Microstructural Characterization of Hybrid Polypropylene-Glass Fibre Reinforced Concrete Using Scanning Electron Microscopy

Ram Bhupal Reddy Anna Reddy; Jayarami Reddy Bommi Reddy

doi:doi:10.11648/j.ajce.20261405.16

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Microstructural Characterization of Hybrid Polypropylene-Glass Fibre Reinforced Concrete Using Scanning Electron Microscopy

Ram Bhupal Reddy Anna Reddy^*, Jayarami Reddy Bommi Reddy

Published in American Journal of Civil Engineering (Volume 14, Issue 5)

Received: 8 September 2026 Accepted: 20 September 2026 Published: 8 October 2026

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Abstract

Concrete is a brittle cementitious material with limited tensile strength and a tendency to develop microcracks and propagate cracks under mechanical and environmental loading. The incorporation of fibres can improve crack control and enhance the integrity of the cementitious matrix. The present study experimentally investigates the microstructural characteristics of hybrid polypropylene (PP) and glass fibre reinforced concrete with different total fibre volume fractions and fibre combinations. Plain cement concrete was considered as the reference mixture, while hybrid fibre mixtures were prepared with total fibre contents of 0.25%, 0.50%, 0.75%, and 1.00%, incorporating different proportions of PP and glass fibres. Scanning Electron Microscopy (SEM) was employed to examine fibre dispersion, fibre-matrix interaction, interfacial transition zone characteristics, crack bridging, matrix compactness, and void formation. The microstructural observations indicate that the incorporation of hybrid fibres improves crack interruption and matrix continuity compared with plain concrete. Glass fibre-rich mixtures showed effective bridging and arrest of comparatively larger cracks, whereas polypropylene fibres contributed primarily to the control of fine microcracks. Balanced PP-glass combinations exhibited comparatively uniform fibre dispersion and multi-scale crack-bridging behaviour. Increasing fibre content generally improved crack control and matrix refinement; however, at higher fibre dosages, localized fibre crowding, overlapping, and entrapped voids were observed, particularly in polypropylene-rich mixtures. The study demonstrates that the microstructural performance of hybrid fibre reinforced concrete depends on both the total fibre volume fraction and the relative proportion of PP and glass fibres. The findings provide a basis for identifying suitable hybrid fibre combinations for improving the microstructural integrity, crack resistance, and potential durability of concrete.

Published in	American Journal of Civil Engineering (Volume 14, Issue 5)
DOI	10.11648/j.ajce.20261405.16
Page(s)	356-369
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2026. Published by Science Publishing Group

Keywords

Hybrid Fibre Reinforced Concrete, Polypropylene Fibre, Glass Fibre, Scanning Electron Microscopy, Microstructure, Fibre Dispersion, Fibre-matrix Interface, Interfacial Transition Zone

References

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APA Style

Reddy, R. B. R. A., Reddy, J. R. B. (2026). Microstructural Characterization of Hybrid Polypropylene-Glass Fibre Reinforced Concrete Using Scanning Electron Microscopy. American Journal of Civil Engineering, 14(5), 356-369. https://doi.org/10.11648/j.ajce.20261405.16

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ACS Style

Reddy, R. B. R. A.; Reddy, J. R. B. Microstructural Characterization of Hybrid Polypropylene-Glass Fibre Reinforced Concrete Using Scanning Electron Microscopy. Am. J. Civ. Eng. 2026, 14(5), 356-369. doi: 10.11648/j.ajce.20261405.16

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AMA Style

Reddy RBRA, Reddy JRB. Microstructural Characterization of Hybrid Polypropylene-Glass Fibre Reinforced Concrete Using Scanning Electron Microscopy. Am J Civ Eng. 2026;14(5):356-369. doi: 10.11648/j.ajce.20261405.16

