## 2 Materials and Methods  
Three different mortars based on calcium sulphoaluminate were investigated as reported in Table 1 in accordance with a previous work [31]. In particular, a traditional mortar (hereafter referred to as TM) containing CSA clinker, Portland cement (OPC, according to EN 197-1) and technical grade anhydrite (CS) was produced. Additionally, two sustainable CSA-based mortars (hereafter referred to as SM 1 and SM 2, respectively) in which OPC is totally replaced by supplementary cementitious materials (SCMs, ground granulated blast furnace slag (GGBFS) according to EN 1516-7 and low calcium fly ash (FA) according to EN 450-1) and hydrated lime CL-90S class (CH, according to EN 459-1) were manufactured. Physical properties of the binders and the supplementary cementitious materials used are reported in Table 2. A set retarding admixture (0.8 wt.% mass of binder) based on tartaric acid (TA) was used to delay the initial set of mortars [26]. Lithium carbonate (LC) and sodium carbonate (SC) were also added to the mix as hardening accelerating admixtures up to 4% by binder mass in accordance with [32]. Finally, a natural siliceous sand with a maximum size equal to 2.5 mm was used (Figure 1). The water/binder ratio and binder/sand ratio were kept constant at 0.53 and 3.0, respectively. Figure 1: Granulometry of aggregates. The workability test by flow table described in EN 1015-3 was conducted on all the fresh mortars over time. In particular, the consistency was measured after the mixing procedure and the pot-life, corresponding to the time during which workability by flow table is higher than 140 mm, was also determined. Furthermore, fresh mortar specific mass and entrapped air were also measured in accordance with EN 1015-6 and EN 1015-7, respectively. The mixtures were molded into 40 mm \(\times\) 40 mm \(\times\) 160 mm specimens, demolded after 24 h and cured in a climatic chamber at 20 \({}^{\circ}\)C and 60% R.H. until tests (Table 3) in order to optimize the strength development in accordance with findings of [PERSON] et al. (2019) concerning the curing condition of CSA-based mixtures. Specific mass at hardened state, determined by weighing the specimen before mechanical test, and compressive strength were measured at 1, 7, 28, 120 and 150 days according to EN 1015-11 and drying shrinkage was evaluated in accordance with EN 12617-4 up to 150 days. Furthermore, dynamic modulus of elasticity (E\({}_{\text{d}}\)) was measured by means of Ultrasonic Digital Indicator Tester at 1, 7, 28, 120 and 150 days (EN 12504-4). Then, pore size distribution and density of the specimens were determined by means of mercury intrusion porosimetry (MIP) using Thermo Pascal 140 and 440. The MIP mortar samples (three specimens for each mortars) were dried in oven at 40 \({}^{\circ}\)C for 24 h and tested after 28 days from casting. Approximately 1 g of mortar was first intruded to a mercury pressure, P\({}_{\text{Hg}}\), of 395 kPa on the Pascal 140, then the sample was moved to the Pascal 440 and intruded to 200 MPa. Moreover, the depth of natural carbonation (specimens stored in air) was measured by a colorimetric test using phenolphthalein as pH indicator, according to EN 14630 up to 150 days. Finally, the capillary water absorption coefficient (AC) was estimated in accordance with EN 13057. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Composition** & **OPC** & **CSA** & **CS** & **CH** & **GGBFS** & **FA** \\ \hline D\({}_{50}\) [\(\mu\)m] & 5.19 & 8.18 & 2.93 & 3.00 & 5.48 & 11.1 \\ Specific surface [cm\({}^{2}\)/g] & 3175 & 2722 & 4837 & 4678 & 3049 & 2283 \\ Specific mass [kg/m\({}^{3}\)] & 3150 & 2650 & 2670 & 2120 & 2730 & 2010 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Physical properties of binders.