Incorporation of Natural Fibres in Rendering Mortars for the Durability of Walls
Abstract
:1. Introduction
2. Materials and Methods
Materials
- REF 1:4—reference cement mortar at 1:4 volumetric ratio (0% incorporation);
- REF 1:1:6—reference cement-lime mortar at 1:1:6 volumetric ratio (0% incorporation);
- W 1.5-20cl—20% wool fibre incorporation at 1:1:6 volumetric ratio;
- C 1.5-20cl—20% coir fibre incorporation at 1:1:6 volumetric ratio;
- F 1.5-20cl—20% flax fibre incorporation at 1:1:6 volumetric ratio.
3. Methods
4. Results and Analysis
4.1. Wall Protection-Related Properties
4.1.1. Water Absorption
4.1.2. Water Evaporation upon Drying
4.1.3. Open Porosity
4.1.4. Water Permeability
4.1.5. Modulus of Elasticity
4.1.6. Dimensional Variation
4.1.7. Adherence Strength
4.2. Evaluation of Durability Performance of the Mortar Based on the Artificial Accelerated Ageing Test
4.2.1. Visual Aspect
4.2.2. Modulus of Elasticity before and after Ageing
4.2.3. Water Permeability before and after Ageing
4.2.4. Open Porosity before and after Ageing
4.2.5. Adherence to Substrate before and after Ageing
5. Conclusions
- The fibres’ addition increased the water absorption capillary coefficient of the mortars. However, the total amount of water absorbed was similar for all the mortars with cement and lime as binary binder. Additionally, the drying rate increases in the mortars with fibres, which reduces the risk of long time wetting;
- Regarding the open porosity of the mortars, it was concluded that, at 365 days, the incorporation of fibres did not affect the volume of interconnected voids inside the mortars. Furthermore, after the artificial accelerated ageing test, the mortars with natural fibres were less permeable to water under pressure, which indicates less microcracks inside their structure;
- In terms of the cracking performance, it was confirmed that the addition of fibres reduced the modulus of elasticity of the mortars, which indicates that the natural fibre-reinforced mortars were able to absorb more imposed deformations than those without fibres. This effect could be due to the lower modulus of elasticity of the fibres when compared to that of the reference mortars;
- A decrease in shrinkage was observed in the mortars with flax and wool fibres when compared with the reference mortar, which suggest that these mortars are less susceptible to cracking when compared to REF 1:1:6;
- At 28 days, the incorporation of fibres in cement-lime mortars did not show a significant effect on the adherence strength. Nonetheless, after the artificial accelerated ageing process, the type of natural fibres affected differently in the mortars. The incorporation of flax fibres increased 5% the adhesive strength when compared to that of REF 1:1:6. On the other hand, when coir fibres were added, a reduction of about 17% was observed;
- Concerning the durability of the mortars, it was found that the addition of natural fibres hindered the microcracking of the lime-cement mortars during the accelerated ageing cycles, as shown by the higher results of the dynamic modulus of elasticity of the reinforced mortars after ageing compared to before ageing. Additionally, although all lime-cement mortars suffered an increase of the water permeability under pressure after ageing, which increase was slight compared to the more pronounced increment registered by the reference lime-cement mortar. The permeability results are somehow confirmed by the porosity values, which indicate that the reinforced mortars suffer no increase or, in one case, only a slight increase of porosity during the ageing cycles. These results suggest an improvement of durability of the mortars with incorporation of natural fibres and do not indicate an effect of degradation of the fibres.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Test | Ages Analysed (Days) | European Standard | Specimens |
---|---|---|---|
Water absorption by capillarity | 28, 365 | EN 1015-18 [21] | Prism |
Drying | 28, 365 | EN 16322 [22] | Prism |
Open porosity | 28, 365, after ageing | EN 1936 [23] | Half of Prism |
Artificial ageing | 28 | EN 1015-21 [24] | Brick |
Aesthetical appearance | 28, after ageing | - | Brick |
Adherence strength to the substrate | 28, after ageing | EN 1015-21 [24] | Brick |
Permeability to water under pressure | 28, after ageing | EN 1015-21 [24] | Brick |
Modulus of elasticity by ultra-sound pulse velocity | 28, after ageing | EN 12504-4 [25] | Brick |
Shrinkage | up to 90 | Cahier 2669-4 [26] | Prism |
Mortar | Before Ageing (28 Days) | After Ageing | ||
---|---|---|---|---|
E (GPa) | σ | E (GPa) | σ | |
REF 1:4 | 5.58 | 0.08 | 5.32 | 0.24 |
REF 1:1:6 | 4.70 | 0.06 | 4.75 | 0.63 |
W 1.5-20cl | 3.90 | 0.14 | 4.27 | 0.64 |
C 1.5-20cl | 3.37 | 0.36 | 4.09 | 0.30 |
F 1.5-20cl | 4.11 | 0.41 | 4.74 | 0.27 |
Mortar | Before Ageing (28 Days) | After Ageing | ||
---|---|---|---|---|
Permeability to Water under Pressure (mL/cm2) | σ | Permeability to Water under Pressure (mL/cm2) | σ | |
REF 1:4 | 2.89 | 0.18 | 2.26 | 0.52 |
REF 1:1:6 | 3.61 | 0.02 | 4.24 | 0.09 |
W 1.5-20cl | 3.34 | 0.18 | 3.70 | 0.01 |
C 1.5-20cl | 3.52 | 0.09 | 4.24 | 0.54 |
F 1.5-20cl | 2.71 | 0.18 | 3.43 | 0.00 |
Mortar | Before Ageing (28 Days) | After Ageing | ||
---|---|---|---|---|
Open Porosity (%) | σ | Open Porosity (%) | σ | |
REF 1:4 | 16.50 | 0.54 | 18.83 | 0.22 |
REF 1:1:6 | 17.22 | 0.34 | 17.68 | 0.57 |
W 1.5-20cl | 18.10 | 0.20 | 18.65 | 0.73 |
C 1.5-20cl | 18.05 | 0.26 | 18.02 | 0.98 |
F 1.5-20cl | 18.25 | 0.30 | 18.20 | 0.77 |
Mortar | Before Ageing (28 Days) | After Ageing | ||||
---|---|---|---|---|---|---|
Adherence (MPa) | Predominant Type of Failure | σ | Adherence (MPa) | Predominant Type of Failure | σ | |
REF 1:4 | 0.55 | A | 0.03 | 0.76 | A | 0.03 |
REF 1:1:6 | 0.33 | A | 0.06 | 0.41 | A/B | 0.33 |
W 1.5-20cl | 0.33 | A | 0.05 | 0.38 | A | 0.46 |
C 1.5-20cl | 0.30 | A/B | 0.07 | 0.34 | A | 0.40 |
F 1.5-20cl | 0.41 | A | 0.12 | 0.43 | B | 0.36 |
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Maia Pederneiras, C.; Veiga, R.; de Brito, J. Incorporation of Natural Fibres in Rendering Mortars for the Durability of Walls. Infrastructures 2021, 6, 82. https://doi.org/10.3390/infrastructures6060082
Maia Pederneiras C, Veiga R, de Brito J. Incorporation of Natural Fibres in Rendering Mortars for the Durability of Walls. Infrastructures. 2021; 6(6):82. https://doi.org/10.3390/infrastructures6060082
Chicago/Turabian StyleMaia Pederneiras, Cinthia, Rosário Veiga, and Jorge de Brito. 2021. "Incorporation of Natural Fibres in Rendering Mortars for the Durability of Walls" Infrastructures 6, no. 6: 82. https://doi.org/10.3390/infrastructures6060082