- What is Marble?
Very few rocks have as many uses as marble. It is used for its beauty in architecture and sculpture. It is used for its chemical properties in pharmaceuticals and agriculture. It is used for its optical properties in cosmetics, paint, and paper. It is used because it is an abundant, low-cost commodity in crushed stone prepared for construction projects. Marble has many unique properties that make it a valuable rock in many different industries. The photographs and captions below illustrate just a few of its varied uses. Marble is a metamarphic rock that forms when limestone is subjected to the heat and pressure of metamorphism. It is composed primarily of the mineral calcite (CaCO3) and usually contains other minerals, such as clay minerals, micas, quartz, pyrite, iron oxides, and graphite. Under the conditions of metamorphism, the calcite in the limestone recrystallizes to form a rock that is a mass of interlocking calcite crystals. A related rock, dolomitic marble, is produced when dolostone is subjected to heat and pressure.
- Materials and Experimental Procedure
- Determining Material Properties
To determine the physicomechanical properties of the selected marble samples, workpieces were prepared and UW, P, UCS, SH, and ITS tests were conducted according to ISRM  standards, whereas FS and BAR tests were conducted according to TS 699 . Thin sections of marble samples were analyzed for mineralogical-petrographical characterizations.
- Polishing Tests
Polishing tests were carried out by using a laboratory-scaled polishing machine designed to be similar to an industrial-scaled machine, equipped with a conveyor belt of 60?cm width and four polishing heads of 35?cm diameter (Figure 1). An abrasive series consisting of 60, 80, 120, 180, 220, 280, 320, 380, 600, and 800, 5 Extra, and a felt pad (Pulitore) were used. The workpieces were obtained from a marble processing plant and were calibrated with diamond abrasives in dimensions of 500?mm long, 300?mm wide, and 20?mm thick. Ten points were marked on the edges of the strips to ensure that the roughness and glossiness measurements were taken from the same points for all samples. Operational polishing machine variables such as belt speed and rotational speed of the polishing head were fixed at 1.48?m/min and 499.5?rpm, respectively. Pressure of the polishing head was kept at 1.25?bar for 60–800 numbered abrasives and reduced to 1 bar for 5 Extra and Pulitore cases. 60 numbered five abrasives were mounted on a grinding head, and six separate polishing tests were conducted for each marble unit by using only one polishing head. After the polishing stage, a compressor was used to blow off the dust and the water drops remaining on the surface of the strips.
Marble industry contributes significantly to the socio-economic development of any country. Due to the abundance of marble reserves, Pakistan relies on marble industry, which in turn contributes to its GDP. Marble powder (MP), produced from the marble industry is also increasing, which constantly remains a source of hazards to the environment. At the same time, natural sand deposits are decreasing, causing an acute need for a product that matches the properties of sand in concrete. This study has been conducted to demonstrate the possibility of using MP as a replacement of sand in the manufacturing of concrete. The MP was used in 5 different dosage percentages ranging from 0% to 100% by weight of sand with an increment of 25%. The effect of MP on the strength behavior of concrete was studied at three different curing ages (7, 14 and 28 days). It was observed from the results that MP could potentially replace sand up to a certain limit without compromising on strength. It was also noticed that 50% sand replacement with MP was optimum at which 13.52% and 35.54% increase in compressive and flexural strength was achieved compared to the control sample. Based on the results of this experimental study, it is clear that MP can partially be used in place of sand in concrete.