CM 840 Fine

CM 840 is a multipurpose trowelable patching compound for underlayments.

CM 840 can be installed on all types of concrete, well-bonded gypsum, bonded ceramic tile, quarry tile, Vinyl (non-cushion backed), VAT, VCT and PVC. Use Primer to block contact with gypsum-based surfaces. CM 840 is perfect for repairing cracks or creating slopes to drains. It may also be used on walls for repairs.

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Product specification

Technical data

Release of corrsive substances

CT (as per EN 13813)

Compressive strength class

C25 (as per EN 13813)

Compressive strength average

32 MPa (as per EN 13813)

Flexural strength class

F6 (as per EN 13813)

Flexural strength average

7 MPa (as per EN 13813)

Fire resistance class

A1 (as per EN 13813)

Adhesion to surface

> 1 MPa (as per EN 13813)

Thickness 1

0–50 mm

Thickness 2

6–20 mm

Grain size

< 0.5 mm

Material consumption

1.7 kg/m²/mm

Weight (dry state)

1700 kg/m³

Water requirements

4,2 l/15 kg

Workplace temperature

10–25 °C

Mixing time

2+1 min

Working time

20–30 min

Final set

30–60 min

Coverable (tiles)

1 hr


1–3 hrs


approx. 11

Water damage resistant


Surface Tensile Bond Strength, 28 days (sanded, loaded surface)

> 1 MPa


0.03–0.05 %



15 kg




The substrate should be clean and free of dust, cement skin, grease and other impurities that may prevent adhesion. Adhesion and surface resistance of the substrate should be no less than 0,5 MPa. Always prime the substrate with PP 600 and allow to dry before pouring (see PP 600 datasheet for proper dilution and installation directions). In terms of the primer forming a film, the temperature of the substrate must not be below 10 °C. For best results, the ambient temperature in the work area should be between 10-25 °C. At higher or lower temperatures, the time for curing will shorten or extend. Protect the product from excessive heat, excessive cold and draft conditions during and after the installation. It is recommended that the installation should be done with a proper air ventilation from an HVAC system. With the risk for cracks due to shrinkage or settings in the subfloor, a concrete surface should not be leveled within the first 28 days after casting. As a recommendation the RH in the concrete should have reached RH 95 % as the upper limit for applying the CM 840.


Mix the dry powder with max 4.2 L of cold, potable water, max 28 %, per 15 kg bag. Do not overwater. Mix for 2 minutes with a heavy duty drill mixer (650 minimum rpm) to obtain a lump-free mix.Let the mixed CM 840 rest for 1 minute and then mix it for 1 minute again. Product may be refreshed by re-mixing but do not ad more water.


Apply blended material onto substrate at a thickness of 0–50 mm for all surfaces by using a steel trowel. After initial set of material (approx. 10–15 min.), remove any overlap marks, seams and inconsistencies by scraping with a steel trowel.

Post-treatment and curing

Protect CM 840 from excessive heat or draft conditions during the curing process. Protect for up to 24 hours after completed installation. Material can be walked on after 30–45 minutes. Before covered by carpet be sure that the subfloor is dry enough. CM 840 is coverable after 1-3 hours. The guiding value assumes a curing temperature of approximately 20 °C, 50 % RH and proper air flow. Newly produced surfaces must be protected against wind, sun and rain.

Consumption calculator

CM 840 Fine

Consumption calculator


+46 171 46 65 90

Call our order department

Contact us

  • Verkstadsvägen 6
  • 746 40 Bålsta, Sweden
  • Tel. +46 171 46 65 90
  • E-mail: [email protected]


Combimix develops and manufactures mineral-based products for the construction industry. Our product range includes products for floor levelling, façade plastering, rendering, concrete resurfacing and restoration mortar for cultural buildings. We conduct sales in Europe and USA.

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