Changes in the Physical and Chemical Properties of Weathered Maroubra Sandstone in Sydney

A cross section of the discarded plinth from the Australian Museum in College Street, Sydney was analyzed to determine differences in the physical and chemical properties of Maroubra sandstone after a century of natural exposure. Thin section petrography shows the sandstone contains 68% quartz, 14% each of clay and pores with minor amounts of siderite (3%) and secondary quartz (1.2%). Preliminary compressive strength tests indicate the Maroubra sandstone cross-section ranged from 28.63MPa to 42.84MPa in dry conditions, while it lost approximately half its strength in wet conditions. X-ray diffraction and infrared analyses confirm the clay that binds Maroubra sandstone is pre dominately kaolinite with minor amounts of illite. Subtle differences in kaolinite detected by infrared spectroscopy may be due to partial iron substitution of aluminium in the clay.