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Structural Behavior of Sustainable ECC Produced By 3D Concrete Printing
Bakir, Ahmad Hitham
Bakir, Ahmad Hitham
Description
A Master of Science thesis in Civil Engineering by Ahmad Hitham Bakir entitled, “Structural Behavior of Sustainable ECC Produced By 3D Concrete Printing”, submitted in August 2021. Thesis advisor is Dr. Adil K. Al-Tamimi. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).
Abstract
The fourth industrial revolution has crossed the threshold of the construction sector by introducing machinery capable of implementing construction tasks, and this auto-manufacturing process is called 3D Concrete Printing (3DCP). It reducces waste, time, workforce and the ability to design complex projects due to the absence of formwork. The key point for a successful 3D printing process is the right selection of printing materials. Earlier research has shown that the brittleness and weakness of the concrete against tension are the main characteristics affecting the widespread of this technology. The aim of this research is to develop Engineered Cementitious Composites (ECC) mixture suitable for the 3DCP process (3D-ECC). The main features of ECC are the tensile strain-hardening properties and ductile failure behavior. The experimental program addressed the fresh properties of the developed 3D-ECC through flowability percentage, initial setting time, extrudability and buildability. A total of 153 specimens have been used to evaluate the mechanical properties such as compressive strength, flexural strength, tensile strength and strain capacity. 80 trial mixes were performed, and one chosen as optimal mix. The flowability percentage and initial setting time for the developed mix were 50% and 14 minutes respectively. The compressive, flexural and tensile strength was 82.0 MPa, 14.2 MPa and 7.73 MPa respectively. In printed samples the test orientation affects the compressive and flexural strength. The compressive strength in the printed samples showed range of 27.9 MPa up to 36.9 MPa for different testing orientations modes. The flexural strength increased to 14.78 Mpa and 18.65 Mpa depends on loading orientation. The printed dog-bone specimens reduced the tensile strength to 4.06 MPa. The tensile strain capacities were 5.21% and 4.79 for the control and printed samples respectively. Both control and printed specimens maintained the tensile strain-hardening behavior. It was observed that replacing cement type I with type V in the control mixes negatively impacted the mechanical performance. The 2% volume fraction of PE-fiber showed higher improvement on the mechanical properties, compared to 3%, 1.5%, 1%, 0.5% and 0%. Finally, flexural strength was increased by 35.7% in R/ECC compared to RCC specimens.