Performance of structural concrete using Waste-to-Energy (WTE) combined ash

Area of Science:

• Materials Science
• Environmental Engineering
• Civil Engineering

Background:

• Municipal solid waste (MSW) combustion in Waste-to-Energy (WTE) plants generates substantial ash.
• Current disposal methods for WTE ash primarily involve landfilling after metal recovery.
• Developing alternative uses for WTE ash is crucial for waste management and resource sustainability.

Purpose of the Study:

• To evaluate the feasibility of using combined bottom and fly ash (combined ash) from WTE plants as a substitute for natural stone aggregates in cement mortar and concrete.
• To assess the impact of ash substitution on the mechanical properties of concrete and mortar.
• To determine the leachability of heavy metals from concrete and mortar incorporating WTE ash.

Main Methods:

• Combined ash was fractionated into fine (<2 mm), medium (2-9.5 mm), and coarse (9.5-25 mm) sizes.
• Stone aggregates in concrete were replaced by coarse and medium ash fractions up to 100%.
• Fine ash was used as a sand substitute (10 wt%) in cement mortar.
• Mechanical properties (compressive strength) and leachability (EPA Method 1313) were tested after curing.

Main Results:

• Concrete with up to 100% coarse and medium ash aggregate replacement achieved compressive strengths exceeding 28 MPa after 28 days.
• Mortar with 10 wt% fine ash as sand substitute showed comparable results to commercial products.
• Leachability tests confirmed effective immobilization of heavy metals within the concrete matrix.

Conclusions:

• Waste-to-Energy ash can be effectively utilized as a sustainable aggregate in concrete and mortar.
• The use of WTE ash in construction materials meets mechanical performance standards.
• This application offers a promising solution for managing WTE ash and reducing reliance on natural aggregates.