# Novel Processing Methods of Low-Clinker Multi-Component Cementitious Materials--A Review
## 4 Microwave Treatment (MW-T) Methodology
### MW-T of Cementitious Materials/Concrete and SCMs
Microwave curing developed a granular C-S-H gel with a high Ca/Si atomic ratio (nearly 3.5) in hydrated PC. Microwave curing and steam curing increased the polymerization of C-S-H gel compared to conventional curing. In addition, MW-T curing for 45 min resulted in a greater hydration of PC than steam curing at 80 \({}^{\circ}\)C for 4 h or conventional curing for 12 h. Microwave and steam curing hastened the hydration of C3S and C2S, respectively. Compared to steam curing and normal curing, microwave curing substantially expedited cement hydration while also increasing the content of medium capillary pores in the hardened paste. In order to determine microwave curing's impact on the development of fc in mortar made with the cement-GGBFS evolution of temperature and the water-to-binder ratio, as well as the composite binder and its underlying process during curing, the hydration products and the microstructure of the composite system were studied [140]. The findings demonstrate that the highest microwave-curing temperature is slightly lower, and the final water-to-binder ratios are slightly lower as GGBFS content increases. Due to its long reaction time with water, GGBS is referred to as a latent hydraulic substance [141]. The ST test tangentially demonstrates the microwave's non-thermal action on composite systems. Steam curing is less effective than microwaves at carbonating composite binders. Together with the acceleration of hydration at early ages, a key element in improving the fc of composed with the cement-mortar-GGBFS composite binder is the reduction in detrimental pores. The microwave's drying effect can greatly reduce mortar's porosity by lowering the water-to-binder ratio. Moreover, the hydration of composite systems can be accelerated by the thermal and non-thermal effects of microwaves, and microwave curing can enhance and homogenize the pore structure of mortar. The characteristics of magnesium phosphate cement were affected by using a microwave oven in the calcination of MgO by [PERSON] et al. [142]. Microwave radiation preferentially links particles with larger dielectric loss during this calcination process, which differs from conventional calcination. If the dopant has a low dielectric loss, a doped powder that can be successfully and quickly calcined in a normal oven may not necessarily show the same results when calcined in a microwave. The microwave calcination was effective in the process of decreasing the MgO surface area and, as a result, in increasing the cement's setting time. This allowed for greater control of the reactions during the setting, producing specimens with a low open porosity and high mechanical strength, but it also increased the tendency to exudate certain volumes of water. To create conductive gratings using a carbon nanotube (CNT), [PERSON] et al. [143] combined a cement composite with aluminum silicate ceramic fiberboard as the dielectric layer, resulting in a unique and practical cementitious metastructure. The microwave absorption of prepared specimens was greatly enhanced by an absorbing metastructure based on CNT gratings. The metastructure (24 mm) periodicity gratings demonstrated multi-band absorption capabilities with five peaks less than \(-\)20 dB. The metastructure (14/24 filling fraction gratings) demonstrated excellent broadband absorption performance with a reflectance peak of \(-\)38.7 dB and bandwidth of \(-\)15 dB at 13.0 GHz. The temperature distribution, structural compactness, and strength development of the Cemented Tailings Backfill (CTB) can all be significantly impacted by MW-T, according to [PERSON] et al. [144]. Underground mined-out sections are filled with CTB, typically made by combining tailings, a binder, and water. To ensure safe and effective mining production, the CTB should soon reach sufficient strength when buried. With varied curing ages, solid contents, and binder-to-tailings ratios when the same MW-T is applied, the CTB exhibits different thermal and mechanical behavior.