Concrete cube testing in London.

Mostly not. 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. That excludes central, east and south London. The outer north-west boroughs, around Barnet, Harrow and Hillingdon, are borderline, so send the postcode and we will confirm. Elsewhere your team or your supplier makes the cubes and we test them.

By courier, by your own delivery up the M1 to Milton Keynes, or by collection when we are on your site for plate bearing or other testing, if you tell us when you book. Wrap cubes damp, pack them so they cannot knock together and send them to arrive before the first test age. On a rolling programme, a regular weekly courier run works well.

Yes. Give us the pour programme and the required ages. Each set of cubes is booked in by reference when it arrives, scheduled against its casting date and reported as soon as it is crushed. What makes it work is a consistent reference from your side: level, pour number and element. That is the detail most often missing when a result has to be traced months later.

It affects what should be specified. London Clay commonly carries sulfates, so piles, basements and other buried concrete are designed to a sulfate class from the ground investigation and the mix is chosen to suit, often with a high proportion of GGBS. A cube test confirms compressive strength, not sulfate resistance, so check every delivery ticket against the specified mix.

Not necessarily. Mixes with a lot of GGBS or fly ash, common in London basements and piles, gain more of their strength after 7 days than a CEM I mix does, so an early result looks low by comparison. A 7-day result is an early indicator, not a verdict. Conformity is judged at the age your specification sets, normally 28 days and sometimes 56.

The cube is loaded to failure in a calibrated compression machine, and the 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 reference, age at test, dimensions, failure load, strength and whether the failure pattern was satisfactory.

Check the specimen first. Identification, age at test, curing history, dimensions and failure pattern can all explain a low figure. If the result stands, the next move is your engineer’s, commonly a spare cube at a later age or cores from the element to establish the in-place strength. We cut cores on London sites, so both can stay with the same laboratory.

No. A cube is compacted and cured under standard conditions and shows what the concrete as supplied can achieve. Concrete in a column, wall or slab is placed and cured in place and is normally somewhat weaker. Cube results judge the conformity of the supply, and in-place strength is assessed from cores.

Your specification sets the sampling rate, usually by reference to BS 8500 and BS EN 206, depending on the volume and importance of the pour. A set from each sample covering the specified ages, plus a spare, is common. Make every cube in a set from the same sample and tell us which are spares to hold.

Somewhere level, sheltered and still. A fresh cube is sensitive to temperature, drying and vibration for its first day. Keep the moulds covered, out of direct sun and frost, at around 20 °C if you can, and away from piling rigs, hoists and traffic routes. Leave them at least 16 hours and no more than 3 days before demoulding, then keep them wet until they travel.

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 marked on each cube and a schedule that matches it: site, level and element, supplier and mix reference, casting date and time, testing ages and who receives the results. Add slump or flow if it was measured. With several contractors and pours on one London site, the reference is what keeps results attached to the right concrete.

No. There is no Hixtra laboratory or office in London. The 020 number rings through to the laboratory in Milton Keynes, where every cube is cured and crushed. Milton Keynes is straight up the M1, so a same-day courier or your own delivery is simple to arrange.