Investigation of the interfacial shear strength between precast prestressed joist and FORTA fiber-reinforced topping concrete

نوع: Type: Thesis

مقطع: Segment: masters

عنوان: Title: Investigation of the interfacial shear strength between precast prestressed joist and FORTA fiber-reinforced topping concrete

ارائه دهنده: Provider: Neda Afroukhteh

اساتید راهنما: Supervisors: DR. Freydoon Rezaie

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: DR. Mostafa Moghadasi,DR. Amir Rezaie Sameti

زمان و تاریخ ارائه: Time and date of presentation: 2026

مکان ارائه: Place of presentation: 44

چکیده: Abstract: Composite concrete members hold a prominent position in civil engineering due to their high load-bearing capacity, reliable structural performance, and extensive application in strengthening, retrofit-ting, and concrete overlays. The effective performance of these members largely relies on the stress transfer mechanism and bond strength at the interface between existing and newly cast concrete. Ac-cordingly, this thesis investigates the effects of surface roughness and Forta-Ferro fiber dosage on the interfacial shear strength of concrete. To this end, specimens were fabricated with two surface condi-tions (smooth and rough) and three fiber volume fractions (0%, 0.5%, and 1.0%). Their structural re-sponse was evaluated using a modified push-off test, and the interfacial shear strength was deter-mined. The experimental results indicated that surface roughening was the most critical factor en-hancing shear capacity; for non-fibrous specimens, the average shear strength increased from 1.85 MPa for smooth surfaces to 3.67 MPa for rough surfaces. Furthermore, incorporating 0.5% Forta fi-bers considerably enhanced the shear performance, yielding the highest resistance in both surface cat-egories—reaching 2.82 MPa and 4.41 MPa for smooth and rough surfaces, respectively. Increasing the fiber content to 1.0% led to a slight reduction in shear strength compared to the 0.5% dosage, though it remained higher than that of the fiber-free control specimens. This reduction can be attributed to decreased mix workability, non-uniform fiber distribution, and localized interfacial discontinuities. Additionally, three-dimensional laser surface scanning and point-cloud analyses were conducted to quantify roughness parameters and evaluate their correlation with interfacial shear strength. The findings confirm that the enhanced shear capacity is governed by the synergistic effect of mechanical interlock induced by surface roughness and the crack-arresting mechanism of the optimized fiber dosage.