Utilization of Crumb Rubber and High-Volume Fly Ash in Concrete for Environmental Sustainability: RSM-Based Modeling and Optimization.

Mugineysh Murali,Bashar S Mohammed,M S Liew,Isyaka Abdulkadir,Wesam Salah Alaloul

doi:10.3390/ma14123322

Mugineysh Murali, Bashar S Mohammed + Show 3 more

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https://doi.org/10.3390/ma14123322

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Abstract

Waste tire and fly ash (FA) are two waste materials whose disposal and rapid rate of accumulation are among the pressing sources of concern and threat to the environment. Although much research exists on the use of these materials in cementitious composites, very little literature is available on the effectiveness of combining them in high volumes for concrete production. This work aimed to utilize crumb rubber (CR) from waste tires as a partial replacement of fine aggregate at 15%, 22.25%, and 30% by volume, and high-volume fly ash (HVFA) replacement of cement at 50%, 60%, and 70% (by weight of cementitious materials) to produce high-volume fly ash–crumb rubber concrete (HVFA–CRC). Using the central composite design (CCD) option of the response surface methodology (RSM), 13 mixes were produced with different combinations and levels of the CR and FA (the input factors) on which the responses of interest (compressive, flexural, and tensile strengths) were experimentally investigated. Furthermore, the composite influence of CR and HVFA on the workability of the concrete was assessed using the slump test. The results showed a decline in the mechanical properties with increasing replacement levels of the CR and HVFA. However, up to 22.25% and 60% of CR and HVFA replacements, respectively, produced a structural HVFA–CRC with a compressive strength of more than 20 MPa at 28 days. Response predictive models were developed and validated using ANOVA at a 95% confidence level. The models had high R2 values ranging from 95.26 to 97.74%. Multi-objective optimization was performed and validated with less than 5% error between the predicted and experimental responses.

Highlights

To achieve the noble aim of environmental sustainability, governments and other relevant organizations are increasingly focused on finding more efficient ways of curtailing the depletion and degradation of natural resources
This research aimed to assess the properties of a green high-volume fly ash (HVFA)–CRC that was produced using a high amount of waste materials (CR and fly ash (FA)) for environmental sustainability and cost reduction
The following conclusions were drawn at the end of the research: 1. An increase in the slump by 80–200% was observed by mixes having 50–70% HVFA content at the same crumb rubber (CR) content

Summary

Introduction

To achieve the noble aim of environmental sustainability, governments and other relevant organizations are increasingly focused on finding more efficient ways of curtailing the depletion and degradation of natural resources One such measure is controlling the amount of waste generation and disposal. The world is experiencing a rapid increase in automobile production to cope with the rising population and transportation needs [1] This leads to the rise in waste tire generation at a rate that far exceeds its recycling and reuse. It is against this backdrop that researchers investigate CR as a replacement for fine aggregate in concrete This practice has a double advantage for the environment due to solving the waste disposal challenge and natural aggregate depletion [4]. The use of CR in concrete enhances the deformation capacity, impact resistance, energy absorption, resistance to cyclic freezing and thawing, decrease in water absorption, and chloride permeability [2,3,4,5,6]

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