CO2 adsorption and mechanical performance of cement mortars incorporating coconut-shell-derived activated carbon

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Article

Publication Date

10-1-2026

Abstract

Activated carbon (AC) derived from biomass has attracted increasing attention as a functional additive for developing cement-based materials with enhanced CO2 uptake. In this study, coconut-shell-derived AC was incorporated into a commercial dry premixed plaster mortar at replacement levels of 0–10 wt% to investigate the relationships among fresh-state behavior, mechanical and physical properties, and composite-level CO2 uptake. A constant-workability design was employed, with the mixing-water content adjusted to maintain a target flow range of 105 ± 5%. Under these conditions, mixtures containing 1–5 wt% AC exhibited higher 28-day compressive strengths than the control, reaching a maximum of 7.45 MPa for AC3 compared with 5.67 MPa for the control, together with higher bulk density and lower water absorption. In contrast, AC10 exhibited lower compressive strength and markedly higher water absorption. At 30 °C and 1.03 bar, the measured composite-level CO2 uptake increased from 0.62 mmol g−1 for the control to 1.07 mmol g−1 for AC5, while AC10 showed a similar uptake of 1.05 mmol g−1. After 308 days of ambient curing, no statistically significant differences in compressive strength relative to the 28-day values were detected for the control and AC1–AC5 mixtures, whereas AC10 exhibited a statistically significant reduction. Thermogravimetric analysis of the 308-day specimens showed AC-dose-dependent high-temperature mass-loss behavior. Based on a criterion combining mechanical acceptability with the highest measured composite-level CO2 uptake, AC5 was identified as the optimum among the dosages investigated. These results demonstrate the potential of coconut-shell-derived AC as a functional additive for cementitious materials with measurable CO2 uptake while maintaining mechanical performance at moderate incorporation levels.

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