# A Study on Reactive Ultra-Fine Fly Ash and Sulfoaluminate Cement in Self-Leveling Mortar
###### Abstract  
The purpose of this study is to find appropriate mixtures for self-leveling mortar that meet the fluidity requirements without displaying segregation by using a combination of two types of cement (Type I Portland cement and sulfoaluminate cement (SAC)) with reactive ultra-fine fly ash (RUFA). Unlike the fly ash, RUFA has a strong strength activity index and exhibits a significant pattern of amorphous phase in XRD. Appropriate mix proportions of raw materials, including the superplasticizer, require investigation in depth. A fixed water-to-binder ratio of 0.6 was selected, with varying proportions of the two cementitious materials considered (the SAC volume percentages were 0%, 10%, 20%, and 30%) and different RUFA contents (the RUFA volume percentages were 5%, 10%, and 15%). Twelve experiments were conducted to examine the properties of the self-leveling mortars. We found that a higher RUFA volume percentage results in lower porosity, higher compressive strength, and better resistance to drying shrinkage, abrasion, and restrained shrinkage cracking. Increasing the SAC volume percentage increases the porosity of self-leveling mortar and its early compressive strength but decreases late-stage strength. At a 10% volume percentage level, SAC achieves an ideal balance among drying shrinkage, abrasion, and shrinkage cracking. use, with experimental data closely resembling those of pure cement-based self-leveling mortar. [PERSON] [5] studied the effects of different types of re-dispersible latex powder on cement-based self-leveling mortar. The findings indicated that re-dispersible latex powder significantly improved the flowability, adhesion, and wear resistance of the mortar without adversely affecting its compressive and flexural strength. Additionally, [PERSON] [6] designed several mixtures by using various components, achieving a medium strength of 35 MPa in 28 days. The inclusion of chemical and mineral additives mixed with limestone enhanced flowability, adhesion, and performance. The results demonstrated that it was possible to successfully produce self-leveling mortar with performance comparable to that of commercially available products. Chemical additives and mixing characteristics also cause flowability and strength changes during construction. [PERSON] [7] explored the application of alkali-activated binders in self-leveling mortar, showing that the resulting mortar exhibited very high acid resistance and greater frost resistance than Portland cement mortar. [PERSON] [8] investigated the effects of three retarders (protein salt, citric acid, and sodium tripolphosphate) on the setting time. The results indicated that the optimal content of protein salt was 0.1-0.15% (by weight), with 0.1% protein salt extending the setting time of self-leveling mortar to 80 min and corresponding compressive strengths of 54.25 MPa, 53 MPa, and 52.25 MPa. [PERSON] [9] noted that as the water-to-cement ratio increased from 0.54 to 0.84, flowability improved with more water. Mortar with high flowability and very low water-to-cement ratios, as well as that with low flowability and high water-to-cement ratios, was defined by the amount of water used, achieving a flowability value of up to 250%, classifying it as self-compacting mortar. [PERSON] [10] examined the effects of pumping on various types of self-leveling mortar based on basic formulations. The results showed that pumping agents helped increase mortar concentration, but excessive use introduced too many air bubbles, affecting the density and resulting in strength variability. [PERSON] [11] quantified the drying process of self-leveling mortar and linked it to the degree of reaction by using isothermal calorimetry. The activation energy remained constant at about 50 kJ/mol until a hydration degree of approximately 0.5, after which it decreased. [PERSON] [12] investigated the effects of partially replacing cement with different amounts of aluminate cement and SAC on the flowability and strength of self-leveling mortar.