Upcycling C&D Fines Into New Cement

Upcycling C&D Fines Into New Cement Using Clean and Fully Electrified Method

Funding Source: Hinkley Center for Solid Hazardous and Waste Management

Coarse crushed concrete particles can be recycled and reused as aggregates in new concrete, however concrete crushing fines are notoriously difficult to upcycle and reuse in concrete. Crushed concrete fines are made mostly of reacted and unreacted cement with some small aggregate particles mixed in. Concrete crushing fines are too small to be used as aggregate in new concrete and have a high water absorption that makes it difficult to use directly in concrete. New approaches could increase the value of this construction demolition waste beyond using it as fill. A second material, construction & demolition (C&D) fines can contain particles of soil, gypsum, asphalt, concrete, or other mixed materials. They can also be difficult to recycle because of their mixed and varied nature.

A new approach to transforming inert inorganic materials into amorphous and reactive materials in cementitious systems has been proposed called mechanochemical activation. Mechanochemical activation (MCA) uses high intensity grinding to activate oxides and make them amorphous. The intense grinding uses less energy than pyro-processing and has no out gasses that need scrubbed. Recent work at Lulea University showed that it may be possible to extend MCA to concrete crushing fines to activate them for reuse as a new cement, with sufficient strength to be used in pavements and building structures. This very recent and preliminary work gives hope that MCA could be used to complete the full recycling circle of this key component of demolition waste, and possibly be extended to other waste materials. While the recent work on MCA showed that it is possible to reactivate cement fines, work is needed to determine the applicability and limits of the system to then scale up the process. It may also be possible to apply MCA to the second class of materials of interest, C&D fines. Work is needed to determine if C&D fines can be activated like concrete crushing fines can be activated and if the C&D fines will react in a beneficial instead of deleterious manner in concrete.

This research is analyzing peer-reviewed literature and data on MCA methods, recycled concrete fines properties and composition, C&D fines properties and composition, and MCA-activated cementitious material performance in concrete. Focus will be on methods that can scale to commercial production and be cost-competitive and have a lower environmental footprint than virgin portland cement. The research will determine if MCA can be used to transform concrete crushing fines into a new cement using recycled concrete from Florida, using a process summarized in Figure 1. The newly produced cement will be evaluated for reactivity and strength development. A techno-economic analysis will be conducted to determine material commercial viability. MCA will be also tested on C&D fines to determine if this method is applicable for this material.

Upcycling C&D Fines Into New Cement Using Clean and Fully Electrified Method – Proposal

Project Team

Principal Investigator: Kyle Riding