SIKA TECHNOLOGY AG

Comprehensive understanding of ­grinding aids

1 (l) The milling media (balls) coated themselves with cement if no grinding aid is used
2 (r) Grinding aids keep the milling media (balls) clean and increase the productivity
3 Reaction on the clinker surface (tricalcium silicate, C3S): water molecules (H2O) react with top surface layer oxide ions (O2-) to form hydroxide ions (OH-) [2]
4 Diagram of different directional forces on molecules. Surface tension is the effect of one-sided forces on the surface [6]
6 The drop shape ­depends on the inter­action between liquid and solid surface
7 Interactions of two TIPA molecules (triisopropanolamine) on dry C3S surface (tricalcium silicate, alite) [1]
8 Energetically unfavorable, improbable fracture with partly separated charges
9 Fracture without water and grinding aid. The formed surfaces attract each other very strongly
10 Fracture only with water. The formed surfaces attract each other strongly
11 Fracture with water and glycerine. The formed surfaces attract each other moderately
12 Fracture with water and diethylene glycol (DEG). The formed surfaces attract each other weakly
13 Fracture with water and diisopropanolamine (DIPA). The formed surfaces attract each other very weakly
14 Two triisopropanolamine (TIPA) molecules on hydroxylated (OH−) tricalcium silicate (C3S) surface. For simplification, only top layer of C3S surface is shown
15 Adsorption energies of triethanolamine, triisopropanolamine, methyl-diisopropanolamine and glycerine on dry and hydroxylated C3S (tricalcium silicate) at 25 °C and 110 °C [2]
16 (l) Two C3S surfaces with an intermediate monolayer of glycerine molecules [2]
17 (r) Two C3S surfaces with an intermediate monolayer of glycerine molecules in separated state; both surfaces are half covered [2]
18 Distribution of gylcerine molecules on approximately half covered clinker surface (top view)
19 Agglomeration energies of dry and ­hydroxylated C3S as well as hydroxylated C3S with glycerine, triethanolamine, triisopropanolamine and methyl-diisopropanolamine at 90 °C (For numeric values see Table 3) [2]
20 Agglomeration energies of dry and hydroxylated C3A as well as hydroxylated C3A with triisopropanolamine, glycerine, triethanolamine and methyl-diisopropanolamine at 90 °C [11]
21 PCE (polycarboxylate ether) molecule on hydroxylated clinker (C3S) [12, 19]
22 PCE (polycarboxylate ether) molecule between hydroxylated clinker, distance of the two C3S surfaces: 9 Å [12]
23 PEO (polyethylene oxide) molecule on hydroxylated clinker (C3S) [12]
Sika Technology Center Zürich all by SIKA TECHNOLOGY AG

Grinding aids increase the productivity and cost-effectiveness of cement production. A comprehensive experimental test program and a variety of computer simulations were used to determine the physical and chemical mechanisms of action.

1 Introduction

Grinding aids have been used successfully for decades in cement production and many other areas, such as ceramics, pigments etc. The main effect is to reduce energy consumption and increase the grinding efficiency. Additional features can be improved – e.g. powder flowability and strength development of binders. There is surprisingly little verified knowledge about the way in which the substances contained in grinding aids act effectively. There are correspondingly many hypotheses in the scientific literature as well as in industrial practice. Starting from basic physical and...

TEXT Dr. Martin Weibel, Sika Technology AG, Zürich/Switzerland
Dr. Ratan K. Mishra, Institute for Building Materials, ETH Zürich/Switzerland

This article appeared in

ZKG 06/2014

This article appeared in

ZKG 06/2014

Ressort:  Materials
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