# New Insights into Cement-Soil Mixtures with the Addition of Fluidized Bed Furnace Bottom Ashes
## 5 Conclusions  
The research focused on mixtures applicable for soil stabilization in active and post-mining areas as well as during tunneling. Investigations into mixtures aligning with the 'green concrete' trend were conducted over a period of 2 years for mortars and 28 days for cement-soil blends. The use of combustion by-products in concrete mixtures may worsen the water-to-cement ratio. These by-products often contain a high content of inert components, requiring more water to ensure the desired consistency. In this study, a constant water-to-binder ratio (c+FBA) was maintained to meet the required rheological properties in jet grouting technology. Employing CEM II as the primary binding material for mixtures with combustion by-products (CBP) may slow down the concrete strength gain process, especially in the first 14 days. CEM II is a type of Portland cement that includes fly ash or slag as major components. While such mixtures may be more environmentally friendly and beneficial for waste recovery, they can impact the chemical reaction rate between water and cement, causing delays in the setting and hardening of concrete. This delay associated with the use of CEM II may be critical in the initial two weeks when achieving the desired concrete or  
Figure 8: UCS values of samples obtained by the manufactured JG columns [43]. cement-soil strength is crucial. Introducing CEM II-based mixtures in production settings would need to be considered in early-stage work schedules. The addition of microsilica to concrete mixtures containing a significant amount of ashes (resulting from the simultaneous use of CEM II and combustion by-products) can significantly improve their properties. Microsilica, a type of mineral admixture added to concrete, consists of very fine particles with a large surface area. Its presence in the mixture yields beneficial effects for both traditional Portland cement (CEM I) and blended cement (CEM II) containing ashes. When microsilica is added to a mixture based on CEM I, an improvement in strength can be observed within the first three days after casting. Microsilica acts as an additional filler, filling the gaps between cement and aggregate particles, leading to a higher density and a better concrete structure. In mixtures containing both CEM II and combustion by-products, the use of microsilica has a similar effect. Microsilica helps fill gaps and voids between cement, ashes, and aggregate particles, resulting in better compaction and higher mixture density. As a result, the concrete becomes more durable and resistant to loads, positively impacting the longevity and stability of structures. The use of CEM II may negatively affect the water tightness of mixtures, as more cracks are observed in CT images. Tomographic studies revealed no correlation between porosity and mixture strength. Further research is needed to analyze and assess the destruction mechanism of cement-soil blends. In-situ studies in a computer tomography chamber could prove valuable for a more comprehensive understanding. The research can be summarized with the following points:  
1. The use of combustion by-products in concrete mixtures may worsen the water-to-cement ratio, affecting the mix consistency. 2. CEM II, while environmentally beneficial, may slow down the concrete hardening process, especially during the first 14 days. 3. Microsilica significantly improves the properties of the concrete mix, including its density and strength, both in traditional cement and in mixtures with CEM II. 4. Microsilica helps improve the durability and stability of concrete, increasing its resistance to loads. 5. The use of CEM II may negatively impact the water tightness of concrete mixtures, leading to more cracks. 6. The lack of correlation between porosity and mixture strength suggests the need for further research into the destruction mechanisms of cement-soil blends. 7.