There is a clear relationship between water ratio and mechanical properties. The water is our carrier. Polycondensation happens between compounds that are soluble in water. It is the water content which determines the density of the matrix. After polycondensation, the excess of water which is not tied to the structure in the form of -OH is expelled from the tri-dimensional network.
After drying has occurred, the volume occupied by the water molecules is empty. This results in a matrix full of micro-voids. I guess you understand that strength is directly correlated with the voids content. Yet this property is also very interesting in terms of freeze-thaw properties and thermal shock. Microvoids and microchannels are very useful to prevent any damage caused by absorbed freezing water.
However, to manufacture fiber reinforced composites, the impregnation of fibers requires very low viscosity. We achieve this very low viscosity by decreasing the ration 1:12 to 1:15 or 1:20.
But because we still want to achieve high mechanical strength, the impregnated fabric is vacuumed at ambient temperature, to evaporate the excess of water.
The US patent you are referring to is dealing with the method of production of M-PSDS geopolymer. If you go back to the earlier patents which dealt with the processing of M-PS or M-PSS geopolymer, you will learn that geopolymerisation occurs even with concentrations of solids that are lower than 60%.
Prof. Joseph Davidovits
