Ardex A 48 Rapid Set Screed

For fast-track floor prep on concrete substrates, ARDEX A 48 Rapid Set Screed allows you to lay tiles, natural stone, and terrazzo after 8 hours. It prevents the long drying delays of standard screeds, making it suitable for moisture-sensitive floor coverings, resilient systems, and parquet on commercial or residential projects.

What it does

This premixed cement and aggregate screed is formulated for rapid drying and high dimensional stability, helping to prevent the shrinkage cracks and curling common with traditional sand-cement mixes. It is compliant with the AS 1884 resilient flooring standard, allowing the application of smoothing cements after 24 hours and resilient or textile floorcoverings after 2 days. The rapid-setting binder system achieves 20 MPa compressive strength in 24 hours, meaning the screed is walkable in approximately 4 hours to keep trades moving on site.

Numbers that matter

• 8-hour tile window: Ready to receive tiles, natural stone, and terrazzo after 8 hours of drying, compared to the multiple days required by conventional screeds.
• 20 MPa compressive strength (1 day): Reaches approximately 20 MPa after 24 hours, rising to 30 MPa at 3 days and 35 MPa at 28 days to support heavy traffic and floor finishes.
• 15mm minimum thickness: Can be installed as a bonded screed at a minimum thickness of 15mm, or as an unbonded screed on a slipsheet at a minimum thickness of 40mm.
• 60-minute working time: Provides up to an hour of working time at standard temperatures, though mixing, placing, and finishing must proceed in rapid 10-minute succession to manage the fast-setting chemistry.
• 20kg/m² coverage: Requires approximately 20kg of dry powder per square metre for every 10mm of screed thickness.

Where to use it

ARDEX A 48 is suitable for internal and external concrete floors. It can be configured as a:

• Bonded screed directly over prepared concrete.
• Unbonded screed over a slipsheet.
• Floating screed over an insulating layer.
• Heated screed over floor heating systems.

It provides a stable base for the subsequent installation of tiles, natural stone, parquet, resilient floor coverings, and the ARDEX WPM 750 Undertile Butynol waterproofing system.

Installation and system limits

To ensure a successful installation, follow these process rules:

• Surface preparation: Subfloors must be mechanically prepared (shot-blasting, scarifying, or diamond grinding) to an open porous concrete matrix. Acid etching, solvents, and sweeping compounds must not be used. Direct-to-earth slabs require a damp-proof membrane or an ARDEX moisture barrier.
• Bonded slurry coat: Bonded applications require a wet-on-wet installation. Prepare a slurry bond coat using ARDEX P 51 mixed 1:1 with clean water and blend with the screed powder. Place the main screed mix directly into the wet slurry; do not allow the slurry coat to dry out.
• Bay sizing: Lay the screed in maximum 40m² bays, with the longest side not exceeding 8m. Maintain a length-to-width ratio of no more than 2. Separate bays with a 2mm gap, which can be joined the next day with epoxy to establish panels up to 100m². Bound all perimeter walls, columns, and directional changes with compressible foam strips and flexible polyurethane sealant.
• Compaction: Install in 50mm increments to ensure proper mechanical compaction. For multiple layers, follow the wet-on-wet slurry process between each lift.

Limitations

• Do not install ARDEX A 48 if the ambient or substrate temperature is below 5°C or above 35°C.
• Do not bond ARDEX A 48 directly to any ARDEX waterproofing membranes.
• Avoid placing heavy loads, such as pallets of tiles or heavy machinery, on the screed before it has achieved final strength.