# Synergistic Effect of Waste Glass Powder and Metakaolin on the Microstructure and Mechanical Performance of Cement-Based Pastes and Mortars

## TL;DR

Combining waste glass powder and metakaolin improves the strength and durability of cement-based materials over time, supporting sustainable construction.

## Contribution

The synergistic effect of waste glass powder and metakaolin on cement microstructure and mechanical performance is demonstrated.

## Key findings

- MK boosts early strength, while WGP improves long-term performance and pore refinement.
- Binary and ternary systems show reduced pore volume and water absorption with curing.
- Ternary mortars significantly decrease porosity and absorption from 28 to 60 days.

## Abstract

MK and WGP act synergistically, improving strength and pore structure over time.

Gas adsorption reveals reduced accessible pore volume in binary and ternary pastes.

WGP–MK mortars exhibit lower water absorption and porosity at later curing ages.

Ternary mortar porosity and absorption decrease significantly from 28 to 60 days.

Combined WGP–MK systems enable clinker replacement for a circular economy.

The incorporation of supplementary cementitious materials (SCMs) is a key strategy for enhancing the performance and sustainability of cement-based systems. This research examines the mechanical behavior, microstructural evolution, and durability-related properties of cementitious materials incorporating waste glass powder (WGP) and metakaolin (MK) as partial replacements of Portland cement. Cement pastes were evaluated for compressive strength at 7 and 28 days, while microstructural analysis at 28 days employed gas adsorption and scanning electron microscopy (SEM). Based on the compressive strength performance of the cement pastes, ternary WGP–MK mortars were assessed for consistency, flexural and compressive strength, water absorption, and porosity at 28 and 60 days. Results indicate that MK accelerates early-age strength, whereas WGP enhances long-term performance and pore structure refinement. Binary and ternary systems exhibited reduced accessible pore volume, enhanced microstructural homogeneity, and lower water absorption with curing time. The findings demonstrate that WGP-MK blends support clinker reduction without compromising performance, advancing circular economy goals in construction.