Carbonation treatment of eggshell powder concrete for performance enhancement

Abstract

A large amount of eggshell waste is produced annually worldwide. Proper disposal of waste eggshell powder is crucial for reducing environmental pollution and achieving sustainable development. In this study, eggshell powder was added to the cement system, and the macroscopic and microscopic properties were evaluated under sealed- and carbonation-curing conditions. The dilution effect of eggshell powder dominated under sealed-curing conditions, causing a decrease in compressive strength, ultrasonic pulse velocity, and electrical resistivity with an increase in eggshell powder addition. Under carbonation-curing conditions, the addition of eggshell powder increased the carbonation efficiency of the mixing system, improved the carbon capture capacity (CO2 uptake was 33% with 30% eggshell powder addition), increased the normalized compressive strength of the samples, and reduced the degree of compressive strength loss. The reaction of the calcium silicate hydrate (C-S-H) gel, calcium hydroxide (CH), ettringite (AFt), monosulphate (AFm), and unhydrated cement with CO2 during carbonation curing formed a large amount of CaCO3, which enabled the formation of a dense internal structure and increased the reactivity of C2S. Therefore, addition of eggshell powder to cement matrix under carbonation-curing conditions promotes sustainability, enhances mechanical properties, and improves durability effects, and provides a feasible strategy for the treatment of agricultural waste eggshell powder.