What is schokbeton (shock-compacted concrete)?
Schokbeton (Dutch for “shock concrete”) is concrete that is subjected to repeated jolts while in the mould. This compacts the mix, making the concrete denser and giving it a smoother surface. The process was used for precast concrete elements and has since been replaced by compaction with vibrators.
How does it work?
Schokbeton was made from an earth-moist mix of sand, cement and fine gravel. The mix was placed in moulds, which were then repeatedly lifted and dropped vertically (“shocked”). This pressed the concrete together and compacted it. Because the mix contained little water, the element could be demoulded and used quickly.
History
According to the story, the process was discovered by chance by Dutch concrete worker Gerrit Lieve (1888-1944), who noticed that concrete in a wheelbarrow with a broken wheel had compacted on the way. He patented the idea and in 1932 founded N.V. Schokbeton in Zwijndrecht with his partner Matthijs Leeuwrik. Schokbeton elements were used until well into the 1980s, for example for facade panels and for the precast barns of the first farms in the Noordoostpolder. The company Schokbeton Saramac in Canada still carries the name.
Application
If you maintain or renovate a building with schokbeton elements, keep in mind:
- Recognising it: schokbeton often has a smooth, dense surface and sharp arrises; sometimes granite chippings or another decorative aggregate were added.
- Concrete decay: as with all reinforced concrete, the steel can corrode if the cover is thin or the concrete has carbonated. Spalling and rust stains are warning signs.
- Repair: have damage repaired professionally with a repair mortar matched to the existing concrete; on listed buildings also in colour and texture.
- Don’t just coat it: a dense coating or paint can trap moisture. Ask a concrete repair specialist if in doubt.
Related Terms
- Precast concrete
- Concrete cancer
- Concrete cover
- Earth-moist concrete
- Vibrated concrete
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