# Eco-Efficient Cement-Based Materials Using Biomass Bottom Ash: A Review
## 5 Biomass Bottom Ash in CTGM (Soil Cement) and Soil Stabilization
### Experimental Methods and Results  
This section shows the results of the laboratory tests carried out by each author on the stabilized soil with BBA, cement treatment granular material with BBA, and cement treatment granular soil with BFA in order to analyze the effect of the BBA in soil and natural aggregates with and without cement and establish a comparison between the BBA and BFA effects on mechanical properties of CTGM. [PERSON] et al. [20,24] performed the moisture-density test, according to EN 103 501-94 [63] (Proctor Modified Test), in order to obtain the optimal moisture content to ensure the maximum dry density. Once the optimal moisture content and maximum dry density value had been obtained, all samples were compacted using a vibrating hammer in a cylindrical mold, filling in three layers. The compressive strength was measured according to NLT-305-90 [64]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Mixes** & **ECS wt.\%** & **Quicklime (QL)** & **BBA** & **NA** & **BFA** & **OPC** & **Soil** \\ \hline \hline
**[PERSON] et al. [24]** & & & & & & \\ \hline ECS-1 & 100 & & & & & \\ BBA-2 & & & 100 & & & \\ ECS + BBA-3 & 50 & & 50 & & & \\ ECS + BBA-4 & 85 & & 15 & & & \\ ECS + QL-5 & 95 & 5 & & & & \\
**[PERSON] et al. [20]** & & & & & & \\ \hline Control-6 & & & 0 & 97 & 3 & \\ BBA-7-NA & & & 15 & 82 & 3 & \\ BBA-8-NA & & & 30 & 67 & 3 & \\ MRA-9 & & & 0 & 95 & 5 & \\ BBA-10-MRA & & 15 & 80 & 5 & \\ BBA-11-MRA & & & 30 & 65 & 5 & \\
**[PERSON] et al. [61]** & & & & & & \\ \hline BFA-12 & & & & 14 & 3 & 83 \\ BFA-13 & & & & 13 & 3 & 83 \\ BFA-14 & & & & 21 & 3 & 75 \\ BFA-15 & & & & 8 & 4 & 88 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Proportions of mixes design by authors. [PERSON] et al. [61] made the mixes according to EN 12390-1 [65], filling cube molds which were compacted using a vibrating table. The water content was varied and adapted so all the samples could be made applying that method. The compressive strength was measured according to EN 12390-3 [45]. Table 9 shows the density of all samples analyzed and the compressive strength of cement treatment materials. Density values are related to the compaction of the samples, so under optimal conditions of moisture and compactness CTGM with BBA made by [PERSON] et al. [20] present lower density values than the reference samples, likely due to the lower density of BBA which reduces the total content of cement in a meter cubic of mix. However, no relationship was observed between BBA content and density in the mix made by [PERSON] et al. [61], because the compactness conditions were not optimal. In addition, stabilized soil with BBA has no significant variances present in density values compared to the reference value obtained in the sample stabilized with quicklime. Analyzing the compressive strength values, the soil treated samples made by [PERSON] et al. [61] show a reduction in strength properties with the increase in BBA caused by the uncontrolled compactness and moisture conditions; however, the incorporation of BBA together with cement had positive effects indicating the potential to manufacture binder from BFA. On the contrary, the samples manufactured by [PERSON] el al. [20] show a significant improvement in strength properties due to the incorporation of BBA in both series, with increases of 25% on average between 7 and 28 days. In addition, analyzing the stress-strain relationship obtained from strength test which were carried out on the mixes, the modulus of elasticity was determined. The elastic properties of a cement-treated soil allow estimating the bearing capacity of a pavement since higher elastic modulus implies a better traffic load distribution, generating less distortion which guarantees an adequate structural behavior of the road over its lifetime. Figure 5 shows the results of compressive strength and modulus of elasticity obtained by [PERSON] et al. [20].