The railway industry is seeking high-performance and sustainable solutions for sub-ballast materials, particularly in light of increasing cargo transport demands and climate events. The meticulous design and construction of track bed geomaterials play a crucial role in ensuring an extended track service life. The global push for sustainability has prompted the evaluation of recycling ballast waste within the railway sector, aiming to mitigate environmental contamination, reduce the consumption of natural resources, and lower costs. This study explores materials for application and compaction using a formation rehabilitation machine equipped with an integrated ballast recycling system designed for heavy haul railways. Two recycled ballast-stabilised soil materials underwent investigation, meeting the necessary grain size distribution for the proper compaction and structural conditions. One utilised a low-bearing-capacity silty sand soil stabilised with recycled ballast fouled waste (RFBW) with iron ore at a 3:7 weight ratio, while the second was stabilised with 3% cement. Laboratory tests were conducted to assess their physical, chemical, and mechanical properties, and a non-linear elastic finite element numerical model was developed to evaluate the potential of these alternative solutions for railway sub-ballast. The findings indicate the significant potential of using soils stabilised with recycled fouled ballast as sub-ballast for heavy haul tracks, underscoring the advantages of adopting sustainable sub-ballast solutions through the reuse of crushed deteriorated ballast material.

The use of bituminous subballast (BS) in railways has gained importance due to structural and geometrical enhancing properties of these infrastructures. Oftentimes, during renovations the paving quality control of bituminous mixtures is compromised due to reduced time span. To verify the effects of significant air voids content variation on the mechanical response of railway tracks, this paper performed a 3-D numerical modelling of a Brazilian railway renovated with BS. First, the BS was characterised in laboratory for model inputs. Then, 3-D numerical models were developed assuming two constitutive behaviour for the BS: linear elastic and linear viscoelastic. An all granular track was also simulated for comparisons. Numerical results were compared with actual instrumented test section. As expected, displacements on foot-of-rail and stresses on the subgrade were reduced when using BS. Moreover, the different air voids content of the bituminous mixture evaluated herein caused low variation in the overall track response. GRAPHICAL ABSTRACT

Cement addition and pozzolanic reaction in construction and demolition waste recycled aggregates can stabilize the base of pavements chemically. A way to control and explore the maximum benefits of it is necessary. This study establishes a mix between recycled cementitious and red ceramic-waste aggregates with hydrated lime to enhance pozzolanic reactivity in the material and achieve the best mechanical properties compared with those of a portland cement or recycled concrete aggregate itself pavement base layers. Chemical tests (Chapelle and thermogravimetry), physical tests (grain size distribution, density), and mechanical tests [unconfined compressive strength (UCS) and resilient modulus (RM)] were conducted. The increase of hydrates in the fine fraction of the mixes and the recycled aggregate itself correlated with the resulting increase in UCS and RM. The limited contribution of the self-cementing reaction of recycled cementitious aggregates was quantified, resulting in an UCS of 1 MPa and RM of 1,000 MPa. The pozzolanic reaction of cementitious and red ceramic aggregates with hydrated lime achieved an UCS of 8.4 MPa and RM of 2,800 MPa, values closer to those achieved by a portland cement stabilized pavement base (5.4 MPa and 4,500 MPa, respectively).

Construction and demolition waste (CDW) worldwide generation accounts 10 billion tonnes yearly. The major fraction is landfilled requiring innovative recycling methods to reduce the associated environmental impacts and to increase its circularity. Our study demonstrated the feasibility of using different CDW fines to develop recycled cements and optimized the content of CDW recycled cements with well-graded crushed stone (WGCS) for use as pavement base layer. We scaled up the study obtaining CDW cement and aggregates from a local recycling plant, as well as pilot pavement sections designed, constructed and field deflections measured. As results, the CDW cement pastes exhibited accumulated heat values of up to 111 J g ⁻¹ and achieved a compressive strength of approximately 16 MPa. The unconfined compressive strength and resilient modulus (RM) achieved using CDW cement and WGCS were 2–3 and >3000 MPa, respectively. The sections constructed using CDW cement exhibited intermediate behaviour compared to those obtained using reference materials (6% Portland cement-WGCS and a conventional granular base made using WGCS). The deflection decreased over time owing to the pozzolanic reaction.

Um parâmetro usado como indicador da resposta elástica e qualidade da via permanente em diversas ferrovias é o módulo de via (u), o qual requer a determinação de deslocamentos (deflexões) em campo. O presente trabalho tem o objetivo de apresentar um dispositivo para medição de deslocamentos (DMD), desenvolvido para registrar deflexões durante a passa-gem dos trens sem interrupção da operação da ferrovia. Para demonstrar sua viabilidade, o DMD foi usado em medições de dois segmentos da Estrada de Ferro Carajás (EFC), com diferentes condições de lastro e dormente. Os resultados apontaram que o dispositivo se mostrou apropriado para realizar as medições de deslocamentos, que posteriormente são usadas no cál-culo do módulo de via. Adicionalmente, no estudo de caso foi possível observar que a forma de carregamento (função da velocidade) implica em respostas mecânicas diferentes, e que a medida de deslocamentos efetuada no patim do trilho é mais adequada. Ademais, observou-se que o dispositivo também pode eventualmente ser capaz de indicar um possível defeito na roda ou no trilho. De modo geral, concluiu-se que o DMD pode ser uma ferramenta útil para auxiliar a gerência de manuten-ção de uma ferrovia.

Equipamento triaxial cíclico de grande escala para análise mecânica de lastro ferroviário