A Review and Experimental Study on the Performance of Rubberised Concrete Under Combined Freeze-Thaw and Sulphate...

The use of end-of-life tyre (ELT) rubber as a partial aggregate replacement in concrete represents a promising route for waste valorisation; however, its durability-related behaviour and long-term performance remain insufficiently characterised, particularly under combined environmental exposures. This study addresses these limitations by combining a targeted literature review encompassing more than 4500 data points from over 150 published studies with a laboratory-based experimental assessment of rubberised concretes aimed at clarifying key knowledge gaps. The experimental programme investigates concretes incorporating 5-50% ELT rubber (0/4 mm) as a selective replacement of a specific sand fraction, rather than of the total fine aggregate content, with particular emphasis on performance under coupled freeze-thaw cycling and sulphate attack. A reference mix (>50 MPa at 28 days) and seven rubberised concretes were characterised in terms of mechanical behaviour and selected durability-related indicators. Specimens were subsequently exposed for 270 days to freeze-thaw cycles (-20/+20 °C) in a 10% MgSO₄ solution, and surface damage and compressive strength loss were quantified. Increasing rubber content resulted in the expected reductions in mechanical performance, accompanied by lower electrical resistivity and increased porosity and carbonation depth. However, the selective replacement of a single sand fraction led to more gradual deterioration than typically reported for global sand substitution. Under combined freeze-thaw and sulphate exposure, concretes with low rubber contents (5-15%) exhibited no observable surface damage and retained most of their mechanical capacity, with compressive strength losses below 8%, whereas mixtures with ≥30% replacement showed pronounced surface degradation and strength losses exceeding 50%.