Ofori-Boadu, A N; Bryant, D; Bock-Hyeng, C; Assefa, Z; Aryeetey, F; Munkaila, S and Fini, E (2022) Physiochemical characterization of agricultural waste biochars for partial cement replacement. International Journal of Building Pathology and Adaptation, 40(4), pp. 569-586. ISSN 23984708
Abstract
Purpose: The purpose of this study is to explore the feasibility of utilizing agricultural (almond shell, rice husk and wood) waste biochars for partial cement replacement by evaluating the relationships between the physiochemical properties of biochars and the early-age characteristics of cement pastes. Design/methodology/approach: Biochars are prepared through the thermal decomposition of biomass in an inert atmosphere. Using varying percentages, biochars are used to replace ordinary Portland cement (OPC) in cement pastes at a water/binder ratio of 0.35. Characterization methods include XPS, FTIR, SEM, TGA, BET, Raman, loss-on-ignition, setting, compression and water absorption tests. Findings: Accelerated setting in biochar-modified cement pastes is attributed to chemical interactions between surface functional groups of biochars and calcium cations from OPC, leading to the early development of metal carboxylate and alkyne salts, alongside the typical calcium-silicate-hydrate (C-S-H). Also, metal chlorides such as calcium chlorides in biochars contribute to the accelerate setting in pastes. Lower compression strength and higher water absorption result from weakened microstructure due to poor C-S-H development as the high carbon content in biochars reduces water available for optimum C-S-H hydration. Amorphous silica contributes to strength development in pastes through pozzolanic interactions. With its optimal physiochemical properties, rice-husk biochars are best suited for cement replacement. Research limitations/implications: While biochar parent material properties have an impact on biochar properties, these are not investigated in this study. Additional investigations will be conducted in the future. Practical implications: Carbon/silicon ratio, oxygen/carbon ratio, alkali and alkaline metal content, chlorine content, carboxylic and alkyne surface functional groups and surface areas of biochars may be used to estimate biochar suitability for cement replacement. Biochars with chlorides and reactive functional groups such as C=C and COOH demonstrate potential for concrete accelerator applications. Such applications will speed up the construction of concrete structures and reduce overall construction time and related costs. Social implications: Reductions in OPC production and agricultural waste deterioration will slow down the progression of negative environmental and human health impacts. Also, agricultural, manufacturing and construction employment opportunities will improve the quality of life in agricultural communities. Originality/value: Empirical findings advance research and practice toward optimum utilization of biomass in cement-based materials.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | accelerator; additive; admixture; biomass; compression strength; concrete; construction; setting; sustainable; water absorption |
| Index terms: | investigation, estimate, interaction, metal, construction time, concrete structure, wood, employment, admixture, methodology, suitability, material property, deterioration, ordinary Portland cement, compression, human health, quality of life, cement replacement, water absorption |
| Subjects: | project controls, design criteria, behavioral psychology, management, structural engineering, public and environmental health, research methods, traditional and composite building materials, water management, material properties and characteristics, building materials, financial and cost management, material degradation and durability, data collection methods, materials science |
| Topics: | Human Resources, Design Practice, Time Control, Research Practice, Engineering Principles, Construction Materials, Cost Management, Health and Safety, Sustainability |
| Descriptive scope: | 4 PCTA |
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