Heavy Duty Made Easy: Particle Size Analysis for the Cement Industry
Measuring particle size in cement can be difficult due to the fact that the particles have a very broad size distribution (from less than a micron to over 100 μm), and that they exhibit very irregular shapes. Additionally, they tend to agglomerate in dry state, and proper dispersion is crucial. Here we demonstrate the accuracy of the dry cement particle size analysis with Anton Paar’s Particle Size Analyzer, which exploits our patented Dry Jet Dispersion (DJD) technology. The results were then compared to measurements performed using the same instrument in liquid mode, on a non-aqueous cement suspension
Cement is made by baking a mixture of limestone (CaCO3), clay (mainly SiO2 and Al2O3) and minority constituents such as iron oxide, at 1450 °C. The resulting product is a rock-like substance called clinker, which then gets mixed and grinded with small amounts of gypsum (CaSO4) to form the fine powder we know as cement.
Grinding is a very energy-consuming process, and properly managing its parameters is an important economic issue. Narrowing the particle size distribution (PSD) will typically help to save energy and costs. However, different raw components of cement have different grindabilities, and the particle size distribution is usually broader for softer materials. Paradoxically, the addition of softer components (with broader PSD) leads to a narrowing of the PSD for the harder components, and vice versa. Thus, as grinding is critically influenced by the particle size distribution of the components, its analysis is performed at almost every step of the process.
Particle size also has a major influence on the properties of the final product. Together with the clinker’s chemical composition and its specific surface area, the PSD is a major factor affecting the hydration curve of cement as well as the strength of the hardened paste. Specifically, reduction in average particle size leads to decreased setting time and enhanced early strength. In contrast, the importance of coarser particles grows with aging of the cement. The width of the PSD also determines the cement’s water demand. In brief, it is possible to change the cement properties by modifying the particle size and its distribution.
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