Weathering resistance of Linz-Donawitz (LD) slag as ballast material using freeze-thaw and sulfate soundness

As nonrenewable natural aggregates with acceptable geotechnical properties become scarce, costly, and entail negative environmental impacts, the study of alternatives remains a first-order challenge for sustainable railway design. This paper focuses on the physical and chemical weathering effects of the industrial byproduct Linz-Donawitz (LD) slag as a ballast material. For this purpose, 75 freeze-thaw (F-T) and 40 sulfate soundness (SS) cycles were carried out on the byproduct. We present a series of laboratory experiments involving particle characteristics, durability and strength for different F-T and SS cycles. To benchmark the performance of LD slag, we also performed our experiments on two natural aggregates: gneiss and basalt. Our main findings reveal that: (i) the shape of LD slag ballast and its particle size distribution are unnafected by the F-T and SS cycles, (ii) the basalt exhibits higher magnitudes of fouling after SS cycles, (iii) losses in Los Angeles abrasion and shock resistance were much more pronounced in SS tests for all ballast materials, (iv) LD slag is more resistant and less susceptible to the degrading effects of freezing and thawing, (v) point load tests indicate that the loss of resistance of basalt is small compared to that of gneiss, (vi) the byproduct showed a decrease in strength of 87% after 40 SS cycles, suggesting that chemical weathering exerts a dominant control on the performance of LD slag. The findings are relevant to elucidate the physical and chemical weathering effects of LD slag and to promote its sustainable use.