Dissertation Defence: Wood ash modified low-carbon cementitious composites and concrete
April 14 at 9:00 am - 1:00 pm
Rubaiya Rumman, supervised by Dr. Shahria Alam, will defend their dissertation titled “Wood ash modified low-carbon cementitious composites and concrete” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering.
An abstract for Rubaiya Rumman’s dissertation is included below.
Examinations are open to all members of the campus community as well as the general public. Please email shahria.alam@ubc.ca to receive the Zoom link for this exam.
Abstract
Concrete is a major emitter of CO2, with cement as the most significant contributor. Different supplementary cementitious materials (SCM) are used in concrete to reduce its carbon footprint. Coal fly ash (CFA), a byproduct of coal-fired power plants, has been used as an SCM in the cement and concrete industries. However, with the recent closure of coal power plants, CFA production has declined, with the possibility of its complete unavailability in the near future.
In search of a possible alternative to CFA, experimental investigations were conducted on wood fly ash (WFA), a byproduct of clean bioenergy production, to determine whether it exhibits pozzolanic activity. Characterization tests and microstructural analysis were conducted on the WFA, and the reactivity of WFA-based cement pastes was observed using two types of WFA sourced from different regions in Canada. The results were also compared with the commercially available classes C and F CFA. The WFA obtained from a local timber manufacturing industry in British Columbia performed similarly with the commercial class C CFA. Moreover, WFA was added to carbon nanotube-modified strain sensors to investigate its effect on the rheological, electrical, and mechanical properties of the composites. The results showed promising potential to improve the materials’ conductivity and reduce the carbon footprint of self-sensing cementitious composites.
The lab-scale research on WFA-modified concrete was then scaled up to field application, where real-life slabs and lock blocks were prepared after concrete was mixed at a ready-mix company’s batch plant. The specimens have been continuously monitored to observe the effect of the weather on them. The WFA exhibited comparable mechanical and durability performance in mortar and concrete at a 15% replacement of the cement content. There was a decrease in the mechanical and durability performance of WFA-based concrete at higher percentage levels, such as 30%. To gain a holistic view of the performance of WFA-modified cementitious composites, a life-cycle assessment was conducted on the specimens using the cradle-to-gate approach. This thesis highlights some of the beneficial impacts of WFA as an SCM, and the potential to utilize the benefits in large-scale applications and self-sensing cementitious composites.
