Beaver Plastics Ltd.

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DYNAFLEX Void Form is an expanded polystyrene (EPS) product designed to protect grade beams, pile caps and other concrete structures from the forces of subgrade up-lift or the swelling of clay soils.

Dynaflex Void Form is manufactured from inert closed cell expanded polystyrene (EPS), used for protecting concrete grade beams, pile caps and other concrete structures from subgrade uplift. Its function is to compensate for frost lensing and swelling of underlying soils that might otherwise lift or fracture concrete structures. Dynaflex will not soften or collapse due to water absorption and, as a ‘solid’ void material, tends to resist soil movement into underlying spaces. Dynaflex has excellent resistance to freeze/thaw, is not biodegradable and has no pest nutrient value.

Available in Standard, Md-2 & Hd-4 Grades

DYNAFLEX Standard will protect many grade beams or other concrete loads up to 1.5 meters in height with minor deflection at time of pour. Dynaflex Md-2 and Hd-4 are two stronger versions available for use when higher concrete placing loads may cause higher initial loss of original thickness. Md-2 and Hd-4 will provide less capacity for absorbing soil swell.

All polystyrene products are thermoplastics and consequently will creep under load, losing compressive resistance over time. Using our maximum load recommendations will result in less than 10% loss of thickness due to short term concrete placing loads.

Specifying the thickness of a void form product.

Common practice may be to double the amount of anticipated soil swell in specifying the thickness of a compressible void form under grade beams. However, the following calculation using a project’s specific conditions will more accurately determine the required Dynaflex version and thickness.

  1. Select the Dynaflex version to be used (Standard, Medium or High Density) determined by RECOMMENDED MAXIMUM CONCRETE PLACING LOADS (see chart on data sheet).
  2. Establish the uplift resistance of the superstructure and foundation. This will be the total weight of the entire superstructure plus the mass and uplift friction resistance of the piles themselves over the area supported by the Dynaflex, expressed as the Structure’s Uplift Resistance (SUR), in kPa.
  3. Find the resulting maximum product deformation from either the data sheet chart, using the SUR.
  4. Divide maximum anticipated soil swell (mm) as determined by a soil investigation by the maximum deformation (%) to produce the needed thickness (mm) of that particular Dynaflex version.