It starts at the rock face
A quarry works a face of hard rock, in Victoria most often basalt (the bluestone of the volcanic plains) or hornfels. The rock is drilled in a pattern and blasted in controlled charges, breaking the face into broken rock of manageable size. This is the raw feed for everything that follows.
The blasted rock is loaded by excavator and hauled to the primary crusher. Nothing about the finished product, its size or its grading, is decided yet; that all happens in the crushing and screening that comes next.
Crushing, stage by stage
How the products are made
The same crushed feed becomes different products depending on how it is screened and blended.
| Product | How it is made |
|---|---|
| Road base / crushed rock | Blended across the full size range so it compacts |
| Crusher dust | The fine end, screened off on its own |
| Single-sized aggregate | Screened to one size and washed of fines |
| Cement treated rock | Road base blended with cement at a pug mill |
Grading to a VicRoads class means controlling these proportions so the mix sits within the specified envelope.
For what those products are and how they differ, see crushed rock vs dust vs aggregate.
Testing and the stockpile
Quarries test their products against grading and strength requirements, and on registered VicRoads sources the rock and its products are certified for their specified use. The finished material is stored in stockpiles by product and class, ready to be weighed onto a truck and delivered. That weighbridge ticket is where your order begins. Curious how it gets to you? See truck loads explained.