Crushing effects on the durability of rocky aggregates used on road surfaces subjected to winter maintenance and extreme climate conditions

Abstract

• The evolution of the internal structure of rocks regarding their crushing and sizing processes has been analyzed. • The effects of freeze-thaw and thermal stress durability tests with NaCl has been also studied. • Both rocks lost similarly weight and increased their water absorption coefficients after crushing and durability tests. • Durability tests affected more to aggregates than rocks, due to the negative impact of the crushing processes. • The specific area subjected to the agents of deterioration in the durability tests should be consider in future studies. • Thermal stress with salt is the most damaging durability test performed, especially on the aggregates analyzed. The internal structure of a rock is determined by its empty spaces (pores and cracks), which can evolve over time by chemical, physical, or biological processes. In construction, these chemical and physical processes, and their effects in the final products, known as aggregates, are well known, and controlled to estimate their quality and durability. However, the intrinsic properties of the raw material, the rock, and the processes that can affect its quality and durability during the production of the aggregates are poorly studied and considered in construction. For this reason, the evolution of the internal structure of two different types of aggregates used in Spanish roads were analyzed. The aggregates will be also studied in their raw form, rock, by measuring their water absorption coefficient and using mercury porosimetry and fluorescence microscopy. To estimate the influence of the internal structure in the durability of the aggregates, both forms, rocks, and aggregates, will be subjected to the combined effect of temperature variations and the salt used during winter maintenance operations on Spanish roads. The results obtained show that crushing processes in the quarry increase the water absorption coefficient of both materials and generate new micro-porosity caused by the microcracking of weak areas of the rock such as its schistosity or the presence of previous cracks. Thus, this increasing of the porosity produced by crushing processes in the quarry has a negative impact on the durability of the aggregates when they are subjected to winter maintenance operations and extreme climate conditions.