Cleaner Materials (Dec 2022)

Generating response surface models for optimisation of CO2 emission and properties of concrete modified with waste materials

  • David Sinkhonde

Journal volume & issue
Vol. 6
p. 100146

Abstract

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Using waste materials in concrete plays a vital role in sustainable construction, so much that it can conserve the environment and improve concrete properties. Waste management and sustainable construction are critical challenges in construction sector. Production of Ordinary Portland Cement (OPC) has also proved to be a contributor to CO2 emissions. Although various studies have concentrated on conserving the environment, limited studies have focused on generating response surface models to optimise CO2 emission and concrete properties using waste clay brick powder (WCBP) and waste tire rubber (WTR). This paper develops models appropriate in generating best compromises among responses of CO2 emissions and dry concrete density. Central composite design (CCD) based on response surface methodology (RSM) was employed to assess the effect of replacement parameters of WCBP (0 – 5%) and WTR (0 – 20%) on CO2 emissions, wet density and dry density. The accuracy of the generated models was checked using analysis of variance (ANOVA). The regression equations from RSM showed high R2 values of greater than 0.8 for all responses and this proved that the generated models were able to explain variability in the responses. The CO2 emission, wet density and dry density responses were noticed to vary linearly with the replacement levels of WCBP and WTR. Optimum conditions using desirability analysis were found with the highest replacements of cement with WCBP (5%) and no replacements of coarse aggregate with WTR (0%). The relationship between CO2 emission and 28-days compressive strength demonstrated no significant trend as the compressive strength increased. Based on the findings, it was concluded that thanks to RSM, CO2 emissions could be reduced through inclusion of waste materials in concrete without significantly affecting properties of concrete.

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