PSI - Issue 78

Sandoli Antonio et al. / Procedia Structural Integrity 78 (2026) 1342–1349

1346

10 12 14

Jute reinf. mortar Broom reinf. mortar Hemp reinf. mortar Waste wood reinf. mortar Flax reinf. mortar

0 2 4 6 8

Engineering

Materials Science

Numb. of paper

Physics and Astronomy

Environmental Science

Energy

Computer Science

Social Sciences

Chemistry

Chemical Engineering

Earth and Planetary Sciences

Agricultural and Biological Sciences

Business, Management and Accounting

2005

2010

2015 Year

2020

2025

Mathematics

Medicine

Arts and Humanities

a)

b)

Fig. 3. Number of papers about natural fiber reinforced mortar: a) by type of fiber, b) by sectors.

3. Insights from experimental tests In this Section some remarks on the mechanical performances of natural fiber-reinforced mortar are reported, focusing the attention on the main parameters affecting the increase/decrease of flexural and compression strength, such as fiber percentage and fiber length. The authors have elaborated an extended database collecting experimental data available in the technical literature; for the sake of brevity such data are not listed in the present paper, but the main achievements are discussed only. Fig. 4 reports some comparisons in terms of dimensionless strength vs fiber length, obtained by varying the fiber percentage with respect to mortar mass. In such diagrams, f m and f c indicates the flexural and compression strength of the reinforced mortar specimens, while the subscripts ‘R’ and ‘Un’ refer to Reinforced and Unreinforced mortar, respectively. Instead, the fiber percentage by mortar weight is reported in the legend of each diagram. Note that dimensionless strengths used to represent the results allow to compare tests results independently from the type of mortar (and then from its strength) used in the experimental campaign, delivering for more general discussion and conclusions about the behavior of natural fiber-reinforced mortar. In particular, the diagrams of Fig. 4a refer to the flexural and compression tests conducted by Majumder et al. 2023 on jute reinforced mortar, while Fig. 4b and 4c to the tests carried out by Sandoli et al. 2025 and Juradin et al. 2021 both on broom fiber-reinforced mortar. All the selected tests regard three-point flexural and uniaxial compression tests, conducted on standardized specimens having standard dimensions 40x40x160 mm and according to standardized recommendations (UNI EN 196-1 and UNI EN 1015-11). From a general standpoint, the main outcomes coming from the experimental tests point out as the addition of fibers involves a reduction either of flexural and compression strength of the composite mortar with respect to those unreinforced: in fact, the strength ratios f m,R / f m,Un and f c,R / f m,Un are lower than the unit in all the analyzed cases, independently from fiber-type, fiber percentage and fiber length. The strength reduction is mainly attributable to the addition of the fibers into the mortar mixtures causing a density reduction of the composite material: as the fiber percentage increases the strength reduces also significantly. On this topic, the mortar mixture also plays a key role, because the mixing phase of the mortar can cause the formation of fiber nets which creates local reduction of the cross-section, voids, non-uniform distribution of the fiber within the mortar specimens thus the fibers do not provide an effective contribution into proving the expected additional tensile strength to the material. To overcome such an issue, a careful mixing phase of the composite material should be done during the specimen preparation together with a shaking of the specimens before placing in maturation.