Research Article
Mechanical Performance and Reliability Assessment of Nanosilica-Modified High-Strength Concrete Beams
Ooye Steve Toba,
John Wasiu,
Ibrahim Abdulrazaq Olayinka*
,
Osegbowa Douglas Enoguan
Issue:
Volume 15, Issue 3, September 2026
Pages:
80-90
Received:
15 June 2026
Accepted:
26 June 2026
Published:
17 July 2026
DOI:
10.11648/j.am.20261503.11
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Abstract: The growing demand for high-performance and durable construction materials has led to increasing interest in nanotechnology applications in concrete. This study investigates the mechanical properties, microstructural behavior, and structural reliability of high-strength concrete beams (HSCBs) incorporating nanosilica as a partial cement replacement. Experimental investigations were conducted on concrete mixes containing 0%, 3%, 5%, and 7% nanosilica by weight of cement. Material characterization included sieve analysis, specific gravity, water absorption, and density tests for aggregates, while nanosilica was evaluated using SEM/EDX and FTIR to examine its morphology and chemical interactions. Compressive strength tests were performed at 7, 14, 21, and 35 days, and flexural strength tests were conducted on reinforced concrete beams. Results showed significant improvements in both compressive and flexural strengths with nanosilica incorporation, with the optimum performance observed at 5% replacement, achieving up to 18% higher compressive strength than the control mix. Microstructural analysis confirmed enhanced formation of calcium silicate hydrate (C–S–H) gel and pore refinement due to nanosilica’s pozzolanic reactivity and filler effect. Furthermore, structural performance was evaluated using both deterministic design methods and reliability-based analysis (FORM), demonstrating that nanosilica-modified beams achieved higher reliability indices and reduced probabilities of failure. The study concludes that controlled incorporation of nanosilica significantly enhances the strength, durability potential, and structural safety of high-strength concrete beams.
Abstract: The growing demand for high-performance and durable construction materials has led to increasing interest in nanotechnology applications in concrete. This study investigates the mechanical properties, microstructural behavior, and structural reliability of high-strength concrete beams (HSCBs) incorporating nanosilica as a partial cement replacement...
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Research Article
Effect of Precursor Solution Volume on Structural and Optical Properties of Iron Doped Titanium Dioxide Thin Films Prepared by Spin Coating
Chemutai Sharon*,
John Njagi,
Jatani Ungula,
Sharon Kiprotich
Issue:
Volume 15, Issue 3, September 2026
Pages:
91-98
Received:
18 June 2026
Accepted:
1 July 2026
Published:
22 July 2026
Abstract: The influence of precursor solution volume on the characteristics of containing iron-doped titanium dioxide (Fe:TiO2) thin films was examined in this work. The coatings were prepared on transparent substrates by the spin-coating method using precursor volumes between 0.5 and 2.5 mL. Following deposition, the coatings were heat treated at 450°C and analyzed using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-Vis) spectroscopy. XRD analysis revealed the presence of both rutile and anatase crystalline phases, evidenced by reflections near 27.4° and 49° corresponding to the (110) and (200) planes, respectively. Variations in precursor volume affected the crystallographic properties of the films, with the sample prepared using 1.0 mL exhibiting the largest crystallite size and sharper diffraction peaks, suggesting improved crystal growth. Increasing the precursor volume beyond this value resulted in peak broadening, which may be associated with greater lattice imperfections and strain within the films. The FTIR results identified characteristic vibrational bands assigned to Ti-O-Ti and Ti-O-Fe linkages, confirming the incorporation of iron species into the TiO2 network. Optical characterization showed that increasing precursor volume shifted the absorption threshold toward longer wavelengths and reduced the optical band gap. This behavior can be ascribed to the creation of defect-induced energy states and oxygen-vacancy states within the material. Overall, the findings demonstrate that precursor solution volume significantly affects both the crystallographic and photonic performance of Fe:TiO2 coatings, with the 1.0 mL sample providing the most favorable combination of crystallinity and film quality.
Abstract: The influence of precursor solution volume on the characteristics of containing iron-doped titanium dioxide (Fe:TiO2) thin films was examined in this work. The coatings were prepared on transparent substrates by the spin-coating method using precursor volumes between 0.5 and 2.5 mL. Following deposition, the coatings were heat treated at 450°C and ...
