Tanvir Imtiaz

ORCID Identifier(s)

0000-0002-0764-2925

Graduation Semester and Year

2021

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering

Department

Civil Engineering

First Advisor

Sahadat MD Hossain

Second Advisor

Warda Ashraf

Abstract

A large percentage of waste materials is recycled back into the same product from which they originated. In spite of considerable progress in recycling waste materials generated in urban environments, the materials are sometimes not able to be recycled into the same product due to their quality or technical requirements and are as a result dumped or incinerated. Recycling concrete aggregate (RCCA) and recycled waste plastics are examples of recycled materials that can be used as an alternative to natural aggregates during the construction of newer structures as well as demolition of existing structures like buildings, bridges, and pavements. Materials that are recycled can reduce the cost, depletion of natural resources, and construction debris. Recycling materials have different properties depending on their source, which limits their utility to a great extent. This experimental program evaluated the strength, stiffness, durability, and environmental impacts of pavement bases made from recycled materials on the basis of these factors. Using recycled plastics and RCCA materials, this study was carried out to determine if there is a correlation between resilient modulus and different strengths. We developed an experimental program for the determination of resilient modulus ($M_R$), unconfined compressive strength (UCS), elastic modulus (EM), cement content (CC) and plastic content (PC). In order to understand the internal bonding of these materials at the micro-scale, we also performed a microstructure image analysis program. Three types of recycled plastic were utilized -- High density polyethylene (HDPE), polypropylene (PP), and polyethylene terephtha-late (PET) -- mixed with RCCA to test the applicability of these materials for use in flexible pavement base layers. According to the study, 3 to 5 percent recycled shredded plastic can be mixed with RCCA, but it must be treated with 6 to 8 percent cement to achieve the 300 psi compressive strength specified by the Texas Department of Transportation. The value of unconfined compressive strength and resilient modulus increases with an increase in cement content. In the image analysis of the specimens of three different types of plastics and cement paste, the differences in compressive strength are revealed among the plastic-RCCA-cement mixtures. Among the three types of plastic, HDPE-RCCA-cement had the highest compressive strength, followed by PP and PET. In pavement design, the most important stiffness parameter is the resilient modulus. However, the resilient modulus test is too complicated and costly to conduct regularly. However, unconfined compressive strength tests are easier to perform. Hence, in order to determine the value of the resilient modulus (MR) for different combinations of recycled materials, MLR models were developed using the unconfined compressive strength (UCS), the elastic modulus (EM), and the cement content (CC) and plastic content (PC). Then again various combinations of recycled materials failed to meet the minimum requirement, but these can be used for sub-base layer where the strength requirement is low. This experimental research can be not only a solution to the worldwide waste plastic disposal problem but also can help reducing the depletion of natural resources. 5 million plastic bottles can be disposed in a typical one mile of pavement construction if we replace only 3 percent of flex-base material. The number will rise up to 9 million plastic bottles if we use 5 percent shredded plastic in flexible pavement base.

Keywords

Recycled plastic, Recycled crushed concrete, Recycled material, Pavement, Pavement base, Pavement subbase, Cement treated base

Disciplines

Civil and Environmental Engineering | Civil Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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