Lightweight aggregate made by microwave irradiation

Abstract

The paper presents experimental results of the manufacture of a lightweight aggregate from a waste (recycled clay brick from the demolition of buildings) and an industrial by-product (coal ash) using the unconventional microwave heating technique. The manufacturing process is based on the direct microwave heating at high temperature (over 1160 ºC) of the finely ground mixture of the raw material having incorporated a foaming agent (silicon carbide) with a role in expanding the material. The manufactured aggregate is a porous product with low apparent density and low thermal conductivity (below 0.80 g/cm3 and below 0.148 W/m·K, respectively), high mechanical strength (up to 8 MPa), low water absorption (below 7%), being suitable for the production of lightweight concrete. The specific energy consumption of the thermal process is very low (0.83-0.89 kWh/kg).

Keywords

• lightweight aggregate
• direct microwave heating
• coal ash
• clay brick waste
• mechanical strength