# Novel Processing Methods of Low-Clinker Multi-Component Cementitious Materials--A Review
## 2 Ultrasound Treatment (US-T) Methodology
#### US-T of Cementitious Materials/Concrete and SCMs
The presence of agglomerated SF leads to the production of a calcium silicate hydrate (C-S-H)-type product with a longer chain length structure, higher silicon substitution by aluminum, and a lower Ca/Si ratio after US-T.  
Figure 3: (**a**) Real photos of the US-T dispersion-based 3D concrete printing system (main parts: stainless steel frame, chain and pulley drive system, and the printing head), (**b**) schematic diagram of the mixing process and the controlling method for the setting time (with the permission of and recreated using data published in [61]). Figure 2: Isothermal heat release rate, reference total heat, and suspension of sonicated cement during hydration (with permission from [30]). A C-S-H phase with a significantly higher Ca/Si ratio than high-performance concrete was observed when SF agglomerates were present [57]. The reflections associated with C-S-H for SSF showed higher intensity, particularly in materials cured for 60 days [63]. Ultrasonic irradiation increased the number of nanometric particles in SSF (up to 90% compared to 22% without US-T), decreased its mean size to reach 57 nm, increased dispersibility, and significantly enhanced the fc after 28 days of curing (up to 20% with 1% nano-SF). SSF demonstrated higher zeta potential values after 15 min of sonication, indicating high stability and a low propensity to aggregate. SF can enhance concrete strength, reduce porosity, and extend the usable life of concrete structures. The filler effect of SF impacts the physical but not chemical processes [64; 65]. Sonicated SF exhibits higher pozzolanic activity, generating more C-S-H phase [66; 67] due to its higher specific surface area. Another method to increase SF reactivity in PC mortars was described in [68]. The fc of SSF mortar increased up to 15 MPa after 28 days of curing, especially with longer sonication times (20-25 min) and higher sonication power levels (141 W). SSF showed pozzolanic activity following ultrasonic treatment, resulting in the development of new calcium silicate hydrate (C-S-H, calcium aluminate hydrates, ettringite, etc.) products. Cement paste with SSF exhibited up to 43% less Ca(OH)\({}_{2}\) than with non-sonicated SF after 28 days of curing [69], and SSF was uniformly disseminated into the cement paste (Figure 4). Table 1 indicates the efficiency of the US-T on the reactivity of DSF (DSF-1, DSF-2, and DSF-3) with varying chemical compositions, which are equivalent to sonicated SF (SSF-1, SSF-2, and SSF-3, respectively). Pastes produced with SSF showed up to 43% lower CH content compared to pastes made from untreated SF. Sonication treatment significantly increased SF reactivity, resulting in stronger pozzolanic activity when used as a mineral additive in PC systems. At the early curing stages, SSF-2 and SSF-3 exhibited 14% higher reactivity than untreated SF (DSF-2 and DSF-3), and their reactivity with CH increased with the curing age. After 28 days, pastes with SSF-1, SSF-2, and SSF-3 had 36%, 34%, and 43% lower portlandite content compared to pastes with DSF (DSF-1, DSF-2, and DSF-3, respectively) [69]. Adding SF improves early concrete strength and lowers permeability, serving as both a filler and pozzolan [69]. The hydrated paste with SSF showed an atomic Ca/Si ratio in the range of 1.64-1.83, which is attributed to uniform SSF dispersion and C-S-H formation. The zeta potential of SSF increased significantly (up to 71%) with longer sonication times (up to 8 min), indicating improved suspension stability and SSF de-agglomeration. The optimization of the sonication time and the solid-to-liquid ratio of nano-silica cement mortars have been proposed by [PERSON] et al. [70]. Five minutes of sonication at a solid-to-liquid ratio of 1:10 produced the ideal specific surface area and particle size distribution, leading to a 39% increase in the fc of nano-silica cement mortar after 7 days and 25% after 28 days compared to the reference material.