In brief
- A supervisor may be on site while the vibration check itself goes unrecorded, and unrecorded vibration checks can hide voids in members.
- Honeycombing sits inside members where it cannot be seen once the formwork comes off, so a pour record and core tests matter more than a final walk.
- Releasing each pour against a written checklist, with a named checker on site, closes the gap before concrete sets.
Contents
Concrete vibration supervision gaps in Borama show up as honeycombing inside columns and beams, not as visible defects at handover. One supervisor covering deliveries, slump tests and sampling cannot watch every poker point at the same time, so the vibration step gets assumed rather than checked. When a pour is released without a written record of poker depth, insertion spacing, layer thickness and hold time, voids can form inside members and stay hidden after the formwork comes off.
Where do concrete vibration supervision gaps start before the pour?
The gap opens before the first truck arrives, when nobody assigns a named checker for vibration. One supervisor covering deliveries and sampling cannot watch every poker point at the same time, so the check passes to whoever is free. General practice is to insert the poker vertically, let it sink under its own weight, hold each point until air stops rising and the surface turns glossy, and take the insertion spacing from the poker manufacturer's data. Treat these as general practice and confirm them against the project specification or the engineer. Confirm the required hold time and vibration duration against the project specification. Ask the project's engineer or the municipal office what pour records the project requires, and write that into the pour method statement.
What does weak vibration do inside a member?
Weak vibration leaves honeycombing and rock pockets where aggregate touches the formwork with no mortar around it. The damage sits at the base of columns, under beam soffits, behind starter bars and at construction joints, all places a final walk cannot show. A cold joint between two layers that were not vibrated together can leak and let rebar corrode. Detection is not visual. Ask the contractor for the pour record showing who checked each placement, then request cores or ultrasonic pulse velocity tests through a laboratory on the members you cannot inspect. On the next pour, watch the poker tip enter the previous layer so the layers knit, and confirm the required penetration depth into the previous layer with the engineer or the specification.
How can a client spot missed checks on site?
A client can spot the gap by asking three questions before the pour starts and writing the answers on the pour sheet. Who is the named vibration checker? How many pokers are working and what is their diameter? What is the layer thickness and the insertion spacing on this member? Walk to a recently poured column and look at the base and the joint line, then ask for the pour record and the cube or core results for that member. If records do not exist, ask a laboratory in the area for its test rate and arrange cores or pulse velocity tests on the suspect members. Ask the contractor what the contract allows for testing and for rework before you act.
What to do next
Pick the next structural pour on your site and write three lines in the site diary before it starts: the checker's name, the poker size and the insertion spacing. Photograph that page with the pour in progress. If no record exists for a member already cast, ask a laboratory for a rate and arrange cores or pulse velocity tests through the contractor, after checking what the contract allows.
Frequently asked questions
How soon can formwork come off to check for honeycombing?
Striking times depend on the mix, the member and the specification, so confirm them with the engineer. Cores or ultrasonic pulse velocity tests give a better picture of voids inside a member than stripping formwork early.
Can a contractor vibrate too much?
Yes. Over-vibration can segregate the mix and push paste away from the coarse aggregate. The poker should be withdrawn slowly and moved to the next point once air stops rising and the surface turns glossy.
Local reporting: this article is written for building work in Borama and Somaliland. Ground conditions, prices and rules differ between places; confirm the details for your own site.