Your Concrete Answer: Size and Shape Analysis of Cement

Cement is the most used material in the construction industry, accounting for the production of over 4 billion tons per year. It is an inexpensive and easy-to-produce material that consists of a complex mixture of inorganic components, such as silicates and aluminates. The hardening of the cement is mainly due to hydration, which means the combination of water with the different cement components.

There are five different types of cement, namely CEM I to CEM V. The most relevant for general construction are CEM I and CEM II. CEM I is a pure Ordinary Portland Cement (OPC), while CEM II is a mixture of OPC and additives such as fly ash, slag, or limestone, up to a maximum additive content of 35%.

Within each type, there are three grades, based on the 28-day compressive strength of the concrete that they produce. The grades are 32.5, 42.5, and 52.5. The cement is also classified according to its strength development: R indicates an early strength gain and N stands for normal strength development. For example, a cement CEM I 42.5 N is pure OPC giving a strength of 42.5 MPa with “normal” strength gain. Besides the usual Portland cement, special formulations are often needed, such as quick-setting cement. This special type of cement starts the hardening process only a few minutes after being mixed with water and is usually set in less than one hour. Quick-setting cement is mainly composed of OPC and aluminum sulfate as a catalyst for the hydration process.

Moreover, the cement's quality is strongly dependent upon the size and shape of its particles, which affect its surface area, compression strength, and curing time. Particles that are too fine cause an exothermal setting in the final product, while particles that are too large do not fully hydrate. Complementary to particle size, particle shape is a critical parameter to monitor. Cement flowability and water demand may vary drastically for regular (spherical) and irregular particles.

Here, we show the application of Litesizer DIA 500 – the Anton Paar Dynamic Image Analyzer – to evaluate different cement types from different manufacturers. Litesizer DIA 500 uses a high frame-rate camera to capture the image of a large number of individual particles in a short time. The result is both particle size and shape distribution in a few seconds.