# New Insights into Cement-Soil Mixtures with the Addition of Fluidized Bed Furnace Bottom Ashes
## 2 Materials and Methods
### Materials

Table 1: Chemical composition of bottom ash. The research on the rheological properties (slurry density, apparent viscosity, and 24-h water setting time) of cement slurries was conducted in accordance with the BN-90 1785-01 standard [28]. The volumetric density of soil-cement mixtures was determined using the direct method in accordance with the PN-EN 1936:2010 [29] standard (similar to that for mortar). The strength tests on the developed mixtures were conducted in two stages: initially, the properties of cementitious pastes with the addition of bottom ash and microsilica were analyzed. Microsilica is a by-product of silicon metal production. It is a dense, amorphous powder obtained in the silicon metallurgy process in an electric arc furnace. It is used as an additive to primarily improve the mechanical properties of concrete and mortar formulations. After examining the properties of the pastes, cement-soil mixtures were prepared in the next stage. Each time, the samples were divided based on the type of cement used: CEM I (Gorazdze 42.5 R) and CEM II/B-V (Polski Portland 32.5 R). The material's behavior in cohesive soils was analyzed, with clay chosen to simulate the soil medium. The material testing was conducted on three samples, and the averaged properties of the clay used are presented in Table 2.  
The mixtures were divided into two groups using CEM I (MIX I to IV) and CEM II (MIX V to VIII). Samples MIX I and V were reference samples. MIX II and VI replaced 10% of the cement mass with grinded bottom ash. MIX III and VII replaced 15% of the cement mass with 10% of grinded bottom ash and 5% microsilica. MIX IV and MIX VIII replaced 15% of the cement mass with grinded bottom ash. In addition to the paste samples, soil-cement samples based on clay were also prepared. The detailed compositions of mixtures for pastes and soil-cement are presented in Table 3 below. The mixing process was carried out in accordance with the PN EN 196-1 standard [30]. Upon the contact of water with cement and ash in the mixing vessel, mixing was initiated at a low speed for 30 s. The moment of water contact with the binding components was recorded as time \"0\" for further tests in accordance with point 8.4 of the standard. Subsequently, clay was evenly added within 30 s. High-speed mixing was then initiated for 30 s. The mixer was stopped for 90 s, and within the first 30 s, the components were scraped from the edge of the bowl to the center using a rubber tool. Mixing was continued at a high speed for one minute. The samples, along with the forms, were placed in containers with water above the water level. After 24 h, the samples were demolded and placed again in the containers with water on a rack above the water level. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Fraction Content [\%]**} & \\ \hline
**Clay** & **Silt** & **Sand** & **Gravel** & **Moisture [\%]** & **Bulk Density** \\
**(-0.002 mm)** & **(0.002–0.063 mm)** & **(0.063–2 mm)** & **(2–63 mm)** & & **[kN/m3]** \\ \hline
28.73 & 68.8 & 2.47 & 0 & 20.98 & 19.13 \\ Plastic limit, & & The liquid limit & Plasticity index, IP & Liquidity index, IL \\ wP [\%] & & wL [\%] & [\%] & [-] \\
37.44 & & 41.69 & 4.255 & \(-\)3.87 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Properties of cohesive soil average of three samples. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{3}{c}{Cementitious Grout—CEM I Görazdze (42.5 R)} \\ MIX & 1 & 2 & 3 & 4 \\ \hline Water mass [g] & 1500 & 1500 & 1500 & 1500 \\ Cement mass [g] & 2000 & 1800 & 1700 & 1700 \\ Bottom ash mass [g] & 0 & 200 & 200 & 300 \\ Microsilica mass [g] & 0 & 0 & 100 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Compositions of mixtures for one batch.