# Stabilisation of Soft Clay, Quick Clay and Peat by Industrial By-Products and Biochars
## 3 Results  
### The Characterisation of Natural Soils and Binders  
Results from the \(w\), \(\rho_{s}\) and SFA determinations are shown in Table 2. The \(w\) of the Tiller-Flotten quick clay (42%) was lower than that of the Onsey clay (73%); however, the SFA was similar for both clays. The IBPs and biochars exhibited a large variation in \(w\), although all were dried prior to being mixed with the natural soils. The PSA, BA, LS1 and BC2 had a \(w\approx\) 0% (Table 2). The biochars had varying \(w\), \(\rho_{s}\) and SFA. The high SFA of the biochars BC1, BC2 and BC3 was expected [26, 27]. The results of the compositional (XRF) and phase (XRD) analyses are shown in Tables 3-5. In general, the compositions were similar to those of previously published results. For example, the two ladle slags had high contents of SiO\({}_{2}\) and CaO [65, 79]. The PSA also showed similar compositions as those reported in the literature, albeit with somewhat lower CaO contents [53]. The BC2 was particularly high in CaO because of the addition of limestone to the sludge prior to pyrolysis. Similarly, the BC3 contained a high amount of Fe\({}_{2}\)O\({}_{3}\) because of the addition of iron chloride in the sedimentation process. This also resulted in higher particle densities compared to BC1 and BC4 (Table 2). Bassanite (Ca(SO\({}_{4}\)) \(\bullet\) 0.5H\({}_{2}\)O) was identified in the CEM I sample at a concentration of 7.2% (Table 5). Bassanite was unexpected, but the chemical composition favoured the phase with sulphur and calcium at reasonable levels (Table 3). It was expected to find C\({}_{3}\)A (3 CaO \(\bullet\) Al\({}_{2}\)O\({}_{3}\)), a common constituent in cement, but no compelling evidence was present in the diffractograms. The high amorphous content (Table 5) made it difficult to argue for an aluminium-containing phase (C\({}_{2}\)A) instead of a calcium-sulphate phase. Results from the TGA for the natural soils are plotted in Figure 2, together with their respective derivative differential thermogravimetry (DTG) values. The clays displayed DTG peaks at approximately 480 \({}^{\circ}\)C for the Onsey clay and 590 \({}^{\circ}\)C and 670 \({}^{\circ}\)C for the Tiller-Flotten clay, corresponding to the dehydroxylation of clay minerals such as illite and chlorite. The Tiller-Flotten clay also contained 2.1% calcite (Table 4), which was most likely reflected by the peak at approximately 590 \({}^{\circ}\)C. The TGA on peat naturally exhibited a high weight loss due to the high organic content, as could also be observed concerning the high LOI and amorphous contents in the XRF and XRD analyses, respectively. Overall, the results agree with both XRF and XRD as well as previous studies [40, 41]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**Material**}} & **Water Content** & **Particle Density** & **SFA** \\  & **[\%]** & **[\(\mathbf{t}\)/\(\mathbf{m}^{3}\)]** & **[\(\mathbf{m}^{2}\)/g]** \\ \hline \multirow{3}{*}{Natural soils} & Tiller-Flotten quick clay & 42 & 2.85 & 23.26 \\  & Tiller-Flotten peat & 886 & \(\sim\)1.45 & 1.28 \\  & Onsey clay & 73 & 2.7 & 25.24 \\ \hline Cement & CEM I & \(\sim\)0 & 2.55 & 1.54 \\ \hline Sludge & PSA & \(\sim\)0 & 2.68 & 3.9 \\ \hline \multirow{3}{*}{Bioash} & FA & 42.5 & 2.85 & 3.0 \\  & BA & \(\sim\)0 & 2.69 & 0.5 \\ \hline \multirow{3}{*}{Ladle slag} & LS1 & \(\sim\)0 & 3.02 & 0.8 \\  & LS2 & 19.8 & 2.99 & 11.0 \\ \hline \multirow{3}{*}{Biochar} & BC1 & 98.4 & 1.61 & 38.5 \\  & BC2 & \(\sim\)0 & 2.44 & 54.8 \\ \cline{1-1}  & BC3 & 35.5 & 2.34 & 51.3 \\ \cline{1-1}  & BC4 & 85.3 & 1.67 & 5.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Results of water content, particle density and specific surface area (SFA) determinations. Note that the water contents for the IBPs and biochars were determined after receiving the binders in the laboratory. Before mixing with the soil, all IBPs and biochars were dried.