PSI - Issue 64

Nathália Andrade da Silva et al. / Procedia Structural Integrity 64 (2024) 1460–1467 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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3. Sieving - After the particles crushing, sieving is performed to separate the different size of bio-aggregates from the powders to coarse or fine aggregates. 4. Homogenization - The bio-aggregates sieving is followed by homogenization to ensure their uniformity.

Fig. 1. Bamboo bio-aggregate produced by (a) Industrial crusher and knife mill (Silva, 2019); (b) Industrial crusher with smaller tooth opening (Siqueira et al. 2023).

Incorporating plant-based aggregates into cement mixtures represents a significant challenge due to their interaction with the binders. During the early contact between vegetable biomass and cement paste, sugars and extractives are dissolved and as consequence, the cement hydration reactions can be inhibited (Da Gloria, et al, 2021). Therefore, pre-treatment of the bio-aggregates is essential before their insertion into the matrix. Various treatment methods are currently available for this purpose. Several methods are available for removing extractives from bio-aggregates. The most utilized treatments for bamboo particles are either washing the particles with hot water or immersing them in an alkaline solution (Table 2). One method that has been employed involves washing the bio-aggregates in hot water at 80ºC, using a ratio of 1:10 (bio-aggregates: water), by mass. Bezerra et al. (2021) examined the impact of three different treatments on the hydration process of bamboo bio-concretes. The treatments investigated included soaking in hot water for one hour, immersion in saturated calcium hydroxide solution for one and two hours. The findings indicate that immersion in hot water for one hour was found to be the most effective treatment for bamboo particles. This method can effectively dissolve the extractives. After thorough rinsing with running water, the resulting bio-aggregates can be incorporated into the matrix without significantly affecting the cement hydration process. Based on the studies of Da Gloria (2020) for wood bio-concrete, alkaline treatment was used to remove the extractives from the bamboo aggregates in the studies carried out by Sá (2022). This method consisted in immersing the bamboo particles in an alkaline solution with a ratio of 7 parts water to 1 part bamboo, along with 1.85 grams of calcium hydroxide per liter of water for one hour.

Table 2. Bamboo aggregates treatments.

Author

Treatment

Andreola (2017) 3 bathes in hot water (80 ºC) for one hour each Silva (2019), Lima (2020), Andreola (2021), Siqueira et al. (2023) 1 bath in hot water (80 ºC) for one hour Sá (2022) Immersion in alkaline solution for one hour

2.2. Dosage of bamboo bio-concrete In order to produce bamboo bio-concrete, Andreola (2017) proposed a rational dosage method with the purpose of developing bio-concretes of 270 ± 20 mm spread. The dosage methodology used consisted of: • Treatment of the bio-aggregates; • Determination of water absorbed by the bio-aggregates; • Definition of a spreading interval for fresh bio-concrete; • Choice of a volumetric fraction of bio-aggregates (45 - 52.5%); • Choice of the water-to-cement ratio (0.40 - 0.50) that allows the framing of fresh bio-concrete in the pre defined spreading range. It is worth mentioning the importance of the water absorbed by the bio-aggregates for the dosage. This water is named compensating water and its addition is crucial to prevent the absorption of water destined for cement