# Influence of Multi-Walled Carbon Nanotubes on the Mechanical and Deformation Performance of Polymer-Modified Crumb Rubber Concrete

## TL;DR

This study explores how adding carbon nanotubes improves the strength and flexibility of concrete mixed with recycled rubber from old tires.

## Contribution

The novel use of multi-walled carbon nanotubes in polymer-modified crumb rubber concrete to enhance mechanical properties is investigated.

## Key findings

- Adding 0.05% MWCNTs and 1% CR increased compressive, flexural, and tensile strength by 14.12%, 11%, and 13.68%, respectively.
- RSM models predicted mechanical properties with 95% reliability.
- Optimal performance was observed with 0.05% to 0.065% MWCNTs and 2% CR.

## Abstract

Crumb rubber (CR), a recycled elastomeric polymer derived from scrap tyres, has been used as a partial replacement for fine aggregates in concrete to manage non-biodegradable waste tyre piling, which fills landfills and harms the environment. Polymer-modified rubber improves the concrete’s flexibility, toughness, and impact resistance, but reduces its strength and modulus of elasticity. Multi-walled carbon nanotubes (MWCNTs) are being used to mitigate these issues. The purpose of this study is to investigate the impact of CR% (1% to 5%) as a partial replacement for sand by volume and MWCNTs (at a percentage of 0.05% to 0.08%) as additives by weight of cement as input parameters for determining the mechanical strength (compressive, tensile, and flexural) and deformation properties (modulus of elasticity and Poisson’s ratio) of MWCNT- and polymer-modified CR concrete using response surface methodology (RSM). The results show that 0.05% MWCNT and 1% CR content led to increases in compressive strength, flexural strength, and tensile strength by 14.12%, 11%, and 13.68%, respectively. In addition, models to predict those properties have been developed using RSM with a 95% reliability level. It has been observed that the notable development in the mechanical characteristics of CR concrete with the accumulation of MWCNTs and the models constructed using RSM were deemed satisfactory, with a variation of 0.05% to 0.065% of MWCNTs along with 2% CR.