If water from an untested source is to be used for concrete manufacturing, what test must be made for strength?

If water from an untested source is used for concrete manufacturing a simple test can be done to know the strength of the concrete called Slump cone test.

Slump cone test:

This test is used to measure the consistency of the concrete. It is made with three percent increase in water added to the concrete will increase slump cone of about 1 in. A fresh concrete is made in proper proportions and the mixture is filled into the cone as three layers. Each layer should be tampered for 25 times using the tamping rod. For the first layer the rod should penetrate the whole length of the cone and for second and third layer the rod should tamp the specific layers. After tamping the level of the concrete will be reduced and the excess of mixture should be placed on it to fill the cone completely. After 2 seconds the outer cone cover should be removed and the height of the slump should be noted. Repeat this procedure with regular increase of water ratio. The difference in the slump height should be measured.