3.2.6. Thermal Stability Analysis

The thermal degradation stability of the mixed cement pastes containing 0%, 5%, 10%, 15%, and 20% CMW immersed in tap water for 7 days are displayed in Figure 7. The main first endothermic peak appeared at a temperature below 100 ◦C, because of the removal of the physically adsorbed water. The second endothermic peak was observed at approximately 100–180 ◦C due to the decomposition of CSH overlapping with calcium sulfoaluminate hydrates (ettringite and mono-sulfate hydrates). The third endothermic peak, located at approximately 475–500 ◦C, is characterized by the decomposition of portlandite Ca(OH)2. The two ends of the overlapping endothermic peaks at 670–700 and 720–750 ◦C are related to the calcination of calcite (CaCO3), with different degrees of crystallinity. The thermograms obtained for the hardened bare OPC paste display the areas and intensities of the peaks characteristic for CSH and Ca(OH)2, which included the main hydration products. Beyond these areas, the peaks increase with increasing the hydration age. The effects of the partial replacement of the OPC by CMW cause a decrease in the peak area characteristic for the CSH, with increasing slag compared with that of the neat OPC paste. Furthermore, the peak area of Ca(OH)2 observed in the thermograms decreased with the increasing CMW, due to the increase in their additional amounts. The thermograms obtained

for all of the hardened cement pastes show an intensive endotherm characteristic for CaCO3 and an increase with an increase in the amounts of mud.

**Figure 7.** Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) analysis of OPC–CMW blended cement pastes containing 5, 10, 15, and 20 wt. % calcined CMW nanoparticles.

### *3.3. Production Costs*

The major goal of the present study is the argument of CMW from sugar factories, a waste originating after the carbonation process. In particular, waste materials as blended cement pastes or in the construction industry are improving the production process from economic aspects, and present an eco-friendly, viable option. Many published papers used various wastes, including palm oil mill waste [54], sewage sludge ash [55], rice husk, limestone, and the waste of activated mining coal [56]. All of the studies found that applying this disposal at a certain ratio presents a great advantage from economic, sustainable, and environmental viewpoints. Li and Yang [2] reported the utilization of Portland cement with sugar filter cake as the source of lime-based raw material, and the optimum replacement level was less than 20%. From an energy efficiency viewpoint, CMW will help reduce the need for excessive energy requirements during the stages of production, which may be beneficial for certain applications for which the energy and cost savings are vital, such as CO2 reduction and improving the impact of climate change [57]. The incorporation of CMW not only lowered the needed energy, but also minimized the electricity consumption and saved time compared with the materials needed from natural resources. Moreover, the cost of transportation is ultimately diminished, and the economic implications of utilizing CMW instead of other costly materials, such as ZnO or TiO2, is encouraging [58]. Mathematically, at normal operation, 60 tons of CMW are discharged per day, which requires at least six trucks. The cost of each truck is 40 SR, which is equal to \$10.66. In this manner, the total annual cost equivalent was 870.000 SR (\$232.222) in 2018, for example. Therefore, incorporating CMW into OPC enhances the cost-saving criteria and inserts green building infrastructure components to improve the engineering economy factor.

### **4. Conclusions**

In summary, important considerations and informative data were presented to evaluate the feasibility of utilizing calcined CMW (5–25 wt. %) from a sugar refining company in the cement industry. The expected outcomes from this study provide guidelines regarding the characteristics of CMW, its engineering performance, and its sustainability. According to the overall methodology and characterization tests, the variation in the results for the different samples is not substantial, but a level of 15 wt.% is nearly acceptable and suitable for all of the parameters of hardened cement paste, as it contributes to a better waste management system, improves the sustainability in the cement industry, and prevents pathogenic effects during transportation. The small particle size of CaO with an average of ~50–100 nm is satisfactory for OPC compatibility. The compressive strength values (kg/cm2) were studied for all of the curing ages. The engineering and environmental impacts were also affirmative concerning the amount of greenhouse gas emissions, daily energy consumption, and economic factors. Furthermore, CMW can reduce the cost of construction by up to \$230 per year.

**Author Contributions:** Conceptualization, Y.A.; Data curation, A.-A.M.G. and A.E.-A.S.F.; Investigation, T.A. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.

### **References**


© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
