Is gravel becoming scarce? Evaluating the local criticality of construction aggregates

- The criticality of sand and gravel has to be evaluated at a local scale.
- Two new approaches, strong and weak locality, were introduced.
- The criticality of aggregates in the regions of a country is driven by the Supply Risk.
- The regions with major Swiss cities present higher criticality scores.

Natural aggregates are considered an immense natural resource at the global level; however some regions face a supply constraint due to the overexploitation of natural aggregates in construction. This paper presents an assessment of the local criticality of quarried aggregates by adapting the methodology for metal criticality determination to the characteristics of construction aggregates. Two approaches, strong and weak locality, are envisaged to examine different substitution scenarios in the case of local supply constraint. The adapted methodology examines three dimensions: Supply Risk, Environmental Implications and Vulnerability to Supply Restriction. The application of the methodology to the cantons of Switzerland shows that inside a country, the criticality is driven by the Supply Risk, which depends on the surface and number of quarries and their distribution in the region. A comparison of the supply risk of aggregates with the supply risk of steel shows that for most of the cantons the supply risk of natural aggregates is lower. The application of this methodology at a world scale will indicate highly critical regions and enable policymakers to define measures for ensuring a sustainable growth, either by regulating the extraction of aggregates or by demonstrating the local need to consider the use of other materials, apart from concrete.

203