Lightweight, Heat-Insulating, Alkali-Activated Slag Composites with Carbon-Based Biochar Additive and Filler

Area of Science:

• Materials Science
• Green Chemistry
• Construction Materials

Background:

• Alkali-activated slag binders offer sustainable alternatives to Portland cement.
• Biochar waste (BW), derived from waste wood, presents an opportunity for valorization in construction materials.

Purpose of the Study:

• To investigate the effect of biochar waste (BW) as an additive and filler in alkali-activated slag binders.
• To evaluate the impact of BW on the mechanical, microstructural, thermal, and acoustic properties of the binder.

Main Methods:

• Preparation of alkali-activated slag composites with varying BW content (0-25%).
• Assessment of compressive strength at 7 and 28 days.
• Microstructural analysis using X-ray diffraction (XRD) and scanning electron microscopy (SEM).
• Determination of thermal and acoustic insulation properties and hydration temperature.

Main Results:

• A slight increase in compressive strength was observed with 0.05-0.5% BW addition, peaking at 44.4 MPa with 0.25% BW at 28 days.
• Homogeneous distribution of small BW amounts reduced crack propagation, while larger amounts led to non-homogeneous distribution and reduced strength.
• SEM confirmed good adhesion between BW and the alkali-activated slag matrix.
• Improved thermal and acoustic insulation performance was noted with BW incorporation.

Conclusions:

• Biochar waste (BW) can be effectively incorporated into alkali-activated slag binders.
• Optimal BW content (around 0.25%) enhances compressive strength and improves thermal and acoustic insulation.
• BW acts as an inert micro-filler, potentially reducing hydration temperature and improving material sustainability.