Petrological assessment of drying shrinkage of sedimentary rock used as aggregates for concrete

Abstract

The drying shrinkage of different sedimentary rocks used as aggregates for concrete, mainly sandstone, is evaluated on the basis of petrological characterization and water vapor sorption. The drying shrinkage of aggregates is dependent on their alteration and metamorphic types, and is especially influenced by the types and contents of their constituent minerals and pore spaces between the crystals. There was a positive correlation between drying shrinkage of aggregates and water vapor desorption. When the volume of pores 4–20 nm in diameter was reduced, drying shrinkage and water vapor sorption were drastically reduced. In the case of sandstone aggregates, drying shrinkage of the aggregate is large in the early stage of alteration while it decreases with the progress of alteration and metamorphism processes. The presence of secondary type-A muscovite indicates a transitional stage between these processes, which is an important petrological feature in evaluating aggregate shrinkage. These results clearly show that differences in geothermal gradient and compression intensity from the time of deposition to the present manifested as the alteration and metamorphic types, with divergent pore distributions. The drying shrinkage and the water vapor sorption of aggregates reflect these petrological characteristics and resultant pore distributions.