Carbon capture performance and properties of cementitious material with local waste biochar / Priscilla Gunn Fong Ern

Priscilla Gunn , Fong Ern (2024) Carbon capture performance and properties of cementitious material with local waste biochar / Priscilla Gunn Fong Ern. Masters thesis, Universiti Malaya.

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Abstract

Considerable attention has been devoted to investigating the viability of utilizing sustainable alternatives derived from agricultural waste to partially replace cement in the construction industry. The shift to alternatives is primarily driven by the significant pollution generated by the industries over the years. Malaysia is known for its extensive plantations of various crops, which is a significant contribution to the economy of the country. The crop plantation in Malaysia produced a large amount of waste, posing challenges in waste utilization and disposal. The waste may be valorized by converting into biochar and incorporating into cement concrete products. Biochar is known for its potential in carbon sequestration, making it a prominent subject of study for environmental benefits. Four types of biochar were obtained and studied for its characterization, properties and carbon sequestration potential. These four types of biochar include rice husk biochar (RHB), palm kernel shell biochar (PKS), coconut husk biochar (CHB), and bamboo biochar (BB) Upon characterization of the biochar, RHB and PKS which had the best carbon sequestration ability were selected for more comprehensive investigation in cement mortar. This study presents experimental investigations on high dosage of locally produced RHB and PKS as cement replacement, specifically at 10, 20, 30 and 40% by volume. The incorporation of biochar as a partial replacement in cementitious material presents a means to mitigate the adverse effect of carbon dioxide (CO2) emissions resulting from cement production. Comprehensive assessments were done to study the porosity, strength, microstructure, and thermal characterization of the PKS and RHB-added mortar composites as an initial phase to develop eco-friendly concretes. All these efforts were undertaken with the aim of maximizing waste valorization and carbon uptake of the produced mortars. The incorporation of biochar caused a change in porosity of the matrix, which is favorable for carbon sequestration. The porosity of the mortar increased by 52.9% after the integration of biochar. The experiment also focuses on enhancing the carbon sequestration ability of biochar-added cement composite through carbonation curing. Qualitative and quantitative carbonation tests were carried out to determine the carbonation rate of the RHB and PKS-added mortar. The addition of biochar has been shown to facilitate the carbonation process, as evidenced by the increase in carbonation depth and degree of carbonation. PKS-added mortars had a higher CO2 uptake compared to RHB-added mortars. Saturated PKS-added mortar demonstrated the highest CO2 uptake of 24.8% (i.e. 248 gCO2/kg PKS-added mortar), greater than unsaturated PKS-added mortar. Besides, the carbonated mortars exhibited higher strength than the water-cured mortars, resolving the strength issue with higher biochar addition. The improvement in strength due to carbonation curing ranges from 26.7 – 87.0%. Overall, the optimum replacement of PKS at 30% by volume contributes to higher carbon uptake and an improved strength in cement mortar through carbonation curing. The findings evaluated the potential of biochar to be effectively used as an additive in cement mortar. Biochar not only reduces environmental impact, but also has the capability to sequester a significant amount of carbon in civil infrastructure.

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