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 (O^2-) 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]

$8 Energetically unfavorable, improbable fracture with partly separated charges$

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]

all by SIKA TECHNOLOGY AG

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...