The correct choice of stone aggregate for railway ballast is directly related to the stability, safety, efficiency, and maintenance costs of the track. The aggregate must meet several criteria to be deemed suitable.
A recent study evaluated four distinct stones from the eastern region of São Paulo, Brazil: two granites, one diabase, and one basalt. Using Brazilian and ASTM procedures, tests on 55 mm and 75 mm specimens, under both dry and wet conditions, showed all stones meet established physical properties. Among the mechanical properties, uniaxial compressive strength stood out; the tested materials all exceeded the required 100 MPa set by Brazilian standards.
Regarding accelerated weathering tests using ethylene glycol, only the basalt exhibited significant changes, yet its resistance remained below 10%. These findings suggest the tested stones are fit for use as railway ballast, which is of considerable importance for making informed decisions on railway infrastructure materials.
Railway systems are integral to the efficient movement of goods and people, and the ballast, consisting mainly of stone aggregates, facilitates the stable support for tracks and absorbs stresses from trains. This study provides insights on the characterization of stones, which is pivotal for enhancing the safety and durability of railway services.
Before sampling, geological observations and petrographic descriptions of the quarries were conducted. The stones chosen were analyzed for their structure and composition—DIA diabase, BAS basalt, and two granite varieties, GRAN1 and GRAN2, all displaying significant strength characteristics. The 'DIA' diabase reported the highest compressive strength of up to 260.29 MPa under specific conditions, surpassing other materials.
Petrographic analysis revealed all stones fall within Brazilian density and porosity standards, meeting the required criteria to withstand the pressures related to railway use. Specifically, the diabase and granites were recognized for their compact and low-porosity structures. These features play key roles in ensuring effective stress distribution and minimizing maintenance costs associated with track integrity.
The study is anticipated to bolster the standards governing stone use as railway ballast. By enhancing the existing datasets on Brazilian stone materials, it aims to promote safer and more effective railway infrastructures.
Overall, the research highlights the necessity of rigorous testing and evaluation of aggregates, enabling railway projects to select the most suitable materials efficiently—thus safeguarding the longevity and safety of the transportation system.