Algal biomass particle size and self-bonding effects on cement composites

Abstract

Cement is a large contributor to carbon dioxide (CO2) emissions, and there is ongoing research to reduce this impact. Algal biomass, in various forms, is studied for potential applications in many industrial industries including the cement industry. This is large in part due to the wide availability of the abundant organic biomass in coastal marine regions. Prior literature has seen Arthrospira (Spirulina) platensis microalgae integrated with Ordinary Portland cement (OPC). This work explores the incorporation of raw and self- bonded algal biomatter to see the impact on the cement composites. The known effect of particle size is also further studied. We respectively incorporate microalgae (Arthrospira platensis) spirulina and macroalgae (Ulva expensa) in OPC at concentrations of 1%, 5%, and 10%. This is completed at three distinct particle size ranges as well as for raw and self- bonded biomass. We observe their effects on the mechanical strength, hydration product formation, and micromorphology of the composites through compression testing, thermogravimetric analysis and scanning electron microscopy, respectively. Spirulina microalgae composites performed as expected with a drastic reduction in compressive strength at 5% concentration while ulva macroalgae experiences a decrease in performance with increasing concentration, but the effect is not significant until 10% and is less dramatic than what is observed in the spirulina. Smaller particle sizes in the ulva composites are on average 1.49 times stronger than their large particle size counterparts, this factor is similar in spirulina but again at relatively much lower strengths. Self-bonding has the opposite effects on the microalgae and macroalgae systems, where self-bonding enhances the strength of ulva-cement composites up to 224%. This work furthers the investigation of whole algal biomass as additions to cement, with the intention of finding methods to reduce the detrimental environmental impact associated with cement production.