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@article{10.11648/j.ajce.20261405.16,
  author = {Ram Bhupal Reddy Anna Reddy and Jayarami Reddy Bommi Reddy},
  title = {Microstructural Characterization of Hybrid Polypropylene-Glass Fibre Reinforced Concrete Using Scanning Electron Microscopy},
  journal = {American Journal of Civil Engineering},
  volume = {14},
  number = {5},
  pages = {356-369},
  doi = {10.11648/j.ajce.20261405.16},
  url = {https://doi.org/10.11648/j.ajce.20261405.16},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ajce.20261405.16},
  abstract = {Concrete is a brittle cementitious material with limited tensile strength and a tendency to develop microcracks and propagate cracks under mechanical and environmental loading. The incorporation of fibres can improve crack control and enhance the integrity of the cementitious matrix. The present study experimentally investigates the microstructural characteristics of hybrid polypropylene (PP) and glass fibre reinforced concrete with different total fibre volume fractions and fibre combinations. Plain cement concrete was considered as the reference mixture, while hybrid fibre mixtures were prepared with total fibre contents of 0.25%, 0.50%, 0.75%, and 1.00%, incorporating different proportions of PP and glass fibres. Scanning Electron Microscopy (SEM) was employed to examine fibre dispersion, fibre-matrix interaction, interfacial transition zone characteristics, crack bridging, matrix compactness, and void formation. The microstructural observations indicate that the incorporation of hybrid fibres improves crack interruption and matrix continuity compared with plain concrete. Glass fibre-rich mixtures showed effective bridging and arrest of comparatively larger cracks, whereas polypropylene fibres contributed primarily to the control of fine microcracks. Balanced PP-glass combinations exhibited comparatively uniform fibre dispersion and multi-scale crack-bridging behaviour. Increasing fibre content generally improved crack control and matrix refinement; however, at higher fibre dosages, localized fibre crowding, overlapping, and entrapped voids were observed, particularly in polypropylene-rich mixtures. The study demonstrates that the microstructural performance of hybrid fibre reinforced concrete depends on both the total fibre volume fraction and the relative proportion of PP and glass fibres. The findings provide a basis for identifying suitable hybrid fibre combinations for improving the microstructural integrity, crack resistance, and potential durability of concrete.},
 year = {2026}
}

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TY  - JOUR
T1  - Microstructural Characterization of Hybrid Polypropylene-Glass Fibre Reinforced Concrete Using Scanning Electron Microscopy
AU  - Ram Bhupal Reddy Anna Reddy
AU  - Jayarami Reddy Bommi Reddy
Y1  - 2026/10/08
PY  - 2026
N1  - https://doi.org/10.11648/j.ajce.20261405.16
DO  - 10.11648/j.ajce.20261405.16
T2  - American Journal of Civil Engineering
JF  - American Journal of Civil Engineering
JO  - American Journal of Civil Engineering
SP  - 356
EP  - 369
PB  - Science Publishing Group
SN  - 2330-8737
UR  - https://doi.org/10.11648/j.ajce.20261405.16
AB  - Concrete is a brittle cementitious material with limited tensile strength and a tendency to develop microcracks and propagate cracks under mechanical and environmental loading. The incorporation of fibres can improve crack control and enhance the integrity of the cementitious matrix. The present study experimentally investigates the microstructural characteristics of hybrid polypropylene (PP) and glass fibre reinforced concrete with different total fibre volume fractions and fibre combinations. Plain cement concrete was considered as the reference mixture, while hybrid fibre mixtures were prepared with total fibre contents of 0.25%, 0.50%, 0.75%, and 1.00%, incorporating different proportions of PP and glass fibres. Scanning Electron Microscopy (SEM) was employed to examine fibre dispersion, fibre-matrix interaction, interfacial transition zone characteristics, crack bridging, matrix compactness, and void formation. The microstructural observations indicate that the incorporation of hybrid fibres improves crack interruption and matrix continuity compared with plain concrete. Glass fibre-rich mixtures showed effective bridging and arrest of comparatively larger cracks, whereas polypropylene fibres contributed primarily to the control of fine microcracks. Balanced PP-glass combinations exhibited comparatively uniform fibre dispersion and multi-scale crack-bridging behaviour. Increasing fibre content generally improved crack control and matrix refinement; however, at higher fibre dosages, localized fibre crowding, overlapping, and entrapped voids were observed, particularly in polypropylene-rich mixtures. The study demonstrates that the microstructural performance of hybrid fibre reinforced concrete depends on both the total fibre volume fraction and the relative proportion of PP and glass fibres. The findings provide a basis for identifying suitable hybrid fibre combinations for improving the microstructural integrity, crack resistance, and potential durability of concrete.
VL  - 14
IS  - 5
ER  -

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Author Information

Ram Bhupal Reddy Anna Reddy

Department of Civil Engineering, Rajiv Gandhi University of Knowledge Technologies, Rajiv Knowledge Valley, India; Department of Civil Engineering, YSR Engineering College of Yogi Vemana University, Proddatur, India

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Jayarami Reddy Bommi Reddy

Department of Civil Engineering, YSR Engineering College of Yogi Vemana University, Proddatur, India

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APA Style

Reddy, R. B. R. A., Reddy, J. R. B. (2026). Microstructural Characterization of Hybrid Polypropylene-Glass Fibre Reinforced Concrete Using Scanning Electron Microscopy. American Journal of Civil Engineering, 14(5), 356-369. https://doi.org/10.11648/j.ajce.20261405.16

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ACS Style

Reddy, R. B. R. A.; Reddy, J. R. B. Microstructural Characterization of Hybrid Polypropylene-Glass Fibre Reinforced Concrete Using Scanning Electron Microscopy. Am. J. Civ. Eng. 2026, 14(5), 356-369. doi: 10.11648/j.ajce.20261405.16

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AMA Style

Reddy RBRA, Reddy JRB. Microstructural Characterization of Hybrid Polypropylene-Glass Fibre Reinforced Concrete Using Scanning Electron Microscopy. Am J Civ Eng. 2026;14(5):356-369. doi: 10.11648/j.ajce.20261405.16

