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Dissertation Defence: Mechanical and Structural Behaviour of Rubberized Recycled Aggregate Concrete
November 4 at 10:00 am - 2:00 pm
F M Zahid Hossain, supervised by Dr. Shahria Alam, will defend their dissertation titled “Mechanical and Structural Behaviour of Rubberized Recycled Aggregate Concrete” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering.
An abstract for F M Zahid Hossain’s dissertation is included below.
Examinations are open to all members of the campus community as well as the general public. Please email shahria.alam@ubc.ca to receive the Zoom link for this exam.
Abstract
This research investigates the effect of substituting recycled coarse aggregate (RCA) and scrap tire-derived crumb rubber (CR) as a partial replacement of coarse and fine aggregate along with polypropylene fibre (PPF) into the concrete mixture. The whole study was carried out encompassing several experiments with different setups to assess the applicability of these recycled materials. The main focus of the initial study was to observe the compressive strength, splitting tensile strength, and flexural response of rubberized concrete with RCA and PPF compared to natural aggregate concrete. Several experiments were carried out to investigate the bond strength of concrete with steel reinforcement having RCA, CR and PPF to find a way to minimize the use of natural resources. Further study was carried out to investigate the shear behaviour of concrete beams containing RCA, CR and PPF.
Initially, it was observed that properties such as compressive, splitting tensile, and flexural strength decrease as the CR content increases, but increase with increasing fibre content. With regard to toughness and ductility, the effect of fibre is greater than RCA and CR, with each being found to increase with its increment. It is noticed that both CR and PPF together reduce the bond strength of concrete but recycled aggregate concrete with either of the two materials increases the bond strength of concrete in certain combinations. In the shear test of beams, the introduction of CR in the concrete mix negatively affects the ultimate shear strength, post-diagonal cracking resistance, toughness, and deformability of the beam. The addition of PPF can overcome this effect in concrete at RCA replacement levels up to 30%. The beam made of 30% RCA along with 5% CR and 1% PPF demonstrated the best performance in terms of shear resistance, deformability, and toughness. The beam deformability increased with the addition of a small percentage of rubber (up to 5%). The post-diagonal crack resistance increased with the presence of fibre, whereas the response was the opposite with the addition of rubber.
As an outcome of the whole research, it is evident that the addition of up to 30% RCA, 5% CR and 2% PPF exhibit the best performance in terms of applicability of these recycled materials in concrete from mechanical and structural points of view.
