Experimental and numerical study of preplaced aggregate concrete reinforced with tire- recycled steel fibers

نوع: Type: Thesis

مقطع: Segment: PHD

عنوان: Title: Experimental and numerical study of preplaced aggregate concrete reinforced with tire- recycled steel fibers

ارائه دهنده: Provider: Roya raeisi

اساتید راهنما: Supervisors: Dr Freydoon Rezaie

اساتید مشاور: Advisory Professors: Dr Mohammad Reza Mohammad Aliha

اساتید ممتحن یا داور: Examining professors or referees: , Dr.Mostafa Moghadasi, Dr. Moosa Mazloom, Dr.Seyed Mohammad Jafari

زمان و تاریخ ارائه: Time and date of presentation: 2025

مکان ارائه: Place of presentation: 43

چکیده: Abstract: Abstract: Preplaced aggregate concrete is an emerging type of concrete, characterized by its unique construction method. It is used in underwater locations and areas where placing, compacting, and consolidating fresh concrete is not easily feasible. Additionally, it is suitable for repair works and large-scale projects, as it prevents aggregate segregation and facilitates concreting in cold and hot weather conditions. Given the extensive applications of preplaced aggregate concrete, examining and improving its performance can significantly benefit the construction industry. In the present study, the effects of the volume of industrial steel fibers, recycled steel fibers from tires, and Forta-Ferro fibers on the mechanical properties and fracture behavior of preplaced aggregate concrete have been investigated. In this regard, notched flexural disk specimens were used to evaluate the fracture parameters of preplaced aggregate concrete. Additionally, fiber volume percentages of 1%, 1.5%, and 2% were considered for Forta-Ferro fibers and industrial steel fibers, while percentages of 0.33%, 0.66%, and 1% were assigned for waste steel fibers recovered from scrap tires. To investigate the fracture modes of preplaced aggregate concrete, pure mode I, mode II, mode III, and mixed- modes I/II and I/III were examined. A total of 270 specimens were tested to assess preplaced aggregate concrete's mechanical and fracture properties. For validation of experimental results, a one-way analysis of variance (ANOVA) was conducted using SPSS software. The results indicated that fracture toughness depends on loading conditions. The lowest and highest fracture toughness values corresponded to specimens subjected to pure mode III and mode II, respectively. Additionally, comparing the effects of industrial steel fibers and recycled steel fibers from tires revealed that recycled fibers had a similar impact on improving the mechanical and fracture properties of preplaced aggregate concrete. The experimental results demonstrated that in specimens reinforced with industrial and recycled steel fibers, the fracture toughness of preplaced aggregate concrete generally increased with higher fiber volumes. However, this trend was not observed for Forta-Ferro fibers. Specifically, the mechanical and fracture properties of preplaced aggregate concrete improved with the addition of Forta-Ferro fibers up to 1.5%, but further increasing the fiber volume to 2% reduced their effectiveness. Thus, the optimal volume of Forta-Ferro fibers in preplaced aggregate concrete is 1.5%. Statistical analyses were also conducted on the experimental results of preplaced aggregate concrete specimens containing Forta-Ferro fibers under various fracture modes to validate the findings. The statistical analysis confirmed that, at a 95% confidence level, the experimental results were statistically significant.

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