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@article{10.11648/j.ajce.20261405.16,
  author = {Ram Bhupal Reddy Anna Reddy and Jayarami Reddy Bommi Reddy},
  title = {Microstructural Characterization of Hybrid Polypropylene-Glass Fibre Reinforced Concrete Using Scanning Electron Microscopy},
  journal = {American Journal of Civil Engineering},
  volume = {14},
  number = {5},
  pages = {356-369},
  doi = {10.11648/j.ajce.20261405.16},
  url = {https://doi.org/10.11648/j.ajce.20261405.16},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ajce.20261405.16},
  abstract = {Concrete is a brittle cementitious material with limited tensile strength and a tendency to develop microcracks and propagate cracks under mechanical and environmental loading. The incorporation of fibres can improve crack control and enhance the integrity of the cementitious matrix. The present study experimentally investigates the microstructural characteristics of hybrid polypropylene (PP) and glass fibre reinforced concrete with different total fibre volume fractions and fibre combinations. Plain cement concrete was considered as the reference mixture, while hybrid fibre mixtures were prepared with total fibre contents of 0.25%, 0.50%, 0.75%, and 1.00%, incorporating different proportions of PP and glass fibres. Scanning Electron Microscopy (SEM) was employed to examine fibre dispersion, fibre-matrix interaction, interfacial transition zone characteristics, crack bridging, matrix compactness, and void formation. The microstructural observations indicate that the incorporation of hybrid fibres improves crack interruption and matrix continuity compared with plain concrete. Glass fibre-rich mixtures showed effective bridging and arrest of comparatively larger cracks, whereas polypropylene fibres contributed primarily to the control of fine microcracks. Balanced PP-glass combinations exhibited comparatively uniform fibre dispersion and multi-scale crack-bridging behaviour. Increasing fibre content generally improved crack control and matrix refinement; however, at higher fibre dosages, localized fibre crowding, overlapping, and entrapped voids were observed, particularly in polypropylene-rich mixtures. The study demonstrates that the microstructural performance of hybrid fibre reinforced concrete depends on both the total fibre volume fraction and the relative proportion of PP and glass fibres. The findings provide a basis for identifying suitable hybrid fibre combinations for improving the microstructural integrity, crack resistance, and potential durability of concrete.},
 year = {2026}
}

Copy | Download

TY  - JOUR
T1  - Microstructural Characterization of Hybrid Polypropylene-Glass Fibre Reinforced Concrete Using Scanning Electron Microscopy
AU  - Ram Bhupal Reddy Anna Reddy
AU  - Jayarami Reddy Bommi Reddy
Y1  - 2026/10/08
PY  - 2026
N1  - https://doi.org/10.11648/j.ajce.20261405.16
DO  - 10.11648/j.ajce.20261405.16
T2  - American Journal of Civil Engineering
JF  - American Journal of Civil Engineering
JO  - American Journal of Civil Engineering
SP  - 356
EP  - 369
PB  - Science Publishing Group
SN  - 2330-8737
UR  - https://doi.org/10.11648/j.ajce.20261405.16
AB  - Concrete is a brittle cementitious material with limited tensile strength and a tendency to develop microcracks and propagate cracks under mechanical and environmental loading. The incorporation of fibres can improve crack control and enhance the integrity of the cementitious matrix. The present study experimentally investigates the microstructural characteristics of hybrid polypropylene (PP) and glass fibre reinforced concrete with different total fibre volume fractions and fibre combinations. Plain cement concrete was considered as the reference mixture, while hybrid fibre mixtures were prepared with total fibre contents of 0.25%, 0.50%, 0.75%, and 1.00%, incorporating different proportions of PP and glass fibres. Scanning Electron Microscopy (SEM) was employed to examine fibre dispersion, fibre-matrix interaction, interfacial transition zone characteristics, crack bridging, matrix compactness, and void formation. The microstructural observations indicate that the incorporation of hybrid fibres improves crack interruption and matrix continuity compared with plain concrete. Glass fibre-rich mixtures showed effective bridging and arrest of comparatively larger cracks, whereas polypropylene fibres contributed primarily to the control of fine microcracks. Balanced PP-glass combinations exhibited comparatively uniform fibre dispersion and multi-scale crack-bridging behaviour. Increasing fibre content generally improved crack control and matrix refinement; however, at higher fibre dosages, localized fibre crowding, overlapping, and entrapped voids were observed, particularly in polypropylene-rich mixtures. The study demonstrates that the microstructural performance of hybrid fibre reinforced concrete depends on both the total fibre volume fraction and the relative proportion of PP and glass fibres. The findings provide a basis for identifying suitable hybrid fibre combinations for improving the microstructural integrity, crack resistance, and potential durability of concrete.
VL  - 14
IS  - 5
ER  -

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