In brief
- A test certificate covers the batch and source it names, so a new plant, quarry or mill needs a fresh record before the material goes into the work.
- Ask the supplier in writing for the new source name and a certificate for the actual batch, then sample that delivery yourself.
- Keep the old and new records side by side in the acceptance file so anyone can see where the material changed.
Contents
A supplier change of source breaks the chain between the test record and the material on site. Re-test before the next pour: ask for the new source name in writing, take a sample from the delivery itself, and hold the material until a result covers it. The old certificate cannot carry over.
What counts as a change of source?
A change of source is any switch in the plant, quarry, mill or stockyard the material comes from, not just a new company name. Treat it as a change when the cement works supplying your brand moves, when aggregate arrives from a different pit, or when a new depot starts breaking bulk.
Cement brands blend and bag at more than one works, so the brand name on the bag does not prove the cement inside matches your last certificate. Aggregate is the same: two lorries from one supplier can come from two pits, and pit A sand and pit B sand can grade differently. Steel mills and block plants change too.
The delivery note is where this shows. Ask the supplier to write the source on every note: works or plant name, pit name, mill name. If the note only says the brand, ask the depot manager which works the batch came from. Record the answer in the site diary the day the lorry arrives.
How do you re-test cement after a source change?
Re-test cement on the first delivery from the new source, before that cement goes into structural concrete. Ask the supplier for the certificate for the batch on the lorry, then check it against the bag markings and the delivery note. Do not accept a general brochure or a certificate from an older batch.
On site, inspect the bags: look for lumps, hardened edges and torn sacks, and set aside any bag that fails. Keep a sample of the delivery sealed and labelled with the date, the batch and the source. A laboratory can run setting time and strength tests; ask the laboratory for its rate and turnaround before you need the result.
The same discipline applies when comparing a replacement brand against the one already approved. Put both sets of records side by side and note which batch each result belongs to, as set out in how do you check a supplier's test certificate in Somaliland?.
How do you re-test aggregates, blocks and steel?
Aggregate needs a fresh sample from the new pit or stockpile before it is batched into structural concrete. Ask the laboratory for grading, silt and clay content and, where the mix design allows, an impurity check. Changing sand changes the water demand of the mix, so tell the engineer and confirm whether the mix design still holds.
Blocks and steel follow the same logic. Take a block sample from the new plant and have a laboratory crush it rather than judging by colour or weight. For reinforcement, check the mill mark on the bar against the certificate for that heat or batch, and confirm the bar diameter and surface condition. Ask the laboratory or the engineer which tests they will accept for the new source.
Do not release the material to the work until the result is in the file and the engineer has seen it. If the pour cannot wait, use material from the approved source.
What record should the file hold?
The acceptance file should show the source, the date it changed and the test that cleared it. Write a short note: old source, new source, date of first delivery, sample reference, test result and the engineer's decision. Keep the old certificate behind the new one so the history is readable.
Mark each delivery so bags or bundles from a new source are easy to separate on site. The practice in how do you mark and trace cement bags across a Somaliland site? keeps a new batch from being mixed into an approved stack.
Label every sample with the date, the source and the batch before it leaves site, and keep a duplicate. When a future delivery is questioned, the labelled sample answers it. Use the concrete calculator to see how much material a pour needs so you order from one source for the whole element where possible.
What to do next
Before the next delivery from the new source, send the supplier a short written request: source name, batch number and the certificate for that batch. Then take a sample from the lorry on arrival, label it with date, source and batch, and hold the material until the engineer accepts the result. File the note in the acceptance record. See materials for the wider set of checks.
Frequently asked questions
Does a new certificate from the same brand mean the source changed?
Not by itself. Ask the supplier to name the works, quarry or mill on the delivery note, and compare it with the source written on the previous certificate. A new certificate for the same source confirms a new batch, not a new source.
Can old stock from the previous source still be used?
It can be used while the old certificate covers it and it is stored correctly. Keep it separate from the new source and labelled, so the two are not mixed before the new result arrives.
Who decides whether the new material is accepted?
The engineer for the project makes the acceptance decision. The site team's job is to supply the sample, the certificate and the source record, and to keep the material out of the work until that decision is written down.
Sources
Local reporting: this article is written for building work in Somaliland. Ground conditions, prices and rules differ between places; confirm the details for your own site.