*2.2. Preparation of Mortars and Pastes*

Mortars and pastes differing in their composition with the type of binder, amount, and viscosity of HEMC admixture were prepared for the tests. As a reference material, a cement mortar without admixture, designated as C-0, was used. In addition, cement composites modified with admixture in various amounts and viscosity (with symbols C-0.05-MV, C-0.3-MV, and C-0.175-HV) and composites

modified with cellulose ether, in which cement was replaced with 50% hydrated lime (marked with symbols CL-0.05-MV, CL-0.3-MV, and CL-0.175-HV). The MV symbol stands for Medium Viscosity (cellulose ether with a viscosity of 25,000 mPa·s), whereas the HV symbol stands for High Viscosity (cellulose ether with viscosity of 45,000 mPa·s). The admixture was added in the amount of 0.05%, 0.175%, and 0.3% in the relation to the dry ingredients of the mortar (binder and fine aggregate). The detailed composition of mortars is given in Table 3. The article is a part of a wider study concerning the analyzed issue in which the influence of cellulose ethers and hydrated lime on selected properties of plastering mortars was studied [31]. Some research in this direction has been published in articles [14,15,30]. The composition of pastes was similar to the composition of mortars, excluding fine aggregate.



Cement, hydrated lime, and fine aggregate were weighed with an accuracy of 0.1 g, and the chemical admixture was weighed with an accuracy of 0.0001 g. The ingredient mixing procedure was as follows: 90 seconds of mechanical mixing at 45 rpm, 30 s of rest, and 90 s of mechanical mixing at 57 rpm. The time and method of mixing were constant (the same in each case).

All mortars were performed, maintaining a constant weight ratio of the binder to the fine aggregate of 1:10. The amount of water was chosen so as to obtain a constant consistency of 165 mm, measured using a flow table, according to the PN-EN 1015-3:2000 standard [32]. All samples were prepared and tested in an air-conditioned laboratory at a temperature of 20 ± 2 ◦C and a relative air humidity of 65 ± 5%.
