Influence of an Alkaline Activator and Mineral Admixture on the Properties of Alkali-Activated Recycled Concrete Powder-Foamed Concrete

Area of Science:

• Materials Science
• Construction Engineering
• Sustainable Building Materials

Background:

• Alkali-activated recycled concrete powder-foamed concrete (ARCP-FC) is an emerging insulation material.
• It utilizes recycled concrete powders (RCPs), slag, fly ash, and sodium silicate.

Purpose of the Study:

• Investigate the impact of W/C ratio, Na2O content, and mineral admixtures on ARCP-FC properties.
• Determine optimal mix designs for enhanced mechanical strength, physical characteristics, and thermal conductivity.

Main Methods:

• Systematic variation of W/C ratio, Na2O content, and fly ash percentage.
• Evaluation of compressive strength, dry apparent density, water absorption, and thermal conductivity.
• Microstructural analysis to understand pore structure and capillary formation.

Main Results:

• Increased W/C ratio decreased strength and density but increased water absorption.
• Optimal W/C ratio found to be 0.45 due to rapid setting and reduced capillaries.
• Na2O content influenced strength and density, with 6% being optimal; excessive amounts harmed insulation.
• Fly ash addition reduced shrinkage and thermal conductivity by creating spherical pores.

Conclusions:

• An optimal ARCP-FC mixture (60% RCPs, 20% slag, 20% fly ash) achieved 800 kg/m3 density, 59.1% porosity, 4.1 MPa strength, and 0.1036 W/(m·K) thermal conductivity.
• ARCP-FC effectively balances compressive strength and low density for insulation applications.
• This material shows significant promise for external insulation boards and layers in sustainable construction.