# Eco-Efficient Cement-Based Materials Using Biomass Bottom Ash: A Review
## 3 Biomass Bottom Ash in Mortars  
The use of ash from biomass combustion is conditioned by its physical-chemical properties. There are not many studies that include the use of BBA in construction materials, especially in cement-based materials. Analyzing the origin of the BBA, those that have been mainly used in construction materials are the ones that come from olive waste or other types of trees. The studies  
Figure 2: X-ray diffraction of BBA from olive waste in South of Spain. [PERSON] et al. [7].  
carried out to date have shown the possibility of using BBA with a high silica and calcium content in the manufacture of cement mortars.  
[PERSON] et al. [11] worked on the manufacture of mortars using commercial CEM II/B-LL cement, sand, and bottom ash from spruce chips. Ash was added in various proportions as cement weight replacement (5%, 10%, 20%, 30%), to study its cementing capacity, pozzolanicity, or hydraulicity.  
[PERSON] et al. [6] used BBA from forest residues as an aggregate in the formulation of mortars with a 50% and 100% by weight replacement of commercial sand for BBA. The authors used two different conditions. On the one hand, it manufactured a series sieving the BBA between 250 and 1000 \(\upmu\)m, adjusting the particle size curve to that of the commercial sand frequently used in the formulation of mortars. On the other hand, with the intention of reducing the percentage of soluble salts, the BBA were washed and sieved.  
[PERSON] et al. [18] studied the mechanical behavior of mortars made with BBA and the influence of different variables on their production, such as the type of cement (CEM II 32.5 R, CEM I/N-SR), content of cement (515, 485, and 450 g/L) and the percentage of BBA replacement. Three volumetric replacement ratios were applied from BBA (0%, 10%, and 20%). Standardized sand and cement were substituted by BBA. The authors reported that different behaviors were reproduced according to the type of cement or the type of material replaced; in addition, the BBAs had a low density and high absorption that was reflected in the variability of the strength of the mortars.  
[PERSON] et al. [30] studied physicochemical and mineralogical properties of compacted building blocks made from Portland cement (OPC) and BBA. OPC were replaced by BBA in a range from 10% to 90%.  
[PERSON] et al. [28] designed new cement formulations replacing 10% and 20% of clinker by BBA. The results drawn by the authors show that the new cement properties are not significantly worsened, present lesser shrinkage and swelling, and similar mechanical behavior.  
[PERSON] et al. [29] analyzed the effect of different OPC replacement by BBA (2, 3, 5, 7, and 10 wt%) in mortar mixtures, concluding the BBA could be used in recycled cement until 42.5 class obtained similar mechanical behavior than the mixtures without bottom ashes.  
[PERSON] et al. [21] studied the mechanical and durability properties of mortars made with BBA using different processing methods; there were a total of eight treatments: raw, crushed, calcined, without light particles, crushed and calcined, crushed and without particles light, calcined and without light particles, and finally, crushed- calcined and without light particles.  
Cement was replaced with different BBA substitution rates. The results showed significant improvements in the mechanical properties and durability of the mortars in which some treatments were applied.