Cement Grinding Aid (CGA)

The introduction of Cement Grinding Aid (CGA), started more than 50 years ago, has as ultimate task the prevention of
cement particle re-agglomeration during and after milling process. What makes CGA application
even more desirable is their significant effects on mechanical properties of cement, whose particle
size distribution results narrower and shifted towards shorter diameters.
Their influence on cement chemico-physical behaviour has been attributed to the reduction of
surface energy forces generated on cement grains during comminution.
CGA are constituted of polar organic compounds such as alkanolamines, which arrange their dipoles
so that they saturate the charges on the newly formed particle surface, reducing re-agglomeration.
Nevertheless, this kind of additives results efficient even at very low dosage (< 500 ppm), which
cannot give reason of a complete covering on cement particle surface, that is for a complete
screening of the free charges. Moreover, it cannot give reason of their effects on subsequent
mechanical properties of cement paste.
Various research groups followed different approaches to go further in the interpretation of the CGA
action. Some authors have been involved in the analysis of alkanolamines and glycols based CGA,
extracted from dry cement by different technics. Besides the intrinsic difficulty in the extraction of
this polar compounds, once they interact with cement, it has been hypothesized either an
irreversible physic adsorbtion or a chemical interaction with cement salts, favoured by high
temperatures (100-120°C) reached inside the mill during grinding process.
Much more interest has been shown on the influence of these alkanolamines or glycols as
admixtures on cement hydration and strength development. It is well known, for example, and
well accepted that alkanolamines (especially TriIsoPropanolAmine - TIPA) interact preferentially
with iron based phases of cement . In the same way TriEthanolAmine (TEA) effect on cement
setting time is still debated.

Recently technology of CGA has been developed. We have not only Amine based , but also Glycol , Polymer Glycol and Polymer Glycol Ester as latest technology . There are some CGA's producers in the world ,Sika is one of it. SikaGrind®-870 is a chloride free liquid cement grinding aid with performance enhancing properties. SikaGrind®-870 has been specifically designed to increase the output of cement grinding plants and obtain improved early strength development for cements with high amount of clinker replacements SikaGrind®-870 is a dispersant with the following characteristics:  Neutralisation of electrical charges on the surface of the cement particles  Separation of the cement particles SikaGrind®-870 provides the following advantages in cement production:  Enhanced grinding properties of the cement mill due to less accumulation of material on grinding balls and mill-liners  Higher separator efficiency due to improved cement particle dispersion  Reduced relative power consumption per ton of cement due to increased output of the grinding system (tons per hour)  Easier achievement of the desired cement fineness (Blaine, particle fraction > 32μm, granulometry) due to reduced re-agglomeration of the sufficiently ground cement particles  Minimized problems with “plugging” due to improved powder flow characteristics SikaGrind®-870 gives the following advantages to the finished cement:  Reduced quantity of “over-milled” particles in the cement granulometry  Easier discharge of the silos  Increased early strengths after 1 and 2 days  Economic cement design with clinker replacements Typical dosage rates of SikaGrind®-870 are between 0.2 -0.5 kg per tonne of cement (0.02% - 0.05% of total weight = cement clinker + additions). The optimum dosage to achieve the desired characteristics shall be determined in Plant trials. Influencing factors are e.g. the properties of clinker source, type of cement and other plant variables. For consistent results, SikaGrind®-870 must be accurately dispensed