Should cement and aggregates be measured by weight or by volume?

Measurement of constituents for concrete is normally carried out by weight because of the following reasons :

(i) Air is trapped inside cement while water may be present in aggregates. As such measurement by volume requires the consideration of the bulking effect by air and water.

(ii) The accuracy of measurement of cement and aggregates by weight is higher when compared with measurement by volume when the weighing machine is properly calibrated and maintained. This reduces the potential of deviation in material quantity with higher accuracy in measurement for the design mix and leads to more economical design without the wastage of excess materials.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.