How do you test whether milled clay has been activated?
Compare the treated clay with an untreated portion of the same material for structural change and pozzolanic reactivity. Particle-size data show how fine the powder became. Jar temperature and pressure describe the milling process, while a reactivity measurement addresses the proposed cement application.
Separate particle size, structure and reactivity
Mechanical treatment can alter clay mineral structure as well as reduce particle size. Compare an untreated portion of the same clay with the milled material. Measure the change in particle distribution separately from structural change and pozzolanic reactivity for the proposed cement blend.
Researchers at the University of Bath investigated clay activation by ball milling as an alternative to thermal calcination. Identify the starting mineralogy when comparing results from kaolinitic, smectitic and illitic materials.
Conditions of the planetary milling experiment
The RETSCH PM 100 example used a 500 mL stainless steel jar, twelve 20 mm stainless steel balls and a 25:1 ball-to-powder ratio. The reported treatment lasted 20 minutes at 500 rpm. These conditions identify the experimental comparison; a different clay or loading calls for a new comparison.
What the jar measurements show
GrindControl recorded increases in temperature and pressure during milling. After 20 minutes the experiment reached up to 55 °C and about 1,700 mbar. Pressure development may reflect gas release, but these readings alone cannot identify the mineral reaction or quantify the product’s pozzolanic performance.
How should two milled clay samples be compared?
Compare milling treatments on an identified clay and evaluate the product using a suitable characterization method. Tool contact, energy input and loading should be recorded with the result. A grinding condition that works for one mineral mixture is not automatically transferable to another.
| Consideration | Information to provide |
|---|---|
| Clay preparation | Mineral identity and starting state |
| Treatment record | Vessel, media and loading |
| Activation assessment | Structural and reactivity tests |
Discuss material testing with Glen Mills or Contact Glen Mills for information or a quote.