# Eco-Efficient Cement-Based Materials Using Biomass Bottom Ash: A Review
## 4 Biomass Bottom Ash in Concrete  
In recent years, some authors have studied the manufacture of concrete with BBA due to its potential use as a substitute for materials such as natural sand or cement.  
[PERSON] et al. (2019) studied the mechanical and durability properties of nonstructural concrete made with BBA from olive waste and recycled aggregates. Nine batches were made, divided into three groups depending on the percentage of substitution of natural sand by BBA (0%, 3%, and 6%) and the type of coarse aggregate used (natural aggregate, recycled concrete aggregate, or mixed recycled aggregate). In addition, a super-plasticizer additive was added, due to the high water absorption of the BBA, in order to maintain the workability. The results shown indicate a worse mechanical and durability behavior of the concrete made with BBA and recycled aggregates than the concrete made with natural aggregates. However, the series manufactured with BBA and natural aggregate, shows compressive strength values of up to 35 MPa with 6% substitution of NA by BBA, and acceptable durability values, which indicates the real possibility of using this by-product in concrete manufacturing.  
[PERSON] et al. (2015) analyzed the feasibility of manufacturing roller-compacted concrete (RCC) and paver-compacted concrete (PCC) made with BBA from the combustion of waste from the paper industry and wood biomass. BBA was used as a replacement for natural sand in three different percentages (0%, 50%, and 100%) in both types of concrete. Furthermore, to the six mixes were added a water-reducing agent and an air-entraining agent, in order to control the workability properties of fresh concrete. The properties of fresh and hardened concrete properties were studied for both types of concrete, RCC and PCC. It was observed that compactness is an essential factor in the manufacture of RCC and PCC with BBA, since its use implies a high demand for water to maintain adequate workability and reduce porosity.  
[PERSON] et al. (2017) studied the manufacture of conventional concrete made with BBA from cocoa shell and wood chips as a replacement of cement. The concrete was manufactured using BBA with two treatments: sieved, to remove larger particles than 600 \(\upmu\)m and sieved and crushed (GBBA), to obtain a higher degree of fineness. With both processes, concrete made with substitutions in two percentages of BBA (5% and 10%) were analyzed. The physical properties and mechanical behavior of the concrete were studied, observing how the composition of the ashes and their low puzzleolarity have a great influence on them.  
[PERSON] et al. (2017) worked on the possibility of manufacturing lightweight recycled concrete (LRC) with BBA (from olive cake and wood biomass) and mixed recycled aggregates, taking advantage of the lower density of these materials than natural aggregates. Several mixes were made with different substitutions of natural aggregates and lightweight aggregates by BBA and mixed recycled aggregates (MRA), in order to study the workability, mechanical behavior, and durability of the LRC. The results showed a decrease in the characteristics of the concrete made with BBA and MRA; however, all the series manufactured with the different dosages presented compressive strength values within the limits established by the Spanish regulation, (EHE-08) ([PERSON] et al., 2017) for lightweight structural concrete.