Title:
Dry Reclaiming Technology for Producing Aggregates from Returned Concrete
Author(s):
A. Brocchi, G. Ferrari, S.H. Norman, J. Hoh, M. Ho, F. Khomsani, S. Bagade
Publication:
Symposium Paper
Volume:
370
Issue:
Appears on pages(s):
25-34
Keywords:
Circular economy, dry reclaiming, flocculants, polyacrylamide, polyacrylic acid, recycled aggregates, returned concrete, sustainability
DOI:
10.14359/51751745
Date:
5/1/2026
Abstract:
Returned concrete is the residual amount of fresh concrete that is not placed at the jobsite and comes back to the ready-mixed plant in the truck mixer. This amount is estimated from 3 to 5 per cent of the overall ready-mixed concrete production and represents the main waste at the ready-mixed concrete plants. Returned concrete can be treated by washing with large amounts of water, whereby coarse and fine aggregates are recovered with the heavy burden of producing a large amount of wastewater, which can be recycled into new concrete production. In addition, the production of sludge always accompanies this process.
Recently, a new dry reclaiming method not using water has been developed, based on the addition of special additives to returned concrete, which are capable of instantaneously transforming fresh concrete into a dry material, from which reclaimed aggregates can be easily recovered. The main advantage of the dry method is that concrete can be fully recovered as aggregates without generating any waste, both in liquid or solid form, and therefore can be considered more sustainable compared to the wet methods.
In this study, different technologies to treat returned concrete by the dry method are compared with a focus on the quality of resulting aggregates to produce new concrete. The results indicate that the reclaimed aggregates obtained by the dry process can be conveniently used up to 30 per cent by weight as a replacement of natural aggregates without affecting concrete performance.
Related References:
1. Obla, K.H. and Kim, H., “Sustainable Concrete through Reuse of Crushed Returned Concrete,” TRR-Journal of the Transportation Research Board, N. 2113, 2009, pp. 114-121.
2. Diotti, A. et al., “Experimental Evaluation of Recycled Aggregates, Washing Water and Cement Sludge Recovered from Returned Concrete,” Appl. Sci., No. 12, 1(36), 2022.
3. Ferrari, G., Miyamoto, M. and Ferrari, A., “New Sustainable Technology for Recycling Returned Concrete,” Construction and Building Materials, No. 67, 2014, pp. 353-359.
4. U.S. Patent 10,875,032, “Method for Producing Aggregates from Returned Concrete,” 2020, assignee Mapei S.p.A.