Concrete cube testing in Bristol.

No. Slump, flow and cube making at the pour are only offered within about an hour’s drive of our laboratory in Milton Keynes. Bristol, Bath, Weston-super-Mare and Gloucester are all well outside that distance, and there is no margin to check here. Your own trained staff or your readymix supplier will need to make the cubes. We then cure and test them.

Usually by courier. Wrap each cube in damp cloth and polythene, pack them in a rigid box so they cannot knock together, and send them to arrive before the first test age. If we are in Bristol for plate bearing or CBR testing, we can collect at the same time if you tell us when you book. You are also welcome to deliver them to Milton Keynes.

It can change the ages. Mixes with a high proportion of GGBS or fly ash are common in piles, bases and buried concrete on the estuary, because they resist aggressive ground well, and they gain strength more slowly. A 7-day result on such a mix looks low against a CEM I mix and is not a cause for alarm on its own. Some specifications judge these mixes at 56 days. Tell us the ages required.

It affects what should be specified. Estuarine alluvium can carry sulfates and chlorides, and the Mercia Mudstone and Lias clays around the city can carry sulfates too. Buried concrete is designed to a sulfate and aggressive ground class from the ground investigation. A cube test confirms compressive strength. It does not confirm chemical resistance, so check each delivery ticket against the specified mix.

The ages your specification sets, most often 7 and 28 days, with conformity normally judged on the 28-day result. Early-age tests and 56-day tests can be scheduled where the specification calls for them. Give us the casting date and the ages and each cube is tested on the right day.

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 the failure pattern.

Check the cube before the structure. Identification, age, curing history, dimensions and failure pattern can all produce a low figure that says nothing about the concrete in the ground. If the result stands, your engineer decides what follows, commonly a spare cube at a later age or cores from the element. We cut and test cores in Bristol.

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

Your specification sets the sampling rate, usually by reference to BS 8500 and BS EN 206, and on a large slab or base it is normally tied to the volume placed. 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 record which load it came from.

100 mm cubes suit most structural mixes with 20 mm aggregate and are easier to courier. 150 mm cubes are needed where the aggregate is larger, because BS EN 12390-1 relates specimen size to maximum aggregate size. Keep to one size across a job.

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 matching schedule: site, element poured, supplier and mix reference, casting date and time, testing ages and who receives the results. Include the slump or flow if measured. On a port or energy site with several contractors pouring, the element and contractor reference matters most.

No. Hixtra has one laboratory, in Milton Keynes, and every cube is cured and crushed there. The 0117 number rings through to the same team as our other numbers. We keep no staff or depot in Bristol, which is why cube testing here works by courier or by collection during a site visit.