Dynavoid 4" x 4' x 4' (sheet) #40144

Beaver Plastics

Beaver Plastics Dynavoid: Protection for structural slabs from frost and expanding clay soils.Dynavoid is designed to be used under structural concrete slab to prevent heaving caused by the upward movement of underlying ground. It is manufactured from inert closed-cell expanded polystyrene, and is not affected by moisture. Dynavoid will mechanically yield to rising subgrade at a sustained force of 50% or less of it's initial strength.


A void is generally required under cast-in-place structural concrete slabs where swelling soils might lift or crack the slab. Various materials can be used to create this protective void, with the primart function of having the structural capacity to adequately support concrete placing, finishing, as well as the weight of the slab. However, it must then reduce in strength to an appropriate time so as to relieve destructive forces from rising soil. Expanded polystyrene (EPS) products are often used to produce void spaces under structural slabs since EPS best serves the practical needs of construction. However, a programmed mechanical collapse mechanism is required so as to cause timely deformation and collapse of an EPS product, in order to accommodate the anticipated stress and strain of moving subgrades.

An EPS void product that is produces without a mechanical collapse mechanical mechanism can be manufactured with reduced density or cross-sectional area in order to reduce its strength. However, it is difficult to produce EPS strong enough to carry concrete placing loads yet resilient enough to absorb a large degree of subgrade motion. Without a programmed mechanical collapse mechanism, the stress that will be transmitted to the bottom of the slab will generally be beyond the slab's structural limit.

Product Description

Dynavoid is a new product for the construction industry that meets the requirements for a predictable and dependable structural slab void material. It is the first foam plastic product to qualify as a Dynamic Inclusion, as it is mechanically responsive to expanding soils.

Dynavoid has the structural strength to serve as false-work until a slab is self-supporting. It then uses thermoplastic creep to trigger a programmed, timely collapse, permitting the subgrade to rise without producing undue stress against the bottom of the slab. As soils begin to expand, causing an initial low level of sustained stress, the unique product geometry activateds slow deflection (creep) sideways. This sideways deflection continues until the point of complete 'over center' mechanical collapse, creating a void space for protection of the concrete. After collapse, the leg segments of Dynavoid are nested together. A small amount of additional compression strain can occur after collapse.

Dynavoid, with an initial compressive strength of 20.6 kPa (3psi) minimum, will support a total construction load of 2110kg/m2 (432 lb/sqft.). It is designed to begin deflection as soils expand and then collapse under a sustained stress of less than 10.3 kPa (1.5psi) in approximately 200 days.

Dynavoid may also conserve energy, serving as under-slab insulation.

Installation Instructions

Dynavoid panels are laid on prepared, level ground, with joints tight. The panels are easily cut to fit around protuberances, column bases, etc. Overlay materials (hardboard, fiberboard, etc.) are optional, to distribute point loads.

Health And The Environment

Dynavoid is one of the few foam plastic materials available that contains absolutely no CFCs, HCFCs, or other refigerant gases. It is non-toxic and hypo-allergenic, and will not irritate sensitive skin on exposure. Since EPS is not biodegradable, it will not emit odors or noxious gases, as can other void-forming materials.

Flammability Characteristics

Dynavoid contains a chemical additive to inhibit accidental ignition from a small fire source. This additive, however, will not prevent burning when the product is exposed to a large continuous fire or intense heat. Observe normal fire percautions and good housekeeping procedures during product storage and installation.


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