Concrete cube testing in Cambridge.

Yes. Fresh concrete testing, meaning slump, flow and cube making at the pour, is only offered within about an hour’s drive of our laboratory in Milton Keynes, and Cambridge, Huntingdon, St Neots and Royston sit inside that. Our technician samples the concrete, tests the consistence and makes the cubes at the point of placement. Further east, at Newmarket, Ely or beyond, send the postcode and we will confirm.

If we made them, our technician collects them and they are in the curing tank the same day or the next, depending on the age at demoulding. If your team made them, you can deliver them to Milton Keynes, which is about an hour away, send them by courier, or have us collect them while we are attending for other testing. Keep them damp and protected from knocks in transit.

Whatever your specification requires. Most structural concrete is tested at 7 and 28 days, with conformity normally judged on the 28-day result. Some specifications add 3-day or 56-day tests, particularly for early striking or for mixes with GGBS or fly ash that gain strength later. Tell us the ages when you book and each cube is scheduled against its casting date.

The cube is loaded to failure in a calibrated compression machine. The compressive strength is the maximum load divided by the cross-sectional area, reported in newtons per square millimetre. Testing is usually specified to BS EN 12390-3. The report gives the cube reference, the age at test, the dimensions, the failure load, the strength and whether the failure pattern was satisfactory.

Your specification sets the sampling rate, usually following BS 8500 and BS EN 206, and it depends on the volume and the structural importance of the pour. A common arrangement is a set from each sample with cubes for 7 and 28 days, plus a spare. Make them all from the same sample, and tell us if any are spares to be held.

100 mm cubes suit most structural concrete with 20 mm aggregate. 150 mm cubes are needed where the aggregate is larger, because BS EN 12390-1 relates the specimen size to the maximum aggregate size. Keep to one size across a job so results compare like with like, and check the specification, because some contracts name the size.

Check the cube before the structure. Identification, age at test, curing history, dimensions and failure pattern all affect the result, and a low figure sometimes comes from the specimen, not the concrete. If the result stands, the next steps belong to your engineer and commonly include testing a spare cube at a later age and, if needed, coring the element to assess the in-place strength.

It is an early indicator, not a substitute. As a rough guide a CEM I mix reaches around two thirds of its 28-day strength by 7 days, but the proportion varies with cement type, additions, admixtures and curing temperature, and mixes with GGBS or fly ash gain more of their strength later. Treat a low 7-day result as a prompt to look closely, not as a verdict.

It affects the concrete that should be specified. Gault Clay and the other clays around Cambridge can carry sulfates, so foundations and buried concrete are normally designed to a sulfate class from the ground investigation. A cube test confirms compressive strength. It does not confirm sulfate resistance, which comes from the mix design, so check that the mix delivered is the one specified. We can test soil samples for sulfate in our laboratory.

Yes, and it matters. Fresh cubes left on an exposed site in winter can be chilled or frozen in the first day, which lowers the result and says nothing about the concrete in the structure. Keep them in their moulds, covered, somewhere sheltered and free from vibration, ideally at around 20 °C, for at least 16 hours and no more than 3 days. After that they belong in water in a controlled tank.

Hixtra holds UKAS accreditation to ISO/IEC 17025 under schedule number 8996. Accreditation is granted method by method, not to the company as a whole. Most of our soil and aggregate tests are on the schedule, and some concrete tests are still going through the accreditation process. If your specification or your client’s engineer requires accredited cube results, tell us when you enquire and we will confirm whether that method is on the current schedule before you book.

A unique reference on each cube and a list that matches it: the site, the element poured, the supplier and mix, the casting date and time, the required testing ages and who the results go to. Add the slump or flow if it was measured. Clear references avoid delays at the laboratory and mean a result can always be traced back to the pour it came from.

No. Hixtra has one laboratory, in Milton Keynes, about an hour from Cambridge, and all cubes are cured and crushed there. The 01223 number rings through to the same team as our other numbers. Because the distance is short, Cambridge is one of the few cities where we can attend the pour as well as test the cubes.