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

1465

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2.5. Mechanical properties - Compressive strength

Analyzing the mechanical properties of bio-concretes concerning compressive strength, it is observed in Table 4 that the studies present a variation in the volumetric fraction of bamboo aggregates, ranging from 25% to 50%, along with diversity in the water-to-cementitious materials ratio, varying from 0.30 to 0.50. A wide variation in compressive strength was also observed, ranging from 21.05 MPa to 2.25 MPa, and in the elastic modulus, from 1.30 to 10.73 GPa. Overall, it is emphasized that the increase in the volumetric fraction of bamboo is related to the reduction of both uniaxial compressive strength and modulus of elasticity (E). All studies agree that the stress-strain curves of bamboo bio-concretes exhibit an elastoplastic behavior, attributed to the energy absorption of bamboo particles. Changes in dosage, mainly in binder content and biomass fraction, enable the development of materials with differentiated behaviors. Another factor influencing the mechanical strength of bio-concretes is the water-to cement ratio, where it is observed that reducing this ratio increases the mixture strength.

Table 4. Bamboo bio-concretes compressive strength values. Bamboo aggregates Matrix w/cm

Compressive strength (MPa)

E (GPa) 2.31-2.35 1.51-2.01

Ref.

45% 50% 25% 45% 45% 30% 50% 35% 45% 25%

C C

0.40-0.50 0.40-0.50

3.93-4.20 2.57-2.25

Andreola (2017) Andreola (2017) Silva (2019) Silva (2019) Lima (2020) Andreola (2021) Andreola (2021)

C+Mk+FA C+Mk+FA C+Mk+FA C+Mk+FA C+Mk+FA

0.40 0.40 0.40 0.30 0.30 0.30 0.30 0.30

21.05 12.30 8.11 14.1

6.75 3.03 2.30 5.20 1.10

8.1

C+Mk+FA+SOIL C+Mk+FA+SOIL C+Mk+FA+SAND

8.61-9.29 6.01-7.05

3.00-3.32 1.38-1.78

Sá (2022) Sá (2022) Siqueira et al.(2023)

14.93

10.73

2.6. Thermo-hygric behavior of bamboo bio-concrete

Sá (2022) is the sole researcher to have assessed the thermo-hygienic characteristics of bamboo bio-concrete so far. The tests conducted measured Moisture Buffer Value (MBV) and Water Vapor Permeability (WVP). MBV quantifies a material's capacity to absorb and release moisture from its surroundings, while WVP determines how relative humidity affects water vapor permeability. According to Nordtest's classification, the bio-concretes in this study are considered exceptional for exchanging moisture with the environment, as they demonstrated an MBV value exceeding 2.0 g/(m².%RH). Specifically, bio concretes containing 35% and 45% bamboo aggregates exhibited values of 3.67 and 3.79 g/(m².%RH), respectively (Table 5) . This outcome can be attributed to bamboo’s hygroscopic nature and high porosity, which facilitate water transport within the bio-concrete (Sá, 2022). The data from WVP analysis indicates that the mixture containing 35% bamboo bio-aggregates exhibited a water vapor permeability 91.0% lower than the mixture with 45% (Table 3). These findings highlight the significant impact of biomass volume on water vapor permeability and resistance parameters. The WVP test assesses the movement of water vapor through a material, requiring interconnected pores to facilitate this process. Bamboo particles play a crucial role in creating conduits for water vapor within the material, leading to an increase in permeability. Besides that, increasing the volume of bamboo affects both the flow of water vapor and reduces the matrix volume that presents closed microstructure with small pores (Sá, 2022).

Table 5. Thermo-hygric properties of bamboo bio-concrete.

MVB [g/(m².%RH)]

Water vapor resistance

WVP [kg/(m.s.Pa)]

% Bio-aggregate

35 45

3.67 3.79

1.23 x 10 -11 2.35 x 10 -11

15.88

8.35