# A Study on Reactive Ultra-Fine Fly Ash and Sulfoaluminate Cement in Self-Leveling Mortar
###### Abstract
The results showed that the addition of aluminate cement and SAC reduced the initial flow and 20 min flow of the mortar. When the aluminate cement content was 0-10%, the mortar's flexural strength and 1-day compressive strength significantly improved. However, when the content exceeded 10%, the strength noticeably decreased, even falling below that of cement mortar. Within the tested range, the flexural strength of the mortar increased with the SAC content, but the 1-day compressive strength showed little variation. When the content was 10-20%, both types of cement had a similar effect on the 28-day compressive strength of the mortar, enhancing it. [PERSON] [13] studied the potential use of phosphogypsum as a binder for calcium sulfate cement, calcium aluminate cement, and Portland cement in self-leveling mortar underlayment. Self-leveling mortar samples produced with phosphogypsum calcined at 550 \({}^{\circ}\)C for 4 h and 650 \({}^{\circ}\)C for 4 h showed the best performance in terms of strength. [PERSON] [14] found that the rheology of cement paste was related to the formation of ettringite, with the early formation of ettringite in Portland cement/SAC mixtures affecting the paste's rheological behavior. As the SAC content in the mixture increased, the rate of change in yield stress over time accelerated. The increased chemical reaction kinetics led to a faster structuring rate of the remaining cement paste, improving the workability of the mortar. [PERSON] [15] observed that adding SAC to Portland cement initially formed ettringite crystals, which acted as nuclei to promote hydration. The rapid consumption of free water and concentrated heat release also contributed to the development of early strength. [PERSON] [16] studied the reaction performance of self-leveling mortar mixed with alkali-activated cement containing fly ash and rice husk ash. Fly ash and rice husk ash (mixed in a 90%:10% ratio) were used to replace Portland cement in proportions of 25%, 50%, and 75%. The results showed that mortar containing 30% Portland cement achieved a compressive strength of 33.5 MPa and a flexural strength of 7.53 MPa. The best performance was observed when 10% Portland cement was replaced with the fly ash and rice husk ash mixture, which significantly reduced shrinkage and bending phenomena. In reference [17], blast furnace slag and fly ash were adopted to make self-leveling mortar. [PERSON] [18] explained that during the early curing stages, PUFA helps fill the voids in the microstructure of concrete and promotes the formation of ettrinigite. PUFA is also considered a composite material, with ash particles acting as reactive micro-aggregates. It was shown to improve the adhesion of concrete, increase compressive strength (both in the initial stage and in the long term), reduce drying shrinkage, and enhance durability. [PERSON] [18] also demonstrated that PUFA could enhance adhesion and promote pozzolanic reactions, forming C-S-H gel. This gel filled the pore structure, increasing the density and compressive strength of the specimens while reducing drying shrinkage. The addition of PUFA was also proven to lower chloride ion permeability and the non-steady-state migration coefficient, indicating improved workability and reduced permeability. PUFA was shown to outperform silica fume as a cement substitute in terms of adhesion, permeability, and construction performance. [PERSON] [19] found that mixing PUFA with cement mortar significantly improved performance and adding 45% PUFA in construction applications enhanced engineering quality. [PERSON] [20] noted that increased fineness of fly ash contributed to improved workability of the mix. Using PUFA to partially replace cement enhanced compressive strength. Regarding durability, replacing cement with PUFA positively affected resistivity, the chloride migration coefficient, and the alkali-silica reaction, though it had a negative impact on carbonation resistance.