Bio-Based Admixture (Black Tea Extraction) for Better Performance of Metakaolin Blended Cement Mortars

Area of Science:

• Materials Science
• Civil Engineering
• Green Chemistry

Background:

• Metakaolin (MK) is a reactive supplementary cementitious material (SCM) used in concrete.
• MK's small particle size can cause agglomeration, leading to poor concrete performance.
• Traditional chemical admixtures for dispersion have environmental drawbacks.

Purpose of the Study:

• To investigate black tea extract (BTE) as a sustainable, bio-based admixture for MK blended cement mortars.
• To evaluate BTE's effect on dispersion, workability, and microstructure.
• To assess the mechanical properties and environmental impact of BTE-modified mortars.

Main Methods:

• Incorporation of black tea extract (BTE) into metakaolin (MK) blended cement mortars.
• Experimental analysis of workability and rheological properties.
• Microstructural characterization using porosity and pore size distribution analysis.
• Mechanical testing, including compressive strength at 28 days.
• Economic and environmental assessment (cost-benefit, embodied carbon, eco-efficiency).

Main Results:

• BTE significantly improved the workability of MK blended cement mortars.
• Reduced pore size (<50 nm) and total porosity in hardened pastes.
• Substantial improvements in micro- and macro-mechanical properties.
• Achieved up to 35% greater compressive strength at 28 days compared to controls.
• Demonstrated economic and environmental advantages of BTE.

Conclusions:

• Black tea extract (BTE) is an effective bio-admixture for enhancing metakaolin (MK) blended cement mortars.
• BTE improves dispersion, workability, and microstructure, leading to superior mechanical performance.
• The use of BTE offers a sustainable and cost-effective alternative to petroleum-based admixtures, with positive environmental implications.