Which method is typically used to determine the specific gravity of coarse aggregate?

• A. Hydrometer method
• B. Pycnometer method
• C. Sieving method
• D. Microwave method

Answer: (B)

The pycnometer method is commonly used to determine the specific gravity of coarse aggregate due to its accuracy in measuring the volume of solids by means of water displacement. This method involves the use of a pycnometer, which is a device designed specifically for measuring the density of materials.

In this process, a known weight of the aggregate is placed in the pycnometer and filled with water. The increase in volume results from the aggregate replacing some of the water, allowing one to calculate the specific gravity using the mass of the aggregate and the volume of water displaced. The precision of this method makes it suitable for coarse aggregates, which can vary in size and shape.

Other methods, such as the hydrometer method, are typically utilized for finer materials and may not be as effective for coarse aggregates due to their larger particle size. The sieving method primarily focuses on particle size distribution rather than density measurements, and the microwave method is generally not recognized for determining specific gravity. Thus, the pycnometer method stands out as the most effective and reliable approach for calculating the specific gravity of coarse aggregates.