Shrinkage behaviour and durability of recycled aggregate concrete incorporating thermo-mechanically treated coarse aggregates

Abstract

Recycled aggregate concrete (RAC) remains underutilised in structural applications due to excessive drying shrinkage and durability limitations associated with adhered mortar on recycled coarse aggregates (RCA). This study evaluates a thermo-mechanical (TM) treatment combining controlled moderate heating (100 °C–200 °C for 24–48 h) with mechanical abrasion (500–1000 revolutions) to improve RCA quality and the corresponding RAC performance. Eleven concrete mixtures at 50% and 100% RCA replacement were assessed for fresh properties, compressive strength, 180 d drying shrinkage, and durability indicators, water absorption, sorptivity, and rapid chloride permeability, supported by SEM–EDX–XRD characterisation and mass-loss quantification. The optimal treatment (TM-2 H: 200 °C/48 h + 1000 rev) reduced aggregate water absorption by 68% (6.15% to 1.95%), satisfying structural requirements. At the concrete scale, 180 d free shrinkage at 100% replacement decreased from 3311 µϵ to 2789 µϵ (15.8% reduction), while late-age shrinkage growth between 90 and 180 d fell from 37.7% to 5.6%, indicating improved microstructural stability. Sorptivity and chloride permeability were reduced by 31.8% and 42.5%, respectively. At 50% replacement, complete compressive strength recovery (34.4 MPa, statistically equivalent to the natural aggregate control) and full workability restoration were achieved

at 100% replacement, M25 structural-grade compliance was maintained. Improvements across measured properties are consistent with adhered mortar removal reducing aggregate water absorption and refining pore structure, though direct causal linkages among individual performance indicators require further controlled validation. A techno-economic assessment confirms commercial feasibility under Indian market conditions, with the concrete-level cost premium below 20% across all sensitivity scenarios. © 2026 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved. This article is available under the terms of the IOP-Standard License.