Exposed Aggregate Concrete SWMS

Exposed aggregate concrete installation is a decorative concreting process used widely across Australian residential driveways, commercial entrances, civic plazas and external paving. The work combines a standard concrete pour with a selected aggregate top layer, application of a surface set retarder chemical, controlled high-pressure washing to expose the stones, and a final sealer coat. Each phase introduces distinct WHS exposures: manual handling of wet concrete and aggregate, respirable crystalline silica liberated during washing of partially set surfaces, hazardous chemical contact from retarders and sealers, and slip/wet works hazards from washing runoff. Under WHS Regulation 2025 section 291, this work is classified as High Risk Construction Work because it involves use of substances containing silica and exposure to hazardous chemicals at a construction workplace. A SWMS prepared, consulted on with workers, and kept available for inspection is therefore mandatory before work commences, and must be reviewed if the method, crew or site conditions change materially.

Hazards identified

7 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1Elimination — Specify factory pre-cast exposed aggregate panels where design allows, removing on-site retarder use and silica wash exposure entirely from the works
2. 2Elimination — Schedule wash-off during low-occupancy windows so adjacent trades and public are removed from the silica and slurry exposure zone
3. 3Substitution — Select low-VOC water-based acrylic sealer over solvent-based product and use surface retarder formulated without hazardous secondary amines where compatible
4. 4Substitution — Specify pre-washed decorative aggregate to reduce dust generation and use bagged retarder paste over spray formulation to limit aerosol exposure
5. 5Engineering — Use wet-method pressure washing at the lowest effective pressure (under 3000 psi) with extended lances and ensure continuous water film suppresses respirable silica
6. 6Engineering — Install slurry containment bunding, silt socks and a settlement tank to capture wash water in accordance with EPA and Council stormwater requirements
7. 7Administrative — Issue this SWMS at pre-start, conduct toolbox on retarder SDS, rotate finishing crew every two hours and post exclusion zones during pressure washing
8. 8Administrative — Air monitoring for respirable crystalline silica per AS 2985 on first three pours and health surveillance under WHS Reg Schedule 14 for exposed workers
9. 9PPE — P2 respirators during wash-off, chemical splash goggles, nitrile gauntlets, alkali-resistant overalls and waterproof safety boots for retarder and sealer handling
10. 10PPE — Hi-vis long sleeves, knee pads, full-face shield during pressure washing and organic vapour cartridge respirator (ABEK-P2) during sealer application

Applicable Codes of Practice

High-Risk Construction Work triggered

Worked example

On a mid-rise apartment forecourt paving project, the concreting leading hand runs a pre-start brief at 6:45am before a 40 square metre exposed aggregate pour. He opens this SWMS on a site tablet and walks the four-person crew through the hazard register, pausing on respirable silica during wash-off and the alkaline retarder spray. The crew identifies a new hazard not captured: a public footpath sits two metres from the pour edge, so the supervisor adds a pedestrian exclusion control referencing barricade signage and amends the wash-off window to after 4pm when foot traffic drops. Each worker signs the SWMS sign-on register, confirming they hold current respirator fit-test records and have reviewed the retarder SDS pinned to the site shed. During placement at 10am, wind shifts and begins driving retarder overspray toward the building façade. The finisher pauses work, the supervisor consults the SWMS chemical control row, and the crew switches from spray application to roller application on the leeward edge, recording the change in the daily SWMS amendment log. At wash-off the next morning, the operator wears a P2 respirator and full face shield as specified, with slurry captured by pre-positioned silt socks draining to a settlement tank, demonstrating live use of the document as a working control plan rather than a filed compliance artefact.

Related legislation

• WHS Act 2011 (model)
• WHS Regulation 2025
• Crystalline Silica — National Strategy + CoP

Frequently asked questions