Incinerated biomedical waste ash in concrete production: A case study on hazardous material immobilization

ABSTRACT Inadequate management of Incinerated Biomedical Waste Ash (IBWA) poses a major challenge for the environment and public health. Simultaneously, the increasing demand for natural resources in civil construction calls for sustainable alternatives. Specifically in the context of Alagoas, Brazil, where healthcare waste production has increased, and where final disposal requires licensed landfills, the search for alternatives becomes pressing. This study investigated the technological and environmental feasibility of incorporating IBWA into concrete matrices, partially replacing river sand. The objective was a dual-benefit solution: hazardous waste valorization and natural aggregate conservation. The IBWA, sourced from an incinerator in Alagoas that treats various types of healthcare waste (with the exception of group C), were subjected to detailed characterization by particle size distribution, X-ray Fluorescence (XRF), X-ray Diffraction (XRD), and Thermogravimetric Analysis (TGA). For performance evaluation, concrete specimens were molded with sand replaced by IBWA at 0% (control), 5%, 10%, 15%, and 20% by mass. The results showed that the IBWA predominantly exhibited particle sizes similar to medium sand, with smaller particles acting to optimize contact points within the cement matrix, serving as a filler. The XRF chemical analysis indicated a high proportion of Calcium (53.232%) and Iron (19.658%), and a limited Silica content (5.408%), suggesting low pozzolanic activity. XRD confirmed the crystalline nature with the presence of Calcite and Calcium Silicates. In terms of mechanical performance, concrete with a 5% replacement of sand with IBWA maintained compressive strength significantly close to the control mix (15.55 MPa vs. 16.89 MPa at 28 days). However, increasing IBWA proportion (above 5%) resulted in a progressive reduction in compressive strength and increased porosity. As a result, water absorption tests indicated higher absorption at greater ash contents. Scanning Electron Microscopy (SEM) complemented the analyses, confirming particle morphology and distribution. The study concluded that the incorporation of IBWA in low proportions is technically promising for non-structural applications. This provides a viable route for sustainable hazardous waste management and innovation in construction materials.