Cold Weather Construction: Formwork Fasteners
> In brief > - Cold affects forming, coating and material behaviour in different ways. > - Temperature changes the process, not just the schedule. > - Dispatch from stock is what keeps a winter lead time honest.
Cold weather changes four things at once: concrete sets more slowly, lateral pressure stays higher for longer, striking times extend, and high-strength steel becomes less forgiving of impact. Each change has a hardware consequence.
Our own production and test data are available on request — see how our factory works and contact the engineering team for the documents behind any figure quoted here.
Pour pressure refers to the lateral pressure exerted by wet concrete on the formwork, which remains higher for longer in cold conditions. Striking time is the duration after pouring when the formwork can be safely removed, which extends in cold weather. Ductility means the ability of high-strength steel to deform under stress without breaking, which decreases at lower temperatures. Hydrostatic-equivalent height refers to the height at which the lateral pressure of setting concrete equals the hydrostatic pressure, which can be higher in cold conditions.
Pressure stays high.
Because the lower concrete has not gained strength, the pressure curve does not flatten as early. In practical terms, a pour that would reach its hydrostatic-equivalent height at 2.2 m in summer may behave closer to full hydrostatic at 5 °C. Tie spacing calculated for a summer pour can therefore be inadequate in winter even at the same pour rate.
The practical responses: reduce pour rate, reduce tie spacing in the lower zone, or both. If the layout cannot be changed, the pour rate must be, and the decision belongs before the pour starts.
Standard basis: EN 13670
Maturity and striking time.
Concrete strength gain is a function of time and temperature, so cold concrete reaches the same strength at a later date. Striking on a fixed timetable in winter is the most common cause of edge spalling around cones and tie positions. Either use a maturity method, or test cubes cured alongside the pour, or extend the striking time by a defined factor and record the decision.
Tie release and handling.
Frozen or stiff release agent, concrete bonded to cone surfaces and thread contamination from wet gloves all make cone extraction harder. More force is then applied at the cone, and the concrete edge — which is weaker at that age — pays for it.
Practical steps: keep release agent above freezing, cover cones and the top of the formwork against rain and snow where practicable, clean and re-oil rods immediately after striking, and store rods under cover rather than in a wet stillage.
High-strength steel at low temperature.
Carbon and alloy steels lose ductility as temperature falls, and the effect is more pronounced at higher strength classes. A class 10.9 or 12.9 part that would deform on impact at 20 °C can crack at -10 °C. Handling damage — dropped rods, hammered nuts, impact from frozen material — becomes more consequential.
Practical control: avoid shock loading during assembly, do not hammer nuts or cones into place, and inspect more frequently rather than less in cold cycles, because damage initiates as a crack rather than a bend.
Standard basis: ISO 898-1
Coating and storage.
Galvanized and plated surfaces are less reactive when cold and dry, but condensation is a bigger risk: cold metal brought into a warm, humid space will sweat. Rods moved from an unheated container into a heated site hut should be allowed to reach ambient temperature before unpacking, or wrapped so condensation forms on the wrap and not on the parts.
What to document in winter.
Pour rate actually used, concrete temperature at placement, ambient temperature record, striking date and method for judging strength, and any inspection findings on the hardware. When something goes wrong in a cold pour, that record is what distinguishes a design issue from a practice issue.
| Tie Spacing | Impact on Pour Rate | Consequence for Pour Schedule |
|---|---|---|
| Summer Spacing | No change | May cause formwork failure in winter |
| Reduced Spacing | Lower pour rate | Extends pour duration, safer formwork |
| Unchanged Layout | Slower pour rate | Delays project, ensures safety |
| Increased Ties | Faster pour rate | Reduces pour time, higher material cost |
References and standards.
- ISO 10683 — Hot dip galvanized coatings on fabricated iron and steel articles
- ASTM A36/A36M — Standard specification for carbon structural steel
- ASTM A615 — Standard specification for deformed and plain carbon-steel bars
- NIST corrosion and materials data
- ISO 9001:2015 — Quality management systems
- ISO 14001:2015 — Environmental management systems
About us: This article covers the impact of cold weather on formwork fasteners and construction processes. Our production and test data are available on request. Our contact page provides a way to reach our engineering team, and the about page documents how our factory works. This article was reviewed by the Qianheng Formwork Engineering team.