ARDEX A 29 Rapid Drying Cement for Internal and External Screeds Grey 20kg

• Product ID: 25434
• Suitable For: bonded, unbonded, and floating screeds
• Area of use: INT & EXT
• Application Method: float
• Time to full cure: 24 hours
• Volume: 20kg
• Container Type: bag
• Type: screed
• Brand: Ardex
• Manufactuer: Ardex
• Box Size: 1

ARDEX A 29 is designed for creating bonded, unbonded, and floating screeds for both internal and external applications. A mix ratio of 1:7 is appropriate for most standard screeding requirements. Additionally, a screed made with ARDEX A 29 meets the BRE Screed (ISCR) standards after just 24 hours, based on testing of a 50mm unbonded layer at 20°C.

SUBSTRATE PREPARATION

Bonded Screeds: To lay an ARDEX A 29 screed as a bonded screed, apply either ARDEX A 18 Screed Bonding Cement or a grouting slurry made from ARDEX A 29 and a bonding agent to a dry, properly prepared concrete base. For internal dry locations, mix ARDEX P 51 Primer and Bonding Agent with an equal volume of water, then combine with ARDEX A 29 cement and screeding sand to create a creamy grouting slurry. Apply the ARDEX A 29 Screed Mortar ‘fresh in fresh’ while the slurry is still wet. For external areas or wet environments, use ARDEX A 18 Screed Bonding Cement or prepare the slurry with ARDEX E 100 Additive for Bonding/Slurry Grouts, diluted with an equal volume of water. Ensure the concrete surface is mechanically prepared to expose the aggregate and is free of all contaminants.

Unbonded Screeds: For unbonded screeds, ensure the concrete slab is reasonably level before applying a damp proof or slip membrane. This membrane is crucial to prevent moisture from affecting the screed.

Floating Screeds: For floating screeds, place a suitable separating layer or damp proof membrane over the insulation before applying the screed mortar.

Moisture Considerations: ARDEX A 29 can be used on concrete bases with high residual moisture (above 75% RH), or where a damp proof membrane is not present. For projects with resilient floor finishes, it is recommended to use a damp proof membrane to protect the flooring from moisture. For unbonded and floating screeds, install a proprietary damp proof/slip membrane as per BS 8204-1:2003+A1:2009 and BS 5385-3:2014. For bonded screeds, apply ARDEX DPM 1 C or ARDEX DPM 1 C R once the screed is walkable (after approximately 8 hours). In cases of high residual construction moisture, ARDEX MVS 95 can be used instead, also applied when the screed is walkable.

MIX PROPORTIONS:

• Mix Ratio: Use a maximum of 1 part ARDEX A 29 Cement to 7 parts screeding sand by weight. The sand should be well-graded (0/8mm) and comply with BS EN 13139. For better workability, use sand with the following grading: 100% passing 10.00mm, 90%-100% passing 5.00mm, 65%-97% passing 2.36mm, and 0%-3% passing 75µm. If sand does not meet these requirements, you may mix in up to 10% 6mm aggregate by mass.
• Thickness Adjustments: For screed thicknesses greater than 50mm, consider using a fine concrete mix by replacing some sand with 8mm or 10mm single-sized aggregate. Adjust the proportions to maintain a workable mix and achieve the desired soundness.
• Water Addition: Add up to a maximum of 11 litres of water per 20kg bag of ARDEX A 29, including the water contained in the sand/aggregate. Adjust water to achieve a workable mix without forming excess water on the surface.
• Mixing: Use a forced-action mixer for best results. The mixed mortar should be semi-dry, retaining its shape when squeezed but not crumbling. Ensure no water film forms when compacted. Avoid using free-fall mixers, and do not add other cements, lime, or additives.

APPLICATION

The working time for mixed ARDEX A 29 mortar is approximately 90 minutes at 20°C. This necessitates that mixing, placing, compacting, and trowelling are completed promptly to ensure proper application and finishing. It is important to only mix and apply as much mortar as can be trowelled and finished within this timeframe. When laying a new screed adjacent to a set and hardened area, ensure that daywork joints are vertical, treated with a grouting slurry, and, if necessary, reinforced with steel.

For floors with a hot water underfloor heating system, allow 7 days after laying the ARDEX A 29 screed before increasing the water temperature to 25°C. Maintain this temperature for 3 days, then increase to the maximum floor temperature and hold it for an additional 4 days. During this period, avoid drafts. After this, let the floor cool to room temperature (above 15°C) before proceeding with floor coverings.

In terms of surface finish, for ceramic and quarry tiles, finish the screed using a wood float. For thin floor coverings like vinyl sheets, use an ARDEX Levelling and Smoothing Compound to achieve a very smooth surface, ensuring it is appropriate for the final floor finish. Refer to the relevant ARDEX Technical Datasheet for detailed recommendations.

For drying times, a bonded ARDEX A 29 screed is typically ready for ceramic tiles after 24 hours. Unbonded and floating screeds need 7 days to dry or a moisture reading of less than 2% using the Carbide method before tiling. Natural stone tiles can be installed after 7 days, and resilient or wood floor coverings can be applied after 7 days or when the moisture reading is below 2%.

Ensure that you account for drying times and application conditions to achieve the best performance from ARDEX A 29. For detailed guidance on faster drying options and mix variations, consult the specific ARDEX data sheets.