Work

Recycled and mechanically activated concrete fines as a complete substitute for Portland cement − Feasibility and life cycle assessment

Year: 2025

Type: article

Abstract: Construction and demolition waste (CDW) puts significant pressure on landfills and natural resources worldwide. Although partial substitutions of Portland cement (PC) with various recycled materials have been reported, a complete (100 %) replacement using recycled concrete remains problematic. In the present study, a novel binder was produced entirely from recycled concrete fines (RCF), while recycled aggregates were incorporated to replace virgin aggregates. High-energy grinding in a planetary ball mill was applied to the RCF fraction below 150 µm. Particle size reduction occurred after grinding, resulting in a decrease in d 50 from 139 μm to 3.18 μm. The intensity of the X-ray diffraction (XRD) peaks corresponding to muscovite, microcline, and portlandite decreased significantly. On the other hand, quartz was only slightly affected. Activated RCF was used as a 100 % PC replacement in paste and concrete mixes. Compressive strengths of approximately 20 MPa were obtained after 28 days in laboratory tests for concrete with w/c equal to 0.6. A preliminary life cycle assessment (LCA) was performed to evaluate the environmental impacts, focusing on carbon emissions and resource depletion. The LCA results suggested over 90 % reduction in CO 2 emissions compared to traditional cement-based mixes. Even at the laboratory-scale milling with high energy consumption per 1 kg of RCF, the impacts correspond to 50 % of traditional concrete (TC). Benefits remain significant over short transporting distances of the processed recycled ingredients; however, resource depletion exceeds TC after about 200 kilometers, and carbon emissions go beyond TC after approximately 800 kilometers. • MC-activated RCF can fully replace PC, reaching 20 MPa without mix optimization. • Environmental benefits drop with transport: gains lost beyond 200 km, CO₂ penalty above 800 km. • Even with high MCA energy, 100RC’s impact stays below 50 % of traditional concrete.

Source: Case Studies in Construction Materials

DOI: 10.1016/j.cscm.2025.e04798

Authors: Magdalena Rajczakowska, Ankit Kothari, Thanyarat Buasiri, Andrzej Cwirzen

Institution: Luleå University of Technology

Language: English

Topic: Recycled Aggregate Concrete Performance

Subfield: Building and Construction

Field: Engineering

Domain: Physical Sciences

SDGs: Responsible consumption and production, Industry, innovation and infrastructure, Climate action, Sustainable cities and communities

Open Access status: gold

Estimated APC paid: $2,660