# A Study on Reactive Ultra-Fine Fly Ash and Sulfoaluminate Cement in Self-Leveling Mortar
## 2 Materials and Methods
### Mix Design and Curing Conditions  
In this study, a fixed water-to-cement ratio of 0.60 was used. The reasons for selecting this value are explained in the following: (1) In order to increase the pot life of mortar, usually, a retarder is used; in this study, no retarder was used to avoid complexity, since once a retarder is used, the consistency of the chemical admixtures as well as mineral mixtures should be considered. (2) Without using a superplasticizer, the trial mixture with Portland cement alone (S0F0) with a ratio of binder material to fine aggregate of 1:2.75 was designed according to ASTM C109 [25] to make the self-leveling mortar satisfy the requirements of ASTM C1780 [26]. However, this mixture failed. Increasing the water-to-cement ratio to make the mortar satisfy the requirements of ASTM C1780 would result in unacceptable compressive strength loss. Therefore, the water-to-cement ratio was fixed at 0.6 to keep the compressive strength at an acceptable level and satisfy the requirements of ASTM C1780 with the use of chemical additives and mineral additives.  
In this study, the addition of SAC and PUFA was implemented. Based on the mix proportions for the trial mix (S0F0), SAC and PUFA in different volume percentages of total cementitious materials were used. This means that for all mixtures, the volume of total cementitious materials remained the same. By doing so, the ratio of binder material to fine aggregate was no longer 1:2.75. The details of the raw materials for all mixtures are tabulated in Table 3.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Group**} & \multirow{2}{*}{**Water**} & **Type I Portland** & \multirow{2}{*}{**RUFA**} & \multirow{2}{*}{**SAC**} & **Fine Granular** & **Carboxylic** \\  & & **Cement** & & & **Material** & **Acid** \\ \hline S0F0 & 296.4 & 494.1 & 0 & 0 & 1358.8 & 0 \\ \hline S0F5 & 292.0 & 469.4 & 17.3 & 0.0 & 1358.8 & 1.22 \\ \hline S0F10 & 287.5 & 444  
The dosage of polycarboxylate-based superplasticizer was determined based on the self-leveling mortar flowability test requirements of ASTM C1780 [26], with a flow range of 120 mm to 150 mm. The SAC volume percentages of total cementitious materials were 0%, 10%, 20%, and 30%, and those of PUFA were 5%, 10%, and 15% to replace the cement in the mix. The amount of superplasticizer was adjusted to achieve the required flow, with the dosages of polycarboxylate-based superplasticizer being 0.25%, 0.30%, and 0.40% of the total binder weight.  
The mixing procedure followed the requirements of ASTM C1780 [26]. The first step involved adding the appropriate mixing water and superplasticizer into a separate container and mixing them for 65 s, observing the mixing state. The second step began with the mixing pot being set to an initial 30 s period (0-30 s) at a medium speed of 281 rpm. During this time, fine aggregate, Type I Portland cement, PUFA, and SAC were added to the mixing pot. In the next 30 s (30-60 s), the prepared solution was added to the mixing pot for combining it with the binder materials. At the 60 s mark, the mixer was stopped, and the mortar that had accumulated in the corners of the mixing pot was scraped back into the mix. This process continued with the timer running from 60 to 90 s, ensuring the mixing steps were completed within 30 s. Following this, the mixture was blended at high speed (580 rpm) for 240 s (from 90 to 330 s on the timer). In total, the entire mixing process took approximately 5 min and 30 s.