CM 840

Combimix 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

Compressive strength class

4,350 psi

Flexural Strength, class

1,015 psi

Fire resistance class


Adhesion to surface

> 144 psi (> 1.0 MPa)

Thickness 1


Weight (dry state)

105 lbs/ft3

Wet volume weight

123 lbs/ft3

Water requirements

4.4 qt/33 lb

Workplace temperature

50–77 °F

Mixing time

2–3 min

Working time

20–30 min

Final set

30–60 min


approx. 11

Water damage resistant



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 72 psi. 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 50 °F. For best results, the ambient temperature in the work area should be between 50 and 77 °F. 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 90 % as the upper limit for applying the CM 840.


Mix the dry powder with max 4.4 qt (4.2 L) of cold, potable water, max 28 %, per 33 lb (15 kg) bag. Do not overwater. Mix for 2–3 minutes with a heavy duty drill mixer (650 minimum rpm) to obtain a lump-free mix. Product may be refreshed by re-mixing but do not ad more water.


Apply blended material onto substrate at a thickness of 0” to 2” (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. The guiding value assumes a curing temperature of approximately 68 °F, 40 % RH and proper air flow. Newly produced surfaces must be protected against wind, sun and rain.

Consumption calculator

CM 840

Consumption calculator


+46 171 46 65 90

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Contact us

  • Verkstadsvägen 6
  • 746 40 Bålsta, Sweden
  • Tel. +46 171 46 65 91
  • Fax. +46 171 46 65 99
  • E-mail:


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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