The incorporation of EipponCell® HEMC LH 620M Cellulose ether into mortar results in a dual functionality of water retention and thickening. Even at a minimal dosage of 0.2%, it significantly mitigates delamination issues in plastering mortar intended for air-entrained concrete, concurrently enhancing the overall water retention capability of the mortar, thus exhibiting remarkable efficacy in this aspect. Furthermore, HEMC exhibits an inherent air-entraining effect, leading to improved workability of the mortar. Notably, it also contributes to a substantial reduction in the dry density of the mortar, and this effect becomes more pronounced with higher HEMC concentrations. Upon the addition of HEMC to the mortar mix, a marginal reduction in flexural strength is observed, while there is a more pronounced decrease in compressive strength. The bending ratio curve exhibits an upward trajectory, indicating that HEMC supplementation enhances the toughness of the mortar. A particularly noteworthy attribute of HEMC is its impressive water retention capacity. This property acts as a barrier against rapid water absorption by air-entrained concrete in plastering mortar scenarios. Consequently, it ensures comprehensive hydration of cement within the mortar, resulting in a denser combination of mortar and air-entrained concrete, thereby elevating bond strength to higher levels.