Professor. Sadowski, the article is really informative, and is apt to clear my query.
I think this article will help you a lot.
https://www.researchgate.net/publication/313172070_The_effect_of_alkali_and_sial_ratio_on_the_development_of_mechanical_properties_of_metakaolin-based_geopolymers
Hi Lincy,
Please refer the publication below that provides the methodology to calculate various phases in your supplementary cementitious materials.
"A quantitative study on the effect of nano SiO2, nano Al2O3and nano CaCO3 on the physicochemical properties of very high volume fly ash cement composite"
Regarding Si/Al ratio on using supplementary cementitious materials, just a word of caution, that fly ashes contain Si and Al in crystalline forms as well i.e. quartz and mullite, which don't react or take part in the pozzolanic reaction. So, your actual Si/Al ratio would be the component of the total Si and total Al that reacts and these forms are most often present in the amorphous phases. The publication above does provide a methodology to separate them. Feel free to contact me if you have any query
Y'all please don't post things on here that don't have to do with the question. It's not helpful for those of us why actually want to follow this discussion.
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