This paper aims to investigate the workability of Limestone Calcined Clay Cement (LC3) concrete by rheometry which is a more reliable technique than conventional tests like slump test, etc. It is a well-known fact that the concrete made with LC3 is stiffer and has lower workability due to higher water demand, in comparison to other cements. Here the rheological properties of LC3 concrete are studied and then compared with the conventional Ordinary Portland Cement (OPC) concrete by using a concrete rheometer. An attritor-type impeller was attached to the central axis of the rheometer to simulate the mixing conditions present in concrete mixer. A total of five concrete mixes were designed at a constant water-cement ratio of 0.50: three of which were made with OPC and two with LC3. In OPC mixes, cement content and coarse aggregate-to-total aggregate ratio were varied from the control mix. While in LC3 mixes, two types of clays with different kaolinite content were selected to understand their effect on workability. The energy required for mixing the concrete is qualitatively analysed by measuring the torque at various rotation speeds for both OPC and LC3 concretes in presence of admixture. In OPC concrete, with increase in the fines, the concrete becomes stiffer and thus higher torque values were observed. In LC3 concrete higher torque values were observed when high kaolinitic clay was used. In practice, LC3 concrete requires more effort for mixing as compared to OPC. However, the torques values obtained for LC3 concrete was lower due to higher dosage of admixtures.