Where the section is large enough, a box culvert serves not only as a watercourse but as an underpass — pedestrian, livestock, farm vehicle or service access.
As the section grows, so does the formwork problem: withdrawing steel formwork from a tall closed box demands heavier equipment and more time. MenfeX® removes the step entirely — the formwork stays in place as the culvert's inner surface.
Top slab support is the critical item
As clear span increases, the deck form must carry wet concrete and construction loads. Above a given span, propping is installed beneath the top slab form; prop spacing by span is tabulated in the technical documentation.
This is not specific to MenfeX — steel systems are propped too. The difference is that here what gets struck is the props, not the formwork.
Scope and large spans
The confirmed standard range is a clear span of 1.00–3.00 m. For underpass culverts above this range we develop a project-specific solution — share your dimensions and we will assess suitability together.
Applications
- Pedestrian underpasses
- Livestock and farm vehicle crossings
- Service road crossings
- Large-flow stream crossings
FAQ
Will plastic formwork withstand the lateral pressure of fresh concrete?
Yes — provided the stated rate of placement and lift height limits are observed.
The lateral pressure fresh concrete exerts on formwork is not constant; it varies with pour rate, lift height, concrete temperature and consistency. This is the same physics for steel and plastic alike — every formwork system is designed to a defined pressure.
The design pressure, maximum rate of placement and maximum lift height for MenfeX panels are stated in the installation guide and on the panel label. Exceeding these limits can deform the panel — a rule that applies to every formwork system.
Does the top slab form need propping?
It depends on the clear span. Small spans may need none; larger spans do.
The deck form carries the weight of wet concrete plus construction loads, and that load rises quickly with span. Above a given span, propping is installed beneath the form. Prop spacing by span is tabulated in the technical documentation.
This is not specific to MenfeX — steel systems are propped too. The difference is that here what gets struck afterwards is the props, not the formwork.
How does the cost compare with steel formwork?
Compare total cost per culvert, not the price of the formwork.
MenfeX is a consumable; steel formwork is an investment. Placing the two purchase prices side by side is meaningless. The right benchmark is what it costs to finish one culvert: the per-culvert items that recur with steel — crane, erection, stripping, release agent, cleaning, freight, storage, patching — are absent or much reduced here. Against that, MenfeX is bought for every culvert.
An honest note: if you are casting hundreds of identical culverts in one location with a crane already on site, steel is probably more economical. The calculator will not hide that from you.
What is its behaviour in fire?
The culvert itself is reinforced concrete; the plastic is a thin surface layer.
In watercourse culverts there is effectively no fire load. On large-section culverts used as underpasses the client's engineer may raise the question; the material's fire behaviour is stated in the product data sheet.
Where a project requires it, the inner surface can be rendered or lined.
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Share your culvert dimensions, quantity and destination. We will return the configuration, container loading and lead time.