Open Access

ARTICLE

CO₂ and Cost-Based Optimum Design of Sustainable Metakaolin-Modified Concrete

Xiaoyong Wang^*

Department of Architectural Engineering, Department of Integrated Energy and Infra System, Kangwon National University, Chuncheon-si, 24341, Korea

* Corresponding Author: Xiaoyong Wang. Email:

(This article belongs to the Special Issue: Sustainable Concrete with Recyclable Materials)

Journal of Renewable Materials 2022, 10(9), 2431-2450. https://doi.org/10.32604/jrm.2022.020829

Received 15 December 2021; Accepted 14 February 2022; Issue published 30 May 2022

Abstract

Metakaolin is a highly reactive pozzolanic material that is widely utilized for enhancing the performance of concrete. This study offers a framework for the mixture design of sustainable metakaolin-modified concrete with low CO₂ emissions and low costs. Different design strengths after 28 days are first formulated, with values such as 30, 40, 50, and 60 MPa. A genetic algorithm is then used to determine the optimal mixtures. Minimized CO₂ and cost are set as the aims of the genetic algorithm. The strength of the concrete, its workability (slump), and carbonation service life with climate change are set as constraints of the genetic algorithm. Five design cases are considered: 1) low-CO₂ concrete with no carbonation, 2) low-CO₂ concrete with carbonation, 3) low-material cost concrete with carbonation, 4) low-total cost concrete with carbonation, and 5) low-total cost concrete with climate change. Based on the analysis, the following results are found: 1) When the design’s strength is 30 MPa, to satisfy the requirement of carbonation durability, the concrete real strength should exceed 30 MPa. Moreover, after considering climate change, the concrete real strength should be further improved. 2) When the design strength is 40, 50, or 60 MPa for low-total-cost concrete, climate change has no impact on the optimal design because the concrete has sufficient carbonation resistance. 3) Low-material-cost concrete has the same mixture as low-total-cost concrete because compared with the material cost, the CO₂ emission cost is much lower. Moreover, for low-material-cost or low-total-cost concrete, the metakaolin content is at the lower limit because the price of metakaolin is much higher than that of cement. Summarily, the proposed model covered different aspects of sustainable concrete, such as cost and CO₂ emissions, clarified various decisive factors of mix design, such as strength and carbon durability, and considered different conditions of climate change, such as no climate change and Representative Concentration Pathways (RCP)8.5. The proposed method is valuable for designing sustainable metakaolin-modified concrete with low CO₂ emissions and costs.

---

Keywords

---