Role of recycled vehicle tires quantity and size on the properties of metakaolin-based geopolymer rubberized concrete

Increasing demand for concrete construction and the consequent increase in the production of conventional Portland cement is thwarting efforts towards sustainable construction practices. This is seen in the carbon dioxide footprint caused by cement manufacturing as well as natural resources consumption. Therefore, the so-called geopolymer or alkali-activated composites using byproduct or natural materials are seen as a potential substitute for cement-based binders. Similarly, recycled rubber recovered from shredded tires has been used in concrete mixes, which in addition to the environmental benefit, offers desirable properties, e.g., improved deformability and energy dissipation capacity. Therefore, this paper investigates the influence of introducing recycled rubber in metakaolin-based geopolymer mixes on the workability, compressive behavior (stress-strain components and failure mode), flexural strength, unit weight, air content, and water absorption percentage. Seven mixes were employed for this purpose with two main variables comprising rubber size (fine, coarse, or combination of both) and replacement percentage (0%, 20%, and 40%). Recycled rubber was observed to reduce the mix workability by 4%-52.5% and 40%-62.5% when fine or coarse rubber particles were added to concrete mixes, respectively. Average compressive strength of 14.3-37.7 MPa was achieved when fine and/or coarse rubber particles replaced 20% or 40% of the conventional fine and/or coarse aggregates. Furthermore, rubberized geopolymer concrete showed more deform ability than plain mixes coupled with lightweight characteristics, which are desirable in many construction applications. This indicates the suitability of the rubberized geopolymer concrete for developing low to moderate-strength concrete for non-structural and structural applications. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The increasing demand for high-strength concrete construction has led to concerns over the carbon dioxide emissions and resource consumption caused by the production of conventional cement. This study explores the potential use of geopolymer or alkali-activated composites and recycled rubber as alternatives to cement-based binders. The results show that introducing recycled rubber into metakaolin-based geopolymer mixes can enhance the workability, flexural strength, and compressive strength of the concrete, making it suitable for non-structural and structural applications in construction.