True Trade Expertise Across the Illawarra, Shoalhaven, and South Coast

Unfortunately, the Illawarra & South Coast has some of the worst concrete mixes, and we have seen some of the most horrible slabs to polish. Due to poor regional aggregate variations, inconsistent local batching, and shortcuts taken during coastal pours, you simply cannot treat every slab as suitable for high-end MPC.

Too many new operators try to mechanically polish every single floor they walk onto just to chase a dollar. It shouldn’t be done. Because MPC relies entirely on the structural integrity of the raw concrete foundation, it should not be done on low-spec or substandard slabs. If the foundation lacks the structural integrity to handle that process, forcing it will fail every single time.   

If you are planning a polished concrete floor, ensure your builder, concreter, and batch plant strictly adhere to these mandatory trade parameters before the trucks arrive on site.

New Slabs – Mandatory Mix Design & Pre-Pour Specs

Hand this structural recipe directly to your builder, concrete placement crew, and local batch plant (such as Boral or Holcim Geostone):

• Compressive Strength: Minimum 32 MPa structural mix (40 MPa highly recommended for premium zero-stone or nil-exposure finishes). Soft, standard 20–25 MPa driveway mixes will crumble under heavy planetary grinding.

• Zero Crusher Dust or Substitutes: The mix must use clean, washed sharp sands. Strictly no crusher dust, crusher fines, heavy slag, or high fly ash replacements. Crusher dust destroys the cement paste density, absorbs excessive water, and leaves a dead, dusty, micro-pitted surface that cannot take a crisp, high-gloss mechanical polish.

• Surface Flatness: Finished to a strict Class A / Class 1 flatness tolerance using a mechanical power trowel (helicopter). Rolling foundations or deep trowel ridges destroy aggregate consistency during grinding.

• Slump & Water Control: Maximum 80mm slump at the truck discharge point. Absolutely no site water is to be added to the mixer by the pump crew. Diluted cement paste causes aggregate segregation (sinking the stone to the bottom mesh) and leaves a weak, dusty “cream” surface layer that won’t hold a mechanical edge.

• Chemical Controls: Controlled water-reducers only. Strictly no heavy overdosing of superplasticisers or fluidisers to force an “easy” self-levelling pour. Overdosing separates the mix and leaves a gummy, rubbery surface laitance that instantly melts and clogs premium diamond tooling.

Curing & Local DIY Supplies Warning: Standard water-curing only. Do not apply any curing products, chemical compounds, or retail sealers without asking ProSand first. The truth is, the local DIY supply shops do not know what they are selling when it comes to mechanical polishing preparation. Off-the-shelf retail products create permanent barriers that completely block the liquid densifiers and chemical hardeners we must inject during our polishing stages—effectively ruining our entire refinement process.

Why True Mechanical Polished Concrete (MPC) Should Not Be Forced on Low-Spec Slabs

• 💪 The Concrete Will Crumble: A low-spec slab (such as a standard 20 MPa or 25 MPa driveway mix) is fundamentally too soft and powdery. When a heavy, 3-phase planetary grinder hits a soft slab, the bond strength of the cement paste cannot hold the aggregate. The diamonds will pluck and rip the stone stones straight out of the floor, causing the concrete matrix to pit, crack, and crumble.
• 🚫 It Will Not Hold a Polish: For concrete to hold a permanent, mechanical high-gloss shine, the cement paste must achieve high density through proper hydration and structural aggregate binding. Low-strength concrete, or concrete that was diluted with excessive site water during the pour, lacks this structural density. No matter how many fine diamond resin pads are run over it, the floor will remain dull, patchy, and incapable of holding a uniform polish.

We Treat the Slab Accordingly

At ProSand, we understand that forcing MPC onto a low-specification slab is a disservice to the client and a hazard to our machinery. If we determine your slab is low-spec or structurally unfit for the intense mechanical polishing process, we will tell you the honest truth on day one. We will then treat the slab accordingly and pivot the project toward systems engineered to succeed on that specific foundation.