## 3 Results and Discussion
### Cement Sludge Fines (CSF)
#### 3.2.2 CSF for Soil Stabilization  
The soil used as a reference had the chemical composition shown in Table 6, while its Atterberg limits were as follows: liquid limit LL: 56, plastic limit PL: 29.4 and plasticity Index PI: 26.6. Overall, it was categorized as poor for subgrade. Figure 17 shows the dry density versus moisture content for soil with 0%, 10% and 20% soil addition. As shown in Table 7, the dry density increased as the CSF rate increased while the required moisture in order to reach the maximum dry density reduced. Both of these properties are desirable for soil stabilization, but the most significant increase is that of the load-bearing capacity of soils, expressed by the CBR value. Furthermore, a higher percentage of CSF increased the CBR value even more. A similar strength increase has been reported (at lower addition percentages) when using lime for soil improvement [42; 43]. Figure 16: XRD diagram of cement mortar with 80% cement and 20% CSF, where C: calcite, P: portladite, Q: quartz, Awf: Awfillite, CSH: hydrated cement. Figure 17: Dry density versus moisture content for soil stabilized with various CSF additions. [PERSON]; [PERSON]; [PERSON] Review of Strategy for Recycling and Reuse of Waste Materials. In _Recycling and Reuse of Sewage Sludge, Proceedings of the International Symposium Organised by the Concrete Technology Unit and Held at the University of Dunade, Scotland, UK, 19-20 March 2001_; [PERSON], [PERSON], [PERSON], [PERSON]; [PERSON]: London, UK, 2001; pp. 325-336. * [PERSON] and [PERSON] (2016) [PERSON]; [PERSON] Evaluation of concrete recycling system efficiency for ready-mix concrete plants. _Waste Manag._**2016**, 56, 337-351. [CrossRef] [PubMed]
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