What is the maximum W/C ratio in cement mortar?
I have make mix of mortar with ordinary Portland cement and standard sand, according ASTM C109 the mix ratio of cement: sand : water was (1:2.75:0.485) but the flow value was very low (about 24%) where it should be 110+-5, so I have increase the water cement ratio to 0.7 to get flow of 108, is it ok?
what if I use W/C of 0.485 and using superplasticizer to increase the flow value?
You can use superplasticizer anytime to improve the flow of mortar/concrete mix. Increasing the W/C for consistency will change a lot of factors (porosity, hydration kinetics, setting time) in your research. The question is not sufficient to guess the reason for low consistency of the mortar mix with W/C of 0.485 and 0.7.
Generally for OPC type 1 the W/C ratio of 0.5 (without any additives or SCM) gives you desired flow. However the flow of mortar decreases significantly with the use of SCM such as fly ash, clays or calcined clays. Using polycarboxylate based superplasticizer with clays is not a good idea.
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