Algae-Enhanced Sustainable Construction Mortar

Abstract

The present investigation evaluates the feasibility of developing sustainable cementitious mortar by partially replacing ordinary Portland cement with a ternary eco-additive system consisting of microalgae biomass, fly ash, and MEL furnace slag. The motivation behind this research arises from the urgent requirement to reduce carbon emissions associated with cement production while simultaneously valorizing industrial and biological waste streams. Microalgae biomass contains calcium, silica, and bio-organic compounds that can act as nucleation sites and internal curing agents, whereas fly ash and furnace slag exhibit well-known pozzolanic and latent hydraulic behavior. The combined action of these materials is expected to enhance mechanical performance and durability while lowering environmental impact.

Mortar mixes were prepared with varying replacement percentages (0–40%) of cement using algae powder, fly ash, and MEL furnace slag in different proportions. Fresh properties including flowability and water demand were assessed, followed by hardened properties such as compressive strength, flexural strength, density, and water absorption. Microstructural characteristics were interpreted based on hydration kinetics and bio-mineralization mechanisms. The study also evaluated durability behavior through sorptivity and permeability tests. Results demonstrated that the ternary system improves long-term strength and reduces pore connectivity due to secondary calcium silicate hydrate formation and bio-precipitation effects. The optimum performance was observed at 25–30% cement replacement where compressive strength exceeded the control mix after 28 and 56 days curing.

The study confirms that algae-based mortar can function not only as a structural material but also as a carbon-sequestering composite due to biological mineralization. Fly ash contributes to delayed hydration strength while MEL furnace slag enhances early-age reaction. The integrated effect produces dense microstructure and improved durability characteristics. The research establishes the potential for producing low-carbon mortar suitable for masonry, plastering, and non-load-bearing structural components. This experimental investigation supports the development of circular construction materials and demonstrates a pathway for combining biological and industrial wastes into value-added construction products.