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Research Article
Growth Time-dependent Structural and Optical Properties of Hydrothermally Synthesized ZnO Thin Films
Issue:
Volume 15, Issue 3, September 2026
Pages:
99-109
Received:
14 June 2026
Accepted:
25 June 2026
Published:
18 August 2026
Abstract: The present study investigates the influence of growth time on the physical properties of ZnO thin films grown by the hydrothermal method. Film fabrication is carried out via a two-step process involving the deposition of ZnO seed layers on glass substrates by spin coating, followed by hydrothermal growth. Post-deposition annealing at 400°C for 3 hours is performed to enhance crystallinity. Structural and optical properties are analyzed using X-ray diffraction (XRD), UV–visible spectroscopy, and photoluminescence (PL) spectroscopy. XRD results confirm that all films are polycrystalline with a hexagonal wurtzite structure and exhibit a pronounced preferential orientation along the (002) plane. The progressive increase in the (002) peak intensity with growth time indicates enhanced crystalline quality, accompanied by an increase in crystallite size from 11.19 to 14.67 nm. UV–visible analysis shows that transmittance decreases from 95% to 65% with increasing growth time, mainly due to increased film thickness and density. However, films grown between 2 and 5 hours provide a good compromise between high transmittance in the visible region and strong absorption in the ultraviolet region. The optical bandgap varies from 3.14 eV to 3.27 eV, attributed to changes in film thickness. PL spectra exhibit three emission bands centered at 412 nm (3.01 eV), 438 nm (2.83 eV), and 490 nm (2.53 eV), associated with intrinsic defects in ZnO. The films grown for 4 hours exhibit relatively low defect density and good visible transmittance, making them promising candidates for photovoltaic applications.
Abstract: The present study investigates the influence of growth time on the physical properties of ZnO thin films grown by the hydrothermal method. Film fabrication is carried out via a two-step process involving the deposition of ZnO seed layers on glass substrates by spin coating, followed by hydrothermal growth. Post-deposition annealing at 400°C for 3 h...
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Research Article
Experimental Investigation on Partial Replacement of Steel Reinforcement by CFRP Bars in Reinforced Concrete Beams
Issue:
Volume 15, Issue 3, September 2026
Pages:
110-131
Received:
20 July 2026
Accepted:
6 August 2026
Published:
24 August 2026
DOI:
10.11648/j.am.20261503.14
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Abstract: The corrosion of conventional steel reinforcement remains a major durability concern in reinforced concrete members exposed to chlorides, carbonation, moisture and industrial chemicals, because progressive section loss and bond deterioration can reduce stiffness, serviceability and structural reliability. Carbon fiber-reinforced polymer (CFRP) bars provide high tensile strength, low density and excellent resistance to electrochemical corrosion; however, their linear-elastic response up to rupture and comparatively different bond and stiffness characteristics can produce brittle failure and limited warning when they are used as the sole longitudinal reinforcement. The present study experimentally investigates partial replacement of steel tensile reinforcement by CFRP bars in reinforced concrete beams, with the objective of identifying a hybrid reinforcement ratio that improves strength and durability while retaining an acceptable level of deformation capacity. Five M30 concrete beam specimens, each measuring 700 mm x 100 mm x 100 mm, were prepared with constant geometry, concrete grade, loading arrangement and total number of bottom tensile bars. The specimens B-S100, B-C25, B-C50, B-C75 and B-C100 represented 0%, 25%, 50%, 75% and 100% CFRP replacement, respectively. The experimental programme comprised M30 mix proportioning, reinforcement cage fabrication, tensile characterization of steel and CFRP bars, 28-day curing and four-point flexural testing in accordance with the general principles of relevant concrete and composite testing standards. During testing, first-crack load, ultimate load, mid-span deflection, ductility index, energy absorption, stiffness, crack development and expected failure characteristics were evaluated. The adopted M30 mix contained 394 kg/m3 cement, 197 L/m3 water, 787 kg/m3 fine aggregate and 1082 kg/m3 coarse aggregate at a water-cement ratio of 0.50. Material testing indicated a peak load of 39.30 kN at 4.70 mm displacement for the steel sample and 45.95 kN at 6.80 mm for the CFRP sample, confirming the higher tensile resistance of CFRP while emphasizing the need to preserve the yielding contribution of steel in hybrid members. The beam results showed a systematic increase in first-crack load from 4.2 kN for B-S100 to 5.2 kN for B-C100 and an increase in ultimate load from 18.50 kN to 31.00 kN. Conversely, ultimate deflection reduced from 10.5 mm to 6.2 mm and the ductility index decreased from 3.50 to 1.20 as CFRP replacement increased. Among the hybrid configurations, B-C50 developed an ultimate load of 24.80 kN, an ultimate deflection of 9.00 mm, a ductility index of 2.70 and the maximum energy absorption of 133 N-m. It also provided the most favorable combined response in terms of strength enhancement, crack control, deformation reserve and energy dissipation. The findings demonstrate that full CFRP replacement maximizes flexural capacity but substantially reduces ductile warning, whereas moderate hybridization permits the complementary use of steel yielding and CFRP tensile resistance, as reported in previous hybrid beam research. Accordingly, 50% CFRP replacement is recommended as the optimum configuration for the present small-scale beam system. This recommendation is limited to the adopted geometry, material properties and test conditions, and should be validated through replicated tests, larger specimens, long-term durability exposure and numerical modelling before application to full-scale structural design.
Abstract: The corrosion of conventional steel reinforcement remains a major durability concern in reinforced concrete members exposed to chlorides, carbonation, moisture and industrial chemicals, because progressive section loss and bond deterioration can reduce stiffness, serviceability and structural reliability. Carbon fiber-reinforced polymer (CFRP) bars...
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