Date of Award

Spring 5-31-2019

Level of Access

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Warda Ashraf

Second Committee Member

Eric N Landis

Third Committee Member

Roberto A Lopez Anido

Abstract

Wood ash is a byproduct from biomass power plants. Most of the wood ash is currently being disposed of as landfilling material that causes severe economic and environmental concerns. This project focuses on the feasibility of using this wood ash in construction materials. Wood ash was found to contain varieties of mineral phases including calcium carbonate, calcium aluminate, and quartz. Based on the chemical composition, the efficacy of wood ash (i) as supplementary cementitious materials (SCM), (ii) in the controlled low strength materials (CLSM) production and (iii) Portland cement production was evaluated.

Wood ash with adequate pozzolanic properties can be used as supplementary cementitious materials (SCM) in concrete production. In practice, coal fly ash, slag, and silica fume are commonly used SCM in concrete and these materials positively contribute to the concrete strength and durability at later ages via pozzolanic reaction. Controlled low strength materials (CLSM) are typically produced with high coal fly ash content, low cement content, water and aggregates, and the strength are attained via pozzolanic reaction. Because of the probable pozzolanic properties, wood ash can partially or fully replace fly ash in the production of controlled low strength materials (CLSM). Production of Ordinary Portland Cement (OPC) requires 60 to 70% of CaO phases and generally, it is supplied by using limestone (CaCO3) phases. The significant amount of calcium carbonate phase present in wood ash makes it a potential material to be used as a raw material for cement production.

For SCM, the test results illustrated that the workability of wood ash blended samples are found to reduce as the replacement level is increased, this is because of the presence of metallic alumina. The replacement of wood ash in both ground and sieved form is studied because of the presence of less fine particles. The ground samples are noted to give better strength than that of the sieved ones. The samples with ground wood ash are found to have hydraulic properties. The ground wood ash can replace cement up to 30% and sieved wood ash can replace cement up to 20% in mortar samples without any significant effect on compressive strength. In the CLSM production, the wood ash can replace fly ash by 100 percent without any decrease in the target strength. The cement clinker produced using wood ash as a raw material is found to have a higher reaction rate than that of Ordinary Portland Cement (OPC). The wood ash cement clinker is found to have a very similar chemical composition as that of an ordinary Portland cement clinker.

Available for download on Sunday, April 26, 2020

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