The stoichiometric water level is very low (stoichiomteric water / cement ratio ranges from 0.2 to 0.25 depending on the type of cement). Therefore, using this amount of water will result in a concrete mix with very low workability. However, any amount of water that causes W/C ratio to be higher than the stoichiometric ratio, will not react with cement, and will evaporate with time. This will increase the porosity of concrete and decrease the compressive strength.

As known, the ratio is very low. Hence, designing the concrete mix using SW/C ratio will lead to almost dry concrete mix, though it may lead to the presence of exact amount water which is necessary for hydration. Therefore, in view of attainment of proper workability and strength eventually, it is not advisable to use SW/C ration for concrete mix design.

Dear Waldemar Łasica

In addition to Amr Ibrahim and Sulaem Musaddiq Laskar comments with regard to the low workability for the stoichiometric water level, this low water level is also expected to produce autogenous shrinkage hence jeopardizing the long term performance of the mix, unless other measures are taken in to consedration when using such low w/c mixes.

Best wishes