Characterization and thermal behavior of marble from northwestern Pakistan

摘要

This research aimed to determine the physical and strength characteristics and temperature-based behavior of marble. Based on laboratory investigations, marble from northwestern Pakistan (Chitral and Khyber) was characterized as follows: (i) high water absorption (0.16%), high porosity (similar to 0.42%), low ultrasonic pulse velocity (similar to 4000 m/s), and low strength (53 +/- 4 MPa) calcite with an equigranular texture with uneven boundaries and sutured contacts and (ii) low absorption (0.05%), low porosity (0.13%), high ultrasonic pulse velocity (6200 m/s) and high strength (68 +/- 6 MPa) quartz-rich calcite having an inequigranular texture with linear boundaries and mosaic contacts. Under thermal treatment, water absorption and porosity initially decreased at 100 degrees C (calcite expansion) followed by an increase around 200 degrees C (thermal fracturing) and then by a decrease at 300 degrees C (tightening of thermal fractures). Bulk density did not show any significant change within the range of these temperatures, and the ultrasonic pulse velocity trend was generally reversed. Both compressive and tensile strengths showed an initial increase at 100 degrees C followed by a decrease at 200 degrees C and then by a low decrease at 300 degrees C. As expected, the compression strength (40 MPa-120 MPa) was found to be almost one order of magnitude larger than the tensile strength (4 MPa-12 MPa).