Cement is made by heating limestone with small quantities of other materials such as clay or sand to 1450°C in a kiln. The resulting ‘clinker’, is then ground with a small amount of gypsum into a powder to make Portland cement. The most common use for Portland cement is in the production of concrete – a composite material consisting of cement, aggregate (gravel and sand) and water.
Measuring and controlling the particle size distribution of cement is important both in order to achieve the desired product performance and to control manufacturing costs. Historic techniques of sieve and air permeability are still in use, but laser diffraction is becoming a more popular method to determine the particle size distribution of cement. The laser diffraction technique is quick, easy, reproducible, and provides a complete picture of the full size distribution.
Historic techniques to determine the particle size and surface area of cement include sieves and air permeability, or Blaine tests – see:
ASTM C430-9C430-96 Standard Test Method for Fineness of Hydraulic Cement by the 45-µm (No. 325) Sieve.
ASTM C786-96 Standard Test Method for Fineness of Hydraulic Cement and Raw Materials by the 300-μm (No. 50), 150-μm (No. 100), and 75-μm (No. 200) Sieves by Wet Methods.
ASTM C204-07 Standard Test Methods for Fineness of Hydraulic Cement by Air-Permeability Apparatus.
Many cement labs have switched to using laser diffraction to measure the particle size of their cement. This technology is fast, easy to use, flexible, and repeatable. HORIBA offers two laser diffraction analyzers to the cement industry: the full featured and automated LA-960, and the smaller, more economical LA-350.