Impact of Chemically Treated Waste Rubber Tire Aggregates on Mechanical, Durability and Thermal Properties of Concrete

Yih Chen Khern,Vivi Anggraini,Branko Šavija,Adewumi John Babafemi,Suvash Chandra Paul,Sih Ying Kong,Md Jihad Miah

doi:10.3389/fmats.2020.00090

Abstract

Studies have shown that the incorporation of waste tire rubber aggregates reduces the strength, increases permeability and decrease thermal conductivity of concrete. However, only a few studies have investigated the effect of surface-modified rubber aggregates on the properties of concrete. This study investigates the effect of the surface treatment of waste tire rubber as coarse aggregates with different oxidizing solutions and different treatment durations on the mechanical, durability and thermal properties of concrete. The properties of concrete incorporated with 8% rubber coarse aggregates (by volume of natural aggregates) which were treated with three different solutions: water (H2O), 20% sodium hydroxide (NaOH) and 5% calcium hypochlorite [Ca(ClO)2] (both as% weight of water) for durations of 2, 24, and 72 h, respectively. The effect of these treatments on the compressive strength, splitting tensile strength, water permeability, thermal conductivity and diffusivity of concrete was investigated. Results show that Ca(ClO)2 has a more positive effect on the strength and permeability compared to NaOH solution and water. Experimental results were statistically analyzed using ANOVA and Post Hoc tests. The analyses showed that the improvement of concrete strength is only significant when the treatment with NaOH and Ca(ClO)2 is prolonged to 72 h. Furthermore, the microstructural analysis of concrete showed that the improvement in the strength is due to the improved bonding between cement paste and rubber aggregates as a result of surface treatment. This microstructural improvement also resulted in lower water permeability of concrete. However, the thermal conductivity and diffusivity increased when the surface treatment duration increases as there are less air voids in the samples. This study shows that, with appropriate pretreatment, a certain percentage of natural aggregates can be safely replaced with waste tire rubber aggregates while maintaining sufficient quality of the resulting concrete.

Highlights

Over the past few decades, the amount of waste tires generated globally has been increasing due to increasing population, leading to a rapid growth in automotive industry and use of vehicles
Based on the hypothesis that the improvement of the mechanical properties is related to the improvement of the interfacial transition zone (ITZ), this study focused on the influence of treatments and their durations on the resulting properties
It was decided that the optimal replacement percentage of coarse aggregates with rubber aggregates was around 8%, which resulted in 17% lower compressive strength compared to the reference mix

Summary

Introduction

Over the past few decades, the amount of waste tires generated globally has been increasing due to increasing population, leading to a rapid growth in automotive industry and use of vehicles. Rubber tires originate from motorcycles, automobiles, and trucks. To a certain extent these tires are suitable for recycling, most of them still end up in landfills. Huge amounts of waste tires are a cause of concern, as they are not bio-degradable, leading to their accumulation at landfills. Such landfills are a health and environmental hazard to surrounding communities. One of the possible solutions for disposal of waste tires is their use as (partial) replacement of natural aggregates in concrete production

Methods

Results

Conclusion