Optimal Mixture Design of Low-CO2 High-Volume Slag Concrete Considering Climate Change and CO2 Uptake

Han-Seung Lee,Xiao-Yong Wang,Seung-Min Lim

doi:10.1186/s40069-019-0359-7

Abstract

High-volume slag (HVS) can reduce the CO2 emissions of concrete, but increase the carbonation depth of concrete. In particular, because of the effects of climate change, carbonation will accelerate. However, the uptake of CO2 as a result of carbonation can mitigate the harm of CO2 emissions. This study proposes an optimal mixture design method of low-CO2 HVS concrete considering climate change, carbonation, and CO2 uptake. Firstly, net CO2 emissions are calculated by subtracting the CO2 emitted by the material from the uptake of CO2 by carbonation. The strength and depth of carbonation are evaluated by a comprehensive model based on hydration. Secondly, a genetic algorithm (GA) is used to find the optimal mixture. The objective function of the GA is net CO2 emissions. The constraints of the GA include the strength, carbonation, workability, and range of concrete components. Thirdly, the results show that carbonation durability is a control factor of the mixture design of low-strength HVS concrete, while strength is a control factor of the mixture design of high-strength HVS concrete. After considering climate change, the threshold of strength control increases. With the increase of strength, the net CO2 emissions increase, while the CO2 uptake ratio decreases.

Highlights

Slag is a byproduct from iron- or steelmaking industry and is widely used to produce sustainable concrete
This study proposes a mixed design method of lowCO2 high-volume slag (HVS) concrete that considers climate change, carbonation, and C O2 uptake caused by carbonation
The net C O2 emissions are equal to the CO2 emissions of the material minus the C O2 uptake caused by carbonation

Summary

Introduction

Slag is a byproduct from iron- or steelmaking industry and is widely used to produce sustainable concrete. Lee et al Int J Concr Struct Mater (2019) 13:56 for concrete with different strengths They found that the raw material stage accounted for more than 90% of the greenhouse gas emissions. Kim et al (2016) proposed an evolution algorithm to produce concrete with minimum CO2 emissions or cost. Based on the optimization method, 34% of CO2 emissions can be reduced compared to the standard concrete production process. It should be recognized that methods in some references (Kim et al 2016; Park et al 2013; Yang et al 2015; Yepes et al 2015) show some weak points regarding the mixture design of HVS concrete. This study proposes a mixed design method of lowCO2 HVS concrete that considers climate change, carbonation, and C O2 uptake caused by carbonation. The influence of the design strength level and climate change scenario on the mixture design was evaluated

Formulation for the Optimization of Concrete Mixing Proportions

Object Function

Findings

Conclusions