Effect of Carbon Pricing on Optimal Mix Design of Sustainable High-Strength Concrete

Xiao-Yong Wang

doi:10.3390/su11205827

Abstract

Material cost and CO2 emissions are among the vital issues related to the sustainability of high-strength concrete. This research proposes a calculation procedure for the mix design of silica fume-blended high-strength concrete with an optimal total cost considering various carbon pricings. First, the material cost and CO2 emission cost are determined using concrete mixture and unit prices. Gene expression programming (GEP) is used to evaluate concrete mechanical and workability properties. Second, a genetic algorithm (GA) is used to search the optimal mixture, considering various constraints, such as design compressive strength constraint, design workability constraint, range constraints, ratio constraints, and concrete volume constraint. The optimization objective of the GA is the sum of the material cost and the cost of CO2 emissions. Third, illustrative examples are shown for designing various kinds of concrete. Five strength levels (from 95 to 115 MPa with steps of 5 MPa) and four carbon pricings (normal carbon pricing, zero carbon pricing, five-fold carbon pricings, and ten-fold carbon pricings) are considered. A total of 20 optimal mixtures are calculated. The optimal mixtures were found the same for the cases of normal CO2 pricing and zero CO2 pricing. Optimal mixtures with higher strengths are more sensitive to variation in carbon pricing. For five-fold CO2 pricing, the cement content of mixtures with higher strengths (105, 110, and 115 MPa) are lower than those of normal CO2 pricing. As the CO2 pricing increases from five-fold to ten-fold, for mixtures with a strength of 110 MPa, the cement content becomes lower. Summarily, the proposed method can be applied to the material design of sustainable high-strength concrete with low material cost and CO2 emissions.

Highlights

To achieve the aim of sustainable development of the modern concrete industry, construction companies and concrete factories are making every effort to lower the material cost and CO2 emissions from concrete production
The w/b ratio, silica-fume-replacement ratio, water content, and sand ratio are set as independent variables of Gene expression programming (GEP), and strength is set as a dependent variable of GEP
Gene expression programming is used to evaluate the slump of silica fume-blended concrete

Summary

Introduction

To achieve the aim of sustainable development of the modern concrete industry, construction companies and concrete factories are making every effort to lower the material cost and CO2 emissions from concrete production. High-strength concrete shows various advantages, such as reducing the size of the structural element, increasing the used space of a building, and extending the service life. Both construction companies and investors are interested in making high-strength concrete with lower material cost and CO2 emissions [1,2]. Sharma and Khan [5] reported that for producing self-consolidating concrete, replacing sand with copper slag can reduce cost, save embodied energy, and reduce CO2 emissions. Hassan and Kianmehr [6] showed that for producing pavement concrete, incorporating previous concrete combined with slag can lower cost, reduce the heat island effect and embodied energy, and offer a decrease in CO2 emissions. Based on comparisons of CO2 emissions and compressive strength, Lin et al [9] found that an environmental benefit can be achieved when quartz is used in concrete with low water-to-binder (w/b) ratios

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Conclusion