# Stabilisation of Soft Clay, Quick Clay and Peat by Industrial By-Products and Biochars
## 3 Results
### The Characterisation of Natural Soils and Binders
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Material** & **C\({}_{2}\)S \({}^{2}\)** & **C\({}_{2}\)S \({}^{3}\)** & **C\({}_{4}\)F \({}^{4}\)** & **Calcite** & **Portlandite** & **Quartz** & **Merwinite** & **CaO-Lime** & **Others \({}^{1}\)** & **Amorphous** \\ \hline Cement & CEM I & 8.1 & 47.4 & 10.2 & - & - & - & - & - & 7.2 & 27.2 \\ \hline Sludge & PSA & - & - & - & 19.4 & 2.3 & 12.9 & 13.7 & 4.8 & 4.8 & 42.2 \\ \hline Biosh & FA & - & - & - & 48.5 & 3.8 & - & - & - & 13.1 & 32.5 \\  & BA & - & - & 13.3 & 0.1 & 6.9 & - & - & 16.0 & 3.8 & 59.9 \\ \hline Ladle slag & LS1 & - & - & - & - & - & - & 20.5 & - & 42.3 & 37.2 \\  & LS2 & - & - & - & - & 48 & - & 11.7 & - & 24.1 & 59.4 \\ \hline Biochar & BC1 & - & - & - & 1.3 & - & 0.6 & - & - & 0.6 & 97.5 \\  & BC2 & - & - & - & 35.3 & - & 3.1 & - & - & 6.6 & 55.0 \\  & BC3 & - & - & - & - & - & 6.4 & - & - & 10.0 & 83.7 \\  & BC4 & - & - & - & 2.6 & - & 7.5 & - & - & 11.1 & 78.9 \\ \hline \hline \end{tabular} \({}^{1}\) CEM I: bassanite (7.2%). PSA: anhydrite (3.7%), rutile (1.1%). FA: fluorapatite (8.3%), arcantile (2.7%), thematic (1.3%), hematite (0.8%). BA: magnestic (1.4%), pericidase (2.4%). LS1: Calclo-olivline (25.9%), laronite (1.2%), gehlenite (9.3%), clinoenstatite (5.9%). LS2: calclo-olivline (18.9%), gehlenite (2.7%), zeolite (2.5%). BC1: rutile (0.6%). BC2: illite+cma (2.4%), K-feldspar (1.6%), plagioclase (2.6%). BC3: K-feldspar (2.8%), plagioclase (4.3%), magnetite (2.9%). BC4: illite+cma (1.7%), K-feldspar (3.7%), plagioclase (4.8%), amphibole (0.8%), dolomite (0.1%), 2\({}^{2}\), C\({}_{2}\)S = di-calcium silicate (bitle), 2\({}^{3}\), C\({}_{2}\)S/O\({}_{2}\). \({}^{3}\), C\({}_{3}\)S = tri-calcium silicate (alite), 3\({}^{4}\)CaOSiO\({}_{2}\). \({}^{4}\), CaF = tetra-calcium alumo ferrite (feitle), 4\({}^{3}\)CaOAl\({}_{2}\)O\({}_{3}\) Fe\({}_{2}\)O\({}_{3}\).  
\end{table} 
Table 5: Results of X-ray diffraction analyses (XRD) of cement and industrial by-products, showing minerals in crystalline phase and amorphous separately. All values in per cent. TGA and DTG results for the CEM, IBPs and biochars are shown in Figure 3. The FA and LS2, in particular, had a high weight loss in the temperature range of approximately 40-120 \({}^{\circ}\)C as the free and adsorbed water evaporated, in line with the high water content determinations. The BA and LS2 showed additional weight loss at temperatures of 380-480 \({}^{\circ}\)C, i.e., dehydration of \(\text{Ca(OH)}_{2}\). These also had the highest content of portlandite, as shown by the XRD analyses. At temperatures of 700-800 \({}^{\circ}\)C, the FA and PSA exhibited weight loss due to the decomposition of \(\text{CaCO}_{3}\). Again, this was observed in the XRD analyses with high calcite contents. Two outlying results were identified: a weight increase for the PSA at temperatures of 380-630 \({}^{\circ}\)C and for LS1 at temperatures of 900-1050 \({}^{\circ}\)C. A possible reason for this might be baseline drift during the TGA tests; however, despite this, it should be of no particular relevance to the stabilisation effect of the binders. In general, the TGA and DTG analyses of the IBPs were similar to those found in the literature [54, 61, 65, 69, 81]. The TGA and DTG results for the biochar showed similar characteristics as those for the peat, i.e., a gradual weight loss over a large temperature range. This was expected since they had relatively similar compositions, as observed in the XRF analyses. One exception was the BC2, which exhibited a DTG peak at temperatures of 700-800 \({}^{\circ}\)C, i.e., decomposition of the \(\text{CaCO}_{3}\) due to the high calcite content, as was observed in the XRD analysis. Figure 2: Results from thermogravimetric analyses on natural soils: (**a**,**b**) Onsey and Tiller-Flotten clay, (**c**,**d**) peat.